全文获取类型
收费全文 | 33399篇 |
免费 | 343篇 |
国内免费 | 220篇 |
专业分类
安全科学 | 813篇 |
废物处理 | 1400篇 |
环保管理 | 4261篇 |
综合类 | 6426篇 |
基础理论 | 8710篇 |
环境理论 | 15篇 |
污染及防治 | 8345篇 |
评价与监测 | 2104篇 |
社会与环境 | 1712篇 |
灾害及防治 | 176篇 |
出版年
2022年 | 214篇 |
2021年 | 238篇 |
2018年 | 397篇 |
2017年 | 405篇 |
2016年 | 649篇 |
2015年 | 506篇 |
2014年 | 764篇 |
2013年 | 2470篇 |
2012年 | 899篇 |
2011年 | 1303篇 |
2010年 | 1029篇 |
2009年 | 1125篇 |
2008年 | 1327篇 |
2007年 | 1410篇 |
2006年 | 1253篇 |
2005年 | 1072篇 |
2004年 | 1067篇 |
2003年 | 1034篇 |
2002年 | 1000篇 |
2001年 | 1244篇 |
2000年 | 881篇 |
1999年 | 555篇 |
1998年 | 406篇 |
1997年 | 443篇 |
1996年 | 452篇 |
1995年 | 520篇 |
1994年 | 484篇 |
1993年 | 444篇 |
1992年 | 424篇 |
1991年 | 442篇 |
1990年 | 440篇 |
1989年 | 413篇 |
1988年 | 380篇 |
1987年 | 351篇 |
1986年 | 330篇 |
1985年 | 320篇 |
1984年 | 397篇 |
1983年 | 349篇 |
1982年 | 403篇 |
1981年 | 335篇 |
1980年 | 298篇 |
1979年 | 300篇 |
1978年 | 281篇 |
1977年 | 239篇 |
1976年 | 217篇 |
1975年 | 226篇 |
1974年 | 244篇 |
1973年 | 230篇 |
1972年 | 224篇 |
1971年 | 220篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
J. S. Rice R. H. Moss P. J. Runci K. L. Anderson E. L. Malone 《Mitigation and Adaptation Strategies for Global Change》2012,17(7):805-819
A new modeling effort exploring the opportunities, constraints, and interactions between mitigation and adaptation at regional scale is utilizing stakeholder engagement in an innovative approach to guide model development and demonstration, including uncertainty characterization, to effectively inform regional decision making. This project, the integrated Regional Earth System Model (iRESM), employs structured stakeholder interactions and literature reviews to identify the most relevant adaptation and mitigation alternatives and decision criteria for each regional application of the framework. The information is used to identify important model capabilities and to provide a focus for numerical experiments. This paper presents the stakeholder research results from the first iRESM pilot region. The pilot region includes the Great Lakes Basin in the Midwest portion of the United States as well as other contiguous states. This geographic area (14 states in total) permits cohesive modeling of hydrologic systems while also providing strong gradients in climate, demography, land cover/land use, and energy supply and demand. The results from the stakeholder research indicate that, for this region, iRESM should prioritize addressing adaptation alternatives in the water resources, urban infrastructure, and agriculture sectors, including water conservation, expanded water quality monitoring, altered reservoir releases, lowered water intakes, urban infrastructure upgrades, increased electric power reserves in urban areas, and land use management/crop selection changes. For mitigation in this region, the stakeholder research implies that iRESM should focus on policies affecting the penetration of renewable energy technologies, and the costs and effectiveness of energy efficiency, bioenergy production, wind energy, and carbon capture and sequestration. 相似文献
992.
