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   381篇
  免费   2篇
  国内免费   1篇
安全科学   2篇
废物处理   4篇
环保管理   9篇
综合类   202篇
基础理论   63篇
污染及防治   86篇
评价与监测   10篇
社会与环境   8篇
  2021年   3篇
  2018年   4篇
  2016年   5篇
  2014年   8篇
  2013年   12篇
  2012年   7篇
  2011年   5篇
  2010年   10篇
  2009年   16篇
  2008年   7篇
  2007年   21篇
  2006年   8篇
  2005年   7篇
  2004年   9篇
  2003年   11篇
  2002年   14篇
  2001年   8篇
  2000年   6篇
  1999年   9篇
  1998年   7篇
  1997年   5篇
  1995年   6篇
  1994年   5篇
  1993年   3篇
  1992年   4篇
  1983年   3篇
  1981年   4篇
  1978年   3篇
  1967年   4篇
  1966年   4篇
  1965年   5篇
  1964年   8篇
  1963年   11篇
  1962年   4篇
  1961年   7篇
  1960年   5篇
  1959年   6篇
  1958年   10篇
  1957年   7篇
  1956年   7篇
  1955年   12篇
  1954年   6篇
  1952年   4篇
  1951年   3篇
  1950年   6篇
  1947年   5篇
  1943年   6篇
  1939年   4篇
  1928年   2篇
  1924年   3篇
排序方式: 共有384条查询结果,搜索用时 15 毫秒
171.
Atmospheric particulate matter (PM) abundance, mass size distribution (MSD) and chemical composition are parameters relevant for human health effects. The MSD and phase state of semivolatile organic pollutants were determined at various polluted sites in addition to the PM composition and MSD. The distribution pattern of pollutants varied from side to side in correspondence to main particle sources and PM composition. Levels of particle-associated polycyclic aromatic hydrocarbons (PAHs) were 1–30 ng m?3 (corresponding to 15–35 % of the total, i.e., gas and particulate phase concentrations), of polychlorinated biphenyls (PCBs) were 2–11 pg m?3 (4–26 % of the total) and of DDT compounds were 2–12 pg m?3 (4–23 % of the total). The PM associated amounts of other organochlorine pesticides were too low for quantification. The organics were preferentially found associated with particles <0.45 μm of aerodynamic equivalent diameter. The mass fractions associated with sub-micrometer particles (PM0.95) were 73–90 %, 34–71 % and 36–81 % for PAHs, PCBs and DDT compounds, respectively. The finest particles fraction had the highest aerosol surface concentration (6.3–29.7)×10?6 cm?1 (44–70 % of the surface concentration of all size fractions). The data set was used to test gas-particle partitioning models for semivolatile organics for the first time in terms of the organics' MSD and size-dependent PM composition. The results of this study prove that at the various sites particles with diverse size, matrix composition, amount of contaminants and toxicological effects occur. Legislative regulation based on gravimetric determination of PM mass can clearly be insufficient for assessment.  相似文献   
172.
173.
Comprehensive data on environmental monitoring programs concerned with air pollutants like ozone (O3), nitrogen dioxide (NO2), nitrogen oxide (NO), carbon dioxide (CO2) und carbon monoxide (CO), and occassionally suspended dust, benzene and other environmental chemicals, are available on the free Internet. As different monitoring information systems exist in most states or big cities of the Federal Republic of Germany, a comparison of these systems with their pros and cons is of great interest to the public. Environmental air pollutant monitoring systems in 16 states of Germany are listed and evaluated by applying 5 evaluation criteria for the differentiation of these systems. Different data-analysis methods will be applied, the Hasse diagram technique, a method derived from discrete mathematics and the partially Ordered Scalogram Analysis with Coordinates (POSAC) method, a multivariate statistical approach. The important objects, the so-called maximal or minimal objects, are detected in both methods. The Internet-based environmental monitoring systems of the states of Berlin, Bremen, Saxony-Anhalt, Baden-Wurttemberg are rated good in the evaluation approaches, whereas the information systems of the states of Brandenburg, North Rhine-Westphalia, Saxony received a rather poor ranking. The attributes of DA, way of data presentation on the Internet, and ME, type and length of measurements, were pointed out in the data-analysis methods. Multivariate explorative statistical methods offer a comprehensive tool for the graphical analysis of data-matrices. The ranking of objects is given in an effective and graphically comprehensible manner using the Hasse diagram technique. The choice and preference of the methods is problem-driven. A combination of these different methods is envisaged in the authors’ future research.  相似文献   
174.
In the last few decades, the international insurance industry has been confronted with a drastic increase in the scope and frequency of great natural disasters. The trend is primarily attributable to the continuing steady growth of the world population and the increasing concentration of people and economic values in urban areas. An additional factor is the global migration of populations and industries into areas such as coastal regions, which are particularly exposed to natural hazards. The natural hazards themselves, on the other hand, are showing a change for the worse as many atmospheric extremes are strongly influenced by global warming. In addition to the problems the insurance industry has with regard to pricing, capacity and loss reserves, the assessment of insured liabilities, preventive planning and the proper adjustment of catastrophe losses are gaining importance. The present problems will be dramatically aggravated if the greenhouse predictions come true. The changing probability distributions of many processes in the atmosphere will force up the frequency and severity of heat waves, droughts, bush fires, tropical and extratropical cyclones, tornados, hailstorms, floods and storm surges in many parts of the world with serious consequences for all types of property insurance, apart from the consequences of the stratospheric ozone destruction for health and life insurance. Rates will have to be raised and in certain areas insurance cover will only be available after considerable restrictions have been imposed, as for example significant deductibles and low liability or loss limits. In areas of high insurance density the loss potential of individual catastrophes can reach a level at which the national and international insurance industries will run into serious capacity problems. Recent disasters showed the disproportionately high participation of reinsurers in extreme disaster losses and the need for more risk transparency if the insurance industry is to fulfil its obligations in an increasingly hostile environment.  相似文献   
175.
Few reports concerning intrauterine shunting are available. We investigated the impact of this method. In order to evaluate intrauterine shunting and the complication rate for different indications, we sent a questionnaire to all German-speaking level 3 centres. In four level 3 centres, 52 intrauterine catheters were inserted in 34 fetuses. The indications were uni- or bilateral hydrothorax in nine cases, cystic adenomatoid malformation of the lung in four cases, infravesical stenosis in 13 cases, and fetal ascites in eight cases. In three cases (6 per cent), difficulties occurred when the drain was inserted. In 15 cases (29 per cent), the function of the drain was reduced by dislocation or occlusion. The mortality rate caused by shunting was as high as eight per cent (four cases). The application of an intrauterine shunt currently represents a rarely performed ultrasound-guided therapeutic intervention in the fetus. In all cases, the indication for shunting is to avoid compression of normal tissue by cystic structures. A high complication rate restricts the application of drainage to selected cases.  相似文献   
176.
The terms growth and evolution can as well be applied to unstable physical systems. The ability of instabilities to create visible shape is being investigated. There are innumerable examples of that in the universe. One class occurring in cosmical plasmas results from the localized dissipation of energy stored in strongly sheared magnetic fields. It leads to the appearance of dynamic luminous structures, as for instance in solar flares and in the northern lights.  相似文献   
177.
178.
179.
180.
All classes of vertebrates harbor tumor viruses that are capable of inducing either tumors or leukemias. After infection, their genomes become integral parts of the host cell's genetic material (DNA). Many biological functions such as the capacity to code for the synthesis of new proteins and, in particular, the oncogenic property (oncogen) have already been assigned to specific regions (on physical maps) of their DNA.  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