全文获取类型
收费全文 | 20026篇 |
免费 | 1272篇 |
国内免费 | 197篇 |
专业分类
电工技术 | 358篇 |
综合类 | 295篇 |
化学工业 | 3965篇 |
金属工艺 | 530篇 |
机械仪表 | 520篇 |
建筑科学 | 1017篇 |
矿业工程 | 173篇 |
能源动力 | 614篇 |
轻工业 | 1473篇 |
水利工程 | 209篇 |
石油天然气 | 200篇 |
武器工业 | 46篇 |
无线电 | 1780篇 |
一般工业技术 | 3635篇 |
冶金工业 | 2842篇 |
原子能技术 | 167篇 |
自动化技术 | 3671篇 |
出版年
2023年 | 217篇 |
2022年 | 427篇 |
2021年 | 764篇 |
2020年 | 483篇 |
2019年 | 500篇 |
2018年 | 634篇 |
2017年 | 608篇 |
2016年 | 646篇 |
2015年 | 642篇 |
2014年 | 770篇 |
2013年 | 1282篇 |
2012年 | 1199篇 |
2011年 | 1436篇 |
2010年 | 1056篇 |
2009年 | 987篇 |
2008年 | 1066篇 |
2007年 | 986篇 |
2006年 | 775篇 |
2005年 | 654篇 |
2004年 | 473篇 |
2003年 | 477篇 |
2002年 | 432篇 |
2001年 | 317篇 |
2000年 | 302篇 |
1999年 | 340篇 |
1998年 | 443篇 |
1997年 | 341篇 |
1996年 | 293篇 |
1995年 | 248篇 |
1994年 | 221篇 |
1993年 | 208篇 |
1992年 | 150篇 |
1991年 | 103篇 |
1990年 | 145篇 |
1989年 | 144篇 |
1988年 | 106篇 |
1987年 | 114篇 |
1986年 | 128篇 |
1985年 | 114篇 |
1984年 | 115篇 |
1983年 | 92篇 |
1982年 | 112篇 |
1981年 | 98篇 |
1980年 | 79篇 |
1979年 | 79篇 |
1978年 | 75篇 |
1977年 | 82篇 |
1976年 | 95篇 |
1975年 | 51篇 |
1974年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 1 毫秒
971.
Esperanza Troyano Daniel de Rafael Isabel Martinez-Castro Agustin Olano 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,65(2):111-114
Sepiolite (a hydrated magnesium silicate) was investigated as a catalyst for the isomerization of lactose. Factors such as temperature, concentration and time were studied. The main reaction product was lactulose; small amounts of epilactose, galactose, tagatose and 3-deoxypentulose were also formed. Product distribution indicated that the reaction routes were isomerization of the disaccharide followed by degradation of lactulose. 相似文献
972.
Elisabeth Wisker Martina Daniel Walter Feldheim 《Journal of the science of food and agriculture》1996,70(3):327-333
The effect of particle size of whole meal rye bread on the apparent digestibility of macro-nutrients, non-starch polysaccharides (NSP) and energy, the energy value of rye NSP and on faecal weight was studied in balance experiments in seven young women. The whole meal breads were prepared from one single batch of rye milled to two different particle sizes (coarse bread: 50% of particles >2 mm, 90% >1 mm; fine bread: 86% of particles <0·5 mm, 58% <0·2 mm). Two diets containing either coarse (350 g day−1) or fine (377 g day−1) whole meal bread and a low fibre control diet were consumed for 3 weeks each in a 3×3 cross-over design. Relative to the low fibre control diet, digestibility of protein, NSP and energy was significantly lower for the diets containing the whole meal breads. Digestibility of fat was the same for all diets. Partial digestible energy value for each g of NSP from coarse and fine whole meal rye bread was calculated to be −3±7 and 1±5 kJ, respectively. There were no differences between coarse and fine whole meal rye bread in the effects on the parameters measured with the exception on faecal wet weight, which was higher for the coarse bread diet. 相似文献
973.
Elizabeth D. Zeisler Daniel H. Bolton Gordon B. Jones 《International Journal of Network Management》1996,6(6):312-326
This paper describes a customer-to-carrier prototype, based on a protocol-independent interface specification and the OMNIPoint Network Management Forum service management concept. 相似文献
974.
975.
A family of elastomer composites has been developed which has outstanding tear resistance, and good tensile strength and elongation to failure as measured in a standard tensile test. These composites constitute a family in that they all are sparsely reinforced by a fishnet-like webbing of reinforcement. The members of the family differ in that the reinforcements can be as flexible as soft polyurethane rod or as stiff as carbon fiber with 3000 strands per fiber. All these composites produce outstanding tear strength and an increase in the elongation to failure in an ASTM Die-C type of tear test. The intersections of the polyurethane rod reinforcements prove to be effective crack arrestors. 相似文献
976.
A new processing system for the extrusion of microcellular polymer sheets is presented. Specifically, the detailed design of a shaping and cell growth control system is discussed in the context of an overall extrusion system design with particular emphasis on the system level functional requirements of cell nucleation, cell growth, and shaping. The principle of the basic extrusion system design is to shape a nucleated polymer/gas solution flow under pressure and accurate temperature control. In this way, the initial cell growth is controlled so as to prevent degradation of the nucleated cell density during shaping. Two foaming die designs for satisfying the initial shaping and cell growth requirements are presented. Critical experiments are then presented which verified the concept of shaping a nucleated polymer/gas solution. Moreover, these experiments demonstrated the feasibility of the overall microcellular polymer sheet extrusion system design. 相似文献
977.
978.
979.
Several surface treatments, using both commercially available coupling agents and reagents containing multiple amines, were applied to commingled continuous as-received AS4 carbon reinforcing fiber/liquid crystal polymer (LCP) matrix fibers. Unidirectional composites (normally 60 vol% carbon fiber) were prepared from as-received and treated commingled fibers and characterized. To estimate the effect the effect of the treatments on fiber-matrix adhesion, short beam shear (SBS) tests were conducted, the failure surfaces were examined, and spectroscopic studies wee performed. The mean SBS strength of the as-received unidirectional AS4 carbon fiber/LCP matrix composite system was 49 MPa. The best coupling agent and amine treatments yielded increases in composite shear strength of ∼ 10 to 20%, relative to the as-received AS4/LCP system. For the amine treatments, ESCA and FTIR analyses suggested of both the carbon and LCP fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers may have caused the increased adhesion. Moreover, SEM analysis of the failure surfaces of SBS specimens from composites prepared with the treated fibers (both with coupling agents and amines) showed that strong fiber-matrix adhesion was present. That is, failure occurred in the LCP matrix material. 相似文献
980.
针对飞秒激光加工镍基高温合金叶片气膜孔时,功率对气膜孔内壁质量影响的问题进行了研究。利用EBSD表征技术,研究了制备功率为4、10和16 W的气膜孔截面的微观组织结构。结果表明:经飞秒激光处理后,热障涂层气膜边界区域的晶体结构发生明显变化;不同功率的飞秒激光对陶瓷涂层结构的影响范围存在差异,因此制备的气膜孔边界质量也存在较大差异,其中功率为10 W的飞秒激光制备的气膜孔边界质量最佳。本研究结果对于指导飞秒激光加工工艺对材料微观组织影响具有重要意义。 相似文献