全文获取类型
收费全文 | 20394篇 |
免费 | 181篇 |
国内免费 | 205篇 |
专业分类
安全科学 | 536篇 |
废物处理 | 987篇 |
环保管理 | 2420篇 |
综合类 | 2695篇 |
基础理论 | 5299篇 |
环境理论 | 4篇 |
污染及防治 | 5602篇 |
评价与监测 | 1659篇 |
社会与环境 | 1455篇 |
灾害及防治 | 123篇 |
出版年
2023年 | 92篇 |
2022年 | 217篇 |
2021年 | 218篇 |
2020年 | 140篇 |
2019年 | 178篇 |
2018年 | 326篇 |
2017年 | 320篇 |
2016年 | 528篇 |
2015年 | 362篇 |
2014年 | 575篇 |
2013年 | 1744篇 |
2012年 | 673篇 |
2011年 | 862篇 |
2010年 | 803篇 |
2009年 | 788篇 |
2008年 | 887篇 |
2007年 | 978篇 |
2006年 | 871篇 |
2005年 | 716篇 |
2004年 | 725篇 |
2003年 | 712篇 |
2002年 | 678篇 |
2001年 | 925篇 |
2000年 | 635篇 |
1999年 | 393篇 |
1998年 | 278篇 |
1997年 | 246篇 |
1996年 | 291篇 |
1995年 | 270篇 |
1994年 | 251篇 |
1993年 | 233篇 |
1992年 | 240篇 |
1991年 | 208篇 |
1990年 | 214篇 |
1989年 | 219篇 |
1988年 | 197篇 |
1987年 | 158篇 |
1986年 | 126篇 |
1985年 | 138篇 |
1984年 | 169篇 |
1983年 | 153篇 |
1982年 | 193篇 |
1981年 | 134篇 |
1980年 | 119篇 |
1979年 | 152篇 |
1978年 | 118篇 |
1977年 | 107篇 |
1976年 | 100篇 |
1975年 | 83篇 |
1974年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Unemployment effects of climate policy 总被引:1,自引:0,他引:1
This paper models the unemployment effects of restrictions on greenhouse gas emissions, embodying two of the most significant types of short-term economic imperfections that generate unemployment: sectoral rigidities in labor mobility and sectoral rigidities in wage adjustments. A labor policy is also analyzed that would reduce the direct negative economic effects of the emissions restrictions.The politics of limiting greenhouse gas emissions are often dominated by relatively short-term considerations. Yet the current economic modeling of emissions limitations does not embody economic features that are likely to be particularly important in the short term, in particular, the politically sensitive unemployment rate. Moreover, only a few of these studies also consider policies that would offset the negative direct economic effects of emissions restrictions. For plausible estimates of the parameters, the model shows that, with the labor market imperfections, if there were no offsetting policies, the reductions in GNP in the U.S. in the first 10 years after emissions restrictions were imposed would be as much as 4%. However, if there were two policies, instead of just one: a counteracting labor market policy, as well as the emissions restrictions, the negative direct economic effects could be completely eliminated. 相似文献
82.
83.
84.
85.
The aim of this study was to determine whether there is increased leakage of neuron-specific enolase (NSE) and S-100 protein into amniotic fluid in pregnancies with neural tube defects, since both these proteins are produced by neural tissue, and to compare the value of these substances for detecting such defects with that of the more conventional techniques of alpha-fetoprotein (AFP) and acetylcholinesterase (AChE) gel electrophoresis. Amniotic samples from 25 mid-pregnancies (15–17 weeks' gestation) with neural tube defects (14 with open spina bifida and 11 with anencephaly) and from seven mid-pregnancies with abdominal wall defects were compared with a control material consisting of 80 amniotic fluid samples from 80 consecutive mid-pregnancy amniocenteses, with normal karyotypes and AFP concentrations. All of the above cases of abnormalities were primarily detected through increased AFP levels in the amniotic fluid. Amniotic fluid samples from 13 pregnancies with fetuses with autosomal chromosomal abnormalities and seven amniotic fluid samples contaminated with blood were also included in the investigation. It is concluded from the results that the conventional AFP assay combined with AChE gel electrophoresis is the best method for screening amniotic fluid for neural tube defects and defects of the abdominal wall. Neither NSE nor S-100 assay alone proved to be superior for the detection of these cases in mid-trimester amniotic fluid. The S-100 assay, however, could give additional information in cases where AChE gel electrophoresis is not decisive; for example, in samples contaminated with blood. 相似文献
86.
R.H. Field S. Benke K. Bdonyi R.B. Bradbury 《Agriculture, ecosystems & environment》2007,120(2-4):399-404
Bird use of conservation tillage-established (CT—seedbed preparation without soil inversion) crops was assessed at two adjacent sites in western Hungary, in comparison with conventionally established (mouldboard ploughed—P) fields. Bird abundance was assessed in a typical rotation of spring-sown maize and winter wheat in three consecutive winters. In the first winter, several species and the guild of seed-eating passerines were significantly more abundant on CT established plots, in both crop types. In the second winter, only starlings were more abundant on CT plots. In the third winter, only skylarks favoured CT over P plots. In combination with agri-environment scheme measures designed to provide resources for biodiversity, conservation tillage could play a role in softening the impact of agriculture on farmland birds in Hungary and elsewhere in Eastern Europe, in addition to its potential for reducing soil erosion and diffuse pollution. 相似文献
87.
Mitigation and Adaptation Strategies for Global Change - Guidelines of the Intergovernmental Panel on Climate Change (IPCC) were used to assess a greenhouse gas inventory for land use change and... 相似文献
88.
89.
90.
The most common mutation in alpha-1-antitrypsin deficiency, conversion of a G to an A at base 9989 (PI-Z), was detected with the chemical cleavage of mismatch method, demonstrating the power of the method for prenatal diagnosis. Exon V of the gene was amplified using the polymerase chain reaction and heteroduplexes were formed to test for the presence of the mutation. The predicted C mismatch was readily detectable with hydroxylamine, and by making the probe from the chorionic villus sample it was possible to determine that the fetus was heterozygous, not homozygous, for the mutation. 相似文献