全文获取类型
收费全文 | 63186篇 |
免费 | 4872篇 |
国内免费 | 2781篇 |
专业分类
电工技术 | 3370篇 |
技术理论 | 6篇 |
综合类 | 4274篇 |
化学工业 | 10607篇 |
金属工艺 | 3920篇 |
机械仪表 | 3968篇 |
建筑科学 | 4769篇 |
矿业工程 | 2294篇 |
能源动力 | 1995篇 |
轻工业 | 3664篇 |
水利工程 | 1095篇 |
石油天然气 | 4573篇 |
武器工业 | 482篇 |
无线电 | 6560篇 |
一般工业技术 | 7323篇 |
冶金工业 | 3410篇 |
原子能技术 | 733篇 |
自动化技术 | 7796篇 |
出版年
2024年 | 244篇 |
2023年 | 987篇 |
2022年 | 1716篇 |
2021年 | 2444篇 |
2020年 | 1849篇 |
2019年 | 1662篇 |
2018年 | 1852篇 |
2017年 | 2055篇 |
2016年 | 1838篇 |
2015年 | 2402篇 |
2014年 | 3057篇 |
2013年 | 3558篇 |
2012年 | 3772篇 |
2011年 | 4147篇 |
2010年 | 3808篇 |
2009年 | 3393篇 |
2008年 | 3391篇 |
2007年 | 3346篇 |
2006年 | 3331篇 |
2005年 | 2889篇 |
2004年 | 2109篇 |
2003年 | 2184篇 |
2002年 | 2501篇 |
2001年 | 2100篇 |
2000年 | 1640篇 |
1999年 | 1704篇 |
1998年 | 1251篇 |
1997年 | 1067篇 |
1996年 | 1103篇 |
1995年 | 846篇 |
1994年 | 631篇 |
1993年 | 468篇 |
1992年 | 365篇 |
1991年 | 274篇 |
1990年 | 206篇 |
1989年 | 166篇 |
1988年 | 153篇 |
1987年 | 88篇 |
1986年 | 69篇 |
1985年 | 37篇 |
1984年 | 38篇 |
1983年 | 27篇 |
1982年 | 25篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
讨论了现代企业的过程观经及企业过程的构成,提出了企业生产经营全过程的作业管理思想,并对全过程作业管理的基本内容进行了探讨,分析了企业过程重组和优化的驱动因素、目标和实现途径,最后概述了全过程作业管理的支撑技术。 相似文献
72.
文章结合水利水电行业的建设特点,着重介绍在项目管理技术日益成熟的今天如何开展水利水电项目管理人力资源的培训与开发工作。作为项目管理活动中至关重要的一个环节,人力资源培训与开发起到了及时为项目输送合适的人才,在项目管理过程中不断提高员工素质和适应力,全力推动项目进展等作用。 相似文献
73.
To reduce the receiver complexity of the space-time bit-interleaved coded modulation (ST-BICM) scheme, this letter describes a turbo-type iterative structure consisting of a modified Gaussian approximation (MGA) detector and an a posteriori probability (APP) decoder. Utilizing the characteristics of the interleaving and the central limited theoretic, the MGA detector first assumes the superposition of the transmitted signals as a Gaussian random variable. Then, P most significant signal combinations are identified to calculate the log-likelihood ratio of each bit. Without any pre-process on the received signals, the proposed method is free of matrix inverse operation and can be applied in systems with more transmit antennas than receive antennas. Furthermore, the performance of the MGA approaches that of the optimal detection 相似文献
74.
75.
Transient performance study of a brushless doubly fed twin stator induction generator 总被引:2,自引:0,他引:2
This paper presents theoretical, simulation, and experimental study of the brushless doubly fed twin stator induction generator (BDFTSIG) dynamics under vector control based on the orientation on the power machine stator flux. A complex transfer function is derived which links the control current and power winding current space vectors in the field coordinates. Based on this result, the transient response of the BDFTSIG to step changes in the control current is examined theoretically. The oscillatory transients are explained in detail and linked to control flux transients triggered whenever operation point of the generator is changed. Furthermore, BDFTSIG operation with closed loop control of the power machine active and reactive powers is examined theoretically and experimentally. It is shown that in the closed loop operation, the system damping may be reduced so that the PI controller gains must be properly selected to achieve a good transient response. 相似文献
76.
For the purpose of remediation of soils polluted by heavy metals, the use of some strong synthetic chelating agents such as ethylenediaminetetraacetic acid (EDTA) has been proposed. However, EDTA would not be considered as the preferential choice for the remediation of soil polluted with heavy metals like copper because of its nonbiodegradability and permanent residence in the natural environment. In the present work, some novel environmentally benign chelating agents, glucosamine hydrochloride, chito-oligosaccharide and
-asparaginic-N,N-diacetic acid (ASDA) were screened to find alternatives to EDTA by investigating the elution of copper from vermiculite with these reagents and comparing their effectiveness with EDTA. The effects of suspension contact time, reagent concentration and equilibrium pH of the solution on the removal of copper were examined. A stoichiometric amount of EDTA can quantitatively remove copper in both acidic and neutral conditions. Chito-oligosaccharide was a slightly less-effective reagent under acidic conditions compared to EDTA, and an amount well in excess of stoichiometry is required to achieve the maximum removal of copper from vermiculite. Glucosamine hydrochloride shows a relatively weak ability for the liberation of copper. The elution behavior of ASDA was equivalent to EDTA in acidic and neutral media. It was concluded that ASDA is the best substitute for EDTA because of its similar high complexing ability and superior biodegradability. 相似文献
77.
Haiquan Guo Shiquan Tao 《IEEE sensors journal》2007,7(3):323-328
Palladium-doped silica nanocomposites were synthesized via a sol-gel technique combined with a template of Triton X-100 micelle. The freshly prepared sol sample of Pd-doped silica nanocomposites was investigated by TEM. Determined from the TEM image, the sizes of the Pd nanoparticles are narrowly distributed, which are around 30 nm in diameter. The prepared sol solution of the sample was injected into a Tygon Microbore Autoanalysis tubing. After 14 days gelatinization, a transparent porous optical fiber was obtained. The response of the fiber to hydrogen gas was tested by using a fiber-optic spectrometric method. The palladium-doped silica nanocomposite fiber is sensitive upon exposure to hydrogen gas and the response is reversible. This palladium-doped silica nanocomposite fiber can be applied as a new kind of hydrogen gas sensor 相似文献
78.
根据生产实践 ,结合PLC的技术特点和 385m2 凯利式叶滤机的电气联锁特性 ,阐述了应用PLC技术 ,可进一步提高 385m2 凯利式叶滤机的运转率和自动化水平。 相似文献
79.
鉴于目前电信的声讯系统中竞争的激烈性,它们急需要提高自身的系统集成度及高可用性,保证以最小的投资获得最丰厚的回报,由此出现了CompactPCI的系列产品,它不仅可以大大提高系统的集成度,同时对于系统的高可用性也进行了充分的考虑。本文将就声讯系统中基于CompactPCI的应用进行分析。 相似文献
80.