全文获取类型
收费全文 | 197679篇 |
免费 | 19643篇 |
国内免费 | 11788篇 |
专业分类
电工技术 | 15796篇 |
技术理论 | 4篇 |
综合类 | 16422篇 |
化学工业 | 28426篇 |
金属工艺 | 11710篇 |
机械仪表 | 13088篇 |
建筑科学 | 16260篇 |
矿业工程 | 6361篇 |
能源动力 | 5824篇 |
轻工业 | 15528篇 |
水利工程 | 4850篇 |
石油天然气 | 10014篇 |
武器工业 | 2207篇 |
无线电 | 23711篇 |
一般工业技术 | 20101篇 |
冶金工业 | 7907篇 |
原子能技术 | 2251篇 |
自动化技术 | 28650篇 |
出版年
2024年 | 935篇 |
2023年 | 3158篇 |
2022年 | 6257篇 |
2021年 | 8669篇 |
2020年 | 6544篇 |
2019年 | 5086篇 |
2018年 | 5658篇 |
2017年 | 6749篇 |
2016年 | 5835篇 |
2015年 | 8709篇 |
2014年 | 10999篇 |
2013年 | 13095篇 |
2012年 | 15199篇 |
2011年 | 15887篇 |
2010年 | 14771篇 |
2009年 | 13900篇 |
2008年 | 13744篇 |
2007年 | 12985篇 |
2006年 | 11904篇 |
2005年 | 9424篇 |
2004年 | 6590篇 |
2003年 | 5491篇 |
2002年 | 5221篇 |
2001年 | 4551篇 |
2000年 | 3753篇 |
1999年 | 3093篇 |
1998年 | 2048篇 |
1997年 | 1697篇 |
1996年 | 1587篇 |
1995年 | 1338篇 |
1994年 | 1083篇 |
1993年 | 704篇 |
1992年 | 572篇 |
1991年 | 421篇 |
1990年 | 305篇 |
1989年 | 275篇 |
1988年 | 210篇 |
1987年 | 123篇 |
1986年 | 114篇 |
1985年 | 56篇 |
1984年 | 46篇 |
1983年 | 31篇 |
1982年 | 39篇 |
1981年 | 42篇 |
1980年 | 46篇 |
1979年 | 27篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1959年 | 11篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
(接上期)
8卷边和切口
尽量不要广泛使用卷边,因为切割不恰当的卷边有潜在的危险。在构件安装到位后,加强杆或横梁的坡口焊缝处总免不了要用卷边,就像纵向加强杆或舱底龙骨这种情况(图11)。 相似文献
93.
CR/MMA乳液接枝共聚物的研制 总被引:1,自引:0,他引:1
用乳液接枝共聚法制备CR/MMA共聚物,讨论CR乳液、引发剂、接枝温度、MMA用量对接枝共聚转化率,接枝MMA含量、MMA接枝效率和粘接性能的影响,用红外光谱对接枝共聚物进行表征,该共聚物具有较好的粘接性能。 相似文献
94.
95.
Wei Li 《Chemical engineering science》2005,60(17):4780-4790
A mathematical model for flowthrough (perfusion) chromatography, namely packed-microtubes (PMT) model, has been proposed for a column packed with biporous (BiP) anion exchanger in which the mesopores and flowthrough pores are created with liquid and solid porogens, respectively. The model is established based on the assumption that the BiP particle is made up of packed microtubes. Bovine serum albumin (BSA) is used as a model protein and three kinds of anion exchangers (i.e., mesoporous, macroporous and BiP resins) are used as adsorbents to determine the model parameters and to evaluate the model. Adsorption equilibrium and finite bath experiments are performed to determine the adsorption isotherms and kinetics parameters. Both the bound amounts of the protein on the surface of the mesopores and macropores are experimentally determined and taken into account in the mathematical model. With all the model parameters determined by independent experiments or calculated from available correlations, model simulations are performed and compared with the experimentally determined breakthrough profiles of the BiP column. It is found that the model predictions agree reasonably well with the experimental data obtained under various conditions and the PMT model fit experimental data better than the modified double linear driving force (LLDF) model proposed by Leitão and Rodriogues (1999. Biochemical Engineering Journal 3, 131) in which the adsorbent particle is considered to be made up of packed microparticles. The results indicate that the PMT model is more reasonable for this kind of BiP adsorbent. 相似文献
96.
97.
The secure operation of autonomous vehicle networks in the presence of adversarial observation is examined, in the context of a canonical double-integrator-network (DIN) model. Specifically, we study the ability of a sentient adversary to estimate the full network’s state, from noisy local measurements of vehicle motions. Algebraic, spectral, and graphical characterizations are provided, which indicate the critical role of the inter-vehicle communication topology and control scheme in achieving security. 相似文献
98.
99.
荧光染料用于涤纶织物染色的荧光性能研究 总被引:4,自引:0,他引:4
在实验条件下,染色织物的荧光反射率随荧光染料的浓度增加而增加,超过一定浓度后,有下降趋势;在pH=5左右,荧光反射率最高;荧光增白剂会提高染色织物的荧光反射率,在荧光黄2GFL中,当荧光增白剂的浓度由0.1%增加到5%时,荧光反射率由8.43增加至18.59,而对非荧光染料只有增艳的作用,不产生荧光。荧光染料染色织物的荧光反射率随着加入非荧光染料量的增加而减弱。 相似文献
100.
Yu-Hang Yuan Xing-Gui Zhou Wei Wu Yi-Ran Zhang Wei-Kang Yuan Lingai Luo 《Catalysis Today》2005,105(3-4):544-2
Gas phase propylene epoxidation on gold catalysts has attracted wide attention from industry and academia due to its high selectivity. However, it suffers from low propylene conversion and rapid catalyst deactivation. Experiments showed that propylene conversion could be increased by raising H2, O2, or C3H6 concentration in the feed, but the feed compositions were within the explosion limit. It was also shown that the activity of the used catalyst could be fully recovered, but the regeneration temperature was 280 °C, much higher than that for reaction. Therefore a microchannel reactor was devised to suppress explosion and was constructed with Fecralloy, to raise the temperature rapidly for catalyst regeneration by electric heating. In two minutes the temperature of the reactor could be raised from 50 to 300 °C. Catalysts were coated on the alloy belt by dip coating, and the performance of the reactor was evaluated under different operating conditions. Results showed that in the microreactor the overall reaction rate was controlled mainly by the intrinsic reaction rate, and also influenced by film diffusion to a certain extent. The deactivated catalyst was regenerated in the microchannel reactor and the activity was fully recovered. 相似文献