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   92819篇
  免费   1230篇
  国内免费   1117篇
安全科学   3781篇
废物处理   3344篇
环保管理   14233篇
综合类   21375篇
基础理论   26537篇
环境理论   72篇
污染及防治   15892篇
评价与监测   5551篇
社会与环境   3848篇
灾害及防治   533篇
  2022年   814篇
  2021年   810篇
  2020年   649篇
  2019年   876篇
  2018年   1147篇
  2017年   1195篇
  2016年   2196篇
  2015年   1846篇
  2014年   2597篇
  2013年   9270篇
  2012年   2253篇
  2011年   2566篇
  2010年   3290篇
  2009年   3455篇
  2008年   2173篇
  2007年   2066篇
  2006年   2424篇
  2005年   2347篇
  2004年   2671篇
  2003年   2535篇
  2002年   2079篇
  2001年   2467篇
  2000年   2074篇
  1999年   1547篇
  1998年   1382篇
  1997年   1372篇
  1996年   1494篇
  1995年   1598篇
  1994年   1493篇
  1993年   1348篇
  1992年   1330篇
  1991年   1300篇
  1990年   1263篇
  1989年   1216篇
  1988年   1065篇
  1987年   999篇
  1986年   995篇
  1985年   1068篇
  1984年   1166篇
  1983年   1177篇
  1982年   1177篇
  1981年   1099篇
  1980年   951篇
  1979年   936篇
  1978年   830篇
  1977年   726篇
  1976年   657篇
  1974年   632篇
  1973年   656篇
  1972年   653篇
排序方式: 共有10000条查询结果,搜索用时 77 毫秒
71.
72.
A statistical analysis of interannual variation in a set of vegetative and generative characters over 13 years has been performed to characterize the growth and seed production dynamics of the Siberian stone pine (Pinus sibirica Du Tour) in the southeast of the forest zone in western Siberia. The results have shown that the range of fluctuations in most of vegetative characters is ordinary and their distribution is close to normal. The range of fluctuations in many generative characters is enormous (from 0 to +∞), and the distribution of their values is usually skewed, with low values being recorded several times more frequently than high values. Most variable are the proportion of abortive cones and other characters that are determined mainly in the spring of the pollination year. These characters account for a very high level of variation in the total seed production.  相似文献   
73.
74.
Phylogenetic relationships and genetic population structures were analyzed for tideland gastropods in the genus Cerithidea around Japan on the basis of partial sequence of the mitochondrial COI gene. Large genetic divergence was shown between individuals of Cerithidea cingulata in the southern Ryukyus and those in the central Ryukyus and the Japanese Islands. Haplotypes of C. cingulata from the Japanese Islands were paraphyletic with the exclusion of a monophyletic group from the central Ryukyus. Genetic differentiation of C. cingulata was also detected between Amami-Oshima Island and Okinawajima Island. No genetic divergence was found between Cerithidea rhizophorarum in the Japanese Islands and its subspecies C. rhizophorarum morchii in the Ryukyu Islands. The lack of genetic divergence of Cerithidea largillierti between continental China and Japan suggests relatively recent migration between the Japanese Islands and the Asian continent. For all three Cerithidea species distributed in both the Japanese Islands and the Ryukyu Islands, the Tokara Gap and the Kerama Gap were shown to have acted as barriers to the dispersal.  相似文献   
75.
76.
Collections made in the course of long-term field studies on ecology of the northern mole vole Ellobius talpinus Pall. in the Ural Region and neighboring areas (more than 2000 individuals from 24 points of the species range) were used to analyze geographic variation in its coat color (color morphs). On the basis of long-term observations (1985–1999) on marked animals from a polymorphic population (Kurtamyshskii raion, Kurgan oblast), the life spans of males and females and the dependence of life span on population density and structure were estimated in animals of different color morphs. Each color morph of E. talpinus was shown to have specific features of the seasonal dynamics of age structure and migrations.  相似文献   
77.
78.
79.
80.
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