全文获取类型
收费全文 | 423284篇 |
免费 | 33009篇 |
国内免费 | 18873篇 |
专业分类
电工技术 | 25349篇 |
技术理论 | 59篇 |
综合类 | 27554篇 |
化学工业 | 68469篇 |
金属工艺 | 24443篇 |
机械仪表 | 27512篇 |
建筑科学 | 33289篇 |
矿业工程 | 14018篇 |
能源动力 | 12508篇 |
轻工业 | 25230篇 |
水利工程 | 7705篇 |
石油天然气 | 26982篇 |
武器工业 | 3806篇 |
无线电 | 47540篇 |
一般工业技术 | 48638篇 |
冶金工业 | 21799篇 |
原子能技术 | 4630篇 |
自动化技术 | 55635篇 |
出版年
2024年 | 1680篇 |
2023年 | 6312篇 |
2022年 | 11230篇 |
2021年 | 15992篇 |
2020年 | 12319篇 |
2019年 | 10071篇 |
2018年 | 11404篇 |
2017年 | 13049篇 |
2016年 | 11762篇 |
2015年 | 16002篇 |
2014年 | 20729篇 |
2013年 | 24887篇 |
2012年 | 26958篇 |
2011年 | 29974篇 |
2010年 | 26369篇 |
2009年 | 25190篇 |
2008年 | 24900篇 |
2007年 | 24146篇 |
2006年 | 24473篇 |
2005年 | 21014篇 |
2004年 | 14016篇 |
2003年 | 12123篇 |
2002年 | 11080篇 |
2001年 | 9964篇 |
2000年 | 9889篇 |
1999年 | 10918篇 |
1998年 | 8892篇 |
1997年 | 7385篇 |
1996年 | 6860篇 |
1995年 | 5765篇 |
1994年 | 4711篇 |
1993年 | 3341篇 |
1992年 | 2662篇 |
1991年 | 2097篇 |
1990年 | 1607篇 |
1989年 | 1328篇 |
1988年 | 1069篇 |
1987年 | 721篇 |
1986年 | 582篇 |
1985年 | 359篇 |
1984年 | 261篇 |
1983年 | 227篇 |
1982年 | 211篇 |
1981年 | 148篇 |
1980年 | 144篇 |
1979年 | 74篇 |
1978年 | 36篇 |
1977年 | 46篇 |
1976年 | 58篇 |
1975年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
A locomotive cabin adsorption air‐conditioner has been equipped in #DF4B‐2369 locomotive; and has been successfully run for 2 years. It is powered by waste heat from the exhaust of the diesel engine. The influence on heat transfer is described by the equivalent heat transfer coefficient or thermal resistance of components inside the adsorber. The variation of adsorption capacity is expressed by a non‐equilibrium adsorption function. The dynamic heat transfer process of adsorption air‐conditioning system is treated with the lumped parameter method. Some typical running experimental results are present. The diesel engine rotating speed and locomotive speed influenced on the refrigeration system are discussed. The maximum mean refrigeration power is regarded as an objective function. Based on experiments and theoretical analysis, the running characteristics of the air‐conditioning system are optimized. Some techniques of performance improvement are suggested as well. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
4.
The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m?2 and 45 W m?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m?1 to 30.2 MPa and 158 J m?1, respectively. Copyright © 2003 Society of Chemical Industry 相似文献
5.
6.
7.
Studies on the deactivations and initiations of gas phase polymerizations of 1,3‐butadiene have been achieved by Monte Carlo simulation. Initiation and deactivation control the reaction before and after the peak of the polymerization rate, respectively. The influence of polymerization temperature has been studied. Monte Carlo modeling of polymerization kinetics and mechanism was confirmed by the agreement of experimental data and simulation results of polymerizations run with a temporary evacuation of monomer. The balance of catalysts and active chains is established by both initiation and chain transfer reactions with cocatalyst, which causes a ‘pseudo‐stability’ stage. © 2003 Society of Chemical Industry 相似文献
8.
第三节 常见氧化物膜目前研究最多的氧化物膜可谓二氧化硅和二氧化钛膜 ,这两种薄膜也是接受呈色离子、制备彩色镀膜常用的基体膜 ,所以 ,有必要将它们单独列出 ,加以讨论。1 二氧化钛膜在所有高折射率材料中 ,由钛的化合物制备的氧化物膜具有特殊的实际意义。因此 ,对二氧化 相似文献
9.
对在实际组网中选择合理的ASON架构和保护方式作了相应分析,并为搭建可向ASON平滑演进的传统网络时需注意的问题提供了参考意见, 相似文献
10.
We propose and evaluate a medium-access control (MAC) protocol for synchronous cellular packet direct-sequence code-division multiple-access (DS/CDMA). The protocol is designed for handling a variety of multimedia traffic types in an integrated wireless-access network (IWAN). For instance, the protocol is suited for carrying multiple traffic types of different priorities. An analytical model for the equilibrium state has been developed for the proposed protocol. A comparative evaluation of the protocol is done for three different radio frequency bandwidths currently under consideration for personal communication services (PCS), i.e., 1.25 MHz, 5 MHz, and 10 MHz. Our results demonstrate that the proposed protocol is both robust and flexible for the intended IWAN applications. It offers a significant multiplexing gain as the bandwidth increases 相似文献