全文获取类型
收费全文 | 1739篇 |
免费 | 91篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 382篇 |
金属工艺 | 22篇 |
机械仪表 | 42篇 |
建筑科学 | 35篇 |
矿业工程 | 3篇 |
能源动力 | 47篇 |
轻工业 | 158篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 246篇 |
一般工业技术 | 369篇 |
冶金工业 | 357篇 |
原子能技术 | 8篇 |
自动化技术 | 137篇 |
出版年
2023年 | 11篇 |
2022年 | 23篇 |
2021年 | 40篇 |
2020年 | 16篇 |
2019年 | 30篇 |
2018年 | 40篇 |
2017年 | 36篇 |
2016年 | 39篇 |
2015年 | 29篇 |
2014年 | 52篇 |
2013年 | 80篇 |
2012年 | 81篇 |
2011年 | 129篇 |
2010年 | 80篇 |
2009年 | 66篇 |
2008年 | 85篇 |
2007年 | 79篇 |
2006年 | 66篇 |
2005年 | 43篇 |
2004年 | 41篇 |
2003年 | 54篇 |
2002年 | 49篇 |
2001年 | 34篇 |
2000年 | 46篇 |
1999年 | 42篇 |
1998年 | 117篇 |
1997年 | 80篇 |
1996年 | 58篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 19篇 |
1991年 | 6篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 20篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1975年 | 4篇 |
1974年 | 10篇 |
1972年 | 4篇 |
1967年 | 6篇 |
排序方式: 共有1838条查询结果,搜索用时 31 毫秒
81.
Low loss ferroelectric materials have been extensively investigated for the high frequency device applications. Especially, weak frequency dispersion materials with high dielectric permittivity and low loss tangent have enormous potential for electronic components including filters, and embedded capacitors. Ag(Ta0.5Nb0.5)O3 thick films have been prepared by low temperature sintering aid Li2CO3 (0, 1, 3 and 5 wt%). Ag(Ta0.5Nb0.5)O3 thick films were characterized by X-ray diffraction analysis and scanning electron microscopy. The dielectric and ferroelectric properties were also investigated. We observed very weak frequency dispersion of dielectric permittivity at the microwave frequency range. 相似文献
82.
ZnBO-doped (Ba, Sr)TiO3 ceramics were investigated for low-temperature co-fired ceramics (LTCCs) applications. Until now, B2O3 and Li2CO3 dopants have been commonly employed as the low-temperature sintering aids. In this paper, we suggest ZnBO as an alternative dopant to the B2O3 and Li2CO3. To reduce the sintering temperature of (Ba, Sr)TiO3, we have added 1–5 wt.% of ZnBO to (Ba, Sr)TiO3. ZnBO-doped (Ba, Sr)TiO3 ceramics were respectively sintered from 750 to 1350 °C by 50 °C to confirm the sintering temperature with different dopant contents. By adding 5 wt.% of ZnBO to the (Ba, Sr)TiO3 ceramics, the sintering temperature of (Ba, Sr)TiO3 ceramics can be reduced to 1100 °C. From the XRD analysis, ZnBO-doped (Ba, Sr)TiO3 has no pyro phase. By adding ZnBO dopants to (Ba, Sr)TiO3 ceramics, both of relative dielectric permittivity and loss tangent were decreased. From the frequency dispersion of dielectric properties, the relative dielectric permittivity and loss tangent of 5 wt.% ZnBO-doped (Ba, Sr)TiO3 were 1180 and 3.3 × 10−3, while those of BST were 1585 and 4.8 × 10−3, respectively. 相似文献
83.
A series of novel hexene‐1–propylene random copolymers with isotactic sequence of propylene was synthesized with a MgCl2‐supported Cr(acac)3 catalyst. The molecular weight distribution of copolymers and homopolymers was considerably narrower than that of typical polyolefins produced by heterogeneous Ziegler–Natta catalysts. The crystallizability of the copolymers having a propylene‐unit content of more than 50 mol % drastically decreased with decreasing propylene‐unit content, and the copolymers with a propylene content of less than 50 mol % were completely amorphous. In the present novel type of random copolymers with crystallizable and noncrystallizable units, a single glass transition was observed between pure polypropylene and polyhexene‐1, and a major component was found to govern the final morphology and the mechanical characteristics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2949–2954, 2004 相似文献
84.
With the recent growth in smartphone services, the “mobile” environment has become a key factor to consider in the design of the future Internet. In this paper, we propose Mobile‐Oriented Future Internet (MOFI), which is a new architecture for the future Internet for mobile‐oriented environments. The MOFI architecture is designed with three functional features: global identifier and local locator in the identifier‐locator separation, query‐first data delivery for route optimization, and distributed control of identifier‐locator mapping. The proposed architecture and functional operations are implemented and tested using the Linux platform. From the experiment results, we see that the MOFI architecture performs better than the existing identifier‐locator separation schemes, such as Proxy Mobile IP and Host Identity Protocol, in terms of data throughout, mapping control overhead, and handover delay. 相似文献
85.
