全文获取类型
收费全文 | 7923篇 |
免费 | 1304篇 |
国内免费 | 553篇 |
专业分类
化学 | 2621篇 |
晶体学 | 86篇 |
力学 | 1741篇 |
综合类 | 86篇 |
数学 | 755篇 |
物理学 | 4491篇 |
出版年
2024年 | 15篇 |
2023年 | 70篇 |
2022年 | 203篇 |
2021年 | 181篇 |
2020年 | 211篇 |
2019年 | 225篇 |
2018年 | 182篇 |
2017年 | 229篇 |
2016年 | 290篇 |
2015年 | 330篇 |
2014年 | 370篇 |
2013年 | 1058篇 |
2012年 | 447篇 |
2011年 | 547篇 |
2010年 | 386篇 |
2009年 | 435篇 |
2008年 | 422篇 |
2007年 | 454篇 |
2006年 | 391篇 |
2005年 | 391篇 |
2004年 | 379篇 |
2003年 | 286篇 |
2002年 | 286篇 |
2001年 | 246篇 |
2000年 | 180篇 |
1999年 | 153篇 |
1998年 | 198篇 |
1997年 | 169篇 |
1996年 | 133篇 |
1995年 | 132篇 |
1994年 | 112篇 |
1993年 | 119篇 |
1992年 | 99篇 |
1991年 | 66篇 |
1990年 | 54篇 |
1989年 | 48篇 |
1988年 | 57篇 |
1987年 | 38篇 |
1986年 | 34篇 |
1985年 | 30篇 |
1984年 | 25篇 |
1983年 | 5篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 7篇 |
1979年 | 17篇 |
1978年 | 7篇 |
1976年 | 4篇 |
1973年 | 4篇 |
1972年 | 5篇 |
排序方式: 共有9780条查询结果,搜索用时 15 毫秒
31.
32.
In the present paper, Daubechies' wavelets and the computation of their scaling coefficients are briefly reviewed. Then a new method of computation is proposed. This method is based on the work [7] concerning a new orthonormality condition and relations among scaling moments, respectively. For filter lengths up to 16, the arising system can be explicitly solved with algebraic methods like Gröbner bases. Its simple structure allows one to find quickly all possible solutions. 相似文献
33.
Eduardo Mizraji 《Complexity》2004,9(6):33-42
This work concerns the interaction between two classical problems: the forecasting of the dynamical behaviors of elementary cellular automata (ECA) from its intrinsic mathematical laws and the conditions that determine the emergence of complex dynamics. To approach these problems, and inspired by the theory of reversible logical gates, we decompose the ECA laws in a “spectrum” of dyadic Boolean gates. Emergent properties due to interactions are captured generating another spectrum of logical gates. The combined analysis of both spectra shows the existence of characteristic bias in the distribution of Boolean gates for ECA belonging to different dynamical classes. These results suggest the existence of signatures capable to indicate the propensity to develop complex dynamics. Logical gates “exclusive‐or” and “equivalence” are among these signatures of complexity. An important conclusion is that within ECA space, interactions are not capable to generate signatures of complexity in the case these signatures are absent in the intrinsic law of the automaton. © 2004 Wiley Periodicals, Inc. Complexity 9: 33–42, 2004 相似文献
34.
Alan L. Andrew 《BIT Numerical Mathematics》2003,43(3):485-503
The asymptotic correction technique of Paine, de Hoog and Anderssen can dramatically improve the accuracy of finite difference or finite element eigenvalues at negligible extra cost if closed form expressions are available for the errors in a simpler related problem. This paper gives closed form expressions for the errors in the eigenvalues of certain Sturm–Liouville problems obtained by various methods, thereby increasing the range of problems for which asymptotic correction can achieve maximum efficiency. It also investigates implementation of the method for more general problems. 相似文献
35.
36.
37.
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
38.
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
39.
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
40.