全文获取类型
收费全文 | 246312篇 |
免费 | 29030篇 |
国内免费 | 26082篇 |
专业分类
电工技术 | 20875篇 |
技术理论 | 8篇 |
综合类 | 15285篇 |
化学工业 | 56703篇 |
金属工艺 | 10865篇 |
机械仪表 | 14171篇 |
建筑科学 | 9380篇 |
矿业工程 | 3206篇 |
能源动力 | 18872篇 |
轻工业 | 16988篇 |
水利工程 | 2535篇 |
石油天然气 | 5997篇 |
武器工业 | 2212篇 |
无线电 | 32688篇 |
一般工业技术 | 29256篇 |
冶金工业 | 6906篇 |
原子能技术 | 5246篇 |
自动化技术 | 50231篇 |
出版年
2024年 | 894篇 |
2023年 | 4182篇 |
2022年 | 7534篇 |
2021年 | 10141篇 |
2020年 | 8835篇 |
2019年 | 8109篇 |
2018年 | 7320篇 |
2017年 | 9610篇 |
2016年 | 10302篇 |
2015年 | 11535篇 |
2014年 | 12421篇 |
2013年 | 16522篇 |
2012年 | 17905篇 |
2011年 | 21267篇 |
2010年 | 15408篇 |
2009年 | 15029篇 |
2008年 | 15923篇 |
2007年 | 17381篇 |
2006年 | 16309篇 |
2005年 | 13907篇 |
2004年 | 11735篇 |
2003年 | 9391篇 |
2002年 | 7385篇 |
2001年 | 5722篇 |
2000年 | 4843篇 |
1999年 | 3957篇 |
1998年 | 3294篇 |
1997年 | 2672篇 |
1996年 | 2162篇 |
1995年 | 1770篇 |
1994年 | 1560篇 |
1993年 | 1175篇 |
1992年 | 1006篇 |
1991年 | 788篇 |
1990年 | 669篇 |
1989年 | 506篇 |
1988年 | 378篇 |
1987年 | 239篇 |
1986年 | 217篇 |
1985年 | 286篇 |
1984年 | 242篇 |
1983年 | 163篇 |
1982年 | 231篇 |
1981年 | 122篇 |
1980年 | 124篇 |
1979年 | 41篇 |
1978年 | 23篇 |
1977年 | 29篇 |
1959年 | 33篇 |
1951年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Modified Imidazoles: Degradation Inhibitors and Adhesion Promoters for Polyimide Films on Copper Substrates 总被引:1,自引:0,他引:1
Polyimide films on copper substrates that are exposed to elevated temperatures and an oxidizing environment will be subject to degradation. In order to halt this degradation without changing the properties of the system, a polymeric agent could be placed between the polyimide and the copper. This paper will investigate three such materials that will not only slow down the degradation of the polyimide and the oxidation of the copper, but will also improve adhesion within the system. Fourier transform infrared reflection-absorption spectroscopy (FTIR-RAS) will be used to investigate the polyimide/polymeric agent/copper system. 相似文献
932.
933.
A. Kussmaul S. Vernon P. C. Colter R. Sudharsanan A. Mastrovito K. J. Linden N. H. Karam N. H. Karam S. C. Warnick M. A. Dahleh 《Journal of Electronic Materials》1997,26(10):1145-1153
We have used spectroscopic ellipsometry to perform real-time monitoring during metalorganic chemical vapor deposition growth
of AlGaAs (on GaAs) and InGaAs (on GaAs and InP). Optical constants for these materials were obtained up to growth temperatures
of 600 to 700°C. This information permits real-time extraction of composition and layer thickness from the raw ellipsometric
data at sample rates on the order of 0.5 Hz. We describe closed-loop control of composition and total layer thickness on AlGaAs-based
structures, including Bragg reflectors. In-situ data obtained on double-heterostructure quantum-well laser structures demonstrate that spectroscopic ellipsometry is an extremely
powerful monitoring and quality-control tool, giving important real-time information on complex structures that would be difficult
and time-consuming to obtain after growth. 相似文献
934.
935.
多传感器检测是使用多种(或多个)传感器对同一被测对象进行广泛的测量。应用多传感器检测技术和多传感器数据溶合技术对车削加工中的零件外圆尺寸检测进行了实验研究,结果表明,多传感器检测技术能够满足现代检测技术对信息的精确要求,使得检测监控系统更加准确、可靠。 相似文献
936.
李毅 《核电子学与探测技术》1995,15(3):184-188
多丝正比室中电子的最大漂移时间是逃逸门电路中的一个重要参数。这个参数的选择将影响逃逸门工作方式的多丝正比室的整体性能。通过实验测量得到了多丝正比室中电子的最大漂移时间的实际值和最大漂移时间随多丝正比室工作状态的变化,测量结果在实际中得到应用。 相似文献
937.
The thermal stability of interfaces between metals (Ni, Pt, Ti, Mo) and III-V compound semiconductors has been investigated
by the application of Rutherford backscattering spectrometry. Metal diffusion and interfacial lattice disorder of the semiconductors
were analyzed for various metal/semiconductor samples annealed at temperatures up to 500°C. The interfaces of Ni/GaAs and
Ti/GaAs were found to be more stable than those of Ni/In-based semiconductors and Ti/ In-based semiconductors, respectively.
Faster diffusion of Pt atoms was ob-served in In-and As-containing materials than in P-containing materials. Mo/ semiconductor
interfaces were the most stable. 相似文献
938.
939.
Giuseppe G. G. Manzardo Sandra Kürsteiner-Laube und Daniel Perrin 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1996,203(6):501-506
In diethyl ether extracts from celeriac (Apium graveolens L. var.rapaceum) all four stereoisomers of (3a–7a)-cis-3-butylhexahydrophthalide were found to be present. The analyses were carried out by means of GC, enantioselective GC and GC-MS. The assignment of the relative configuration of the diastereomers3 and4 was accomplished by NOE difference spectroscopy. 相似文献
940.
The pyrolysis of tertiarybutylphosphine (TBP) has been studied in the low pressure conditions used for chemical beam epitaxy
(CBE). The pyrolysis studies were carried out in low pressure reactors of two different configurations, one of which is a
cracker cell designed for use in a CBE system. The reaction products were studied using a quadrupole mass spectrometer. The
products observed are accounted for by a reaction mechanism involving homolysis of the parent TBP molecule to produce PH2 and C4H9 radicals. These undergo subsequent reactions to form the stable products C4H8, PH3 and H2, with smaller amounts of P and P2 being produced. The production of the sub-hydride PH2 using this cracker cell design indicates that the use of partially cracked TBP may be a promising technique for reducing
the amount of carbon incorporated into the growing epitaxial layer. 相似文献