全文获取类型
收费全文 | 348717篇 |
免费 | 25744篇 |
国内免费 | 17087篇 |
专业分类
电工技术 | 21674篇 |
技术理论 | 74篇 |
综合类 | 47455篇 |
化学工业 | 36844篇 |
金属工艺 | 12071篇 |
机械仪表 | 18932篇 |
建筑科学 | 51386篇 |
矿业工程 | 19869篇 |
能源动力 | 10435篇 |
轻工业 | 19946篇 |
水利工程 | 19166篇 |
石油天然气 | 16341篇 |
武器工业 | 3065篇 |
无线电 | 22553篇 |
一般工业技术 | 23225篇 |
冶金工业 | 20976篇 |
原子能技术 | 3271篇 |
自动化技术 | 44265篇 |
出版年
2024年 | 1020篇 |
2023年 | 3109篇 |
2022年 | 6306篇 |
2021年 | 7505篇 |
2020年 | 7975篇 |
2019年 | 6481篇 |
2018年 | 6078篇 |
2017年 | 7719篇 |
2016年 | 9204篇 |
2015年 | 10419篇 |
2014年 | 20575篇 |
2013年 | 17969篇 |
2012年 | 23145篇 |
2011年 | 25034篇 |
2010年 | 20087篇 |
2009年 | 20861篇 |
2008年 | 19304篇 |
2007年 | 25174篇 |
2006年 | 24075篇 |
2005年 | 20953篇 |
2004年 | 17694篇 |
2003年 | 15932篇 |
2002年 | 13027篇 |
2001年 | 11060篇 |
2000年 | 9311篇 |
1999年 | 7434篇 |
1998年 | 5465篇 |
1997年 | 4645篇 |
1996年 | 4204篇 |
1995年 | 3514篇 |
1994年 | 3127篇 |
1993年 | 2324篇 |
1992年 | 2039篇 |
1991年 | 1493篇 |
1990年 | 1299篇 |
1989年 | 1160篇 |
1988年 | 918篇 |
1987年 | 621篇 |
1986年 | 485篇 |
1985年 | 415篇 |
1984年 | 387篇 |
1983年 | 276篇 |
1982年 | 238篇 |
1981年 | 200篇 |
1980年 | 164篇 |
1979年 | 136篇 |
1978年 | 75篇 |
1977年 | 81篇 |
1976年 | 63篇 |
1975年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
HHD型核子秤电离室已成功地使用于HCS型核子秤.对它的各种物理性能指标进行了检测,各项性能指标都达到了设计要求。 相似文献
52.
S. Gratch 《International Journal of Thermophysics》1985,6(6):541-544
Historical developments regarding the realization of the importance of reliable thermophysical properties data in engineering applications are presented. The events leading to the establishment of the Symposium on Thermophysical Properties in 1959 and the accomplishments of the symposia series since then are discussed. Contributions of the National Bureau of Standards to the thermophysical properties field are described.Welcoming address presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A. 相似文献
53.
我国建筑涂料技术进步简评 总被引:1,自引:1,他引:0
从以下诸方面简述我国建筑涂料的技术进步:⑴新品种涂料的研制开发;⑵加强对配套材料及施工技术的研究;⑶超细填料在涂料中的应用;⑷计算机自动配色技术;⑸产品标准的修订;⑹建筑涂料的实用范围扩大。 相似文献
54.
凸轮进给式双管平头倒棱机 总被引:3,自引:0,他引:3
研制的凸轮进给式双管平头倒棱机可自动完成上料→夹紧→平头倒棱→松开→退料动作循环,同步准确,可靠性高,平头倒棱质量好。介绍了该装置的工作原理、工作程序、技术性能、设备组成以及刀具和夹具的特点。 相似文献
55.
Jan A. Derecki 《Journal of Great Lakes research》1985,11(3):201-207
Periodic man-made changes in the outlet of Lake Huron through the St. Clair River date back to the middle of the last century. These artificial channel changes have been well documented during the present century. They consist of dredging for commercial gravel removal in the upper river during 1908–25 and uncompensated navigation improvements for the 7.6-m (25-ft) and 8.2-m (27-ft) projects completed in 1933 and 1962, respectively. The total effect of these changes on the levels of Lakes Michigan and Huron (hydraulically one lake) and on the upper St. Clair River profile was determined with dynamic flow models. The ultimate effect of the above dredging was a permanent lowering of the Lake Michigan-Huron levels 0.27 m (0.89 ft), which represents a tremendous loss of freshwater resource [32 km3 (7.7 mi3)]. 相似文献
56.
邹志强 《稀有金属与硬质合金》1994,(1)
根据第十三届国际普兰西会议获得的信息,对国际上难熔金属、硬质合金、硬质材料和涂层技术等方面近几年来的研究和发展动态进行了综合评述。最后,提出了几点自己的看法。 相似文献
57.
康山金矿地质地球化学特征及其成因 总被引:3,自引:1,他引:2
康山金矿产在豫西熊耳山古隆起区的结晶基底太华群和盖层中元古界熊耳群地层接触界面附近,矿体严格受构造破碎蚀变带控制。流体包裹体,稳定同位素等研究表明,成矿物质来自太华群变质岩,成矿流体的性质与变质热液截然不同,而与花岗岩浆热液相近似。该矿床的形成与燕山期发生的同构造-花岗岩浆期热液活动有关,金沉淀成矿阶段有大气水的混入。 相似文献
58.
59.
The compaction properties of an investigational drug are studied by the use of a compaction simulator. The effects of punch velocity over the range of 30-640 mm-1 on the compaction properties of the pure drug and a variety of formulas incorporating a high dose of the active compound have been investigated. The data were analyzed by applying the Heckel equation. The pure drug was found to have a high yield pressure at a relatively low punch velocity of 31 mm-1. As the punch velocity was increased there was a decrease in crushing strength, primarily as a result of increasing yield pressure. These findings indicate that the pure drug predominantly consolidated by fragmentation and elastic deformation, with a slow plastically deforming component. The information obtained on the consolidation mechanism of the pure drug and, subsequently, on model formulas were instrumental in the design and selection of a robust formula and granulation process. The advantages of conducting dosage form design and characterization studies during the early phase of tablet formulation using means such as a compaction simulator are emphasized in this investigation. 相似文献
60.
Isolation and preliminary characterization of Pichia pinus mutants insensitive to glucose repression
A new method for the isolation of glucose repression-insensitive mutants in the methylotrophic yeast Pichia pinus was developed. The method is based on screening of small suspension samples derived from 2-deoxyglucose-resistant colonies for alcohol oxidase activity. Alcohol oxidase activity was evaluated by determination of formaldehyde excreted by cells. Mutants with glucose non-repressible alcohol oxidase and catalase synthesis were obtained. All mutants grew poorly on D -xylose compared to the wild type, whereas growth on L -arabinose was similar to the wild type. Changes in the glucose transport system were suggested to be responsible for altered growth characteristics and defective glucose repression. 相似文献