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   87145篇
  免费   1249篇
  国内免费   1264篇
安全科学   3651篇
废物处理   3129篇
环保管理   13522篇
综合类   21129篇
基础理论   25877篇
环境理论   71篇
污染及防治   12961篇
评价与监测   5218篇
社会与环境   3589篇
灾害及防治   511篇
  2022年   795篇
  2021年   801篇
  2020年   658篇
  2019年   870篇
  2018年   1116篇
  2017年   1148篇
  2016年   2135篇
  2015年   1851篇
  2014年   2575篇
  2013年   9250篇
  2012年   2047篇
  2011年   2205篇
  2010年   3223篇
  2009年   3357篇
  2008年   1726篇
  2007年   1546篇
  2006年   1990篇
  2005年   2083篇
  2004年   2368篇
  2003年   2210篇
  2002年   1748篇
  2001年   2010篇
  2000年   1837篇
  1999年   1432篇
  1998年   1353篇
  1997年   1344篇
  1996年   1471篇
  1995年   1553篇
  1994年   1451篇
  1993年   1306篇
  1992年   1290篇
  1991年   1267篇
  1990年   1215篇
  1989年   1186篇
  1988年   1017篇
  1987年   972篇
  1986年   983篇
  1985年   1056篇
  1984年   1151篇
  1983年   1159篇
  1982年   1170篇
  1981年   1093篇
  1980年   937篇
  1979年   910篇
  1978年   817篇
  1977年   710篇
  1976年   638篇
  1975年   593篇
  1973年   619篇
  1972年   622篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
71.
72.
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   
73.
74.
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   
75.
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   
76.
77.
78.
79.
80.
Two synthetic superabsorbent crosslinked acrylic polymers were mineralized by the white-rot fungusPhanerochaete chrysosporium. The amount of polymer converted to CO2 increased as the amount of polymer added to the cultures increased. In the presence of sufficiently large amounts of the superabsorbents, such that all of the culture fluid was absorbed and a gelatinous matrix was formed, the fungus still grew and mineralization was observed. Neither the polymers, nor their degradation products were toxic to the fungus. While the rates of mineralization were low, all of the polymers incubated in the liquid fungal cultures were completely depolymerized to water soluble products within 15–18 days. The depolymerization of the polymers was observed only in nitrogen limited cultures of the fungus which secrete the lignin degradation system, however, the water soluble products of depolymerization were mineralized in both nutrient limited and sufficient cultures of the fungus. The rate of mineralization of the depolymerized metabolites was more than two times greater in nutrient sufficient cultures. Following longer incubation periods, most (> 80 %) of the radioactivity was recovered in the fungal mycelial mat suggesting that carbon of the polymer had been converted to fungal metabolites.  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