全文获取类型
收费全文 | 501篇 |
免费 | 3篇 |
国内免费 | 10篇 |
专业分类
系统科学 | 6篇 |
教育与普及 | 1篇 |
理论与方法论 | 8篇 |
现状及发展 | 112篇 |
研究方法 | 66篇 |
综合类 | 317篇 |
自然研究 | 4篇 |
出版年
2021年 | 7篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 41篇 |
2011年 | 60篇 |
2010年 | 20篇 |
2009年 | 5篇 |
2008年 | 35篇 |
2007年 | 40篇 |
2006年 | 28篇 |
2005年 | 36篇 |
2004年 | 23篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1972年 | 5篇 |
1971年 | 2篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 2篇 |
1966年 | 5篇 |
1964年 | 2篇 |
1945年 | 1篇 |
排序方式: 共有514条查询结果,搜索用时 545 毫秒
331.
Alexander v. Muralt 《Cellular and molecular life sciences : CMLS》1945,1(5):136-146
Ohne ZusammenfassungNach einem Vortrag vor der Chemischen Gesellschaft Zürich, 2. Juli 1945. 相似文献
332.
Steven H. Back Naga Suresh Adapala Mary F. Barbe Nick C. Carpino Alexander Y. Tsygankov Archana Sanjay 《Cellular and molecular life sciences : CMLS》2013,70(7):1269-1284
Bone is a dynamic tissue that depends on the intricate relationship between protein tyrosine kinases (PTK) and protein tyrosine phosphatases (PTP) for maintaining homeostasis. PTKs and PTPs act like molecular on and off switches and help modulate differentiation and the attachment of osteoclasts to bone matrix regulating bone resorption. The protein T cell ubiquitin ligand-2 (TULA-2), which is abundantly expressed in osteoclasts, is a novel histidine phosphatase. Our results show that of the two family members, only TULA-2 is expressed in osteoclasts and that its expression is sustained throughout the course of osteoclast differentiation, suggesting that TULA-2 may play a role during early as well late stages of osteoclast differentiation. Skeletal analysis of mice that do not express TULA or TULA-2 proteins (DKO mice) revealed that there was a decrease in bone volume due to increased osteoclast numbers and function. Furthermore, in vitro experiments indicated that bone marrow precursor cells from DKO mice have an increased potential to form osteoclasts. At the molecular level, the absence of TULA-2 in osteoclasts results in increased Syk phosphorylation at the Y352 and Y525/526 residues and activation of phospholipase C gamma 2 (PLCγ2) upon engagement of immune-receptor-tyrosine-based-activation-motif (ITAM)—mediated signaling. Furthermore, expression of a phosphatase-dead TULA-2 leads to increased osteoclast function. Taken together, these results suggest that TULA-2 negatively regulates osteoclast differentiation and function. 相似文献
333.
Alexander Y. Tsygankov 《Cellular and molecular life sciences : CMLS》2009,66(17):2949-2952
Two members of the TULA family (TULA/STS-2/UBASH3A and TULA-2/STS-1/UBASH3B) recently emerged as novel regulators of several
cellular functions. The degree of structural similarity between the TULA-family proteins is typical for proteins that belong
to the same family. Furthermore, the experiments with knockout mice lacking these proteins may be interpreted as suggesting
that functions of TULA-family proteins in T lymphocytes overlap. At the same time, TULA and TULA-2 exhibit clear functional
dissimilarities, starting with the finding that a conserved phosphatase domain present in both proteins exhibits remarkable
differences in enzymatic activity; TULA-2 is an active phosphatase capable of dephosphorylating multiple tyrosine-phosphorylated
proteins, whereas the phosphatase activity of TULA is extremely low. In contrast, TULA, but not TULA-2, facilitates growth
factor withdrawal-induced apoptosis in T cells. In spite of their apparent importance, the functional role of TULA-family
proteins is not well understood. In particular, the role of functional dissimilarities between them remains unclear. 相似文献
334.
Alexander Afriat Ermenegildo Caccese 《Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics》2010,41(1):9-26
We first see that the inertia of Newtonian mechanics is absolute and troublesome. General relativity can be viewed as Einstein's attempt to remedy, by making inertia relative, to matter—perhaps imperfectly though, as at least a couple of freedom degrees separate inertia from matter in his theory. We consider ways the relationist (for whom it is of course unwelcome) can try to overcome such underdetermination, dismissing it as physically meaningless, especially by insisting on the right transformation properties. 相似文献
335.
336.
Sabine Gilch Christian Bach Gloria Lutzny Ina Vorberg Hermann M. Schätzl 《Cellular and molecular life sciences : CMLS》2009,66(24):3979-3991
The infectious agent in prion diseases consists of an aberrantly folded isoform of the cellular prion protein (PrPc), termed PrPSc, which accumulates in brains of affected individuals. Studies on prion-infected cultured cells indicate that cellular cholesterol
homeostasis influences PrPSc propagation. Here, we demonstrate that the cellular PrPSc content decreases upon accumulation of cholesterol in late endosomes, as induced by NPC-1 knock-down or treatment with U18666A.
PrPc trafficking, lipid raft association, and membrane turnover are not significantly altered by such treatments. Cellular PrPSc formation is not impaired, suggesting that PrPSc degradation is increased by intracellular cholesterol accumulation. Interestingly, PrPSc propagation in U18666A-treated cells was partially restored by overexpression of rab 9, which causes redistribution of cholesterol
and possibly of PrPSc to the trans-Golgi network. Surprisingly, rab 9 overexpression itself reduced cellular PrPSc content, indicating that PrPSc production is highly sensitive to alterations in dynamics of vesicle trafficking. 相似文献
337.
H Alexander D A Johnson J Rosen L Jerabek N Green I L Weissman R A Lerner 《Nature》1983,306(5944):697-699
Recent studies have shown that short chemically synthesized peptides very often induce antibodies which react with the cognate sequence in the intact folded protein. Since such antibodies react with known regions of proteins, they are of predetermined specificity and offer a precision not previously possible with immunological probes. A basic concept emerging from the use of such antibodies in viral systems is that the differential immunogenicity of closely related proteins can be mimicked by short peptides which span the regions of sequence variation. To generalize this concept, we have studied the two Thy-1 proteins which vary by only a single amino acid. Chemically synthesized peptides differing in only one out of 19 amino acids were able to induce allospecific antisera. Thus, single amino acid changes have similar effects on the immunogenicity of proteins and small peptides, even though the latter are free from constraints provided by neighbouring structures in the tertiary configuration of the intact folded proteins. 相似文献
338.
考虑粉粒体积分率对气粉两相流的影响建立了收缩-扩张喷嘴中气粉流的数学模型,这一模型由九个未知量U_p,T_p,U-g,T_g,α,P,ρ_g,M和A的一阶常微分方程组,以及相应的入口边界条件所构成。数值计算表明,在亚声速区中粉粒速度和气体速度的变化与粉气比无关,在超声速区中粉粒速度和气体速度均随粉气比的增大而减小;粉粒终速随粉粒粒径的减小而增大。 相似文献
339.
340.
Zusammenfassung Die Röntgenbestrahlung des Kopfes junger Ratten verursacht eine vermehrte DNS-Synthese im Thymus, was mit der Freisetzung von Wachstumshormon-ähnlichen Substanzen in Zusammenhang gebracht wird.
Acknowledgment. This project was supported in part by a grant from the Israel Cancer Association. 相似文献
Acknowledgment. This project was supported in part by a grant from the Israel Cancer Association. 相似文献