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   101403篇
  免费   1248篇
  国内免费   1349篇
安全科学   3974篇
废物处理   3865篇
环保管理   15223篇
综合类   21807篇
基础理论   27842篇
环境理论   75篇
污染及防治   19828篇
评价与监测   6122篇
社会与环境   4596篇
灾害及防治   668篇
  2022年   850篇
  2021年   871篇
  2020年   692篇
  2019年   921篇
  2018年   1379篇
  2017年   1364篇
  2016年   2340篇
  2015年   1890篇
  2014年   2645篇
  2013年   9330篇
  2012年   2741篇
  2011年   3387篇
  2010年   3541篇
  2009年   3690篇
  2008年   3053篇
  2007年   2974篇
  2006年   3050篇
  2005年   2859篇
  2004年   3111篇
  2003年   3060篇
  2002年   2544篇
  2001年   3065篇
  2000年   2412篇
  1999年   1679篇
  1998年   1412篇
  1997年   1415篇
  1996年   1549篇
  1995年   1642篇
  1994年   1527篇
  1993年   1388篇
  1992年   1393篇
  1991年   1348篇
  1990年   1316篇
  1989年   1262篇
  1988年   1087篇
  1987年   1038篇
  1986年   1007篇
  1985年   1088篇
  1984年   1180篇
  1983年   1188篇
  1982年   1177篇
  1981年   1110篇
  1980年   963篇
  1979年   954篇
  1978年   836篇
  1977年   729篇
  1976年   654篇
  1974年   638篇
  1973年   665篇
  1972年   673篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Anthropogenic habitat disturbance can often lead to rapid evolution of environmental tolerances in taxa that are able to withstand the stressor. What we do not understand, however, is how species respond when the stressor no longer exists, especially across landscapes and over a considerable length of time. Once anthropogenic disturbance is removed and if there is an ecological trade-off associated with local adaptation to such an historical stressor, then evolutionary theory would predict evolutionary reversals. On the Boreal Shield, tens of thousands of lakes acidified as a result of SO2 emissions, but many of these lakes are undergoing chemical recovery as a consequence of reduced emissions. We investigated the adaptive consequences of disturbance and recovery to zooplankton living in these lakes by asking (1) if contemporary evolution of acid tolerance had arisen among Leptodiaptomus minutus copepod populations in multiple circum-neutral lakes with and without historical acidification, (2) if L. minutus populations were adaptively responding to reversals in selection in historically acidified lakes that had recovered to pH 6.0 for at least 6-8 years, and (3) if there was a fitness trade-off for L. minutus individuals with high acid tolerance at circum-neutral pH. L. minutus populations had higher acid tolerances in circum-neutral lakes with a history of acidification than in local and distant lakes that were never acidified. However, copepods in circum-neutral acid-recovering lakes were less acid-tolerant than were copepods in lakes with longer recovery time. This adaptive reversal in acid tolerance of L. minutus populations following lake recovery was supported by the results of a laboratory experiment that indicated a fitness trade-off in copepods with high acid tolerances at circum-neutral pH. These responses appear to have a genetic basis and suggest that L. minutus is highly adaptive to changes in environmental conditions. Therefore, restoration managers should focus on removing environmental stressors, and adaptable species will be able to reverse evolutionary responses to environmental disturbance in the years following recovery.  相似文献   
82.
83.
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   
84.
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   
85.
86.
87.
88.
89.
90.
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