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   407篇
  免费   63篇
  国内免费   3篇
  473篇
  2022年   5篇
  2021年   7篇
  2019年   4篇
  2018年   9篇
  2017年   6篇
  2016年   8篇
  2015年   15篇
  2014年   12篇
  2013年   15篇
  2012年   16篇
  2011年   17篇
  2010年   14篇
  2009年   9篇
  2008年   14篇
  2007年   12篇
  2006年   11篇
  2005年   6篇
  2004年   12篇
  2003年   10篇
  2002年   12篇
  2001年   11篇
  2000年   14篇
  1999年   12篇
  1998年   10篇
  1997年   15篇
  1996年   4篇
  1994年   3篇
  1993年   6篇
  1992年   8篇
  1991年   5篇
  1990年   10篇
  1989年   12篇
  1988年   18篇
  1987年   14篇
  1986年   8篇
  1985年   5篇
  1984年   8篇
  1983年   10篇
  1982年   3篇
  1980年   5篇
  1979年   7篇
  1977年   11篇
  1976年   4篇
  1974年   4篇
  1973年   10篇
  1972年   7篇
  1971年   5篇
  1970年   3篇
  1969年   3篇
  1968年   7篇
排序方式: 共有473条查询结果,搜索用时 0 毫秒
61.
In five and a half years 16 children were admitted to hospital in Nottingham suffering from malaria. Thirteen cases were caused by Plasmodium vivax and two by P falciparum, and in one the type was not identified. All were children of immigrant parents, predominantly from Pakistan, although most were born in England but had been visiting Asia. Three children were ill on or soon after arrival, but in the others the onset of symptoms was delayed by up to nine months. All made an uneventful recovery, although two children with P vivax infections had a further relapse after chloroquine treatment only. The question "Where have you been?" should be put to all immigrant parents whose children have a febrile illness. Agencies who provide travel for Asian immigrant families returning home for a visit should be encouraged to provide instructions about malaria prophylaxis.  相似文献   
62.
A high molecular weight glycoconjugate has been isolated from neurite-producing neuronal tumor cells in culture and has been designated as I(0) based on its elution characteristics in gel filtration chromatography. This molecule cannot be found in a variety of nonneuronal cells. I(0) is found in the substratum-attached material or cell fraction of neurite-producing neuroblastoma cells, depending upon culture conditions. It is found in the substratum-bound fraction of B104 rat neuroblastoma cells during serum starvation and in the EGTA-detached cell fraction of B104 cells grown in chemically defined N2 medium. It occurs only in the cell fraction of the human neuroblastoma line Platt. Examination of behavioral variants of the B104 rat line further strengthens the association of I(0) with neurite production; the constitutive neurite-producing E(R)B9 variant contains I(0) while the non-neurite-producing E(R)A11 variant does not. I(0) is large, eluting in the void volume of sepharose-CL2B columns. Radioiodination of intact cells with lactoperoxidase shows I(0) to be a cell surface component. Metabolic radiolabeling studies show that it contains a high proportion of polysaccharide to protein, does not contain mannose, and is unsulfated. Alkaline borohydride reduction release two size classes of large polysaccharide chain. The alkaline reduction results, along with the mannose incorporation studies, show the presence of O-glycosidic linkages and few, if any, N-linkages. Resistance to nitrous acid deamination, insensitivity to glycosaminoglycan lyases, and the absence of sulfation, indicate that I(0) does not contain the glycosaminoglycans hyaluronic acid, chondroitin-, dermatan-, or heparin- sulfates. Affinity column chromatography reveals high binding affinity of I(0) to polyornithine and no binding to gelatin (collagen) or the glycosaminoglycans hyaluronate and heparin. These studies describe a unique high molecular weight glycoconjugate on the surface of neurite-producing neuroblastoma cell lines from two species.  相似文献   
63.
马鹿茸血酶解肽体内免疫功能及抗氧化功能关系的研究   总被引:1,自引:0,他引:1  
本文分别选用由木瓜蛋白酶水解天山马鹿茸血获得的肽Ⅰ、肽Ⅱ以及原血为受试样品,研究天山马鹿茸血及其酶解肽对小鼠免疫功能和抗氧化功能的影响,其中肽Ⅰ、肽ⅡDH分别为18.1%、12.2%时,清除OH·能力最强,清除率为50.8%。分别测定了脏器指数,脾细胞增殖实验,血清中溶血素和抗体生成细胞的含量以及小鼠血清总抗氧化能力、SOD活力和MDA含量。结果表明:与对照组相比较,肽Ⅱ组能极显著提高小鼠体液和细胞免疫功能,加强小鼠的抗氧化功能(P〈0.01或P〈0.05)。此外,具有较强抗氧化活性的肽显示出了很强的免疫活性(P〈0.05)。  相似文献   
64.
65.
When compound I of chloroperoxidase is formed from the native enzyme the absorption peak in the Soret region diminishes in intensity, and shifts to a maximum absorbance at 367 nm. This unusual Soret spectrum decreases in intensity in a linear fashion as the wavelength increases. The first visible spectrum of chloroperoxidase compound I is reported which has a peak at 689 nm as its most prominent feature.  相似文献   
66.
We have developed a new approach to the measurement of phylogenetic signal in character state matrices called relative apparent synapomorphy analysis (RASA). RASA provides a deterministic, statistical measure of natural cladistic hierarchy (phylogenetic signal) in character state matrices. The method works by determining whether a measure of the rate of increase of cladistic similarity among pairs of taxa as a function of phenetic similarity is greater than a null equiprobable rate of increase. Our investigation of the utility and limitations of RASA using simulated and bacteriophage T7 data sets indicates that the method has numerous advantages over existing measures of signal. A first advantage is computational efficiency. A second advantage is that RASA employs known methods of statistical inference, providing measurable sensitivity and power. The performance of RASA is examined under various conditions of branching evolution as the number of characters, character states per character, and mutations per branch length are varied. RASA appears to provide an unbiased and reliable measure of phylogenetic signal, and the general approach promises to be useful in the development of new techniques that should increase the rigor and reliability of phylogenetic estimates.   相似文献   
67.
The subunit structure of mammalian fructose diphosphate aldolase   总被引:20,自引:0,他引:20  
  相似文献   
68.
Cardiac conduction disorders caused sudden serious illnesses in six infants that might have been fatal if diagnosis and treatment had been delayed. These cases provide circumstantial evidence to support a link between cardiac conduction disorders and some sudden infant deaths. A further potential long-term effect of these disorders is illustrated in one child in whom psychomotor retardation seemed to develop after an episode of cerebral hypoxia that was probably by an arrhythmia associated with the Wolff-Parkinson-White syndrome. Cardiac conduction disorders may be detected by routine neonatal ECG screening, and it may therefore be appropriate to start prophylactic antiarrhythmic treatment in certain children before clinical signs develop.  相似文献   
69.
70.
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