全文获取类型
收费全文 | 16394篇 |
免费 | 234篇 |
国内免费 | 149篇 |
专业分类
安全科学 | 586篇 |
废物处理 | 597篇 |
环保管理 | 2775篇 |
综合类 | 2613篇 |
基础理论 | 4352篇 |
环境理论 | 14篇 |
污染及防治 | 3890篇 |
评价与监测 | 1029篇 |
社会与环境 | 782篇 |
灾害及防治 | 139篇 |
出版年
2023年 | 118篇 |
2022年 | 152篇 |
2021年 | 152篇 |
2020年 | 133篇 |
2019年 | 157篇 |
2018年 | 280篇 |
2017年 | 261篇 |
2016年 | 387篇 |
2015年 | 307篇 |
2014年 | 416篇 |
2013年 | 1259篇 |
2012年 | 572篇 |
2011年 | 769篇 |
2010年 | 596篇 |
2009年 | 698篇 |
2008年 | 757篇 |
2007年 | 750篇 |
2006年 | 655篇 |
2005年 | 598篇 |
2004年 | 515篇 |
2003年 | 499篇 |
2002年 | 478篇 |
2001年 | 552篇 |
2000年 | 432篇 |
1999年 | 275篇 |
1998年 | 203篇 |
1997年 | 210篇 |
1996年 | 220篇 |
1995年 | 261篇 |
1994年 | 260篇 |
1993年 | 221篇 |
1992年 | 183篇 |
1991年 | 203篇 |
1990年 | 196篇 |
1989年 | 192篇 |
1988年 | 144篇 |
1987年 | 147篇 |
1986年 | 154篇 |
1985年 | 129篇 |
1984年 | 149篇 |
1983年 | 152篇 |
1982年 | 167篇 |
1981年 | 147篇 |
1980年 | 126篇 |
1979年 | 125篇 |
1978年 | 101篇 |
1977年 | 91篇 |
1976年 | 74篇 |
1975年 | 83篇 |
1973年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
The movement and digestion of food in the gut ofOligometra serripinna (Carpenter) were studied at Lizard Island (14°3842S; 145°2710E) in the austral winter of 1986. Feather stars in the laboratory were fed a brief, small meal of brine shrimp nauplii and killed at increasing time intervals thereafter. Histological reconstructions showed that the ingested nauplii progressed along the digestive tract surprisingly quickly. Some nauplii were found in the mid and hind intestine in only 30 min, and all of the nauplii had reached the hind intestine and rectum in 1 h. Digestion of the nauplii had started at 1 h, and only a few fragments of naupliar exoskeleton remained in the hind intestine and rectum 5 h after the start of feeding. Videotape analysis showed that no fecal pellets were released during this experiment. In the natural environment ofO. serripinna, ingested particles may similarly be transported quickly to the hind part of the gut and digested there — when feather stars were fixed in the field, most of the gut contents were found in the hind intestine and rectum.O. serripinna, which efficiently rejects inert particles before they are ingested, usually defecates infrequently (probably not more than once over a span of many hours) and differs from some other feather stars that ingest numerous inert particles and defecate much more frequently. When specimens ofO. serripinna were fed continuously on brine shrimp nauplii,Artemia sp. (San Francisco strain), in the laboratory, the feather stars fed gluttonously, packing their guts with several hundred nauplii in 1 to 2 h. Thereafter, superfluous feeding began (i.e., further ingestions appeared to force undigested nauplii, some of them still living, out of the anus). These observations suggest thatO. serripinna usually feeds at relatively modest rates in its natural habitat, but can feed gluttonously to take advantage of infrequent patches of highly concentrated, nutritious particles (e.g. copepod swarms, migrating demersal zooplankton, and invertebrate gametes from mass spawnings). It is likely that such patches of nutritious particles are usually small enough to drift out of reach of the feather stars before gluttonous feeding proceeds to superfluous feeding. Opportunities for superfluous feeding in nature are probably very infrequent (e.g. ingestion of coral gametes and embryos after a mass spawning), and the feather stars evidently have no behavior that stops further ingestions after the gut becomes filled to capacity. 相似文献
43.
David R. McCallum 《Environmental monitoring and assessment》1987,8(3):199-215
The environmental impact assessment procedure for Canadian federal government projects is briefly described. In the non-legislated Canadian system, follow-up to assessments is one of the major means of encouraging and improving the implementation of environmental impact assessment and the quality of environmental work done around development projects. The results of a study on the status of follow-up in the Canadian Government are presented. Factors that limit and that are conducive to follow-up are discussed. The effectiveness of follow-up depends as much on the circumstances surrounding a project and the concerned parties as on the follow-up techniques used; both of these aspects can be addressed in the planning and management of follow-up and of environmental impact assessment overall. Areas for improving the management of follow-up are identified and discussed: planning of follow-up activities, coordination of concerned parties, generation of clear understandings, information management, resource allocation, and maintenance of credibility. A method for planning follow-up activities for specific projects is presented. 相似文献
44.
