全文获取类型
收费全文 | 16090篇 |
免费 | 1884篇 |
国内免费 | 1270篇 |
专业分类
电工技术 | 1603篇 |
综合类 | 1806篇 |
化学工业 | 1812篇 |
金属工艺 | 885篇 |
机械仪表 | 1221篇 |
建筑科学 | 1082篇 |
矿业工程 | 527篇 |
能源动力 | 448篇 |
轻工业 | 1694篇 |
水利工程 | 403篇 |
石油天然气 | 427篇 |
武器工业 | 256篇 |
无线电 | 1649篇 |
一般工业技术 | 1199篇 |
冶金工业 | 1693篇 |
原子能技术 | 287篇 |
自动化技术 | 2252篇 |
出版年
2024年 | 94篇 |
2023年 | 277篇 |
2022年 | 596篇 |
2021年 | 771篇 |
2020年 | 556篇 |
2019年 | 402篇 |
2018年 | 414篇 |
2017年 | 483篇 |
2016年 | 412篇 |
2015年 | 705篇 |
2014年 | 828篇 |
2013年 | 992篇 |
2012年 | 1275篇 |
2011年 | 1278篇 |
2010年 | 1263篇 |
2009年 | 1173篇 |
2008年 | 1197篇 |
2007年 | 1175篇 |
2006年 | 985篇 |
2005年 | 865篇 |
2004年 | 598篇 |
2003年 | 405篇 |
2002年 | 379篇 |
2001年 | 349篇 |
2000年 | 301篇 |
1999年 | 124篇 |
1998年 | 387篇 |
1997年 | 212篇 |
1996年 | 156篇 |
1995年 | 96篇 |
1994年 | 80篇 |
1993年 | 87篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 14篇 |
1978年 | 4篇 |
1977年 | 36篇 |
1976年 | 90篇 |
1959年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Zhenkun Ke Xin Cao Chuanli Shan Lifen Shi Pingping Wang Yong Yang Fengyang Zhao Jiedong Cui Jinwei Li Gang Zhou Min Guan Tao Yu 《Ceramics International》2021,47(14):19605-19613
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased. 相似文献
2.
3.
实施独立计量分区(district metered area,DMA)是辅助供水管网管理和漏损识别的重要手段.图划分算法是进行DMA分区的方法之一,常规图划分算法应用中,存在解空间受限、分区后原水流状态易发生较大改变、形成较多串联分区(对流量计算不利)的缺点.在常规图划分算法基础上进行了改进:粗化阶段按照特定规则匹配、合并非输水干管两端的节点,形成简化的管网拓扑结构;分区阶段得到管网初步分区方案;细化阶段提出基于贪心算法、枚举算法、蒙特卡洛算法的分区调整方法,结合改进的仪表安置方法、水力模拟、优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS),对分区方案进行调整.将该方法应用于YX市供水管网,成功进行了分区. 相似文献
4.
5.
6.
CMP系统技术与市场 总被引:3,自引:1,他引:2
葛劢冲 《电子工业专用设备》2003,32(1):17-24
概述了CMP系统技术的发展历史、发展趋势以及在IC生产中的重要性,介绍了国外CMP设备主要制造厂家的设备型号和性能及CMP设备市场分布和需求,阐述了CMP系统技术的基础研究、关键技术和国内研究概况。 相似文献
7.
KJ Shon M Grilley R Jacobsen GE Cartier C Hopkins WR Gray M Watkins DR Hillyard J Rivier J Torres D Yoshikami BM Olivera 《Canadian Metallurgical Quarterly》1997,36(31):9581-9587
A paralytic peptide, psi-conotoxin Piiie has been purified and characterized from Conus purpurascens venom. Electrophysiological studies indicate that the peptide inhibits the nicotinic acetylcholine receptor (nAChR). However, the peptide does not block the binding of alpha-bungarotoxin, a competitive nAChR antagonist. Thus, psi-conotoxin Piiie appears to inhibit the receptor at a site other than the acetylcholine-binding site. As ascertained by sequence analysis, mass spectrometry, and chemical synthesis, the peptide has the following covalent structure: HOOCCLYGKCRRYOGCSSASCCQR* (O = 4-trans hydroxyproline; * indicates an amidated C-terminus). The disulfide connectivity of the toxin is unrelated to the alpha- or the alphaA-conotoxins, the Conus peptide families that are competitive inhibitors of the nAChR, but shows homology to the mu-conotoxins (which are Na+ channel blockers). 相似文献
8.
9.
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
10.
EG Mdurvwa JI Alak GE Pimentel-Smith HS Gakou S Kolavala H Abdelrahman PG Reddy 《Canadian Metallurgical Quarterly》1997,43(7):1039-1044
The LP-BM5 murine leukemia virus causes acquired immunodeficiency syndrome in C57BL/6J mice (MAIDS), similar to that of AIDS in humans. The objective of this study was to determine the effect of LP-BM5 viral infection on cellular activation and membrane integrity of splenocytes. Oxidative burst in splenocytes in response to exposure to PMA (20 microg/ml) was significantly higher (p<.02) in infected than in control mice at two weeks post-infection using luminol-enhanced chemiluminescence. By 13 weeks post-infection superoxide anion production in infected mice was significantly lower when compared to controls coinciding with decreased proliferative response to mitogens. The extent of cell membrane damage as indicated by lactic dehydrogenase (LDH) activity in serum was significantly higher in infected than in control mice (p<.001). The results from this study suggests that LP-BM5 virus causes an initial stimulation of cellular activity followed by a decreased cell activation characterized by decreased proliferation of splenocytes and decreased oxygen radical production. Decreased cell membrane integrity indicated by increased LDH activity may partly be responsible for these changes. 相似文献