全文获取类型
收费全文 | 40086篇 |
免费 | 1737篇 |
国内免费 | 1371篇 |
专业分类
电工技术 | 1391篇 |
技术理论 | 2篇 |
综合类 | 1159篇 |
化学工业 | 5621篇 |
金属工艺 | 3075篇 |
机械仪表 | 1974篇 |
建筑科学 | 1862篇 |
矿业工程 | 595篇 |
能源动力 | 1288篇 |
轻工业 | 2209篇 |
水利工程 | 419篇 |
石油天然气 | 1339篇 |
武器工业 | 95篇 |
无线电 | 4639篇 |
一般工业技术 | 8715篇 |
冶金工业 | 4647篇 |
原子能技术 | 590篇 |
自动化技术 | 3574篇 |
出版年
2024年 | 73篇 |
2023年 | 345篇 |
2022年 | 531篇 |
2021年 | 748篇 |
2020年 | 608篇 |
2019年 | 698篇 |
2018年 | 877篇 |
2017年 | 897篇 |
2016年 | 874篇 |
2015年 | 964篇 |
2014年 | 1353篇 |
2013年 | 2451篇 |
2012年 | 1874篇 |
2011年 | 2373篇 |
2010年 | 1962篇 |
2009年 | 2234篇 |
2008年 | 2163篇 |
2007年 | 2155篇 |
2006年 | 2048篇 |
2005年 | 1804篇 |
2004年 | 1432篇 |
2003年 | 1332篇 |
2002年 | 1311篇 |
2001年 | 1255篇 |
2000年 | 1139篇 |
1999年 | 1260篇 |
1998年 | 1836篇 |
1997年 | 1388篇 |
1996年 | 1247篇 |
1995年 | 843篇 |
1994年 | 713篇 |
1993年 | 531篇 |
1992年 | 363篇 |
1991年 | 332篇 |
1990年 | 227篇 |
1989年 | 235篇 |
1988年 | 170篇 |
1987年 | 118篇 |
1986年 | 77篇 |
1985年 | 73篇 |
1984年 | 45篇 |
1983年 | 39篇 |
1982年 | 33篇 |
1981年 | 34篇 |
1980年 | 24篇 |
1979年 | 10篇 |
1977年 | 8篇 |
1976年 | 19篇 |
1975年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
AJ Dorta M Ferra R Bu-Colfiu L García M Gil X Escobar G Martín NA Díaz OM Perez MT Interián 《Canadian Metallurgical Quarterly》1993,10(10):490-491
It is essential to know how the immune system acts in different neurological diseases, some of them non very well known or of unknown etiology at all. It was applied Reiber and Felgenhauer's formula in 56 patients with different diseases. IgA, IgM, IgG and albumin were quantified in sera and cerebrospinal fluid by simple immunodiffusion. It was observed more frequent IgG local synthesis and IgA in this sample. 相似文献
133.
Gabriel C.M.W. Heffels J.J.M. Hou X. Ouibrahim H. 《Electronics & Communication Engineering Journal》1993,5(2):103-112
Introduction of the broadband integrated services digital network (B-ISDN) will enable network users to make use of advanced multimedia, multiparty services. With this aim in view, RACE II project R2044, MAGIC, is investigating long-term signalling requirements, architecture and protocols for B-ISDN. New service concepts are being developed in MAGIC which will provide more flexibility when compared to narrowband ISDN (N-ISDN). The service requirements and other signalling requirements, such as the separation between call and associated connections at the network-node interface, are used to determine the distribution of functions over the network. The signalling protocols which are used to exchange the signalling information are subsequently developed. These signalling protocols are simulated to prove the performance and the feasibility of call handling concepts 相似文献
134.
X. Zhang J.R. Ho C.P. Grigoropoulos 《International Journal of Heat and Mass Transfer》1996,39(18):3835-3844
Heat and mass transfer at the nanosecond time scale and the nanometer length scale in pulsed laser fabrication of ultra-shallow p+-junctions is studied in this work. A new technique is developed to fabricate the ultra-shallow p+-junctions with pulsed laser doping of crystalline silicon with a solid spin-on-glass (SOG) dopant, through the nanosecond pulsed laser heating, melting, and boron mass diffusion in the 100 nm thin silicon layer close to the surface. High boron concentration of 1020 atoms cc−1 and the ‘box-like’ junction profile are achieved. The key mechanism determining the ‘box-like’ junction shape is found to be the melt-solid interface limited diffusion. The ultra-shallow p+-junctions with the depth from 30 to 400 nm are successfully made by the excimer laser. The optimal laser fluence condition for SOG doping is found about 0.6–0.8 J cm−2 by studying the ultra-shallow p+-junction boron profiles measured by the secondary ion mass spectroscopy (SIMS) vs the laser fluence and the pulse number. The one-dimensional numerical analysis agrees reasonably with the experiment, within the available physical picture. Possible mechanisms such as boron diffusivity dependence on the dopant concentration in the molten silicon are proposed. 相似文献
135.
136.
137.
138.
The changes in the intestinal mucosal permeability were observed by quantitatively assessing plasma to luminal clearance of 99mTc-labeled DTPA, and the influence of platelet activating factor (PAF) on it was investigated. The results showed that intestinal permeability was significantly elevated after severe burn and was positively correlated with increase in PAF in the intestinal tissue (r = 0.94, P < 0.01). PAF antagonist therapy could significantly attenuate postburn intestinal mucosal permeability. It is concluded that PAF is one of the important factors causing increased intestinal permeability after severe burn. 相似文献
139.
J. S. Hong L. Gao X. X. Huang B. A. Shaw D. P. Thompson 《Journal of Materials Science》1996,31(4):957-962
Tetragonal zirconia polycrystalline (TZP) ceramics containing SiC reinforcement in the form of fine particles (nano-scale), particles (micro-scale), whiskers and platelets were synthesized by hot-pressing. The effects of morphology and grain size of SiC reinforcement on the strength and fracture toughness at room temperature were investigated. The addition of SiC (in whatever form) caused decreases in strength and toughness at room temperature with the exception of whisker-reinforced materials. Toughness fell off with increasing temperature, but nevertheless retained about one-half of the room-temperature value for that particular SiC reinforcement. However, the whisker- and particle-reinforced materials had higher K
lc values at high temperature than fine particle- or platelet-reinforced materials, with values in excess of 7 MPa m1/2 at 1000 °C. The microstructure was examined for SiC whisker-reinforced/TZP materials by TEM and HREM, to examine the nature of the whisker/zirconia interface. 相似文献
140.