全文获取类型
收费全文 | 8541篇 |
免费 | 700篇 |
国内免费 | 3312篇 |
专业分类
安全科学 | 486篇 |
废物处理 | 216篇 |
环保管理 | 769篇 |
综合类 | 6315篇 |
基础理论 | 2541篇 |
环境理论 | 1篇 |
污染及防治 | 899篇 |
评价与监测 | 466篇 |
社会与环境 | 508篇 |
灾害及防治 | 352篇 |
出版年
2024年 | 56篇 |
2023年 | 217篇 |
2022年 | 327篇 |
2021年 | 381篇 |
2020年 | 320篇 |
2019年 | 319篇 |
2018年 | 349篇 |
2017年 | 366篇 |
2016年 | 468篇 |
2015年 | 473篇 |
2014年 | 548篇 |
2013年 | 868篇 |
2012年 | 677篇 |
2011年 | 731篇 |
2010年 | 563篇 |
2009年 | 557篇 |
2008年 | 459篇 |
2007年 | 633篇 |
2006年 | 606篇 |
2005年 | 499篇 |
2004年 | 398篇 |
2003年 | 440篇 |
2002年 | 347篇 |
2001年 | 323篇 |
2000年 | 269篇 |
1999年 | 208篇 |
1998年 | 165篇 |
1997年 | 159篇 |
1996年 | 136篇 |
1995年 | 151篇 |
1994年 | 109篇 |
1993年 | 93篇 |
1992年 | 75篇 |
1991年 | 66篇 |
1990年 | 53篇 |
1989年 | 31篇 |
1988年 | 27篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
本文全面分析了珠江三角洲水土资源开发利用的现状,阐明了水土资源开发利用中出现的环境问题及原因。因此,提出了该地区水土资源进一步合理开发利用的对策。 相似文献
972.
Saud A. Amer Timothy O. Keefer Mark A. Weltz David C. Goodrich Leslie B. Bach 《Journal of the American Water Resources Association》1994,30(1):69-83
ABSTRACT: Certain physical and chemical properties of soil vary with soil water content. The relationship between these properties and water content is complex and involves both the pore structure and constituents of the soil solution. One of the most economical techniques to quantify soil water content involves the measurement of electrical resistance of a dielectric medium that is in equilibrium with the soil water content. The objective of this research was to test the reliability and accuracy of fiberglass soil-moisture electrical resistance sensors (ERS) as compared to gravimetric sampling and Time Domain Reflectometry (TDR). The response of the ERS was compared to gravimetric measurements at eight locations on the USDA-ABS Walnut Gulch Experimental Watershed. The comparisons with TDR sensors were made at three additional locations on the same watershed. The high soil rock content (≥45 percent) at seven locations resulted in consistent overestimation of soil water content by the ERS method. Where rock content was less than 10 percent, estimation of soil water was within 5 percent of the gravimetric soil water content. New methodology to calibrate the ERS sensors for rocky soils will need to be developed before soil water content values can be determined with these sensors. 相似文献
973.
建立城市自然灾害承灾能力指标的思路探讨 总被引:10,自引:0,他引:10
本文论述了城市承灾能力的含义,分析了我国城市主要自然灾害以及承文体的类型和致灾因素,探讨了城市承灾能力指标,为城市承灾能力综合评判提供了依据. 相似文献
974.
David F. Grigal 《Environmental management》1985,9(5):449-454
During the winters of 1978–79 and 1979–80, a 500-kV electrical transmission right-of-way (r-o-w) was constructed across the Red Lake Peatland in northwestern Minnesota, the largest contiguous peatland in the lower 48 states of the USA. Immediately before, and for two years following construction, vascular vegetation was monitored within the r-o-w and in undisturbed control areas. Monitoring was carried out in five vegetation types: a thicket swamp, a low shrub bog, a graminoid fen, a treed bog, and a treed fen. Evaluation of construction impacts was based on vegetation structure, irrespective of species composition, and on community composition (species data for low shrubs and herbs). Construction eliminated trees from the r-o-w. Vegetation structure, excluding trees, was markedly altered in the two bog types and the treed fen type in the first postconstruction growing season. By the second season, measurable recovery to control levels had begun. The sample plots were placed into a previously developed vegetation classification system for the Red Lake Peatland, on the basis of herbs and low shrubs. There was a shift in composition in the low shrub bog and in the treed vegetation types following construction. Results of both methods of data analysis were consistent. Major vegetation changes following construction occurred in the low shrub bog and treed types. The open, low-stature fen types showed almost no changes related to construction. Even in the affected types, all vegetation strata except trees were returning to their preconstruction status by the second growing season following construction. 相似文献
975.
Peter F. M. McLoughlin 《Journal of the American Water Resources Association》1988,24(3):599-607
ABSTRACT: Third World irrigation and drainage systems have experienced major declines recently in both capability and performance. This is due initially to working them well beyond their design capaci-capacities; scouring, sedimentation, and overtopping result. Chronic O&M underfunding then adds heavily to this worsening malaise. International donors have assisted irrigation departments with rehabilitation projects and programs to improve O&M effectiveness on a grand (billions of dollars) scale. Despite their historical propensity to examine, almost fastidiously, program economic justifications (B/C, IRR, etc), the donors apparently have glossed over two basic analytic elements for (a) more spending on O&M as distinct from an equivalent spending on other means to provide farmers with an m3 of water; and (b) different levels of O&M spending on canals and drains. Surely those different levels provide differing benefits, in total, and at the margin. Which level is most economic? This paper identifies these latter analytical issues, posits methodologies key to an O&M spending level analysis, and discusses the information base. Particular attention is paid to identifying relevant costs and benefits, and to suggesting supplementary criteria for O&M spending level selection. The paper is an exercise in delineation of an imminently practical area of irrigation engineering economics. 相似文献
976.
酸沉降物对土壤化学性质的影响 总被引:1,自引:0,他引:1
本文综述了酸沉降物对土壤酸化、营养物质的淋溶、重金属的活化、矿物分解等化学性质的影响,以及阻止酸雨危害土壤的化学方法。 相似文献
977.
燃煤电厂对环境与人群所产生的辐射影响早已引起了国内外学者的关注。本文通过对四川省境内重庆、河门口、江油等燃煤电厂烟尘中天然放射性水平的分析,估算出由烟尘沉降所造成周围土壤中天然放射性本底的年增加量不到0.1%,这说明由烟尘沉降每年对土壤所产生的辐射影响是较小的;然而由于沉降的放射性在相当长的时期内存在于土壤的表层,因此随电厂运转时间的增加,其所产生的辐射影响就必须引起重视了;本文通过对电厂周围表层与深层土中天然放射性水平的比较与分析说明,燃煤电厂的长期运转有可能使周围表层土壤中天然放射性本底增加。 相似文献
978.
979.
980.