全文获取类型
收费全文 | 22367篇 |
免费 | 5356篇 |
国内免费 | 3368篇 |
专业分类
化学 | 12956篇 |
晶体学 | 498篇 |
力学 | 1765篇 |
综合类 | 233篇 |
数学 | 1759篇 |
物理学 | 13880篇 |
出版年
2024年 | 65篇 |
2023年 | 258篇 |
2022年 | 624篇 |
2021年 | 742篇 |
2020年 | 912篇 |
2019年 | 715篇 |
2018年 | 690篇 |
2017年 | 845篇 |
2016年 | 973篇 |
2015年 | 941篇 |
2014年 | 1448篇 |
2013年 | 1939篇 |
2012年 | 1507篇 |
2011年 | 1636篇 |
2010年 | 1406篇 |
2009年 | 1638篇 |
2008年 | 1603篇 |
2007年 | 1637篇 |
2006年 | 1552篇 |
2005年 | 1251篇 |
2004年 | 1175篇 |
2003年 | 1071篇 |
2002年 | 853篇 |
2001年 | 758篇 |
2000年 | 705篇 |
1999年 | 648篇 |
1998年 | 546篇 |
1997年 | 473篇 |
1996年 | 413篇 |
1995年 | 328篇 |
1994年 | 272篇 |
1993年 | 219篇 |
1992年 | 188篇 |
1991年 | 196篇 |
1990年 | 112篇 |
1989年 | 115篇 |
1988年 | 95篇 |
1987年 | 91篇 |
1986年 | 68篇 |
1985年 | 65篇 |
1984年 | 47篇 |
1983年 | 29篇 |
1982年 | 42篇 |
1981年 | 39篇 |
1980年 | 33篇 |
1979年 | 32篇 |
1978年 | 14篇 |
1977年 | 24篇 |
1976年 | 12篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
81.
82.
83.
84.
XiaoMinSUN DaChengFENG ZhengTingCAI 《中国化学快报》2004,15(6):749-752
For the Na I2 collision system, theoretical study is performed on the QCISD(T) level by using ab initio method. The ab initio potential energy surfaces are got and on them the long-lived complexes are found and optimized. These results verify the crossed molecule beam experimental phenomenon and the detailed geometry structures are given for the first time. The role of the complexes in the reaction path is also described in detail. 相似文献
85.
Kinetic parameters of amino acid cations in an MK-40 ion-exchange membrane are calculated from the conductivity data. A theoretical quantum-chemical analysis of experimental activation energies for conduction suggests a mechanism of elementary act of transport of amino acid cations in the membrane. 相似文献
86.
We analyse a model for equilibrium configurations of composite systems of nematic liquid crystal with polymer inclusions, in the presence of an external magnetic field. We assume that the system has a periodic structure, and consider the relaxed problem on the unit length constraint of the nematic director field. The relaxation of the Oseen–Frank energy functional is carried out by including bulk as well as surface energy penalty terms, rendering the problem fully non‐linear. We employ two‐scale convergence methods to obtain effective configurations of the system, as the size of the polymeric inclusions tends to zero. We discuss the minimizers of the effective energies for, both, the constrained as well as the unconstrained models. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
87.
Toshihiro Kobayashi 《Mathematical Methods in the Applied Sciences》2004,27(18):2171-2184
In this paper low‐gain adaptive stabilization of undamped semilinear second‐order hyperbolic systems is considered in the case where the input and output operators are collocated. The linearized systems have an infinite number of poles and zeros on the imaginary axis. The adaptive stabilizer is constructed by a low‐gain adaptive velocity feedback. The closed‐loop system is governed by a non‐linear evolution equation. First, the well‐posedness of the closed‐loop system is shown. Next, an energy‐like function and a multiplier function are introduced and the exponential stability of the closed‐loop system is analysed. Some examples are given to illustrate the theory. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
88.
89.
J. T. Hoeft M. Polcik D. I. Sayago M. Kittel R. Terborg R. L. Toomes J. Robinson D. P. Woodruff M. Pascal G. Nisbet C. L. A. Lamont 《Surface science》2003,540(2-3):441-456
The local adsorption geometry of CO adsorbed in different states on Ni(1 0 0) and on Ni(1 0 0) precovered with atomic hydrogen has been determined by C 1s (and O 1s) scanned-energy mode photoelectron diffraction, using the photoelectron binding energy changes to characterise the different states. The results confirm previous spectroscopic assignments of local atop and bridge sites both with and without coadsorbed hydrogen. The measured Ni–C bondlengths for the Ni(1 0 0)/CO states show an increase of 0.16 ± 0.04 Å in going from atop to bridge sites, while comparison with similar results for Ni(1 1 1)/CO for threefold coordinated adsorption sites show a further lengthening of the bond by 0.05 ± 0.04 Å. These changes in the Ni–CO chemisorption bondlength with bond order (for approximately constant adsorption energy) are consistent with the standard Pauling rules. However, comparison of CO adsorbed in the atop geometry with and without coadsorbed hydrogen shows that the coadsorption increases the Ni–C bondlength by only 0.06 ± 0.04 Å, despite the decrease in adsorption energy of a factor of 2 or more. This result is also reproduced by density functional theory slab calculations. The results of both the experiments and the density functional theory calculations show that CO adsorption onto the Ni(1 0 0)/H surface is accompanied by significant structural modification; the low desorption energy may then be attributed to the energy cost of this restructuring rather than weak local bonding. 相似文献
90.