全文获取类型
收费全文 | 34671篇 |
免费 | 428篇 |
国内免费 | 558篇 |
专业分类
安全科学 | 1095篇 |
废物处理 | 1577篇 |
环保管理 | 4704篇 |
综合类 | 5200篇 |
基础理论 | 8968篇 |
环境理论 | 11篇 |
污染及防治 | 9238篇 |
评价与监测 | 2418篇 |
社会与环境 | 2212篇 |
灾害及防治 | 234篇 |
出版年
2023年 | 172篇 |
2022年 | 349篇 |
2021年 | 356篇 |
2020年 | 302篇 |
2019年 | 306篇 |
2018年 | 564篇 |
2017年 | 552篇 |
2016年 | 864篇 |
2015年 | 635篇 |
2014年 | 924篇 |
2013年 | 2897篇 |
2012年 | 1188篇 |
2011年 | 1608篇 |
2010年 | 1353篇 |
2009年 | 1386篇 |
2008年 | 1557篇 |
2007年 | 1689篇 |
2006年 | 1456篇 |
2005年 | 1217篇 |
2004年 | 1192篇 |
2003年 | 1153篇 |
2002年 | 1087篇 |
2001年 | 1389篇 |
2000年 | 1026篇 |
1999年 | 654篇 |
1998年 | 447篇 |
1997年 | 435篇 |
1996年 | 476篇 |
1995年 | 488篇 |
1994年 | 428篇 |
1993年 | 407篇 |
1992年 | 377篇 |
1991年 | 365篇 |
1990年 | 362篇 |
1989年 | 363篇 |
1988年 | 323篇 |
1987年 | 272篇 |
1986年 | 257篇 |
1985年 | 260篇 |
1984年 | 339篇 |
1983年 | 285篇 |
1982年 | 343篇 |
1981年 | 271篇 |
1980年 | 230篇 |
1979年 | 282篇 |
1978年 | 202篇 |
1977年 | 189篇 |
1976年 | 167篇 |
1975年 | 165篇 |
1974年 | 166篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
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
162.
Kenneth L. Garver Miriam G. Blitzer Gladys Ibezim Sandra G. Marchese Dolores L. Pegram Anita M. Hagins Wnjing Zhang 《黑龙江环境通报》1984,4(2):109-112
Using a modified procedure by Solomons and Styner (1969), an evaluation of inorganic pyrophosphate (PPi) was performed on the amniotic fluid of two fetuses at risk for osteogenesis imperfecta (OI) at 14½ weeks gestation. The parents of both cases had a previous child with OI, Type II. The normal control group at 14–16 weeks gestation had PPi values ranging from 22.0–59.2 ug/100 ml, with a mean of 38.6±9.51 ug/100 ml. In each at-risk fetus, the amniotic fluid PPi value was within normal range. The first baby was born phenotypically normal at term. Intrauterine radiographic and fetal sonograms were done on the second fetus at approximately 19 weeks gestation. Both showed evidence of OI, Type II. The pregnancy was terminated at 21 weeks. Radiologic studies of the aborted fetus were consistent with OI, Type II. Our results indicate that the evaluation of PPi levels in amniotic fluid is not the method of choice for prenatal diagnosis of IO. 相似文献
163.
164.
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
165.
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
166.
167.
168.
169.
170.