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   3433篇
  免费   271篇
  国内免费   335篇
化学   366篇
晶体学   18篇
力学   297篇
综合类   89篇
数学   2585篇
物理学   684篇
  2024年   3篇
  2023年   41篇
  2022年   60篇
  2021年   51篇
  2020年   72篇
  2019年   91篇
  2018年   80篇
  2017年   87篇
  2016年   92篇
  2015年   73篇
  2014年   130篇
  2013年   258篇
  2012年   129篇
  2011年   131篇
  2010年   169篇
  2009年   208篇
  2008年   218篇
  2007年   246篇
  2006年   210篇
  2005年   206篇
  2004年   176篇
  2003年   175篇
  2002年   166篇
  2001年   138篇
  2000年   147篇
  1999年   114篇
  1998年   109篇
  1997年   93篇
  1996年   79篇
  1995年   57篇
  1994年   60篇
  1993年   22篇
  1992年   28篇
  1991年   14篇
  1990年   17篇
  1989年   14篇
  1988年   7篇
  1987年   10篇
  1986年   2篇
  1985年   5篇
  1984年   12篇
  1983年   6篇
  1982年   4篇
  1981年   4篇
  1980年   9篇
  1979年   6篇
  1978年   4篇
  1977年   2篇
  1970年   1篇
  1936年   1篇
排序方式: 共有4039条查询结果,搜索用时 15 毫秒
141.
We study the electromagnetic form factors and tensor polarization observables of the deuteron in the framework of the hard-wall AdS/QCD model. We find a profile function for the bulk twist \begin{document}$\tau=6$\end{document} vector field, which describes the deuteron on the boundary and fix the infrared boundary cut-off of AdS space in accordance with the ground state mass of the deuteron. We obtain the deuteron charge monopole, quadrupole, and magnetic dipole form factors and tensor polarization observables from the bulk Lagrangians for the deuteron and photon field interactions. We plot the momentum transfer dependence of the form factors and tensor polarization observables and compare our numerical results with those in the soft-wall model and experimental data.  相似文献   
142.
非保守力学系统Nielsen方程的形式不变性   总被引:6,自引:2,他引:6       下载免费PDF全文
方建会  薛庆忠  赵嵩卿 《物理学报》2002,51(10):2183-2185
研究非保守力学系统Nielsen方程的形式不变性.给出非保守力学系统Nielsen方程的形式不变性的定义和判据,研究形式不变性和Noether对称性的关系,并举例说明结果的应用 关键词: 非保守力学系统 Nielsen方程 形式不变性 Noether对称性  相似文献   
143.
Rose bengal has been used in the diagnosis of ophthalmic disorders and liver function, and has been studied for the treatment of solid tumor cancers. To date, the antibacterial activity of rose bengal has been sporadically reported; however, these data have been generated with a commercial grade of rose bengal, which contains major uncontrolled impurities generated by the manufacturing process (80–95% dye content). A high-purity form of rose bengal formulation (HP-RBf, >99.5% dye content) kills a battery of Gram-positive bacteria, including drug-resistant strains at low concentrations (0.01–3.13 μg/mL) under fluorescent, LED, and natural light in a few minutes. Significantly, HP-RBf effectively eradicates Gram-positive bacterial biofilms. The frequency that Gram-positive bacteria spontaneously developed resistance to HP-RB is extremely low (less than 1 × 10−13). Toxicity data obtained through our research programs indicate that HP-RB is feasible as an anti-infective drug for the treatment of skin and soft tissue infections (SSTIs) involving multidrug-resistant (MDR) microbial invasion of the skin, and for eradicating biofilms. This article summarizes the antibacterial activity of pharmaceutical-grade rose bengal, HP-RB, against Gram-positive bacteria, its cytotoxicity against skin cells under illumination conditions, and mechanistic insights into rose bengal’s bactericidal activity under dark conditions.  相似文献   
144.
Single domain antibodies from camelids, or nanobodies, are a unique class of antibody fragments with several advantageous characteristics: small monomeric size, high stability and solubility and easy tailoring for multiple applications. Nanobodies are gaining increasing acceptance as diagnostic tools and promising therapeutic agents in cancer and other diseases. While most nanobodies are obtained from immunized animals of the camelid family, a few synthetic nanobody libraries constructed in recent years have shown the capability of generating high quality nanobodies in terms of affinity and stability. Since this synthetic approach has important advantages over the use of animals, the recent advances are indeed encouraging. Here we review over a dozen synthetic nanobody libraries reported so far and discuss the different approaches followed in their construction and validation, with an emphasis on framework and hypervariable loop design as critical issues defining their potential as high-class nanobody sources.  相似文献   
145.
In the computing literature, there are few detailed analytical studies of the global statistical characteristics of a class of multiplicative pseudo-random number generators.We comment briefly on normal numbers and study analytically the approximately uniform discrete distribution or (j,)-normality in the sense of Besicovitch for complete periods of fractional parts {x 0 1 i /p} on [0, 1] fori=0, 1,..., (p–1)p–1–1, i.e. in current terminology, generators given byx n+1 1 x n mod p wheren=0, 1,..., (p–1)p –1–1,p is any odd prime, (x 0,p)=1, 1 is a primitive root modp 2, and 1 is any positive integer.We derive the expectationsE(X, ),E(X 2, ),E(X nXn+k); the varianceV(X, ), and the serial correlation coefficient k. By means of Dedekind sums and some results of H. Rademacher, we investigate the asymptotic properties of k for various lagsk and integers 1 and give numerical illustrations. For the frequently used case =1, we find comparable results to estimates of Coveyou and Jansson as well as a mathematical demonstration of a so-called rule of thumb related to the choice of 1 for small k.Due to the number of parameters in this class of generators, it may be possible to obtain increased control over the statistical behavior of these pseudo-random sequences both analytically as well as computationally.  相似文献   
146.
本文研究了一个新的、基本的不含参量的Hilbert型不等式.应用改进的Euler-Maclaurin求和公式以估算权系数,证明了其常数系数为最佳值以及此不等式的等价式.  相似文献   
147.
许学军  梅凤翔  秦茂昌 《中国物理》2004,13(12):1999-2002
Based on the invariance of Birkhoffian equations under the infinitesimal transformations of groups, the definition and the criterion of a form invariance for a Birkhoffian system are established. The condition under which the form invariance can lead to a non-Noether conserved quantity and the form of the conserved quantity are deduced by relyingon the total time derivative along the trajectory of the equations, and two corollaries in special cases are presented. An example is finally given to illustrate the application of the results.  相似文献   
148.
分布形式未知的矩法<英>   总被引:1,自引:0,他引:1  
我们考虑分布形式未知的矩法,假设分布函数F_θ(x)可用一多项式表示或逼近。多项式的阶数r未知,其系数为未知参数θ_1,…,θ_r。我们给出了θ_1,…,θ_r的一种新的矩法估计,r可自动地求得,估计是强一致的。  相似文献   
149.
In this paper, we study the global stability, and the periodic character of the rational recursive sequence. We show that the positive equilibrium of the sequence is a global attractor with a basin which depends on certain conditions posed on the coefficients.  相似文献   
150.
Nakao’s stochastic integrals for continuous additive functionals of zero energy are extended from the symmetric Dirichlet forms setting to the non-symmetric Dirichlet forms setting.It? ’s formula in terms of the extended stochastic integrals is obtained.  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