全文获取类型
收费全文 | 36224篇 |
免费 | 7029篇 |
国内免费 | 5755篇 |
专业分类
化学 | 26918篇 |
晶体学 | 577篇 |
力学 | 2330篇 |
综合类 | 395篇 |
数学 | 4031篇 |
物理学 | 14757篇 |
出版年
2024年 | 108篇 |
2023年 | 659篇 |
2022年 | 1308篇 |
2021年 | 1370篇 |
2020年 | 1475篇 |
2019年 | 1532篇 |
2018年 | 1329篇 |
2017年 | 1370篇 |
2016年 | 1795篇 |
2015年 | 1983篇 |
2014年 | 2414篇 |
2013年 | 2997篇 |
2012年 | 3494篇 |
2011年 | 3534篇 |
2010年 | 2623篇 |
2009年 | 2688篇 |
2008年 | 2903篇 |
2007年 | 2413篇 |
2006年 | 2241篇 |
2005年 | 1801篇 |
2004年 | 1348篇 |
2003年 | 1132篇 |
2002年 | 1144篇 |
2001年 | 927篇 |
2000年 | 748篇 |
1999年 | 619篇 |
1998年 | 445篇 |
1997年 | 403篇 |
1996年 | 355篇 |
1995年 | 286篇 |
1994年 | 289篇 |
1993年 | 225篇 |
1992年 | 176篇 |
1991年 | 143篇 |
1990年 | 139篇 |
1989年 | 90篇 |
1988年 | 80篇 |
1987年 | 62篇 |
1986年 | 70篇 |
1985年 | 47篇 |
1984年 | 24篇 |
1983年 | 28篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 19篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1957年 | 8篇 |
1925年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
本文得到Ω满足Dini型条件时,Marcinkiewicz积分交换子μΩ,b(f)的端点估计:|{x∈R~n:μΩ,b(f)(x)>λ}|≤c‖b‖BMO∫_(R~n)(|f(x)|)/λ(1+log+(|f(x)|)/λ)dx. 相似文献
143.
汪巍 《数学的实践与认识》2004,34(3):103-109
首先引入了差分系统基于两种度量的极端稳定性概念 ,然后建立了一些关于差分系统 ( h0 ,h)极端稳定性 (极端一致稳定性 ,极端渐近稳定性 ,极端一致渐近稳定性 )的判定准则 .在所得到的定理中 ,对△ V的限制较弱 ,特别地 ,△V甚至可以恒为正 ,从而便于实际应用 . 相似文献
144.
145.
The specific heat and related thermophysical properties of liquid Fe77.5Cu13Mo9.5 monotectic alloy were investigated by an electromagnetic levitation drop calorimeter over a wide temperature range from 1482 to 1818 K. A maximum undercooling of 221 K (0.13 Tm) was achieved and the specific heat was determined as 44.71 J·mol-1·K-1. The excess specific heat, enthalpy change, entropy change and Gibbs free energy difference of this alloy were calculated on the basis of experimental results. It was found that the calculated results by traditional estimating methods can only describe the solidification process under low undercooling conditions. Only the experimental results can reflect the reality under high undercooling conditions. Meanwhile, the thermal diffusivity, thermal conductivity, and sound speed were derived from the present experimental results. Furthermore, the solidified microstructural morphology was examined, which consists of (Fe) and (Cu) phases. The calculated interface energy was applied to exploring the correlation between competitive nucleation and solidification microstructure within monotectic alloy. 相似文献
146.
Numerical studies were conducted to investigate the natural convection heat transfer around a uniformly heated thin plate
with arbitrary inclination in an infinite space. The numerical approach was based on the finite volume technique with a nonstaggered
grid arrangement. For handling the pressure–velocity coupling the SIMPLE-algorithm was used. QUICK scheme and first order
upwind scheme were employed for discretization of the momentum and energy convective terms respectively. Plate width and heating
rate were used to vary the modified Rayleigh number over the range of 4.8×106 to 1.87×108. Local and average heat transfer characteristics were compared with regarding to the inclination angle. The empirical expressions
for local and average Nusselt number were correlated. It has been found that for inclination angle less than 10∘, the flow and heat transfer characteristics are complicated and the average Nusselt number can not be correlated by one equation
while for inclination angle larger than 10∘, the average Nusselt number can be correlated into an elegant correlation.
Received on 18 April 2001 / Published online: 29 November 2001 相似文献
147.
148.
魏嵬 《数学的实践与认识》2007,37(16):76-83
为给转炉设计提供依据,需要计算炉液倾动的重心.利用数学方法将实际问题进行简化,通过分析炉液倾动过程中变量间的相互关系,来确定每个倾动角度对应情况下的液面位置.利用数学中三重积分的有关应用,进一步得出转炉在每个倾动角度为α∈(0,π2)时的重心计算方法及相关结论,在理论上为工程计算重心的方法提供参考. 相似文献
149.
Diane L. Levesque Eng-Chi Wang Dau-Chang Wei Cherng-Chyi Tzeng Raymond P. Panzica Fardos N. M. Naguib Mahmoud H. El Kouni 《Journal of heterocyclic chemistry》1993,30(5):1399-1404
A new series of potent uridine phosphorylase inhibitors have been prepared from barbituric acid. Among them, 1-[(2-hydroxyethoxy)methyl]-5-)(m--benzyloxy)benzylbarbituric acid ( 37 , BBBA) is the most promising having a Ki value of 1.1 ± 0.2 nM with uridine phosphorylase from human liver. The new inhibitors are easily synthesized and are better inhibitors of human uridine phosphorylase than their uracil counterparts. 相似文献
150.