全文获取类型
收费全文 | 2001篇 |
免费 | 111篇 |
国内免费 | 160篇 |
专业分类
化学 | 689篇 |
晶体学 | 4篇 |
力学 | 500篇 |
综合类 | 15篇 |
数学 | 289篇 |
物理学 | 775篇 |
出版年
2024年 | 5篇 |
2023年 | 25篇 |
2022年 | 87篇 |
2021年 | 79篇 |
2020年 | 81篇 |
2019年 | 64篇 |
2018年 | 41篇 |
2017年 | 56篇 |
2016年 | 79篇 |
2015年 | 67篇 |
2014年 | 81篇 |
2013年 | 136篇 |
2012年 | 100篇 |
2011年 | 81篇 |
2010年 | 72篇 |
2009年 | 86篇 |
2008年 | 117篇 |
2007年 | 99篇 |
2006年 | 105篇 |
2005年 | 96篇 |
2004年 | 70篇 |
2003年 | 73篇 |
2002年 | 71篇 |
2001年 | 61篇 |
2000年 | 43篇 |
1999年 | 39篇 |
1998年 | 46篇 |
1997年 | 30篇 |
1996年 | 35篇 |
1995年 | 32篇 |
1994年 | 22篇 |
1993年 | 29篇 |
1992年 | 22篇 |
1991年 | 17篇 |
1990年 | 21篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1971年 | 4篇 |
排序方式: 共有2272条查询结果,搜索用时 109 毫秒
1.
通过改变带细玻璃管的烧瓶中水的温度导致水位变化来粗略演示水的收缩情况.为较准确测定水最大密度时的温度,将2个温度计放在水下较浅处和较深处,分别测量当温度经由4℃升高时和由4℃降低时两温度计的示数,进而验证水的反常热膨胀特性. 相似文献
2.
3.
4.
W. Hufenbach R. Böhm A. Langkamp L. Kroll T. Ritschel 《Mechanics of Composite Materials》2006,42(2):151-162
The basic damage and failure models of multiaxially reinforced composites with a thermoplastic matrix are presented and verified.
Within the framework of continuum damage mechanics, a phenomenological model is introduced, where the damage is defined as
a change in the elasticity tensor. For damage identification, a specific ultrasonic device was developed. A combination of
an immersion set-up and a contact coupling device formed a system for an efficient determination of stiffness-tensor components
from convenient sets of velocity measurements. Linked to a tensile machine, it allowed us to measure the anisotropic damage
of the new materials group caused by tensile loading.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 2, pp. 221–234, March–April, 2006. 相似文献
5.
Two tests for multivariate conditional heteroscedastic models are proposed. One is based on the cross-correlations of standardized squared residuals and the other is a score (Lagrange multiplier) test. The cross-correlations test can be used to detect the presence of multivariate conditional heteroscedasticity whereas the other test can be used for diagnostic checking. Simulation studies on the size and power of the test statistics are reported. The application of the tests is illustrated by an example using the S & P 500 and Sydney All Ordinary Indexes. 相似文献
6.
Temperature effects on deposition rate of silicon nitride films were characterized by building a neural network prediction model. The silicon nitride films were deposited by using a plasma enhanced chemical vapor deposition system and process parameter effects were systematically characterized by 26−1 fractional factorial experiment. The process parameters involved include a radio frequency power, pressure, temperature, SiH4, N2, and NH3 flow rates. The prediction performance of generalized regression neural network was drastically improved by optimizing multi-valued training factors using a genetic algorithm. Several 3D plots were generated to investigate parameter effects at various temperatures. Predicted variations were experimentally validated. The temperature effect on the deposition rate was a complex function of parameters but N2 flow rate. Larger decreases in the deposition rate with the temperature were only noticed at lower SiH4 (or higher NH3) flow rates. Typical effects of SiH4 or NH3 flow rate were only observed at higher or lower temperatures. A comparison with the refractive index model facilitated a selective choice of either SiH4 or NH3 for process optimization. 相似文献
7.
Summary We discuss a null experiment to search for the fifth force at ranges around 10 km. It is proposed to use a three-axis gravity
gradiometer to measure the trace of the Earth gravity tensor from a freely falling elevator dropped by a balloon. The main
error sources are considered to some extent.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
8.
J. Teixeira 《Il Nuovo Cimento D》1994,16(9):1433-1437
Summary The dynamics of water molecules occupying very small volumes can be probed by incoherent quasi-elastic neutron scattering.
We summarise some results obtained with wet samples of porous silica and hydrated proteins. The movements of the molecules
in the vicinity of the substrate are extremely reduced as compared to those of bulk water at the same temperature. Almost
only rotational movements subsist and the local diffusion is of the order of that observed in deeply supercooled water.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
9.
物理实验课程考核、评估体系初探 总被引:4,自引:0,他引:4
对物理实验课程考核、评估方法进行了探讨,提出了物理实验课程考核、评估体系及实施细则.重点介绍了体系中的核心部分——正规的物理实验课程考试. 相似文献
10.