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   4085篇
  免费   186篇
  国内免费   29篇
化学   2736篇
晶体学   95篇
力学   147篇
综合类   2篇
数学   413篇
物理学   907篇
  2023年   42篇
  2022年   139篇
  2021年   115篇
  2020年   121篇
  2019年   111篇
  2018年   102篇
  2017年   77篇
  2016年   169篇
  2015年   126篇
  2014年   168篇
  2013年   367篇
  2012年   248篇
  2011年   306篇
  2010年   176篇
  2009年   154篇
  2008年   189篇
  2007年   222篇
  2006年   142篇
  2005年   129篇
  2004年   103篇
  2003年   81篇
  2002年   77篇
  2001年   48篇
  2000年   28篇
  1999年   24篇
  1998年   26篇
  1997年   22篇
  1996年   35篇
  1995年   33篇
  1994年   36篇
  1993年   50篇
  1992年   37篇
  1991年   19篇
  1990年   17篇
  1989年   28篇
  1988年   31篇
  1987年   24篇
  1986年   25篇
  1985年   40篇
  1984年   25篇
  1983年   38篇
  1982年   39篇
  1981年   30篇
  1980年   35篇
  1979年   34篇
  1978年   25篇
  1977年   22篇
  1976年   27篇
  1974年   23篇
  1973年   19篇
排序方式: 共有4300条查询结果,搜索用时 0 毫秒
1.
2.
3.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain a decomposition of continuity.  相似文献   
4.
5.
6.

Background  

The aim of the present study was to characterize the activation profiles of 15 opioid ligands in transfected human embryonic kidney cells expressing only δ opioid receptors. Activation profiles of most of these ligands at δ opioid receptors had not been previously characterized in vitro. Receptor activation was assessed by measuring the inhibition of forskolin-stimulated cAMP production.  相似文献   
7.
Pre—Separation Axioms in Fuzzifying Topology   总被引:1,自引:0,他引:1  
1  IntroductionYing[5,6 ] introduced and elementally developed so called fuzzifying topology with the semanticmethod of continuous valued L ogic.Shen[7] introduced and studied T0 -,T1-,T2 (Hausdorff) -,T3(regularity) -,T4 (normality) -separation axioms in fuzzifying topology.In [3 ]the concepts of thefamily of fuzzifying pre-open sets,fuzzifying pre-neighbourhood structure of a point and fuzzifyingpre-closure are introduced and studied.It is worth to mention that pre-separation axioms are …  相似文献   
8.
The present paper reports the dislocation unpinning model of acoustic emission (AE) from alkali halide crystals. Equations are derived for the strain dependence of the transient AE pulse rate, peak value of the AE pulse rate and the total number of AE pulse emitted. It is found that the AE pulse rate should be maximum for a particular strain of the crystals. The peak value of the AE pulse rate should depend on the volume and strain rate of the crystals, and also on the pinning time of dislocations. Since the pinning time of dislocations decreases with increasing strain rate, the AE pulse rate should be weakly dependent on the strain rate of the crystals. The total number of AE should increase linearly with deformation and then it should attain a saturation value for the large deformation. By measuring the strain dependence of the AE pulse rate at a fixed strain rate, the time constantτ s for surface annihilation of dislocations and the pinning timeτ p of the dislocations can be determined. A good agreement is found between the theoretical and experimental results related to the AE from alkali halide crystals.  相似文献   
9.
Considering external electric field as well as third- and fourth-order phonon anharmonic interaction terms in the pseudospin-lattice coupled mode (PLCM) model Hamiltonian for KDP-type ferroelectrics, expressions for field-dependent shift, width, renormalized soft mode frequency, Curie temperature, dielectric constant and dielectric loss are evaluated. For the calculation, method of statistical double-time temperature-dependent Green’s function has been used. By fitting model values of physical quantities, temperature and electric field dependences of soft mode frequency, dielectric constant and loss have been calculated which compare well with experimental results of Baumgartner [8] and Choi and Lockwood [9]. Both dielectric constant and loss decrease with electric field.  相似文献   
10.
Nanosize aluminum substituted nickel zinc ferrites were prepared through aerosol route and characterized using TEM, XRD, magnetic measurements and Mössbauer spectroscopy. The particle size of as obtained samples was found to be ∼10 nm which increases up to ∼85 nm upon annealing at 1200 °C. The unit cell parameter ‘a’ decreases linearly with concentration of aluminum due to the small ionic radius of aluminum. The saturation magnetization for all the samples after annealing at 1200 °C lies in the range 12.9–72.6 emu/g and decreases linearly with concentration of aluminum. Room temperature Mössbauer spectra of all as obtained samples of ferrite compositions exhibited a broad doublet suggesting super paramagnetic nature. This doublet is further resolved into two doublets and assigned to the surface region and internal region atoms of the particles. The samples annealed at 1200 °C show broad sextets, which were fitted with five sextets, indicating different local environment of both tetrahedrally and octahedrally coordinated Fe cation.  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