首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3216篇
  免费   416篇
  国内免费   271篇
化学   707篇
晶体学   29篇
力学   480篇
综合类   50篇
数学   1194篇
物理学   1443篇
  2024年   4篇
  2023年   33篇
  2022年   53篇
  2021年   76篇
  2020年   95篇
  2019年   111篇
  2018年   100篇
  2017年   111篇
  2016年   117篇
  2015年   82篇
  2014年   120篇
  2013年   277篇
  2012年   122篇
  2011年   134篇
  2010年   103篇
  2009年   179篇
  2008年   131篇
  2007年   144篇
  2006年   198篇
  2005年   147篇
  2004年   150篇
  2003年   144篇
  2002年   144篇
  2001年   123篇
  2000年   125篇
  1999年   109篇
  1998年   85篇
  1997年   69篇
  1996年   55篇
  1995年   58篇
  1994年   48篇
  1993年   54篇
  1992年   44篇
  1991年   33篇
  1990年   41篇
  1989年   30篇
  1988年   45篇
  1987年   39篇
  1986年   29篇
  1985年   24篇
  1984年   18篇
  1983年   11篇
  1982年   20篇
  1981年   13篇
  1980年   7篇
  1979年   8篇
  1978年   16篇
  1977年   5篇
  1976年   5篇
  1973年   6篇
排序方式: 共有3903条查询结果,搜索用时 0 毫秒
991.
In this paper we examine a nonlinear elliptic problem driven by the p-Laplacian differential operator and with a potential function which is only locally Lipschitz, not necessarily C1 (hemivariational inequality). Using the nonsmooth critical point theory of Chang, we obtain two strictly positive solutions. One solution is obtained by minimization of a suitable modification of the energy functional. The second solution is obtained by generalizing a result of Brezis-Nirenberg about the local C10-minimizers versus the local H10-minimizers of a C1-functional. Mathematics Subject Classification (2000) 35J50, 35J85, 35R70  相似文献   
992.
In this paper, we are interested in the nonlinear Schrödinger equation with non‐local regional diffusion (1) where 0 < α < 1 and is a variational version of the regional Laplacian, whose range of scope is a ball with radius ρ(x) > 0. The novelty of this paper is that, assuming f is of subquadratic growth as |u|→+, we show that 1 possesses infinitely many solutions via the genus properties in critical point theory. Furthermore, if f(x,u) = γa(x)|u|γ ? 1, where is a nonincreasing radially symmetric function, then the solution of 1 is radially symmetric. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
993.
沈洁琼  何平  李海艳 《数学杂志》2015,35(4):945-951
本文研究了一类修旧非新的两参数预防维修策略.在预防维修依赖于基准可靠度R的条件下,利用系统的相关可靠性指标建立了平均费用关于R和N(预防维修次数上限)的函数关系.进一步找到了该函数的最小值点,即得到了最优策略(R,N)*.同时通过实例说明了本文的维修策略优于文献[8].  相似文献   
994.
We study existence and multiplicity of solutions of the following nonlocal ‐Kirchhoff equation with critical exponent, via truncation argument on the Sobolev space with variable exponent, where Ω is a bounded smooth domain of , , M, f are continuous functions, , and are real parameter.  相似文献   
995.
We present exact results for several universal parameters of the tricritical O(n) model in two dimensions. The results apply to the range −2⩽n⩽3/2, and include the central charge and three scaling dimensions, associated with temperature, magnetic field and the introduction of an interface. Since these results are based on an extrapolation of known relations between the O(n) and the Potts model, they cannot be considered as rigorous. For this reason, we perform an accurate numerical analysis of the central charge and the critical exponents. This analysis, which is based on transfer-matrix calculations on the honeycomb lattice, is in a full and precise agreement with the theoretical predictions.   相似文献   
996.
Holographic s‐wave superconductors with nonlinear arcsin‐electrodynamics in the background of Schwarzschild anti‐de Sitter black holes are investigated. The analytical Sturm–Liouville eigenvalue problem is explored and the scalar and electromagnetic fields are assumed not to influence the background metric (the probe limit). The critical temperatures of phase transitions depending on the parameter of the model are obtained. It is shown that in this case, the condensation formation becomes easier compared to Born–Infeld nonlinear electrodynamics. The critical exponent near the critical temperature is calculated, which is 1/2. With the help of the matching method, analytic expressions for the condensation value and the critical temperature are derived. The real and imaginary parts of the conductivity in the model, making use of an analytical method, are computed.  相似文献   
