全文获取类型
收费全文 | 29735篇 |
免费 | 334篇 |
国内免费 | 247篇 |
专业分类
安全科学 | 999篇 |
废物处理 | 1453篇 |
环保管理 | 3942篇 |
综合类 | 4469篇 |
基础理论 | 7748篇 |
环境理论 | 8篇 |
污染及防治 | 7349篇 |
评价与监测 | 2125篇 |
社会与环境 | 2043篇 |
灾害及防治 | 180篇 |
出版年
2023年 | 141篇 |
2022年 | 261篇 |
2021年 | 319篇 |
2020年 | 195篇 |
2019年 | 243篇 |
2018年 | 435篇 |
2017年 | 460篇 |
2016年 | 719篇 |
2015年 | 531篇 |
2014年 | 854篇 |
2013年 | 2463篇 |
2012年 | 1015篇 |
2011年 | 1349篇 |
2010年 | 1102篇 |
2009年 | 1144篇 |
2008年 | 1411篇 |
2007年 | 1329篇 |
2006年 | 1207篇 |
2005年 | 1079篇 |
2004年 | 1037篇 |
2003年 | 990篇 |
2002年 | 933篇 |
2001年 | 1091篇 |
2000年 | 768篇 |
1999年 | 482篇 |
1998年 | 363篇 |
1997年 | 383篇 |
1996年 | 397篇 |
1995年 | 465篇 |
1994年 | 394篇 |
1993年 | 343篇 |
1992年 | 376篇 |
1991年 | 355篇 |
1990年 | 326篇 |
1989年 | 322篇 |
1988年 | 295篇 |
1987年 | 241篇 |
1986年 | 247篇 |
1985年 | 247篇 |
1984年 | 267篇 |
1983年 | 254篇 |
1982年 | 268篇 |
1981年 | 221篇 |
1980年 | 165篇 |
1979年 | 181篇 |
1978年 | 162篇 |
1977年 | 133篇 |
1975年 | 137篇 |
1973年 | 167篇 |
1972年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
Changes in functional structure of soil bacterial communities due to fungicide and insecticide applications in canola 总被引:1,自引:0,他引:1
Newton Z. Lupwayi K. Neil Harker Lloyd M. Dosdall T. Kelly Turkington Robert E. Blackshaw John T. ODonovan Hctor A. Crcamo Jennifer K. Otani George W. Clayton 《Agriculture, ecosystems & environment》2009,130(3-4):109-114
The fungicide vinclozolin and insecticide λ-cyhalothrin are widely used to control canola (Brassica spp.) diseases and insect pests, respectively, in Canada. We investigated non-target effects of these pesticides, applied at recommended rates, on soil microbial biomass, functional bacterial diversity and functional community structure of soil bacteria (by evaluating patterns of C substrate utilization) in canola rhizosphere and bulk soil at three locations in Alberta from 2002 to 2004. Experimental treatments were (a) untreated control, (b) vinclozolin fungicide foliar application, (c) λ-cyhalothrin insecticide foliar application, and (d) vinclozolin and λ-cyhalothrin applications. No significant pesticide effects on soil microbial biomass or functional bacterial diversity were observed, but the functional structures of soil bacteria were altered. In 1 of 12 cases, the control treatment had a different soil bacterial community structure from the 3 pesticide treatments. The fungicide treatment had different bacterial community structures from the control or insecticide treatments in 3 of 12 cases, the insecticide treatment had different community structures from the control or fungicide treatments in 4 of 12 cases, and the combined fungicide and insecticide treatment had different community structures from the other treatments in 3 of 12 cases. Therefore, evaluating soil bacterial functional structures revealed pesticide effects that were not detected when bacterial diversity or microbial biomass were measured in canola rhizosphere or bulk soil. 相似文献
892.
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
893.
Norovirus Detection in Groundwater 总被引:2,自引:0,他引:2
894.
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
895.
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
896.
