全文获取类型
收费全文 | 11077篇 |
免费 | 18篇 |
国内免费 | 35篇 |
专业分类
系统科学 | 41篇 |
丛书文集 | 205篇 |
教育与普及 | 39篇 |
理论与方法论 | 49篇 |
现状及发展 | 5168篇 |
研究方法 | 492篇 |
综合类 | 5005篇 |
自然研究 | 131篇 |
出版年
2013年 | 97篇 |
2012年 | 165篇 |
2011年 | 294篇 |
2010年 | 66篇 |
2008年 | 189篇 |
2007年 | 209篇 |
2006年 | 203篇 |
2005年 | 228篇 |
2004年 | 188篇 |
2003年 | 189篇 |
2002年 | 201篇 |
2001年 | 286篇 |
2000年 | 293篇 |
1999年 | 189篇 |
1992年 | 176篇 |
1991年 | 149篇 |
1990年 | 153篇 |
1989年 | 158篇 |
1988年 | 165篇 |
1987年 | 157篇 |
1986年 | 168篇 |
1985年 | 228篇 |
1984年 | 140篇 |
1983年 | 140篇 |
1982年 | 98篇 |
1981年 | 116篇 |
1980年 | 150篇 |
1979年 | 377篇 |
1978年 | 282篇 |
1977年 | 304篇 |
1976年 | 219篇 |
1975年 | 220篇 |
1974年 | 340篇 |
1973年 | 278篇 |
1972年 | 299篇 |
1971年 | 308篇 |
1970年 | 418篇 |
1969年 | 364篇 |
1968年 | 365篇 |
1967年 | 334篇 |
1966年 | 292篇 |
1965年 | 213篇 |
1964年 | 69篇 |
1959年 | 117篇 |
1958年 | 211篇 |
1957年 | 169篇 |
1956年 | 160篇 |
1955年 | 132篇 |
1954年 | 132篇 |
1948年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
881.
The synthesis and initial applications are reported for 1-[p-(palmitamido)-phenyl]ethylenedinitrilotetraacetic acid. The results demonstrate the versatility of this spectroscopic probe molecule, which allows choice of a particular technique for a particular system as well as use of multiple spectroscopic techniques for complementary information about hydrophobic regions in biological systems. 相似文献
882.
Nucleosome mobilization catalysed by the yeast SWI/SNF complex. 总被引:18,自引:0,他引:18
883.
Integrin cytoplasmic tyrosine motif is required for outside-in alphaIIbbeta3 signalling and platelet function. 总被引:23,自引:0,他引:23
D A Law F R DeGuzman P Heiser K Ministri-Madrid N Killeen D R Phillips 《Nature》1999,401(6755):808-811
Integrins not only bind adhesive ligands, they also act as signalling receptors. Both functions allow the integrin alphaIIbbeta3 to mediate platelet aggregation. Platelet agonists activate alphaIIbbeta3 (inside-out signalling) to allow the binding of soluble fibrinogen. Subsequent platelet aggregation leads to outside-in alphaIIbbeta3 signalling, which results in calcium mobilization, tyrosine phosphorylation of numerous proteins including beta3 itself, increased cytoskeletal reorganisation and further activation of alphaIIbbeta3. Thus, outside-in signals enhance aggregation, although the mechanisms and functional consequences of specific signalling events remain unclear. Here we describe a mouse that expresses an alphaIIbbeta3 in which the tyrosines in the integrin cytoplasmic tyrosine motif have been mutated to phenylalanines. These mice are selectively impaired in outside-in alphaIIbbeta3 signalling, with defective aggregation and clot-retraction responses in vitro, and an in vivo bleeding defect which is characterized by a pronounced tendency to rebleed. These data provide evidence for an important role of outside-in signalling in platelet physiology. Furthermore, they identify the integrin cytoplasmic tyrosine motif as a key mediator of beta-integrin signals and a potential target for new therapeutic agents. 相似文献
884.
Pitx2 regulates lung asymmetry, cardiac positioning and pituitary and tooth morphogenesis. 总被引:27,自引:0,他引:27
C R Lin C Kioussi S O'Connell P Briata D Szeto F Liu J C Izpisúa-Belmonte M G Rosenfeld 《Nature》1999,401(6750):279-282
885.
886.
Vivek S. Peche Tad A. Holak Bhagyashri D. Burgute Kosmas Kosmas Sushant P. Kale F. Thomas Wunderlich Fatiha Elhamine Robert Stehle Gabriele Pfitzer Klaus Nohroudi Klaus Addicks Florian Stöckigt Jan W. Schrickel Julia Gallinger Michael Schleicher Angelika A. Noegel 《Cellular and molecular life sciences : CMLS》2013,70(3):527-543
Cyclase-associated proteins are highly conserved proteins that have a role in the regulation of actin dynamics. Higher eukaryotes have two isoforms, CAP1 and CAP2. To study the in vivo function of CAP2, we generated mice in which the CAP2 gene was inactivated by a gene-trap approach. Mutant mice showed a decrease in body weight and had a decreased survival rate. Further, they developed a severe cardiac defect marked by dilated cardiomyopathy (DCM) associated with drastic reduction in basal heart rate and prolongations in atrial and ventricular conduction times. Moreover, CAP2-deficient myofibrils exhibited reduced cooperativity of calcium-regulated force development. At the microscopic level, we observed disarrayed sarcomeres with development of fibrosis. We analyzed CAP2’s role in actin assembly and found that it sequesters G-actin and efficiently fragments filaments. This activity resides completely in its WASP homology domain. Thus CAP2 is an essential component of the myocardial sarcomere and is essential for physiological functioning of the cardiac system, and a deficiency leads to DCM and various cardiac defects. 相似文献
887.
888.
Benjamin Förthmann Hella Brinkmann Andreas Ratzka Michal K. Stachowiak Claudia Grothe Peter Claus 《Cellular and molecular life sciences : CMLS》2013,70(14):2555-2568
Reduced levels of survival of motoneuron (SMN) protein lead to spinal muscular atrophy, but it is still unknown how SMN protects motoneurons in the spinal cord against degeneration. In the nucleus, SMN is associated with two types of nuclear bodies denoted as gems and Cajal bodies (CBs). The 23 kDa isoform of fibroblast growth factor-2 (FGF-223) is a nuclear protein that binds to SMN and destabilizes the SMN-Gemin2 complex. In the present study, we show that FGF-223 depletes SMN from CBs without affecting their general structure. FRAP analysis of SMN-EGFP in CBs demonstrated that the majority of SMN in CBs remained mobile and allowed quantification of fast, slow and immobile nuclear SMN populations. The potential for SMN release was confirmed by in vivo photoconversion of SMN-Dendra2, indicating that CBs concentrate immobile SMN that could have a specialized function in CBs. FGF-223 accelerated SMN release from CBs, accompanied by a conversion of immobile SMN into a mobile population. Furthermore, FGF-223 caused snRNP accumulation in CBs. We propose a model in which Cajal bodies store immobile SMN that can be mobilized by its nuclear interaction partner FGF-223, leading to U4 snRNP accumulation in CBs, indicating a role for immobile SMN in tri-snRNP assembly. 相似文献
889.
890.