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   53656篇
  免费   587篇
  国内免费   639篇
安全科学   1726篇
废物处理   2494篇
环保管理   7094篇
综合类   8451篇
基础理论   14427篇
环境理论   25篇
污染及防治   13122篇
评价与监测   3678篇
社会与环境   3538篇
灾害及防治   327篇
  2023年   226篇
  2022年   480篇
  2021年   530篇
  2020年   360篇
  2019年   443篇
  2018年   1069篇
  2017年   1095篇
  2016年   1443篇
  2015年   947篇
  2014年   1409篇
  2013年   4092篇
  2012年   1869篇
  2011年   2782篇
  2010年   2150篇
  2009年   2203篇
  2008年   2681篇
  2007年   2781篇
  2006年   2067篇
  2005年   1815篇
  2004年   1701篇
  2003年   1791篇
  2002年   1651篇
  2001年   1937篇
  2000年   1375篇
  1999年   835篇
  1998年   622篇
  1997年   618篇
  1996年   632篇
  1995年   749篇
  1994年   706篇
  1993年   593篇
  1992年   633篇
  1991年   619篇
  1990年   608篇
  1989年   570篇
  1988年   504篇
  1987年   449篇
  1986年   414篇
  1985年   425篇
  1984年   475篇
  1983年   444篇
  1982年   463篇
  1981年   386篇
  1980年   310篇
  1979年   340篇
  1978年   299篇
  1977年   228篇
  1975年   245篇
  1973年   232篇
  1972年   243篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
Pomonis A 《Disasters》1990,14(2):89-114
The 1988 earthquake in Armenia was the most serious seismic disaster since the 1976 earthquake in Tangshan, China. At least 25,000 people lost their lives in a tremor of moderate magnitude and the USSR suffered a loss of more than 2.5 per cent of 1988's GDP. Research at the Martin Centre on the effects of earthquakes on human lives has shown an increase in global earthquake mortality rate, despite the well known improvements in some countries. The Armenian disaster was a warning to all of us concerned with natural or man-made disasters. Areas of potential high hazard are pointed out for the sub-Caucasian region. Construction practices similar to those in Armenia are certainly found in many other parts of the world, with some regional variations, and the fast assimilation of the lessons is an important target. The structural characteristics of all the residential building types existing in the affected area are presented in terms of their seismic vulnerability. Vulnerable points are discussed with a view to low cost interventions that will drastically improve the seismic safety of new buildings.  相似文献   
53.
Ornas AH 《Disasters》1990,14(2):115-122
The most vulnerable people in Third World countries are often accused of destroying forests and fragile ecosystems and of practising destructive forms of agriculture and animal husbandry. The key to environmental sustainability, however, lies in more reliable production and food security at the local level. This article focuses on individual and household security amongst dryland herders in East Africa. The most crucial aspect of pastoral viability is the maintenance of a balance between family herd and size of household. Risk-spreading, through dependence on relatives, the borrowing of animals, redistribution through marriage etc. is a general principle of social behaviour amongst these peoples. Consideration of local-level security, furthermore, reveals the connection between ecological stress and political conflict. Only by establishing secure access to food for individuals and families can sustainable development and political security, not only at the local but also at the national and international levels, be achieved.  相似文献   
54.
Concerns over data quality have raised many questions related to sampling soils for volatile organic compounds (VOCs). This paper was prepared in response to some of these questions and concerns expressed by Remedial Project Managers (RPMs) and On-Scene Coordinators (OSCs). The following questions are frequently asked:
  1. Is there a specific device suggested for sampling soils for VOCs?
  2. Are there significant losses of VOCs when transferring a soil sample from a sampling device (e.g., split spoon) into the sample container?
  3. What is the best method for getting the sample from the split spoon (or other device) into the sample container?
  4. Are there smaller devices such as subcore samplers available for collecting aliquots from the larger core and efficiently transferring the sample into the sample container?
  5. Are certain containers better than others for shipping and storing soil samples for VOC analysis?
  6. Are there any reliable preservation procedures for reducing VOC losses from soil samples and for extending holding times?
Guidance is provided for selecting the most effective sampling device for collecting samples from soil matrices. The techniques for sample collection, sample handling, containerizing, shipment, and storage described in this paper reduce VOC losses and generally provide more representative samples for volatile organic analyses (VOA) than techniques in current use. For a discussion on the proper use of sampling equipment the reader should refer to other sources (Acker, 1974; U.S. EPA, 1983; U.S. EPA, 1986a). Soil, as referred to in this report, encompasses the mass (surface and subsurface) of unconsolidated mantle of weathered rock and loose material lying above solid rock. Further, a distinction must be made as to what fraction of the unconsolidated material is soil and what fraction is not. The soil component here is defined as all mineral and naturally occurring organic material that is 2 mm or less in size. This is the size normally used to differentiate between soils (consisting of sands, silts, and clays) and gravels. Although numerous sampling situations may be encountered, this paper focuses on three broad categories of sites that might be sampled for VOCs:
  1. Open test pit or trench.
  2. Surface soils (<5 ft in depth).
  3. Subsurface soils (>5 ft in depth).
  相似文献   
55.
