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   1595篇
  免费   8篇
  国内免费   2篇
安全科学   10篇
废物处理   71篇
环保管理   85篇
综合类   525篇
基础理论   366篇
污染及防治   371篇
评价与监测   99篇
社会与环境   68篇
灾害及防治   10篇
  2017年   15篇
  2016年   21篇
  2014年   22篇
  2013年   70篇
  2012年   25篇
  2011年   48篇
  2010年   44篇
  2009年   48篇
  2008年   66篇
  2007年   51篇
  2006年   46篇
  2005年   44篇
  2004年   41篇
  2003年   39篇
  2002年   48篇
  2001年   59篇
  2000年   54篇
  1999年   34篇
  1998年   20篇
  1997年   30篇
  1996年   28篇
  1995年   30篇
  1994年   28篇
  1993年   26篇
  1992年   19篇
  1991年   36篇
  1990年   50篇
  1989年   23篇
  1988年   27篇
  1987年   20篇
  1985年   21篇
  1984年   21篇
  1983年   16篇
  1982年   30篇
  1979年   18篇
  1978年   13篇
  1977年   15篇
  1976年   13篇
  1974年   17篇
  1972年   17篇
  1971年   13篇
  1969年   11篇
  1968年   12篇
  1967年   23篇
  1966年   19篇
  1965年   13篇
  1964年   12篇
  1962年   13篇
  1958年   14篇
  1957年   12篇
排序方式: 共有1605条查询结果,搜索用时 0 毫秒
131.
132.
133.
134.
Assisted migration of forest trees has been widely proposed as a climate change adaptation strategy, but moving tree populations to match anticipated future climates may disrupt the geographically based, coevolved association suggested to exist between host trees and ectomycorrhizal fungal (EMF) communities. We explored this issue by examining the consistency of EMF communities among populations of 40 year-old Douglas-fir (Pseudotsuga menziesii var. menziesii) trees in a common-garden field trial using four provenances from contrasting coastal climates in southwestern British Columbia. Considerable variation in EMF community composition within test sites was found, ranging from 0.38 to 0.65 in the mean similarity index, and the divergence in EMF communities from local populations increased with site productivity. Clinal patterns in colonization success were detected for generalist and specialist EMF species on only the two productive test sites. Host population effects were limited to EMF species abundance rather than species loss, as richness per site averaged 15.0 among provenances and did not differ by transfer extent (up to 450 km), while Shannon's diversity index declined slightly. Large differences in colonization rates of specialist fungi, such as Tomentella stuposa and Clavulina cristata, raise the possibility that EMF communities maladapted to soil conditions contributed to the inferior growth of some host populations on productive sites. The results of the study suggest locally based specificity in host-fungal communities is likely a contributing factor in the outcome of provenance trials, and should be a consideration in analyzing seed-transfer effects and developing strategies for assisted migration.  相似文献   
135.
136.
MESIP is a fugacity model which can predict the fate of organic hydrophobic chemicals in aquatic ecosystems. In this paper a short introduction to the mathematical model is presented together with a more detailed listing of the required input data. Comparison of the calculated and measured fate of a fluorescent whitening compound in an artificial outdoor pond is shown  相似文献   
137.
SUMMARY

The rich plant diversity of the Indian Himalaya is utilized by the native communities in various forms as medicine, edible/food, fodder, fuel, timber, agricultural tools, etc. Among these, wild edible plants form an important source as a supplement/substitute food in times of scarcity for native communities. Because land holdings are small and subsistence agriculture prevails, the natives gather many wild plants for food. This paper presents an inventory of wild edible plants of Indian Himalaya used by local communities. Over 675 wild plant species, representing 384 genera and 149 families, are used as food/edible and their various parts are either consumed raw, roasted, boiled, fried, cooked or in the form of oil, spice, seasoning material, jams, pickles, etc. The species were analysed for diversity in different phytogeographical provinces, altitudinal distribution, endemism, origin and potentials. West Himalaya shows the highest diversity (50.96%) of edible plants and East Himalaya the maximum number of endemics (18 taxa) and wild relatives of economic plants (39 taxa). Mass scale propagation, dissemination of information packages to local inhabitants to ensure that wild edibles remain as a resource for income generation, and strategies for conservation and management are recommended.  相似文献   
138.
