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   90295篇
  免费   1239篇
  国内免费   1106篇
安全科学   3843篇
废物处理   3212篇
环保管理   14162篇
综合类   21230篇
基础理论   26481篇
环境理论   78篇
污染及防治   14060篇
评价与监测   5408篇
社会与环境   3601篇
灾害及防治   565篇
  2022年   804篇
  2021年   812篇
  2020年   667篇
  2019年   885篇
  2018年   1168篇
  2017年   1180篇
  2016年   2175篇
  2015年   1866篇
  2014年   2630篇
  2013年   9304篇
  2012年   2234篇
  2011年   2479篇
  2010年   3311篇
  2009年   3442篇
  2008年   1997篇
  2007年   1799篇
  2006年   2238篇
  2005年   2240篇
  2004年   2539篇
  2003年   2341篇
  2002年   1909篇
  2001年   2118篇
  2000年   1926篇
  1999年   1466篇
  1998年   1378篇
  1997年   1344篇
  1996年   1480篇
  1995年   1574篇
  1994年   1475篇
  1993年   1329篇
  1992年   1305篇
  1991年   1287篇
  1990年   1236篇
  1989年   1201篇
  1988年   1021篇
  1987年   977篇
  1986年   998篇
  1985年   1066篇
  1984年   1158篇
  1983年   1175篇
  1982年   1181篇
  1981年   1109篇
  1980年   944篇
  1979年   919篇
  1978年   824篇
  1977年   715篇
  1976年   640篇
  1975年   612篇
  1973年   628篇
  1972年   628篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
While the world is going into different tourism expectations, the tourism understanding in Turkey is defined as tourism in the sea-sand-sun triangle. However, it is possible to contribute to the income and local development of the indigenous people by developing nature-based tourism. Besides, with the sustainable use and preservation of the natural-cultural assets, the damage of the traditional tourism industry on the natural and cultural environment could be reduced. In this study, it is aimed to bring up the nature-based tourism concept in Çanakkale by evaluating the nature-based tourism industry in the general of Turkey and assessing the natural-cultural resources that Çanakkale comprehends. The most important areas that have a nature-based tourism potential in Çanakkale and the tourism activities that are most suitable for these areas have been determined.  相似文献   
75.
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   
76.
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