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   43078篇
  免费   450篇
  国内免费   522篇
安全科学   1206篇
废物处理   1636篇
环保管理   5885篇
综合类   7116篇
基础理论   11968篇
环境理论   27篇
污染及防治   10833篇
评价与监测   2658篇
社会与环境   2424篇
灾害及防治   297篇
  2022年   358篇
  2021年   328篇
  2020年   268篇
  2019年   356篇
  2018年   617篇
  2017年   594篇
  2016年   879篇
  2015年   731篇
  2014年   1029篇
  2013年   3305篇
  2012年   1282篇
  2011年   1858篇
  2010年   1507篇
  2009年   1605篇
  2008年   1852篇
  2007年   1934篇
  2006年   1677篇
  2005年   1472篇
  2004年   1394篇
  2003年   1369篇
  2002年   1332篇
  2001年   1743篇
  2000年   1226篇
  1999年   760篇
  1998年   572篇
  1997年   590篇
  1996年   625篇
  1995年   681篇
  1994年   605篇
  1993年   556篇
  1992年   558篇
  1991年   546篇
  1990年   526篇
  1989年   541篇
  1988年   469篇
  1987年   428篇
  1986年   390篇
  1985年   412篇
  1984年   407篇
  1983年   441篇
  1982年   455篇
  1981年   393篇
  1980年   348篇
  1979年   383篇
  1978年   310篇
  1977年   275篇
  1976年   260篇
  1975年   266篇
  1973年   249篇
  1972年   271篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
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   
32.
33.
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   
34.
35.
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   
36.
37.
38.
39.
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   
40.
We examined the impact of seven species of mobile mushroom corals (Fungiidae) on the community structure of sheltered reef slopes in terms of their patterns of migration, habitat use and competition with other benthic organisms. On fringing reefs at Eilat, Red Sea, polyps detached at 1 to 6 cm length, and grew to 11–55 cm length. Attached mushroom corals were oriented vertically in reef cavities. Detached corals migrated downward on the reef slope and onto rubble or soft substratum at the reef base, at 29 to 71 cmyr–1. Mobility decreased with corallum size and extent of undersurface ornamentation. In aquaria, small corals righted themselves and migrated up to 6 cm d–1 by nocturnally inflating and pushing their tissues against the substratum. Autonomous coral behavior and storm-generated water motion appeared to account for most fungiid mobility at Eilat. Mushroom corals did not damage each other upon contact, even in multi-species aggregations, but unilaterally damaged non-fungiid scleractinian corals. Their dominance during contact interactions retards overgrowth by larger attached scleractinians, and mobility allows them to colonize soft substrata not accessible to most other reef corals.  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