全文获取类型
收费全文 | 139439篇 |
免费 | 2471篇 |
国内免费 | 541篇 |
专业分类
化学 | 61351篇 |
晶体学 | 1120篇 |
力学 | 7830篇 |
综合类 | 4篇 |
数学 | 41640篇 |
物理学 | 30506篇 |
出版年
2022年 | 416篇 |
2021年 | 769篇 |
2020年 | 883篇 |
2019年 | 777篇 |
2018年 | 11001篇 |
2017年 | 10796篇 |
2016年 | 7676篇 |
2015年 | 2324篇 |
2014年 | 1963篇 |
2013年 | 3797篇 |
2012年 | 6711篇 |
2011年 | 13767篇 |
2010年 | 7536篇 |
2009年 | 7699篇 |
2008年 | 9736篇 |
2007年 | 11692篇 |
2006年 | 3161篇 |
2005年 | 3923篇 |
2004年 | 3598篇 |
2003年 | 3752篇 |
2002年 | 2613篇 |
2001年 | 1552篇 |
2000年 | 1432篇 |
1999年 | 1014篇 |
1998年 | 908篇 |
1997年 | 869篇 |
1996年 | 1077篇 |
1995年 | 853篇 |
1994年 | 861篇 |
1993年 | 947篇 |
1992年 | 817篇 |
1991年 | 629篇 |
1990年 | 650篇 |
1989年 | 543篇 |
1988年 | 560篇 |
1987年 | 587篇 |
1986年 | 536篇 |
1985年 | 712篇 |
1984年 | 712篇 |
1983年 | 628篇 |
1982年 | 649篇 |
1981年 | 638篇 |
1980年 | 602篇 |
1979年 | 544篇 |
1978年 | 569篇 |
1977年 | 517篇 |
1976年 | 458篇 |
1975年 | 436篇 |
1974年 | 407篇 |
1973年 | 438篇 |
排序方式: 共有10000条查询结果,搜索用时 564 毫秒
61.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution. 相似文献
62.
We prove that to most of the known hypercyclic operators A on separable Banach spaces there exist compact (compact convex, compact connected) subsets K of E such that each compact (compact convex, compact connected) subset of E can be approximated with respect to Hausdorff's distance by for suitable .
Received July 8, 1997, in final form October 17, 1997 相似文献
63.
64.
Eduard Feireisl Antonín Novotný Hana Petzeltov 《Mathematical Methods in the Applied Sciences》2002,25(12):1045-1073
We prove a general compactness result for the solution set of the compressible Navier–Stokes equations with respect to the variation of the underlying spatial domain. Among various corollaries, we then prove a general existence theorem for the system in question with no restrictions on smoothness of the spatial domain. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
65.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献
66.
Chee Sing Yap 《The Journal of the Operational Research Society》1989,40(7):649-658
This paper describes three case studies which investigated issues relating to the implementation and management of advanced information technology. The benefits derived from information technology were found to vary from one organization to another. These studies provide further evidence to support earlier research findings that senior management has an important role to play in the effective exploitation of information technology, and that the investment approach taken by an organization has a significant effect on the development of computer-based information systems. The effectiveness of a system depends not only on applying the appropriate technology, but also on how successfully technical and behavioural issues are resolved. 相似文献
67.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献
68.
Marí a J. Martí n Dragan Vukotic 《Proceedings of the American Mathematical Society》2006,134(6):1701-1705
We show that every composition operator which is an isometry of the Dirichlet space is induced by a univalent full map of the disk into itself that fixes the origin. This is an analogue of the Hardy space result for inner functions due to Nordgren. The proof relies on the Stone-Weierstrass theorem and the Riesz representation theorem.
69.
M I Salema A P B Póvoa A Q Novais 《The Journal of the Operational Research Society》2006,57(6):615-629
In this paper, an MILP formulation is proposed for the design of a reverse logistics network based on a warehouse location–allocation model, which optimizes, simultaneously, the forward and reverse networks. A single product model with unlimited capacity is first defined. Subsequently, the model is extended to a multi-product capacitated recovery network model, where capacity limitations and a multi-product system can be considered. The proposed model is compared to published work in the field, where different model assumptions have been proposed. Two cases are described so as to gain a better insight into the model and allow a comparative analysis. 相似文献
70.
Zoltá n M. Balogh Marianna Csö rnyei 《Proceedings of the American Mathematical Society》2006,134(9):2667-2675
We give sufficient conditions for Sobolev and Lipschitz functions in terms of their lower scaled-oscillation. The sharpness of these conditions is shown by examples. Our examples also show that a Stepanov-type differentiability theorem does not hold under the boundedness assumption of the lower scaled-oscillation.