全文获取类型
收费全文 | 3055篇 |
免费 | 103篇 |
国内免费 | 38篇 |
专业分类
化学 | 1688篇 |
晶体学 | 13篇 |
力学 | 52篇 |
数学 | 822篇 |
物理学 | 621篇 |
出版年
2023年 | 21篇 |
2022年 | 34篇 |
2021年 | 64篇 |
2020年 | 42篇 |
2019年 | 60篇 |
2018年 | 82篇 |
2017年 | 52篇 |
2016年 | 113篇 |
2015年 | 110篇 |
2014年 | 113篇 |
2013年 | 190篇 |
2012年 | 181篇 |
2011年 | 231篇 |
2010年 | 121篇 |
2009年 | 146篇 |
2008年 | 173篇 |
2007年 | 169篇 |
2006年 | 154篇 |
2005年 | 147篇 |
2004年 | 161篇 |
2003年 | 112篇 |
2002年 | 100篇 |
2001年 | 51篇 |
2000年 | 32篇 |
1999年 | 30篇 |
1998年 | 44篇 |
1997年 | 39篇 |
1996年 | 47篇 |
1995年 | 32篇 |
1994年 | 30篇 |
1993年 | 24篇 |
1992年 | 28篇 |
1991年 | 24篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1971年 | 8篇 |
排序方式: 共有3196条查询结果,搜索用时 15 毫秒
41.
A new computational method is presented for the rapid estimation of polymer miscibility. The algorithm (coined FLEXIBLEND) uses molecular mechanics calculations on a pair of polymer segments and takes into account the effects of local chain flexibility to estimate heats of mixing. This paper shows miscibility predictions in agreement with experiment for blends of poly(ethyleneoxide) (PEO) with isotactic poly(propylene) (PP) as an immiscible system and of PEO with poly(acrylic acid) (PAA) as a miscible system. 相似文献
42.
43.
44.
Johanne Heitmann Solheim Boris Zimmermann Valeria Tafintseva Simona Dzurendov Volha Shapaval Achim Kohler 《Molecules (Basel, Switzerland)》2022,27(6)
Extended multiplicative signal correction (EMSC) is a widely used preprocessing technique in infrared spectroscopy. EMSC is a model-based method favored for its flexibility and versatility. The model can be extended by adding constituent spectra to explicitly model-known analytes or interferents. This paper addresses the use of constituent spectra and demonstrates common pitfalls. It clarifies the difference between analyte and interferent spectra, and the importance of orthogonality between model spectra. Different normalization approaches are discussed, and the importance of weighting in the EMSC is demonstrated. The paper illustrates how constituent analyte spectra can be estimated, and how they can be used to extract additional information from spectral features. It is shown that the EMSC parameters can be used in both regression tasks and segmentation tasks. 相似文献
45.
46.
Electronic and atomic structures of different terminations of the (0 0 1) non-polar orientation of BaZrO3 surfaces have been studied using first-principles calculations. We found that surface energies at both possible surface terminations, BaO and ZrO2, were very close. The (0 0 1)-BaO and (0 0 1)-ZrO2 terminated surfaces have bandgap values smaller than that of a bulk BaZrO3 crystal. In addition, the relative surface stability has been analyzed as a function of chemical environment. 相似文献
47.
Optical gap solitons, which exist due to a balance of nonlinearity and dispersion due to a Bragg grating, can couple to acoustic waves through electrostriction. This gives rise to a new species of "gap-acoustic" solitons (GASs), for which we find exact analytic solutions. The GAS consists of an optical pulse similar to the optical gap soliton, dressed by an accompanying phonon pulse. Close to the speed of sound, the phonon component is large. In subsonic (supersonic) solitons, the phonon pulse is a positive (negative) density variation. Coupling to the acoustic field damps the solitons' oscillatory instability, and gives rise to a distinct instability for supersonic solitons, which may make the GAS decelerate and change direction, ultimately making the soliton subsonic. 相似文献
48.
49.
Families of analytical solutions are found for symmetric and antisymmetric solitons in a dual-core system with Kerr nonlinearity and parity-time (PT)-balanced gain and loss. The crucial issue is stability of the solitons. A stability region is obtained in an analytical form, and verified by simulations, for the PT-symmetric solitons. For the antisymmetric ones, the stability border is found in a numerical form. Moving solitons of both types collide elastically. The two soliton species merge into one in the "supersymmetric" case, with equal coefficients of gain, loss, and intercore coupling. These solitons feature a subexponential instability, which may be suppressed by periodic switching ("management"). 相似文献
50.
Boris Baeumer Mark M. Meerschaert 《Journal of Computational and Applied Mathematics》2010,233(10):2438-2448
The space-fractional diffusion equation models anomalous super-diffusion. Its solutions are transition densities of a stable Lévy motion, representing the accumulation of power-law jumps. The tempered stable Lévy motion uses exponential tempering to cool these jumps. A tempered fractional diffusion equation governs the transition densities, which progress from super-diffusive early-time to diffusive late-time behavior. This article provides finite difference and particle tracking methods for solving the tempered fractional diffusion equation with drift. A temporal and spatial second-order Crank-Nicolson method is developed, based on a finite difference formula for tempered fractional derivatives. A new exponential rejection method for simulating tempered Lévy stables is presented to facilitate particle tracking codes. 相似文献