全文获取类型
收费全文 | 264912篇 |
免费 | 29047篇 |
国内免费 | 18908篇 |
专业分类
电工技术 | 22799篇 |
技术理论 | 4篇 |
综合类 | 24741篇 |
化学工业 | 34694篇 |
金属工艺 | 17048篇 |
机械仪表 | 18593篇 |
建筑科学 | 22232篇 |
矿业工程 | 9458篇 |
能源动力 | 7628篇 |
轻工业 | 23656篇 |
水利工程 | 7447篇 |
石油天然气 | 11244篇 |
武器工业 | 3367篇 |
无线电 | 31126篇 |
一般工业技术 | 25080篇 |
冶金工业 | 10417篇 |
原子能技术 | 3678篇 |
自动化技术 | 39655篇 |
出版年
2024年 | 1506篇 |
2023年 | 4285篇 |
2022年 | 9296篇 |
2021年 | 12424篇 |
2020年 | 9145篇 |
2019年 | 6810篇 |
2018年 | 7498篇 |
2017年 | 8881篇 |
2016年 | 7678篇 |
2015年 | 11847篇 |
2014年 | 14940篇 |
2013年 | 17789篇 |
2012年 | 21309篇 |
2011年 | 21704篇 |
2010年 | 20610篇 |
2009年 | 19616篇 |
2008年 | 19921篇 |
2007年 | 19289篇 |
2006年 | 17072篇 |
2005年 | 13752篇 |
2004年 | 9622篇 |
2003年 | 7269篇 |
2002年 | 6915篇 |
2001年 | 6100篇 |
2000年 | 4883篇 |
1999年 | 3136篇 |
1998年 | 1762篇 |
1997年 | 1452篇 |
1996年 | 1314篇 |
1995年 | 1126篇 |
1994年 | 912篇 |
1993年 | 590篇 |
1992年 | 495篇 |
1991年 | 355篇 |
1990年 | 316篇 |
1989年 | 278篇 |
1988年 | 179篇 |
1987年 | 147篇 |
1986年 | 120篇 |
1985年 | 54篇 |
1984年 | 54篇 |
1983年 | 45篇 |
1982年 | 34篇 |
1981年 | 60篇 |
1980年 | 63篇 |
1979年 | 40篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1959年 | 31篇 |
1951年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The formation of aluminum matrix composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system was investigated. The thermal analysis results show that the reactions are spontaneous and exothermic. The Gibbs free energy of α-Al2O3 is the lowest among all the combustion products, followed by TiB2 and Al3Ti. It is noted that when the B2O3/TiO2 mole ratio is below 1, the reaction products are composed of particle-like α-Al2O3, TiB2 and rod-like Al3Ti. The α-Al2O3 crystallites, resulting from the reaction between A1 and TiO2 or B2O3, are segregated at the grain boundaries due to a lower wettability with the matrix. SEM micrographs show that rod-like Al3Ti phase distributes uniformly in the matrix. When the BEO3/TiO2 mole ratio is around 1, the Al3Ti phase almost disappears in the composites, and the distribution of α-Al2O3 particulates is improved evidently. 相似文献
92.
Junwei Fu Zhengbiao Zhang Zhenping Cheng Jian Zhu Wei Zhang Xiulin Zhu 《Polymer Bulletin》2008,61(3):287-297
A novel reversible addition-fragmentation chain transfer (RAFT) reagent bearing triphenylamine (TPA)
group, 4-diphenylamino-dithiobenzoic acid benzyl ester (DDABE), was designed and synthesized. It was used
in the RAFT polymerizations of styrene (St) and methyl acrylate (MA) to prepare end-functionalized polymers.
The results of the polymerization showed that the RAFT polymerizations could be well controlled using DDABE
as the RAFT agent. Number-average molecular weight (Mn,GPC) increased linearly
with monomer conversion, and molecular weight distributions were relatively narrow (PDI<
1.50). The results of chain-extension reaction, 1H NMR spectra and UV/Vis
spectra confirmed that most of the polymers chains were end-capped by the functional triphenylamine
(TPA) groups. The effect of feed molar ratios of St/DDABE/AIBN on polymerization was investigated. 相似文献
93.
本文介绍了磁电机点火系统的点火提前角测量原理。对点火系统的点火信号和触发信号进行采集、调理,再用单片机进行处理,最后用LabVIEW进行点火提前角数据存储和显示。 相似文献
94.
本文分析了QC小组活动与企业文化的特点与共同点,提出开展QC小组活动与企业文化建设是互相促进,互相补充的,两者可以互相结合。 相似文献
95.
介绍了一个计算机远程控制系统的设计与实现,该系统采用客户机/服务器模式,实现远程屏幕的实时传输,采用LZW压缩算法对图像进行压缩传输,在接受方进行解码并且实现了远程文件创建和删除、显示被控制端的主机信息、发送实时消息等功能。采用鼠标,键盘的模拟方式对计算机进行实时控制。 相似文献
96.
This paper presents an investigation on a single-mode-multimode-single-mode fiber structure. A one-way guided-mode propagation analysis for the circular symmetry waveguide is employed to model the light propagation and the approximated formulations are derived and evaluated concerning the accuracy. Phase conjunction of the multimode interference within the fiber structure is revealed. A simple way to predict and analyze the spectral response of the structure is presented through the space to wavelength mapping with the derived approximated formulations. The prediction of spectral response is verified numerically and experimentally. 相似文献
97.
The ennoblement of corrosion potential (Ecorr) of passive metal immersed in seawater was investigated with electrochemical technology and epifluorescence microscopy. The in situ observation showed that the bacteria number increased on the metal surface according to an exponential law which was in the same way with the ennoblement of Ecorr. At the same time, the anodic polarization current of high‐Mo stainless steel decreased in the initial days. According to the mix‐potential theory and the characteristics of polarization curves of high‐Mo steel in natural seawater, the ennoblement of corrosion potential may be induced by the decrease of the passive current density. 相似文献
98.
99.
Wei Li Zhang Wei Pan Bin Luo Xi Hua Zou Meng Yao Wang 《Photonics Technology Letters, IEEE》2008,20(9):712-714
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications. 相似文献
100.