全文获取类型
收费全文 | 3354篇 |
免费 | 26篇 |
国内免费 | 46篇 |
专业分类
安全科学 | 79篇 |
废物处理 | 154篇 |
环保管理 | 417篇 |
综合类 | 456篇 |
基础理论 | 1235篇 |
环境理论 | 2篇 |
污染及防治 | 656篇 |
评价与监测 | 224篇 |
社会与环境 | 187篇 |
灾害及防治 | 16篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 18篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 127篇 |
2017年 | 136篇 |
2016年 | 205篇 |
2015年 | 75篇 |
2014年 | 34篇 |
2013年 | 62篇 |
2012年 | 449篇 |
2011年 | 253篇 |
2010年 | 48篇 |
2009年 | 51篇 |
2008年 | 68篇 |
2007年 | 88篇 |
2006年 | 89篇 |
2005年 | 416篇 |
2004年 | 535篇 |
2003年 | 413篇 |
2002年 | 57篇 |
2001年 | 53篇 |
2000年 | 28篇 |
1999年 | 38篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1961年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有3426条查询结果,搜索用时 109 毫秒
191.
Ground-living spiders were studied using modified pitfall traps during several years in four characteristic habitats in Giant Mountains (Krkono?e Mts.), the High Sudetes, Czech Republic: alpine tundra, subalpine mire, tall-herb stand at the bottom of a glacial corrie, and decaying mountain spruce forest. Ecological and zoogeographical aspects of spider communities were analysed. The spider communities of alpine tundra, subalpine mire, and glacial corrie exhibited long-term stability, whereas the community of decaying mountain forest changed during observations. Small linyphiid spiders, dominating in mature forest, were gradually replaced by larger Iycosid and gnaphosid species. Zoogeographic characterization of mountain habitats was made based on species exhibiting disjunctive area. In contrast to plants, for spiders of boreal origin alpine tundra is the most important habitat for survival, followed by screes, mires, spruce forests, and corries. 相似文献
192.
The primary objective of this study was to identify gaps in coastal and marine data available through the Gulf Geospatial Assessment of Marine Ecosystems (GAME) project for the west coast of Florida. A survey was designed and sent to more than 2,000 experts working with coastal and ocean issues in the Gulf of Mexico to elicit their opinions. The survey asked the experts to rank 12 data categories and score the relevance of four qualifiers (spatial resolution, temporal resolution, age of data, and level of detail) using a discrete choice approach. The statistical interpretation of experts?? responses allowed assigning a relative value to each available data set, based upon their qualifiers. The results were then displayed in a Geographic Information System to visually show how the total value for all data categories or for a specific data category varies spatially and to identify data gaps. It was found that the total data set value is generally higher within Tampa Bay and along the coast. Areas with low total value show a lack of data sets that have qualifiers falling within the ideal range, as per experts?? opinions. The gap maps created for this project are useful to identify priority areas where money should be invested for future data collection. 相似文献
193.
Combining field and laboratory work, this study investigated the reproductive cycle, aggregative behavior, spawning periodicity,
development and early growth of the sea star Henricia lisa living at bathyal depths off eastern Canada. Marked differences were found between individuals from ~1,300 and ~600 m deep.
The former had a male biased sex ratio and an aperiodic reproductive cycle, whereas the latter displayed an equal sex ratio
and a biannual breeding pattern. Furthermore, the maximum size was larger and female fecundity roughly five times higher in
shallower compared to deeper populations. In the tanks, aggregative behavior was recorded twice a year during the summer and
winter breeding periods. The onset of aggregations and spawning coincided with a temperature of 3–4°C. Males spawned first
and females typically responded inside 30–60 min. Between 12 and 20 eggs were retained to be brooded under the arched arms
of the female, whereas the remainder were broadcasted and developed without parental care. The fertilized eggs underwent a
first cleavage after 12 h, reached the brachiolaria stage in 1 month, became juveniles within 3–4 months and reached ~ 4 mm
in diameter after 14–17 months of growth. The embryos and juveniles developed at the same rate whether brooded or not, and
development of winter cohorts was typically slower due to lower prevailing temperatures. This study of H. lisa provides the first evidence of lecithotrophy in a seasonally breeding deep-sea echinoderm and of brooding in a deep-sea asteroid. 相似文献
194.
This study examines the composition and activity of the planktonic community during the polar night in the high Arctic Kongsfjord,
Svalbard. Our results are the first published evidence of bioluminescence among zooplankton during the Arctic polar night.
The observations were collected by a bathyphotometer detecting bioluminescence, integrated into an autonomous underwater vehicle,
to determine the concentration and intensity of bioluminescent flashes as a function of time of day and depth. To further
understand community dynamics and composition, plankton nets were used to collect organisms passing through the bathyphotometer
along with traditional vertical net tows. Additionally, using a moored bathyphotometer closed to the sampling site, the bioluminescence
potential itself was shown not to have a diurnal or circadian rhythm. Rather, our results provide evidence for a diel vertical
migration of bioluminescent zooplankton that does not correspond to any externally detectable changes in illumination. 相似文献
195.
Pascal D. Leroy Ahmed Sabri Fran?ois J. Verheggen Fr��d��ric Francis Philippe Thonart Eric Haubruge 《Chemoecology》2011,21(3):113-122
In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects,
plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect
species, inducing particular behaviours, such as the localisation of a source of food, the orientation to an adequate oviposition
site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown
to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing
on the semiochemically mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as
important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted
by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect
evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many
interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest
management, advances in this field are discussed in the context of biological control against insect pests. 相似文献
196.
