全文获取类型
收费全文 | 11963篇 |
免费 | 1663篇 |
国内免费 | 1806篇 |
专业分类
化学 | 9386篇 |
晶体学 | 171篇 |
力学 | 748篇 |
综合类 | 162篇 |
数学 | 1338篇 |
物理学 | 3627篇 |
出版年
2024年 | 16篇 |
2023年 | 177篇 |
2022年 | 387篇 |
2021年 | 377篇 |
2020年 | 468篇 |
2019年 | 434篇 |
2018年 | 357篇 |
2017年 | 354篇 |
2016年 | 531篇 |
2015年 | 515篇 |
2014年 | 638篇 |
2013年 | 855篇 |
2012年 | 981篇 |
2011年 | 1064篇 |
2010年 | 820篇 |
2009年 | 718篇 |
2008年 | 842篇 |
2007年 | 781篇 |
2006年 | 745篇 |
2005年 | 587篇 |
2004年 | 534篇 |
2003年 | 445篇 |
2002年 | 456篇 |
2001年 | 364篇 |
2000年 | 274篇 |
1999年 | 264篇 |
1998年 | 189篇 |
1997年 | 170篇 |
1996年 | 160篇 |
1995年 | 121篇 |
1994年 | 96篇 |
1993年 | 111篇 |
1992年 | 87篇 |
1991年 | 80篇 |
1990年 | 75篇 |
1989年 | 55篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 30篇 |
1985年 | 31篇 |
1984年 | 19篇 |
1983年 | 26篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1978年 | 9篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1973年 | 9篇 |
1972年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
61.
62.
Ying‐Ling Liu Chuan‐Shao Wu Yie‐Shun Chiu Wen‐Hsuan Ho 《Journal of polymer science. Part A, Polymer chemistry》2003,41(15):2354-2367
A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4′‐diaminodiphenylmethane with the sol–gel reaction of a phosphorus‐containing trimethoxysilane (DOPO–GPTMS), which was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with 3‐glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO–GPTMS was confirmed with Fourier transform infrared, 1H and 31P NMR, and elemental analysis. The resulting organic–inorganic hybrid epoxy resins exhibited a high glass‐transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2354–2367, 2003 相似文献
63.
研究了 2 0 0 0年 MCM— B题 ,将问题推广到有三层干扰的复杂情况 ,给出并严格证明了 ( k,1,1)问题的最优解 相似文献
64.
Bao Tong Cui Maoan Han Huizhong Yang 《Journal of Computational and Applied Mathematics》2005,180(2):365-375
This paper deals with the oscillation problems of delay hyperbolic systems with impulses. Some sufficient conditions for oscillations of impulsive delay hyperbolic systems with Robin boundary conditions are obtained and the criteria of oscillation of the systems are established. 相似文献
65.
66.
Forward degenerate four-wave mixing (DFWM) processes are investigated with a femtosecond pulsed laser in lithium niobate crystal doubly-doped with magnesium and iron (LiNbO3:Fe, Mg). The pulse energy dependence reveals a pure third-order nonlinear response, and the third-order nonlinear susceptibility x^(3) in the material is evaluated to be 4.96 × 10^-13 esu. The time-resolved DFWM process shows a response time of x^(3) shorter than 100fs, which is due to the nonresonant electronic nonlinearities. Our results indicate that LiNbO3 crystals have potentials for ultrafast real-time optical processing systems, which require a large and fast x^(3) optical nonlinearity. 相似文献
67.
68.
69.
70.
This paper investigates regression quantiles (RQ) for unstable autoregressive models. The uniform Bahadur representation of the RQ process is obtained. The joint asymptotic distribution of the RQ process is derived in a unified manner for all types of characteristic roots on or outside the unit circle. It involves stochastic integrals in terms of a sequence of independent and identically distributed multivariate Brownian motions with correlated components. The related L-estimator is also discussed. The asymptotic distributions of the RQ and the L-estimator corresponding to the nonstationary componentwise arguments can be transformed into a function of a normal random variable and a sequence of i.i.d. univariate Brownian motions. This is different from the analysis based on the LSE in the literature. As an auxiliary theorem, a weak convergence of a randomly weighted residual empirical process to the stochastic integral of a Kiefer process is established. The results obtained in this paper provide an asymptotic theory for nonstationary time series processes, which can be used to construct robust unit root tests. 相似文献