全文获取类型
收费全文 | 14043篇 |
免费 | 1411篇 |
国内免费 | 2846篇 |
出版年
2024年 | 38篇 |
2023年 | 257篇 |
2022年 | 383篇 |
2021年 | 876篇 |
2020年 | 633篇 |
2019年 | 746篇 |
2018年 | 641篇 |
2017年 | 511篇 |
2016年 | 645篇 |
2015年 | 941篇 |
2014年 | 1183篇 |
2013年 | 1117篇 |
2012年 | 1342篇 |
2011年 | 1299篇 |
2010年 | 795篇 |
2009年 | 763篇 |
2008年 | 879篇 |
2007年 | 762篇 |
2006年 | 623篇 |
2005年 | 525篇 |
2004年 | 475篇 |
2003年 | 397篇 |
2002年 | 373篇 |
2001年 | 284篇 |
2000年 | 289篇 |
1999年 | 228篇 |
1998年 | 137篇 |
1997年 | 120篇 |
1996年 | 125篇 |
1995年 | 93篇 |
1994年 | 94篇 |
1993年 | 65篇 |
1992年 | 78篇 |
1991年 | 84篇 |
1990年 | 60篇 |
1989年 | 42篇 |
1988年 | 52篇 |
1987年 | 28篇 |
1986年 | 39篇 |
1985年 | 42篇 |
1984年 | 27篇 |
1983年 | 29篇 |
1982年 | 23篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1975年 | 13篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1970年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
981.
ErbB2 is essential in the prevention of dilated cardiomyopathy 总被引:22,自引:0,他引:22
Crone SA Zhao YY Fan L Gu Y Minamisawa S Liu Y Peterson KL Chen J Kahn R Condorelli G Ross J Chien KR Lee KF 《Nature medicine》2002,8(5):459-465
Amplification of the gene encoding the ErbB2 (Her2/neu) receptor tyrosine kinase is critical for the progression of several forms of breast cancer. In a large-scale clinical trial, treatment with Herceptin (trastuzumab), a humanized blocking antibody against ErbB2, led to marked improvement in survival. However, cardiomyopathy was uncovered as a mitigating side effect, thereby suggesting an important role for ErbB2 signaling as a modifier of human heart failure. To investigate the physiological role of ErbB2 signaling in the adult heart, we generated mice with a ventricular-restricted deletion of Erbb2. These ErbB2-deficient conditional mutant mice were viable and displayed no overt phenotype. However, physiological analysis revealed the onset of multiple independent parameters of dilated cardiomyopathy, including chamber dilation, wall thinning and decreased contractility. Additionally, cardiomyocytes isolated from these conditional mutants were more susceptible to anthracycline toxicity. ErbB2 signaling in cardiomyocytes is therefore essential for the prevention of dilated cardiomyopathy. 相似文献
982.
The present work describes a complete probe design software system for oligonucleotide microarrays based on Kane's research on probe sensitivity and specificity (Kane's rule). Combining Kane's rule and traditional criteria for probe design we constructed MProbe, the software system for oligonucleotide microarrays using Java. The general criteria for probe design are: (1) probes may have different lengths that range from 20 to 100 bases; (2) they should have a similar melting temperature (Tm) or GC content; (3) they should not contain stable secondary structures; and (4) they abide by Kane's rule. 相似文献
983.
Nakamura H Kouda K Fan W Takeuchi H 《Journal of PHYSIOLOGICAL ANTHROPOLOGY and Applied Human Science》2002,21(5):223-227
Previous studies have shown that mortality from cardiovascular diseases in fishing villages was lower than that in farming villages. In contrast, few reports on the population living in a tourist village have appeared. Then, we report here the characteristic features of a tourist town, and that in fishing and farming towns. The rural farming town in Gunma prefecture had a population of 15,100. The population working in the primary industry was 17.1%, and the farming population was 17.0%. The fishing town in Shizuoka prefecture had a population of 11,700. The population working in the primary industry was 11.0%, and the fishing population was 10.2%. The rural tourist town in Shizuoka prefecture had a population of 17,800. The population working in the tertiary industry was 60.2%, and the wholesaling or retailing population was 16.6%. Standardized mortality ratios of cardiovascular diseases in the tourist town reported by Shizuoka health officials were higher than the fishing town. The rate of participation at ages of 50-59 years for the basic health examination in the tourist town was lower than the fishing and the farming towns. From the results of the health examination of residents at ages of 50-59 years, the high prevalence of obesity and hypertension in men and high prevalence of hypertension in women were found in the tourist town. In the tourist town, self-employed women at ages of 50-59 years had irregular time of meals and insufficient care of diet in comparison with employed women. Furthermore, the prevalence of hypertension in self-employed women was also higher than that of employed women. We could suggest that health status in communities might be associated with job-related factors. 相似文献
984.
