全文获取类型
收费全文 | 16349篇 |
免费 | 1471篇 |
国内免费 | 1560篇 |
专业分类
化学 | 3664篇 |
晶体学 | 226篇 |
力学 | 1925篇 |
综合类 | 258篇 |
数学 | 10774篇 |
物理学 | 2533篇 |
出版年
2024年 | 35篇 |
2023年 | 165篇 |
2022年 | 197篇 |
2021年 | 282篇 |
2020年 | 392篇 |
2019年 | 371篇 |
2018年 | 346篇 |
2017年 | 419篇 |
2016年 | 457篇 |
2015年 | 342篇 |
2014年 | 678篇 |
2013年 | 1173篇 |
2012年 | 820篇 |
2011年 | 951篇 |
2010年 | 936篇 |
2009年 | 1054篇 |
2008年 | 1121篇 |
2007年 | 1203篇 |
2006年 | 967篇 |
2005年 | 893篇 |
2004年 | 794篇 |
2003年 | 848篇 |
2002年 | 691篇 |
2001年 | 552篇 |
2000年 | 526篇 |
1999年 | 457篇 |
1998年 | 417篇 |
1997年 | 344篇 |
1996年 | 298篇 |
1995年 | 251篇 |
1994年 | 220篇 |
1993年 | 148篇 |
1992年 | 144篇 |
1991年 | 110篇 |
1990年 | 101篇 |
1989年 | 76篇 |
1988年 | 77篇 |
1987年 | 54篇 |
1986年 | 67篇 |
1985年 | 93篇 |
1984年 | 53篇 |
1983年 | 29篇 |
1982年 | 60篇 |
1981年 | 45篇 |
1980年 | 30篇 |
1979年 | 25篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Yi Zhan 《应用数学学报(英文版)》1997,13(3):235-242
In [1] we construct a unique bounded Hölder continuous viscosity solution for the nonlinear PDEs with the evolutionp-Laplacian equation and its anisotropic version as typical examples. In this part, we investigate the Lipschitz continuity of the free boundary of viscosity solution and its asymptotic spherical symmetricity, however, this result does not include the anisotropic case.This research is supported by the National Natural Sciences Foundation of China. 相似文献
62.
本文利用Liapunov-Schmidt方法获得了高维自治系统在共振情况下决定周期解个数的分支函数,并通过计算分支函数的主项,分析分支函数的零点,研究了具两对共轭特征根的四维系统多个周期解的共振分支问题. 相似文献
63.
Most of the few known examples of compact Riemannian manifolds with positive sectional curvature are the total space of a
Riemannian submersion. In this article we show that this is true for all known examples, if we enlarge the category to orbifold
fibrations. For this purpose we study all almost free isometric circle actions on positively curved Eschenburg spaces, which
give rise to principle orbifold bundle structures, and we examine in detail their geometric properties. In particular, we
obtain a new family of 6-dimensional orbifolds with positive sectional curvature whose singular locus consists of just two
points.
相似文献
64.
Lei Liu 《Journal of Mathematical Analysis and Applications》2007,328(2):1484-1486
In this note, we generalize the inequality about the trace of positive semidefinite matrix trk(AB)?k(trA)k(trB) to Hilbert space, and obtain a relevant inequality about positive trace class operator. 相似文献
65.
G. N. Merrill 《Journal of Physical Organic Chemistry》2007,20(1):19-29
Ab initio molecular orbital calculations were carried out on epibromohydrin (EBH) and epichlorohydrin (ECH) in an attempt to elucidate their reactivity with respect to a hard nucleophile, hydroxide. These systems were modeled in both the gas phase and a polar solvent under basic conditions. In the gas phase, it was determined that a direct displacement mechanism (nucleophilic attack at the C1 position) was operative for EBH, while an indirect pathway (nucleophilic attack at the C3 position and subsequent intramolecular displacement) was followed for ECH. In an acetone solution, only the indirect displacement mechanism was found to occur. An electrostatic argument is advanced to account for this behavior in polar solution. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
66.
Small‐Angle Neutron Scattering has been performed from poly(ethylene oxide) in deuterated water at temperature ranging from 10 to 80 °C. A simple fitting model was used to obtain a correlation length and a Porod exponent. The correlation length L characterizes the average distance between entanglements in the semidilute region and is proportional to the individual coil sizes in the dilute region. L was found to increase with temperature in the semidilute region but it decreases with temperature in the dilute region. This decrease is the precursor to the single‐chain collapse which applies to very dilute polymer solutions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2196–2200, 2007 相似文献
67.
By using the theory of coincidence degree, we study a kind of periodic solutions to p-Laplacian neutral functional differential equation with multiple deviating arguments, a new result on the existence of periodic solutions is obtained. 相似文献
68.
Henrik Stetkær 《Journal of Functional Analysis》2007,252(1):1-33
We extend results on square integrable representations of a locally compact group to subrepresentations of a representations induced from a character of a closed subgroup. We do so working in the framework of quotient representations of ∗-algebras. 相似文献
69.
利用微分方程的级数求解方法,分析了两端简支的有限长功能梯度圆筒的轴对称稳态热弹性问题,推导出了稳态温度场与应力场的解析解。分析中采用指数函数模型来描述FGM圆筒中材料性能在厚度方向的连续变化,同时忽略温度对材料性能的影响。另外,论文以金属钼和多铝红柱石制成的功能梯度圆筒为例,给出了稳态温度场和应力场的数值结果。 相似文献
70.
An inverse problem of the reconstruction of the right-hand side of the Euler-Darboux equation is studied. This problem is equivalent to the Volterra integral equation of the third kind with the operator of multiplication by a smooth nonincreasing function. Numerical solution of this problem is constructed using an integral representation of the solution of the inverse problem, the regularization method, and the method of quadratures. The convergence and stability of the numerical method is proved. 相似文献