全文获取类型
收费全文 | 122660篇 |
免费 | 11315篇 |
国内免费 | 6835篇 |
专业分类
电工技术 | 8218篇 |
技术理论 | 3篇 |
综合类 | 8315篇 |
化学工业 | 19109篇 |
金属工艺 | 7389篇 |
机械仪表 | 8341篇 |
建筑科学 | 8650篇 |
矿业工程 | 3283篇 |
能源动力 | 4002篇 |
轻工业 | 9090篇 |
水利工程 | 2667篇 |
石油天然气 | 4759篇 |
武器工业 | 1284篇 |
无线电 | 15849篇 |
一般工业技术 | 15092篇 |
冶金工业 | 5410篇 |
原子能技术 | 1842篇 |
自动化技术 | 17507篇 |
出版年
2024年 | 464篇 |
2023年 | 1583篇 |
2022年 | 3085篇 |
2021年 | 4584篇 |
2020年 | 3397篇 |
2019年 | 2925篇 |
2018年 | 3332篇 |
2017年 | 3772篇 |
2016年 | 3677篇 |
2015年 | 4894篇 |
2014年 | 6411篇 |
2013年 | 7711篇 |
2012年 | 8968篇 |
2011年 | 10094篇 |
2010年 | 9076篇 |
2009年 | 8795篇 |
2008年 | 8728篇 |
2007年 | 8185篇 |
2006年 | 7603篇 |
2005年 | 6101篇 |
2004年 | 4644篇 |
2003年 | 3850篇 |
2002年 | 3764篇 |
2001年 | 3198篇 |
2000年 | 2536篇 |
1999年 | 1937篇 |
1998年 | 1613篇 |
1997年 | 1180篇 |
1996年 | 1026篇 |
1995年 | 782篇 |
1994年 | 565篇 |
1993年 | 455篇 |
1992年 | 323篇 |
1991年 | 266篇 |
1990年 | 197篇 |
1989年 | 206篇 |
1988年 | 141篇 |
1987年 | 121篇 |
1986年 | 109篇 |
1985年 | 68篇 |
1984年 | 58篇 |
1983年 | 56篇 |
1982年 | 50篇 |
1981年 | 46篇 |
1980年 | 46篇 |
1979年 | 21篇 |
1977年 | 30篇 |
1976年 | 36篇 |
1975年 | 18篇 |
1959年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
11.
12.
13.
Chel-Jong Choi Tae-Yeon Seong Key-Min Lee Joo-Hyoung Lee Young-Jin Park Hi-Deok Lee 《Electron Device Letters, IEEE》2002,23(4):188-190
The leakage mechanism in p+/n shallow junctions fabricated using Co silicidation and shallow trench isolation processes has been investigated using transmission electron microscopy (TEM) combined with selective chemical etching. TEM and TSUPREM-4 simulation results show that dopant profiles bend upward near the edge of the active region. The formation of the abnormal profile is attributed to transient enhanced diffusion induced by source/drain implantation. Based on the TEM and simulation results, it is suggested that the shallower junctions formed near the active edge can serve as a source for leakage current in the silicided p+ /n shallow junctions 相似文献
14.
The effect of high oxide field stress is studied using capacitance-time (C-t) measurements of MOS capacitors. The stress results in parallel shifts of the C-t curve along the time axis. The flatband voltage shift ΔVFB obtained from the initial deep depletion capacitance C(t=0+) follows the same trend as that from the high-frequency C-V characteristics. However, the discrepancy between the two flatband voltages becomes larger as the stress increases due to the effect of interface charges on C-t characteristics. The flatband voltage difference is converted to interface trap density, showing a steady increase of interface trap density with stress, similar to that from low-frequency C-V measurements 相似文献
15.
