全文获取类型
收费全文 | 9250篇 |
免费 | 799篇 |
国内免费 | 547篇 |
专业分类
化学 | 1220篇 |
晶体学 | 144篇 |
力学 | 696篇 |
综合类 | 78篇 |
数学 | 6926篇 |
物理学 | 1532篇 |
出版年
2024年 | 13篇 |
2023年 | 74篇 |
2022年 | 95篇 |
2021年 | 113篇 |
2020年 | 238篇 |
2019年 | 242篇 |
2018年 | 253篇 |
2017年 | 259篇 |
2016年 | 277篇 |
2015年 | 226篇 |
2014年 | 413篇 |
2013年 | 878篇 |
2012年 | 351篇 |
2011年 | 526篇 |
2010年 | 529篇 |
2009年 | 586篇 |
2008年 | 644篇 |
2007年 | 593篇 |
2006年 | 514篇 |
2005年 | 473篇 |
2004年 | 399篇 |
2003年 | 373篇 |
2002年 | 333篇 |
2001年 | 261篇 |
2000年 | 222篇 |
1999年 | 208篇 |
1998年 | 163篇 |
1997年 | 166篇 |
1996年 | 141篇 |
1995年 | 115篇 |
1994年 | 109篇 |
1993年 | 80篇 |
1992年 | 67篇 |
1991年 | 53篇 |
1990年 | 48篇 |
1989年 | 33篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 44篇 |
1985年 | 46篇 |
1984年 | 54篇 |
1983年 | 40篇 |
1982年 | 50篇 |
1981年 | 41篇 |
1980年 | 38篇 |
1979年 | 45篇 |
1978年 | 30篇 |
1977年 | 17篇 |
1976年 | 20篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
具有重值分担的亚纯函数 总被引:1,自引:0,他引:1
林秀清 《纯粹数学与应用数学》2006,22(1):76-79
在考虑重值分担的情况下,得到一个具有三个分担值的亚纯函数的唯一性定理及若干推论,推广并改进了仪洪勋、Lah iri等人的结果. 相似文献
42.
Ternary mutual diffusion coefficients (D11, D22, D12 and D21) measured by the Taylor dispersion method are reported for aqueous solutions of {levodopa (l-dopa) + β-cyclodextrin (β-CD)} solutions at T = 298.15 K and concentrations up to 0.007 mol · dm−3. Significant effects on the diffusion were observed, suggesting interactions between this carbohydrate and l-dopa. Support for this came from 1H NMR spectroscopy, which shows that these effects are due to formation of 1:1 (β-CD:l-dopa) complexes. 相似文献
43.
Bound state solutions of D‐dimensional schrödinger equation with exponential‐type potentials 下载免费PDF全文
José Juan Peña Jesús García‐Martínez Jesus García‐Ravelo Jesus Morales 《International journal of quantum chemistry》2015,115(3):158-164
In this article, using an exactly‐solvable multiparameter exponential‐type potential we propose a unified treatment of the analytical bound—state solutions of the Schrödinger equation for exponential‐type potentials in D‐dimensions. Our proposal accepts different approximations to the centrifugal term; however, its usefulness is exemplified in the frame of the Green and Aldrich approach. This fact enables us to compare our results with specific potentials found in the literature and that are obtained here as particular cases of our proposal. That is, instead of solving a specific exponential‐type potential, by resorting each time to a specialized method, the energy spectra and wavefunctions are derived straightforward from the proposed approach. Furthermore, our proposal can be used as an alternative way in the search of solutions to new exponential‐type potentials besides that one can study different approximations to the term . © 2014 Wiley Periodicals, Inc. 相似文献
44.
