全文获取类型
收费全文 | 10242篇 |
免费 | 994篇 |
国内免费 | 659篇 |
专业分类
化学 | 579篇 |
晶体学 | 41篇 |
力学 | 2684篇 |
综合类 | 97篇 |
数学 | 6608篇 |
物理学 | 1886篇 |
出版年
2024年 | 17篇 |
2023年 | 115篇 |
2022年 | 118篇 |
2021年 | 136篇 |
2020年 | 261篇 |
2019年 | 241篇 |
2018年 | 255篇 |
2017年 | 267篇 |
2016年 | 325篇 |
2015年 | 269篇 |
2014年 | 425篇 |
2013年 | 881篇 |
2012年 | 413篇 |
2011年 | 560篇 |
2010年 | 454篇 |
2009年 | 594篇 |
2008年 | 637篇 |
2007年 | 647篇 |
2006年 | 570篇 |
2005年 | 531篇 |
2004年 | 478篇 |
2003年 | 453篇 |
2002年 | 406篇 |
2001年 | 338篇 |
2000年 | 353篇 |
1999年 | 292篇 |
1998年 | 290篇 |
1997年 | 246篇 |
1996年 | 190篇 |
1995年 | 137篇 |
1994年 | 131篇 |
1993年 | 109篇 |
1992年 | 115篇 |
1991年 | 99篇 |
1990年 | 83篇 |
1989年 | 50篇 |
1988年 | 36篇 |
1987年 | 29篇 |
1986年 | 34篇 |
1985年 | 41篇 |
1984年 | 57篇 |
1983年 | 37篇 |
1982年 | 47篇 |
1981年 | 32篇 |
1980年 | 25篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 6篇 |
1973年 | 9篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This paper investigates the existence of positive solutions of a singular boundary value problem with negative exponent similar
to standard Emden-Fowler equation. A necessary and sufficient condition for the existence of C[0, 1] positive solutions as
well as C1[0, 1] positive solutions is given by means of the method of lower and upper solutions with the Schauder fixed point theorem. 相似文献
82.
We prove equivalence of the definitions by the author and by Korevaar and Schoen of the Sobolev classes of mappings of a domain of an arithmetic n-dimensional space to a metric space. 相似文献
83.
Combining layered positional order as smectic order and chirality can generate complex architectures since twist parallel
to the layers is not allowed. This paper will review some new experimental results on different phases resulting from the
competition between smectic positional order and twist orientational order. It concerns the TGBA and the NL*, that is the liquid line phase as well as the SmQ phase. Chiral effects in the isotropic phase will also be discussed. 相似文献
84.
Banach空间二阶周期边值问题解的存在性 总被引:2,自引:0,他引:2
利用一些比较结果,讨论了Banach空间中二阶周期边值问题解的存在性,获得了若干解的存在性与唯一性结果。 相似文献
85.
J. T. Haslinger K. Kunisch G. Peichl 《Computational Optimization and Applications》2003,26(3):231-251
This contribution deals with an efficient method for the numerical realization of the exterior and interior Bernoulli free boundary problems. It is based on a shape optimization approach. The state problems are solved by a fictitious domain solver using boundary Lagrange multipliers. 相似文献
86.
Xian Xu 《Journal of Mathematical Analysis and Applications》2004,291(2):673-689
In this paper, some multiplicity results for positive solutions of some singular semi-positone three-point boundary value problem be obtained by using the fixed point index method. 相似文献
87.
High-resolution Fourier transform spectra of CH3OH have been investigated in the infrared region from 930 to 1450 cm−1 in order to map the torsion-rotation energy manifolds associated with the ν7 in-plane CH3 rock, the ν11 out-of-plane CH3 rock, and the ν6 OH bend. Upper-state term values have been determined from the assigned spectral subbands, and have been fitted to power-series expansions to obtain substate origins and effective B-values for the three modes. The substate origins have been grouped into related families according to systematic trends observed in the torsion-vibration energy map, but there are substantial differences from the traditional torsional patterns. There appears to be significant torsion-mediated spectral mixing, and a variety of “forbidden” torsional combination subbands with |Δυt|>1 have been observed, where υt denotes the torsional quantum number (equivalent to υ12). For example, coupling of the (υ6,υt)=(1,0) OH bend to nearby torsionally excited (υ7,υt)=(1,1) CH3-rock and (υ8,υt)=(1,1) CO-stretch states introduces (υ6,υt)=(1,0)←(0,1) subbands into the spectrum and makes the ν7+ν12−ν12 torsional hot band stronger than the ν7 fundamental. The results suggest a picture of strong coupling among the OH-bending, CH3-rocking, and CO-stretching modes that significantly modifies the traditional energy structure and raises interesting and provocative questions about the torsion-vibration identity of a number of the observed states. 相似文献
88.
The periodic precipitation pattern formation in gelatinous media is interpreted as a moving boundary problem. The time law,
spacing law and width law are revisited on the basis of the new scenario. The explicit dependence of the geometric structure
on the initial concentrations of the reactants is derived. Matalon—Packter law, which relates the spacing coefficient with
the initial concentrations is reformulated removing many ambiguities and impractical parameters. Experimental results are
discussed to establish the significance of moving boundary concept in the diffusion controlled pattern forming systems 相似文献
89.
In this paper, we exhibit a unified treatment of the mixed initial boundary value problem for second order (in time) parabolic linear differential equations in Banach spaces, whose boundary conditions are of a dynamical nature. Results regarding existence, uniqueness, continuous dependence (on initial data) and regularity of classical and strict solutions are established. Moreover, several examples are given as samples for possible applications.
90.
In this paper we give necessary and sufficient conditions for the existence of a C>
0-semigroup in L
1(I) (I real interval) generated by a second-order differential operator when suitable boundary conditions at the endpoints are imposed. 相似文献