全文获取类型
收费全文 | 8495篇 |
免费 | 821篇 |
国内免费 | 381篇 |
专业分类
电工技术 | 1422篇 |
综合类 | 714篇 |
化学工业 | 1119篇 |
金属工艺 | 840篇 |
机械仪表 | 839篇 |
建筑科学 | 449篇 |
矿业工程 | 238篇 |
能源动力 | 539篇 |
轻工业 | 271篇 |
水利工程 | 217篇 |
石油天然气 | 171篇 |
武器工业 | 72篇 |
无线电 | 412篇 |
一般工业技术 | 711篇 |
冶金工业 | 616篇 |
原子能技术 | 538篇 |
自动化技术 | 529篇 |
出版年
2024年 | 29篇 |
2023年 | 85篇 |
2022年 | 197篇 |
2021年 | 231篇 |
2020年 | 268篇 |
2019年 | 207篇 |
2018年 | 213篇 |
2017年 | 300篇 |
2016年 | 281篇 |
2015年 | 330篇 |
2014年 | 443篇 |
2013年 | 608篇 |
2012年 | 569篇 |
2011年 | 651篇 |
2010年 | 441篇 |
2009年 | 490篇 |
2008年 | 487篇 |
2007年 | 577篇 |
2006年 | 531篇 |
2005年 | 477篇 |
2004年 | 357篇 |
2003年 | 357篇 |
2002年 | 242篇 |
2001年 | 209篇 |
2000年 | 191篇 |
1999年 | 154篇 |
1998年 | 130篇 |
1997年 | 113篇 |
1996年 | 83篇 |
1995年 | 96篇 |
1994年 | 73篇 |
1993年 | 60篇 |
1992年 | 42篇 |
1991年 | 35篇 |
1990年 | 22篇 |
1989年 | 35篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1959年 | 6篇 |
1951年 | 2篇 |
排序方式: 共有9697条查询结果,搜索用时 15 毫秒
941.
942.
本文研究了开关磁阻电机(SRM)磁链特性实验检测方法,建立了基于DSP芯片TMS320F2812的SRM磁链检测系统,利用ADC模块实时采集不同转子位置的电压、电流信号,将数据传送到上位机,根据间接磁链测量原理,由数字离散方法计算磁链值,得到SRM磁链电流特性曲线和磁链-转子位置-电流模型。 相似文献
943.
机电一体化技术在纺织粗纱工艺中的应用 总被引:1,自引:1,他引:0
随着纺织产业的工业化,机电一体化技术在纺织设备上广泛应用,以采用计算机控制多电动机分部传动为典型标志的新一代粗纱机,以其优质、高速、高产、低耗、智能化、易管理维修的优越性能受到纺织企业的广泛青睐。文章将从机电一体化的五大要素(控制器、执行器、传感器、动力源、机械结构)来浅谈粗纱机的机电一体化。 相似文献
944.
Taisuke Banno Kazunobu Toshima Kazuo Kawada Shuichi Matsumura 《Journal of surfactants and detergents》2009,12(3):249-259
Gemini-type cationic surfactants containing carbonate linkages as biodegradable and chemically recyclable segments, consisting
of two long-chain alkyl groups, two quaternary ammonium groups and a linker moiety, were designed and synthesized as novel
green and sustainable cationics with improved physicochemical and biological activities. The gemini-type cationics containing
a carbonate linkage showed lower critical micelle concentration values compared to the corresponding single-type cationics.
Also, the gemini-type cationics containing a carbonate linkage in the linker moiety showed strong antimicrobial activities.
The biodegradability of the gemini-type cationics was significantly improved when a carbonate linkage was introduced into
the linker moiety. The maximum biochemical oxygen demand-biodegradability of the gemini-type cationics containing a carbonate
linkage in the linker moiety exceeded 70% after a 28-day incubation. Furthermore, the gemini-type cationics containing both
a carbonate linkage and an n-dodecyl group showed a chemical recyclability using a lipase (E.C. 3.1.1.3).
相似文献
Shuichi MatsumuraEmail: |
945.
盾叶薯蓣糖化液发酵生产2,3-丁二醇 总被引:4,自引:2,他引:2
利用克雷伯氏杆菌以盾叶薯蓣糖化液为底物发酵生产2,3-丁二醇(2,3-BD),考察了2,3-BD浓度、生产强度、有机酸生成及代谢流量分布情况. 结果表明,盾叶薯蓣中的有机酸成分能促进三羧酸循环途径和乙酸途径的代谢流,减弱琥珀酸途径的代谢流,从而提高2,3-BD的浓度. 以盾叶薯蓣糖化液为底物,采用批式流加方式,补加固体葡萄糖,发酵56 h,发酵液中2,3-BD最终浓度达到80.20 g/L,乙偶姻与2,3-BD浓度之和最终达到86.19 g/L,生产强度达到1.54 g/(L×h),比单独以葡萄糖为底物时分别提高了8.50%, 7.38%和7.69%. 相似文献
946.
