全文获取类型
收费全文 | 35136篇 |
免费 | 376篇 |
国内免费 | 502篇 |
专业分类
安全科学 | 1050篇 |
废物处理 | 1643篇 |
环保管理 | 4114篇 |
综合类 | 5768篇 |
基础理论 | 8943篇 |
环境理论 | 22篇 |
污染及防治 | 9214篇 |
评价与监测 | 2467篇 |
社会与环境 | 2589篇 |
灾害及防治 | 204篇 |
出版年
2023年 | 164篇 |
2022年 | 406篇 |
2021年 | 398篇 |
2020年 | 276篇 |
2019年 | 331篇 |
2018年 | 575篇 |
2017年 | 595篇 |
2016年 | 867篇 |
2015年 | 651篇 |
2014年 | 1038篇 |
2013年 | 2818篇 |
2012年 | 1233篇 |
2011年 | 1639篇 |
2010年 | 1324篇 |
2009年 | 1381篇 |
2008年 | 1641篇 |
2007年 | 1716篇 |
2006年 | 1459篇 |
2005年 | 1270篇 |
2004年 | 1161篇 |
2003年 | 1224篇 |
2002年 | 1088篇 |
2001年 | 1402篇 |
2000年 | 1001篇 |
1999年 | 579篇 |
1998年 | 394篇 |
1997年 | 411篇 |
1996年 | 398篇 |
1995年 | 482篇 |
1994年 | 490篇 |
1993年 | 388篇 |
1992年 | 413篇 |
1991年 | 390篇 |
1990年 | 442篇 |
1989年 | 381篇 |
1988年 | 326篇 |
1987年 | 306篇 |
1986年 | 259篇 |
1985年 | 285篇 |
1984年 | 304篇 |
1983年 | 285篇 |
1982年 | 278篇 |
1981年 | 248篇 |
1980年 | 209篇 |
1979年 | 229篇 |
1978年 | 199篇 |
1977年 | 143篇 |
1975年 | 162篇 |
1972年 | 160篇 |
1971年 | 155篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
This paper describes the help given by the social services department of a shipping company to bereaved families following a shipping disaster. In the absence of clear, factual and prompt information from an authoritative source, there is a tendency for bereaved individuals to deny their loss and thereby delay the process of mourning and eventual recovery. Appropriate intervention and support can help to overcome this tendency as was seen in the Madasa case. 相似文献
122.
Marine Biology - The combined effects of temperature and salinity on the rate of oxygen consuption by the estuarine crab Panopeus herbstii Milne-Edwards (Crustacea: Decapoda: Xanthidae) were... 相似文献
123.
124.
Gunavant M. Oza 《The Environmentalist》2003,23(2):189-192
Much of the forest wealth on the plains and in the hilly areas of India has been foolishly destroyed, and the rich heritage of wildlife has been slaughtered mostly for only temporary gain. The wanton axing of the larger indigenous trees and the uprooting of other floristic elements in the hills and on the lower slopes of the mountains, gradually impoverishes them, and may be followed by erosion that ultimately leaves the slopes barren. These alarming threats to the chir (Pinus roxburghii) and fir (Abies pindrow) forests of Kashmir will have disastrous consequences. Once densely-forested, the mountain slopes in Kashmir have become largely naked through too-heavy tapping and cutting of the trees; with concomitant landslides, frequent floods, and loss of fertile topsoil. Unfortunately, the people living in the areas of the chir and fir trees, do not play a proper part in their protection, and the last two decades have witnessed, year by year, the rapid march of urbanization and manifold destructive activities which have taken a heavy toll on these precious species. Urgent conservation measures are essential to preserve these endangered trees in Kashmir. 相似文献
125.
Kathleen M. Leonard Timothy LeDuc R.Kyle Mixon 《Waste management (New York, N.Y.)》1996,16(8):727-734
This paper describes a novel technology for the removal of solidified radioactive waste from underground storage tanks at the DOE Hanford site in southeast Washington. The process involves the use of a unique high pressure system which pulverizes the hardened saltcake with stainless steel pellets to a powder for easy vacuum removal. The steel pellets can be magnetically separated from the waste material for re-use. Specifically this study analyzes the effects of various steel abrasives, pressure of the air stream, and stand-off distance on removal rates and penetration depth on simulated saltcake samples using the high pressure technique. A full-scale test set-up and protocol were implemented to allow for comprehensive testing. To insure reproducibility of the method, tests were then run for the optimum removal parameters. A time-dependent test was also conducted to determine the relationship of removal rates to length of pressure blasts. The results of these tests revealed that stand-off distance and pressure could be positively correlated to removal volumes. Additionally, a statistical analysis confirmed that nozzle angle is independent of removal rate. This study demonstrated that the pellet ‘blaster’ technique is a safe, effective method for removal of radioactive wastes without any increase in either waste mass or volume. 相似文献
126.
