全文获取类型
收费全文 | 16913篇 |
免费 | 2831篇 |
国内免费 | 2124篇 |
专业分类
化学 | 7167篇 |
晶体学 | 198篇 |
力学 | 1801篇 |
综合类 | 169篇 |
数学 | 2225篇 |
物理学 | 10308篇 |
出版年
2024年 | 27篇 |
2023年 | 155篇 |
2022年 | 372篇 |
2021年 | 417篇 |
2020年 | 510篇 |
2019年 | 368篇 |
2018年 | 385篇 |
2017年 | 453篇 |
2016年 | 483篇 |
2015年 | 566篇 |
2014年 | 764篇 |
2013年 | 1373篇 |
2012年 | 921篇 |
2011年 | 1169篇 |
2010年 | 970篇 |
2009年 | 1131篇 |
2008年 | 1159篇 |
2007年 | 1213篇 |
2006年 | 1122篇 |
2005年 | 1013篇 |
2004年 | 842篇 |
2003年 | 857篇 |
2002年 | 755篇 |
2001年 | 612篇 |
2000年 | 604篇 |
1999年 | 510篇 |
1998年 | 476篇 |
1997年 | 409篇 |
1996年 | 346篇 |
1995年 | 271篇 |
1994年 | 259篇 |
1993年 | 190篇 |
1992年 | 201篇 |
1991年 | 141篇 |
1990年 | 106篇 |
1989年 | 106篇 |
1988年 | 82篇 |
1987年 | 69篇 |
1986年 | 56篇 |
1985年 | 86篇 |
1984年 | 52篇 |
1983年 | 24篇 |
1982年 | 61篇 |
1981年 | 30篇 |
1980年 | 21篇 |
1979年 | 24篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 20篇 |
1973年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Werner WinterGünther W.H Höhne 《Thermochimica Acta》2003,403(1):43-53
A method for measuring heat capacities of small samples using a chip-calorimeter and a heat pulse technique is described. The theoretical background to calculate the heat transport properties and the heat capacity of the sample from the pulse response function is given. Problems and potentials of the method are discussed. An example is given. 相似文献
92.
Ekatherina A. Karatsuba 《Numerical Algorithms》2007,45(1-4):127-137
A new approach to the study of the Jaynes–Cummings sum, which determines the atomic inversion in quantum model of a single
two-level atom interacting with a single mode of the quantized radiation field, based on the number theory theorems on approximation
of trigonometric sums is presented.
相似文献
93.
PURE STATE APPROACH TO C(x)_αZ_nLIBINGREN;LINQING(InstituteofMathematics,AcademiaSinica,Beijing100080,China.Projectsupportedbyth?.. 相似文献
94.
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
95.
Qingrong Zheng Gang Su Jian Wang Hong Guo 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,25(2):233-238
We report a theoretical analysis of the phonon thermal conductance, κ(T), for single wall carbon nanotubes (SWCN). In a range of low temperatues up to 100 K, κ(T) of perfect SWCN is found to increase with temperature, approximately, in a parabolic fashion. This is qualitatively consistent
with recent experimental measurements where the tube-tube interactions are negligibly weak. When the carbon-carbon bond length
is slightly varied, κ(T) is found to be qualitatively unaltered which implies that the anharmonic effect does not change the qualitative behavior
of κ(T).
Received 12 June 2001 相似文献
96.
章志飞 《浙江大学学报(理学版)》2003,30(6):609-611
利用Besov空间的热核刻画及压缩映射原理,研究半线性热方程ut-△u=u|u|a的初值问题,得到了当初值u0∈Lp0(Rn)且||u0||(B·)p-n (1/p0-1/p),∞(Rn)(p0=na/2,p>p0)充分小时,整体解的存在性及在一定条件下解的惟一性. 相似文献
97.
应用电磁线路中涨落耗散理论,推导了不同温度均匀二半空间接触后产生辐射场密度的公式。将此公式近似展开后,即得Grover和Urtiew所获得的表示式,不过多了一松弛项,该项如用非富里叶热传导理论推导,也是存在的。该结果和实验结果一致,不过这里的松驰时间可以应用介质性质进行计算。 相似文献
98.
Auguet C. Martorell F. Moll F. Torra V: 《Journal of Thermal Analysis and Calorimetry》2002,70(1):277-290
The miniaturized calorimetric devices furnish a reduced working flat surface and permits measurements with extremely low-mass
quantities. The experimental sensitivity shows relevant position dependence with x-y surface coordinates and with z-distance. The device identification is realized via a 2-D model based in Fourier general equation.
Using the Marquardt method the experimental flat surface device can be identified and the fitted parameters used to simulate
the behavior of the experimental system. From the model, the effects of several dissipation configurations can be evaluated.
Also, via the RC-analogy, a way to 3-D experimental devices is roughly described.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
99.
在电流及温度分布满足“不变性”原理的基础上,本文分析了等离子体中心热区的能量平衡,求出了电子热传导系数,根据实验数据拟合出HL-1装置电子热传导系数的定标关系为X_e=6.8(n_(eq1))~(-1.2)。此关系与其他托卡马克装置的结果类似。 相似文献
100.
Heat transfer in lattice BGK modeled fluid 总被引:1,自引:0,他引:1
The thermal lattice BGK model is a recently suggested numerical tool aiming at solving problems of thermohydrodynamics. The quality of the lattice BGK simulation is checked in this paper by calculating temperature profiles in the Couette flow under different Eckert and Mach numbers. A revised lower order model is proposed to improve the accuracy and the higher order model is proved to be advantageous in this respect, especially in the flow regime with a higher Mach number. 相似文献