High shear granulation is a common technology for particle size enlargement, but generally the product properties are badly affected by the broad size distribution generated in the process. A recently published approach by Michaels et al. [J.N. Michaels, G. Wang, L. Farber, K.P. Hapgood, J.H. Chou, S. Heidel, and G.I. Tardos, 2006, One-dimensional scale-up of high-shear granulators, Paper 243c, World Congress Particle Technology 5, Orlando (FL)] employs low binder solution spray rates and long granulation times, whilst the solids are kept in roping flow, to avoid coarse formation. The present work applies this approach to a two-component binder system with a dry powder gum and water spray as activation agent. Similarities with fluidised bed granulation and coating processes are explored. The work shows that indeed narrow size distributions of fine granules can be achieved with ease. Dimensionless numbers for spray fluxes are useful to identify operating regimes and to steer optimisation efforts. Comparison of flux numbers for different systems shows that they are not useful (yet) for detailed product and process design. Further work on material-specific quantities controlling nucleation and growth, e.g. particle wetting, is recommended. 相似文献
947.
文章主要对火灾自动报警系统在施工和调试过程中所遇到的一些问题进行分析,并就作者的实践经验提出解决这些问题的相关对策。 相似文献
948.
Xiaozhen Zhang 《Desalination》2009,249(1):364-367
ZrO2/cordierite composite microfiltration (MF) membrane was prepared by the combination of extrusion and slip casting techniques. The electrokinetic properties of as-prepared membrane were characterized by streaming potential measurements operated in tangential microfiltration mode. The influences of pH, electrolyte species and concentrations of filtered solutions on the electrokinetic properties and permeate flux were investigated. Results show that the streaming potentials are dependent on the pH, types of the electrolyte and concentrations of filtered solutions. The isoelectric point (IEP) of membranes moved from 4.2 to 5.4 with different types of 10− 3 M electrolyte solutions. The change of ionic concentration of NaCl solution does not alter the IEP of the membranes, but does make the streaming potential tend to be zero at high salt concentration. The specific adsorption of Ca2+ and SO42− ions in CaCl2 and Na2SO4 solutions onto the pore wall can alter the IEP and the net charge sign of the membrane. The as-prepared ZrO2/cordierite membrane shows a maximal permeate volume flux near the IEP. 相似文献
949.
雷直击建筑物时,流过结构钢筋的雷电流将对室内的电子系统产生电磁干扰。通过麦克斯韦基本方程,求出空间的矢量磁位,得出空间磁感应强度分布的表达形式。根据我国电力系统过电压保护和绝缘配合规程所用的雷电参数,采用波形为2.6/50μs的双指数波电流波形及幅值为10 kA的雷电流进行计算;并通过Matlab编程计算得到所需解。结果表明,导出的雷直击时高层建筑物内暂态磁场的计算公式,能反映出雷电流波头陡度对磁场的影响,这对采用短波头雷电流源进行磁场计算是很重要的。该计算方法在时间和空间上离散化,便于采用计算机对高层建筑物内雷电磁场的计算与分析。 相似文献
950.
The high thermal storage capacity of phase change material (PCM) can reduce energy consumption in buildings through energy storage and release when combined with renewable energy sources, night cooling, etc. PCM boards can be used to absorb heat gains during daytime and release heat at night. In this paper, the thermal performance of an environmental chamber fitted with phase change material boards has been investigated. During a full-cycle experiment, i.e. charging–releasing cycle, the PCM boards on a wall can reduce the interior wall surface temperature during the charging process, whereas the PCM wall surface temperature is higher than that of the other walls during the heat releasing process. It is found that the heat flux density of the PCM wall in the melting zone is almost twice as large as that of ordinary wall. Also, the heat-insulation performance of a PCM wall is better than that of an ordinary wall during the charging process, while during the heat discharging process, the PCM wall releases more heat energy. The convective heat transfer coefficient of PCM wall surface calculated using equations for a normal wall material produces an underestimation of this coefficient. The high convective heat transfer coefficient for a PCM wall is due to the increased energy exchange between the wall and indoor air. 相似文献