Elaine S. Carvalho Rubén J. Sánchez Maria I. B. Tavares álano C. Lam?nica 《Journal of Polymers and the Environment》2010,18(4):661-667
The chemical modification of Acrylamidomethyl Cellulose Acetate Propionate (AMCAP) was carried out by radical addition of
acrylic acid. The structural modification was confirmed with the aid of FTIR, MS and NMR techniques. Thermal properties of
hydrophilic cellulose derivative (AMCAP–H2O2) such as glass transition (Tg 153 °C) and thermal stability (372.7 °C) were determined by DSC and TGA techniques, respectively. These thermal properties
confirmed the introduction of carboxylic groups into AMCAP structure, which causes an impact in their properties. The AMCAP–H2O2 shows minor contact angle compared to AMCAP, giving a more hydrophilic characteristic, due to acrylic acid addition into
the side chains of AMCAP polymer. 相似文献
197.
Kelly M. Cobourn Hannah J. Burrack Rachael E. Goodhue Jeffrey C. Williams Frank G. Zalom 《Journal of Environmental Economics and Management》2011,62(2):278-289
A modeler must often rely on highly simplified representations of complex physical systems when analyzing associated economic issues. Herein, we consider a management problem in which a bioeconomic system exhibits simultaneity in processes governing productivity and damage. In this case, it may benefit the producer to sacrifice productivity to reduce the costs associated with increased damage. We specify empirically a structural damage relationship that explains the biological process by which an invasive species damages a host and estimate the structural model and its reduced form with an exceptional dataset on infestation of olives by the olive fruit fly. We contrast the results of these models with the approach typically taken in the economic literature, which expresses damage as a function of pest density. The population-based approach introduces significantly greater bias into the individual grower's choice of damage-control inputs than estimates based on the structural model. 相似文献
198.
Kelly A. Stiver Stephen H. Wolff Suzanne H. Alonzo 《Behavioral ecology and sociobiology》2012,66(6):855-864
While extensive empirical and theoretical work has focused on the evolution of costly cooperation (particularly in group-living species), less attention has been paid to more low-risk or immediately beneficial forms of cooperation. In some non-group-living darters, alloparental care (or allocare) by subordinates has been noted to result from by-product benefits as small territorial (subordinate) males adopt and provide care to the abandoned eggs of large territorial (dominant) males. In the tessellated darter (Etheostoma olmstedi), allocare also results from sneak fertilization. However, information on the rate of allocare by tessellated darters is contradictory: prior behavioral work suggested that it is very common, while a genetic examination showed males to primarily care for their own young. We found behavioral and genetic evidence of very high levels of allocare at our study location. The relative size of the assigned fathers of young to the alloparental male is consistent with the idea that initial allocare primarily results from sneak fertilization (“cuckoldry-based allocare”), but later allocare results from subordinate males caring at previously abandoned nests (“adoption-based allocare”). Larger males appeared to breed more frequently at different nests, but did not father more individual offspring than smaller males. Finally, low relatedness between abandoning and alloparenting males suggests that kin selection does not contribute to alloparental care. We discuss how variation in nest availability may explain the inconsistent findings of the rate of alloparental care in the tessellated darter, and how increased research in this and similar systems can expand our understanding of the evolution of cooperation. 相似文献
199.
Negative effects of noise on individuals, the inevitable result of urbanization, have become a significant urban problem in our day. Introduction of an approach to the noise problem on an urban-planning scale lightens the burden of measures required to be taken against noise at the stages of regional and developmental planning. Stadiums, which should be also evaluated from the point of noise problem when planning decisions are made on the urban planning scale, may cause very serious problems differing depending on the region they are located in. In this article, various dimensions of the noise problem caused by stadiums have been exemplified by making an assessment on Ali Sami Yen football stadium located in Mecidiyeköy district which is among important residential and commercial centres of ?stanbul or Turkey. When the simulation results obtained for ordinary days and match days are evaluated, it has been found out that the people living in the area are exposed to noise levels substantially exceeding the acceptable values. Results of the survey conducted in the area have clearly revealed the existence of noise problem, too. 相似文献
200.
Vitas M Smith KE Plavec J Kesselmeier J Pajic T Ferlan A Zigon RD Kelly SL Komel R 《Chemosphere》1999,38(4):853-863
We investigated the hypothesis that the endogenous role of the commercially important inducible steroid hydroxylase cytochrome P450s of fungi was in defense against plant toxophores/secondary metabolites. Two plant defense compounds, the aglycones tomatidine and solanidine, the steroidal glycoalkaloid alpha-tomatine and the triterpene saponin beta-escin were tested as inducers of 11beta/14alpha-steroid hydroxylase in the filamentous fungus Cochliobolus lunatus. The extracts of saponins from the roots of Primula veris and green oat leaves were also tested as inducers of 11beta/14alpha-hydroxylation activity in progesterone biotransformation with the same fungus. Induction of steroid hydroxylase and inhibition of activity in some cases support our hypothesis that their endogenous function is in biochemical defence against secondary metabolites. 4-Pregnene-3,11,20-trione was added as a substrate for biotransformation with C. lunatus. We isolated from culture broth 14alpha-hydroxy-4-pregnene-3,11,20-trione, and the hitherto unreported compounds, 7alpha,14alpha-dihydroxy-4-pregnene-3,11,20-trione and 7alpha-hydroxy-pregna-4,8(14)-diene-3,11,20-trione. 相似文献