全文获取类型
收费全文 | 44085篇 |
免费 | 483篇 |
国内免费 | 665篇 |
专业分类
安全科学 | 1351篇 |
废物处理 | 1950篇 |
环保管理 | 5683篇 |
综合类 | 7675篇 |
基础理论 | 11180篇 |
环境理论 | 16篇 |
污染及防治 | 11425篇 |
评价与监测 | 3033篇 |
社会与环境 | 2631篇 |
灾害及防治 | 289篇 |
出版年
2022年 | 438篇 |
2021年 | 423篇 |
2020年 | 343篇 |
2019年 | 375篇 |
2018年 | 698篇 |
2017年 | 678篇 |
2016年 | 1054篇 |
2015年 | 767篇 |
2014年 | 1173篇 |
2013年 | 3533篇 |
2012年 | 1478篇 |
2011年 | 1984篇 |
2010年 | 1640篇 |
2009年 | 1714篇 |
2008年 | 1920篇 |
2007年 | 2025篇 |
2006年 | 1784篇 |
2005年 | 1522篇 |
2004年 | 1461篇 |
2003年 | 1417篇 |
2002年 | 1335篇 |
2001年 | 1718篇 |
2000年 | 1253篇 |
1999年 | 813篇 |
1998年 | 538篇 |
1997年 | 542篇 |
1996年 | 581篇 |
1995年 | 616篇 |
1994年 | 548篇 |
1993年 | 493篇 |
1992年 | 481篇 |
1991年 | 491篇 |
1990年 | 481篇 |
1989年 | 461篇 |
1988年 | 420篇 |
1987年 | 348篇 |
1986年 | 339篇 |
1985年 | 349篇 |
1984年 | 422篇 |
1983年 | 366篇 |
1982年 | 423篇 |
1981年 | 358篇 |
1980年 | 288篇 |
1979年 | 345篇 |
1978年 | 274篇 |
1977年 | 254篇 |
1976年 | 236篇 |
1975年 | 227篇 |
1974年 | 243篇 |
1972年 | 226篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Previous work has shown that the breeding density of a bird characteristic of upland streams, the dipper Cinclus cinclus, is markedly reduced at low pH in both Wales and Scotland. Populations also declined when streams became more acidic. Evidence of causal explanation for these relationships is that: (1) Food quantity is reduced in acidic streams, and important prey, including those rich in calcium, are scarce; (2) Blood chemistry in pre-breeding birds differs between acid and circumneutral streams, with plasma calcium reduced in those breeding at low pH. Skeletal sources of calcium are probably limited; (3) The time spent foraging by pre-breeding birds on acidic streams is markedly increased, even though overall energy costs on acidic and circumneutral streams are similar. Body condition is inferior to birds on circumneutral streams; (4) Egg laying is significantly delayed on acidic streams irrespective of an effect on laying of altitude, and clutch and brood sizes are significantly reduced; (5) Eggs are lighter and shells thinner at low pH; (6) Chick growth is reduced at low pH; (7) Contamination by heavy metals and persistent organochlorines is low in the populations on acidic streams and cannot explain the impaired breeding performance. None of these features can exclude the possibilities that acidic streams either hold populations of poor quality birds, which show the above features, or that acidity affects the breeding ecology of all dippers that attempt to breed at low pH. The qualitative outcome of these two alternatives is identical. 相似文献
42.
L Weaver 《Journal - Water Pollution Control Federation》1966,38(8):1334-1344
43.
44.
45.
46.
A Barba M A Camara S Navarro Garcia C Sanchez-Fresneda N Lopez de Hierro A Acebes 《Journal of environmental science and health. Part. B》1991,26(3):323-332
Residues of Bromopropylate were determine in artichokes, strawberries and beans after foliar spray of acaricide at two rates. The rates used were 1 g/l formulated product (normal recommended) and 1.5 g/l. The residue levels of bromopropylate in the three crops after 14 days were lower than 0.7 ppm and did not exceed the Maximum Residual Level (MRL) recommended by FAO. In the artichokes and strawberries, the total concentration of residues decreased by 50% of the initial level after 2-3 days. Only trace levels of the bromopropylate residues (less than 0.01 ppm) were detected in the "hearts" of the artichokes. Bromopropylate residues in the green beans were also less than 0.8 ppm after the first day of foliar spraying. The kinetic of degradation occurred in two different steps. In the first step (4-6 days) the dissipation of bromopropylate was faster whereas in the second step (7-14 days) the loss of residues was much slower. 相似文献
47.
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).
48.
49.
The importance of temperature in assessing iron pipe corrosion in water distribution systems 总被引:1,自引:0,他引:1
Temperature is expected to play a significant role in the corrosion of iron pipes in drinking water distribution systems. Temperature impacts many parameters that are critical to pipe corrosion including biological activity, physical properties of the solution, thermodynamic and physical properties of corrosion scale, and chemical rates. Moreover, variations in temperature and temperature gradients may give rise to new corrosion phenomena worthy of consideration by water treatment personnel. 相似文献
50.
In many situations, the effect of a toxic chemical on a biological system depends on both the intensity and the duration of exposure. The dependence on the time dimension can be the expression of a range of processes including the physical accumulation of toxic chemicals or their metabolites and the functional accumulation of damage. Measures and functions that have been used to describe this dependence are reviewed.Some of these functions are compared through a case study of the neurotoxicity of methylmercury. Use is made of data that indicates a dependency between the blood concentration at which monkeys were exposed and the length of time before damage was detected. Several exposure functions are fitted to these data and their appropriateness is compared. Using the most appropriate function, an exposure-response relationship is developed using probit analysis. An alternative data analysis procedure is also investigated. The apparent threshold after a 100 day exposure is estimated to be greater by a factor of 3–5 compared to the threshold for chronic exposure. Applying this factor to man, the blood concentration threshold for chronic exposure is estimated to be 40–170 ppb, a finding consistent with recent reports of neurological damage in humans exposed below the generally accepted threshold. 相似文献