全文获取类型
收费全文 | 25419篇 |
免费 | 2398篇 |
国内免费 | 1232篇 |
专业分类
电工技术 | 1425篇 |
技术理论 | 5篇 |
综合类 | 1847篇 |
化学工业 | 4366篇 |
金属工艺 | 1461篇 |
机械仪表 | 1475篇 |
建筑科学 | 1949篇 |
矿业工程 | 734篇 |
能源动力 | 623篇 |
轻工业 | 2775篇 |
水利工程 | 410篇 |
石油天然气 | 1337篇 |
武器工业 | 173篇 |
无线电 | 3046篇 |
一般工业技术 | 2866篇 |
冶金工业 | 1100篇 |
原子能技术 | 228篇 |
自动化技术 | 3229篇 |
出版年
2024年 | 168篇 |
2023年 | 526篇 |
2022年 | 942篇 |
2021年 | 1249篇 |
2020年 | 910篇 |
2019年 | 828篇 |
2018年 | 899篇 |
2017年 | 912篇 |
2016年 | 830篇 |
2015年 | 1105篇 |
2014年 | 1365篇 |
2013年 | 1528篇 |
2012年 | 1699篇 |
2011年 | 1608篇 |
2010年 | 1462篇 |
2009年 | 1395篇 |
2008年 | 1326篇 |
2007年 | 1228篇 |
2006年 | 1204篇 |
2005年 | 967篇 |
2004年 | 738篇 |
2003年 | 924篇 |
2002年 | 1164篇 |
2001年 | 949篇 |
2000年 | 662篇 |
1999年 | 584篇 |
1998年 | 343篇 |
1997年 | 304篇 |
1996年 | 283篇 |
1995年 | 226篇 |
1994年 | 176篇 |
1993年 | 137篇 |
1992年 | 96篇 |
1991年 | 78篇 |
1990年 | 72篇 |
1989年 | 43篇 |
1988年 | 35篇 |
1987年 | 16篇 |
1986年 | 20篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1959年 | 2篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
发电公司报价辅助决策系统研究 总被引:1,自引:0,他引:1
为了适应电力市场的需要,建立了发电公司报价辅助决策系统。该系统在完成诸如成本分析等基本功能模块的基础上采用Internet技术,由信息浏览终端、应用程序服务器、历史及实时数据库服务器及防火墙等功能模块组成,其具体实现可以基于Windows系列操作平台及国内外流行的商用数据库平台,采用面向对象的程序设计方法,以VC 6.0等语言为主要开发工具。 相似文献
62.
探讨分析了前桥下横臂在卧式加工心上试制的工艺难点,从建立坐标系、数铣内孔槽、螺纹加工等方面提出相应的解决方案.在实际加工过程中取得了良好的加工效果,对解决其它类似零件具有一定的借鉴意义。 相似文献
63.
The influence of different pairs on the energy dissipation of a given hard coating during fretting has been discussed. Based on the view of the competition between the elastic and plastic deformations in a fretting experiment, it suggests that the energy dissipation rate is proportional to the elastic energy density of pairs. This trend is in agreement with the reported experimental data. For comparison, hardness of pairs is used as the index to relate the antiwear properties of a DLC film against different pairs. It is obvious that the elastic energy density of pairs is more appropriate to predict the antiwear properties of the DLC film against different pairs. 相似文献
64.
Electrically conductive fiber/yarn/fabric is one of the promising materials as flexible conductive sensors because of their sensitivity to strain, temperature and humidity. Aiming at developing of effective flexible sensors, this study investigates experimentally the strain sensing behavior of PPy (polypyrrole)-coated Lycra fibers, showing that the electrically resistance of the conductive fibers changes with the deformation of fibers. The variation in electrically resistance is mainly related to the micro-cracks appearing on the fiber surface during deformation. Then, the effects of the characteristic parameters of the micro-cracks are studied statistically by means of image processing functions in MATLAB, and the governing parameters are determined. Based on the results, a model is built to describe the variation of electrical resistance by the parameters of the micro-cracks. The analytical results are compared with the experimental results, showing an acceptable agreement. 相似文献
65.
Mark J.Schulz 《材料科学技术学报》2012,28(3):261-267
The corrosion behavior of pure Mg,AZ31,and AZ91D were evaluated in various in vitro and in vivo environments to investigate the potential application of these metals as biodegradable implant materials.DC polarization tests and immersion tests were performed in different simulated body solutions,such as distilled(DI) water,simulated body fluid(SBF) and phosphate buffered solution(PBS).Mg/Mg alloys were also implanted in different places in a mouse for in vivo weight loss and biocompatibility investigations.The in vivo subcutis bio-corrosion rate was lower than the corrosion rate for all of the in vitro simulated corrosive environments.The Mg/Mg alloys were biocompatible based on histology results for the liver,heart,kidney,skin and lung of the mouse during the two months implantation.Optical microscopy and scanning electron microscopy were carried out to investigate the morphology and topography of Mg/Mg alloys after immersion testing and implantation to understand the corrosion mechanisms. 相似文献
66.
The traditional view that the role of the composite template that is adopted in the preparation of nano-TiO2 is only for forming a pore structure and increasing the material's specific surface area is challenged by this study. The complex impact of the composite template and La-doping on the microdynamic behavior of photo-generation free charge carriers (FCCs) in the mesoporous nano-TiO2 is investigated using the transient photovoltaic (TPV) technique, supplemented by electric field-induced surface photovoltaic spectroscopy and a computer simulation method. The experimental results reveal that utilizing an appropriate composite template, such as polyethylene glycol and octadecylamine with a molar ratio of 1:1, may result in the rapid separation and prolonged diffusion distance of electron–hole pairs that were excited by a 355 nm and 50 μJ laser pulse. These may be responsible for the stronger and broader TPV response in the microsecond and millisecond regions of the La-doped nano-TiO2 in TPV spectroscopy, as compared with that for materials that used other composite templates. This response is closely related to the reduced content of the surface state located at 367 nm. A suitable level of La-doping, however, was only responsible for the stronger and broader TPV response in the microsecond region of the spectrum of the nano-TiO2. The computer simulation results confirm that the photo-generation FCCs microdynamic characteristics in the microsecond region may partially originate from the state density distribution of both the d-electron in the antibonding orbital and the p-electron in the bonding orbital moving up to higher levels, and from a broader band-gap after La-doping in the anatase lattice cell. 相似文献
67.
介绍气候变化的危害原因和我国能源利用效率与发达国家的差距,提出推进碳减排工作及发展低碳经济,以实现我国承诺的2020年减排指标的设想。 相似文献
68.
69.
70.