Density, electrical conductivity and viscosity of binary liquid mixtures of 1-butyl-1-methylpyrrolydinium bis(trifluoromethylsulfonyl)imide, [bmpyrr][NTf2], with γ-butyrolactone (GBL) were measured at temperatures from (293.15 to 323.15) K and at atmospheric pressure over the whole composition range. Excess molar volumes have been calculated from the experimental densities and fitted with the Redlich–Kister polynomial equation. These values are positive over the whole range of ionic liquid mole fraction and at all temperatures. In the range between 0.55 and 0.6 [bmpyrr][NTf2] mole fraction, an ideal behaviour of the ionic liquid mixture with molecular solvent was observed for the first time. Other volumetric properties, such as isobaric thermal expansion coefficients, partial molar volumes and partial molar volumes at infinite dilution have been also calculated, in order to obtain information about interactions between GBL and selected ionic liquid. Positive values of these properties for both components also indicate weaker interactions between GBL and IL compared to the pure components. From the viscosity results, the Angell strength parameter was calculated and found to be 3.24 indicating that [bmpyrr][NTf2] is a “fragile” liquid. From the volumetric and transport properties obtained, formation of the [bmpyrr]+ micellar structures was also discussed. All the results are compared to those obtained for imidazolium-based ionic liquid with GBL. 相似文献
45.
Kimet Jusufi 《中国物理C(英文版)》2023,47(3):035108-035108-9
Using a modified expression for the electric potential in the context of T-duality [Gaete and Nicolini, Phys. Lett. B, 2022], we obtained an exact charged solution within the 4D Einstein-Gauss-Bonnet (4D EGB) theory of gravity in the presence of a cosmological constant. We show that the solution also exists in the regularized 4D EGB theory. Moreover, we point out a correspondence between the black hole solution in the 4D EGB theory and the solution in the non-relativistic Horava–Lifshitz theory. The black hole solution is regular and free from singularity. As a special case, we derive a class of well known solutions in the literature. 相似文献
46.
Analytical theoretical solutions are deduced for the current-potential response, concentration profiles and interfacial potentials of electron-coupled ion transfers in the cyclic voltammetry with thick film-modified electrodes. The theory covers a wide variety of possible situations, namely, the redox transducer can be either immobilized on the working electrode or freely diffusing in the organic film, and the ion transfer can be either simple or complicated by homogeneous chemical processes. A comparative and comprehensive study of each case is performed, establishing the key parameters that define the behaviour of the system, as well as guidelines to analyse its electrochemical signal. 相似文献
47.
《Macromolecular theory and simulations》2017,26(2)
The mechanism of the lower critical solution temperature (LCST) in thermoresponsive polymer solutions has been studied by means of a coarse‐grained single polymer chain simulation and a theoretical approach. The simulation model includes solvent explicitly and thus accounts for solvent interactions and entropy directly. The theoretical model consists of a single chain polymer in an implicit solvent where the effect of solvent is included through the intrapolymer solvophobic potential proposed by Kolomeisky and Widom. The results of this study indicate that the LCST behavior is determined by the competition between the mean energy difference between the bulk and bound solvent, and the entropy loss due to the bound solvent. At low temperatures, solvent molecules are bound to the polymer and the solvophobicity of the polymer is screened, resulting in a coiled state. At high temperatures the entropy loss due to bound solvent offsets the energy gain due to binding which causes the solvent molecules to unbind, leading to the collapse of the polymer chain to a globular state. Furthermore, the coarse‐grained nature of these models indicates that mean interaction energies are sufficient to explain LCST in comparison to specific solvent structural arrangements.
48.
Lingyun GAO 《数学物理学报(B辑英文版)》2017,37(1):187-194
In this paper, we will mainly investigate entire solutions with finite order of two types of systems of differential-difference equations, and obtain some interesting results. It extends some results concerning complex differential (difference) equations to the systems of differential-difference equations. 相似文献
49.
50.
As a first step towards the numerical analysis of the stochastic primitive equations of the atmosphere and the oceans,the time discretization of these equations by an implicit Euler scheme is studied.From the deterministic point of view,the 3D primitive equations are studied in their full form on a general domain and with physically realistic boundary conditions.From the probabilistic viewpoint,this paper deals with a wide class of nonlinear,state dependent,white noise forcings which may be interpreted in either the It6 or the Stratonovich sense.The proof of convergence of the Euler scheme,which is carried out within an abstract framework,covers the equations for the oceans,the atmosphere,the coupled oceanic-atmospheric system as well as other related geophysical equations.The authors obtain the existence of solutions which are weak in both the PDE and probabilistic sense,a result which is new by itself to the best of our knowledge. 相似文献