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   17248篇
  免费   142篇
  国内免费   113篇
安全科学   406篇
废物处理   652篇
环保管理   1904篇
综合类   5324篇
基础理论   3569篇
环境理论   2篇
污染及防治   4092篇
评价与监测   877篇
社会与环境   616篇
灾害及防治   61篇
  2018年   200篇
  2017年   188篇
  2016年   285篇
  2015年   216篇
  2014年   317篇
  2013年   1155篇
  2012年   369篇
  2011年   517篇
  2010年   493篇
  2009年   554篇
  2008年   573篇
  2007年   596篇
  2006年   526篇
  2005年   465篇
  2004年   501篇
  2003年   457篇
  2002年   436篇
  2001年   616篇
  2000年   412篇
  1999年   282篇
  1998年   203篇
  1997年   195篇
  1996年   193篇
  1995年   230篇
  1994年   242篇
  1993年   206篇
  1992年   223篇
  1991年   231篇
  1990年   253篇
  1989年   229篇
  1988年   181篇
  1987年   180篇
  1986年   180篇
  1985年   180篇
  1984年   199篇
  1983年   187篇
  1982年   195篇
  1981年   207篇
  1980年   169篇
  1979年   180篇
  1978年   147篇
  1977年   139篇
  1974年   147篇
  1973年   146篇
  1968年   156篇
  1967年   184篇
  1966年   154篇
  1965年   148篇
  1964年   151篇
  1963年   139篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
451.
The mental health consequences of exposure to traumatic events and the risk factors for psychological morbidity among expatriate and Kosovar Albanian humanitarian aid workers have not been well studied. In June 2000, we used standardised screening tools to survey 285 (69.5%) of 410 expatriate aid workers and 325 (75.8%) of 429 Kosovar Albanian aid workers from 22 humanitarian organizations that were implementing health programmes in Kosovo. The mean number of trauma events experienced by expatriates was 2.8 (standard deviation: 2.7) and by Kosovar staff 3.2 (standard deviation: 2.8). Although only 1.1% of expatriate and 6.2% of Kosovar aid workers reported symptoms consistent with the diagnosis for post-traumatic stress disorder, 17.2% and 16.9%, respectively, reported symptoms satisfying the definition of depression. Regression analysis demonstrated that the number of trauma events experienced was significantly associated with depression for the two sets of workers. Organisational support services may be an important mediating factor and should be targeted at both groups.  相似文献   
452.
Mussels are worldwide recognized as pollution bioindicators and used in Mussel Watch programs, because they accumulate pollutants in their tissues at elevated levels in relation to pollutant biological availability in the marine environment. The present study deals with the use of Mytilus galloprovincialis as a local bioindicator of heavy metal and (137)Cs contamination in an estuarine ecosystem (Thermaikos gulf, Greece in Eastern Mediterranean). M. galloprovincialis samples were collected monthly from two aquaculture farms during the period April to October 2000. Analyses for the heavy metals Cu, Cr, Ni, Zn, Fe, Mn and (137)Cs showed that the concentrations measured were low and similar to those from other non-polluted Mediterranean areas. In terms of the two sampling stations, there were no statistically significant differences between them. On the contrary, the seasonal evolution of either heavy metals or (137)Cs levels presented high variation. The levels were found to increase during the cold period of the year, especially for Cu, Zn, Mn and Cr which are essential for life. Stable metals were positively inter-related and moreover, metals more involved in biochemical activities seem to present more correlations than others with less significant role in the metabolism of the organisms.  相似文献   
453.
Classification and distribution of mangrove vegetation are vital information for the proper development of a mangrove management plan. In this study, classification for the mangroves of the district of Kemaman were done using both 1 : 5000 aerial photographs and Landsat TM imageries. The coverage by aerial photographs is limited to the coastal and estuarine areas only. Thus, for areas further upstream of the aerial photo coverage, Landsat TM imageries were used. Analysis of aerial photographs and remote sensing images revealed that the mangroves of Kemaman could be classified into 14 different classes of vegetation. All the 14 classes were identified from areas covered by the aerial photographs. For areas covered by the Landsat images only 7 classes of vegetation were identified. The accuracy for aerial photograph and Landsat images are 91.2% and 87.8%, respectively. It can be concluded that although both techniques are useful in determining the mangrove vegetation classes, the large 1 : 5000 aerial photographs are more accurate and provided more detailed information comparatively.  相似文献   
454.
Man‐made disasters such as acts of terrorism may affect a society's resiliency and sensitivity to prolonged physical and psychological stress. The Israeli Tel Aviv stock market TA‐100 Index was used as an indicator of reactivity to suicide terror bombings. After accounting for factors such as world market changes and attack severity and intensity, the analysis reveals that although Israel's financial base remained sensitive to each act of terror across the entire period of the Second Intifada (2000–06), sustained psychological resilience was indicated with no apparent overall market shift. In other words, we saw a ‘normalisation of terror’ following an extended period of continued suicide bombings. The results suggest that investors responded to less transitory global market forces, indicating sustained resilience and long‐term market confidence. Future studies directly measuring investor expectations and reactions to man‐made disasters, such as terrorism, are warranted.  相似文献   
455.
The 7Be wet deposition has been intensively investigated in a semiarid region at San Luis Province, Argentina. From November 2006 to May 2008, the 7Be content in rainwater was determined in 58 individual rain events, randomly comprising more than 50% of all individual precipitations at the sampling period. 7Be activity concentration in rainwater ranged from 0.7 ± 0.3 Bq l−1 to 3.2 ± 0.7 Bq l−1, with a mean value of 1.7 Bq l−1 (sd = 0.53 Bq l−1). No relationship was found between 7Be content in rainwater and (a) rainfall amount, (b) precipitation intensity and (c) elapsed time between events. 7Be ground deposition was found to be well correlated with rainfall amount (R = 0.92). For the precipitation events considered, the 7Be depositional fluxes ranged from 1.1 to 120 Bq m−2, with a mean value of 32.7 Bq m−2 (sd = 29.9 Bq m−2). The annual depositional flux was estimated at 1140 ± 120 Bq m−2 y−1. Assuming the same monthly deposition pattern and that the 7Be content in soil decreases only through radioactive decay, the seasonal variation of 7Be areal activity density in soil was estimated. Results of this investigation may contribute to a valuable characterization of 7Be input in the explored semiarid ecosystem and its potential use as tracer of environmental processes.  相似文献   
456.
457.
458.
For the investigation of climatic history for the last 65 million years, several holes were drilled in 1990 on the Ontong Java Plateau by the drilling vessel Joides Resolution, under the auspices of the international Ocean Drilling Program. The Ontong Java Plateau is the largest basalt plateau on earth, and was formed in the Middle Cretaceous. From the core material, seismic reflectors from the overlying sediments can be associated with specific, climate-related oceanic events. For the cyclic sediments of the last 2 million years, high-resolution isotope curves were generated which depict the two dominant Milankovitch cycles with periods of 100 000 and 41000 years.  相似文献   
459.
460.
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