全文获取类型
收费全文 | 87157篇 |
免费 | 753篇 |
国内免费 | 453篇 |
专业分类
化学 | 30721篇 |
晶体学 | 833篇 |
力学 | 6852篇 |
数学 | 33342篇 |
物理学 | 16615篇 |
出版年
2022年 | 61篇 |
2021年 | 102篇 |
2020年 | 221篇 |
2019年 | 184篇 |
2018年 | 10501篇 |
2017年 | 10322篇 |
2016年 | 6315篇 |
2015年 | 1052篇 |
2014年 | 544篇 |
2013年 | 799篇 |
2012年 | 4285篇 |
2011年 | 11041篇 |
2010年 | 5960篇 |
2009年 | 6328篇 |
2008年 | 7078篇 |
2007年 | 9226篇 |
2006年 | 749篇 |
2005年 | 1792篇 |
2004年 | 1933篇 |
2003年 | 2249篇 |
2002年 | 1299篇 |
2001年 | 346篇 |
2000年 | 397篇 |
1999年 | 239篇 |
1998年 | 281篇 |
1997年 | 274篇 |
1996年 | 335篇 |
1995年 | 238篇 |
1994年 | 223篇 |
1993年 | 218篇 |
1992年 | 166篇 |
1991年 | 172篇 |
1990年 | 141篇 |
1989年 | 133篇 |
1988年 | 122篇 |
1987年 | 127篇 |
1986年 | 114篇 |
1985年 | 158篇 |
1984年 | 139篇 |
1983年 | 100篇 |
1982年 | 144篇 |
1981年 | 126篇 |
1980年 | 124篇 |
1979年 | 140篇 |
1978年 | 120篇 |
1977年 | 99篇 |
1976年 | 104篇 |
1975年 | 79篇 |
1974年 | 70篇 |
1973年 | 83篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
1.
Yuliang Zhao 《中国科学:化学(英文版)》2018,61(12):1481-1482
正Living organisms have developed their unique strategies during the natural evolution for building hard tissues with minerals, including silica, calcium carbonate, calcium phosphate, and ferric oxide [1]. Such biomineralized materials generally have complex hierarchical structures with excellent mechanical properties. Although bioinspired approaches have led to the creation of well-defined synthetic structural materials ranging from micro to macro scales, the rational design of discrete biomimetic structures at the nanoscale remains a grand challenge. 相似文献
2.
JuHong Ge 《Nonlinear dynamics》2018,94(1):87-98
A five-neuron network model with multiple delays is proposed. This paper presents the combined effect of different delays on the dynamics of the proposed network. Pitchfork bifurcation is discussed in detail with the variation of the value of coupled weight or attenuation rate of internal neurons. By analyzing the corresponding characteristic equation, some stable criteria on delay-dependence and delay-independence are derived including multiple delays and coupled weights and the periodic oscillation arises bifurcated from the trivial equilibrium after the network loses its stability. Stable regions on delay-dependence are displayed in the two delayed parameter plane. It is shown that multiple delays can produce stability switching between resting state and periodic activity. Finally, theoretical results are justified by providing two illustrative examples. 相似文献
3.
It is shown that the countably infinite dimensional pointed vector space (the vector space equipped with a constant) over a finite field has infinitely many first order definable reducts. This implies that the countable homogeneous Boolean-algebra has infinitely many reducts. 相似文献
4.
5.
Laurens Kooijman Dr. Matthias Schuster Christian Baumann Simon Jurt Dr. Frank Löhr Dr. Boris Fürtig Prof. Dr. Peter Güntert Prof. Dr. Oliver Zerbe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(47):21151-21158
To achieve efficient proton pumping in the light-driven proton pump bacteriorhodopsin (bR), the protein must be tightly coupled to the retinal to rapidly convert retinal isomerization into protein structural rearrangements. Methyl group dynamics of bR embedded in lipid nanodiscs were determined in the dark-adapted state, and were found to be mostly well ordered at the cytosolic side. Methyl groups in the M145A mutant of bR, which displays only 10 % residual proton pumping activity, are less well ordered, suggesting a link between side-chain dynamics on the cytosolic side of the bR cavity and proton pumping activity. In addition, slow conformational exchange, attributed to low frequency motions of aromatic rings, was indirectly observed for residues on the extracellular side of the bR cavity. This may be related to reorganization of the water network. These observations provide a detailed picture of previously undescribed equilibrium dynamics on different time scales for ground-state bR. 相似文献
6.
Ein elektronenreiches cyclisches (Alkyl)(amino)carben auf Au(111)-, Ag(111)- und Cu(111)-Oberflächen
Anne Bakker Dr. Matthias Freitag Elena Kolodzeiski Peter Bellotti Dr. Alexander Timmer Dr. Jindong Ren Bertram Schulze Lammers Daniel Moock Prof. Dr. Herbert W. Roesky Dr. Harry Mönig Dr. Saeed Amirjalayer Prof. Dr. Harald Fuchs Prof. Dr. Frank Glorius 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13745-13749
7.
Journal of Statistical Physics - We consider the symmetric exclusion process on suitable random grids that approximate a compact Riemannian manifold. We prove that a class of random walks on these... 相似文献
8.
9.
10.
Zinovy Reichstein 《Archiv der Mathematik》2018,111(5):449-455
We use a recent advance in birational geometry to prove new lower bounds on the essential dimension of some finite groups. 相似文献