全文获取类型
收费全文 | 287084篇 |
免费 | 35524篇 |
国内免费 | 15078篇 |
专业分类
电工技术 | 19770篇 |
技术理论 | 6篇 |
综合类 | 21912篇 |
化学工业 | 52005篇 |
金属工艺 | 15169篇 |
机械仪表 | 17366篇 |
建筑科学 | 21886篇 |
矿业工程 | 7763篇 |
能源动力 | 7994篇 |
轻工业 | 26610篇 |
水利工程 | 6179篇 |
石油天然气 | 11964篇 |
武器工业 | 2608篇 |
无线电 | 36122篇 |
一般工业技术 | 35512篇 |
冶金工业 | 10877篇 |
原子能技术 | 3125篇 |
自动化技术 | 40818篇 |
出版年
2024年 | 1127篇 |
2023年 | 3718篇 |
2022年 | 7299篇 |
2021年 | 10246篇 |
2020年 | 8883篇 |
2019年 | 8884篇 |
2018年 | 9436篇 |
2017年 | 10988篇 |
2016年 | 10496篇 |
2015年 | 14014篇 |
2014年 | 16906篇 |
2013年 | 20464篇 |
2012年 | 21083篇 |
2011年 | 21689篇 |
2010年 | 20626篇 |
2009年 | 19765篇 |
2008年 | 19157篇 |
2007年 | 18249篇 |
2006年 | 16928篇 |
2005年 | 13619篇 |
2004年 | 10329篇 |
2003年 | 9087篇 |
2002年 | 9438篇 |
2001年 | 8297篇 |
2000年 | 6520篇 |
1999年 | 4817篇 |
1998年 | 2876篇 |
1997年 | 2407篇 |
1996年 | 2237篇 |
1995年 | 1910篇 |
1994年 | 1551篇 |
1993年 | 1009篇 |
1992年 | 803篇 |
1991年 | 606篇 |
1990年 | 491篇 |
1989年 | 379篇 |
1988年 | 300篇 |
1987年 | 208篇 |
1986年 | 148篇 |
1985年 | 106篇 |
1984年 | 87篇 |
1983年 | 65篇 |
1982年 | 57篇 |
1981年 | 66篇 |
1980年 | 65篇 |
1979年 | 41篇 |
1978年 | 18篇 |
1977年 | 22篇 |
1976年 | 25篇 |
1951年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
N. Jongen M. Donnet P. Bowen J. Lemaître H. Hofmann R. Schenk C. Hofmann M. Aoun‐Habbache S. Guillemet‐Fritsch J. Sarrias A. Rousset M. Viviani M.T. Buscaglia V. Buscaglia P. Nanni A. Testino J.R. Herguijuela 《化学工程与技术》2003,26(3):303-305
The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production. 相似文献
12.
13.
通过密度测定和DSC热分析,观测了超高分子量聚乙烯的辐射效应。实验结果表明:在吸收剂量0—1.13MGy范围内,密度随吸收剂量的增加而增大,熔化热和熔点也有所增加,特别是在低剂量范围内增加十分明显。以上结果都说明,超高分子量聚乙烯在辐照过程中,结晶在完善或有新的结晶形成 相似文献
14.
LeeSiewWei 《水利水电快报》2002,23(19):1-5
在英国伦敦多克兰斯轻便铁路刘易舍姆延长线(DLR-LWE)双隧道掘进工程中,在敏感建筑物下进行了补偿灌浆,以防止隧道开挖引起的过度沉降。但是,过度灌浆也会对隧道下部施加超越。介绍了由隧道掘进承包商所编辑的关于地面和建筑物沉降以及由补偿灌浆引起的隧道衬砌变形的详细现场监测数据。 相似文献
15.
恢复城市水环境的自然生态 总被引:5,自引:0,他引:5
为了确保城市社会经济的可持续发展,城市的水资源管理是重要的一环,而且,这项管理会逐步从防洪、水资源利用的量的管理向水质管理、空间管理和生态体系的保护等综合管理发展,其中恢复河流清澈、优美的自然生态,科学有效地建设城市水环境是个需要研究的大课题. 相似文献
16.
Liang Y.C. Wenjiang Zeng Pick Hong Ong Zhaoxia Gao Jun Cai Balasubramanian N. 《Electron Device Letters, IEEE》2002,23(12):700-703
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology. 相似文献
17.
In this paper, a localized MEI method (L-MEI) is developed and combined with the domain decomposition method (DDM) for the simulation of scattering by a concave cylinder. In the L-MEI, the whole domain is decomposed into many subdomains. Different from the conventional MEI method, the MEI coefficients of the L-MEI method in each subdomain are only dependent on the localized metrons that are defined in the subdomain. The localization of metrons has the following advantages: (1) speeding up the calculation of MEI coefficients and saving memory, (2) making the MEI method available for concave structures, and (3) obtaining a band sparse matrix directly without any modification 相似文献
18.
Flame structure and NO emission characteristics in counterflow diffusion flame of blended fuel of H2/CO2/Ar have been numerically simulated with detailed chemistry. The combination of H2, CO2 and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of CO2. A radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. The detailed chemistry adopts the reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions. All mechanisms including thermal, NO2, N2O and Fenimore are taken into account to separately evaluate the effects of CO2 addition on NO emission characteristics. The increase of added CO2 quantity causes flame temperature to fall since at high strain rates a diluent effect is prevailing and at low strain rates the breakdown of CO2 produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the contribution of NO production by N2O and NO2 mechanisms are negligible and that thermal mechanism is concentrated on only the reaction zone. As strain rate and CO2 quantity increase, NO production is remarkably augmented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
19.
Hong Jeong Jeong‐Ho Park 《International Journal of Adaptive Control and Signal Processing》2002,16(1):1-23
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
20.