45.
T. E. Lewis A. B. Crockett R. L. Siegrist 《Environmental monitoring and assessment》1994,30(3):213-246
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:
- Is there a specific device suggested for sampling soils for VOCs?
- Are there significant losses of VOCs when transferring a soil sample from a sampling device (e.g., split spoon) into the sample container?
- What is the best method for getting the sample from the split spoon (or other device) into the sample container?
- 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?
- Are certain containers better than others for shipping and storing soil samples for VOC analysis?
- Are there any reliable preservation procedures for reducing VOC losses from soil samples and for extending holding times?
- Open test pit or trench.
- Surface soils (<5 ft in depth).
- Subsurface soils (>5 ft in depth).
46.
47.
48.
Meklin T Haugland RA Reponen T Varma M Lummus Z Bernstein D Wymer LJ Vesper SJ 《Journal of environmental monitoring : JEM》2004,6(7):615-620
Indoor mold concentrations were measured in the dust of moldy homes (MH) and reference homes (RH) by quantitative PCR (QPCR) assays for 82 species or related groups of species (assay groups). About 70% of the species and groups were never or only rarely detected. The ratios (MH geometric mean : RH geometric mean) for 6 commonly detected species (Aspergillus ochraceus, A. penicillioides, A. unguis, A. versicolor, Eurotium group, and Cladosporium sphaerospermum) were >1 (Group I). Logistic regression analysis of the sum of the logs of the concentrations of Group I species resulted in a 95% probability for separating MH from RH. These results suggest that it may be possible to evaluate whether a home has an abnormal mold condition by quantifying a limited number of mold species in a dust sample. Also, four common species of Aspergillus were quantified by standard culturing procedures and their concentrations compared to QPCR results. Culturing underestimated the concentrations of these four species by 2 to 3 orders of magnitude compared to QPCR. 相似文献
49.
Mehaffey MH Nash MS Wade TG Ebert DW Jones KB Rager A 《Environmental monitoring and assessment》2005,107(1-3):29-44
The Catskill/Delaware reservoirs supply 90% of New York City’s drinking water. The City has implemented a series of watershed protection measures, including land acquisition, aimed at preserving water quality in the Catskill/Delaware watersheds. The objective of this study was to examine how relationships between landscape and surface water measurements change between years. Thirty-two drainage areas delineated from surface water sample points (total nitrogen, total phosphorus, and fecal coliform bacteria concentrations) were used in step-wise regression analyses to test landscape and surface-water quality relationships. Two measurements of land use, percent agriculture and percent urban development, were positively related to water quality and consistently present in all regression models. Together these two land uses explained 25 to 75% of the regression model variation. However, the contribution of agriculture to water quality condition showed a decreasing trend with time as overall agricultural land cover decreased. Results from this study demonstrate that relationships between land cover and surface water concentrations of total nitrogen, total phosphorus, and fecal coliform bacteria counts over a large area can be evaluated using a relatively simple geographic information system method. Land managers may find this method useful for targeting resources in relation to a particular water quality concern, focusing best management efforts, and maximizing benefits to water quality with minimal costs.The United States Environmental Protection Agency through its Office of Research and Development funded and managed the research described here. It has been subjected to Agency’s administrative review and approved for publication as an EPA document. 相似文献
50.
B. Beck-Friis M. Pell U. Sonesson H. Jönsson H. Kirchmann 《Environmental monitoring and assessment》2000,62(3):317-331
Composting can be a source of N2O andCH4 production. In this investigation, differentcompost heaps of organic household waste weremonitored with the focus on potential formation ofCH4 and N2O in the heaps and emission ofthese gases from the heaps. The studied compost heapshad different compost ages, turning intervals andcompost sizes. The analysed compost gases containedbetween 1–3421 L of N2O-N L-1 and 0–470 mL of CH4 L-1. The emission rates ofN2O and CH4 from the compost heaps werebetween 1–1464 mg N2O m-2 day-1 and0–119 000 mg CH4 m-2 day-1. These verylarge differences in compost gas composition andemission indicate the importance of compostmanagement. The results also give an understanding ofwhere in the composting process an increasing emissionof N2O and CH4 can occur. 相似文献