全文获取类型
收费全文 | 29591篇 |
免费 | 2015篇 |
国内免费 | 1476篇 |
专业分类
电工技术 | 917篇 |
综合类 | 3339篇 |
化学工业 | 5417篇 |
金属工艺 | 3286篇 |
机械仪表 | 2074篇 |
建筑科学 | 1969篇 |
矿业工程 | 1415篇 |
能源动力 | 1695篇 |
轻工业 | 965篇 |
水利工程 | 486篇 |
石油天然气 | 1176篇 |
武器工业 | 234篇 |
无线电 | 1304篇 |
一般工业技术 | 3823篇 |
冶金工业 | 1907篇 |
原子能技术 | 385篇 |
自动化技术 | 2690篇 |
出版年
2024年 | 62篇 |
2023年 | 324篇 |
2022年 | 638篇 |
2021年 | 714篇 |
2020年 | 813篇 |
2019年 | 725篇 |
2018年 | 674篇 |
2017年 | 848篇 |
2016年 | 945篇 |
2015年 | 1023篇 |
2014年 | 1571篇 |
2013年 | 1740篇 |
2012年 | 1927篇 |
2011年 | 2303篇 |
2010年 | 1581篇 |
2009年 | 1764篇 |
2008年 | 1602篇 |
2007年 | 1877篇 |
2006年 | 1809篇 |
2005年 | 1589篇 |
2004年 | 1347篇 |
2003年 | 1169篇 |
2002年 | 977篇 |
2001年 | 736篇 |
2000年 | 657篇 |
1999年 | 592篇 |
1998年 | 477篇 |
1997年 | 421篇 |
1996年 | 374篇 |
1995年 | 341篇 |
1994年 | 301篇 |
1993年 | 223篇 |
1992年 | 197篇 |
1991年 | 173篇 |
1990年 | 132篇 |
1989年 | 112篇 |
1988年 | 91篇 |
1987年 | 49篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 31篇 |
1983年 | 17篇 |
1982年 | 27篇 |
1981年 | 15篇 |
1980年 | 7篇 |
1979年 | 16篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1959年 | 2篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
本文提出了求解非线性问题的一种新方法——逐次迭代法,本方法先是给出一个初始近似解,然后将这个近似解进行校正迭代,使之接近于真实解,把一个非线性问题转化为一个线性问题来解决。 相似文献
22.
PVDF中空纤维滤膜的形态结构 总被引:3,自引:0,他引:3
用L-S相转换法制备了聚偏氟乙烯(PVDF)中空纤维不对称滤膜。铸膜液由聚合物、溶剂和添加剂组成。用电子显微镜(SEM)考察了聚合物浓度、添加剂用量及种类对膜形态结构的影响。实验结果表明,聚合物浓度对膜形态结构有显著影响,当铸膜液中聚合物浓度较低时,无论用什么种类添加剂,都能形成大、且多的孔,但孔的形状随添加剂不同而异。当恒定聚合物浓度时,添加剂的用量对膜形态结构有很大的影响,但孔的大小及多少与添加剂含量的多少不成正比。 相似文献
23.
熔窑玻璃液流数值模拟的新发展 总被引:1,自引:0,他引:1
熔窑玻璃液流数值模拟的新发展赵国昌(清华大学核能技术设计研究院,100084)NewDevelopmentoftheNumericalSimulationforFlowandHeatTransferofGlassMeltinTankFurnace¥Z... 相似文献
24.
The high-temperature crystallization of poly(p-phenylene terephthalamide) (PPTA) from dilute organic solutions was achieved through the introduction of a non-solvent, or precipitating agent, at the desired crystallization temperature. The morphology and crystal structure were examined for crystals produced from PPTA polymer with two different molecular weights (Mw = 46000 and 3430 g mol−1), using transmission electron microscopy. For the high-molecular-weight polymer, ribbon-like crystals were produced, while the low-molecular-weight polymer yielded small needles or platelets. In both cases, electron diffraction showed that the Northolt allomorph was obtained. For the high-molecular-weight polymer, the molecular axes were parallel to the ribbon axes in a chain-extended type structure. A hypothesis for the orientation of the low-molecular-weight PPTA in the small platelets, is also given. 相似文献
25.
In order to cumpare the peformance of different supply diffuers of ventilation air, the airflow passern, temperature stratifiation and contaminant dispersion in a furnitured office ventilated by three kinds of air diffuer were numerically investigated. The air diffuers studied in this paper are a quarter-cylinder displacement diffuer on the floor and mixing diffuers (linear and vortex diffuers) on the ceiling. The heat sources in the of-fice are considered to be 50% convective and 50% radiative. The k-? two-equatwn model of turbulence is employed to predict the turbulent diffusion. The results show that the displacement diffuser provides a rather uniform flow field with low velocify in most areas, and the vertical temperature difference from floor to ceiling is as high as 6 K. With the linear diffuser, the air velociry is high, and the temperature is uniform both horizontally and vertically. The air velocity generated by the vortex diffuser is moderate. The distributions of the temperature and the contaminant are rather uniform. 相似文献
26.
A general numerical model is described for the dissolution kinetics of spherical particles in binary systems for any combination of first order reactions at the particle-matrix interface and long distance diffusion within the matrix. The model is applicable to both finite and infinite media and handles both complete and partial particle dissolution. It is shown that interfacial reactions can have a strong effect on the dissolution kinetics, the solute concentration at the particle-matrix interface and the solute concentration profile in the matrix. 相似文献
27.
28.
在氧化铝生产过程中,熟料折合比是烧结法一项重要的综合性指标,本文通过对熟料折合比的定义、计算公式的剖析,分析了生产过程中影响熟料折合比的主要因素,对有效降低熟料折合比的措施进行了探讨。 相似文献
29.
The viscometric, turbidimetric and potentiometric properties of copolymers of acrylamide (AM) with 2-acrylamido-2-methylpropanedimethylammonium chloride (AMPDAC) were studied in aqueous solutions. The AMPDAC polymers exhibit poor salt tolerance and large, negative viscosity/temperature coefficients. Furthermore, the polymers were found to be sensitive to changes in pH. The AMPDAC polymers undergo phase separation in the presence of dianions as a function of temperature and AMPDAC composition. 相似文献
30.
NUMERICAL ANALYSIS AND EXPERI- MENT OF UNSTEADY THERMAL FIELD OF ROTOR PLATE FOR EDDY CURRENT RETARDER 总被引:3,自引:0,他引:3
LIU Chengye HE Ren 《机械工程学报(英文版)》2008,21(4):71-75
The physical model based on heat transfer theory and virtual boundary method for analyzing unsteady thermal field of rotor plate for eddy current retarder used in automobile is established and boundary conditions are also defined. The finite element governing equation is derived by Galerkin method. The time differential item is discrete based on Galerkin format that is stable at any condition. And a new style of varying time step method is used in iteration process. The thermal field on the rotor plate at the radial and axle directions is analyzed and varying temperature at appointed points on two side-surfaces is measured. The testing and analytical data are uniform approximately. Finite element method can be used for estimating thermal field of the rotor plate at initial design stage of eddy current retarder. 相似文献