首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   107778篇
  免费   2131篇
  国内免费   7382篇
安全科学   5054篇
废物处理   4381篇
环保管理   15406篇
综合类   31192篇
基础理论   28895篇
环境理论   73篇
污染及防治   20557篇
评价与监测   6189篇
社会与环境   4193篇
灾害及防治   1351篇
  2023年   723篇
  2022年   1607篇
  2021年   1581篇
  2020年   1248篇
  2019年   1376篇
  2018年   1741篇
  2017年   1956篇
  2016年   3043篇
  2015年   2928篇
  2014年   3916篇
  2013年   10919篇
  2012年   3684篇
  2011年   3949篇
  2010年   4489篇
  2009年   4575篇
  2008年   3348篇
  2007年   2956篇
  2006年   3367篇
  2005年   2967篇
  2004年   3086篇
  2003年   2966篇
  2002年   2503篇
  2001年   2680篇
  2000年   2502篇
  1999年   1936篇
  1998年   1714篇
  1997年   1734篇
  1996年   1796篇
  1995年   1843篇
  1994年   1665篇
  1993年   1511篇
  1992年   1475篇
  1991年   1382篇
  1990年   1331篇
  1989年   1254篇
  1988年   1093篇
  1987年   1011篇
  1986年   1005篇
  1985年   1080篇
  1984年   1174篇
  1983年   1179篇
  1982年   1188篇
  1981年   1115篇
  1980年   944篇
  1979年   933篇
  1978年   827篇
  1977年   717篇
  1976年   652篇
  1973年   658篇
  1972年   655篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
Abstract:  Introduction of artificial light into wildlife habitat represents a rapidly expanding form of human encroachment, particularly in coastal systems. Light pollution alters the behavior of sea turtles during nesting; therefore, long-wavelength lights—low-pressure sodium vapor and bug lights—that minimize impacts on turtles are required for beach lighting in Florida (U.S.A.). We investigated the effects of these two kinds of lights on the foraging behavior of Santa Rosa beach mice (  Peromyscus polionotus leucocephalus ). We compared patch use and giving-up densities of mice for experimental food patches established along a gradient of artificial light in the field. Mice exploited fewer food patches near both types of artificial light than in areas with little light and harvested fewer seeds within patches near bug lights. Our results show that artificial light affects the behavior of terrestrial species in coastal areas and that light pollution deserves greater consideration in conservation planning.  相似文献   
9.
The quantitative relationship between the median effective concentration (EC50) of organic chemicals to Daphnia magna and the number of molecular fragments was investigated based on experimental EC50 values for 217 chemicals derived from the literature. A fragment constant model was developed based on a multivariate linear regression between the number of fragments and the logarithmically transformed reciprocal values of EC50. Functional correction factors were introduced into the model. The model was verified using an independent set of randomly selected data. The mean residual of the final model was 0.4 log-units. The robustness of the model was discussed based on the results of three jackknife tests.  相似文献   
10.
The genetic polymorphism of natural populations of Lepilemur mustelinus ruficaudatus was studied by protein electrophoresis. We sampled blood from 72 individuals from four populations separated by geographic or anthropogenic barriers from southwestern Madagascar. Six out of 22 enzyme loci showed genetic variation with a degree of polymorphism of 0.273. The expected and observed degree of genetic heterozygosity over all loci is similar to that of other primates (He = 0.058, Ho = 0.036). The F-statistics revealed that the four subpopulations were similar with respect to gene structure (FST = 0.065, p = 0.016), but the genotypic structures within subpopulations were inconsistent with random mating. For the total of the four subpopulations the proportion of heterozygous individuals was significantly smaller than expected under random mating (FIS = 0.373, FIT = 0.414, p < 0.01). These results correspond closely to what is expected considering the low migration ability of individuals of L. m ruficaudatus leading to small and rather isolated inbred populations.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号