A risk assessment of chemical constituents in rivers that receive untreated wastewater should take into account the adverse effects of increased biological oxygen demand (BOD), ammonia and reduced dissolved oxygen (DO). This concept was tested via a field study in the Balatuin River, The Philippines, where the influence of physical and chemical factors, including the consumer product chemical linear alkylbenezene sulfonate (LAS), to aquatic communities (algae, invertebrates, fish) was determined. Periphytic algae were found to be insensitive to high BOD (>10 mg/l) and ammonia (>0.01 mg unionized NH(3)/l), concentrations from organically enriched untreated wastewater discharges. However, taxa richness and abundance of macroinvertebrates were influenced greatly by the discharges. Where BOD and ammonia concentrations were elevated, the dominant taxa were oligochaete worms and chironominds. Fish and crustaceans (freshwater crabs and prawns) were found only in sites with the least BOD concentrations (furthest upstream and downstream). The maximum concentration of LAS (0.122 mg/l) was less than that expected to affect 5% of taxa (0.245 mg/l), whereas exceedences of DO and ammonia criteria were observed in several sites. The lack of recovery observed was attributed to influences of low DO, high ammonia and poor colonization from upstream and downstream reaches due to organically-enriched discharges  相似文献   
139.
Hong SH  Yim UH  Shim WJ  Li DH  Oh JR 《Chemosphere》2006,64(9):1479-1488
To assess the organochlorine contamination in the Korean marine environment, a nationwide monitoring study was conducted. A total of 138 surface sediments, covering the whole Korean coast, were collected and analyzed. Organochlorine compounds (OCs) were widely distributed in the Korean coastal environment, with PCB and DDT contamination being particularly prevalent. The overall concentrations of PCBs, DDTs, HCHs, CHLs, and HCB in surface sediments were in the range of 0.088-199ngg(-1) (median value: 1.56ngg(-1)), 0.006-135ngg(-1) (0.68ngg(-1)), not detected (ND)-5.46ngg(-1) (0.32ngg(-1)), ND-3.26ngg(-1) (0.14ngg(-1)), and ND-2.59ngg(-1) (0.05ngg(-1)), respectively. The southeastern coast was found to be highly contaminated. Overall contamination status of Korean coastal sediments with regard to OCs is lower than that of USA. With the exception of highly industrialized sites, Korean coastal areas in general showed similar OC concentrations to those of other Asian countries. There was a significant correlation between distributions of most organochlorine contaminants with each other. OC contamination is closely related to shipping and industrial activities. Of the 7 sites categorized as highly polluted, 4 are in a harbor zone. Adverse effects to benthic communities are expected at the levels of OC contamination observed from harbor and industrial areas.  相似文献   
140.
Seeds of Cicer arietinum L. plants are edible and a valuable source of protein. Accumulation of toxic metals in the edible part of the plant, grown in fields close to fly-ash (FA) landfills, may pose a threat to human health. In the present study, the effects of FA and its amendments with different ameliorants viz., garden soil (GS), press mud (PM) and saw dust (SD), on total soluble protein contents, amino acid composition and metal accumulation in seeds were investigated in var. CSG-8962 and var. C-235 of C. arietinum. Plants accumulated adequate amounts of essential metals viz. Fe, Cu, Zn in seeds, while the toxic metals such as Cd and Cr were taken up in smaller quantities. The accumulation of Cr and Cd was less in var. C-235 than var. CSG-8962. Amendment of FA with PM enhanced the amount of soluble protein and amino acids in both varieties and was found to be superior among all tested ameliorants. Both quantitative and qualitative analysis of amino acids showed better response in var. C-235 as compared to var. CSG-8962. Thus var. C-235 seems to be suitable for cultivation in FA contaminated areas due to more accumulation of essential metals and less accumulation of toxic metals in seeds. Application of PM may further improve the growth of plants and nutritional quality of seeds.  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