Maria Rönnqvist Thedi Ziegler Carl-Henrik von Bonsdorff Leena Maunula 《Food and environmental virology》2012,4(1):26-33
Recent events have shown that humans may become infected with some pathogenic avian influenza A viruses (AIV). Since soil
and water, including lakes, rivers, and seashores, may be contaminated by AIV excreted by birds, effective methods are needed
for monitoring water for emerging viruses. Combining water filtration with molecular methods such as PCR is a fast and effective
way for detecting viruses. The objective of this study was to apply a convenient method for the detection of AIV in natural
water samples. Distilled water and lake, river, and seawater were artificially contaminated with AIV (H5N3) and passed through
a filter system. AIV was detected from filter membrane by real-time RT-PCR. The performance of Zetapor, SMWP, and Sartobind
D5F membranes in recovering influenza viruses was first evaluated using contaminated distilled water. SWMP, which gave the
highest virus recoveries, was then compared with a pre-filter combined GF/F filter membrane in a trial using natural water
samples. In this study, the cellulose membrane SMWP was found to be practical for recovery of AIVs in water. Viral yields
varied between 62.1 and 65.9% in distilled water and between 1 and 16.7% in natural water samples. The borosilicate glass
membrane GF/F combined with pre-filter was also feasible in filtering natural water samples with viral yields from 1.98 to
7.33%. The methods described can be used for monitoring fresh and seawater samples for the presence of AIV and to determine
the source of AIV transmission in an outbreak situation. 相似文献
993.
994.
Many endotherms save energy during food and water shortage or unpredictable environment using controlled reductions in body
temperature and metabolism called torpor. In this study, we measured energy metabolism and water turnover in free-ranging
grey mouse lemurs Microcebus murinus (approximately 60 g) using doubly labelled water during the austral winter in the rain forest of southeastern Madagascar.
We then compared patterns of thermal biology between grey mouse lemurs from the rain forest and a population from the dry
forest. M. murinus from the rain forest, without a distinct dry season, entered daily torpor independent of ambient temperature (T
a). There were no differences in torpor occurrence, duration and depth between M. murinus from the rain and dry forest. Mouse lemurs using daily torpor reduced their energy expenditure by 11% in the rain forest
and by 10.5% in the dry forest, respectively. There was no significant difference in the mean water flux rates of mouse lemurs
remaining normothermic between populations of both sites. In contrast, mean water flux rate of individuals from the dry forest
that used torpor was significantly lower than those from the rain forest. This study represents the first account of energy
expenditure, water flux and skin temperature (T
sk) in free-ranging M. murinus from the rain forest. Our comparative findings suggest that water turnover and therefore water requirement during the austral
winter months plays a more restricting role on grey mouse lemurs from the dry forest than on those from the rain forest. 相似文献
995.
European scale application of atmospheric reactive nitrogen measurements in a low-cost approach to infer dry deposition fluxes 总被引:1,自引:0,他引:1
Y.S. Tang I. Simmons N. van Dijk C. Di Marco E. Nemitz U. Dmmgen K. Gilke V. Djuricic S. Vidic Z. Gliha D. Borovecki M. Mitosinkova J.E. Hanssen T.H. Uggerud M.J. Sanz P. Sanz J.V. Chorda C.R. Flechard Y. Fauvel M. Ferm C. Perrino M.A. Sutton 《Agriculture, ecosystems & environment》2009,133(3-4):183
A European scale network was established in 2006 as part of the NitroEurope Integrated Project to infer reactive nitrogen (Nr) dry deposition fluxes, based on low-cost sampling of gaseous and aerosol species and inferential modelling. The network provides monthly measurements of NH3, NH4+, HNO3 and NO3−, as well as SO2, SO42−, HCl, Cl− and base cations at 58 sites. Measurements are made with an established low-cost denuder methodology (DELTA) as a basis to: (1) examine temporal trends and spatial patterns across Europe, (2) improve and calibrate inferential modelling techniques to estimate exchange of Nr species, (3) provide best estimates of atmospheric dry N deposition, and (4) permit an analysis of net GHG exchange in relation to atmospheric and agricultural N inputs at the European scale. Responsibility for measurements is shared among seven European laboratories. An inter-comparison of the DELTA implementation by 6 laboratories at 4 test sites (Montelibretti, Italy; Braunschweig, Germany; Paterna, Spain and Auchencorth, UK) from July to October 2006 provided training for the laboratories and showed that good agreement was achieved in different climatic conditions (87% of laboratory site-means within 20% of the inter-laboratory median). Results obtained from the first year of measurements show substantial spatial variability in atmospheric Nr concentrations, illustrating the major local (NH3) and regional (HNO3, NO3−, and NH4+) differences in Nr concentrations. These results provide the basis to develop future estimates of site-based Nr dry deposition fluxes across Europe, and highlight the role of NH3, largely of agricultural origin, which was the largest single constituent and will dominate dry Nr fluxes at most sites. 相似文献
996.
