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   795篇
  免费   16篇
  国内免费   3篇
化学   636篇
晶体学   2篇
力学   5篇
数学   30篇
物理学   141篇
  2021年   5篇
  2020年   6篇
  2019年   10篇
  2018年   5篇
  2017年   6篇
  2016年   8篇
  2015年   15篇
  2014年   13篇
  2013年   32篇
  2012年   27篇
  2011年   37篇
  2010年   19篇
  2009年   21篇
  2008年   38篇
  2007年   40篇
  2006年   34篇
  2005年   51篇
  2004年   42篇
  2003年   29篇
  2002年   41篇
  2001年   28篇
  2000年   20篇
  1999年   23篇
  1998年   13篇
  1997年   17篇
  1996年   11篇
  1995年   12篇
  1994年   5篇
  1993年   10篇
  1992年   10篇
  1991年   6篇
  1990年   9篇
  1989年   11篇
  1988年   6篇
  1987年   6篇
  1986年   4篇
  1985年   17篇
  1984年   18篇
  1983年   5篇
  1982年   11篇
  1981年   11篇
  1980年   12篇
  1979年   11篇
  1978年   8篇
  1977年   7篇
  1976年   5篇
  1975年   7篇
  1974年   4篇
  1973年   7篇
  1967年   4篇
排序方式: 共有814条查询结果,搜索用时 15 毫秒
131.
We investigated the effects of NaF, NaCl, NaBr, and NaI on the molecular organization of H2O by a calorimetric methodology developed by us earlier. We use the third derivative quantities of G pertaining to 1-propanol (1P) in ternary 1P-a salt-H2O as a probe to elucidate the effects of a salt on H2O. We found that NaF and NaCl worked as hydration centers. The hydration numbers were 19 +/- 2 for NaF and 7.5 +/- 0.6 for NaCl. Furthermore, the bulk H2O away from the hydration shell was found unaffected by the presence of Na+, F-, and Cl-. For NaBr and NaI, in addition to the hydration to Na+, Br- and I- acted like a hydrophilic moiety such as urea. Namely, they formed a hydrogen bond to the existing H2O network and retarded the fluctuation nature of H2O. These findings were discussed with respect to the Hofmeister ranking. We suggested that more chaotropic anions Br- and I- are characterized as hydrophiles, whereas kosmotropes, F- and Cl-, are hydration centers.  相似文献   
132.
133.
We propose a new interpolation technique for the CIP method applied to curvilinear coordinates. The CIP method can hardly maintain third-order accuracy on curvilinear coordinates. The reason for the degeneracy in accuracies has not been discussed in detail. This paper reveals the problems of the CIP method on curvilinear coordinates and presents an improved CIP method to solve the advection equation accurately. The features of the presented method are: (1) the metric computation on the upwind stencil is defined in the same manner as in the advection phase of the CIP method; and (2) gradient values in the physical domain in the computation on the curvilinear coordinates are used. Various test problems show that the improved CIP method has approximate third-order accuracy.  相似文献   
134.
Abstract

The solubility of monosodium L-glutamate monohydrate (MSG.H2O) in water was measured at pressures in the range of 0.10-300MPa and 298.15K. The density of MSG solution at high concentrations and heat of solution at saturated concentration were also measured at atmospheric pressure. The solubility, ms, increased with increasing pressure and the pressure coefficient, Θp, [?(? In ms,? p)T] at 0.10 MPa was (2.0 ± 0.1) × 10-10Pa-1. It agrees well with (2.1 ±0.2)× 10-10 Pa-1 thermodynamically estimated using the partial molar volume, the activity coefficient of the solute in solution, and the molar volume of the crystal. The excellent agreement at 0.10MPa gives us confidence in the solubility data at higher pressures. The heat of solution data and other pertinent values were used to calculate the temperature coefficient of solubility, ΘT [? (? In ms/?(1/T))p], by a thermodynamic equality. The resulting ΘT compares well with the data directly measured by Ogawa.  相似文献   
135.
We introduce the notion of semi-tilting modules and show that the class of basic semi-tilting modules is closed under mutation. Using this, we provide a partial answer to the Wakamatsu tilting conjecture. Also, we define a partial order on the set of equivalence classes of semi-tilting modules and show that this order is closely related to mutation for semi-tilting modules.  相似文献   
136.
A method for the controlled generation of intense high frequency electromagnetic fields by a breaking Langmuir wave (relativistic flying mirrors) in a gradually inhomogeneous plasma is proposed. The wave breaking threshold depends on the local plasma density gradient. Compression, chirping and frequency multiplication of an electromagnetic wave reflected from relativistic mirrors is demonstrated using Particle-In-Cell simulations. Adjusting the shape of the density profile enables control of the reflected light properties.  相似文献   
137.
Hirotaka Koga 《代数通讯》2013,41(7):2417-2429
Let R be a commutative noetherian ring and A a noetherian R-algebra. Let P ? ∈ 𝒦b(𝒫 A ) with Hom𝒦(Mod-A)(P ?, P ?[i]) = 0 for i > 0. We will provide a sufficient condition for P ? to be a direct summand of a silting complex. Also, in case Hom𝒦(Mod-A)(P ?, P ?[i]) = 0 for i ≠ 0, we will provide a sufficient condition for P ? to be a direct summand of a tilting complex.  相似文献   
138.
We have realized the microscopic simulation of olefin polymerization, that is, the simulation of the catalytic polymerization (CP) reaction system composed of (pyridylamido)hafnium(IV) complex as the catalyst. For this purpose, we adopted Red Moon (RM) method, a novel molecular simulation method to simulate the complex reaction system. First, according to the previous research, with the help of the QM calculation, we proposed a model system and elementary processes and explained the theoretical treatment of the simulation by the RM method (the RM simulation). In addition, we also proposed a macroscopic simulation based on chemical kinetics simulation. Then, we performed two simulations and compared them in terms of the effective time evolution of the three macroscopic physical quantities, the number-average molecular weight Mn , the mass-average molecular weight Mw , and the molar-mass dispersity ĐM . The comparison showed that the two simulations are in quantitative or partially qualitative agreement with each other. Therefore, it is concluded that the RM simulation could not only simulate the CP reaction process microscopically, but also it is connected essentially to reproduce the time evolution of the macroscopic physical quantities on the basis of its microscopic simulation data. © 2018 Wiley Periodicals, Inc.  相似文献   
139.
Journal of Thermal Analysis and Calorimetry - Thermal behaviors of two different siliceous concretes used in a sodium-cooled fast reactor were comparatively investigated in a temperature range from...  相似文献   
140.
The physico-geometric kinetics for the solid-state reactions by thermoanalytical (TA) measurements were reexamined by focusing some fundamental aspects: (1) the fundamental kinetic equation, (2) the kinetic model function, (3) the fractional reaction , and (4) the apparent kinetic parameters. It was pointed out that some pitfalls in the practical kinetic study are originated by the disagreement between the kinetic information from the TA measurements and the theory of the physico-geometric kinetics. In order to increase the degree of coordination between the theory and practice, several attempts were made from both the theoretical and experimental points of views. The significance of the apparent kinetic parameters was discussed with a possible orientation for obtaining the reliable kinetic parameters.I would like to thank to Profs H. Tanaka, J. esták, J. M. Criado, A. K. Galwey and Dr. J. Malek for their kind supports.  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