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   693篇
  免费   42篇
  国内免费   3篇
化学   358篇
晶体学   4篇
力学   24篇
数学   110篇
物理学   242篇
  2024年   3篇
  2023年   15篇
  2022年   13篇
  2021年   21篇
  2020年   25篇
  2019年   20篇
  2018年   27篇
  2017年   24篇
  2016年   48篇
  2015年   35篇
  2014年   28篇
  2013年   51篇
  2012年   42篇
  2011年   54篇
  2010年   42篇
  2009年   27篇
  2008年   25篇
  2007年   22篇
  2006年   26篇
  2005年   17篇
  2004年   8篇
  2003年   10篇
  2002年   20篇
  2001年   13篇
  2000年   6篇
  1999年   4篇
  1998年   7篇
  1997年   8篇
  1996年   10篇
  1995年   3篇
  1994年   9篇
  1993年   16篇
  1992年   4篇
  1991年   1篇
  1990年   11篇
  1989年   5篇
  1988年   1篇
  1987年   4篇
  1986年   6篇
  1985年   5篇
  1984年   5篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1980年   2篇
  1979年   2篇
  1978年   3篇
  1977年   2篇
  1975年   2篇
  1959年   2篇
排序方式: 共有738条查询结果,搜索用时 31 毫秒
51.
For distinct points x1,x2,…,xn in ℛ (the reals), letϕ[x1, x2,…,xn] denote the divided difference ofϕ. In this paper, we determine the general solutionϕ,g: ℛ → ℛ of the functional equationϕ[x1,x2,…,xn] =g(x1,+ x2 + … + xn) for distinct x1,x2,…, xn in ℛ without any regularity assumptions on the unknown functions.  相似文献   
52.
A new computer design program based on the modified-complex method has been developed for constrained optimization and refinement of optical thin-film multilayer devices. This program is having a provision to include both limiting constraints as well as constraint equations. Constraints are suitably accommodated to generate designs which are practicable and withstand high laser power. Various rapid convergent processes like dynamic contraction and expansion of feasible vertices are incorporated for efficient scanning of the constraint parametric space. A broad band IR antireflection coating has been designed to test its relative efficiency with respect to other available methods. A wide varieties of highly useful multilayer devices have been successfully developed using this method.  相似文献   
53.
The study of changes in the structure (H-bonded) of liquid alcohols at elevated temperatures is rare probably due to low flash points of these liquids. An indigenously devised special quartz cell is now used to carry out the structural studies of these liquids at elevated temperatures through neutron diffraction. Here, the liquid consists of deuterated methanol and neutron data was collected on the high-Q diffractometer at Dhruva, BARC. The corrected data at elevated temperatures (BP (boiling point) and double the BP) show that there is a large change in the H-bonded structure of this liquid. The pre-peak or hump, known to be signature of H-bonded clusters appears to be present at all the three temperatures studied. In the low-Q (scattering vector) data Ornstein Zernike (OZ) behaviour is also observed. It is, however, seen that the intramolecular structure does not change very much at higher temperatures. A detailed model analysis is in progress and would be reported later.  相似文献   
54.
Ruckert  T.  Keune  W.  Sahoo  B.  Sturhahn  W.  Toellner  T. S.  Alp  E. E.  Röhlsberger  R. 《Hyperfine Interactions》2002,144(1-4):65-76
Hyperfine Interactions - Nuclear resonant inelastic X-ray scattering (NRIXS) of 14.4125 keV synchrotron radiation was used to measure directly the partial vibrational density of states (VDOS),...  相似文献   
55.
Ab initio calculations have been carried out to study the magnetic dipole and electric quadrupole hyperfine structure constants of 205Pb+. Many-body effects have been considered to all orders using the relativistic coupled-cluster theory in the singles, doubles and partial triples approximation. The trends of these effects are found to be different from atomic systems that have been studied earlier.  相似文献   
56.
Divinylbenzene derivatives represent an important class of molecular building blocks in organic chemistry and materials science. Reported herein is the palladium‐catalyzed synthesis of divinylbenzenes by meta‐C? H olefination of sulfone‐based arenes. Successful sequential olefinations in a position‐selective manner provided a novel route for the synthesis of hetero‐dialkenylated products, which are difficult to access using conventional methods. Additionally, 1,3,5‐trialkenylated compounds can be generated upon successful removal of the directing group.  相似文献   
57.
The corrosion inhibition impact of two quinoline derivatives, viz tetrazolo [1,5‐a] quinoline‐4‐carbaldehyde ( TQC ) and (Z) ?5‐methyl‐N‐(tetrazolo [1,5‐a] quinolin‐4‐ylmethylene) thiazol‐2‐amine ( MTQT ), has been examined against mild steel in 1 M HCl solution using conventional weight loss, potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, quantum chemical, and scanning electron microscopic studies. The experimental results have showed that TQC and MTQT revealed a good corrosion inhibition and that the inhibition efficiency increases with the increase of concentration of inhibitor to attain 94.54% for TQC and 99.25% for MTQT at 25 ppm. Polarization measurements suggest that TQC and MTQT act as a mixed‐type inhibitor. A synergism between inhibitors can be observed by polarization measurements. Electrochemical impedance spectroscopy measurements show an increase of the transfer resistance with the inhibitor concentration. Adsorption of TQC and MTQT on the mild steel surfaces in 1 N HCl solution follows the Langmuir adsorption isotherm model. Furthermore, quantum chemical calculations have been conducted using B3LYP functional and 6‐31G(d,p) basis set to complement the experimental evidences. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
58.
59.
We first investigate the Lipschitz continuity of (K,K’)-quasiregular C 2 mappings between two Jordan domains with smooth boundaries, satisfying certain partial differential inequalities concerning Laplacian. Then two applications of the obtained result are given: As a direct consequence, we get the Lipschitz continuity of ρ-harmonic (K,K’)-quasiregular mappings, and as the other application, we study the Lipschitz continuity of (K,K’)- quasiconformal self-mappings of the unit disk, which are the solutions of the Poisson equation Δw = g. These results generalize and extend several recently obtained results by Kalaj, Mateljevi? and Pavlovi?.  相似文献   
60.
The current article devoted on the new method for finding the exact solutions of some time‐fractional Korteweg–de Vries (KdV) type equations appearing in shallow water waves. We employ the new method here for time‐fractional equations viz. time‐fractional KdV‐Burgers and KdV‐mKdV equations for finding the exact solutions. We use here the fractional complex transform accompanied by properties of local fractional calculus for reduction of fractional partial differential equations to ordinary differential equations. The obtained results are demonstrated by graphs for the new solutions. Copyright © 2016 John Wiley & Sons, Ltd.  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