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   972篇
  免费   90篇
  国内免费   22篇
化学   47篇
力学   18篇
综合类   16篇
数学   893篇
物理学   110篇
  2023年   4篇
  2022年   30篇
  2021年   34篇
  2020年   22篇
  2019年   23篇
  2018年   18篇
  2017年   40篇
  2016年   47篇
  2015年   26篇
  2014年   55篇
  2013年   63篇
  2012年   47篇
  2011年   42篇
  2010年   43篇
  2009年   74篇
  2008年   68篇
  2007年   58篇
  2006年   54篇
  2005年   50篇
  2004年   36篇
  2003年   27篇
  2002年   33篇
  2001年   19篇
  2000年   11篇
  1999年   12篇
  1998年   19篇
  1997年   25篇
  1996年   18篇
  1995年   15篇
  1994年   6篇
  1993年   8篇
  1992年   6篇
  1991年   5篇
  1990年   3篇
  1989年   4篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   6篇
  1984年   4篇
  1983年   1篇
  1982年   4篇
  1981年   4篇
  1980年   6篇
  1979年   2篇
  1978年   3篇
  1977年   2篇
  1976年   1篇
  1973年   2篇
排序方式: 共有1084条查询结果,搜索用时 10 毫秒
41.
We study fundamental properties of monotone network enterprises which contain public vertices and have positive and negative costs on edges and vertices. Among the properties studied are the nonemptiness of the core, characterization of nonredundant core constraints, ease of computation of the core and the nucleolus, and cases of decomposition of the core and the nucleolus. Received December 1994/Final version March 1998  相似文献   
42.
The single machine group scheduling problem is considered. Jobs are classified into several groups on the basis of group technology, i.e. jobs of the same group have to be processed jointly. A machine set-up time independent of the group sequence is needed between each two consecutive groups. A schedule specifies the sequence of groups and the sequence of jobs in each group. The quality of a schedule is measured by the criteriaF 1, ...,F m ordered by their relative importance. The objective is to minimize the least important criterionF m subject to the schedule being optimal with respect to the more important criterionF m–1 which is minimized on the set of schedules minimizing criterionF m–2 and so on. The most important criterion isF 1, which is minimized on the set of all feasible schedules. An approach to solve this multicriterion problem in polynomial time is presented if functionsF 1, ...,F m have special properties. The total weighted completion time and the total weighted exponential time are the examples of functionsF 1, ...,F m–1 and the maximum cost is an example of functionF m for which our approach can be applied.The research of the authors was partially supported by a KBN Grant No. 3 P 406 003 05, the Fundamental Research Fund of Belarus, Project N 60-242, and the Deutsche Forschungsgemeinschaft, Project Schema, respectively. The paper was completed while the first author was visiting the University of Melbourne.  相似文献   
43.
A system such as missiles and spare parts of aircraft has to perform a normal operation in a severe environment at any time when it is used. However, the system is in storage for a long time from the delivery to the usage and its reliability goes down with time. Thus, a system in storage should be inspected and maintained at periodic times to hold a higher reliability than is prespecified.The following inspection model is considered: A system has three types of units, where unit 1 is maintained, unit 21 is not maintained but is replaced and unit 22 is neither maintained nor replaced. The system is overhauled if its reliability becomes lower than a prespecified probability. The number of replacements and time until overhaul are derived. Using these results, the average cost is obtained and both an optimal inspection time and an optimal replacement time to minimize it are numerically discussed.  相似文献   
44.
Static and dynamic average polarisabilities and polarisability anisotropies of seven linear non-polar and polar molecules are calculated within the CCS, CC2, and CC3 approximations using a range of medium-sized basis sets: the polarised LPol-n (n = ds, dl, fs, fl), the aug-pc-n (n = 1, 2), the def2-SVPD, and -TZVPD basis sets. Reference values are obtained using a hierarchy of Dunning's (d-)aug-cc-pVXZ (X = D, T, Q, 5) basis sets. The results are discussed together with the available CCSD values in terms of basis set and correlation method errors, and their ratio. Detailed analysis shows that already the def2-SVPD basis set can be used in CCS polarisability calculations. When affordable, the slightly larger aug-pc-1 basis set is recommended, as it leads to significant reduction of basis set error. The def2-TZVPD, LPol-ds, and aug-pc-2 basis sets are optimal choice within the CC2 approximation, with the latter allowing to approach the CC2 basis set limit. The LPol-ds, -dl, and def2-TZVPD sets outperform the aug-cc-pVTZ set in average polarisability CCSD calculations, with the def2-TZVPD being competitive to other reduced-size sets also in determination of polarisability anisotropy. The aug-pc-2 basis is a particularly attractive choice for CCSD, giving the accuracy of aug-cc-pVQZ at a significantly reduced computational cost. The polarisability anisotropy is shown to be more computationally demanding than the average polarisability, in particular with respect to the accuracy of the correlation method and an accurate evaluation of this property requires at least the CCSD model.  相似文献   
45.
