全文获取类型
收费全文 | 8090篇 |
免费 | 224篇 |
国内免费 | 976篇 |
专业分类
化学 | 4240篇 |
晶体学 | 11篇 |
力学 | 262篇 |
综合类 | 10篇 |
数学 | 3145篇 |
物理学 | 1622篇 |
出版年
2024年 | 16篇 |
2023年 | 148篇 |
2022年 | 206篇 |
2021年 | 148篇 |
2020年 | 185篇 |
2019年 | 182篇 |
2018年 | 155篇 |
2017年 | 195篇 |
2016年 | 202篇 |
2015年 | 179篇 |
2014年 | 298篇 |
2013年 | 553篇 |
2012年 | 395篇 |
2011年 | 493篇 |
2010年 | 446篇 |
2009年 | 620篇 |
2008年 | 598篇 |
2007年 | 647篇 |
2006年 | 475篇 |
2005年 | 337篇 |
2004年 | 340篇 |
2003年 | 277篇 |
2002年 | 242篇 |
2001年 | 189篇 |
2000年 | 157篇 |
1999年 | 137篇 |
1998年 | 156篇 |
1997年 | 150篇 |
1996年 | 159篇 |
1995年 | 117篇 |
1994年 | 133篇 |
1993年 | 99篇 |
1992年 | 84篇 |
1991年 | 60篇 |
1990年 | 60篇 |
1989年 | 56篇 |
1988年 | 42篇 |
1987年 | 27篇 |
1986年 | 40篇 |
1985年 | 42篇 |
1984年 | 40篇 |
1983年 | 18篇 |
1982年 | 54篇 |
1981年 | 27篇 |
1980年 | 29篇 |
1979年 | 30篇 |
1978年 | 18篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1973年 | 4篇 |
排序方式: 共有9290条查询结果,搜索用时 187 毫秒
61.
V. A. KHATSKEVICH V.A. SENDEROV 《数学学报(英文版)》2006,22(6):1687-1694
The operator sets, which are the subject of this paper, have been studied in many papers where, under different restrictions on the generating operators, convexity, compactness in the weak operator topology, and nonemptiness were proved for sets of different classes under study. Then the results obtained were used in these papers to solve several applied problems. Namely, they played the key role in establishing the dichotomy of nonautonomous dynamical systems, with either continuous or discrete time. In the present paper, we generalize and sharpen the already known criteria and obtain several new criteria for convexity, compactness, and nonemptiness of several special operator sets. Then, using the assertions obtained, we construct examples of sets of the form under study which are nonconvex, noncompact in the weak operator topology, as well as empty, and are generated by "smooth" operators of a special class. The existence problem for such sets remained open until the authors of this paper announced some of its results. 相似文献
62.
Several techniques for experimental determination of floating point precision in practical computations are examined, and applied to linear algebra algorithms. These techniques are simple enough to be directly applicable to existing production codes, requiring a very limited amount of software on many machines, and yet they yield interesting information on the numerical precision of a computation. Our choice of linear algebra algorithms includes a direct solver (namely the MA32 program from the Harwell Library) and several variants of preconditioned conjugate gradients (the methods DIAG, INV, MINV and POL of Reference 1). The results may be of interest as method selection criteria, and thus complement Mflop performance data available from several sources. 相似文献
63.
有序分组资料的线性趋势检验主要用于检验几个二项总体反应率的线性趋势;在医学与生物学中最典型的用途是研究剂量和反应的关系. 如果用Z检验来代替通常在本检验中所用的卡方检验,就可容易地导出本检验的确切概率计算方法,和其他2×C有序列联表有着相同的形式.本文给出了该检验的确切概率计算方法. 相似文献
64.
In this article, we solve in closed form a system of nonlinear differential equations modelling the elastica in space of a thin, flexible, straight rod, loaded by a constant thrust at its free end. Common linearizations of strength of materials are of course not applicable any way, because we analyze great deformations, even if not so large to go off the linear elasticity range. By passing to cylindrical coordinates ρ, θ, z, we earn a more tractable differential system evaluating ρ as elliptic function of polar anomaly θ and also providing z through elliptic integrals of I and III kind. Deformed rod’s centerline is then completely described under both tensile or compressive load. Finally, the planar case comes out as a degeneracy, where the Bernoulli lemniscatic integral appears. 相似文献
65.
该文通过构造特殊形式的有效集来逼近KKT点处的有效集,给出了一个任意初始点下的序列线性方程组新算法,并证明了该算法在没有严格互补松驰条件的情况下具有全局收敛性和一步超线性收敛性。
相似文献
66.
67.
本文讨论了在带有截断情况的线性回归模型中 ,响应变量均值的估计问题 .将经验似然的方法应用到带有截断情况的回归模型中 ,在估计响应变量的均值时构造了调整的经验似然统计量 ,证明了在一定的条件下 ,该统计量渐近服从 χ2 分布 ,给出了均值的置信区间 ,并与正态下得到的结果进行了比较 ,模拟的结果说明了经验似然的优良性 . 相似文献
68.
ρ混合、φ混合、ψ混合线性模型M估计的强相合性 总被引:5,自引:3,他引:2
研究了 ρ混合、φ混合、ψ混合样本线性模型中回归参数M估计的强相合性 ,在条件不变的情况下 ,获得与独立情形一样的M估计是强相合的充分条件 ,推广了文 [1 ]定理 2 . 相似文献
69.
Testing goodness of fit for the distribution of errors in multivariate linear models 总被引:2,自引:0,他引:2
M.D. Jimnez Gamero J. Muoz García R. Pino Mejías 《Journal of multivariate analysis》2005,95(2):301-322
In this paper, to test goodness of fit to any fixed distribution of errors in multivariate linear models, we consider a weighted integral of the squared modulus of the difference between the empirical characteristic function of the residuals and the characteristic function under the null hypothesis. We study the limiting behaviour of this test statistic under the null hypothesis and under alternatives. In the asymptotics, the rank of the design matrix is allowed to grow with the sample size. 相似文献
70.
František Toman Ludvík Beneš 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):231-236
Differential molar adsorption enthalpies (DMAE) were determined by gas chromatographic measurements of specific retention
volume of vapors on the surface of two forms of Mg–Al hydrotalcite. A linear dependence of the DMAE on the number of the carbon
atoms in hydrocarbons was observed for both form of hydrotalcite. The dependence of the differential molar adsorption enthalpies
on the number of chlorine atoms in organic molecules is discussed. A linear dependence of DMAE on the molecular weight of
chloroderivatives of methane and ethylene on the basic form in an order monochloromethane < dichloromethane < trichloromethane
or vinylidene chloride < 1,1-dichloroethylene < trichloroethylene was found. 相似文献