全文获取类型
收费全文 | 81256篇 |
免费 | 9120篇 |
国内免费 | 5618篇 |
专业分类
电工技术 | 6793篇 |
技术理论 | 2篇 |
综合类 | 7498篇 |
化学工业 | 11192篇 |
金属工艺 | 4898篇 |
机械仪表 | 5396篇 |
建筑科学 | 6400篇 |
矿业工程 | 2793篇 |
能源动力 | 2139篇 |
轻工业 | 8716篇 |
水利工程 | 2235篇 |
石油天然气 | 2943篇 |
武器工业 | 998篇 |
无线电 | 9147篇 |
一般工业技术 | 7645篇 |
冶金工业 | 3325篇 |
原子能技术 | 1319篇 |
自动化技术 | 12555篇 |
出版年
2024年 | 526篇 |
2023年 | 1505篇 |
2022年 | 3210篇 |
2021年 | 4183篇 |
2020年 | 3131篇 |
2019年 | 2323篇 |
2018年 | 2542篇 |
2017年 | 2927篇 |
2016年 | 2547篇 |
2015年 | 3774篇 |
2014年 | 4859篇 |
2013年 | 5571篇 |
2012年 | 6591篇 |
2011年 | 6774篇 |
2010年 | 6477篇 |
2009年 | 5922篇 |
2008年 | 5809篇 |
2007年 | 5644篇 |
2006年 | 4794篇 |
2005年 | 3978篇 |
2004年 | 2826篇 |
2003年 | 1981篇 |
2002年 | 1860篇 |
2001年 | 1547篇 |
2000年 | 1379篇 |
1999年 | 889篇 |
1998年 | 436篇 |
1997年 | 398篇 |
1996年 | 351篇 |
1995年 | 280篇 |
1994年 | 203篇 |
1993年 | 173篇 |
1992年 | 118篇 |
1991年 | 98篇 |
1990年 | 61篇 |
1989年 | 75篇 |
1988年 | 51篇 |
1987年 | 27篇 |
1986年 | 25篇 |
1985年 | 10篇 |
1984年 | 18篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 21篇 |
1980年 | 24篇 |
1979年 | 10篇 |
1970年 | 2篇 |
1965年 | 2篇 |
1959年 | 9篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
织物-树脂复合材料层压板的准静态侵彻机理 总被引:4,自引:1,他引:3
本文利用MTS得到了芳纶和高强维纶织物复合材料层压板受尖头侵彻体穿孔的准静态侵彻曲线 ,比较和分析了不同类型纤维集合体与热固性树脂和热塑性树脂复合材料的破坏模式 ,并考察了芳纶织物复合材料层压板侵彻的逐步破坏过程 ,揭示了复合材料层压板的准静态侵彻机理。 相似文献
42.
应用色谱—质谱(GC-MS)及裂解色谱-质谱(PGC-MS)测定了乙烯基三甲基硅烷等离子体聚合反应中的气体冷凝物及聚合物,研究推导了等离子体聚合反应历程。单体在气相中被电子撞击,然后扩散到基底,在基底发生链增长和链终止反应。 相似文献
43.
This paper reports a new, highly integrated modular design approach for pulsewidth-modulation AC-AC converters based on a modular phase-bank structure. Novel high-power 3-in-1 integrated bi-directional power modules (IBPM) rated at 1200-V AC and 150 A and the 3-to-1 phase bank circuits have been successfully developed, fabricated and tested. This enables the modularity design of the multiphase converter systems and reduces the critical parasitic inductance. A theoretical analysis of the IBPM's silicon utilization for this new breed of direct power converters has been outlined. A lab prototype at medium power level has been successfully designed, implemented, and tested with good results. A nearly 460-VRMS out voltage at a 1:0.955 voltage transfer ratio, which, perhaps, is the highest performance reported so far in the literature, has been achieved by the novel two-side modulation control system. The converter-fed AC motor system is able to operate over the 0-240 Hz range with inherent regenerative capability and four-quadrant operation. Potential industrial applications are also briefly highlighted in this paper 相似文献
44.
