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   8420篇
  免费   435篇
  国内免费   195篇
化学   5862篇
晶体学   72篇
力学   332篇
综合类   1篇
数学   1212篇
物理学   1571篇
  2024年   18篇
  2023年   80篇
  2022年   104篇
  2021年   148篇
  2020年   203篇
  2019年   177篇
  2018年   218篇
  2017年   200篇
  2016年   347篇
  2015年   292篇
  2014年   313篇
  2013年   627篇
  2012年   616篇
  2011年   663篇
  2010年   338篇
  2009年   308篇
  2008年   567篇
  2007年   577篇
  2006年   504篇
  2005年   469篇
  2004年   344篇
  2003年   315篇
  2002年   282篇
  2001年   108篇
  2000年   96篇
  1999年   78篇
  1998年   59篇
  1997年   44篇
  1996年   79篇
  1995年   57篇
  1994年   52篇
  1993年   56篇
  1992年   45篇
  1991年   32篇
  1990年   24篇
  1989年   29篇
  1987年   23篇
  1985年   52篇
  1984年   39篇
  1983年   19篇
  1982年   53篇
  1981年   36篇
  1980年   48篇
  1979年   38篇
  1978年   31篇
  1977年   29篇
  1976年   40篇
  1975年   37篇
  1974年   26篇
  1973年   24篇
排序方式: 共有9050条查询结果,搜索用时 15 毫秒
101.
Some curvature conditions about the geodesics emanating from a submanifold are obtained. These conditions are used to to study the topological and geometric properties of the ambient spaces which admit some minimal submanifolds.  相似文献   
102.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C 1 transformation.  相似文献   
103.
This study proposes and construct a primitive quantum arithmetic logic unit (qALU) based on the quantum Fourier transform (QFT). The qALU is capable of performing arithmetic ADD (addition) and logic NAND gate operations. It designs a scalable quantum circuit and presents the circuits for driving ADD and NAND operations on two-input and four-input quantum channels, respectively. By comparing the required number of quantum gates for serial and parallel architectures in executing arithmetic addition, it evaluates the performance. It also execute the proposed quantum Fourier transform-based qALU design on real quantum processor hardware provided by IBM. The results demonstrate that the proposed circuit can perform arithmetic and logic operations with a high success rate. Furthermore, it discusses in detail the potential implementations of the qALU circuit in the field of computer science, highlighting the possibility of constructing a soft-core processor on a quantum processing unit.  相似文献   
104.
A value on ′AN     
We prove here the existence of a value (of norm 1) on the spaces N A and even A N, the closure in the variation distance of the linear space spanned by all games f, where is a non-atomic, non-negative finitely additive measure of mass 1 and f a real-valued function on [0,1] which satisfies a much weaker continuity at zero and one. 1991 Mathematics Subject Classification. 90A08, 90A07This research was in part supported by the Belgian Programme on Interuniversity Poles of Attraction, initiated by the Prime Ministers Science Policy Office.  相似文献   
105.
This paper presents an approach based on topology for the determination of characteristics and properties of curves used in the trimming of NURBS surfaces. Through discrete subdivision and topological criteria, a method is presented to determine characteristics of the boundary; such as whether the set of trimming curves forms a set of closed loops, whether trimming curves contain singularities or self intersections, and whether the boundary is simply connected. A surface mesh partitionning the parameter space is used, formed of isoparametric lines in both parametric directions. Topological properties of the cells of this mesh and their intersections with the trimming curves allow to localize the boundary. Topological treatment of this localization allows to define the interior and exterior of the face, and to refine the boundary localization. Singularities and self intersections of the boundary as well as voids in the face are investigated through the study of topological properties of neighbors. As an application, an algorithm for point localization is presented that very rapidly allows to determine whether a given point in parameter space lies inside, on the boundary or outside of the trimmed surface.  相似文献   
106.
In this Note we consider nonnegative solutions for the nonlinear equation
M+λ,ΛD2u+|x|αup=0
in RN, where M+λ,Λ(D2u) is the so called Pucci operator
M+λ,Λ(M)=λei<0eiei>0ei,
and the ei are the eigenvalues of M et Λ?λ>0. We prove that if u satisfies the decreasing estimate
lim|x|→+∞|x|β?1u(x)=0
for some β satisfying (β?1)(p?1)>2+α then u is radial. In a second time we prove that if p<N+2α+2N?2 and u is a nonnegative radial solution of (1), u(x)=g(r), such that g″ changes sign at most once, then u is zero. To cite this article: I. Birindelli, F. Demengel, C. R. Acad. Sci. Paris, Ser. I 336 (2003).  相似文献   
107.
We consider a class of problems originating from a Raman laser amplification model, for which the equations can be written as a Poisson system with boundary conditions. Once reformulated, this system becomes an integro-differential equation that we study here in some detail. In particular, we show the existence of a smooth solution under general assumptions, and prove its uniqueness for boundary values that are not too far apart. Eventually, we completely solve the question of uniqueness for systems of dimensions one and two. To cite this article: F. Castella et al., C. R. Acad. Sci. Paris, Ser. I 336 (2003).  相似文献   
108.
Dyson has associated with the Fredholm determinants of the even (resp. odd) Dirichlet kernels a Schrödinger equation on the half-axis and has used, in tandem, the Gel'fand–Levitan and Marchenko methods of inverse scattering theory to study the asymptotics of these determinants. We have proposed following our unearthing of the conductor operator to seek to realize the Fourier transform itself as a scattering, and we obtain here to this end two Dirac systems on the entire real axis which are intrinsically associated, respectively, to the cosine and to the sine transforms. To cite this article: J.-F. Burnol, C. R. Acad. Sci. Paris, Ser. I 336 (2003).  相似文献   
109.
110.
The charge-dependent three-nucleon potential due to simultaneous photon and pion exchange was derived. The intermediate state of the three-nucleon system was considered to consist of a Δ (1236) resonance. The contribution of this charge-dependent three-nucleon potential to the charge asymmetric energy of 3He−3H is then evaluated using a reasonable trial wave function for a three-nucleon bound system. This contribution turns out to be small but makes the charge asymmetric energy of 3He−3H slightly larger.  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