全文获取类型
收费全文 | 70093篇 |
免费 | 19194篇 |
国内免费 | 2447篇 |
专业分类
化学 | 71674篇 |
晶体学 | 356篇 |
力学 | 3572篇 |
综合类 | 109篇 |
数学 | 5583篇 |
物理学 | 10440篇 |
出版年
2024年 | 428篇 |
2023年 | 4381篇 |
2022年 | 2346篇 |
2021年 | 3387篇 |
2020年 | 5459篇 |
2019年 | 3248篇 |
2018年 | 3020篇 |
2017年 | 1316篇 |
2016年 | 6619篇 |
2015年 | 6522篇 |
2014年 | 6164篇 |
2013年 | 6785篇 |
2012年 | 5482篇 |
2011年 | 3402篇 |
2010年 | 4911篇 |
2009年 | 4790篇 |
2008年 | 2628篇 |
2007年 | 2228篇 |
2006年 | 1454篇 |
2005年 | 1219篇 |
2004年 | 888篇 |
2003年 | 684篇 |
2002年 | 647篇 |
2001年 | 482篇 |
2000年 | 456篇 |
1999年 | 541篇 |
1998年 | 453篇 |
1997年 | 521篇 |
1996年 | 534篇 |
1995年 | 499篇 |
1994年 | 391篇 |
1993年 | 446篇 |
1992年 | 330篇 |
1991年 | 265篇 |
1990年 | 223篇 |
1989年 | 218篇 |
1988年 | 211篇 |
1987年 | 207篇 |
1980年 | 205篇 |
1978年 | 195篇 |
1977年 | 312篇 |
1976年 | 370篇 |
1975年 | 467篇 |
1974年 | 474篇 |
1973年 | 287篇 |
1972年 | 373篇 |
1971年 | 355篇 |
1970年 | 543篇 |
1969年 | 413篇 |
1968年 | 457篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Dr. Guido Goldschmiedt 《Monatshefte für Chemie / Chemical Monthly》1885,6(1):372-403
Ohne Zusammenfassung 相似文献
62.
Finite element analysis of fluid flow with moving free surface has been performed in 2‐D and 3‐D. The new VOF‐based numerical algorithm that has been proposed by the present authors (Int. J. Numer. Meth. Fluids, submitted) was applied to several 2‐D and 3‐D free surface flow problems. The proposed free surface tracking scheme is based on two numerical tools; the orientation vector to represent the free surface orientation in each cell and the baby‐cell to determine the fluid volume flux at each cell boundary. The proposed numerical algorithm has been applied to 2‐D and 3‐D cavity filling and sloshing problems in order to demonstrate the versatility and effectiveness of the scheme. The proposed numerical algorithm resolved successfully the free surfaces interacting with each other. The simulated results demonstrated applicability of the proposed numerical algorithm to the practical problems of large free surface motion. It has been also demonstrated that the proposed free surface tracking scheme can be easily implemented in any irregular non‐uniform grid systems and can be extended to 3‐D free surface flow problems without additional efforts. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
63.
Gallin Peter Prof. Dr. 《ZDM》2003,35(3):110-119
In order to emphasize functional thinking in mathematical education, arguments are brought forward for an early and frequent use of tree diagrams in teaching stochastics. Since set and tree diagrams can be regarded as two sides of the same matter, Bayes’ theorem, which is strongly associated with predicative set diagrams, need not be dealt with explicitly any longer. Set diagrams are replaced by tree diagrams that are labelled in detail and by tree inversion as a functional instrument of dealing with conditioned probabilities. This technique is demonstrated by three typical problems in the context of conditioned probability. Finally, two letters by Pascal to Fermat are analysed in order to illustrate that predicative and functional approaches were already pursued in the early stages of probability calculus in the 17th century. 相似文献
64.
Envelop solitons in dusty plasmas for warm dust 总被引:1,自引:0,他引:1
A nonlinear Schrödinger equation is obtained for the warm dusty plasmas. The modulational instability of envelop soliton is investigated in this paper. Both the temperature of the dust grains and the charge variations of dust grains affect the instability regions of the dusty plasmas. It also affect the amplitude and the width of the envelop soliton. 相似文献
65.
66.
Jin Sun Yihu Song Qiang Zheng Hong Tan Jie Yu Hong Li 《Journal of Polymer Science.Polymer Physics》2007,45(18):2594-2602
The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO2) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO2 causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO2 hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007 相似文献
67.
光照与彩陶俑表面色变关系的实验研究 总被引:1,自引:0,他引:1
本文以秦彩俑表面色彩为研究对象,通过光照实验与色彩变化的色度测量,分析了光照引起彩俑颜料色变的规律,为秦彩俑这一大型重点文物的色彩保护提供了科学理论依据. 相似文献
68.
C. Scheidenberger K. Beckert P. Beller F. Bosch C. Brandau D. Boutin L. Chen B. Franzke H. Geissel R. Knöbel C. Kozhuharov J. Kurcewicz S. A. Litvinov Yu. A. Litvinov M. Mazzocco G. Münzenberg F. Nolden W. R. Plaß M. Steck B. Sun H. Weick M. Winkler 《Hyperfine Interactions》2006,173(1-3):61-66
One important goal of the ILIMA project at FAIR is the study of masses and decay properties of relativistic isomeric beams
stored and cooled in the planned storage-ring complex. A new scheme is described, where a storage-cooler ring is used for
high-resolution mass separation. Experimental results on the separation of the isobaric pair 140Pr-140Ce are presented.
P. Beller, deceased. 相似文献
69.
This paper is concerned with a class of nonlinear delay partial difference equations with variable coefficients, which may
change sign. By making use of frequency measures, some new oscillatory criteria are established. This is the first time oscillation
of these partial difference equations is discussed by employing frequency measures.
相似文献
70.
This paper presents the preliminary results obtained using an Electron Paramagnetic Resonance imaging apparatus operating at 280 MHz. The acquisition technique and the procedure used to obtain the spin density spatial localization are presented and specimen images of extended samples are given. The accuracy of the images and the spatial resolution are also discussed. 相似文献