全文获取类型
收费全文 | 3084篇 |
免费 | 264篇 |
国内免费 | 326篇 |
专业分类
化学 | 292篇 |
晶体学 | 2篇 |
力学 | 321篇 |
综合类 | 116篇 |
数学 | 2339篇 |
物理学 | 604篇 |
出版年
2024年 | 6篇 |
2023年 | 16篇 |
2022年 | 44篇 |
2021年 | 41篇 |
2020年 | 63篇 |
2019年 | 44篇 |
2018年 | 58篇 |
2017年 | 72篇 |
2016年 | 102篇 |
2015年 | 64篇 |
2014年 | 124篇 |
2013年 | 191篇 |
2012年 | 172篇 |
2011年 | 205篇 |
2010年 | 184篇 |
2009年 | 225篇 |
2008年 | 218篇 |
2007年 | 240篇 |
2006年 | 212篇 |
2005年 | 174篇 |
2004年 | 148篇 |
2003年 | 157篇 |
2002年 | 117篇 |
2001年 | 114篇 |
2000年 | 93篇 |
1999年 | 93篇 |
1998年 | 97篇 |
1997年 | 73篇 |
1996年 | 59篇 |
1995年 | 34篇 |
1994年 | 37篇 |
1993年 | 31篇 |
1992年 | 31篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1971年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有3674条查询结果,搜索用时 15 毫秒
131.
A new iterative method for finding a zero of m-accretive operators is proposed. This method, involving a so-called perturbed mapping, provides a way to construct sunny nonexpansive retractions. Several strong convergence theorems for this method are established in a Banach space that is either uniformly smooth or reflexive with a weakly continuous duality map. 相似文献
132.
Nest代数上的在零点广义可导映射 总被引:4,自引:0,他引:4
设A为B(H)的子代数, 是A到B(H)的线性映射,我们说 在0点广义可导(广义双边可导),如果对任意的S,T∈A且ST=0(ST=0或TS=0),有 (ST)= (S)T+S (T)-S (I)T.本文主要得到如下结果:(1)有限Nest代数上的每个范数拓扑连续的在0点广义可导的线性映射是广义内导子;(2)若N是完备Nest且H_ H,则algN上的每个范数拓扑连续的在0点广义双边可导的线性映射是广义内导子. 相似文献
133.
研究了带约束条件集值优化问题近似Henig有效解集的连通性.在实局部凸Hausdorff空间中,讨论了可行域为弧连通紧的,目标函数为C-弧连通的条件下,带约束条件集值优化问题近似Henig有效解集的存在性和连通性.并给出了带约束条件集值优化问题近似Henig有效解集的连通性定理. 相似文献
134.
135.
Zbigniew Jelonek 《Proceedings of the American Mathematical Society》2003,131(5):1361-1367
Let be a polynomial of degree . Assume that the set there is a sequence s.t. and is finite. We prove that the set of generalized critical values of (hence in particular the set of bifurcation points of ) has at most points. Moreover, We also compute the set effectively.
136.
一致凸Banach空间中渐近非扩张映象的几乎轨道的渐近行为 总被引:1,自引:0,他引:1
设X是有Fréchet可微范数的一致凸Banach空间,C是X的有界闭凸子集,T:C→C是一个渐近非扩张映象.证明了,如果{xn:n≥1}是T的几乎轨道,则序列{x0}弱几乎收敛到集合∩from∞to(n=1)co{xi:i≥n}∩F(T)的唯一点,其中,F(T)是T的不动点集. 相似文献
137.
138.
Nano-mechanical mapping by atomic force microscopy has been developed as an useful application to measure mechanical properties of soft materials at nanometer scale. To date, the Hertzian theory was used for analyzing force-distance curves as the simplest model among several contact mechanics between elastic bodies. However, the preexisting methods based on this theory do not consider the adhesive interaction in principle, which cannot be neglected in the ambient condition. A new analytical method was introduced to estimate the elasticity and the adhesive energy simultaneously by means of the JKR theory, describing adhesive contact between elastic materials. Poly(dimethylsiloxane) (PDMS) and isobutylene-co-isoprene rubber (IIR) were analyzed to verify the applicable limit of the JKR analysis. For elastic samples such as PDMS, the force-deformation plots obtained experimentally were consistent with JKR theoretical curves. Meanwhile, for viscoelastic samples, especially for IIR, the experimental plots revealed large deviations from JKR curves depending on scanning velocity and maximum loading force. Some nano-rheological arguments were employed based on the difference between these specimens. 相似文献
139.
Magnetic resonance imaging (MRI) is a well-known technique in medical diagnosis and materials science. In the more specialized arena of laboratory-scale petrophysical rock core analysis, the role of MRI has undergone a substantial change in focus over the last three decades. Initially, alongside the continual drive to exploit higher magnetic field strengths in MRI applications for medicine and chemistry, the same trend was followed in core analysis. However, the spatial resolution achievable in heterogeneous porous media is inherently limited due to the magnetic susceptibility contrast between solid and fluid. As a result, imaging resolution at the length-scale of typical pore diameters is not practical and so MRI of core-plugs has often been viewed as an inappropriate use of expensive magnetic resonance facilities. Recently, there has been a paradigm shift in the use of MRI in laboratory-scale core analysis. The focus is now on acquiring data in the laboratory that are directly comparable to data obtained from magnetic resonance well-logging tools (i.e., a common physics of measurement). To maintain consistency with well-logging instrumentation, it is desirable to measure distributions of transverse (T2) relaxation time–the industry-standard metric in well-logging–at the laboratory-scale. These T2 distributions can be spatially resolved over the length of a core-plug. The use of low-field magnets in the laboratory environment is optimal for core analysis not only because the magnetic field strength is closer to that of well-logging tools, but also because the magnetic susceptibility contrast is minimized, allowing the acquisition of quantitative image voxel (or pixel) intensities that are directly scalable to liquid volume. Beyond simple determination of macroscopic rock heterogeneity, it is possible to utilize the spatial resolution for monitoring forced displacement of oil by water or chemical agents, determining capillary pressure curves, and estimating wettability. The history of MRI in petrophysics is reviewed and future directions considered, including advanced data processing techniques such as compressed sensing reconstruction and Bayesian inference analysis of under-sampled data. Although this review focuses on rock core analysis, the techniques described are applicable in a wider context to porous media in general, such as cements, soils, ceramics, and catalytic materials. 相似文献
140.
Toshio Matsushima 《Journal of Mathematical Analysis and Applications》2003,285(2):691-707
Let Ω be a domain of . As a study of boundary behavior of functions and maps in Ω, we consider “the linear cluster set,” which is the cluster set along segment terminating at a boundary point of Ω. We prove that there exist bounded holomorphic functions and maps defined in Ω which have the linear cluster sets of positive measure at every point of a discrete subset of the boundary of Ω under some conditions. 相似文献