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   41802篇
  免费   537篇
  国内免费   570篇
安全科学   1342篇
废物处理   1582篇
环保管理   5919篇
综合类   6888篇
基础理论   11647篇
环境理论   27篇
污染及防治   10782篇
评价与监测   2424篇
社会与环境   1997篇
灾害及防治   301篇
  2022年   318篇
  2021年   319篇
  2020年   312篇
  2019年   323篇
  2018年   596篇
  2017年   592篇
  2016年   868篇
  2015年   750篇
  2014年   998篇
  2013年   3142篇
  2012年   1301篇
  2011年   1858篇
  2010年   1507篇
  2009年   1592篇
  2008年   1821篇
  2007年   1944篇
  2006年   1690篇
  2005年   1416篇
  2004年   1423篇
  2003年   1307篇
  2002年   1298篇
  2001年   1635篇
  2000年   1183篇
  1999年   755篇
  1998年   578篇
  1997年   588篇
  1996年   594篇
  1995年   658篇
  1994年   580篇
  1993年   532篇
  1992年   532篇
  1991年   503篇
  1990年   505篇
  1989年   522篇
  1988年   455篇
  1987年   391篇
  1986年   382篇
  1985年   408篇
  1984年   428篇
  1983年   426篇
  1982年   448篇
  1981年   386篇
  1980年   340篇
  1979年   374篇
  1978年   294篇
  1977年   265篇
  1976年   251篇
  1975年   253篇
  1974年   242篇
  1972年   266篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
891.
892.
The general integument of reptiles is traditionally defined as being dry, but we report here the discovery of unicellular mucoid glands (UCMG) in the dorsal skin of lizards of the genus Phelsuma (Gekkonidae). To this end, the skin of these lizards and of some others for comparison was studied by scanning electron microscopy and transmission electron microscopy. These photographs showed that the development and function of the UCMGs are related to the skin's sloughing cycle. The UCMGs differentiate at scattered locations from Oberh?utchen cells of the inner (new) epidermal generation, above the differentiating beta-keratin layer. While the inner generation matures, the UCMG increases in size; unlike the surrounding Oberh?utchen cells, it does not develop the spinules that characterize gecko skin. When, upon sloughing, the inner generation becomes the new outer generation, and the Oberh?utchen forms the skin surface, the UCMGs, several per scale, dot the surface as mucus-inflated "blebs" projecting from the surrounding spinulate Oberh?utchen, each nesting in a shallow pit of the underlying beta-keratin. On the surface, the UCMGs rupture and the mucus appears to dissipate in cords, flowing over the tips of the spinules, and incorporating minute foreign bodies. It is concluded that, due to the low wettability of the spinulate surface (derived from the spacing of the spinules), the cords brush off easily, with the mucus functioning as a cleaning agent.  相似文献   
893.
894.
This paper explores the implications of work schedule flexibility for family life. Based on data from the 1977 Quality of Employment Survey, it demonstrates that flexibility of work schedules moderates the effects of nonstandard work schedules on family life. That is, nonstandard work schedules tend to have a less negative association with the quality of family life when accompanied by a high level of schedule flexibility. The paper further demonstrates that this tendency of flexibility to act as a buffer against the negative effects of nonstandard work schedules on family life is more pronounced among working women than working men.  相似文献   
895.
896.
897.
This study attempts to assess the sources of occupational stress on air traffic controllers. It is based on data collected from a majority of air traffic controllers at a large U.K. airport. There are two unique methodological features described in this article. First, the use of the repertory grid technique as a method of generating work stressor variables, and second, the use of the multiple logistic equation as a coronary heart disease risk index.  相似文献   
898.
899.
The purpose of this study was to estimate the total medical care costs of individuals injured in motor vehicle crashes and in crashes where alcohol was involved. Crashes were studied that involved 2,728 vehicle occupants and 191 pedestrians with injuries as reported in 1979 by the National Accident Sampling System, a probability sample of all motor vehicle crashes occurring in the united States. Medical care costs were assigned by using Abbreviated Injury Scale codes in accordance with other published research. Determination of alcohol involvement was based on crash characteristics. Results indicate that 20.2 % of medical care costs for motor vehicle crash injuries may be due to crashes where alcohol was involved. It was estimated that alcohol-related motor vehicle crashes cost between $434 million and $483 million in medical care alone in the United States in 1979.  相似文献   
900.
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