全文获取类型
收费全文 | 99925篇 |
免费 | 12567篇 |
国内免费 | 6909篇 |
专业分类
电工技术 | 10835篇 |
技术理论 | 4篇 |
综合类 | 11094篇 |
化学工业 | 9055篇 |
金属工艺 | 8622篇 |
机械仪表 | 10220篇 |
建筑科学 | 6849篇 |
矿业工程 | 6041篇 |
能源动力 | 5800篇 |
轻工业 | 1582篇 |
水利工程 | 3954篇 |
石油天然气 | 5722篇 |
武器工业 | 3501篇 |
无线电 | 9484篇 |
一般工业技术 | 8957篇 |
冶金工业 | 3243篇 |
原子能技术 | 1561篇 |
自动化技术 | 12877篇 |
出版年
2024年 | 525篇 |
2023年 | 1565篇 |
2022年 | 2952篇 |
2021年 | 3279篇 |
2020年 | 3564篇 |
2019年 | 2657篇 |
2018年 | 2662篇 |
2017年 | 3532篇 |
2016年 | 4208篇 |
2015年 | 4617篇 |
2014年 | 6847篇 |
2013年 | 6568篇 |
2012年 | 8244篇 |
2011年 | 8907篇 |
2010年 | 6446篇 |
2009年 | 6417篇 |
2008年 | 5961篇 |
2007年 | 7391篇 |
2006年 | 6349篇 |
2005年 | 5100篇 |
2004年 | 4283篇 |
2003年 | 3406篇 |
2002年 | 2706篇 |
2001年 | 2238篇 |
2000年 | 1804篇 |
1999年 | 1433篇 |
1998年 | 1116篇 |
1997年 | 909篇 |
1996年 | 820篇 |
1995年 | 649篇 |
1994年 | 542篇 |
1993年 | 353篇 |
1992年 | 290篇 |
1991年 | 227篇 |
1990年 | 192篇 |
1989年 | 162篇 |
1988年 | 109篇 |
1987年 | 56篇 |
1986年 | 67篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1983年 | 32篇 |
1982年 | 24篇 |
1981年 | 14篇 |
1980年 | 18篇 |
1979年 | 18篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1959年 | 21篇 |
1951年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
T.L. Phillips 《Polymer》2005,46(24):11035-11050
Results are presented from atomistic molecular dynamics simulations of the mobile pseudo-hexagonal phase of polyethylene, which occurs under conditions of elevated pressure and temperature. Three different types of model are considered, all of which employ periodic boundary conditions. The first model consists of n-alkane sequences (48×-C24H48-) that are bonded across the simulation box boundaries to produce chains that are effectively infinite in extent. On heating, at high pressure, this system displays a rotator phase, in which the chains retain an all-trans conformation, and rotate as semi-rigid units. A second model, consisting of finite n-alkanes (48×C24H50) displays the same behaviour at low temperatures, but at high temperature and pressure forms a conformationally disordered rotator phase, characterised by a large proportion of gauche defects and a significant lattice expansion. The final model considered contains long n-alkanes (24×C102H206) which contain jog defects and each pass twice through the simulation box. This model forms a conformationally disordered rotator phase at high temperature and ambient pressure. The behaviour of the three models, in terms of the variations in chain conformation and rotational and translational dynamics, are compared. The conformationally disordered phases provide useful representations of the experimentally observed mobile phase. 相似文献
32.
介绍了Multisim8的仿真功能的特点,并通过实例说明了用Multisim8进行仿真分析的具体方法,简单介绍了如何设置参数和进行仿真操作。 相似文献
33.
Specific interactions in blends containing Chitosan and functionalized polymers. Molecular dynamics simulations 总被引:2,自引:0,他引:2
Chitosan (CS)/poly(vinyl alcohol) (PVA) and Chitosan/poly(2-hydroxyethyl methacrylate) (P2HEM) blends have been studied through molecular dynamic simulations. In a previous work it was found miscibility between these polymers and it was attributed to hydrogen bonding formation. However, the experimental information obtained was not enough to know which of the interacting groups of Chitosan, i.e. -CH2OH or -NH2, are responsible of the interaction. Therefore, we have performed molecular dynamics simulation runs of 1 ns in order to calculate radial distribution functions (RDF) for the groups tentatively involved in the interaction. The results are correlated with our previous experimental data. This way, we have obtained a more precise conclusive information about the interactions involved as function of the blends composition. For low compositions of PVA and P2HEM the interaction is predominantly with the hydroxymethyl groups of CS while as the composition of PVA and P2HEM increases, the interaction with the amine groups increases. 相似文献
34.
基于Protel DXP的电路仿真设计 总被引:6,自引:0,他引:6
Protel DXP是集所有设计工具于一身的电子设计自动化(EDA)软件.文中运用其内嵌的仿真器叙述了分压式偏置电路放大器的仿真设计过程,设计过程简单、方便.在电子线路理论教学过程中引入电路设计仿真环节在不同情况下对电路进行实时分析,不仅可以提高学生的学习兴趣,而且能够在较短时间内加深学生对理论知识的理解;在工程设计过程中利用仿真工具对电路进行即时测试,可以缩短设计周期,提高设计效率. 相似文献
35.
36.
Iwao Shimizu Yuji Naito Iwao Yamaguchi Katsuyuki Kaiho Hitoshi Mizoguchi Satoru Yanabu 《Electrical Engineering in Japan》2008,164(1):52-61
Using conventional high‐temperature superconducting wire, a model superconducting fault current limiter (SFCL) is made and tested. Solenoid coil using Bi2223 silver sheath wire is so made that inductance is as small as possible and a vacuum interrupter is connected in series to it. A conventional reactor coil is connected in parallel. When the fault current flows in this equipment, superconducting wire is quenched and current is transferred into the parallel coil because of voltage drop of superconducting wire. This large current in parallel coil actuates magnetic repulsion mechanism of vacuum interrupter. Due to opening of vacuum interrupter, the current in superconducting wire is broken. By using this equipment, current flow time in superconducting wire can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of parallel coil. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(1): 52–61, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20315 相似文献
37.
目前的电路仿真软件通常是在电路中所有元件值都是给定的情况下得到一些数值结果,而非解析结果。该文利用Matlab的符号运算功能编程,通过节点列表法,实现了任意线性电路的自动解析求解,为电路分析提供了一个有效的辅助工具。 相似文献
38.
39.
A. F. Kurbatskii 《High Temperature》2004,42(1):79-87
The difference in the turbulent diffusion between the active (heat) and passive (mass) scalars in a thermally stably stratified medium is investigated. The axisymmetric problem is treated on the formation of a turbulent circulation flow above a heated disk and on the turbulent diffusion of a passive scalar (impurity) from a continuous surface source in a stably stratified medium. The results indicate that the thermal stratification causes appreciable differences in the coefficients of turbulent transfer between the active (heat) and passive (mass) scalars. This means that the assumption of the identity of the coefficient of turbulent diffusion of heat and mass, employed in conventional models of turbulence, produces significant errors in estimating the heat and mass transfer in a thermally stably stratified medium. 相似文献
40.