全文获取类型
收费全文 | 13481篇 |
免费 | 1512篇 |
国内免费 | 1073篇 |
专业分类
电工技术 | 400篇 |
综合类 | 1062篇 |
化学工业 | 3246篇 |
金属工艺 | 1813篇 |
机械仪表 | 369篇 |
建筑科学 | 724篇 |
矿业工程 | 212篇 |
能源动力 | 1241篇 |
轻工业 | 443篇 |
水利工程 | 327篇 |
石油天然气 | 374篇 |
武器工业 | 71篇 |
无线电 | 1205篇 |
一般工业技术 | 1987篇 |
冶金工业 | 447篇 |
原子能技术 | 477篇 |
自动化技术 | 1668篇 |
出版年
2024年 | 51篇 |
2023年 | 230篇 |
2022年 | 314篇 |
2021年 | 405篇 |
2020年 | 399篇 |
2019年 | 409篇 |
2018年 | 419篇 |
2017年 | 504篇 |
2016年 | 476篇 |
2015年 | 478篇 |
2014年 | 645篇 |
2013年 | 1232篇 |
2012年 | 811篇 |
2011年 | 900篇 |
2010年 | 713篇 |
2009年 | 778篇 |
2008年 | 753篇 |
2007年 | 824篇 |
2006年 | 729篇 |
2005年 | 614篇 |
2004年 | 576篇 |
2003年 | 481篇 |
2002年 | 406篇 |
2001年 | 355篇 |
2000年 | 339篇 |
1999年 | 267篇 |
1998年 | 252篇 |
1997年 | 227篇 |
1996年 | 185篇 |
1995年 | 190篇 |
1994年 | 142篇 |
1993年 | 132篇 |
1992年 | 109篇 |
1991年 | 120篇 |
1990年 | 113篇 |
1989年 | 101篇 |
1988年 | 75篇 |
1987年 | 49篇 |
1986年 | 36篇 |
1985年 | 52篇 |
1984年 | 40篇 |
1983年 | 20篇 |
1982年 | 28篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
程控电话交换机过电流保护元件用高性能PTC陶瓷的研制 总被引:3,自引:0,他引:3
阐述了高性能PTC陶瓷材料制备的基本要点,并以基方固溶体化学组成、原材料选择、复合添加物改性以及特定烧结工艺等方面开展工作,制得了居里温度为90℃左右、室温体积电阻率为30Ω·cm,电阻率突变ρνmax/ρνmin>105、电阻率温度系数α≈15%/℃、耐电压强度≥150V/mm的高性能PTC陶瓷材料。此材料制得的元件能满足程控电话交换机过电流保护的要求。 相似文献
102.
焊前处理方式对LF6铝合金扩散焊的影响 总被引:4,自引:0,他引:4
利用Gleeble-1500热/力模拟试验机,研究了LF6铝合金的扩散焊工艺,通过对焊接温度、压力、时间的调整和选用不同的料前处理方法,确定了最佳的扩散规范,研究结果表明:在一定的温度和时间范围内,LF65铝合金扩散焊接头的剪切哟度随焊接温度和时间的增加而提高;化学浸蚀法比机械打磨法能更有效的去除铝合金表面的氧化膜;在现有试验条件下,得到LF6铝合金扩散焊的最佳规范参数,搭接试扩散焊接头的剪切强度 相似文献
103.
Anatoly M. Dolgonosov Ruslan Kh. Khamizov Anna N. Krachak Andrei G. Prudkovsky 《Reactive and Functional Polymers》1995,28(1)
A model for multispecies ion-exchange kinetics based on the Nernst-Planck equation is suggested. It is analyzed in comparison with the “locally-determinate” model described by Hwang and Helfferich [1]. The model makes possible simple computation. The conditions for the occurrence of unusual kinetic curves with a maximum are clarified. The proposed model is developed for different types of kinetic problems and verified by the experimental investigation of a kinetics in ternary systems. 相似文献
104.
将气体动压轴压简化为转化气膜系统后,针对其动力特点,给出气膜在微幅振动下动压轴承的实用数学模型和测定动态参数的方法,并进行了测量误差的修正。 相似文献
105.
106.
Thermal conductivity, viscosity, and self-diffusion coefficient data for liquid n-alkanes are satisfactorily correlated simultaneously by a method based on the hard-sphere theory of transport properties. Universal curves are developed for the reduced transport properties
*,
*, and D
* as a function of the reduced volume. A consistent set of equations is derived for the characteristic volume and for the parameters R
, R
, and R
D, introduced to account for the nonsphericity and roughness of the molecules. The temperature range of the above scheme extends from 110 to 370 K, and the pressure range up to 650 MPa. 相似文献
107.
Milton E. Rose 《Journal of scientific computing》1990,5(2):169-185
A compact finite-difference scheme to solve one-phase Stefan problems in one dimension is described. Numerical experiments indicate that the moving interface is obtained withO(t) accuracy when 3–4 iterations per time step are used to solve the nonlinear implicit scheme. The scheme can be adapted to ADI methods in higher dimensions. 相似文献
108.
Equations of state and contact values of hard-sphere radial distribution functions (rdf's) which are given by a linear combination of the Percus— Yevick and scaled-particle virial expressions are considered. In the one-component case the mixing coefficient() is, in general, a function of the volume fraction. In mixtures the coefficient(
i
,d
i
), in general, depends upon the volume fraction
i
, and diameterd
i
, of each species,i andj. For the contact valuesY
ij
of the rdf's, the mixing coefficients
ij
(
k
) also depend on speciesi andj. Density expansions for the exact for the one-component hard-sphere fluid are obtained and compared with several approximations made in earlier works and in our own work, as well as with simulations. For a mixture, it turns out that one cannot obtain the exact fourth virial coefficient by using a linear combination of the Percus-Yevick and scaled-particle virial expressions forY
ij
unless one allows
ij
to depend on mole fractionsx
i
even at the zeroth order of its density expansion. We also find that
ij
must depend on particle speciesi andj in order to satisfy the exact limits obtained earlier by Sung and Stell. A new equation of state for the binary hard-sphere mixture which satisfies all the exact limits we have considered is suggested.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
109.
E. I. Leyarovski J. K. Georgiev A. L. Zahariev 《International Journal of Thermophysics》1988,9(3):391-408
A new method for experimental determination of the thermal diffusion factor
T for binary gas mixtures with a thermal diffusion column (TDC) is developed, based on A. M. Rozen's equation of TDC. The experimental results for
T are obtained in a reduced form in this approximation. An experimental reference point, determined in the same TDC with a standard gas mixture, is used for the transformation of the results for
T in absolute units. The proposed method is applicable for arbitrary gas mixtures, irrespective of the mass difference of the components. 相似文献
110.
D. D. Palmer D. K. Rehbein J. F. Smith O. Buck 《Journal of Nondestructive Evaluation》1988,7(3-4):167-174
It has been shown that the acoustic response of imperfect interfaces may be described by a quasi-static spring model. In the present paper, experimental data on the geometry of the contacts between two diffusion-bonded blocks have been used to determine the spring stiffness of such interfaces which have been correlated with experimentally determined ultrasonic reflection coefficients. The correlation between the theoretical reflection coefficient and the spring stiffness was found to be in excellent agreement with experimentally-observed values, if the disbonds are of infinitesimally small thickness. For disbonds of finite thickness, the agreement is less satisfactory. Reasons for the discrepancy in the latter case are unknown at the present time. 相似文献