全文获取类型
收费全文 | 72444篇 |
免费 | 5474篇 |
国内免费 | 2192篇 |
专业分类
电工技术 | 3152篇 |
技术理论 | 7篇 |
综合类 | 3244篇 |
化学工业 | 13456篇 |
金属工艺 | 3792篇 |
机械仪表 | 4534篇 |
建筑科学 | 3982篇 |
矿业工程 | 1600篇 |
能源动力 | 2387篇 |
轻工业 | 4927篇 |
水利工程 | 882篇 |
石油天然气 | 3186篇 |
武器工业 | 463篇 |
无线电 | 9546篇 |
一般工业技术 | 11130篇 |
冶金工业 | 4077篇 |
原子能技术 | 998篇 |
自动化技术 | 8747篇 |
出版年
2024年 | 279篇 |
2023年 | 1166篇 |
2022年 | 1930篇 |
2021年 | 2842篇 |
2020年 | 2126篇 |
2019年 | 1895篇 |
2018年 | 2264篇 |
2017年 | 2474篇 |
2016年 | 2406篇 |
2015年 | 2663篇 |
2014年 | 3615篇 |
2013年 | 4580篇 |
2012年 | 4765篇 |
2011年 | 5376篇 |
2010年 | 4324篇 |
2009年 | 4217篇 |
2008年 | 4086篇 |
2007年 | 3662篇 |
2006年 | 3436篇 |
2005年 | 2941篇 |
2004年 | 2206篇 |
2003年 | 1942篇 |
2002年 | 1925篇 |
2001年 | 1676篇 |
2000年 | 1610篇 |
1999年 | 1600篇 |
1998年 | 1675篇 |
1997年 | 1240篇 |
1996年 | 1157篇 |
1995年 | 836篇 |
1994年 | 660篇 |
1993年 | 478篇 |
1992年 | 378篇 |
1991年 | 299篇 |
1990年 | 246篇 |
1989年 | 221篇 |
1988年 | 184篇 |
1987年 | 123篇 |
1986年 | 113篇 |
1985年 | 79篇 |
1984年 | 65篇 |
1983年 | 55篇 |
1982年 | 58篇 |
1981年 | 39篇 |
1980年 | 38篇 |
1979年 | 19篇 |
1977年 | 26篇 |
1976年 | 39篇 |
1975年 | 17篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
概述污水处理厂的一般工艺,简单介绍了风机、水泵等的节能特点,介绍了变频调速装置在污水处理厂各处理工段的应用。 相似文献
102.
Jae-Duk Lee Jeong-Hyuk Choi Donggun Park Kinam Kim 《Electron Device Letters, IEEE》2003,24(12):748-750
In contrast to the conventional theories, we have revealed that the most distinguished mechanism in the data retention phenomenon after Fowler-Nordheim (FN) stress in sub-100 nm NAND Flash memory cells is the annihilation of interface states. Interface state generation rate increases rapidly as the channel width of NAND flash cell decreases. Comparison of interface states and stress-induced leakage current (SILC) component during retention mode shows that the annihilation of interface states strongly affects data retention characteristics of the programmed cells. 相似文献
103.
104.
Min-Seok Park Vladislav P. Vislovskiy Jong-San Chang Yong-Gun Shul Jin S. Yoo Sang-Eon Park 《Catalysis Today》2003,87(1-4):205-212
Alumina-supported vanadium oxide, VOx/Al2O3, and binary vanadium–antimony oxides, VSbOx/Al2O3, have been tested in the ethylbenzene dehydrogenation with carbon dioxide and characterized by SBET, X-ray diffraction, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction and CO2 pulse methods. VSbOx/Al2O3 exhibited enhanced catalytic activity and especially on-stream stability compared to VOx/Al2O3 catalyst. Incorporation of antimony into VOx/Al2O3 increased dispersion of active VOx species, enhanced redox properties of the systems and formed a new mixed vanadium–antimony oxide phase in the most catalytically efficient V0.43Sb0.57Ox/Al2O3 system. 相似文献
105.
A new discontinuous modulation method based on space-vector control is proposed and analyzed. The proposed technique employs a pulse-dropping method and is designed in the time domain. It features a very wide modulation range while maintaining the required waveform qualities and switching numbers in the overmodulation region. Since the modulation method and modulation index equation are simple, the proposed technique can be easily implemented by software and is applicable to the overmodulation region in ac motor drives. The performance indexes are discussed and experiments have been performed. 相似文献
106.
Yan R.-H. Lee K.F. Jeon D.Y. Kim Y.O. Park B.G. Pinto M.R. Rafferty C.S. Tennant D.M. Westerwick E.H. Chin G.M. Morris M.D. Early K. Mulgrew P. Mansfield W.M. Watts R.K. Voshchenkov A.M. Bokor J. Swartz R.G. Ourmazd A. 《Electron Device Letters, IEEE》1992,13(5):256-258
The authors report the implementation of deep-submicrometer Si MOSFETs that at room temperature have a unity-current-gain cutoff frequency (f T) of 89 GHz, for a drain-to-source bias of 1.5 V, a gate-to-source bias of 1 V, a gate oxide thickness of 40 Å, and a channel length of 0.15 μm. The fabrication procedure is mostly conventional, except for the e-beam defined gates. The speed performance is achieved through an intrinsic transit time of only 1.8 ps across the active device region 相似文献
107.
Sang-Hoon Lee Dae Hwan Kim Kyung Rok Kim Jong Duk Lee Byung-Gook Park Young-Jin Gu Gi-Young Yang Jeong-Taek Kong 《Nanotechnology, IEEE Transactions on》2002,1(4):226-232
A practical model for a single-electron transistor (SET) was developed based on the physical phenomena in realistic Si SETs, and implemented into a conventional circuit simulator. In the proposed model, the SET current calculated by the analytic model is combined with the parasitic MOSFET characteristics, which have been observed in many recently reported SETs formed on Si nanostructures. The SPICE simulation results were compared with the measured characteristics of the Si SETs. In terms of the bias, temperature, and size dependence of the realistic SET characteristics, an extensive comparison leads to good agreement within a reasonable level of accuracy. This result is noticeable in that a single set of model parameters was used, while considering divergent physical phenomena such as the parasitic MOSFET, the Coulomb oscillation phase shift, and the tunneling resistance modulated by the gate bias. When compared to the measured data, the accuracy of the voltage transfer characteristics of a single-electron inverter obtained from the SPICE simulation was within 15%. This new SPICE model can be applied to estimating the realistic performance of a CMOS/SET hybrid circuit or various SET logic architectures. 相似文献
108.
109.
陈如燕 《辐射研究与辐射工艺学报》1992,10(4):223-227
研究了工业糖化酶制剂经辐照处理后各项性能的变化。结果表明,经2kGy以下剂量的γ射线处理后,可提高其贮存稳定性,改善卫生品质,不影响其正常使用。 相似文献
110.
应用不同剂量的~(60)Coγ射线照射含NT株弓形虫包囊的鼠脑匀浆后,以0.4%胰蛋白酶液消化,使弓形虫缓殖子从包囊中释放出来,并用生理盐水作连续10倍稀释,使成为含不同数量缓殖子的悬液,将此悬液接种小鼠,用生物检测方法确定其感染性。另设未经照射处理的缓殖子悬液感染小鼠的对照组。结果表明,γ射线0.55kGy剂量为控制鼠脑中NT株弓形虫感染性的最小有效剂量。γ射线0.1kGy剂量对弓形虫缓殖子感染性无明显影响,而0.45kGy照射后,其感染性较前者下降了10~4倍。 相似文献