C.R. Rodríguez Pleguezuelo V.H. Durn Zuazo J.L. Muriel Fernndez F.J. Martín Peinado D. Franco Tarifa 《Agriculture, ecosystems & environment》2009,134(1-2):79-88
On the coast of Granada (SE, Spain), an economically important area for subtropical fruit cultivation, the crops are grown on orchard terraces. Also, high amounts of fertilizers, often excessive, are used in this type of intensive agriculture. However, each year significant fractions of nutrients taken up by the trees return to the soil by fallen leaves. Using a litter-bag technique, we assessed the decomposition rates and N-release in various types of litter. Our main purpose was to compare two different agroecosystem scenarios: (1) an unaltered slope consisting mainly of a mixture of herbaceous plants (Papaver rhoeas, Convolvulus sp., Malva sylvestris, Reseda phyteuma, Anacyclus sp., Sinapis arvensis, Medicago sp.) among spontaneous perennial woody shrubs (Genista umbellata, Olea europaea, Lavandula officinalis, Phlomis purpurea, Retama sphaerocarpa), and (2) an altered slope cultivated with subtropical trees on terraces: loquat (Eriobotrya japonica), mango (Mangifera indica), avocado (Persea americana), and cherimoya (Annona cherimola), with groundcover plantings of aromatic, medicinal, and melliferous plants (AMMPs) on the taluses of the terraces, which are usually used for erosion control: Lavandula dentata, Thymus mastichina, Satureja obovata, Rosmarinus officinalis, Anthyllis cytisoides. In the leaves from the subtropical crops, we found the highest decomposition rates in cherimoya and the lowest in mango (1.30 and 0.64 years−1, respectively). Leaves from mango and loquat registered initial peaks of N immobilization and later N-release, which was highest in cherimoya and avocado leaves (71.2 and 56.8% of the initial remaining N). In the spontaneous woody shrubs, O. europaea and G. umbellata were the slowest in decomposing (1.18 and 1.01 years−1, respectively) contrary to L. officinalis, which decomposed fastest (2.22 years−1). Only L. officinalis and P. purpurea registered a net N-release at the end of the study. The AMMPs showed different decomposition patterns: L. dentata registered the highest decomposition rates and Rosmarinus the lowest (1.9 and 1.1 years−1, respectively). T. mastichina, L. dentata, and S. obovata had the highest N-release, whereas R. officinalis and A. cytisoides showed N immobilization (183 and 122% of the initial N). Knowledge of the dynamics of nutrient release and litter decomposition will be useful for predicting nutrient availability and nutrient cycles in these types of agroecosystems where subtropical orchards are grown on terraces. 相似文献
997.
Norovirus Detection in Groundwater 总被引:2,自引:0,他引:2
998.
Guangxue Wu Zhenhu Hu Mark G. Healy Xinmin Zhan 《Frontiers of Environmental Science & Engineering in China》2009,3(3):300-306
Since the solubilization of meat and bone meal (MBM) is a prerequisite in many MBM disposal approaches, enhancement of the
solubilization by means of thermochemical pretreatment was investigated in this study at two temperatures (55°C and 131°C)
and six sodium hydroxide (NaOH) concentrations (0, 1.25, 2.5, 5, 10 and 20 g/L). The MBM volatile solid (VS) reduction ratio
was up to 66% and 70% at 55°C and 131°C, respectively. At the same temperature, the VS reduction ratio increased with the
increase in the dosage of NaOH. The study on the methane (CH4) production potential of pretreated MBM shows that the addition of NaOH at 55°C did not cause the inhibition of the succeeding
CH4 production process. However, CH4 production was inhibited by the addition of NaOH at 131°C. The CH4 production potential was in the range of 389 to 503 mL CH4/g VS MBM and 464 to 555 mL CH4/g VS MBM at 55°C and 131°C, respectively. 相似文献
999.
