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   341篇
  免费   2篇
  国内免费   3篇
化学   67篇
力学   2篇
数学   47篇
物理学   230篇
  2020年   5篇
  2018年   4篇
  2016年   2篇
  2015年   1篇
  2014年   3篇
  2013年   11篇
  2012年   7篇
  2011年   5篇
  2010年   4篇
  2009年   2篇
  2008年   31篇
  2007年   36篇
  2006年   29篇
  2005年   34篇
  2004年   35篇
  2003年   23篇
  2002年   13篇
  2001年   5篇
  2000年   5篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1992年   2篇
  1991年   2篇
  1990年   18篇
  1989年   8篇
  1988年   2篇
  1987年   5篇
  1986年   6篇
  1985年   6篇
  1984年   1篇
  1982年   2篇
  1981年   5篇
  1980年   1篇
  1979年   1篇
  1978年   5篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1974年   1篇
  1973年   1篇
  1971年   1篇
  1969年   1篇
  1939年   2篇
  1938年   1篇
  1936年   2篇
  1931年   1篇
排序方式: 共有346条查询结果,搜索用时 171 毫秒
41.
42.
43.
When social groups compete for members, the resulting dynamics may be understandable with mathematical models. We demonstrate that a simple ordinary differential equation (ODE) model is a good fit for religious shift by comparing it to a new international data set tracking religious nonaffiliation. We then generalize the model to include the possibility of nontrivial social interaction networks and examine the limiting case of a continuous system. Analytical and numerical predictions of this generalized system, which is robust to polarizing perturbations, match those of the original ODE model and justify its agreement with real-world data. The resulting predictions highlight possible causes of social shift and suggest future lines of research in both physics and sociology.  相似文献   
44.
We present a measurement of the partial branching fractions and mass spectra of the exclusive radiative penguin processes B-->Kpipigamma in the range m(Kpipi)<1.8 GeV/c(2). We reconstruct four final states: K(+)pi(-)pi(+)gamma, K(+)pi(-)pi(0)gamma, K(S)(0)pi(-)pi(+)gamma, and K(S)(0)pi(+)pi(0)gamma, where K(S)(0)-->pi(+)pi(-). Using 232 x 10(6) e(+)e(-)-->BB events recorded by the BABAR experiment at the SLAC PEP-II asymmetric-energy storage ring, we measure the branching fractions B(B(+)-->K(+)pi(-)pi(+)gamma)=[2.95+/-0.13(stat)+/-0.20(syst)] x 10(-5), B(B(0)-->K(+)pi(-)pi(0)gamma)=[4.07+/-0.22(stat)+/-0.31(syst)] x 10(-5), B(B(0)-->K(0)pi(+)pi(-)gamma)=[1.85+/-0.21(stat)+/-0.12(syst)] x 10(-5), and B(B(+)-->K(0)pi(+)pi(0)gamma)=[4.56+/-0.42(stat)+/-0.31(syst)] x 10(-5).  相似文献   
45.
We present the results of searches for decays of B mesons to final states with a b1 meson and a charged pion or kaon. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 382x10(6) BB[over ] pairs produced in e+e- annihilation. The results for the branching fractions are, in units of 10(-6), B(B+-->b1(0)pi+)=6.7+/-1.7+/-1.0, B(B+-->b1(0)K+)=9.1+/-1.7+/-1.0, B(B0-->b1(-/+)pi(+/-))=10.9+/-1.2+/-0.9, and B(B0-->b1(-)K+)=7.4+/-1.0+/-1.0, with the assumption that B(b1-->omega pi)=1. We also measure charge and flavor asymmetries A(ch)(B+-->b1(0)pi+)=0.05+/-0.16+/-0.02, Ach(B+-->b1(0)K+)=-0.46+/-0.20+/-0.02, A(ch)(B0-->b1(-/+)pi(+/-))=-0.05+/-0.10+/-0.02, C(B0-->b1(-/+)pi(+/-))=-0.22+/-0.23+/-0.05, DeltaC(B0-->b1(-/+)pi(+/-))=-1.04+/-0.23+/-0.08, and A(ch)(B0-->b1(-)K+)=-0.07+/-0.12+/-0.02. The first error quoted is statistical, and the second systematic.  相似文献   
46.
We perform an amplitude analysis of B+/--->phi(1020)K*(892)+/- decay with a sample of about 384 x 10(6) BB[over ] pairs recorded with the BABAR detector. Overall, twelve parameters are measured, including the fractions of longitudinal fL and parity-odd transverse f perpendicular amplitudes, branching fraction, strong phases, and six parameters sensitive to CP violation. We use the dependence on the Kpi invariant mass of the interference between the JP=1(-) and 0+ Kpi components to resolve the discrete ambiguity in the determination of the strong and weak phases. Our measurements of fL=0.49+/-0.05+/-0.03, f perpendicular=0.21+/-0.05+/-0.02, and the strong phases point to the presence of a substantial helicity-plus amplitude from a presently unknown source.  相似文献   
47.
庞琳勇  刘永  Dan Abrams 《实验力学》2007,22(3):295-304
此篇论文将介绍一个用于半导体光罩上图样设计以及可用于实际生产的光刻反向计算技术(ILT)。在论文中将讨论有关ILT的最新发展,包括在超成像极限协助图样(SRAF)的生成,可增加制程宽容度的ILT,以及如何生成满足光罩生产标准的图样等方面。从内部的研究结果和客户的使用结果可以看出,ILT已经不再只是一种用于研究的工具,而是已经可以用于先进半导体制程的大规模生产。在对各个环节优化之后,ILT可以增加制程的宽容度,同时将光罩的成本控制在可以接受的水平。  相似文献   
48.
Previous work has considered the problem of swiftly traversing a marked traversal-medium where the marks represent probabilities that associated local regions are traversable, further supposing that the traverser is equipped with a dynamic capability to disambiguate these regions en route. In practice, however, the marks are given by a noisy sensor, and are only estimates of the respective probabilities of traversability. In this paper, we investigate the performance of disambiguation protocols that utilize such sensor readings. In particular, we investigate the difference in performance when a disambiguation protocol employs various sensors ranked by their estimation quality. We demonstrate that a superior sensor can yield superior traversal performance—so called Sensor Information Monotonicity. In so doing, we provide to the decision-maker the wherewithal to quantitatively assess the advantage of a superior (and presumably more expensive) sensor in light of the associated improvement in performance.  相似文献   
49.
We report here on a study of vertically aligned TiO(2) nanotube arrays grown by the one-step anodic oxidation technique and their photocatalytic performance for methane decomposition. Quantitative activity data as a function of film thickness is obtained.  相似文献   
50.
We give necessary and sufficient conditions on a row-finite graph E so that the Leavitt path algebra L(E) is purely infinite simple. This result provides the algebraic analog to the corresponding result for the Cuntz-Krieger C-algebra C(E) given in [T. Bates, D. Pask, I. Raeburn, W. Szymański, The C-algebras of row-finite graphs, New York J. Math. 6 (2000) 307-324].  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