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   96363篇
  免费   1226篇
  国内免费   1146篇
安全科学   3852篇
废物处理   3660篇
环保管理   14466篇
综合类   21599篇
基础理论   26905篇
环境理论   74篇
污染及防治   17587篇
评价与监测   5832篇
社会与环境   4203篇
灾害及防治   557篇
  2022年   854篇
  2021年   835篇
  2020年   660篇
  2019年   889篇
  2018年   1220篇
  2017年   1276篇
  2016年   2280篇
  2015年   1865篇
  2014年   2632篇
  2013年   9313篇
  2012年   2392篇
  2011年   2800篇
  2010年   3389篇
  2009年   3561篇
  2008年   2456篇
  2007年   2402篇
  2006年   2663篇
  2005年   2566篇
  2004年   2875篇
  2003年   2757篇
  2002年   2278篇
  2001年   2727篇
  2000年   2237篇
  1999年   1641篇
  1998年   1406篇
  1997年   1391篇
  1996年   1517篇
  1995年   1608篇
  1994年   1525篇
  1993年   1353篇
  1992年   1359篇
  1991年   1327篇
  1990年   1284篇
  1989年   1217篇
  1988年   1076篇
  1987年   1006篇
  1986年   1000篇
  1985年   1070篇
  1984年   1174篇
  1983年   1173篇
  1982年   1179篇
  1981年   1103篇
  1980年   954篇
  1979年   943篇
  1978年   831篇
  1977年   729篇
  1976年   653篇
  1974年   644篇
  1973年   657篇
  1972年   664篇
排序方式: 共有10000条查询结果,搜索用时 390 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.
Codigestion of five wastes and municipal wastewater sludge was evaluated using full-scale testing. Synergistic, antagonistic, and neutral outcomes were observed depending on codigestate identity and concentration, highlighting the value of careful blending. Yeast waste resulted in notable synergism, increasing biogas production by over 50%, whereas aircraft deicing waste resulted in antagonism at high loadings and neutral outcomes at lower loadings. Restaurant waste codigestion resulted in neutral outcomes. The synergisim with yeast codigestates may have resulted from trace nutrients (i.e., iron, nickel, and cobalt) in the wastes that increased microbiological activity. Antagonist outcomes with deicing waste may have been the result of organic overload or inhibitory deicer constituents. Codigestion of wastes at the feed rates investigated was estimated to produce 0.50 ML/d of methane having an energy equivalent of 17 500 MJ/d. This was estimated to reduce net carbon dioxide emissions by 560 tonnes/y.  相似文献   
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