全文获取类型
收费全文 | 35738篇 |
免费 | 2932篇 |
国内免费 | 3001篇 |
专业分类
化学 | 24856篇 |
晶体学 | 391篇 |
力学 | 1242篇 |
综合类 | 161篇 |
数学 | 5446篇 |
物理学 | 9575篇 |
出版年
2023年 | 371篇 |
2022年 | 778篇 |
2021年 | 866篇 |
2020年 | 878篇 |
2019年 | 891篇 |
2018年 | 816篇 |
2017年 | 786篇 |
2016年 | 1412篇 |
2015年 | 1435篇 |
2014年 | 1539篇 |
2013年 | 2682篇 |
2012年 | 2789篇 |
2011年 | 2938篇 |
2010年 | 1923篇 |
2009年 | 2057篇 |
2008年 | 2140篇 |
2007年 | 1961篇 |
2006年 | 1657篇 |
2005年 | 1533篇 |
2004年 | 1681篇 |
2003年 | 1274篇 |
2002年 | 1183篇 |
2001年 | 699篇 |
2000年 | 651篇 |
1999年 | 496篇 |
1998年 | 404篇 |
1997年 | 373篇 |
1996年 | 352篇 |
1995年 | 316篇 |
1994年 | 248篇 |
1993年 | 273篇 |
1992年 | 227篇 |
1991年 | 182篇 |
1990年 | 192篇 |
1989年 | 161篇 |
1988年 | 177篇 |
1987年 | 133篇 |
1986年 | 151篇 |
1985年 | 190篇 |
1984年 | 206篇 |
1983年 | 150篇 |
1982年 | 157篇 |
1981年 | 157篇 |
1980年 | 142篇 |
1979年 | 140篇 |
1978年 | 130篇 |
1977年 | 119篇 |
1976年 | 129篇 |
1975年 | 122篇 |
1974年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
D. Barrios Rolanía G. Lpez Lagomasino E. B. Saff 《Journal of Approximation Theory》2003,124(2):263-281
Using a convergence theorem for Fourier–Padé approximants constructed from orthogonal polynomials on the unit circle, we prove an analogue of Hadamard's theorem for determining the radius of m-meromorphy of a function analytic on the unit disk and apply this to the location of poles of the reciprocal of Szeg
functions. 相似文献
33.
Parameters of Gaussian multivariate models are often estimated using the maximum likelihood approach. In spite of its merits, this methodology is not practical when the sample size is very large, as, for example, in the case of massive georeferenced data sets. In this paper, we study the asymptotic properties of the estimators that minimize three alternatives to the likelihood function, designed to increase the computational efficiency. This is achieved by applying the information sandwich technique to expansions of the pseudo-likelihood functions as quadratic forms of independent normal random variables. Theoretical calculations are given for a first-order autoregressive time series and then extended to a two-dimensional autoregressive process on a lattice. We compare the efficiency of the three estimators to that of the maximum likelihood estimator as well as among themselves, using numerical calculations of the theoretical results and simulations. 相似文献
34.
Pedro lvarez‐Boo Jos Sergio Casas Alfonso Castieiras María Delfina Couce Eduardo Freijanes Eva Novoa Jos Sordo 《应用有机金属化学》2003,17(9):725-729
Reaction of dichloro‐ and dibromodimethyltin(IV) with 2‐(pyrazol‐1‐ylmethyl)pyridine (PMP) afforded [SnMe2Cl2(PMP)] and [SnMe2Br2(PMP)] respectively. The new complexes were characterized by elemental analysis and mass spectrometry and by IR, Raman and NMR (1H, 13C) spectroscopies. Structural studies by X‐ray diffraction techniques show that the compounds consist of discrete units with the tin atom octahedrally coordinated to the carbon atoms of the two methyl groups in a trans disposition (Sn? C = 2.097(5), 2.120(5) Å and 2.110(6), 2.121(6) Å in the chloro and in the bromo compounds respectively), two cis halogen atoms (Sn? Cl = 2.4908(16), 2.5447(17) Å; Sn? Br = 2.6875(11), 2.7464(9) Å) and the two donor atoms of the ligand (Sn? N = 2.407(4), 2.471(4) Å and 2.360(5), 2.455(5) Å). In both cases, the Sn? N(pyridine) bond length is markedly longer than the Sn? N(pyrazole) distance. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
35.
36.
Summary. We introduce linear semi-implicit complementary volume numerical scheme for solving level set like nonlinear degenerate diffusion
equations arising in image processing and curve evolution problems. We study discretization of image selective smoothing equation
of mean curvature flow type given by Alvarez, Lions and Morel ([3]). Solution of the level set equation of Osher and Sethian
([26], \[30]) is also included in the study. We prove and estimates for the proposed scheme and give existence of its (generalized) solution in every discrete time-scale step. Efficiency
of the scheme is given by its linearity and stability. Preconditioned iterative solvers are used for computing arising linear
systems. We present computational results related to image processing and plane curve evolution.
Received April 25, 2000 / Revised version received June 11, 2001 / Published online November 15, 2001 相似文献
37.
Lubomír Kubáček 《Mathematica Slovaca》2007,57(6):571-588
The multivariate model, where not only parameters of the mean value of the observation matrix, but also some other parameters
occur in constraints, is considered in the paper. Some basic inference is presented under the condition that the covariance
matrix is either unknown, or partially unknown, or known.
Supported by the grant of the Council of Czech Republic MSM 6 198 959 214. 相似文献
38.
The presented one-capacitor pinch driver, designed as a compact coaxial structure (including spark-gap and discharge section) consistent with the capacitor output, generates a current of 200 kA with 700 ns quarter-period, suitable for studying the optimization of Z-pinch radiative characteristics. The driver is described, measurements of its parameters summarized, and relations to our previous and future activities briefly reviewed.This work was supported in part by the Grant Agency of the Czech Republic under contract No. 202/93/1023. 相似文献
39.
V. D. Fedotov N. P. Obuchov R. A. Zadikhanov J. Spěváček J. Straka 《Applied magnetic resonance》1993,4(4):491-511
The combined analysis of1H and13C NMR relaxation data in solid lysozyme and some typical homopolypeptides was carried out by using “model-free” approach. Three types of relaxation transitions (γ’, γ and β) were revealed in the temperature range investigated. The microdynamical parameters of these motions were determined. From the comparison of these parameters with those of selected synthetic polymers it follows that the molecular motions in proteins and synthetic polymers are of the same nature. All these motions show pronounced anisotropic character. In the investigated temperature range no molecular motions corresponding to α-relaxation (liquid-like) transition were revealed. The hydration effects on parameters of the motions in proteins were considered. The most pronounced effect takes place for β-transition. The effect of Brownian rotation of protein molecule in solution on measured correlation function of local motions was also discussed. 相似文献
40.