全文获取类型
收费全文 | 14437篇 |
免费 | 1120篇 |
国内免费 | 1619篇 |
专业分类
化学 | 6271篇 |
晶体学 | 22篇 |
力学 | 700篇 |
综合类 | 160篇 |
数学 | 7935篇 |
物理学 | 2088篇 |
出版年
2024年 | 26篇 |
2023年 | 164篇 |
2022年 | 252篇 |
2021年 | 302篇 |
2020年 | 482篇 |
2019年 | 392篇 |
2018年 | 365篇 |
2017年 | 452篇 |
2016年 | 494篇 |
2015年 | 405篇 |
2014年 | 644篇 |
2013年 | 1120篇 |
2012年 | 606篇 |
2011年 | 743篇 |
2010年 | 677篇 |
2009年 | 869篇 |
2008年 | 912篇 |
2007年 | 925篇 |
2006年 | 860篇 |
2005年 | 819篇 |
2004年 | 698篇 |
2003年 | 661篇 |
2002年 | 503篇 |
2001年 | 450篇 |
2000年 | 427篇 |
1999年 | 392篇 |
1998年 | 378篇 |
1997年 | 345篇 |
1996年 | 265篇 |
1995年 | 210篇 |
1994年 | 176篇 |
1993年 | 152篇 |
1992年 | 136篇 |
1991年 | 137篇 |
1990年 | 94篇 |
1989年 | 75篇 |
1988年 | 78篇 |
1987年 | 47篇 |
1986年 | 48篇 |
1985年 | 58篇 |
1984年 | 49篇 |
1983年 | 26篇 |
1982年 | 46篇 |
1981年 | 45篇 |
1980年 | 37篇 |
1979年 | 44篇 |
1978年 | 32篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
Mats Gyllenberg 《Journal of Differential Equations》2004,205(1):50-76
For time-periodic dissipative and irreducible type-K competitive Kolmogorov systems, it is proved that there is a canonically defined countable family F of unordered, disjoint invariant sets with the property that, for every persistent trajectory whose ω-limit set is not a cycle, there exists a unique trajectory in some element of F such that these two trajectories are asymptotic and the corresponding points in these two trajectories are K-related. 相似文献
32.
33.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
34.
For an arbitrary bounded closed set E in the complex plane with complement Ω of finite connectivity, we study the degree of convergence of the lemniscates in Ω. 相似文献
35.
林正炎 《数学物理学报(B辑英文版)》2003,23(3)
Let {X_n, n≥1} be a strictly stationary sequence of random variables, whichare either associated or negatively associated, f(·) be their common density. In this paper,the author shows a central limit theorem for a kernel estimate of f(·) under certain regularconditions. 相似文献
36.
Hiroshi Noguchi Masanori Ueda Yoshinobu Baba Masako Takasu 《Journal of Polymer Science.Polymer Physics》2003,41(12):1316-1322
The electrophoresis of DNA chains in uncrosslinked polymer solutions with a Brownian dynamics simulation with an anisotropic friction tensor was analyzed. According to the degree of anisotropy, three types of migration behavior are obtained: fluctuation without or with periodicity between U‐shaped and compact conformations, or migration with linear conformation. We found good agreement between our simulation results and the direct observations of DNA by fluorescence microscopy. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1316–1322, 2003 相似文献
37.
Ergodic isospectral theory of the Lax pairs of Euler equations with harmonic analysis flavor 总被引:2,自引:0,他引:2
Y. Charles Li 《Proceedings of the American Mathematical Society》2005,133(9):2681-2687
Isospectral theory of the Lax pairs of both 3D and 2D Euler equations of inviscid fluids is developed. Eigenfunctions are represented through an ergodic integral. The Koopman group and mean ergodic theorem are utilized. Further harmonic analysis results on the ergodic integral are introduced. The ergodic integral is a limit of the oscillatory integral of the first kind.
38.
Anatoliy Samoilenko Manuel Pinto Sergei Trofimchuk 《Proceedings of the American Mathematical Society》2005,133(1):145-154
We apply the Krylov and Bogolyubov asymptotic integration procedure to asymptotically autonomous systems. First, we consider linear systems with quasi-periodic coefficient matrix multiplied by a scalar factor vanishing at infinity. Next, we study the asymptotically autonomous Van-der-Pol oscillator.
39.
K.B. Welter Q. Wu Y. You K. Abel D. McCreary S.M. Bajorek J.N. Reyes Jr 《International Journal of Multiphase Flow》2004,30(12):407-1484
This article describes a comprehensive literature review of liquid entrainment in horizontal pipes with vertical-up branches. Deficiencies in the available data and correlations were identified. The Air–water Test Loop for Advanced Thermal–hydraulic Studies (ATLATS) was constructed and entrainment onset and steady-state data were collected for a wide range of flow conditions. Using new insights gained from experimental testing, the authors developed a model for predicting the onset of entrainment and steady-state entrainment rate. Previously published correlations, along with the new model, are compared against all available data. The new model shows very good agreement with the onset data, but is not very good at predicting branch quality at high liquid flow rates. 相似文献
40.
Takeshi Murashige Hideo Fujikake Hiroto Sato Hiroshi Kikuchi Taiichiro Kurita Fumio Sato 《Optical Review》2004,11(6):349-352
We have confirmed light diffraction of aligned polymer fibers obtained by a phase separation of an anisotropic-phase solution of liquid crystal and polymer. He—Ne laser light passing through the polymer fibers was scattered in the axis vertical to the fibers, and had two peaks of light intensity symmetrical to the center of the transmitting laser spot. The two peaks were found to be caused by light diffraction due to the periodic polymer-fiber dispersion because the peaks corresponded to values calculated by intervals between the fibers. The periodical fiber networks are considered to be formed by anisotropic spinodal decomposition. This effect can be used to measure the dispersion order of the polymer fibers. © 2004 The Optical Society of Japan 相似文献