Corporations own approximately 25% of all private land in the United States and, therefore, play an essential role in protecting biodiversity and maintaining natural habitats. The Wildlife Habitat Council (WHC) is a unique joint venture between conservation organizations and corporations to utilize corporate lands for ensuring biodiversity. The following case studies demonstrate how corporations have helped ensure healthy ecosystems and provided critical leadership in regional efforts. Amoco Chemical Company's Cooper River Plant has been instrumental in developing a cooperative project that involves numerous corporations, plantation owners, private citizens, nonprofit organizations, government agencies, and community groups to develop a comprehensive, ecosystem-based management plan for part of the Cooper River in Charleston, South Carolina, USA. The second case focuses on the Morie Company, a national sand quarry operator headquartered in southern New Jersey, USA. Morie Company is working with WHC, community groups, the Pinelands Commission, and other state regulatory agencies to explore sustainable development opportunities for companies within the Pinelands regulations. The third case takes us to DuPont Company's Asturias, Spain, site. A win—win success story of improved habitat and cost savings is the result of DuPont's concern for the environment, ability to work with a variety of groups, and willingness to consider innovative restoration techniques. The fourth case discusses Consumers Power Company's Campbell Plant in West Olive, Michigan, USA. In addition to implementing projects that contribute to biodiversity, Consumers Power has developed an environmental education field station to teach others about the importance of natural habitats. The final case highlights Baltimore Gas & Electric Company's efforts to maintain habitat for endangered species at their Calvert Cliffs site in Maryland. 相似文献
127.
128.
Peggy A. Johnson Thomas M. Heil 《Journal of the American Water Resources Association》1996,32(6):1283-1291
ABSTRACT: Bankfull depth and discharge are basic input parameters to stream planform, stream restoration, and highway crossing designs, as well as to the development of hydraulic geometry relationships and the classification of streams. Unfortunately, there are a wide variety of definitions for bankfull that provide a range of values, and the actual selection of bankfull is subjective. In this paper, the relative uncertainty in determining the bankfull depth and discharge is quantified, first by examining the variability in the estimates of bankfull and second by using fuzzy numbers to describe bankfull depth. Fuzzy numbers are used to incorporate uncertainty due to vagueness in the definition of bankfull and subjectivity in the selection of bankfull. Examples are provided that demonstrate the use of a fuzzy bankfull depth in sediment trans. port and in stream classification. Using fuzzy numbers to describe bankfull depth rather than a deterministic value allows the engineer to base designs and decisions on a range of possible values and associated degrees of belief that the bankfull depths take on each value in that range. 相似文献
129.
Liang Chen Syed H. Imam Sherald H. Gordon Richard V. Greene 《Journal of Polymers and the Environment》1997,5(2):111-117
Starch-PVOH cast films were prepared with and without crosslinking agent (hexamethoxymethylmelamine) in the absence of plasticizer.
Moisture absorption in films without crosslinking agent at a low relative humidity was similar to that of PVOH and increased
as the relative humidity increased. Films with crosslinking agent showed moisture absorption linearly proportional to the
relative humidity. Significant improvement in resistance to water disintegration for crosslinked starch-PVOH films was observed.
While the tensile strength decreased with increased relative humidity, crosslinking significantly improved the tensile strength.
Increased PVOH content improved elongation of films even when the relative humidity was 80% or higher. Biodegradation studies
revealed that the degradation rate was negatively correlated with the PVOH content in films and crosslinking generated more
converged degradation curves.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
130.
Groundwater was being remediated with pump and treat technology at a facility where the groundwater was contaminated with commonly used degreaser solvents. Hydraulic conductivity of the heterogeneous residuum was beneficiated by applying pneumatic fracturing technology. The remedial system was controlled and monitored by a sophisticated remote telemetry system. A case history follows. 相似文献