Polycyclic aromatic hydrocarbons (PAH) include compounds with two or more fused benzene rings, many of which are carcinogens. Industrial sources produce hundreds of PAH, notably in the coke- and aluminium-producing industries. Because PAH are distributed at varying levels between gaseous and particulate phases, exposure assessment has been problematic. Here, we recommend that occupational exposures to naphthalene be considered as a potential surrogate for occupational PAH exposure for three reasons. Naphthalene is usually the most abundant PAH in a given workplace; naphthalene is present almost entirely in the gaseous phase and is, therefore, easily measured; and naphthalene offers several useful biomarkers, including the urinary metabolites 1- and 2-hydroxynaphthalene. These biomarkers can be used to evaluate total-body exposure to PAH, in much the same way that 1-hydroxypyrene has been applied. Using data from published sources, we show that log-transformed airborne levels of naphthalene are highly correlated with those of total PAH (minus naphthalene) in several industries (creosote impregnation: Pearson r= 0.815, coke production: r= 0.917, iron foundry: r= 0.854, aluminium production: r= 0.933). Furthermore, the slopes of the log-log regressions are close to one indicating that naphthalene levels are proportional to those of total PAH in those industries. We also demonstrate that log-transformed urinary levels of the hydroxynaphthalenes are highly correlated with those of 1-hydroxypyrene among coke oven workers and controls (r= 0.857 and 0.876), again with slopes of log-log regressions close to one. These results support the conjecture that naphthalene is a useful metric for occupational PAH exposure. Since naphthalene has also been shown to be a respiratory carcinogen in several animal studies, it is also argued that naphthalene exposures should be monitored per se in industries with high levels of PAH.  相似文献   
56.
57.
Summary As stated at the beginning of this paper conclusions reached thus far cannot be discussed in this paper. However, a great deal of information is available for examination.EPA displayed its ability to coordinate widely separated laboratories, both Federal and private, into a smooth working team in a very short period of time. A very comprehensive study plan was also developed and implemented quickly. EPA was fortunate to have already had GCA under contract when the emergency arose. In no small part the success of the field effort was due to the managerial and technical abilities of the GCA team.Within a period of 6 weeks a plan was developed, a prime contractor retained, subcontractors hired, and field activities begun. Within a period of 3 months in excess of 8600 field samples were collected and over 12,000 field and QC samples were analyzed. During this same period 2 major data systems were developed, debugged, and placed into operation.In short this EPA project was probably the most comprehensive multimedia field project ever attempted by EPA and certainly the data is being subjected to the most strenuous quality control measures ever imposed by this Agency. The entire program is presently under peer review and the results are being prepared for publication by EPA Headquarters.Note. Originally intended to be published as part of the special issue on Exposure Monitoring: An International Workshop (Las Vegas, Nevada, October 19–22, 1981).  相似文献   
58.
59.
A number of methods has been proposed for dealing with single-factor or factorial experiments when the requirements for performing the normal theory analysis of variance procedure are not satisfied. This paper suggests the use of the likelihood ratio statistic for testing the main effects and the interaction between the factors in two-way layout of count data following negative binomial distributions with a common dispersion parameter. The likelihood ratio statistic for testing the equality of the dispersion parameters of several groups of count data is also derived. The methods is illustrated by an example concerning the study of spatial and temporal variation of bacterial counts.  相似文献   
60.
Graphical methods can play an important role in the reliable assessment of trends in typically ill behaved river quality data series both as diagnostic tools and as visual corroborative evidence when assumptions required for formal statistical tests are not met. Robust, graphically-oriented trend diagnosis procedures are presented for data series characterized by nonnormal populations, uneven time spacing, nonmonotonic trend and other factors which can create serious problems for standard parametric time series methods. Cleveland's robust locally weighted regression (RLWR) developed for investigating nonlinearity in x-y scatterplots is adapted as a robust/resistant smoothing filter for the analysis of irregular time series comprising quantitative observations. Low powered RLWR trend lines reveal temporally local phenomena, e.g. abrupt jumps (often associated with point source impacts) and periodicities, while higher powered RLWR yields smooth lines characterizing medium and longer term trends. Simple variants of Tukey smoothing concepts are developed for series with censored observations. Applications to Ontario river quality series reveal that graphical evidence is frequently sufficient to obviate the need for formal trend testing. The methods are generally applicable to most time series.  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