全文获取类型
收费全文 | 213篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
化学 | 100篇 |
晶体学 | 2篇 |
力学 | 5篇 |
数学 | 53篇 |
物理学 | 63篇 |
出版年
2023年 | 2篇 |
2020年 | 3篇 |
2018年 | 2篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 22篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 2篇 |
2008年 | 9篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 15篇 |
2004年 | 9篇 |
2003年 | 9篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1995年 | 3篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1927年 | 1篇 |
排序方式: 共有223条查询结果,搜索用时 15 毫秒
91.
Second order parallel algorithms for Fredholm integral equations with piecewise smooth displacement kernels are derived. One is based on a difference scheme of Runge-Kutta type for an unusual partial differential equations for continuous functions of two variables. The other is based on the trapezoidal quadrature rule applied to a modified integral equations. It is found that the Runge-Kutta type algorithm exhibits certain advantages.The work of these authors was supported in part by the NSF Grant DMS-9007030The work of this author was supported in part by a grant from the National Science and Engineering Research Council of Canada 相似文献
92.
Maximal hermitian solutions of the discrete algebraic matrix Riccati equation play an important role in least squares optimal control problems for discrete linear systems. We prove an existence and comparison theorem concerning maximal hermitian solutions. This theorem is inspired by known results for the algebraic Riccati equation arising in the least squares optimal control problem in continuous linear systems. 相似文献
93.
94.
95.
This paper describes the development of a liquid sampling approach for trace analysis by electron impact ionization magnetic sector mass spectrometry, with no chromatographic separation. Development of a liquid sample introduction interface based on the principle of Programmable Temperature Vaporizing (PTV) GC injection is shown. A univariate procedure for the analysis of trace (mg kg(-1)) propanoic acid in acetic acid was developed. Results from the laboratory-based analysis of acetic acid are presented and compared with conventional GC analysis. The detection limit was 16 mg l(-1) and the speed of analysis was employed to acquire 30 scans per minute thus reducing the confidence intervals of the results and potentially allowing production plants to run much closer to sales specifications. For the analysis of more complex samples where the analytes contained no unique ions, multivariate analysis was employed and up to three scans per minute were acquired. Results from the analysis of an ester for six trace impurities are shown. Calibration was by partial least squares regression. The detection limits for these components were 20-30 mg kg(-1), well within the required product specifications. The system proved to be robust and easy to operate, with analyses being carried out over a period of several months requiring no maintenance of the spectrometer and only cleaning of the injection liner of the PTV injector on a monthly basis. 相似文献
96.
Gerald M. Lancaster Fumihiro Honda Yasuo Fukuda J.Wayne Rabalais 《Chemical physics letters》1978,59(2):356-358
Secondary ion mass spectrometry (SIMS) has been used to detect the reactions induced by active ion bombardment (AIB) of N+2 on surfaces of pyrolytic graphite and a (100) Si crystal. The SIMS spectra exhibit ions of CN?, HCN?, HnC2N?(n = 2, 3, 4), HN?, and SiN?, indicating that reactions take place with the graphite and silicon as well as adsorbed hydrogen on the surfaces. 相似文献
97.
Mountford AJ Lancaster SJ Coles SJ Horton PN Hughes DL Hursthouse MB Light ME 《Inorganic chemistry》2005,44(16):5921-5933
The reaction between B(C(6)F(5))(3) and NH(3)(g) in light petroleum yielded the solvated adduct H(3)N.B(C(6)F(5))(3).NH(3). Treatment with a second equivalent of B(C(6)F(5))(3) afforded H(3)N.B(C(6)F(5))(3). Attempts to prepare the analogous alane adduct were unsuccessful and resulted in protolysis. Related compounds of the form R'R' 'N(H).M(C(6)F(5))(3) were synthesized from M(C(6)F(5))(3) and the corresponding primary and secondary amines (M = B, Al; R' = H, Me, CH(2)Ph; R' ' = Me, CH(2)Ph, CH(Me)(Ph); R'R' ' = cyclo-C(5)H(10)). The solid-state structures of 13 new compounds have been elucidated by single-crystal X-ray diffraction and are discussed. Each of the borane adducts has a significant bifurcated intramolecular hydrogen bond between an amino hydrogen and two o-fluorines, while N-H...F-C interactions in the alane adducts are weaker and more variable. (19)F NMR studies demonstrate that the borane adducts retain the bifurcated C-F...H...F-C hydrogen bond in solution. Compounds of the type R'R' 'N(H).M(C(6)F(5))(3) conform to Etter's rules for the prediction of hydrogen-bonding interactions. 相似文献
98.
Solutions of Dirichlet problems for quasilinear elliptic equations in unbounded domains inside a slab are considered. The rate at which solutions converge to their limiting functions at infinity is established in terms of properties of the top order coefficients of the operator and the rate at which the boundary values converge to their limiting functions.Our proofs are based on constructing appropriate barrier functions which depend on the behavior of coefficients of the operator and the rate of convergence of boundary value 相似文献
99.
100.