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   142篇
  免费   2篇
安全科学   5篇
废物处理   3篇
环保管理   8篇
综合类   73篇
基础理论   22篇
污染及防治   24篇
评价与监测   6篇
社会与环境   3篇
  2018年   2篇
  2017年   2篇
  2016年   2篇
  2014年   2篇
  2013年   8篇
  2012年   2篇
  2011年   4篇
  2010年   4篇
  2009年   6篇
  2008年   4篇
  2007年   3篇
  2006年   3篇
  2005年   4篇
  2004年   2篇
  2003年   3篇
  2002年   10篇
  2001年   2篇
  1994年   2篇
  1992年   2篇
  1974年   2篇
  1969年   3篇
  1968年   2篇
  1967年   4篇
  1966年   4篇
  1964年   3篇
  1963年   3篇
  1962年   6篇
  1961年   1篇
  1960年   3篇
  1959年   1篇
  1958年   2篇
  1957年   1篇
  1956年   1篇
  1954年   1篇
  1953年   1篇
  1952年   2篇
  1946年   1篇
  1943年   2篇
  1942年   1篇
  1939年   2篇
  1937年   1篇
  1934年   1篇
  1933年   1篇
  1928年   1篇
  1926年   1篇
  1925年   3篇
  1924年   1篇
  1923年   1篇
  1916年   1篇
  1914年   1篇
排序方式: 共有144条查询结果,搜索用时 171 毫秒
121.
Hand cranks are used in a variety of industries to actuate valves and in other gear-operated applications. In order to evaluate these types of operations and their compatibility with operator strength capabilities, a rotational dynamometer was used to measure torque production capability of operators using a hand crank at different heights and angles (with respect to the coronal plane). The tests were conducted for both clockwise and counterclockwise rotations using the dominant arm of each test participant. A total of 18 tests were completed by each of five male right-handed test participants. A 0° declination angle, counterclockwise operation, and both 40.65 cm and 60.96 cm heights were found to be associated with the greatest torque production capabilities.  相似文献   
122.
123.
With the increasing public concern over the environment, corporate management is now faced with the problem of first, organizing its efforts to be responsive to the public and legislation, and second, obtaining maximum value for its expenditures. This paper discusses how a firm can approach the problem of deciding when to use environmental consultants and when to perform tasks using an in-house staff organization.  相似文献   
124.
125.
Koh IO  Rotard W  Thiemann WH 《Chemosphere》2002,47(2):219-227
Chlorinated paraffins (CPs) pose a major risk in the environment, due to their wide application, to their persistence, to their carcinogenic potential, and in view of the fact, that they cannot be easily identified. Various commercial cutting fluids and sealing materials were analysed for CPs with carbon skeleton reaction gas chromatography (GC) and flame ionization detection. CPs are simultaneously dechlorinated and hydrogenated to the corresponding alkanes with Pd catalyst material in the GC injector. With this method, the carbon chain length of commercial technical CPs was determined. In six of sixteen sealing materials we found five short and one medium chain length polychlorinated paraffins in percentages of 9-16% (w/w). In five cutting fluids we found predominantly medium to long chain length chloroparaffins with percentages of 2.5-31% (w/w), only one fluid contained short chain CPs.  相似文献   
126.
Stand level O(3) fluxes were calculated using water balance calculations for 21 Common beech (Fagus sylvatica L.) stands and O(3) data from 20 monitoring stations in Southern Germany. For this intention, the daily loss of water by evapotranspiration per stand area was set against the daily O(3) uptake. During the last 30 years, O(3) uptake ranges between 0 and 187 mmol ha(-1) d(-1) per stand area. Cumulative O(3) uptake (CUO(3)), ranging between 0.1 and 0.7 mmol m(-2) yr(-1) per stand area, shows increasing trends since 1971 with considerably greater values at high altitudes. Effects in radial growth were used to derive an initial approximate critical threshold value for O(3) impacts on the vitality and growth of mature beech stands in Southern Germany. It is concluded that this concept of O(3) flux estimation in combination with dendroecological analyses offers both a site specific and regional applicable approach to derive new critical levels for O(3).  相似文献   
127.
128.
The paper explores the relations of (1) regionalized climate change impulses; (2) their impacts on regional industry sectors; and (3) a regional econometric impact analysis. It develops a methodology by which the impulses of a regional climate change scenario can be transformed into ‘primary’ impacts on the capital stock and value added of climate-sensitive regional industries. These industries are vulnerable to ‘creeping’, i.e. continuous, climate change impulses, and they tend to react through ‘defensive’ investment. In addition, a singular flooding event is simulated for a specific local area and its different capital stocks. The stock damages and value-added losses of both the continuous industrial impacts and the singular flooding are inserted into a regional econometric model. This is sectorally disaggregated in stock, value-added and investment functions. It is also calibrated in the very-long run (through to the year 2040), according to different scenarios. The regional economic ‘secondary’ effects on the regional GNP are calculated. In addition to the calculation of regional economic primary and secondary impacts, the methodological issue of generating more transparency of the causal chains by use of damage functions, reaction functions, and comparative defensive strategies are discussed.  相似文献   
129.
DNA-dependent RNA polymerases of archaebacteria are distinct from those of eubacteria both in structure and in function. They show similarities to those of the eukaryotic cytoplasm. Extremely thermophilic anaerobic sulfur-respiring archaebacteria isolated from solfataric waters represent four different families, the Thermoproteaceae, the “stiff filaments”, the Desulfurococcaceae and the Thermococcaceae, of a novel order, Thermoproteales. Together with the Sulfolobales, they form the second branch of the urkingdom of the archaebacteria besides that of the methanogens and extreme halophiles. Thermoplasma appears isolated.  相似文献   
130.
The potential risk of ground-water contamination through the infiltration of contaminants originating from suspended matter and sediments deposited within flood retention areas in the Upper Rhine valley, as well as subsequent problems for drinking water production, were analyzed by means of the bacterial dehydrogenase activity (DHA; sediment contact test) assay with Arthrobacter globiformis and in a prolonged embryo toxicity assay using zebrafish (Danio rerio). Since the direct uptake of contaminants from particle-bound sources has usually been assumed to play only a minor role in bioaccumulation, the availability of organic extracts to biota has generally been regarded as being overestimated. In order to confirm or discard this hypothesis, organic (acetone) extracts of recently suspended, freeze-dried matter, as well as freeze-dried sediments collected from Rhine flood plains (i.e. soil samples) were compared to corresponding native samples in order to screen for the relative availability of particle-bound contaminants. Whereas a significantly higher ecotoxicological burden was observed for some native soil samples, organic extracts of suspended matter proved to be more toxic than corresponding native samples when compared to organic extracts using each test system. With respect to organic extracts, the suspended matter samples were more toxic than soil samples taken from a rarely flooded site. In contrast to the native samples, the rarely flooded soils revealed a higher toxicity than suspended matter. Therefore, organic extracts did not necessarily overestimate the toxicity of soil and suspended matter samples. Moreover, considerable toxicity of particle-bound contaminants to both bacteria and fish embryos, even in native samples, corroborate the hypothesis that particle-bound contaminants may be more readily available than is generally assumed.  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