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   100274篇
  免费   1550篇
  国内免费   1650篇
测绘学   3184篇
大气科学   7335篇
地球物理   20088篇
地质学   37888篇
海洋学   7763篇
天文学   18768篇
综合类   2357篇
自然地理   6091篇
  2022年   430篇
  2021年   770篇
  2020年   864篇
  2019年   915篇
  2018年   6376篇
  2017年   5573篇
  2016年   4786篇
  2015年   1688篇
  2014年   2407篇
  2013年   4182篇
  2012年   3353篇
  2011年   5797篇
  2010年   4666篇
  2009年   5894篇
  2008年   5214篇
  2007年   5395篇
  2006年   3202篇
  2005年   2727篇
  2004年   2865篇
  2003年   2698篇
  2002年   2389篇
  2001年   1979篇
  2000年   1916篇
  1999年   1520篇
  1998年   1611篇
  1997年   1472篇
  1996年   1195篇
  1995年   1247篇
  1994年   1081篇
  1993年   971篇
  1992年   953篇
  1991年   854篇
  1990年   945篇
  1989年   799篇
  1988年   727篇
  1987年   912篇
  1986年   752篇
  1985年   999篇
  1984年   1084篇
  1983年   992篇
  1982年   946篇
  1981年   837篇
  1980年   773篇
  1979年   718篇
  1978年   712篇
  1977年   642篇
  1976年   621篇
  1975年   582篇
  1974年   569篇
  1973年   545篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
222.
223.
224.
This paper goes some way towards redressing the lack of geographical literature on charity through exploring the geography of the British domestic charitable sector. The size and geography of the third sector is outlined, followed by an analysis of how almshouses can be understood as inherently geographical and deeply embedded in local social networks of inclusion as well as exclusion.  相似文献   
225.
226.
227.
— Brunei Darussalam experienced a severe haze episode between the beginning of February and the end of April 1998 due mainly to local peat and forest fires in Brunei and in neighbouring Sabah and Sarawak. The extensive research studies of the haze carried out in Brunei are outlined together with selected results. Particulate matter (PM10) was the only significant criteria pollutant and it exceeded WHO guidelines and accepted air quality standards on most days during the haze episode. Gaseous criteria pollutants (CO, SO2, NO2, O3) were generally well below WHO guidelines and at these concentrations they are expected to have no significant health or environmental effects. Measurements of volatile organic compounds (VOCs) revealed the presence of benzene, toluene, ethylbenzene, and xylenes (BTEX), aldehydes, phenol, and polynuclear aromatic hydrocarbons (PAHs). Personal exposure monitoring of PM10 revealed significant differences in exposure patterns between different individuals depending on the location, time and activity. Data on outpatient visits showed an increase for some illnesses (e.g., acute respiratory infection) during the months of haze. No significant impacts of haze on rainwater acidity or deposition were noted. Emission factors for some volatile compounds were determined in combustion experiments in which peat was burned at temperatures typical of smouldering.  相似文献   
228.
Relationships of mineralized microbiota with the content of polycyclic aromatic hydrocarbons in hydrothermal systems are considered. It has been established that the mineralized microbiota can serve as an indicator of hydrothermal hydrocarbon flows in present-day and ancient deposits.  相似文献   
229.
SENSITIVITY OF MALARIA, SCHISTOSOMIASIS AND DENGUE TO GLOBAL WARMING   总被引:5,自引:0,他引:5  
Global assessment of the potential impacts of anthropogenically-induced climate change on vector-borne diseases suggests an increase in extent of the geographical areas susceptible to transmission of malarial Plasmodium parasites, dengue Flavivirus and Schistosoma worms. The transmission potential of the three associated vector-borne diseases studied is highly sensitive to climate changes on the periphery of the currently endemic areas and at higher altitudes within such areas. Our findings vis-à-vis the present endemic areas indicate that the increase in the epidemic potential of malaria and dengue transmission may be estimated at 12–27% and 31–47%, respectively, while in contrast, schistosomiasis transmission potential may be expected to exhibit a 11–17% decrease.  相似文献   
230.
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