全文获取类型
收费全文 | 6330篇 |
免费 | 175篇 |
国内免费 | 35篇 |
专业分类
化学 | 4680篇 |
晶体学 | 37篇 |
力学 | 139篇 |
数学 | 848篇 |
物理学 | 836篇 |
出版年
2023年 | 37篇 |
2022年 | 47篇 |
2021年 | 56篇 |
2020年 | 85篇 |
2019年 | 83篇 |
2018年 | 58篇 |
2017年 | 50篇 |
2016年 | 158篇 |
2015年 | 132篇 |
2014年 | 142篇 |
2013年 | 286篇 |
2012年 | 381篇 |
2011年 | 427篇 |
2010年 | 215篇 |
2009年 | 188篇 |
2008年 | 391篇 |
2007年 | 426篇 |
2006年 | 455篇 |
2005年 | 386篇 |
2004年 | 343篇 |
2003年 | 306篇 |
2002年 | 276篇 |
2001年 | 99篇 |
2000年 | 59篇 |
1999年 | 48篇 |
1998年 | 60篇 |
1997年 | 77篇 |
1996年 | 86篇 |
1995年 | 66篇 |
1994年 | 68篇 |
1993年 | 102篇 |
1992年 | 56篇 |
1991年 | 54篇 |
1990年 | 72篇 |
1989年 | 51篇 |
1988年 | 41篇 |
1987年 | 39篇 |
1986年 | 37篇 |
1985年 | 70篇 |
1984年 | 58篇 |
1983年 | 37篇 |
1982年 | 66篇 |
1981年 | 58篇 |
1980年 | 50篇 |
1979年 | 48篇 |
1978年 | 45篇 |
1977年 | 28篇 |
1976年 | 41篇 |
1975年 | 23篇 |
1974年 | 20篇 |
排序方式: 共有6540条查询结果,搜索用时 15 毫秒
1.
Marcelo Do Amaral Steven Van Es Jos M. Asua 《Journal of polymer science. Part A, Polymer chemistry》2004,42(16):3936-3946
The production of high‐solid‐content, low‐viscosity latexes is an active field in both industry and academia. The viscosity of polymer dispersions has a clear dependence on the particle size distribution (PSD). An example is the rule of thumb that a bimodal PSD enables the reduction of the viscosity with respect to monomodal systems. Despite important progress in theoretical work, not much has been done to quantitatively predict the low shear viscosity of aqueous polymer dispersions as a function of the complex PSD. In this work, the capability of a low‐shear‐viscosity equation to quantitatively account for the influence of both the PSD and the physicochemical characteristics of the dispersions is experimentally assessed. An analysis, consistent with theoretical concepts, of the data with semiempirical correlations is proposed. Next, with values of the parameters of the viscosity equation obtained experimentally, the effect of a latex with a 70% solid content on the low shear viscosity is examined. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3936–3946, 2004 相似文献
2.
3.
Steven G. Buyske 《Geometriae Dedicata》1992,44(1):7-16
In 1980 Chern and Terng defined a Bäcklund transformation for affine minimal surfaces. In this paper we show that this Bäcklund transformation can be simply represented by an involution and translation of the affine conormal. 相似文献
4.
We apply cluster expansion methods to to theN=2 Wess-Zumino models in finite volume, in two space-time dimensions. We show that in the region of convergence of the cluster expansion, a vanishing theorem holds for the supercharge of the theory; that is, the dimension of the kernel of the Hamiltonian is equal to the index of the supercharge.Supported in part by National Science Foundation Mathematical Sciences Postdoctoral Research Fellowship DMS 90-07206Supported in part by National Science Foundation Mathematical Sciences Postodoctoral Research Fellowship DmS 88-07291 相似文献
5.
Steven Schmidt Gü nter Lattermann Ralf Kleppinger Joachim H. Wendorff 《Liquid crystals》1994,16(4):693-702
Liquid crystalline complexes with chromium, molybdenum and with tungsten as metallic centres are reported. 1,4,7-Trisubstituted 1,4,7-triazacyclononane and three carbonyl groups are coordinated in an octahedral geometry. The observed mesophases are characterized as disordered rectangular columnar of a pyramidic type. 相似文献
6.
Steven J. Sepanski 《Journal of Theoretical Probability》1997,10(4):1053-1063
For independent identically distributed random vectors belonging to the generalized Domain of Attraction of the multivariate normal law, we define two partial sum processes analogous to that of Donsker's Theorem. We prove that each converges in distribution to a Brownian Motion in the space of continuous functions. One process uses nonrandom operator normalization, and the other is a studentization of the first, using normalization by the empirical covariance operator. 相似文献
7.
Abhimanyu O. Patil Stephen Zushma Robert T. Stibrany Steven P. Rucker Louise M. Wheeler 《Journal of polymer science. Part A, Polymer chemistry》2003,41(13):2095-2106
Novel nickel(II) bisbenzimidazole complexes were prepared via a three‐step synthetic procedure consisting of aniline/diacid condensation, ligand N‐alkylation, and metal complexation. The complexes were characterized by X‐ray crystallography and found to possess a pseudotetrahedral geometry. Upon activation with methylaluminoxane, these nickel bisbenzimidazoles did not polymerize simple olefins (e.g., ethylene, propylene, and 1‐butene) but were found to carry out the rapid and efficient polymerization of norbornene. The polynorbornene products were characterized by gel permeation chromatography/light scattering, 13C NMR, and IR, and their Mark–Houwink and dn/dc parameters were determined. The molecular weights of the polynorbornenes were very high (weight‐average molecular weight = 587,000–797,000 g/mol). 13C NMR suggested that the polymerization occurred via vinyl addition (i.e., a 2,3‐linked polymer); no ring‐opened product was observed. Thermogravimetric analysis indicated that the polynorbornenes were stable up to 400 °C under nitrogen. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2095–2106, 2003 相似文献
8.
We construct a convergent cluster expansion for the two-dimensionalN=2 Wess-Zumino model, in a region of parameter space where there are multiple phase. As a result of this expansion, we are able to construct the infinite volume field theory and demonstrate exponential decay of correlations. We are also able to investigate the different phases of the model, develop the phase diagram, and show that the free energy of each phase vanishes.Supported in part by National Science Foundation grants DMS 90-08827, PHY/DMS 88-16214 and DMS 88-58073Supported in part by National Science Foundation Mathematical Sciences Postdoctoral Research Fellowship DMS 88-07291 相似文献
9.
Suzanne J. Dilly Steven J. Carlisle Andrew J. Clark Andrew R. Shepherd Stephen C. Smith Paul C. Taylor Andrew Marsh 《Journal of polymer science. Part A, Polymer chemistry》2006,44(7):2248-2259
A practical and divergent synthesis of supported [1,3,5]‐triazine dendritic molecules on Wang resin, PEGA resin, SynPhase? Lanterns, and silica gel is described. The alkylamine linkers used allow derivatization with functionality for both synthetic (e.g., supported reagent and scavenger activity) and chemical biology applications. The use of supported intermediates allows differentiation of symmetric linkers without the need for protecting group chemistry. The synthetic route uses inexpensive, readily available starting materials in a straightforward and scaleable strategy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2248–2259, 2006 相似文献
10.
Matthew D. Bailey Steven M. Shechter Andrew J. Schaefer 《Operations Research Letters》2006,34(3):307-315
We consider a general adversarial stochastic optimization model. Our model involves the design of a system that an adversary may subsequently attempt to destroy or degrade. We introduce SPAR, which utilizes mixed-integer programming for the design decision and a Markov decision process (MDP) for the modeling of our adversarial phase. 相似文献