Sea–island-type, black dope-dyed poly(ethylene terephthalate) microfibre fabrics were compared with normal sea–island-type PET microfibres in terms of their thermal properties, alkaline weight reduction, and dyeing properties. A comparison of the weight reduction behaviours of the two microfibre yarns revealed that the microfibre yarn containing carbon black exhibited a higher dissolution speed than that containing no carbon black. The incorporation of carbon black particles in the polyester fibre matrix therefore accelerates the degradation of the less crystalline sea component during alkali treatment. A cationic dye staining method was used to monitor the alkaline dissolution behaviour of the sea–island-type PET microfibres, and compared with the K/S values and the colour difference, the fk value is the most-desirable indicator for determination of the termination point of the alkaline dissolution process. The colour strength and the colour fastness of the dope-dyed sea–island-type PET microfibre fabrics are superior to those of the normal type. 相似文献
86.
M.M. Blideran M. Häffner B.-E. Schuster C. Raisch H. Weigand M. Fleischer H. Peisert T. Chassé D.P. Kern 《Microelectronic Engineering》2009,86(4-6):769-772
Fluorine plasma treatment is applied to cross-link a novolak based negative tone optical resist (maN-2400) to achieve increased dry etching selectivity. Furthermore, fluorine plasma treatment is used to strengthen the same resist to keep it in place during a second lithography step on top of the first one. Using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, cross-linking and passivation of the resist during plasma treatment is demonstrated. In contrast to the application of a baking process after resist development, AFM images show that fluorine plasma treatment preserves the intrinsic structure of the resist. 相似文献
87.
Koh Matsumoto Kazutada Ikenaga Jun Yamamoto Kazuki Naito Yoshiki Yano Akinori Ubukata Hiroki Tokunaga Tadanobu Arimura Katsuaki Cho Toshiya Tabuchi Akira Yamaguchi Yasuhiro Harada Yuzaburo Ban Kousuke Uchiyama 《半导体学报》2011,32(1):21-23
Growth rate has a direct impact on the productivity of nitride LED production.Atmospheric pressure growth of GaN with a growth rate as high as 10μm/h and also Al0.1Ga0.9N growth of 1μm/h by using 4 inch by 11 production scale MOVPE are described.XRD of(002) and(102) direction was 200 arcsec and 250 arcsec, respectively.Impact of the growth rate on productivity is discussed. 相似文献
88.
It is widely feared that a novel, highly pathogenic, human transmissible influenza virus may evolve that could cause the next global pandemic. Mitigating the spread of such an influenza pandemic would require not only the timely administration of antiviral drugs to those infected, but also the implementation of suitable intervention policies for stunting the spread of the virus. Towards this end, mathematical modelling and simulation studies are crucial as they allow us to evaluate the predicted effectiveness of the various intervention policies before enforcing them. Diagnosis plays a vital role in the overall pandemic management framework by detecting and distinguishing the pathogenic strain from the less threatening seasonal strains and other influenza-like illnesses. This allows treatment and intervention to be deployed effectively, given limited antiviral supplies and other resources. However, the time required to design a fast and accurate testkit for novel strains may limit the role of diagnosis. Herein, we aim to investigate the cost and effectiveness of different diagnostic methods using a stochastic agent-based city-scale model, and then address the issue of whether conventional testing approaches, when used with appropriate intervention policies, can be as effective as fast testkits in containing a pandemic outbreak. We found that for mitigation purposes, fast and accurate testkits are not necessary as long as sufficient medication is given, and are generally recommended only when used with extensive contact tracing and prophylaxis. Additionally, in the event of insufficient medication and fast testkits, the use of slower, conventional testkits together with proper isolation policies while waiting for the diagnostic results can be an equally effective substitute. 相似文献
89.
Joachim Mittendorf Prof. Dr. Stefan Weigand Dr. Cristina Alonso‐Alija Dr. Erwin Bischoff Dr. Achim Feurer Dr. Michael Gerisch Dr. Armin Kern Dr. Andreas Knorr Dr. Dieter Lang Dr. Klaus Muenter Dr. Martin Radtke Dr. Hartmut Schirok Dr. Karl‐Heinz Schlemmer Dr. Elke Stahl Dr. Alexander Straub Dr. Frank Wunder Dr. Johannes‐Peter Stasch Dr. 《ChemMedChem》2009,4(5):693-693
90.