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   2153篇
  免费   73篇
  国内免费   72篇
化学   1037篇
晶体学   12篇
力学   57篇
综合类   2篇
数学   498篇
物理学   692篇
  2023年   7篇
  2022年   44篇
  2021年   55篇
  2020年   54篇
  2019年   47篇
  2018年   70篇
  2017年   56篇
  2016年   93篇
  2015年   41篇
  2014年   69篇
  2013年   97篇
  2012年   103篇
  2011年   126篇
  2010年   87篇
  2009年   79篇
  2008年   93篇
  2007年   65篇
  2006年   96篇
  2005年   89篇
  2004年   155篇
  2003年   141篇
  2002年   86篇
  2001年   89篇
  2000年   24篇
  1999年   20篇
  1998年   31篇
  1997年   18篇
  1996年   14篇
  1995年   19篇
  1994年   25篇
  1993年   34篇
  1992年   31篇
  1991年   23篇
  1990年   19篇
  1989年   18篇
  1988年   22篇
  1987年   11篇
  1986年   10篇
  1985年   17篇
  1984年   8篇
  1983年   4篇
  1982年   11篇
  1981年   10篇
  1980年   5篇
  1977年   4篇
  1976年   8篇
  1974年   5篇
  1973年   7篇
  1972年   4篇
  1911年   4篇
排序方式: 共有2298条查询结果,搜索用时 46 毫秒
231.
232.
233.
234.
地黄滋阴补血填髓,广泛用于贫血和脑疾病患者,但其功效机制尚未阐明.本文探讨地黄水提物(Rehmannia glutinosa’s water extracts,RGWE)改善血虚大鼠记忆及其滋阴补血填髓的可能机制.采用断尾放血结合注射环磷酰胺制备贫血大鼠模型,随机分溶媒组和地黄水提物3,6,10g/kg治疗组,灌服等体积自来水或不同剂量地黄水提物10天,采用Morris水迷宫观测大鼠空间记忆能力,采用酶联免疫吸附测定方法(Enzyme linked immunosorbent assay,ELISA)检测血浆红细胞生成素(EPO)水平,免疫组化和免疫蛋白印迹技术(Western blotting)检测分析脑EPO及其受体表达水平.成功制备血虚模型,表现为大鼠红细胞数和血红蛋白显著下降,与造模前比较差异显著(P<0.05),溶媒组空间记忆能力显著下降,地黄治疗组空间记忆能力明显提高,逃避潜伏期明显缩短(P<0.05),一定时间内穿越平台次数显著增多(P<0.05);免疫组化和Western blotting结果显示脑组织EPO及其受体表达、血浆EPO水平均较溶媒组明显升高(P<0.05).地黄水提物显著提高贫血...  相似文献   
235.
We derive the leading-order equations that govern the dynamics of the flow in a falling, free-standing soap film. Starting with the incompressible Navier?CStokes equations, we carry out an asymptotic analysis using parameters that correspond to a common experimental setup. We account for the effects of inertia, surface elasticity, pressure, viscous stresses, gravity, and air drag. We find that the dynamics of the flow is dominated by the effects of inertia, surface elasticity, gravity, and air drag. We solve the leading-order equations to compute the steady-state profiles of velocity, thickness, and pressure in an experiment in which the film is in the Marangoni elasticity regime. The computational results, which include a Marangoni shock, are in good accord with the experimental measurements.  相似文献   
236.
In this paper, we propose and investigate numerical methods based on QR factorization for computing all or some Lyapunov or Sacker?CSell spectral intervals for linear differential-algebraic equations. Furthermore, a perturbation and error analysis for these methods is presented. We investigate how errors in the data and in the numerical integration affect the accuracy of the approximate spectral intervals. Although we need to integrate numerically some differential-algebraic systems on usually very long time-intervals, under certain assumptions, it is shown that the error of the computed spectral intervals can be controlled by the local error of numerical integration and the error in solving the algebraic constraint. Some numerical examples are presented to illustrate the theoretical results.  相似文献   
237.
In this paper, we deal with the backward problem of determining initial condition for Rayleigh‐Stokes where the data are given at a fixed time. The problem has many applications in some non‐Newtonian fluids. We give some regularity properties of the solution to backward problem.  相似文献   
238.
In this paper, we complete the study of the dynamics of a recognized continuous‐time model for the Babesiosis disease. The local and global asymptotic stability of the endemic state are established theoretically and experimentally. In addition, to restrain the disease in the original model when the endemic state exists, we propose and study the continuous model with feedback controls. The global stability of the boundary‐equilibrium point of this model is analyzed by means of rigorous mathematical methods. As an important consequence of this result, we propose a strategy to select feedback control variables in order to restrain the disease in the original model. This strategy allows us to make the disease vanish completely. In other words, the feedback controls are specially effective for restraining disease in the model. The validity of the established theoretical result is supported by a set of numerical simulations.  相似文献   
239.
We prove some Picone-type identities and inequalities for a class of first-order nonlinear dynamic systems and derive various weighted inequalities of Wirtinger type and Hardy type on time scales. As applications we study oscillatory and related properties of these systems including Reid's roundabout theorem on disconjugacy, Sturm's separation and comparison theorems, as well as a variational method in the oscillation theory.  相似文献   
240.
Nguyen Dinh  Tuan 《Positivity》2019,23(1):195-217
Positivity - The main goal of this note is to formulate sequence-based necessary second-order optimality conditions for a semilinear elliptic optimal control problem, with a pointwise pure state...  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