Kyriaki Remoundou Phoebe Koundouri Areti Kontogianni Paulo A.L.D. Nunes Michalis Skourtos 《Environmental Science & Policy》2009,12(7):1040-1051
This paper attempts to examine whether information from valuation studies can help the design of policies adequate to reverse and halt the generally poor state of marine and coastal ecosystems of the Mediterranean and the Black Sea. Economic implications of managing coastal and marine environments are thus discussed by assessing the results of different valuation studies implemented in the area. Lessons and policy recommendations from existing literature are inferred to guide marine resources management decisions. One of our main findings is that there are extremely few published studies within the Mediterranean and Black Sea region which highlights the potential for future research on coastal and marine ecosystems ability to sustain different goods and services as a result of climate change and anthropogenic drivers in the area. However, results reveal that there are substantial positive economic values attached to marketed and non-marketed services provided by marine and coastal ecosystems that justify their sustainable use and management. 相似文献
897.
898.
Thomas Merckx Ruth E. Feber Philip Riordan Martin C. Townsend Nigel A.D. Bourn Mark S. Parsons David W. Macdonald 《Agriculture, ecosystems & environment》2009,130(3-4):177-182
How best to optimize the biodiversity gain from agri-environment schemes (AES) has recently been identified as a key policy-relevant question. Here, the effects of two features of lowland agricultural landscapes on the abundance and diversity of larger moths are contrasted. Although both features bring about positive effects, hedgerow trees have a larger impact than 6 m wide grassy field margins. Whilst AES payments are given to create and maintain grass margins, no financial reward is currently offered for the retention of hedgerow trees. Furthermore, it was only in areas where the amount of land under AES was experimentally increased, by targeting farmers, that the presence of hedgerow trees resulted in a substantially higher abundance (+60%) and diversity (+38%) of moths. Thus, by using larger moths as bio-indicators of landscape-scale quality, it is demonstrated that improvements to the cost-effectiveness of AES could be achieved, firstly, by providing more appropriate financial rewards to farmers for different landscape features, and secondly, through landscape-scale targeting of farmers to encourage participation in AES. 相似文献
899.
Lily Amelia D.A. Wahab C.H. Che Haron N. Muhamad C.H. Azhari 《Journal of Cleaner Production》2009,17(17):1572-1579
As the production of local vehicles increases, the impact of end-of-life vehicles (ELVs) wastes to the environment will also increase. ELVs recovery including reuse, remanufacture, and recycle apparently become a strategy in solving this environmental problem. This study identifies the existing conditions of automotive reuse in Malaysia by conducting some interviews in selected local automotive and automotive component manufacturers. Results from the interviews indicated that reuse of automotive components in newly manufactured vehicles has never been practiced by the selected companies. However, there is interest among respondents in developing automotive components for after-market reuse. Some strategies were proposed in this study to initiate automotive components reuse in the local automotive manufacturers including the establishment of the end-of-life directive, enhance research and development on design for reuse and increase reusability and economic benefits of reuse. 相似文献
900.
Takashi A. Inoue Kiyoshi Asaoka Kazuaki Seta Daisuke Imaeda Mamiko Ozaki 《Die Naturwissenschaften》2009,96(3):355-363
The feeding behavior in nectar-feeding insects is triggered by a sugar-receptor response in contact chemosensilla. The contact
chemosensilla are distributed not only on tarsi and the outside of the proboscis but also on the inside of the food canal
in Lepidoptera. Although the chemosensilla inside the food canal are assumed to detect sweet taste during the passage of nectar
through the food canal, their electrophysiological function has received little attention. In the nectar-feeding Asian swallowtail
butterfly, Papilio xuthus (Lepidoptera: Papilionidae), we found 15- to 30-μm-long sensilla neatly lined up along the inside galea wall, which forms
the food canal in the proboscis. The receptor neurons of these sensilla responded to sucrose. We hypothesized that starch
and sucrose compete with each other for a taste receptor site on the sensilla. When we added starch and sucrose to the food-canal
sensilla, the electrophysiological responses of food-canal sensilla were inhibited in parallel with the food-sucking behavior
of the butterflies. These results suggest that the food-canal sensilla are involved in the behavioral control of nectar-sucking
in this butterfly species. 相似文献