全文获取类型
收费全文 | 15930篇 |
免费 | 199篇 |
国内免费 | 134篇 |
专业分类
安全科学 | 451篇 |
废物处理 | 584篇 |
环保管理 | 2188篇 |
综合类 | 3088篇 |
基础理论 | 3999篇 |
环境理论 | 10篇 |
污染及防治 | 3908篇 |
评价与监测 | 970篇 |
社会与环境 | 940篇 |
灾害及防治 | 125篇 |
出版年
2022年 | 119篇 |
2021年 | 126篇 |
2020年 | 110篇 |
2019年 | 135篇 |
2018年 | 200篇 |
2017年 | 240篇 |
2016年 | 331篇 |
2015年 | 282篇 |
2014年 | 371篇 |
2013年 | 1335篇 |
2012年 | 476篇 |
2011年 | 632篇 |
2010年 | 506篇 |
2009年 | 569篇 |
2008年 | 635篇 |
2007年 | 664篇 |
2006年 | 625篇 |
2005年 | 503篇 |
2004年 | 488篇 |
2003年 | 498篇 |
2002年 | 434篇 |
2001年 | 543篇 |
2000年 | 424篇 |
1999年 | 243篇 |
1998年 | 199篇 |
1997年 | 191篇 |
1996年 | 208篇 |
1995年 | 216篇 |
1994年 | 208篇 |
1993年 | 205篇 |
1992年 | 215篇 |
1991年 | 203篇 |
1990年 | 204篇 |
1989年 | 175篇 |
1988年 | 152篇 |
1987年 | 132篇 |
1986年 | 157篇 |
1985年 | 158篇 |
1984年 | 160篇 |
1983年 | 162篇 |
1982年 | 156篇 |
1981年 | 162篇 |
1980年 | 151篇 |
1979年 | 145篇 |
1978年 | 108篇 |
1977年 | 121篇 |
1974年 | 109篇 |
1973年 | 91篇 |
1972年 | 107篇 |
1971年 | 88篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
941.
This article analyses, using Bayesian networks, the circumstances surrounding workplace tasks performed using auxiliary equipment (ladders, scaffolding, etc.) that may result in falls. The information source was a survey of employees working at a height. We were able to determine the usefulness of this approach – innovative in the accident research field – in identifying the causes that have the greatest bearing on accidents involving auxiliary equipment: in these cases, the adoption of incorrect postures during work and a worker’s inadequate knowledge of safety regulations. Likewise, the duration of tasks was also associated with both these variables, and therefore, with the accident rate. Bayesian networks also enable dependency relationships to be established between the different causes of accidents. This information – which is not usually furnished by conventional statistical methods applied in the field of labour risk prevention – allow a causality model to be defined for workplace accidents in a more realistic way. With this statistic tool, the expert is also provided with useful information that can be input to a management model for labour risk prevention. 相似文献
942.
Coexistence between People and Elephants in African Savannas 总被引:3,自引:0,他引:3
Abstract: The decline in the range and numbers of elephants as a result of expanding human activity in Africa is recognized as one of the continent's more serious conservation problems. Understanding the relationship between human settlement patterns and elephant abundance is fundamental to predicting the viability of elephant populations. The prevailing model of human-elephant interaction predicts a negative linear relationship between rising human density and declining elephant density at a coarse (national or subcontinental) scale. Using observed elephant densities and human population data, we tested this prediction in a study area of 15,000 km2 in northwestern Zimbabwe. The results did not fit a linear model. Elephant and human coexistence occurs at various levels of human density, up to a threshold of human density beyond which elephant populations disappear. This threshold seems to be related to a particular stage in the process of agriculturally transformed land becoming spatially dominant over the natural woodland that constitutes elephant habitat. Within the contexts of conservation and sustainable development in African savannas, investigating spatial relationships between elephant and human abundance should be a priority topic for future research. 相似文献
943.
944.
945.
946.
947.
948.
949.
Laura E Ellison Thomas J O'Shea Daniel J Neubaum Richard A Bowen 《Ecological applications》2007,17(2):620-627
We investigated movements of female big brown bats (Eptesicus fuscus) roosting in maternity colonies in buildings in Fort Collins, Colorado (USA), during the summers of 2002, 2003, and 2005. This behavior can be of public health concern where bats that may carry diseases (e.g., rabies) move among buildings occupied by people. We used passive integrated transponders (PIT tags) to mark individual bats and hoop PIT readers at emergence points to passively monitor the use of building roosts by marked adult females on a daily basis during the lactation phase of reproduction. Multi-strata models were used to examine movements among roosts in relation to ambient temperatures and ectoparasite loads. Our results suggest that high ambient temperatures influence movements. Numbers of mites (Steatonyssus occidentalis) did not appear to influence movements of female bats among building roosts. In an urban landscape, periods with unusually hot conditions are accompanied by shifting of bats to different buildings or segments of buildings, and this behavior may increase the potential for contact with people in settings where, in comparison to their more regularly used buildings, the bats may be more likely to be of public concern as nuisances or health risks. 相似文献
950.
Mark E. Churchwell Robert L. Livingston Donald L. Sgontz Jerry D. Messman 《Environment international》1987,13(6)
The current U.S. Environmental Protection Agency (U.S. EPA) protocols for mercury determinations in aqueous and solid waste samples (SW-846 Methods 7470 and 7471) using recirculating cold-vapor atomic absorption spectrometry (CV-AAS) have been evaluated. The U.S. EPA methods are not sufficiently flexible to permit special quality control (QC) measures, have limited detectability for low-level mercury concentrations, and are plagued by spectral interferences caused by the nonspecific absorption of primary mercury radiation by volatile organic vapors. The U.S. EPA protocols have been modified in a single-laboratory study to facilitate additional QC measures, to enhance detectability for low-level mercury concentrations, and to eliminate nonspecific vapor absorption interferences. Volumetric manipulations for additional QC measures, if required, are facilitated by performing the sample digestions in Erlenmeyer flasks rather than in the current Biochemical Oxygen Demand (BOD) reduction-aeration bottles. Typical manipulations for additional QC measures that are now feasible include dilution of concentrated samples and multiple aliquot sampling for post-digestion spike and replicate analyses. Instrument detectability is improved 10-fold by using a gas sparging bottle as a dedicated reduction-aeration vessel and a silver wool-amalgamation CV-AAS system operated in an open configuration. The on-line amalgamation/thermal desorption process of the modified CV-AAS system eliminates interfering water and organic matrix vapors prior to the mercury absorption measurement. Good accuracy and precision have been obtained with the amalgamation CV-AAS system for the analyses of four reference sediment materials. The amalgamation CV-AAS measurements on the reference sediment digests have been successfully performed at absolute mercury concentration levels that are only 1 to 4 times above the instrumental detection limit of the U.S. EPA recirculating CV-AAS method. 相似文献