全文获取类型
收费全文 | 13383篇 |
免费 | 2248篇 |
国内免费 | 1011篇 |
专业分类
化学 | 4465篇 |
晶体学 | 121篇 |
力学 | 3745篇 |
综合类 | 231篇 |
数学 | 2063篇 |
物理学 | 6017篇 |
出版年
2024年 | 14篇 |
2023年 | 107篇 |
2022年 | 250篇 |
2021年 | 342篇 |
2020年 | 430篇 |
2019年 | 349篇 |
2018年 | 353篇 |
2017年 | 467篇 |
2016年 | 565篇 |
2015年 | 567篇 |
2014年 | 596篇 |
2013年 | 1532篇 |
2012年 | 767篇 |
2011年 | 834篇 |
2010年 | 626篇 |
2009年 | 716篇 |
2008年 | 694篇 |
2007年 | 709篇 |
2006年 | 725篇 |
2005年 | 663篇 |
2004年 | 613篇 |
2003年 | 561篇 |
2002年 | 462篇 |
2001年 | 428篇 |
2000年 | 393篇 |
1999年 | 342篇 |
1998年 | 338篇 |
1997年 | 277篇 |
1996年 | 243篇 |
1995年 | 252篇 |
1994年 | 202篇 |
1993年 | 199篇 |
1992年 | 166篇 |
1991年 | 130篇 |
1990年 | 118篇 |
1989年 | 81篇 |
1988年 | 114篇 |
1987年 | 69篇 |
1986年 | 52篇 |
1985年 | 55篇 |
1984年 | 47篇 |
1983年 | 14篇 |
1982年 | 44篇 |
1981年 | 32篇 |
1980年 | 11篇 |
1979年 | 21篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1957年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
71.
72.
In the present paper, a new two-parameter inverted equation of state (EOS) is developed which is found to be working very
well in the high-pressure region. To check its success and validity, this EOS has been applied in a number of solids. The
computed volume compression is found to be in very good agreement with the experimental data in the whole range of pressure
in all the solids. The minimum and the maximum pressure range used in the present study is 0–320 kbar and 0–3000 kbar, respectively. 相似文献
73.
L. Erbe A. Peterson S.H. Saker 《Journal of Mathematical Analysis and Applications》2007,329(1):112-131
In this paper, we extend the oscillation criteria that have been established by Hille [E. Hille, Non-oscillation theorems, Trans. Amer. Math. Soc. 64 (1948) 234-252] and Nehari [Z. Nehari, Oscillation criteria for second-order linear differential equations, Trans. Amer. Math. Soc. 85 (1957) 428-445] for second-order differential equations to third-order dynamic equations on an arbitrary time scale T, which is unbounded above. Our results are essentially new even for third-order differential and difference equations, i.e., when T=R and T=N. We consider several examples to illustrate our results. 相似文献
74.
75.
Eugene Savov 《Complexity》2007,12(3):61-76
The solar wind makes the magnetosphere to expand and contract as indicated by the expansions and contractions of the auroral oval due to balancing of the dynamic pressure of the ambient space plasma at inner and outer magnetic lines. This self‐similar magnetospheric behavior elucidates the controversial magnetic storm‐substorm relationship and reveals the 3D‐spiral structure of magnetic interaction. The found self‐similarly evolving structure of one seen as fundamental interaction suggests dynamic fractal unifying interaction that builds a firework universe having 3D‐spiral code. The unifying interaction is described with equation drawn in new fundamental dynamic fractal framework. The equation of unifying interaction converges to the inverse square laws and the principle of uncertainty at laboratory scales. The dynamic fractal fundamental framework is made of one 3D‐spirally‐faster‐inward contracting and expanding, oscillating, basic matter. It simply accounts for observed constant speed of light and for the creation of bright and dark bands on a screen behind a tiny slit. The dynamic fractal framework is quantitatively confirmed with the orbital data for the Milky Way Galaxy, the Sun, the Earth, and the triple asteroid system 87 Sylvia. Many testable predictions are also made. The presented new fundamental dynamic fractal framework allows qualitative and quantitative modeling and simplification. © 2007 Wiley Periodicals, Inc. Complexity 12: 61–76, 2007 相似文献
76.
Belting, a vocal technique typically cultivated in musical theatre singing, differs timbrally from operatic singing in many interesting respects. The underlying phonatory differences have not been previously investigated in detail. Yet, belting is frequently associated with disturbances of voice function. Articulatory and phonatory characteristics are investigated in a female subject who is a professional singer (co-author JL) trained in both the operatic and belting styles and in an intermediate vocal technique (“mixed”). This article presents data obtained from this subject by video-fiberoptic observation of the pharynx, inverse filtering of airflow, and measurement of subglottal pressure. The results reveal that belting was characterized by very high subglottal pressures and sound levels, and apparently also by a comparatively high degree of glottal adduction. Comparisons with other investigations of related aspects of belting and operatic singing support the assumption that the data obtained from our subject are representative for these vocal techniques. 相似文献
77.
本文采用高压X光衍射方法在金刚石对顶压砧中在位地(in situ)研究了Fe68Co24Ni8(wt%)合金在室温下的压致bcc→hcp结构相变和直到40.5 GPa的等温压缩行为。实验结果表明该合金在常压下为bcc结构,晶格常数a0=(0.287 0±0.000 1) nm,体积V0=(7.119±0.007) cm3/mol,密度ρ0=(7.981±0.008) g/cm3;在20.9 GPa附近出现bcc→hcp结构相变,两相共存压力区约10 GPa,在此区域内有晶面间距d(002)hcp=d(110)bcc,且原子平面(002)hcp//(110)bcc,hcp相比bcc相体积减小(0.33±0.02) cm3/mol;高压相hcp结构的晶格参数比值c/a=1.608±0.004;相变后原子配位数的增加使得hcp相(002)平面内及(002)平面间的最近邻原子间距比bcc相最近邻原子间距分别增大约1.6%和0.5%;用Murnaghan状态方程对实验数据进行最小二乘法拟合,得到bcc相B0=(130±13) GPa,B0'=12.6±0.5;hcp相V0=(6.62±0.04) cm3/mol,B0=(243±21) GPa,B0'=6.8±0.3;对于该合金的bcc→fcp相变时的结构转变机制做了详细的讨论。 相似文献
78.
Jesús M. Velásquez Bermúdez 《Annals of Operations Research》2002,117(1-4):21-31
This document presents theoretical considerations about the solution of dynamic optimization problems integrating the Benders Theory, the Dynamic Programming approach and the concepts of Control Theory. The so called Generalized Dual Dynamic Programming Theory (GDDP) can be considered as an extension of two previous approaches known as Dual Dynamic Programming (DDP): The first is the work developed by Pereira and Pinto [3–5], which was revised by Velásquez and others [8,9]. The second is the work developed by Read and others [2,6,7]. 相似文献
79.
80.