全文获取类型
收费全文 | 80433篇 |
免费 | 7997篇 |
国内免费 | 7619篇 |
专业分类
化学 | 33744篇 |
晶体学 | 508篇 |
力学 | 6741篇 |
综合类 | 1335篇 |
数学 | 25724篇 |
物理学 | 27997篇 |
出版年
2023年 | 631篇 |
2022年 | 1316篇 |
2021年 | 1504篇 |
2020年 | 1685篇 |
2019年 | 1835篇 |
2018年 | 1587篇 |
2017年 | 1918篇 |
2016年 | 2261篇 |
2015年 | 2127篇 |
2014年 | 2934篇 |
2013年 | 5572篇 |
2012年 | 3436篇 |
2011年 | 3874篇 |
2010年 | 3315篇 |
2009年 | 4494篇 |
2008年 | 4936篇 |
2007年 | 5254篇 |
2006年 | 4955篇 |
2005年 | 4125篇 |
2004年 | 3817篇 |
2003年 | 3829篇 |
2002年 | 3429篇 |
2001年 | 2924篇 |
2000年 | 2814篇 |
1999年 | 2522篇 |
1998年 | 2346篇 |
1997年 | 1978篇 |
1996年 | 1741篇 |
1995年 | 1569篇 |
1994年 | 1452篇 |
1993年 | 1238篇 |
1992年 | 1170篇 |
1991年 | 903篇 |
1990年 | 757篇 |
1989年 | 654篇 |
1988年 | 597篇 |
1987年 | 471篇 |
1986年 | 407篇 |
1985年 | 461篇 |
1984年 | 465篇 |
1983年 | 220篇 |
1982年 | 360篇 |
1981年 | 425篇 |
1980年 | 320篇 |
1979年 | 303篇 |
1978年 | 232篇 |
1977年 | 209篇 |
1976年 | 157篇 |
1974年 | 114篇 |
1973年 | 110篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
951.
952.
953.
Petr Lachout 《Acta Appl Math》2003,78(1-3):243-250
The paper introduces an extension of the epi-convergence, the lower semicontinuous approximation and the epi-upper semicontinuous approximation of random real functions in distribution. The new notions could be helpful tools for sensitivity analyzes of stochastic optimization problems. The research is evoked by S. Vogel and continues the research started by Vogel and the author. 相似文献
954.
Bourget Alain Jakobson Dmitry Min-Oo Maung Toth John A. 《Letters in Mathematical Physics》2003,64(2):105-118
We determine the limiting density of the zeroes of Heine–Stieltjes polynomials (or of any set of points satisfying the conclusion of Heine–Stieltjes Theorem) in the thermodynamic limit and use this to prove a strong law of large numbers for the zeroes. 相似文献
955.
It is generally in a firm’s interest for its supply chain partners to invest in innovations. To the extent that these innovations either reduce the partners’ variable costs or stimulate demand for the end product, they will tend to lead to higher levels of output for all of the firms in the chain. However, in response to the innovations of its partners, a firm may have an incentive to opportunistically increase its own prices. The possibility of such opportunistic behavior creates a hold-up problem that leads supply chain partners to underinvest in innovation. Clearly, this hold-up problem could be eliminated by a pre-commitment to price. However, by making an advance commitment to price, a firm sacrifices an important means of responding to demand uncertainty. In this paper we examine the trade-off that is faced when a firm’s channel partner has opportunities to invest in either cost reduction or quality improvement, i.e. demand enhancement. Should it commit to a price in order to encourage innovation, or should it remain flexible in order to respond to demand uncertainty. We discuss several simple wholesale pricing mechanisms with respect to this trade-off. 相似文献
956.
Vitali Vogel Jean‐Franois Gohy Bas G. G. Lohmeijer Jacomina A. Van Den Broek Winfried Haase Ulrich S. Schubert Dieter Schubert 《Journal of polymer science. Part A, Polymer chemistry》2003,41(20):3159-3168
In aqueous solutions, amphiphilic block copolymers in which a polystyrene (PS) segment is connected to a poly(ethylene oxide) (PEO) block via a bis(2,2′:6′,2″‐ terpyridine ruthenium) complex can form micelles. Such micelles of the protomer type PS20‐[Ru]‐PEO70, according to the preparation procedure representing frozen micelles, were studied by sedimentation velocity and sedimentation equilibrium analysis in an analytical ultracentrifuge and by transmission electron microscopy, with different techniques applied for the sample preparation. The particles obtained were surprisingly multifarious in size. In ultracentrifugation experiments performed at relatively low salt concentrations, the distributions of the sedimentation coefficient s20,w showed a pronounced peak at 9.6 S and a broad, only partly separated second peak around 14 S. The molar mass of the particles at the peak was around 430,000 g/mol, corresponding to an aggregation number of approximately 85. The average hydrodynamic diameter of the particles in the peak fraction was approximately 13 nm. In electron micrographs of negatively stained samples, spheres of diameters between 10 and 25 nm were the most abundant particles, but larger ones with a wide size range were also visible. The latter particles apparently were composed of smaller ones. The data from both sedimentation analysis and electron microscopy showed that (1) the studied compound formed primary micelles of diameters around 20 nm and (2) the primary micelles had a tendency toward aggregation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3159–3168, 2003 相似文献
957.
基于突变论的林火蔓延分析 总被引:8,自引:0,他引:8
在对森林火灾进行能量和质量守恒分析的基础上,把尖点突变模型应用于森林火灾蔓延的预测,使突变理论在 森林火灾的模型中从理论上有了初步的应用。文中计算了林火发生突变时的一些分歧点,分析了林火突变的特点和变化规 律。 相似文献
958.
The purpose of this paper is to review the mechanisms and available theoretical methods for modeling the strength and failure of thin film/substrate systems 相似文献
959.
Bassan Bruno Gossner Olivier Scarsini Marco Zamir Shmuel 《International Journal of Game Theory》2003,32(1):17-31
We exhibit a general class of interactive decision situations in which all the agents benefit from more information. This class includes as a special case the classical comparison of statistical experiments à la Blackwell.
AMS 2000 Subject Classification:Primary 91A35.The work of Bruno Bassan and Marco Scarsini was partially supported by MIUR-COFIN. The authors express their thanks to Sylvain Sorin for enlightening comments. 相似文献
960.
Yu. M. Smirnov 《Journal of Russian Laser Research》2003,24(2):121-128
Excitation of rhenium atoms by electron impact is investigated by the method of extended crossing beams. At electron energies of 50 eV, the excitation cross sections of 36 resonance and competing transitions in ReI are measured. Within the energy range from the threshold value to 250 eV, six optical excitation functions are detected. The reliability of data on transition probabilities in ReI has been analyzed. 相似文献