ATHISAYA BURANSOMPOB JUMING TANG RUNSHENG MAO BARRY G. SWANSON 《Journal of Food Processing and Preservation》2003,27(6):445-464
Short time heat treatments effectively control insect contamination of nuts containing substantial quantities of polyunsaturated fatty acids susceptible to oxidative rancidity. Walnut kernels contain greater concentrations of polyunsaturated fatty acids than almond kernels. The objectives of this research were to investigate the lipid stability of shelled walnuts and almonds as affected by short time heat treatments and accelerated storage temperatures. Heating treatments were at 55C for 2 min, 55C for 10 min, 60C for 2 min or 60C for 10 min to simulate predetermined deinfestation treatments. Untreated control and heat treated shelled walnut and almond kernels were stored at 25C for 5, 15, 30 and 60 days or 35C for 2, 5, 10 and 20 days to simulate the shelf lives of walnut and almond kernels at 4C for 2 years. Oils extracted from untreated and short time heat treated walnut kernels exhibited higher peroxide values than oils extracted from untreated and short time heat treated almond kernels under equivalent conditions. Oils extracted from untreated walnut kernels exhibited significantly (P ± 0.05) higher peroxide values than oils extracted from short time heat treated walnut kernels after 5, 15, 30, and 60 days of storage at 25C, or after 2, 5, 10, or 20 days of storage at 35C. Oils extracted from untreated almond kernels exhibited higher peroxide values than oils extracted from short time heat treated almond kernels after 5, 15, 30, or 60 days of storage at 25C, or after 2, 5, 10 or 20 days of storage at 35C. Oils extracted from untreated walnut kernels and oils extracted from short time heat treated walnut kernels exhibited higher peroxide values than oils extracted from almond kernels after storage at 25C or 35C. Short time heat treatment does not enhance development of rancidity during accelerated storage of walnut or almond kernels. 相似文献
45.
2,6-二甲基萘生产技术进展 总被引:2,自引:0,他引:2
许杰 《精细石油化工进展》2003,4(2):44-47
概述了国外2,6-二甲基萘生产技术现状,详细介绍了ExxonMobil公司2,6-二甲基萘的工艺路线和日本神户制钢所的提纯方法,指出了实现我国2,6-二甲基萘工业化生产应注意的问题。 相似文献
46.
Ziegler-Natta烯烃聚合催化剂进展 总被引:1,自引:0,他引:1
综述了Ziegler-Natta催化剂在乙烯聚合和丙烯聚合方面的研究开发现状,重点介绍了采用新型二醚化合物作为内给电子体的丙烯聚合催化剂的进展。随着合成树脂向功能化方向发展,开发综合性能优越的新型催化剂及给电子体将是今后的研究方向。 相似文献
47.
用共沉淀法制备了TiO2-ZrO2复合氧化物载体,BET,DTA,XRD表征结果表明,该复合载体具有较大的比表面和较好的热稳定性,对于环己酮肟气相Beckmann重排反应制己内酰胺,用复合载体制备的B2O3/TiO2-ZrO2催化剂,比分别以TiO2,ZrO2为载体所制备的B2O3/TiO2和B2O3/ZrO2催化剂具有更高的活性和选择性,实验表明,催化剂表面中等强度的酸位是环己酮肟气相Beckmann重排反应的有效活性中心。 相似文献
48.
Szczech J.B. Megaridis C.M. Gamota D.R. Jie Zhang 《Electronics Packaging Manufacturing, IEEE Transactions on》2002,25(1):26-33
An emerging selective metallization process to fabricate fine-line conductors based on drop-on-demand (DOD) ink jet printing and novel nano-particle fluid suspensions (NPFS) was studied. The suspensions consist of 1-10 nm silver or gold particulates that are homogeneously suspended in an organic carrier. A piezo-electric droplet generator driven by a bipolar voltage signal is used to dispense 50-70 μm diameter droplets traveling at 1-3 m/s before impacting a compliant polyimide substrate. The deposit/substrate composite is subsequently processed at 300°C for 15 min to allow for complete evaporation of the carrier and for sintering of the nano-particles, thereby yielding a finished circuit interconnect. Test vehicles created using this technique exhibit features as fine as 120 μm wide and 1 μm thick with resistivities on the order of 3.5×10-5 Ωcm. The circuitry performed well under environmental conditioning. As expected, repeatability of circuitry fabrication showed sensitivity to the generation of steady, satellite-free droplets. In an effort to generate droplets consistently, it is essential to develop a strong fundamental understanding of the correlation between device excitation parameters and dispensed fluid properties, and to resolve the microrheological behavior of the NPFS when flowing through the droplet generator 相似文献
49.
Internet网络延时分析 总被引:3,自引:0,他引:3
本文对Internet网络延迟进行了较为全面的分析,介绍了几种减少网络延迟的技术。然后提出一种新的方法,并用排队论加以分析。 相似文献
50.
Meng Jun min Ocean University of Qingdao Qingdao China Zhang Zi li Zhao Jun sheng First Institute of Oceanography State Oceanic Administration Qingdao China Zhang Jie Key Laboratory of Marine Science Numerical Modelling 《水动力学研究与进展(B辑)》2001,(3)
1 . INTRODUCTIONOceaninternalwaveisakindofgravitywavegeneratedinthestratifiedocean .Itproducebytheinteractionoftidecurrentandtopography ,seaquakeandmovingshipwhenthestrong ,shallowpycnoclineis present.Theinternalwavesinthecontinentalshelfarealmosttideprod… 相似文献