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   22892篇
  免费   3834篇
  国内免费   2610篇
化学   11759篇
晶体学   212篇
力学   1001篇
综合类   134篇
数学   1609篇
物理学   6443篇
无线电   8178篇
  2024年   127篇
  2023年   624篇
  2022年   914篇
  2021年   988篇
  2020年   1015篇
  2019年   998篇
  2018年   865篇
  2017年   862篇
  2016年   1085篇
  2015年   1256篇
  2014年   1425篇
  2013年   1730篇
  2012年   2096篇
  2011年   1993篇
  2010年   1464篇
  2009年   1599篇
  2008年   1581篇
  2007年   1376篇
  2006年   1287篇
  2005年   1109篇
  2004年   775篇
  2003年   583篇
  2002年   532篇
  2001年   453篇
  2000年   358篇
  1999年   349篇
  1998年   267篇
  1997年   247篇
  1996年   223篇
  1995年   206篇
  1994年   155篇
  1993年   162篇
  1992年   128篇
  1991年   94篇
  1990年   80篇
  1989年   50篇
  1988年   52篇
  1987年   40篇
  1986年   39篇
  1985年   33篇
  1984年   18篇
  1983年   22篇
  1982年   7篇
  1981年   12篇
  1980年   8篇
  1979年   9篇
  1977年   4篇
  1975年   5篇
  1965年   4篇
  1957年   3篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
21.
In this paper, we deal with the nonlinear second-order differential equation with damped vibration term involving p-Laplacian operator. Of particular interest is the resolution of an open problem. An interesting outcome from our result is that we can obtain the fast homoclinic solution with general superlinear growth assumption in suitable Sobolev space. To our knowledge, our theorems appear to be the first such result about damped vibration problem with p-Laplacian operator.  相似文献   
22.
Acta Mathematica Sinica, English Series - The main purpose of this article is to study the calculating problem of the sixth power mean of the two-term exponential sums, and give an interesting...  相似文献   
23.
As a sequel to [8], we investigate here the behaviour of thetrivial extensions of tilted algebras under stable equivalence.It will be shown that if a finite-dimensional symmetric algebra is stably equivalent to the trivial extension of a tilted algebraB, then is the trivial extension of some tilted algebra A whichhas the same type as B.  相似文献   
24.
Present paper presents a derivation of Luikov equations applicable to sublimation-drying. The physical situation and transfer mechanism are elucidated clearly. The coefficients appearing in Luikov equations are given in a more explicit way. Some formulation mistakes in recent publications are indicated.
Anwendung der Luikov-Gleichungen auf die Sublimationstrocknung
Zusammenfassung Die Untersuchung bezieht sich auf eine Ableitung der Luikov-Gleichungen, mittels deren sich der Vorgang der Sublimationstrocknung analysieren läßt. Physikalische Anfangssituation und Austauschmechanismen werden klar herausgestellt und die in den Luikov-Gleichungen auftretenden Koeffizienten in expliziter Weise angegeben. Ferner erfolgt Hinweis auf Formulierungsfehler in jüngeren Veröffentlichungen.

Nomenclature C M v/V f, concentration of vapor, kg/m3 - c pv specific heat of vapor at constant pressure, J/kg K - c pw specific heat of adsorbed water at constant pressure, J/kg K - c s specific heat of solid skeleton, J/kg K - C s M s/V f, concentration of solid skeleton, kg/m3 - C w M w/V f, concentration of adsorbed water, kg/m3 - f V w/V f, volumetric fraction of adsorbed water - j F mass flux of vapor by diffusion (Fick) transfer, kg/m2 s - j D mass flux of vapor by filtration (Darcy) transfer, kg/m2 s - j v total mass flux of vapor, kg/m2 s - k permeability, m2 - M s mass of solid skeleton, kg - M v mass of vapor in pores, kg - M w mass of adsorbed water, kg - P pressure, Pa - q heat flux, W/m2 - R gas constant, J/kg K - T temperature, K - V f volume of the framework of porous medium, m3 - V v volume of vapor in porous medium, m3 - V w volume of the absorbed water, m3 Greek symbols /(c p), effective thermal diffusivity, m2/s - m effective vapor diffusivity in porous medium, m2/s - p R T /, Luikov pressure diffusivity, m2/s - +f, porosity of the porous medium - effective thermal conductivity of porous body, W/m K - dynamic viscosity of vapor, kg/m s - kinematic viscosity, m2/s - Ck/=k/, Luikov filtration motion coefficient, s - V v/V f, volumetric fraction of vapor - density of absorbed water, kg/m3 - (c p) M v c pv+M s c s+M w c pw /V f=Cc pv+C s c s+fc pw, effective product of density and specific heat of humid porous body, J/m3K  相似文献   
25.
26.
27.
Lithium metal batteries (LMBs), due to their ultra-high energy density, are attracting tremendous attentions. However, their commercial application is severely impeded by poor safety and unsatisfactory cycling stability, which are induced by lithium dendrites, side reactions, and inferior anodic stability. Electrolytes, as the indispensable and necessary components in lithium metal batteries, play a crucial role in regulating the electrochemical performance of LMBs. Recently, the fluorinated electrolytes are widely investigated in high-performance LMBs. Thus, the design strategies of fluorinated electrolytes are thoroughly summarized, including fluorinated salts, fluorinated solvents, and fluorinated additives in LMBs, and insights of the fluorinated components in suppressing lithium dendrites, improving anodic stability and cycling stability. Finally, an outlook with several design strategies and challenges will be proposed for novel fluorinated electrolytes.  相似文献   
28.
29.
Methylene blue-intercalated alpha-zirconium phosphate (MBZrP) micro particles in deionized water were deposited onto the surface of graphite powder to prepare graphite powder-supported MBZrP, which was subsequently dispersed into methyltrimethoxysilane-derived gels to yield a conductive composite. The composite was used as electrode material to fabricate a surface-renewable, rigid, leak-free carbon ceramic composite electrode, bulk-modified with methylene blue (MB). In the configuration, alpha-zirconium phosphate was employed as a solid host for MB, which acted as a catalyst. Graphite powder ensured conductivity by percolation, the silicate provided a rigid porous backbone and the methyl groups endowed hydrophobicity and thus limited the wetting section of the modified electrode. Peak currents of the MBZrP-modified electrode were surface-confined at low scan rates but diffusion-controlled at high scan rates. Square-wave voltammetric study revealed that MBZrP immobilized in carbon ceramic matrix presented a two-electron, three-proton redox process in acidic aqueous solution with pH ranged from 0.44 to 2.94. In addition, the chemically modified electrode showed an electrocatalytic activity toward nitrite reduction at +0.15 V ( vs. Ag/AgCl) in acidic aqueous solution (pH=0.44). The linear range and detection limit are 1x10(-6)-4x10(-3) mol x L(-1) and 1.5x10(-7) mol x L(-1), respectively.  相似文献   
30.
纳米级NiTiO3粉体的合成   总被引:3,自引:0,他引:3  
以H2TiO3,H2O2及NiCl2为主要原料,用化学共沉淀法制备了纳米级NiTiO3。确定了反应物H2TiO3,H2O2,NH3的最佳摩尔比为1:8:2,用不同的退火温度和退火时间对样品处理得到相应粒径的纳米级粉体。  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