全文获取类型
收费全文 | 17051篇 |
免费 | 3138篇 |
国内免费 | 2792篇 |
专业分类
化学 | 9633篇 |
晶体学 | 177篇 |
力学 | 1528篇 |
综合类 | 146篇 |
数学 | 1856篇 |
物理学 | 9641篇 |
出版年
2024年 | 72篇 |
2023年 | 239篇 |
2022年 | 540篇 |
2021年 | 577篇 |
2020年 | 751篇 |
2019年 | 585篇 |
2018年 | 572篇 |
2017年 | 626篇 |
2016年 | 757篇 |
2015年 | 692篇 |
2014年 | 975篇 |
2013年 | 1473篇 |
2012年 | 1021篇 |
2011年 | 1119篇 |
2010年 | 987篇 |
2009年 | 1188篇 |
2008年 | 1177篇 |
2007年 | 1215篇 |
2006年 | 1168篇 |
2005年 | 903篇 |
2004年 | 816篇 |
2003年 | 761篇 |
2002年 | 620篇 |
2001年 | 547篇 |
2000年 | 527篇 |
1999年 | 472篇 |
1998年 | 413篇 |
1997年 | 332篇 |
1996年 | 272篇 |
1995年 | 239篇 |
1994年 | 209篇 |
1993年 | 157篇 |
1992年 | 130篇 |
1991年 | 130篇 |
1990年 | 87篇 |
1989年 | 84篇 |
1988年 | 76篇 |
1987年 | 65篇 |
1986年 | 61篇 |
1985年 | 58篇 |
1984年 | 41篇 |
1983年 | 23篇 |
1982年 | 37篇 |
1981年 | 37篇 |
1980年 | 33篇 |
1979年 | 29篇 |
1978年 | 13篇 |
1977年 | 22篇 |
1976年 | 12篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
71.
本在Glover—Klingman算法及最小费用支撑树对策的基础上,讨论了最小费用k度限制树对策问题.利用威胁、旁支付理论制订了两种规则,并利用优超、策略等价理论分别给出了在这两种规则下最小费用k度限制树对策核心中的解,从而证明了在这两种规则下其核心非空. 相似文献
72.
A set of invariants describing the limit regimes of braking disk-type wound composite flywheels is suggested. The limit regime is determined by using a linear failure criterion. It is shown that, for generating short-time impulses of very high power, a set of small identical flywheels is more effective than one large flywheel with an equivalent mass. Particular examples illustrating the theory considered are discussed. 相似文献
73.
We use methods of nonequilibrium statistical thermodynamics to investigate two dissipative processes in solids. We find the electron energy losses of a particle moving in a planar channeling regime and the sound absorption coefficient in metals under electron impurity scattering. The oscillator model is used to analyze the contribution from the effect of electron entrainment by a moving scattering center to the total dissipated energy. We investigate the frequency and temperature dependence of energy losses and also the dependence of the absorption coefficient on the sound wave vector. 相似文献
74.
Taking both the heterogeneous catalytic processes, including the surface formation of particles with excited internal degrees of freedom, and the processes of multicomponent diffusion and heat transfer in the MESOX apparatus fully into account makes it possible to obtain a recombination coefficient and an accommodation coefficient of the oxygen-atoms-on-quartz recombination energy which are in good agreement with the experimental data. The heterogeneous catalysis model constructed can be used effectively for predicting the heat fluxes to the surface of reentry vehicles on their entry into the Earth’s atmosphere. 相似文献
75.
基于突变论的林火蔓延分析 总被引:8,自引:0,他引:8
在对森林火灾进行能量和质量守恒分析的基础上,把尖点突变模型应用于森林火灾蔓延的预测,使突变理论在 森林火灾的模型中从理论上有了初步的应用。文中计算了林火发生突变时的一些分歧点,分析了林火突变的特点和变化规 律。 相似文献
76.
Image potential resonances on the Sn/Ge(1 1 1) α-phase are investigated by two closely related methods: specular electron reflection and so-called selective electron scattering. Electrons from image resonances are detected on this surface at 120 and 300 K, i.e. below and above the phase transition at about 200 K. The dispersion of the image resonances reveals at these two temperatures equivalent effective electron masses, which are characteristic for this type of electronic surface states. The results of the two methods are consistent according to the similarity of the scattering processes. Changes in the loss peak intensity with the annealing temperature are assigned to the surface quality and are reflected by characteristic photoemission intensities. 相似文献
77.
This paper concerns methods by which a trusted authority can distribute keys and/or broadcast a message over a network, so that each member of a privileged subset of users can compute a specified key or decrypt the broadcast message. Moreover, this is done in such a way that no coalition is able to recover any information on a key or broadcast message they are not supposed to know. The problems are studied using the tools of information theory, so the security provided is unconditional (i.e., not based on any computational assumption).In a recent paper st95a, Stinson described a method of constructing key predistribution schemes by combining Mitchell-Piper key distribution patterns with resilient functions; and also presented a construction method for broadcast encryption schemes that combines Fiat-Naor key predistribution schemes with ideal secret sharing schemes. In this paper, we further pursue these two themes, providing several nice applications of these techniques by using combinatorial structures such as orthogonal arrays, perpendicular arrays, Steiner systems and universal hash families. 相似文献
78.
79.
黎勇 《数学物理学报(B辑英文版)》2007,27(2):437-448
In this article, two relaxation time limits, namely, the momentum relaxation time limit and the energy relaxation time limit are considered. By the compactness argument, it is obtained that the smooth solutions of the multidimensional nonisentropic Euler-Poisson problem converge to the solutions of an energy transport model or a drift diffusion model, respectively, with respect to different time scales. 相似文献
80.
讨论了带有背景矢量场的动力学标量场作为暗能量在闭宇宙的情形下的演化. 选取适当的标量场势函数后, 在得到的暗能量有效状态方程中, 参数w在红移z≈0.2处可以越过-1, 而且在z≈1.7处宇宙从减速膨胀的状态转变为加速膨胀状态, 这与最近的宇宙学观测相符. 相似文献