全文获取类型
收费全文 | 1061篇 |
免费 | 15篇 |
国内免费 | 4篇 |
专业分类
化学 | 476篇 |
晶体学 | 12篇 |
力学 | 14篇 |
数学 | 139篇 |
物理学 | 439篇 |
出版年
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2016年 | 12篇 |
2015年 | 13篇 |
2014年 | 12篇 |
2013年 | 40篇 |
2012年 | 36篇 |
2011年 | 43篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 45篇 |
2007年 | 45篇 |
2006年 | 45篇 |
2005年 | 40篇 |
2004年 | 26篇 |
2003年 | 28篇 |
2002年 | 37篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 20篇 |
1996年 | 24篇 |
1995年 | 21篇 |
1994年 | 27篇 |
1993年 | 26篇 |
1992年 | 36篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 13篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 10篇 |
1975年 | 11篇 |
1974年 | 14篇 |
1973年 | 20篇 |
1972年 | 12篇 |
1967年 | 8篇 |
排序方式: 共有1080条查询结果,搜索用时 15 毫秒
951.
The synthesis technique is given and the results of X-ray study of a copper(II) compound, Cu(O12N4C28H30)·7H2O, are reported. The structure is molecular and the copper atom is coordinated by a distorted octahedron exhibiting a Jahn-Teller effect. The Cu-O(carbonyl) bond is 0.31 Å longer than the axial carboxylate to copper bonds. 相似文献
952.
We are concerned with the problem of estimating the reachable set for a two-dimensional linear discrete-time system with bounded controls. Different approaches are adopted depending on whether the system matrix has real or complex eigenvalues. For the complex eigenvalue case, the quasiperiodic nature of minimum time trajectories is exploited in developing a simple, but often accurate, procedure. For the real eigenvalue case, over estimates of reachable sets can be trivially obtained using a decomposition method.The second author was supported by funds supplied by the John M. Bennett Faculty Fellowship, Trinity University, San Antonio, Texas. 相似文献
953.
Dawn Fisher 《Journal of Elasticity》1988,19(1):77-84
Elementary vector methods and the path-independent definition of a conservative force are used to show that a position dependent pressure p on a closed surface is conservative and has the potential R dV, where R is the region bounded by the surface.A useful definition of tensor cross product is introduced. 相似文献
954.
955.
956.
957.
Matrix metalloproteinase-1 is the major collagenolytic enzyme responsible for collagen damage in UV-irradiated human skin 总被引:2,自引:0,他引:2
Brennan M Bhatti H Nerusu KC Bhagavathula N Kang S Fisher GJ Varani J Voorhees JJ 《Photochemistry and photobiology》2003,78(1):43-48
Punch biopsies of human skin were obtained 1 day after irradiation with two minimal-erythema doses (MED) from either a UVB light source or a Solar Simulator and incubated in organ culture for 72 h. Organ culture fluids obtained at 24, 48 and 72 h were analyzed for collagenolytic activity and for reactivity with antibodies to matrix metalloproteinase-1 (MMP-1; interstitial collagenase) and MMP-13 (collagenase-3). High levels of collagenolytic activity were seen in organ culture fluid from skin exposed to either light source. MMP-1 was strongly induced in parallel, increasing from less than 100 ng/ml in organ culture fluid from control skin to approximately 1.1 microg/ml in culture fluid from UV-treated skin. Whereas most of the detectable MMP-1 in control culture fluid was represented by the latent form of the enzyme, approximately 50% of the enzyme was present as the active form in organ culture fluid of UV-exposed skin. In contrast, there was no detectable MMP-13 in control organ culture fluid and very little change after UV exposure (less than 100 ng/ml in both cases). Finally, neutralization studies with a blocking antibody to MMP-1 removed 95 +/- 4% of the collagenolytic activity in the organ culture fluid from UV-treated skin. These findings strongly implicate MMP-1 rather than MMP-13 as the major collagenolytic enzyme responsible for collagen damage in photoaging. 相似文献
958.
959.
960.