首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   18781篇
  免费   208篇
  国内免费   158篇
安全科学   553篇
废物处理   773篇
环保管理   2678篇
综合类   2844篇
基础理论   5083篇
环境理论   11篇
污染及防治   4746篇
评价与监测   1256篇
社会与环境   1084篇
灾害及防治   119篇
  2022年   147篇
  2021年   127篇
  2020年   124篇
  2019年   139篇
  2018年   234篇
  2017年   295篇
  2016年   400篇
  2015年   327篇
  2014年   519篇
  2013年   1614篇
  2012年   610篇
  2011年   846篇
  2010年   717篇
  2009年   702篇
  2008年   821篇
  2007年   891篇
  2006年   708篇
  2005年   623篇
  2004年   638篇
  2003年   622篇
  2002年   588篇
  2001年   706篇
  2000年   547篇
  1999年   300篇
  1998年   221篇
  1997年   249篇
  1996年   261篇
  1995年   290篇
  1994年   294篇
  1993年   230篇
  1992年   239篇
  1991年   217篇
  1990年   238篇
  1989年   214篇
  1988年   188篇
  1987年   189篇
  1986年   184篇
  1985年   187篇
  1984年   174篇
  1983年   175篇
  1982年   170篇
  1981年   162篇
  1980年   139篇
  1979年   150篇
  1978年   123篇
  1977年   138篇
  1975年   95篇
  1974年   97篇
  1973年   101篇
  1972年   97篇
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
361.
A 46,XX; 47,XX,+9; 47,XX, + ?mar karyotype was detected in an amniotic fluid cell culture and confirmed in a subsequent fetal blood sample from a 40-year-old woman. After termination of the pregnancy, none of the 186 mitoses obtained from a second blood sample was trisomic for chromosome 9 (p<0.001). Selection against cells containing trisomy 9 is postulated to explain the disappearance of the lymphocyte clone.  相似文献   
362.
363.
364.
365.
366.
In this paper we describe the use of five-colour fluorescence in situ hybridization for prenatal diagnosis of aneuploidy using uncultured amniotic fluid cells. The analysis is based on ratio mixing of dual-labelled probes and digital imaging for the detection and visualization of five different probes specific for the five target chromosomes, 13, 18, 21, X, and Y. A retrospective blind analysis of 30 coded uncultured amniotic fluid samples correctly detected fetal sex and five trisomy 21 cases. Multicolour fluorescence in situ hybridization used in this way allows rapid and simultaneous detection of the most frequent aneuploidies.  相似文献   
367.
The histochemical measurement of urea-resistant alkaline phosphatase from maternal blood neutrophils is known to have a high detection rate for the prenatal detection of Down's syndrome pregnancies. However, because the histochemical method is laborious and subjective to use, it has not gained widespread acceptance in prenatal screening programmes. We present a simple and objective method for the measurement of urea-resistant alkaline phosphatase by flow cytometry. The method should allow the design of larger studies aimed at evaluating the role of neutrophil urea-resistant alkaline phosphatase in the prenatal screening for Down's syndrome.  相似文献   
368.
Ultrasound examination at 12 weeks' gestation revealed severe generalised subcutaneous oedema in a pregnancy at risk for achondrogenesis type II. Transvaginal scanning confirmed the oedema and suggested abnormal limb development. The prenatal diagnosis was confirmed by X-ray examination after transvaginal termination.  相似文献   
369.
The efficacy of the insulin infusion pump (CSII) in pregnancy was examined in 12 diabetic patients and compared with intermittent insulin therapy (IIT). In patients poorly controlled on IIT constant and rapid equilibrium was achieved with CSII (mean of glucose levels: CSII versus IIT=84 versus 137 mg/dl; S.D. = 36 versus 63 mg/dl; mean amplitude of glycemic excursion (MAGE)=65 versus 112 mg/dl. In patients well controlled on IIT, CSII led to a reduction in the variation of glucose excursions (S.D.= 29 versus 36 mg/dl; MAGE=48 versus 76 mg/dl). CSII generally produced a reduction of 20–37 per cent of daily insulin dose (in three cases there was an increase of dose with the achievement of glycemic control). Furthermore in CSII treated-patients amniotic glucose, insulin and C-peptide concentrations werefound tobeinthenormalrange(22.1±10.1 mg/dl; 5.2±2.7μ/ml; 1.25±0.71 ng/ml, respectively). All infants were horn at or near-term, had no macrosomia or neonatal problems. It is concluded that CSII is a highly efficient way to achieve normal glucose levels in pregnancy, not only in type I, hut also in type II or gestational diabetes.  相似文献   
370.
The electric organ of Torpedo, besides providing abundant amounts of cholinoceptive post-synaptic membrane for the isolation of the acetylcholine receptor protein, is a rich source of cholinergic nerve terminals. Using perfused, innervated tissue blocks from which synaptic vesicles in different functional states can be isolated, much information can be obtained about synaptic-vesicle dynamics. So far this is consistent with the view that the synaptic vesicles are the source of transmitter released on stimulation and that uptake of newly synthesized transmitter by the vesicles is dependent on their having discharged their previous charge of transmitter in at least one cycle of exo- and endocytosis. Studies of the protein composition of the vesicle membrane, especially when combined with similar information about the external presynaptic membrane, purified samples of which are now available from synaptosome (T-sac) preparations, promise to throw new light on the molecular mechanism underlying vesicle exo-/endocytosis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号