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   492篇
  免费   10篇
  国内免费   5篇
安全科学   28篇
废物处理   12篇
环保管理   101篇
综合类   61篇
基础理论   146篇
污染及防治   110篇
评价与监测   21篇
社会与环境   16篇
灾害及防治   12篇
  2023年   4篇
  2022年   6篇
  2021年   6篇
  2020年   12篇
  2019年   8篇
  2018年   18篇
  2017年   7篇
  2016年   12篇
  2015年   14篇
  2014年   17篇
  2013年   40篇
  2012年   14篇
  2011年   18篇
  2010年   19篇
  2009年   14篇
  2008年   14篇
  2007年   18篇
  2006年   18篇
  2005年   18篇
  2004年   10篇
  2003年   14篇
  2002年   15篇
  2001年   27篇
  2000年   12篇
  1999年   14篇
  1998年   6篇
  1997年   7篇
  1996年   11篇
  1995年   9篇
  1994年   4篇
  1993年   6篇
  1992年   5篇
  1991年   7篇
  1990年   7篇
  1989年   4篇
  1988年   3篇
  1987年   5篇
  1986年   6篇
  1985年   4篇
  1984年   5篇
  1983年   5篇
  1982年   6篇
  1981年   4篇
  1980年   3篇
  1979年   7篇
  1977年   5篇
  1975年   4篇
  1974年   2篇
  1973年   4篇
  1967年   2篇
排序方式: 共有507条查询结果,搜索用时 15 毫秒
1.
2.
Mitigation and Adaptation Strategies for Global Change - In Mexico an estimated 4.5 × 106ha are available for farm forestry, while up to 6.1 × 106 ha could be saved from deforestation by...  相似文献   
3.
Desulfobacter sp. (Strain 3ac10), an acetate-utilizing sulphatereducing bacteria, was added to sterile marine pore water spiked with 14C-acetate, and changes in both the natural acetate pool and the added 14C-acetate were measured over time. Initially, both the added 14C-acetate and the chemically measured acetate were rapidly mineralized, but then the rate of removal decreased and a significant amount (approximately 20%) of both 14C-acetate and chemically measured acetate remained unmetabolised. In a replicate experiment, approximately 50% of the acetate was not metabolised. Kinetic analysis of the data indicated that there were two pools of acetate in the original pore water, a biologically available pool (which is rapidly metabolised) and a recalcitrant pool (which is only very slowly metabolised). Addition of 14C-acetate after the biologically available acetate had been removed resulted in rapid removal of the added acetate but no change in the recalcitrant acetate pool. The implications of this data to radiolabelled techniques of measuring in situ acetate turnover are discussed.  相似文献   
4.
A ciliate red tide at Barrow,Alaska   总被引:1,自引:0,他引:1  
In September 1968 the first occurrence of extensive red water in the Arctic Ocean in the vicinity of Point Barrow, Alaska, was recorded. The organism causing this water discoloration was a fairly large (100 to 150 ) ciliated protozoan, with chlorophyll-containing endosymbionts. This ciliate, which is not identical to the commonly reported Mesodinium or Cyclotrichium species, is described in this paper, but cannot be identified with any organism described in the literature. Concentrations of dissolved inorganic nutrients and trace metals were determined on water samples obtained from the red water and also in the clear water adjacent to it. These data are discussed relative to the hydrographic conditions in the Chuckchi Sea around Point Barrow. A direct species' analysis by microscopic methods indicated that the plankton were quite similar in all the water samples except for the aforementioned red ciliate, which accounted for over 90% of the total cellular organic carbon in the samples from the red water. Chemical analyses indicated that the red tide ciliate contained approximately 51% protein, 33% lipid, 8% carbohydrate, 0.2% chlorophyll a, and 1.2% DNA.  相似文献   
5.
Fucus distichus L. was collected near Vancouver, Canada, in late fall and early winter, 1981. The effects of the forms of nitrogen (nitrate, ammonium or urea) and periodic exposure to air on growth, rhizoid development and nitrogen uptake in germlings was investigated. Gamete release, fertilization, germination and germling growth had no requirement for a specific form of nitrogen. Periodic exposure to air increased secondary rhizoid development twofold. Nitrate and ammonium uptake rates of the germlings were higher than for the mature thalli (20 to 40 times for nitrate and 8 times for ammonium), while the halfsaturation constant (K s) values for nitrate were similar (1 to 5 M). The germlings showed saturable uptake kinetics but the mature thalli did not. When germlings were exposed to air it caused a 70% decrease in nitrate uptake, but not change in ammonium uptake. Ammonium uptake in the mature thalli was proportional to the ambient ammonium concentration. Nitrate uptake in the mature thalli appeared to follow saturation kinetics at low nitrate concentrations, but showed a non-saturable component at concentrations greater than 10 M. Presence of ammonium inhibited nitrate uptake by the mature plants but not by the germlings.  相似文献   
6.
Taylor AJ 《Disasters》1990,14(4):291-300
Two three-dimensional conceptual models are presented that should help those concerned with disasters and disaster victims to integrate the numerous studies on the topic. The first, concerning disasters, involves matters ecological, technological and social scientific. It covers the elements earth, air, fire, water/liquid, and people. It includes the time dimensions of preparedness, response, recovery and mitigation. The second introduces a six-fold classification of victims, together with dimensions to cover the methods and kinds of delivery of different interventions that might be made available to help them. The suggestion is that, were the appropriately noted victim model placed within the larger disaster model according to the types of disaster study being examined, there might be useful academic, political, and professional implications.  相似文献   
7.
Taylor AJ 《Disasters》1983,7(1):37-40
This paper defines the various levels within government, the voluntary agencies and the community which might benefit from training and makes suggestions as to where the emphasis should be placed. It points out that training programmes should be designed to meet the expressed needs of a particular group of trainees as well as be related to the current or potential disaster situation.  相似文献   
8.
Material within the terrestrial environment is rarely homogeneously distributed, either spatially or temporally. One consequence of heterogeneity is that uncertainty is usually generated in measurements that are taken with the aim of characterising the environment. For example, a measurement of analyte concentration within soil taken from one sampling location on contaminated land can vary substantially when compared against another sample taken at effectively the same nominal location. The measurement uncertainty arising from the heterogeneity can substantially limit the reliability of the interpretations made upon environmental investigations. The sampling uncertainty usually outweighs the analytical uncertainty from the laboratory, often by a factor of 20 or more. One approach to reducing the uncertainty is to design a more suitable sampling strategy. This might be achieved by predicting the degree of heterogeneity prior to the investigation, but this is often difficult to achieve accurately. Another approach, which was investigated here, is to actually characterise the heterogeneity prior to the main investigation using rapid and inexpensive technology, such as in situ measurement techniques. In situ portable X-ray fluorescence (PXRF) and X-ray microprobe (XMP) techniques were employed to test the feasibility of this approach. Two contrasting contaminated land sites were chosen to characterise the two-dimensional spatial heterogeneity of heavy metal contamination in topsoil at a range of scales (50 m to 0.001 m). The spatial heterogeneity of contaminants, expressed as relative standard deviations, was found to differ between the two sites by a factor of two, largely due to the mode of deposition of pollution. The study also indicated that the heterogeneity did not change systematically with the scale of measurement between sampling locations at either site.  相似文献   
9.
10.
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