MA Steller KJ Gurski M Murakami RW Daniel KV Shah E Celis A Sette EL Trimble RC Park FM Marincola 《Canadian Metallurgical Quarterly》1998,4(9):2103-2109
Human papillomavirus (HPV) infection has been causally associated with cervical cancer. We tested the effectiveness of an HLA-A*0201-restricted, HPV-16 E7 lipopeptide vaccine in eliciting cellular immune responses in vivo in women with refractory cervical cancer. In a nonrandomized Phase I clinical trial, 12 women expressing the HLA-A2 allele with refractory cervical or vaginal cancer were vaccinated with four E786-93 lipopeptide inoculations at 3-week intervals. HLA-A2 subtyping was also performed, and HPV typing was assessed on tumor specimens. Induction of epitope-specific CD8+ T-lymphocyte (CTL) responses was analyzed using peripheral blood leukapheresis specimens obtained before and after vaccination. CTL specificity was measured by IFN-gamma release assay using HLA-A*0201 matched target cells. Clinical responses were assessed by physical examination and radiographic images. All HLA-A*0201 patients were able to mount a cellular immune response to a control peptide. E786-93-specific CTLs were elicited in 4 of 10 evaluable HLA-A*0201 subjects before vaccination, 5 of 7 evaluable HLA-A*0201 patients after two vaccinations, and 2 of 3 evaluable HLA-A*0201 cultures after all four inoculations. Two of three evaluable patients' CTLs converted from unreactive to reactive after administration of all four inoculations. There were no clinical responses or treatment toxicities. The ability to generate specific cellular immune responses is retained in patients with advanced cervical cancer. Vaccination with a lipidated HPV peptide epitope appears capable of safely augmenting CTL reactivity. Although enhancements of cellular immune responses are needed to achieve therapeutic utility in advanced cervical cancer, this approach might prove useful in treating preinvasive disease. 相似文献
16.
Bimolecular hydrogen transfer and skeletal isomerization the important secondary reac-tions among catalytic cracking reactions,which affect product yield distribution and product quality,Catalyst properties and operating parameters have great impact on bimolecular hydrogen transfer and skeletal isomerization reactions .Bimolecular hydrogen transfer activity and skeletal isomrization activity of USY-containing catalysts are higher thn that of ZSM-5-containing catalyst.Coke deposition on the active sites of catalyst may suppress bimolecular hydrogen transfer activity and skeletal isomer-ization activity of catlys in different degrees.Short raction time causes a decrease of hydrogen trans-fer reaction,but and increase of skeletal isomerization reaction compared to cracking reaction in catalytic cracking process. 相似文献
17.
Overview of ship-design expert systems 总被引:1,自引:0,他引:1
Expert systems constitute a branch of artificial intelligence, and their unique characteristics enable computer systems to perform at the level of a human expert by the use of algorithms that can capture domain-specific knowledge. Through an extensive survey of research about ship-design expert systems, we conclude that although development and implementation of expert systems for ship design offer substantial barriers, the shipbuilding industry needs them nonetheless. We examine the major reasons that use of expert systems in this industry has lagged behind. These include the problems of integration with existing computer-aided design systems, problems of knowledge representation and sizable development costs. We discuss in detail some key factors that can lead to the solution of these problems. 相似文献
18.
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
19.
20.
一种支持QoS的拓扑自适应动态组播路由算法 总被引:3,自引:0,他引:3
YAM、QoSMIC、DSDMR等一类支持QoS的动态组播路由算法允许组播成员动态地加入和离开,同时为接收方提供多个可选择的组播接入路径,以满足不同应用的QoS需求。但这些算法普遍存在控制信令开销大和结点加入时延长,可扩展性不好等问题。本文在分析这些算法的基础上,提出改进的支持QoS的动态组播路由算法,即拓扑自适应动态组播路由(Topology Adaptive Dynamic Multicast Routing,TADMR)算法。该算法避免了以往算法中大部分盲目的路径搜索,并使结点加入时延不再受限于固定的等待时钟,而与网络拓扑相自适应。性能分析和仿真结果表明,该算法具有较低的控制信令开销和结点加入时延,适用于各种网络规模和群组规模,具有良好的可扩展性。 相似文献