全文获取类型
收费全文 | 921篇 |
免费 | 17篇 |
国内免费 | 9篇 |
专业分类
化学 | 314篇 |
晶体学 | 5篇 |
力学 | 20篇 |
数学 | 335篇 |
物理学 | 273篇 |
出版年
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 11篇 |
2019年 | 10篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 19篇 |
2015年 | 14篇 |
2014年 | 13篇 |
2013年 | 45篇 |
2012年 | 35篇 |
2011年 | 32篇 |
2010年 | 20篇 |
2009年 | 19篇 |
2008年 | 33篇 |
2007年 | 42篇 |
2006年 | 50篇 |
2005年 | 44篇 |
2004年 | 38篇 |
2003年 | 27篇 |
2002年 | 28篇 |
2001年 | 12篇 |
2000年 | 24篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 18篇 |
1993年 | 24篇 |
1992年 | 29篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 19篇 |
1980年 | 11篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1975年 | 12篇 |
1974年 | 9篇 |
1973年 | 5篇 |
排序方式: 共有947条查询结果,搜索用时 15 毫秒
151.
Tal S Blumer-Ganon B Kapon M Eichen Y 《Journal of the American Chemical Society》2005,127(27):9848-9854
A new pi-conjugated electroactive 4,4'-bipyridinium that bears two pyridazone self-complementary units was prepared and characterized. The new system readily assembles and forms at least two stable charge-transfer crystalline structures having a thermal population of unpaired electrons. The crystals of one phase exhibit electrical bistability, displaying either high (ON) and low (OFF) conductivity, at the same applied bias, depending on the electrical history of the system. The relation between the supramolecular structure of the crystals and their electrical properties is also discussed. 相似文献
152.
The degree of diastereoselectivity in the wrapping of four new chiral Salan ligands to form chiral-at-metal titanium complexes ranged from mild to perfect as a function of the ligands' N substituents; the enantiomerically pure complexes catalyzed the addition of diethyl zinc to benzaldehyde in 73-76% enantiomeric excess. 相似文献
153.
Herein we report that trifluorohexylsilane (2), trifluorophenylsilane (3) and trifluoro(pentafluorophenyl)silane (4) form new hypervalent complexes with pyridine (py) and with 4-methoxypyridine (MeO-py), through intermolecular Si...N interactions. In general, stronger and more efficient binding is observed for the more electron poor (Si atom in) silane 4 and for the more electron rich (N atom in) 4-methoxypyridine. Binding constants of 15+/-2, 25+/-5, and 550+/-100 M(-1) at 25 degrees C in benzene were measured for the formation of the pentacoordinate 2.py, 3.py, and 3.MeO-py complexes, respectively. In addition, silane 3 also forms the hexacoordinate 3-2py and 3-2MeO-py complexes at low temperatures and silane 4 forms the 4-2py complex below room temperature and the 4-2MeO-py complex already at room temperature and in a high concentration. The various types of hypervalent complexes and different binding strengths described here for silanes 2-4 and previously for trifluoro(phenylethynyl)silane (1) and the possibility to modulate the binding modes (penta- vs hexacoordination) of these complexes (by the type of amine used, concentration, and the temperature applied) suggest that such new intermolecular Si...N interactions could be used as efficient and versatile binding motifs in supramolecular chemistry. 相似文献
154.
We prove certain identities between Bessel functions attached to irreducible unitary representations ofPGL
2(R) and Bessel functions attached to irreducible unitary representations of the double cover ofSL
2(R). These identities give a correspondence between such representations which turns out to be the Waldspurger correspondence.
In the process we prove several regularity theorems for Bessel distributions which appear in the relative trace formula. In
the heart of the proof lies a classical result of Weber and Hardy on a Fourier transform of classical Bessel functions. This
paper constitutes the local (real) spectral theory of the relative trace formula for the Waldspurger correspondence for which
the global part was developed by Jacquet.
Research of first author was partially supported by NSF grant DMS-0070762.
Research of second author was partially supported by NSF grant DMS-9729992 and DMS 9971003. 相似文献
155.
The paper applies Jacobi's fundamental result on minors of the adjoint matrix to obtain properties on determinants of unimodular matrices. 相似文献
156.
157.
Orr R. S. und J. N. Grant 《Colloid and polymer science》1962,184(1):91
Ohne Zusammenfassung 相似文献
158.
The time evolution of wavefunctions ψ(t) is compared in two systems, one with a regular energy spectrum and one with an irregular spectrum. The behavior of P(t) = {|[ψ(O)|ψ(y]}|2 is found to be the same in both systems, P(t) decay is insensitive to the coupling between the degrees of freedom. 相似文献
159.
160.
Moshe Dror 《Discrete Applied Mathematics》2010,158(16):1767-1776
We examine computational complexity implications for scheduling problems with job precedence relations with respect to strong precedence versus weak precedence. We propose a consistent definition of strong precedence for chains, trees, and series-parallel orders. Using modular decomposition for partially ordered sets (posets), we restate and extend past complexity results for chains and trees as summarized in Dror (1997) [5]. Moreover, for series-parallel posets we establish new computational complexity results for strong precedence constraints for single- and multi-machine problems. 相似文献