全文获取类型
收费全文 | 19432篇 |
免费 | 207篇 |
国内免费 | 175篇 |
专业分类
安全科学 | 520篇 |
废物处理 | 753篇 |
环保管理 | 2549篇 |
综合类 | 3492篇 |
基础理论 | 5510篇 |
环境理论 | 10篇 |
污染及防治 | 4508篇 |
评价与监测 | 1210篇 |
社会与环境 | 1130篇 |
灾害及防治 | 132篇 |
出版年
2022年 | 129篇 |
2021年 | 139篇 |
2020年 | 115篇 |
2019年 | 144篇 |
2018年 | 322篇 |
2017年 | 363篇 |
2016年 | 531篇 |
2015年 | 337篇 |
2014年 | 395篇 |
2013年 | 1381篇 |
2012年 | 898篇 |
2011年 | 848篇 |
2010年 | 544篇 |
2009年 | 613篇 |
2008年 | 690篇 |
2007年 | 744篇 |
2006年 | 693篇 |
2005年 | 1040篇 |
2004年 | 1177篇 |
2003年 | 1045篇 |
2002年 | 486篇 |
2001年 | 585篇 |
2000年 | 449篇 |
1999年 | 278篇 |
1998年 | 206篇 |
1997年 | 202篇 |
1996年 | 211篇 |
1995年 | 226篇 |
1994年 | 214篇 |
1993年 | 214篇 |
1992年 | 221篇 |
1991年 | 212篇 |
1990年 | 208篇 |
1989年 | 180篇 |
1988年 | 153篇 |
1987年 | 132篇 |
1986年 | 157篇 |
1985年 | 158篇 |
1984年 | 160篇 |
1983年 | 163篇 |
1982年 | 157篇 |
1981年 | 163篇 |
1980年 | 151篇 |
1979年 | 147篇 |
1978年 | 108篇 |
1977年 | 121篇 |
1974年 | 111篇 |
1973年 | 92篇 |
1972年 | 109篇 |
1971年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
105.
The invertebrate neuromodulator octopamine is known to be involved in bees' associative learning, enhancing the responsiveness of a bee to a conditioned stimulus. In this study, we tested the effect of octopamine on the choice behavior of free-flying bumblebees using a two-phase experiment in an array of artificial flowers. During the first phase of the experiment, the bee was allowed to collect octopamine-laden sugar water from two types of equally rewarding flowers (yellow versus blue). In the second phase, one type of flower was set to be unrewarding. The behavior of the bee (proportion of visits to the unrewarding flowers) over the two phases was fitted to a sigmoid regression model. Our results show that octopamine had no significant effect on the bees' equilibrium choice or on the overall rate of the behavioral change in response to the change in reward. Rather, octopamine significantly affected the time interval between the change in reward status and the initiation of behavioral change in the bee. 相似文献
106.
107.
M. Blunck W. -D. Busse G. Meister E. Möller A. Mullen L. A. A. van Rooijen 《Die Naturwissenschaften》1989,76(3):96-98
Online searching in publically available patent files opens up interesting possibilities to provide a rapid response to critical questions. A computerized analysis of all patents of leading German pharmaceutical companies over the last decade in important indication areas is described. Supported by subsequent manual processing of individual patents it is shown that duplicate experiments on animals practically never occur. 相似文献
108.
The basic principles of dc-tandem and high-frequency linear accelerator are discussed by referring to the pioneering work of H. Kallmann and R. Wideröe. The 30 MV Supertandem in Daresbury, the Heidelberg combination of tandem and linac, and the universal linear accelerator Unilac of the GSI at Darmstadt serve as examples of modern heavy-ion accelerators. 相似文献
109.
E. Kuhn-Schnyder 《Die Naturwissenschaften》1979,66(12):587-592
Lorenz Oken, 1. Aug. 1779 Bohlsbach (Baden, Germany) — 11. Aug. 1851 Zurich (Switzerland). Philosopher and Zoologist. He studied at Freiburg i. Br. and Würzburg, was called from Göttingen to the university of Jena (1807–1819), München (1827–1832), Zurich (1833–1851). Oken came very early under the influence of Schelling and became the typical German Naturphilosoph. This did not prevent him from doing distinguished biological work. Oken was one of the best comparative anatomists of his days, his works on embryology are classics. He gave an interesting forecast of the modern cell doctrine. He founded a biological journal (Isis, 1816–1848) which for thirty years published articles of unquestioned value. He instituted the meetings of the “Gesellschaft Deutscher Naturforscher und Ärzte” (1821). By his “Naturgeschichte für alle Stände”, 13 vols. (1833–1845) he is one of the first to popularize natural science. 相似文献
110.
Extended screening tests on the cercaricidal activity of various plants from northeast Brazil have shown that the extracts of the leaves and fruits ofPiper marginatum,Protium heptaphyllum, andCapsicum annuum show a remarkable effect on the cercaria ofSchistosoma mansoni. In the case of the oils ofPiper marginatum andCapsicum annuum, 90–96% of the cercaria ofSchistosoma mansoni were killed within 15 min. According to the NMR spectra, the active principles of the extracts seem to be water-soluble unsaturated compounds from the oils or their hydrolysis products. Natural substances provide an attractive alternative for preventive actions against schistosomiasis, as the perturbation of the ecological equilibrium of natural waters can be avoided in this manner. 相似文献