全文获取类型
收费全文 | 1407篇 |
免费 | 45篇 |
国内免费 | 6篇 |
专业分类
化学 | 771篇 |
晶体学 | 8篇 |
力学 | 72篇 |
数学 | 296篇 |
物理学 | 311篇 |
出版年
2023年 | 9篇 |
2022年 | 29篇 |
2021年 | 35篇 |
2020年 | 29篇 |
2019年 | 40篇 |
2018年 | 33篇 |
2017年 | 34篇 |
2016年 | 58篇 |
2015年 | 34篇 |
2014年 | 52篇 |
2013年 | 92篇 |
2012年 | 96篇 |
2011年 | 112篇 |
2010年 | 72篇 |
2009年 | 60篇 |
2008年 | 89篇 |
2007年 | 67篇 |
2006年 | 74篇 |
2005年 | 71篇 |
2004年 | 52篇 |
2003年 | 53篇 |
2002年 | 37篇 |
2001年 | 10篇 |
2000年 | 16篇 |
1999年 | 22篇 |
1998年 | 19篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1984年 | 6篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1966年 | 2篇 |
1938年 | 7篇 |
排序方式: 共有1458条查询结果,搜索用时 15 毫秒
1.
Valentin A. Semenov Dmitry O. Samultsev Leonid B. Krivdin 《Magnetic resonance in chemistry : MRC》2020,58(6):532-539
The density functional theory calculation of 1H and 13C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated 1H and 13C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases. 相似文献
2.
Multinomial permutations on a circle are considered in the framework of combinatorics. Different cases are presented and shown to agree with previously derived formula for the number of cyclic necklaces. Two applied examples are discussed with a view to illustrate the implications of derived formulas. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
3.
We prove that the sequence of finite reflecting branching Brownian motion forests defined by Burdzy and Le Gall ([1]) converges in probability to the “super-Brownian motion with reflecting historical paths.” This solves an open problem posed in [1], where only tightness was proved for the sequence of approximations. Several results on path behavior were proved in [1] for all subsequential limits–they obviously hold for the unique limit found in the present paper.Mathematics Subject Classification (2000): Primary 60H15, Secondary 35R60Supported in part by NSF Grant DMS-0071486, Israel Science Foundation Grants 12/98 and 116/01 - 10.0, and the U.S.-Israel Binational Science Foundation (grant No. 2000065). 相似文献
4.
Leonid Polterovich 《Geometric And Functional Analysis》1996,6(4):726-739
Supported by the United States-Israel Binational Science Foundation grant 94-00302 相似文献
5.
Let G=(V,E) be a (directed) graph with vertex set V and edge (arc) set E. Given a set P of source-sink pairs of vertices of G, an important problem that arises in the computation of network reliability is the enumeration of minimal subsets of edges (arcs) that connect/disconnect all/at least one of the given source-sink pairs of P. For undirected graphs, we show that the enumeration problems for conjunctions of paths and disjunctions of cuts can be solved in incremental polynomial time. Furthermore, under the assumption that P consists of all pairs within a given vertex set, we also give incremental polynomial time algorithm for enumerating all minimal path disjunctions and cut conjunctions. For directed graphs, the enumeration problem for cut disjunction is known to be NP-complete. We extend this result to path conjunctions and path disjunctions, leaving open the complexity of the enumeration of cut conjunctions. Finally, we give a polynomial delay algorithm for enumerating all minimal sets of arcs connecting two given nodes s1 and s2 to, respectively, a given vertex t1, and each vertex of a given subset of vertices T2. 相似文献
6.
Boris Golinskii Leonid Golinskii 《Journal of Mathematical Analysis and Applications》1998,220(2):1050
The known conditions due to G. Baxter, Ya. L. Geronimus, and B. L. Golinskii which guarantee the uniform boundedness and/or uniform asymptotic representation for orthonormal polynomials on the unit circle are under consideration. We show that these conditions are in general not necessary. We discuss the relation between the orthonormal polynomials on the unit circle, the best approximations, and absolutely convergent Fourier series. 相似文献
7.
8.
9.
The perturbed-chain statistical associating fluid theory (PC-SAFT) is studied for a wide range of temperature, T, pressure, p, and (effective) chain length, m, to establish the generic phase diagram of polymers according to this theory. In addition to the expected gas-liquid coexistence, two additional phase separations are found, termed "gas-gas" equilibrium (at very low densities) and "liquid-liquid" equilibrium (at densities where the system is expected to be solid already). These phase separations imply that in one-component polymer systems three critical points occur, as well as equilibria of three fluid phases at triple points. However, Monte Carlo simulations of the corresponding system yield no trace of the gas-gas and liquid-liquid equilibria, and we conclude that the latter are just artefacts of the PC-SAFT approach. Using PC-SAFT to correlate data for polybutadiene melts, we suggest that discrepancies in modelling the polymer density at ambient temperature and high pressure can be related to the presumably artificial liquid-liquid phase separation at lower temperatures. Thus, particular care is needed in engineering applications of the PC-SAFT theory that aims at predicting properties of macromolecular materials. 相似文献
10.
Kleitz F Solovyov LA Anilkumar GM Choi SH Ryoo R 《Chemical communications (Cambridge, England)》2004,(13):1536-1537
Exceptional control of the phase behavior of highly ordered large pore mesostructured silica (with the choice of Fm3m, Im3m or p6mm symmetry) is achieved using a triblock copolymer (EO(106)PO(70)EO(106)) and butanol at low acid concentrations. 相似文献