全文获取类型
收费全文 | 910篇 |
免费 | 17篇 |
国内免费 | 6篇 |
专业分类
化学 | 604篇 |
晶体学 | 18篇 |
力学 | 14篇 |
数学 | 151篇 |
物理学 | 146篇 |
出版年
2020年 | 6篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 15篇 |
2013年 | 52篇 |
2012年 | 53篇 |
2011年 | 35篇 |
2010年 | 27篇 |
2009年 | 23篇 |
2008年 | 41篇 |
2007年 | 47篇 |
2006年 | 47篇 |
2005年 | 42篇 |
2004年 | 46篇 |
2003年 | 23篇 |
2002年 | 40篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 16篇 |
1997年 | 10篇 |
1996年 | 16篇 |
1995年 | 16篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 18篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 13篇 |
1970年 | 5篇 |
1969年 | 4篇 |
1968年 | 9篇 |
排序方式: 共有933条查询结果,搜索用时 15 毫秒
61.
Markus Neuenschwander Ulrich Lienhard Hans-Peter Fahrni Beat Hurni 《Helvetica chimica acta》1978,61(7):2428-2436
Amide Synthesis by Means of ‘Push-Pull’-Acetylenes ‘Push-Pull’-acetylenes react easily with carbon acids, Addition of amines to the crude reaction mixture gives amides in an excellent yield by a simple one-pot procedure. Because of the high selectivity of the acetylenes 1 towards carboxylic functions and of the high selectivity of the enol esters 4 towards amine functions, ‘push-pull’-acetylenes could be excellent reagents for peptide synthesis. 相似文献
62.
Hanson RJ Macomber HK Morrison AC Boucher MA 《The Journal of the Acoustical Society of America》2005,117(1):400-412
The purpose of the work reported here is to further experimentally explore the wide variety of behaviors exhibited by driven vibrating wires, primarily in the nonlinear regime. When the wire is driven near a resonant frequency, it is found that most such behaviors are significantly affected by the splitting of the resonant frequency and by the existence of a "characteristic" axis associated with each split frequency. It is shown that frequency splitting decreases with increasing wire tension and can be altered by twisting. Two methods are described for determining the orientation of characteristic axes. Evidence is provided, with a possible explanation, that each axis has the same orientation everywhere along the wire. Frequency response data exhibiting nonlinear generation of transverse motion perpendicular to the driving direction, hysteresis, linear generation of perpendicular motion (sometimes tubular), and generation of motion at harmonics of the driving frequency are exhibited and discussed. Also reported under seemingly unchanging conditions are abrupt large changes in the harmonic content of the motion that sometimes involve large subharmonics and harmonics thereof. Slow transitions from one stable state of vibration to another and quasiperiodic motions are also exhibited. Possible musical significance is discussed. 相似文献
63.
The cluster size dependence of superconductivity in the conventional two-dimensional Hubbard model, commonly believed to describe high-temperature superconductors, is systematically studied using the dynamical cluster approximation and quantum Monte Carlo simulations as a cluster solver. Because of the nonlocality of the d-wave superconducting order parameter, the results on small clusters show large size and geometry effects. In large enough clusters, the results are independent of the cluster size and display a finite temperature instability to d-wave superconductivity. 相似文献
64.
We define cheat sensitive cryptographic protocols between mistrustful parties as protocols which guarantee that, if either cheats, the other has some nonzero probability of detecting the cheating. We describe an unconditionally secure cheat sensitive nonrelativistic bit commitment protocol which uses quantum information to implement a task which is classically impossible; we also describe a simple relativistic protocol. 相似文献
65.
66.
Addition of nitrogen to III-V semiconductor alloys radically changes their electronic properties. We report large-scale electronic structure calculations of GaAsN and GaPN using an approach that allows arbitrary states to emerge, couple, and evolve with composition. We find a novel mechanism of alloy formation where localized cluster states within the gap are gradually overtaken by a downwards moving conduction band edge, composed of both localized and delocalized states. This localized to delocalized transition explains many of the hitherto puzzling experimentally observed anomalies in III-V nitride alloys. 相似文献
67.
By using a simple Bäcklund-like transformation which linearizes the GL(N, C) self-dual Yang-Mills equation, an infinite number of local conservation laws for this equation are constructed. In the SL(N, C) case, the currents become trivial, which explains why these currents are not found in SU(N) gauge theory. 相似文献
68.
69.
Zhiwei Sun Peter J. Reynolds R. Kent Owen William A. Lester Jr. 《Theoretical chemistry accounts》1989,75(5):353-368
A study is made of electron-electron correlation functions for use in trial wave functions for small molecules. New forms are proposed that have only a few variational parameters, and these parameters have physical meanings that are easily discerned. Total energies for H2, LiH and Li2 computed using these correlation functions are presented, and comparison is made with previous forms, including the Jastrow-Pade form often used in Monte Carlo studies. We further treat the possibility that correlation depends not only on the separation of a pair of electrons but also on the location of the electron pair relative to the nuclei — indicative of a density-dependent or many body correlation effect. Our results indicate that such a many-body correlation effect is weakly present.This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Chemical Sciences Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098 相似文献
70.
C. H. Rich G. C. Whittam J. Kent Smith und H. Tusker 《Fresenius' Journal of Analytical Chemistry》1916,55(7):349
Ohne Zusammenfassung 相似文献