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   147541篇
  免费   13116篇
  国内免费   7629篇
化学   73091篇
晶体学   1385篇
力学   11035篇
综合类   310篇
数学   39420篇
物理学   43045篇
  2024年   279篇
  2023年   1601篇
  2022年   2718篇
  2021年   2835篇
  2020年   3107篇
  2019年   2907篇
  2018年   12306篇
  2017年   11953篇
  2016年   9239篇
  2015年   4272篇
  2014年   4412篇
  2013年   5594篇
  2012年   10305篇
  2011年   16738篇
  2010年   9858篇
  2009年   9980篇
  2008年   10887篇
  2007年   12553篇
  2006年   3955篇
  2005年   4386篇
  2004年   3887篇
  2003年   3820篇
  2002年   2719篇
  2001年   1704篇
  2000年   1641篇
  1999年   1682篇
  1998年   1492篇
  1997年   1433篇
  1996年   1483篇
  1995年   1165篇
  1994年   995篇
  1993年   855篇
  1992年   726篇
  1991年   641篇
  1990年   550篇
  1989年   443篇
  1988年   393篇
  1987年   331篇
  1986年   306篇
  1985年   250篇
  1984年   185篇
  1983年   138篇
  1982年   121篇
  1981年   105篇
  1980年   111篇
  1979年   77篇
  1978年   64篇
  1977年   58篇
  1976年   46篇
  1973年   53篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
It is explicitly shown that if phase transition occurs at the core of a newborn neutron star with moderately strong magnetic field strength, which populates only the electron’s Landau levels, then in the β -equilibrium condition, the quark core is energetically much more unstable than the neutron matter of identical physical condition.  相似文献   
102.
刘少杰  于健 《物理通报》2003,(11):36-37
凯尔文电桥是国内大学基础物理实验所开设的实验内容之一,且多为自组式.关于自组凯尔文电桥的测量精度与桥路参数精度之间的关系,有些实验教材已有推导,但尚未涉及与两低阻相邻电压接头间跨桥电阻的定量关系,不注意这一点,会给测量结果带来一定的误差.本文就实际中常用的等双臂凯尔文电桥从理论上定量地推出了这一关系,进而给出了跨桥电阻可忽略时的适当阻值.  相似文献   
103.
The electrical conductivity was investigated for multi-walled carbon nanotubes (MWNTs) dissolved in chloroform and toluene, respectively. The electrical conductivity remarkably increased with increase in the content of MWNTs, which is in accordance with Archie's equation . Furthermore, a hypothesis of the electronic transport process was proposed to explain the difference between the solution and the solid compound. In addition, the temperature dependence of the electrical conductivity shows that log σ vs. 1/T exist in a good linear relationship. The activation energy of the electrical conductivity decreased with increase in concentration and an inflexion was observed at 60 °C in MWNT/toluene solution.  相似文献   
104.
Basic ideas and results which characterize quantum diffusion of defects in quantum crystals like solid helium as a new phenomenon are presented. Quantum effects in such media lead to a delocalization of point defects (vacancies, impurities etc.) and they turn into quasiparticles of a new type—defectons, which are characterized not by their position in the crystal lattice but by their quasimomentum and dispersion law. Defecton-defecton and defecton-phonon scattering are considered and an interpolation formula for the diffusion coefficient valid in all interesting temperature and concentration regions is presented. A comparison with the experimental data is made. Some alternative points of view are discussed in detail and the inconsistency of the Kisvarsanyi-Sullivan theory is shown.  相似文献   
105.
106.
To further evaluate the causality between endogenous pyrogen (EP)-induced fever and cyclic adenosine-3',5'-monophosphate (cyclic AMP) level, the effects of sodium salicylate (SS) on the febrile response and increased levels of cyclic AMP in both cerebrospinal fluid (c.s.f.) and plasma during EP-induced fever in rabbits were observed. The results suggest that cyclic AMP is probably involved in the central mediation of EP-induced fever and that increased concentration of cyclic AMP in c.s.f. associated with EP-induced fever is not the result of temperature elevation but appears to be caused by the increased synthesis in the central nervous system. In addition it is confirmed that blood is impossibly a contributory source of increased cyclic AMP in c.s.f. during EP fever, and that SS may act subsequent to the increase in cyclic AMP.  相似文献   
107.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
108.
In this paper, the transformation processes of two types of bis(8-hydroxyquinoline)zinc: Znq2 dihydrate and anhydrous (Znq2)4 were investigated by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG). The effects of crystal structure on optical properties of bis(8-hydroxyquinoiline)zinc were analyzed. Znq2 dihydrate can be transformed into anhydrous (Znq2)4 during heating under vacuum. Reversal transformation occurs by the interaction between chloroform and (Znq2)4. But (Znq2)4 was partially transformed into Znq2 dihydrate by the interaction between ethanol and (Znq2)4. The different molecular structure results in different crystal stacking and electronic structure, thereby affect its optical properties.  相似文献   
109.
We define analytic functions within Clifford Algebras CL, and study their trigonometric properties. We write the addition formulas when their arguments, A and B in CL, commute, this generalizes ordinary trigonometry. We examine in particular the case A2 = 1.   相似文献   
110.
In the present paper it is shown that if S1 and S2 are two Clifford topological semigroups satisfying certain conditions and T is an isometric isomorphism of LUC(S1*) onto LUC(S2*), then T maps S1 topologically isomorphically onto S2. Furthermore, T maps M l n(S1) (M(S1), respectively) isometrically isomorphically onto M l n(S2) (M(S2), respectively). Indeed, we have obtained a generalization of a well-known result of Ghahramani, Lau and Losert for locally compact groups to a more general setting of Clifford topological semigroups.  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