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   1421篇
  免费   63篇
  国内免费   1篇
  2022年   7篇
  2018年   14篇
  2017年   17篇
  2016年   22篇
  2015年   24篇
  2014年   43篇
  2013年   59篇
  2012年   73篇
  2011年   76篇
  2010年   54篇
  2009年   34篇
  2008年   77篇
  2007年   73篇
  2006年   80篇
  2005年   59篇
  2004年   83篇
  2003年   54篇
  2002年   70篇
  2001年   36篇
  2000年   32篇
  1999年   13篇
  1998年   20篇
  1997年   16篇
  1996年   19篇
  1995年   8篇
  1994年   15篇
  1993年   8篇
  1992年   15篇
  1991年   9篇
  1990年   11篇
  1989年   8篇
  1988年   18篇
  1987年   17篇
  1986年   7篇
  1985年   12篇
  1984年   21篇
  1983年   21篇
  1982年   16篇
  1981年   28篇
  1980年   24篇
  1979年   12篇
  1978年   28篇
  1977年   15篇
  1976年   21篇
  1975年   17篇
  1974年   14篇
  1973年   9篇
  1971年   6篇
  1968年   8篇
  1964年   8篇
排序方式: 共有1485条查询结果,搜索用时 328 毫秒
31.
Soil microfungi in three Swedish coniferous forests   总被引:4,自引:0,他引:4  
Microfungi were isolated with the soil washing technique from five different soil horizons in three podzolic coniferous forests in Sweden. Totally 126 species were identified of which 45 were found at two and 24 were found at three sites. The most common genera were Mortierella and Penicillium . Other genera isolated in high frequences were Oidiodendron, Tolypocladium, Trichoderma and Verticillium . Pronounced differences in species composition were found between the soil layers, while great similarities were shown in identical soil layers at different sites.  相似文献   
32.
Leukotriene A: stereochemistry and enzymatic conversion to leukotriene B   总被引:13,自引:0,他引:13  
Leukotriene A was assigned the structure 5(S)-trans-5,6-oxido-7,9-trans-11,14-cis-eicosatetraenoic acid by the enzymatic conversion of a synthetic product of known stereochemistry into the naturally occurring isomer of 5(S),12(R)-dihydroxy-6,8,10,14-eicosatetraenoic acid in human polymorphonuclear leukocytes.  相似文献   
33.
A slow reacting substance, produced by murine mastocytoma cells, has been shown to have the structure 5(S)-hydroxy-6(R)-S-glutathionyl-7,9,11-trans-14-cis-eicosatetraenoic acid (11-trans leukotriene C, previously referred to as leukotriene C-2) by ultraviolet spectroscopy, amino acid analyses, lipoxygenase conversion and comparisions with a synthetic compound of known structure and stereochemistry.  相似文献   
34.
Slow reacting substance (SRS), produced by rat peritoneal mononuclear cells after stimulation with ionophore A23187, consists of two main components (Bach, M.K. et al. (1979) J. Immunol. 122, 160–165). One of these components was recently identified as leukotriene C-1. The other component has now been identified as leukotriene D.  相似文献   
35.
36.
37.
Plasma levels of prolactin and FSH in free-living Pied flycatchers were studied in relation to breeding stage, clutch size and diurnal variations. In the female, the concentration of prolactin started to increase during the egg-laying and reached maximal values at the end of the incubation period. After hatching prolactin levels decreased. Male Pied flycatchers showed an increase in plasma levels of prolactin at the time when they returned to their home-territories, i.e. at the end of the incubation period. Males still occupying secondary territories at this time had low levels of prolactin. In the males, as in the females, plasma levels of prolactin decreased after hatching.
Male Pied flycatchers showed at all times higher plasma levels of FSH than did females. In both sexes FSH levels were high during the early part of the breeding season and started to decrease after the egg-laying period. After hatching time plasma levels of FSH were below the sensitivity of the assay. No differences in FSH were found between males occupying secondary territories and males in home-territories.
In incubating females FSH, but not prolactin, showed a distinct unimodal daily cycle.
No differences were found in plasma levels of prolactin and FSH between females incubating different sized clutches.  相似文献   
38.
Gene fusion vectors based on the gene for staphylococcal protein A   总被引:1,自引:0,他引:1  
Two plasmid vectors, containing the gene coding for staphylococcal protein A and adapted for gene fusion, have been constructed. These vectors will allow fusion of any gene to the protein A gene, thus giving hybrid proteins which can be purified, in a one-step procedure, by IgG affinity chromatography. As an example of the practical use of such vectors, the protein A gene has been fused to the lacZ gene of Escherichia coli. E. coli strains containing such plasmids produce hybrid proteins with both IgG binding and β-galactosidase activities. The hybrid protein(s) can be immobilized on IgG-Sepharose by its protein A moiety with high efficiency without losing its enzymatic activity and they can be eluted from the column by competitive elution with pure protein A. The fused protein(s) also binds to IgG-coated microtiter wells which means that the in vivo product can be used as an enzyme conjugate in ELISA tests.  相似文献   
39.
A method of analyzing facial proportions in evaluating occlusal vertical dimension was used in a test on 71 complete denture wearers aiming to find a way to rank denture wearers with different stages of reduced vertical dimension and development an instruction for patients' self judgment. By use of face drawings on a proforma the patients ranked themselves into one of four classes. The investigator also ranked the patients into these classes. There was a significant correlation (p<0.01) between the ranking by patient and investigator. The face proportions were also measured with an instrument. The distances nasion-rima oris and subnasale-gnathion were established. When ranking into classes, there was a significant (p<0.0001) correlation between the ranking by the investigator and the measurements. The results show that it may be possible to use information of facial proportions to give complete denture wearers a way of assessment of face height and thus a reason to consult a dentist in case of suspicion of reduced vertical dimension.  相似文献   
40.
Phosphoserine peptides, obtained by phosphorylation of synthetic precursors with cyclic AMP-dependent protein kinase, can be efficiently separated from the corresponding non-phosphorylated peptides and from each other by ion-pair high-performance liquid chromatography. All experiments were performed under isocratic conditions on a C18 column, using phosphate buffers with pH 3.2–4.5, n-hexane sulfonic acid as counter ion, and ethanol as organic modifier.  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