全文获取类型
收费全文 | 25430篇 |
免费 | 335篇 |
国内免费 | 556篇 |
专业分类
系统科学 | 489篇 |
丛书文集 | 552篇 |
教育与普及 | 236篇 |
理论与方法论 | 101篇 |
现状及发展 | 7443篇 |
研究方法 | 921篇 |
综合类 | 16315篇 |
自然研究 | 264篇 |
出版年
2015年 | 271篇 |
2014年 | 379篇 |
2013年 | 462篇 |
2012年 | 679篇 |
2011年 | 929篇 |
2010年 | 546篇 |
2009年 | 540篇 |
2008年 | 789篇 |
2007年 | 846篇 |
2006年 | 776篇 |
2005年 | 721篇 |
2004年 | 659篇 |
2003年 | 595篇 |
2002年 | 735篇 |
2001年 | 1049篇 |
2000年 | 863篇 |
1999年 | 682篇 |
1998年 | 261篇 |
1997年 | 267篇 |
1996年 | 281篇 |
1995年 | 261篇 |
1993年 | 229篇 |
1992年 | 446篇 |
1991年 | 372篇 |
1990年 | 388篇 |
1989年 | 357篇 |
1988年 | 316篇 |
1987年 | 322篇 |
1986年 | 307篇 |
1985年 | 323篇 |
1984年 | 283篇 |
1983年 | 223篇 |
1980年 | 250篇 |
1979年 | 566篇 |
1978年 | 432篇 |
1977年 | 425篇 |
1976年 | 315篇 |
1975年 | 349篇 |
1974年 | 515篇 |
1973年 | 437篇 |
1972年 | 428篇 |
1971年 | 519篇 |
1970年 | 688篇 |
1969年 | 484篇 |
1968年 | 399篇 |
1967年 | 487篇 |
1966年 | 398篇 |
1965年 | 282篇 |
1958年 | 268篇 |
1957年 | 207篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
高等师范学校物理实验教学改革的研究与实践 总被引:1,自引:0,他引:1
物理实验是提高学生能力最主要的入门基础课 ,通过分析目前高等师范学校物理实验教学的现状 ,提出了进行物理实验教学改革的建议和设想 ,以及提高物理实验教学人员素质的重要性 . 相似文献
12.
新的、高密度树木种植正在给林业生物技术带来迅速的变化。但是如果不能克服生态风险和经济障碍.这些新的方法或许永远也无法使用—— 相似文献
13.
裴东林 《甘肃联合大学学报(自然科学版)》2002,16(2):16-19
文 [1 ]给出了非负函数无穷积分收敛性的几个判别法 ,本文给出了比文 [1 ]判别法更精细的一个判别法 ,同时 ,通过与文 [1 ]中判别法的比较 ,说明它比文 [1 ]中的判别法都强 . 相似文献
14.
15.
利用降价法研究了多孔介质中一维核废料污染问题,此模型由一非线性抛物-椭圆耦合偏微分方程组的初边值问题来描述,对此问题给出了一个关于时间和空间均具有二阶精度的差分格式,并进行了理论分析。 相似文献
16.
The Shwachman-Bodian-Diamond syndrome protein mediates translational activation of ribosomes in yeast 总被引:1,自引:0,他引:1
Menne TF Goyenechea B Sánchez-Puig N Wong CC Tonkin LM Ancliff PJ Brost RL Costanzo M Boone C Warren AJ 《Nature genetics》2007,39(4):486-495
The autosomal recessive disorder Shwachman-Diamond syndrome, characterized by bone marrow failure and leukemia predisposition, is caused by deficiency of the highly conserved Shwachman-Bodian-Diamond syndrome (SBDS) protein. Here, we identify the function of the yeast SBDS ortholog Sdo1, showing that it is critical for the release and recycling of the nucleolar shuttling factor Tif6 from pre-60S ribosomes, a key step in 60S maturation and translational activation of ribosomes. Using genome-wide synthetic genetic array mapping, we identified multiple TIF6 gain-of-function alleles that suppressed the pre-60S nuclear export defects and cytoplasmic mislocalization of Tif6 observed in sdo1Delta cells. Sdo1 appears to function within a pathway containing elongation factor-like 1, and together they control translational activation of ribosomes. Thus, our data link defective late 60S ribosomal subunit maturation to an inherited bone marrow failure syndrome associated with leukemia predisposition. 相似文献
17.
Romeo S Pennacchio LA Fu Y Boerwinkle E Tybjaerg-Hansen A Hobbs HH Cohen JC 《Nature genetics》2007,39(4):513-516
Resequencing genes provides the opportunity to assess the full spectrum of variants that influence complex traits. Here we report the first application of resequencing to a large population (n = 3,551) to examine the role of the adipokine ANGPTL4 in lipid metabolism. Nonsynonymous variants in ANGPTL4 were more prevalent in individuals with triglyceride levels in the lowest quartile than in individuals with levels in the highest quartile (P = 0.016). One variant (E40K), present in approximately 3% of European Americans, was associated with significantly lower plasma levels of triglyceride and higher levels of high-density lipoprotein cholesterol in European Americans from the Atherosclerosis Risk in Communities Study and in Danes from the Copenhagen City Heart Study. The ratio of nonsynonymous to synonymous variants was higher in European Americans than in African Americans (4:1 versus 1.3:1), suggesting population-specific relaxation of purifying selection. Thus, resequencing of ANGPTL4 in a multiethnic population allowed analysis of the phenotypic effects of both rare and common variants while taking advantage of genetic variation arising from ethnic differences in population history. 相似文献
18.
19.
20.
Komen JC Distelmaier F Koopman WJ Wanders RJ Smeitink J Willems PH 《Cellular and molecular life sciences : CMLS》2007,64(24):3271-3281
Refsum disease is a rare, inherited neurodegenerative disorder characterized by accumulation of the dietary branched-chain
fatty acid phytanic acid in plasma and tissues caused by a defect in the alphaoxidation pathway. The accumulation of phytanic
acid is believed to be the main pathophysiological cause of the disease. However, the exact mechanism(s) by which phytanic
acid exerts its toxicity have not been resolved. In this study, the effect of phytanic acid on mitochondrial respiration was
investigated. The results show that in digitonin-permeabilized fibroblasts, phytanic acid decreases ATP synthesis, whereas
substrate oxidation per se is not affected. Importantly, studies in intact fibroblasts revealed that phytanic acid decreases both the mitochondrial
membrane potential and NAD(P)H autofluorescence. Taken together, the results described here show that unesterified phytanic
acid exerts its toxic effect mainly through its protonophoric action, at least in human skin fibroblasts.
Received 4 August 2007; received after revision 26 September 2007; accepted 10 October 2007
J. C. Komen, F. Distelmaier: These authors contributed equally to this work. 相似文献