全文获取类型
收费全文 | 47893篇 |
免费 | 704篇 |
国内免费 | 382篇 |
专业分类
化学 | 24139篇 |
晶体学 | 445篇 |
力学 | 1735篇 |
综合类 | 13篇 |
数学 | 11814篇 |
物理学 | 10833篇 |
出版年
2022年 | 171篇 |
2021年 | 217篇 |
2020年 | 309篇 |
2019年 | 303篇 |
2018年 | 1362篇 |
2017年 | 1609篇 |
2016年 | 1101篇 |
2015年 | 892篇 |
2014年 | 901篇 |
2013年 | 1547篇 |
2012年 | 4040篇 |
2011年 | 3523篇 |
2010年 | 2389篇 |
2009年 | 2035篇 |
2008年 | 1532篇 |
2007年 | 1664篇 |
2006年 | 1640篇 |
2005年 | 5410篇 |
2004年 | 4738篇 |
2003年 | 3001篇 |
2002年 | 1200篇 |
2001年 | 531篇 |
2000年 | 341篇 |
1999年 | 398篇 |
1998年 | 330篇 |
1997年 | 325篇 |
1996年 | 327篇 |
1995年 | 269篇 |
1994年 | 255篇 |
1993年 | 266篇 |
1992年 | 372篇 |
1991年 | 339篇 |
1990年 | 299篇 |
1989年 | 248篇 |
1988年 | 240篇 |
1987年 | 215篇 |
1986年 | 177篇 |
1985年 | 242篇 |
1984年 | 279篇 |
1983年 | 205篇 |
1982年 | 237篇 |
1981年 | 261篇 |
1980年 | 192篇 |
1979年 | 212篇 |
1978年 | 239篇 |
1977年 | 177篇 |
1976年 | 236篇 |
1975年 | 187篇 |
1974年 | 205篇 |
1973年 | 189篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The finite-size corrections, central chargesc, and scaling dimensionsx of tricritical hard squares and critical hard hexagons are calculated analytically. This is achieved by solving the special functional equation or inversion identity satisfied by the commuting row transfer matrices of these lattice models at criticality. The results are expressed in terms of Rogers dilogarithms. For tricritical hard squares we obtainc=7/10,x=3/40, 1/5, 7/8, 6/5 and for hard hexagons we obtainc=4/5,x=2/15, 4/5, 17/15, 4/3, 9/5, in accord with the predictions of conformal and modular invariance. 相似文献
22.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K. 相似文献
23.
A. I. Magunov A. Ya. Faenov I. Yu. Skobelev T. A. Pikuz E. Biémont P. Quinet F. Blasco C. Bonte F. Dorchies T. Caillaud F. Salin C. Stenz 《Journal of Experimental and Theoretical Physics》2002,95(6):998-1005
The satellite structure of 1s2p 1,3 P 1-1s 21 S 0 lines of the He-like argon ion in plasma produced by a 45-fs laser pulse in a gas-jet cluster target is measured with a high spectral resolution. Radiation transitions 2p → 1s from autoionizing states (AISs) are detected for ions ranging from Li-like to F-like. The spectrum observed is theoretically simulated with the use of the spectroscopic data for the AISs of multicharged ions obtained within the multiconfiguration relativistic Hartree-Fock method. Good agreement with experimental data is obtained when the main population channels of these states are taken into account for typical values of cluster-target plasma parameters. 相似文献
24.
Susan Baker Lisa Kelchner Barbara Weinrich Linda Lee Paul Willging Robin Cotton Karen Zur 《Journal of voice》2006,20(4):631-641
Laryngotracheal stenosis is defined as a congenital or acquired narrowing of the airway. Congenital causes may include subglottic membranous or cartilaginous narrowing. Acquired causes may include trauma due to prolonged endotracheal or tracheal intubation or laryngotracheal injury. Although advances have been made over the past 30 years in reconstructive surgeries to improve airway patency in these patients, long-term laryngeal function for voice production is not well defined in this population. This review examines causes, symptoms and signs, and methods for diagnosing laryngotracheal stenosis. Surgical management procedures are briefly summarized. The current literature on voice outcomes is summarized. The predominant voice characteristics in the population are presented, although results are challenged by the heterogeneity of voice presentation and paucity of data from instrumental measures. Considerations for subjective and instrumental assessment, measures of quality of life, instrumental methods, and treatment options specific to the needs of this population are discussed. Research strategies to identify long-term outcomes of surgical and behavioral treatments in this population are posed. 相似文献
25.
Milan Medved? 《Journal of Mathematical Analysis and Applications》2002,267(2):643-650
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality. 相似文献
26.
The determination of the past and the future of a physical system are complementary aims of measurements. An optimal determination of the past of a system can be achieved by an informationally complete set of physical quantities. Such a set is always strongly noncommutative. An optimal determination of the future of a physical system can be obtained by a Boolean complete set of quantities. The two aims can be reconciled to a reasonable degree with using unsharp measurements.This work was partly supported by the Bundesministerium für Forschung und Technologie, Bonn, the Research Institute for Theoretical Physics, Helsinki, and the University of Turku Foundation, Turku. 相似文献
27.
J. S. Chiou J. W. Barlow D. R. Paul 《Journal of Polymer Science.Polymer Physics》1987,25(7):1459-1471
The miscibility of bisphenol-A polycarbonate (PC) with poly(methyl methacrylate) (PMMA) has been reexamined using differential scanning calorimetry (DSC) and optical indications for phase separation on heating, i.e., lower critical solution temperature (LCST) behavior. Various methods have been used to prepare the blends including methylene chloride (CH2Cl2) and tetrahydrofuran (THF) solution casting, melt mixing, and precipitation of PC and PMMA simultaneously from THF solution by using the nonsolvents methanol and heptane. It is shown that the resulting phase behavior for PC/PMMA blends is strongly affected by the blend preparation method. However, these blends are miscible over the whole blend composition range (unambiguous single composition-dependent Tg's and LCST behavior) when prepared by precipitation from solution using heptane as the nonsolvent. To the contrary, solution-cast and melt-mixed PC/PMMA blends were all phase separated, which may be attributed to the “solvent” effect and LCST behavior, respectively, not discovered in previous reports. Methanol precipitation does not lead to fully mixed blends, which demonstrates the importance of the choice of nonsolvent when using the precipitation method. 相似文献
28.
Paul du Bois-Reymond 《Mathematische Annalen》1879,15(3-4):564-576
Ohne Zusammenfassung 相似文献
29.
We consider the one-dimensional steady-state semiconductor deviceequations modelling a pnpn device. There are two relevant scalingsof the equations corresponding to small and large applied voltages.In both scalings, the semiconductor equations can be consideredas singularly perturbed. It turns out that the small-voltagescaling breaks down for current values between two saturationcurrents. In that interval, the large-voltage scaling has tobe employed. For both scalings, we derive the first-order termsof an asymptotic expansion and show that the reduced problemhas a solution. An example verifies that the current-voltagecurves obtained have the expected qualitative structure. 相似文献
30.