丁文杰  黄欢  戴涛  郭海兵 《强激光与粒子束》2019,31(5):056007-1-056007-6
基于核燃料循环政策技术的成熟度,选取了一次通过循环方案(OTC)、单次复用循环方案(TTC)、快堆闭式循环方案(FRC)及混合堆闭式循环方案(HRC)四种典型的核燃料循环方案进行分析。采用平衡物质流模型对不同燃料循环方案的可持续性进行研究,基于平准化电力成本计算方法对不同方案的燃料成本和乏燃料处置成本进行分析。研究结果表明:闭式燃料循环可极大减少核废料产生; 燃料可自持的FRC方案及HRC方案可使用贫铀做燃料而不消耗天然铀; 仅考虑燃料成本和乏燃料处置成本时,HRC方案的经济性最高而TTC方案的经济性最差。  相似文献   
46.
Abbas  SH 《应用数学和力学》1996,17(12):1077-1083
本文讨论了求解密集型线性方程组的两种并行算法。这两种算法都在下上单元(LU)分解。法的基础上使用了前向和后向置换进行的。这些算法在数值上是稳定的,并在顺序平衡机上用各种处理程序进行试验,都得到良好效果。  相似文献   
47.
We consider the spatially homogeneous Landau equation of kinetic theory, and provide a differential inequality for the Wasserstein distance with quadratic cost between two solutions. We deduce some well-posedness results. The main difficulty is that this equation presents a singularity for small relative velocities. Our uniqueness result is the first one in the important case of soft potentials. Furthermore, it is almost optimal for a class of moderately soft potentials, that is for a moderate singularity. Indeed, in such a case, our result applies for initial conditions with finite mass, energy, and entropy. For the other moderately soft potentials, we assume additionally some moment conditions on the initial data. For very soft potentials, we obtain only a local (in time) well-posedness result, under some integrability conditions. Our proof is probabilistic, and uses a stochastic version of the Landau equation, in the spirit of Tanaka [H. Tanaka, Probabilistic treatment of the Boltzmann equation of Maxwellian molecules, Z. Wahrsch. Verw. Geb. 46 (1) (1978-1979) 67-105].  相似文献   
48.
A scheme for probabilistic remotely preparing N-particle d-dimensional equatorial entangled states via entangled swapping with three parties is presented. The quantum channel is composed of N - 1 pairs of bipartite d-dimensional non-maximally entangled states and a tripartite d-dimension non-maximally entangled state. It is shown that the sender can help either of the two receivers to remotely prepare the original state, and the N-particle projective measurement and the generalized Hadamard transformation are needed in this scheme. The total success probability and classical communication cost are calculated.  相似文献   
49.
量子纠缠消相干对确定型远程制备的影响   总被引:1,自引:0,他引:1       下载免费PDF全文
郭振  闫连山  潘炜  罗斌  徐明峰 《物理学报》2011,60(6):60301-060301
研究了两种典型的量子纠缠消相干现象对确定型量子态远程制备方案的影响.首先对该确定型远程制备方案进行了分析,得到该方案确定性和比特消耗情况; 然后通过分析制备过程中纠缠消相干现象对系统的影响得出: 在极化消相干过程中,该系统保真度与目标量子比特在Bloch球上的经度选择无关,仅与目标比特的纬度和消相干的大小有关;在相位消相干中,该系统的保真度不会受到消相干的影响,仅与目标量子态的纬度相关. 关键词: 远程制备 纠缠消相干 通信消耗 保真度  相似文献   
50.
电子束固化树脂基复合材料进展   总被引:7,自引:0,他引:7  
综述了电子束固化树脂基复合材料的树脂基体、电子束固化工艺的优越性、吵固化复合材料在国内外的发展状况以不固化复合材料中存在的一些待解决的问题。  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