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   331篇
  免费   36篇
  国内免费   29篇
  2022年   3篇
  2021年   3篇
  2020年   6篇
  2019年   4篇
  2018年   9篇
  2017年   6篇
  2016年   8篇
  2015年   6篇
  2014年   9篇
  2013年   12篇
  2012年   17篇
  2011年   22篇
  2010年   18篇
  2009年   17篇
  2008年   16篇
  2007年   11篇
  2006年   25篇
  2005年   14篇
  2004年   13篇
  2003年   9篇
  2002年   10篇
  2001年   16篇
  2000年   3篇
  1999年   7篇
  1998年   13篇
  1997年   9篇
  1996年   6篇
  1995年   4篇
  1994年   7篇
  1992年   10篇
  1990年   3篇
  1989年   6篇
  1988年   5篇
  1987年   5篇
  1985年   2篇
  1983年   3篇
  1982年   3篇
  1981年   5篇
  1980年   6篇
  1978年   2篇
  1977年   5篇
  1974年   2篇
  1971年   2篇
  1963年   2篇
  1959年   2篇
  1958年   3篇
  1957年   2篇
  1955年   3篇
  1949年   5篇
  1948年   2篇
排序方式: 共有396条查询结果,搜索用时 515 毫秒
1.
On the basis of the results of clinicoroentgenological and tensographic investigations of 119 patients after traumas of the crural bones and ankle joint (2-36 yrs. ago) the authors showed the importance of roentgenofunctional investigation of the ankle joint, a patient being in a standing position with maximum flexion and extension of the foot. A specially designed footing was proposed. Of 77 patients after intra-articular fractures of the ankle bones various disorders in articular proportions, undetectable on routine roentgenography, were diagnosed in 29 by functional roentgenography. Articular changes on roentgenofunctional investigation were revealed in one patient only out of 42 patients with extra-articular fractures of the crural bones. Tensography showed disorders of foot biomechanics in all patients with subluxations in the ankle.  相似文献   
2.
Studies have been made on a possibility of inducing a prolonged hypothermia by injections to albino mice of a fraction with a molecular mass 1-10 KD isolated from the small intestine of hibernating ground squirrels. Specific conditions for the onset of hibernation (hypoxia, hypercapnia, temperature) were simulated. Exposure of mice to hypoxia and hypercapnia for 2 hours in combination with injection of the mentioned fraction extended hypothermic condition in animals up to 24-36 hours as compared to 2-3 hours after sole injection of the fraction. After the injection of 5-OT under the same conditions, the prolonged hypothermia was less stable.  相似文献   
3.
Nuclear DNA was extracted from each of the eight species comprising the Drosophila melanogaster species subgroup. Southern hybridization of this DNA by using a molecular probe specific for the alpha-amylase coding region showed that the duplicated structure of the amylase locus, first found in D. melanogaster, is conserved among all species of the melanogaster subgroup. Evidence is also presented for the concerted evolution of the duplicated genes within each species. In addition, it is shown that the glucose repression of amylase gene expression, which has been extensively studied in D. melanogaster, is not confined to this species but occurs in all eight members of the species subgroup. Thus, both the duplicated gene structure and the glucose repression of Drosophila amylase gene activity are stable over extended periods of evolutionary time.   相似文献   
4.
From tissues of hibernating and active long-tailed ground squirrels and from the brain of cold-adapted Yakut horses, low molecular peptide fractions were obtained which, after injection to albino mice, decreased oxygen consumption and rectal temperature in them. The same fractions exhibited negative chrono- and inotropic effects on isolated hearts of ectothermic and endothermic animals. Fractions from the brain of ground squirrels and the brain of horse exhibited similar pattern of the activity. The activity of fractions was subjected to seasonal changes and depended on the degree of their purification. Provisional intracellular microelectrophysiological analysis of the effect of these fractions on the frequency and strength of contractions in isolated heart was made.  相似文献   
5.
ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.  相似文献   
6.
ABSTRACT. Proteins of the membrane skeleton of Euglena gracilis were extensively phosphorylated in vivo and in vitro after incubation with [32P]-orthophosphate or γ-[32P] ATP. Endogenous protein threonine/serine activity phosphorylated the major membrane skeletal proteins (articulins) and the putative integral membrane protein (IP39) anchor for articulins. The latter was also the major target for endogenous protein tyrosine kinase activity. A cytoplasmic domain of IP39 was specifically phosphorylated, and removal of this domain with papain eliminated the radiolabeled phosphoamino acids and eliminated or radically shifted the PI of the multiple isoforms of IP39. In gel kinase assays IP39 autophosphorylated and a 25 kDa protein which does not autophosphorylate was identified as a threonine/serine (casein) kinase. Plasma membranes from the membrane skeletal protein complex contained threonine/serine (casein) kinase activity, and cross-linking experiments suggested that IP39 was the likely source for this membrane activity. pH optima, cation requirements and heparin sensitivity of the detergent solubilized membrane activity were determined. Together these results suggest that protein kinases may be important modulators of protein assembly and function of the membrane skeleton of these protistan cells.  相似文献   
7.
Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.   相似文献   
8.
Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations.  相似文献   
9.
10.
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