Evolutionary dynamics and population control during in vitro selection and amplification with multiple targets 下载免费PDF全文
Iterative cycles of in vitro selection and amplification allow rare functional nucleic acid molecules, aptamers, to be isolated from large sequence pools. Here we present an analysis of the progression of a selection experiment that simultaneously yielded two families of RNA aptamers against two disparate targets: the intended target protein (B52/SRp55) and the partitioning matrix. We tracked the sequence abundance and binding activity to reveal the enrichment of the aptamers through successive generations of selected pools. The two aptamer families showed distinct trajectories of evolution, as did members within a single family. We also developed a method to control the relative abundance of an aptamer family in selected pools. This method, involving specific ribonuclease digestion, can be used to reduce the background selection for aptamers that bind the matrix. Additionally, it can be used to isolate a full spectrum of aptamers in a sequential and exhaustive manner for all the different targets in a mixture. 相似文献
985.
黄芩甙对发热大鼠下丘脑PGE2和cAMP含量的影响 总被引:18,自引:0,他引:18
目的和方法:PGE2和cAMP是重要的中枢发热介质。为了探讨PGE2和cAMP是否参与了黄芩甙解热的机制,本实验用内毒素(ET)复制大鼠发热模型,观察黄芩甙的解热作用及对大鼠下丘脑中PGE2和cAMP含量的影响。结果:黄芩甙有明显的解热作用,并且翻转ET对下丘脑中PGE2和cAMP含量的影响。相关分析显示,下丘脑中PGE2和cAMP含量的变化与体温变化之间存在明显正相关。结论:黄芩甙可通过抑制下丘脑中PGE2和cAMP含量升高而发挥其解热作用。 相似文献
986.
987.
988.
989.
Nitrate uptake,nitrate reductase distribution and their relation to proton release in five nodulated grain legumes 总被引:4,自引:0,他引:4
Nitrate uptake, nitrate reductase activity (NRA) and net proton release were compared in five grain legumes grown at 0.2 and 2 mM nitrate in nutrient solution. Nitrate treatments, imposed on 22-d-old, fully nodulated plants, lasted for 21 d. Increasing nitrate supply did not significantly influence the growth of any of the species during the treatment, but yellow lupin (Lupinus luteus) had a higher growth rate than the other species examined. At 0.2 mM nitrate supply, nitrate uptake rates ranged from 0.6 to 1.5 mg N g(-1) d(-1) in the order: yellow lupin > field pea (Pisum sativum) > chickpea (Cicer arietinum) > narrow-leafed lupin (L angustifolius) > white lupin (L albus). At 2 mM nitrate supply, nitrate uptake ranged from 1.7 to 8.2 mg N g(-1) d(-1) in the order: field pea > chickpea > white lupin > yellow lupin > narrow-leafed lupin. Nitrate reductase activity increased with increased nitrate supply, with the majority of NRA being present in shoots. Field pea and chickpea had much higher shoot NRA than the three lupin species. When 0.2 mM nitrate was supplied, narrow-leafed lupinreleased the most H+ per unit root biomass per day, followed by yellow lupin, white lupin, field pea and chickpea. At 2 mM nitrate, narrow-leafed lupin and yellow lupin showed net proton release, whereas the other species, especially field pea, showed net OH- release. Irrespective of legume species and nitrate supply, proton release was negatively correlated with nitrate uptake and NRA in shoots, but not with NRA in roots. 相似文献
990.