全文获取类型
收费全文 | 4358篇 |
免费 | 832篇 |
国内免费 | 853篇 |
专业分类
化学 | 2658篇 |
晶体学 | 85篇 |
力学 | 541篇 |
综合类 | 49篇 |
数学 | 326篇 |
物理学 | 2384篇 |
出版年
2024年 | 20篇 |
2023年 | 57篇 |
2022年 | 146篇 |
2021年 | 145篇 |
2020年 | 132篇 |
2019年 | 142篇 |
2018年 | 122篇 |
2017年 | 180篇 |
2016年 | 185篇 |
2015年 | 167篇 |
2014年 | 232篇 |
2013年 | 361篇 |
2012年 | 308篇 |
2011年 | 322篇 |
2010年 | 252篇 |
2009年 | 328篇 |
2008年 | 311篇 |
2007年 | 316篇 |
2006年 | 253篇 |
2005年 | 236篇 |
2004年 | 235篇 |
2003年 | 194篇 |
2002年 | 173篇 |
2001年 | 160篇 |
2000年 | 157篇 |
1999年 | 140篇 |
1998年 | 134篇 |
1997年 | 102篇 |
1996年 | 87篇 |
1995年 | 69篇 |
1994年 | 61篇 |
1993年 | 52篇 |
1992年 | 57篇 |
1991年 | 30篇 |
1990年 | 27篇 |
1989年 | 23篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 18篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1980年 | 3篇 |
1979年 | 13篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1974年 | 2篇 |
1973年 | 7篇 |
1957年 | 2篇 |
排序方式: 共有6043条查询结果,搜索用时 62 毫秒
1.
Yuta Yamamoto Shogo Nakano Fumio Seki Yasuteru Shigeta Sohei Ito Hiroaki Tokiwa Makoto Takeda 《Molecules (Basel, Switzerland)》2021,26(5)
Infection of hosts by morbilliviruses is facilitated by the interaction between viral hemagglutinin (H-protein) and the signaling lymphocytic activation molecule (SLAM). Recently, the functional importance of the n-terminal region of human SLAM as a measles virus receptor was demonstrated. However, the functional roles of this region in the infection process by other morbilliviruses and host range determination remain unknown, partly because this region is highly flexible, which has hampered accurate structure determination of this region by X-ray crystallography. In this study, we analyzed the interaction between the H-protein from canine distemper virus (CDV-H) and SLAMs by a computational chemistry approach. Molecular dynamics simulations and fragment molecular orbital analysis demonstrated that the unique His28 in the N-terminal region of SLAM from Macaca is a key determinant that enables the formation of a stable interaction with CDV-H, providing a basis for CDV infection in Macaca. The computational chemistry approach presented should enable the determination of molecular interactions involving regions of proteins that are difficult to predict from crystal structures because of their high flexibility. 相似文献
2.
A model is developed for the formation and propagation of cracks in a material sample that is heated at its top surface, pyrolyses, and then thermally degrades to form char. In this work the sample is heated uniformly over its entire top surface by a hypothetical flame (a heat source). The pyrolysis mechanism is described by a one-step overall reaction that is dependent nonlinearly on the temperature (Arrhenius form). Stresses develop in response to the thermal degradation of the material by means of a shrinkage strain caused by local mass loss during pyrolysis. When the principal stress exceeds a prescribed threshold value, the material forms a local crack. Cracks are found to generally originate at the surface in response to heating, but occasionally they form in the bulk, away from ever-changing material boundaries. The resulting cracks evolve and form patterns whose characteristics are described. Quantities examined in detail are: the crack spacing in the pyrolysis zone; the crack length evolution; the formation and nature of crack loops which are defined as individual cracks that have joined to form loops that are disconnected from the remaining material; the formation of enhanced pyrolysis area; and the impact of all of the former quantities on mass flux. It is determined that the mass flux from the sample can be greatly enhanced over its nominal (non-cracking) counterpart. The mass efflux profile qualitatively resembles those observed in Cone Calorimeter tests. 相似文献
3.
4.
Volker Elling. 《Mathematics of Computation》2006,75(256):1721-1733
A particular case of initial data for the two-dimensional Euler equations is studied numerically. The results show that the Godunov method does not always converge to the physical solution, at least not on feasible grids. Moreover, they suggest that entropy solutions (in the weak entropy inequality sense) are not well posed.
5.
用密耦方法计算了非对称同位素替代分子与氦原子碰撞(He-HD,HT,DT)转动激发,当入射能量E=0.3 eV时,得到了上述碰撞体系的微分散射截面或角分布.基于上述理论计算,讨论了原子与双原子分子碰撞的同位素效应. 相似文献
6.
S. K. Godunov V. T. Zhukov O. B. Feodoritova 《Computational Mathematics and Mathematical Physics》2006,46(6):971-982
An algorithm is constructed for calculating invariant subspaces of symmetric hyperbolic systems arising in electromagnetic, acoustic, and elasticity problems. Discrete approximations are calculated for subspaces that correspond to minimal eigenvalues and smooth eigenfunctions. Difficulties related to the presence of an infinite-dimensional kernel in the differential operator are successfully handled. The efficiency of the algorithm is demonstrated using acoustics equations. 相似文献
7.
What Is Its Real Existing Form?——Theoretical and Experimental Studies on 2-Mercaptobenzothiazole 总被引:1,自引:0,他引:1
1 INTRODUCTION The study of heterocyclic molecules with aroma- tic rings and their absorptions on metals is of con- siderable importance from both theoretical and te- chnological points of view. These molecules are in- teresting because of their applications as corrosion inhibitors and flotation collectors, and their abilities to form self-assembly layers[1]. 2-Mercaptobenzo- thiazole (C7H5NS2, in the following MBT) is an important heterocyclic molecule, which can be used as corrosion … 相似文献
8.
9.
Sh. M. Aitaliev 《International Applied Mechanics》2004,40(10):1065-1091
Some results on underground structures obtained by Kazakh mechanicians are reviewed. The review covers a period of the last forty years. Also results on the mechanics of special objects are discussed.Translated from Prikladnaya Mekhanika, Vol. 40, No. 10, pp. 3–36, October 2004. 相似文献
10.
Using the DFT/B3LYP method with a 6-31G(d) basis set, the structure, normal vibration frequencies, and the absolute band intensities in the IR spectra of the chlorin molecule and its four symmetric isotopomers have been calculated. Scaling of the force field by the Pulay method in independent and natural coordinates has been carried out. A method for obtaining effective force fields without using experimental data on the fundamental vibration frequencies is proposed. By comparing the vibration modes and constructing special matrices, complete assignment of the fundamental frequencies of porphin and chlorin has been carried out. It has been shown that the majority of porphin macroring vibrations upon pyrrolenine ring hydrogenation are frequency-characteristic and only 12 vibrations change considerably. A frequency correlation with regard for the mode transition between chlorin and all its isotopomers under consideration has been established. Comparative analysis of the force fields of porphin and chlorin in dependent natural coordinates has revealed the unique nonlocal character of the change in force constants of the macroring upon hydrogenation of one pyrrolenine ring. Modeling of the IR spectra of chlorin and its isotopomers has been performed. Assignment and interpretation of the normal vibrations of the molecules under consideration have been carried out. 相似文献