全文获取类型
收费全文 | 169835篇 |
免费 | 14363篇 |
国内免费 | 8194篇 |
专业分类
电工技术 | 11043篇 |
技术理论 | 15篇 |
综合类 | 11387篇 |
化学工业 | 26311篇 |
金属工艺 | 9418篇 |
机械仪表 | 11012篇 |
建筑科学 | 13265篇 |
矿业工程 | 4960篇 |
能源动力 | 4870篇 |
轻工业 | 11180篇 |
水利工程 | 3492篇 |
石油天然气 | 9066篇 |
武器工业 | 1489篇 |
无线电 | 21096篇 |
一般工业技术 | 19523篇 |
冶金工业 | 8111篇 |
原子能技术 | 2061篇 |
自动化技术 | 24093篇 |
出版年
2024年 | 733篇 |
2023年 | 2659篇 |
2022年 | 4790篇 |
2021年 | 6632篇 |
2020年 | 5019篇 |
2019年 | 4099篇 |
2018年 | 4770篇 |
2017年 | 5382篇 |
2016年 | 4766篇 |
2015年 | 6630篇 |
2014年 | 8320篇 |
2013年 | 10248篇 |
2012年 | 11260篇 |
2011年 | 12318篇 |
2010年 | 10857篇 |
2009年 | 10428篇 |
2008年 | 10605篇 |
2007年 | 10010篇 |
2006年 | 9703篇 |
2005年 | 8312篇 |
2004年 | 5714篇 |
2003年 | 4627篇 |
2002年 | 4156篇 |
2001年 | 3872篇 |
2000年 | 3792篇 |
1999年 | 4026篇 |
1998年 | 3285篇 |
1997年 | 2841篇 |
1996年 | 2531篇 |
1995年 | 2157篇 |
1994年 | 1724篇 |
1993年 | 1331篇 |
1992年 | 1059篇 |
1991年 | 795篇 |
1990年 | 644篇 |
1989年 | 529篇 |
1988年 | 415篇 |
1987年 | 314篇 |
1986年 | 216篇 |
1985年 | 183篇 |
1984年 | 111篇 |
1983年 | 84篇 |
1982年 | 91篇 |
1981年 | 64篇 |
1980年 | 62篇 |
1979年 | 42篇 |
1978年 | 25篇 |
1977年 | 26篇 |
1976年 | 40篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
介绍了15kt/a本体苯乙烯-丙烯腈(SAN)装置试生产打火机专用SAN树脂的生产情况,确定了主要工艺配方及参数:进料组成为乙苯浓度为6%-11%、丙烯腈浓度为30%-42%,聚合温度130-145℃、压力0.40-0.46MPa,搅拌转速60-90r/min,脱挥温度215-250℃、压力小于等于4kPa;并对影响打火机志用SAN树脂性能的主要工艺条件及因素进行了讨论。结果表明,聚合温度、结合丙烯腈含量、熔体流动指数、转化率是影响打火机专用SAN树脂生产工艺及产品性能的主要因素。 相似文献
93.
94.
Behavioral cues to deception are instrumental in detecting deception. As one of the primary sources of deception behavior, text has been analyzed at the level of sub-sentence or message but not the discourse of interaction. Additionally, empirical studies on cues to deception in the case of multiple receivers remain nonexistent. To fill these voids, we propose a discourse framework and six hypotheses about deception behaviors in a multi-receiver environment. The deception behaviors are operationalized by discourse features based on an analysis of real-world data. The results of statistical analysis validate the efficacy of discourse features in discriminating deceivers from truth-tellers. 相似文献
95.
Partially observable Markov decision process (POMDP) is an ideal framework for sequential decision-making under uncertainty in stochastic domains. However, it is notoriously computationally intractable to solving POMDP in real-time system. In order to address this problem, this paper proposes a point-based online value iteration (PBOVI) algorithm which involves performing value backup at specific reachable belief points, rather than over the entire belief simplex, to speed up computation processes, exploits branch-and-bound pruning approach to prune the AND/OR tree of belief states online, and proposes a novel idea to reuse the belief states that have been searched to avoid repeated computation. The experiment and simulation results show that the proposed algorithm can simultaneously satisfy the requirement of low errors and high timeliness in real-time system. 相似文献
96.
Chang Yang Chengyin Liu Ning Wu Xiang Wu Yidong Li Zhiying Wang 《Neural computing & applications》2014,25(7-8):1741-1754
Collaboration representation-based classification (CRC) was proposed as an alternative approach to the sparse representation method with similar efficiency. The CRC is essentially a competition scheme for the training samples to compete with each other in representing the test sample, and the training class with the minimum representation residual from the test sample wins the competition in the classification. However, the representation error is usually calculated based on the Euclidean distance between a test sample and the weighted sum of all the same-class samples. This paper exploits alternative methods of calculating the representation error in the CRC methods to reduce the representation residual in a more optimal way, so that the sample classes compete with each other in a closer range to represent the test sample. A large number of face recognition experiments on three face image databases show that the CRC methods with optimized presentation residual achieve better performance than the original CRC, and the maximum improvement in classification accuracy is up to 12 %. 相似文献
97.
ATO包裹硅酸锆的制备与应用 总被引:2,自引:0,他引:2
采用化学共沉淀技术制备了锑掺杂二氧化锡(ATO)包裹硅酸锆的导电粉体,对比了该导电粉体与ATO在防静电陶瓷中的应用效果。结果表明与掺纯ATO相比较,掺入ATO包裹硅酸锆的防静电陶瓷颜色比较浅,并且能明显减少氧化锡的用量,当陶瓷的表面电阻为107Ω/□量级时,用ATO包裹硅酸锆作为导电填料可以节省25%左右的ATO。 相似文献
98.
99.
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