997.
Shu He  Xiaofeng Luo 《中国物理C(英文版)》2018,42(10):104001-104001
We performed systematic studies on the effects of event-by-event efficiency fluctuations on efficiency correction for cumulant analysis in relativistic heavy-ion collision experiments. Experimentally, particle efficiencies of events measured under different experimental conditions should be different. For fluctuation measurements, the final event-by-event multiplicity distributions should be the superposed distributions of various type of events measured under different conditions. We demonstrate efficiency fluctuation effects using numerical simulation, in which we construct an event ensemble consisting of events with two different efficiencies. By using the mean particle efficiencies, we find that the efficiency corrected cumulants show large deviations from the original inputs when the discrepancy between the two efficiencies is large. We further studied the effects of efficiency fluctuations for the cumulants of net-proton distributions by implementing the UrQMD events of Au+Au collisions at sNN~(1/2) = 7.7 GeV in a realistic STAR detector acceptance. We consider the unequal efficiency in two sides of the Time Projection Chamber(TPC), multiplicity dependent efficiency, and the event-by-event variations of the collision vertex position along the longitudinal direction(V_z). When the efficiencies fluctuate dramatically within the studied event sample,the effects of efficiency fluctuations have significant impacts on the efficiency corrections of cumulants with the mean efficiencies. We find that this effect can be effectively suppressed by binning the entire event ensemble into various sub-event samples, in which the efficiency variations are relatively small. The final efficiency corrected cumulants can be calculated from the weighted average of the corrected factorial moments of the sub-event samples with the mean efficiencies.  相似文献   
998.
余学才  叶玉堂  程琳 《物理学报》2006,55(2):551-554
基于最小动量态上的玻色-爱因斯坦凝聚(简称BEC),给出了指数吸引势场中超冷玻色原子气体的势场有效性和势阱中所装载的原子数目极限判据.此判据给出了当所装载的原子数确定时,所需要的势场强度;或势场给定时,所装载的原子数目的极限. 关键词: 玻色-爱因斯坦凝聚 临界温度 最小动量态  相似文献   
999.
The current research is focused on the cooling of a hot moving steel plate by using air atomized spray cooling technique. A new type of coolant, Cu-Al LDH nanofluid, has been prepared and used for heat flux removal. Preparation method of nanofluid and its characteristics has been reported. The cooling effectiveness is reported in terms of cooling rate by varying the concentration of nanofluid in five levels. The results indicate that the cooling rate increases at very low concentration of LDH with respect to base fluid. However, beyond a certain concentration a decreasing trend of cooling rate has been observed.

Abbreviations: CHF: Critical heat flux; HTC: Heat transfer coefficients; LDH:Layered double hydroxide; TEM: Transmission electron microscopy.  相似文献   

1000.
Recently, compressed H2S has been shown to become superconducting at 203 K under a pressure of 155 GPa. One might expect fluctuations to dominate at such temperatures. Using the magnetisation critical current, we determine the ground‐state London penetration depth, λ0=189 nm, and the superconducting energy gap, Δ0=27.8 meV, and find these parameters are similar to those of cuprate superconductors. We also determine the fluctuation temperature scale, K, which shows that, unlike the cuprates, of the hydride is not limited by fluctuations. This is due to its three dimensionality and suggests the search for better superconductors should refocus on three‐dimensional systems where the inevitable thermal fluctuations are less likely to reduce the observed .

  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号