Here, we review Charles Darwin’s relation to beetles and developments in coleopteran systematics in the last two centuries.
Darwin was an enthusiastic beetle collector. He used beetles to illustrate different evolutionary phenomena in his major works,
and astonishingly, an entire sub-chapter is dedicated to beetles in “The Descent of Man”. During his voyage on the Beagle,
Darwin was impressed by the high diversity of beetles in the tropics, and he remarked that, to his surprise, the majority
of species were small and inconspicuous. However, despite his obvious interest in the group, he did not get involved in beetle
taxonomy, and his theoretical work had little immediate impact on beetle classification. The development of taxonomy and classification
in the late nineteenth and earlier twentieth century was mainly characterised by the exploration of new character systems
(e.g. larval features and wing venation). In the mid-twentieth century, Hennig’s new methodology to group lineages by derived
characters revolutionised systematics of Coleoptera and other organisms. As envisioned by Darwin and Ernst Haeckel, the new
Hennigian approach enabled systematists to establish classifications truly reflecting evolution. Roy A. Crowson and Howard
E. Hinton, who both made tremendous contributions to coleopterology, had an ambivalent attitude towards the Hennigian ideas.
The Mickoleit school combined detailed anatomical work with a classical Hennigian character evaluation, with stepwise tree
building, comparatively few characters and a priori polarity assessment without explicit use of the outgroup comparison method.
The rise of cladistic methods in the 1970s had a strong impact on beetle systematics. Cladistic computer programs facilitated
parsimony analyses of large data matrices, mostly morphological characters not requiring detailed anatomical investigations.
Molecular studies on beetle phylogeny started in the 1990s with modest taxon sampling and limited DNA data. This has changed
dramatically. With very large data sets and high throughput sampling, phylogenetic questions can be addressed without prior
knowledge of morphological characters. Nevertheless, molecular studies have not lead to the great breakthrough in beetle systematics—yet.
Especially the phylogeny of the extremely species rich suborder Polyphaga remains incompletely resolved. Coordinated efforts
of molecular workers and of morphologists using innovative techniques may lead to more profound insights in the near future.
The final aim is to develop a well-founded phylogeny, which truly reflects the evolution of this immensely species rich group
of organisms. 相似文献
1000.
Evans Obura Charles A. O. Midega Daniel Masiga John A. Pickett Mohamed Hassan Shinsaku Koji Zeyaur R. Khan 《Die Naturwissenschaften》2009,96(10):1169-1176
Napier grass (Pennisetum purpureum) is the most important fodder crop in smallholder dairy production systems in East Africa, characterized by small zero-grazing units. It is also an important trap crop used in the management of cereal stemborers in maize in the region. However, production of Napier grass in the region is severely constrained by Napier stunt disease. The etiology of the disease is known to be a phytoplasma, 16SrXI strain. However, the putative insect vector was yet unknown. We sampled and identified five leafhopper and three planthopper species associated with Napier grass and used them as candidates in pathogen transmission experiments. Polymerase chain reaction (PCR), based on the highly conserved 16S gene, primed by P1/P6-R16F2n/R16R2 nested primer sets was used to diagnose phytoplasma on test plants and insects, before and after transmission experiments. Healthy plants were exposed for 60 days to insects that had fed on diseased plants and acquired phytoplasma. The plants were then incubated for another 30 days. Nested PCR analyses showed that 58.3% of plants exposed to Recilia banda Kramer (Hemiptera: Cicadellidae) were positive for phytoplasma and developed characteristic stunt disease symptoms while 60% of R. banda insect samples were similarly phytoplasma positive. We compared the nucleotide sequences of the phytoplasma isolated from R. banda, Napier grass on which these insects were fed, and Napier grass infected by R. banda, and found them to be virtually identical. The results confirm that R. banda transmits Napier stunt phytoplasma in western Kenya, and may be the key vector of Napier stunt disease in this region. 相似文献