全文获取类型
收费全文 | 1336篇 |
免费 | 21篇 |
国内免费 | 4篇 |
专业分类
化学 | 948篇 |
晶体学 | 6篇 |
力学 | 13篇 |
数学 | 283篇 |
物理学 | 111篇 |
出版年
2019年 | 7篇 |
2017年 | 9篇 |
2016年 | 25篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 49篇 |
2012年 | 51篇 |
2011年 | 70篇 |
2010年 | 40篇 |
2009年 | 23篇 |
2008年 | 42篇 |
2007年 | 60篇 |
2006年 | 47篇 |
2005年 | 51篇 |
2004年 | 42篇 |
2003年 | 32篇 |
2002年 | 46篇 |
2001年 | 30篇 |
2000年 | 15篇 |
1999年 | 24篇 |
1998年 | 17篇 |
1997年 | 11篇 |
1996年 | 38篇 |
1995年 | 25篇 |
1994年 | 34篇 |
1993年 | 21篇 |
1992年 | 19篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 25篇 |
1984年 | 26篇 |
1983年 | 12篇 |
1982年 | 30篇 |
1981年 | 21篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 21篇 |
1977年 | 12篇 |
1976年 | 19篇 |
1975年 | 14篇 |
1974年 | 8篇 |
1973年 | 11篇 |
1972年 | 7篇 |
1971年 | 10篇 |
1964年 | 6篇 |
1926年 | 6篇 |
排序方式: 共有1361条查询结果,搜索用时 21 毫秒
51.
A capillary zone electrophoretic method with UV-scanning detection for the separation and identification of both free ligands and metal species is presented. The electrophoretic behavior of naturally occurring binding partners such as organic acids and amino acids was studied and compared with their metal-complexes. Copper(II) complexes of citrate and amino acids showed decreased electrophoretic mobilities and altered UV spectra. The optimized method was validated on ultrafiltered cow's milk and human milk samples. In cow's milk six low molecular weight substances, including citrate, orotate, and hippurate, could be separated. Metal supplementation with Cu(II), Ni(II), or Zn(II) decreased not only the citrate peak but also the orotate signal and in the case of copper(II) supplementation a new signal for the copper(II)-citrate complex appeared. In human milk samples various amino acids such as glutamate, phenylalanine, tyrosine, and tryptophan could be identified besides citrate. The electrophoretic mobilites and peak areas of the amino acids were also influenced by the metal supplementation. 相似文献
52.
In the search for organic ferromagnets polymers with a conjugated backbone and pendant persistent radicals are one route of interest. The synthesis of poly[4-(4-ethynylphenyl)-2′,4′,6′-trinitro-2,6-diphenyldiphenylamine] (p-3) and poly[4-(3-ethynylphenyl)-2′,4′,6′-trinitro-2,6-diphenyldiphenylamine] (m-3) as precursors of polyradicals are described. A dinuclear rhodium cyclooctadiene chloride complex as polymerization catalyst was used to yield polymers with molecular weights (gel-permeation chromatography) of 100 000 for m-3 and 210 000 for p-3 . 相似文献
53.
54.
55.
The oxide formation on thin copper films deposited on Si wafer was studied by XPS, SEM and Sequential Electrochemical Reduction Analysis SERA. The surfaces were oxidized in air with a reflow oven as used in electronic assembly at temperatures of 100 °C, 155 °C, 200 °C, 230 °C and 260 °C. The SERA analyses detected only the formation of Cu2O but the XPS analysis done for the calibration of the SERA equipment proved also the presence of a CuO layer smaller than 2 nm above the Cu2O oxide. The oxide growth follows a power-law dependence on time within this temperature range and an activation energy of 33.1 kJ/mol was obtained. The wettability of these surfaces was also determined by measuring the contact angle between solder and copper substrate after the soldering process. A correlation between oxide thickness and wetting angle was established. It was found that the wetting is acceptable only when the oxide thickness is smaller than 16 nm. An activation energy of 27 kJ/mol was acquired for the spreading of lead free solder on oxidized copper surfaces.From wetting tests on copper surfaces protected by Organic Solderability Preservatives (OSP), it was possible to calculate the activation energy for the thermal decomposition of these protective layers. 相似文献
56.
57.
A real-time path-integral Monte Carlo approach is developed to study the dynamics in a many-body quantum system coupled to a phonon background until reaching a nonequilibrium stationary state. The approach is based on augmenting an exact reduced equation for the evolution of the system in the interaction picture which is amenable to an efficient path integral (worldline) Monte Carlo approach. Results obtained for a model of inelastic tunneling spectroscopy reveal the applicability of the approach to a wide range of physically important regimes, including high (classical) and low (quantum) temperatures, and weak (perturbative) and strong electron-phonon couplings. 相似文献
58.
Lothar Müller 《Nuclear Physics A》1981,360(2):331-358
The relativistic theory for few-nucleon systems developed by Glöckle and Müller is evaluated numerically for a model of scalar particles exchanging scalar mesons to lowest order in the coupling constant. 2-nucleon binding energies and scattering phases and 3-nucleon binding energies are compared with the usual non-relativistic calculation for different choices of the potential. The relativistic treatment gives a weaker binding. The mechanism of this is studied in more detail. We compare our results with the relativistic correction in the 1/c2 expansion of Foldy and Krajcik. 相似文献
59.
The evaluation of matrix functions of the form f(A)v, where A is a large sparse or structured symmetric matrix, f is a nonlinear function, and v is a vector, is frequently subdivided into two steps: first an orthonormal basis of an extended Krylov subspace of fairly small dimension is determined, and then a projection onto this subspace is evaluated by a method designed for small problems. This paper derives short recursion relations for orthonormal bases of extended Krylov subspaces of the type Km,mi+1(A)=span{A-m+1v,…,A-1v,v,Av,…,Amiv}, m=1,2,3,…, with i a positive integer, and describes applications to the evaluation of matrix functions and the computation of rational Gauss quadrature rules. 相似文献
60.
Tikhonov regularization is a popular method for the solution of linear discrete ill-posed problems with error-contaminated data. Nonstationary iterated Tikhonov regularization is known to be able to determine approximate solutions of higher quality than standard Tikhonov regularization. We investigate the choice of solution subspace in iterative methods for nonstationary iterated Tikhonov regularization of large-scale problems. Generalized Krylov subspaces are compared with Krylov subspaces that are generated by Golub–Kahan bidiagonalization and the Arnoldi process. Numerical examples illustrate the effectiveness of the methods. 相似文献