全文获取类型
收费全文 | 21891篇 |
免费 | 1752篇 |
国内免费 | 1047篇 |
专业分类
电工技术 | 1132篇 |
技术理论 | 4篇 |
综合类 | 1445篇 |
化学工业 | 4171篇 |
金属工艺 | 1352篇 |
机械仪表 | 1225篇 |
建筑科学 | 1581篇 |
矿业工程 | 583篇 |
能源动力 | 554篇 |
轻工业 | 1326篇 |
水利工程 | 351篇 |
石油天然气 | 1388篇 |
武器工业 | 137篇 |
无线电 | 2470篇 |
一般工业技术 | 2809篇 |
冶金工业 | 1059篇 |
原子能技术 | 246篇 |
自动化技术 | 2857篇 |
出版年
2024年 | 96篇 |
2023年 | 414篇 |
2022年 | 597篇 |
2021年 | 836篇 |
2020年 | 669篇 |
2019年 | 587篇 |
2018年 | 616篇 |
2017年 | 700篇 |
2016年 | 584篇 |
2015年 | 797篇 |
2014年 | 965篇 |
2013年 | 1231篇 |
2012年 | 1306篇 |
2011年 | 1377篇 |
2010年 | 1287篇 |
2009年 | 1304篇 |
2008年 | 1191篇 |
2007年 | 1166篇 |
2006年 | 1157篇 |
2005年 | 1033篇 |
2004年 | 704篇 |
2003年 | 682篇 |
2002年 | 710篇 |
2001年 | 581篇 |
2000年 | 553篇 |
1999年 | 669篇 |
1998年 | 523篇 |
1997年 | 433篇 |
1996年 | 399篇 |
1995年 | 356篇 |
1994年 | 311篇 |
1993年 | 214篇 |
1992年 | 169篇 |
1991年 | 129篇 |
1990年 | 81篇 |
1989年 | 103篇 |
1988年 | 56篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
Aimin Xiang Zhongjie Du Qinghua Zeng Chen Zhang Hangquan Li 《Polymer International》2005,54(10):1366-1370
This paper presents recent efforts on the preparation of flexible polyhedral particles via concentrated emulsion templating polymerization in which the hydrophilic monomer (acrylamide) and hydrophobic monomer (butyl acrylate) are polymerized simultaneously in the continuous and dispersed phase, respectively. Such templating polymerization has been enhanced in our systems owing to the introduction of acrylamide monomer and their higher polymerization rate in continuous phase as compared with butyl acrylate in dispersed phase. Diffusion between the different phases was also inhibited. Furthermore, the stability of the concentrated emulsion and the molecular weight of the produced poly(butyl acrylate) were found to be significantly affected by the amount of redox initiator. The morphology of the particles could be controlled by varying the volume fraction of the dispersed phase and the polyhedral particles were achieved at higher volume fraction. Copyright © 2005 Society of Chemical Industry 相似文献
3.
4.
An innovative method for modelling biological processes under anaerobic conditions is presented and discussed. The method is based on titrimetric and off-gas measurements. Titrimetric data is recorded as the addition rate of hydroxyl ions or protons that is required to maintain pH in a bioreactor at a constant level. An off-gas analysis arrangement measures, among other things, the transfer rate of carbon dioxide. The integration of these signals results in a continuous signal which is solely related to the biological reactions. When coupled with a mathematical model of the biological reactions, the signal allows a detailed characterisation of these reactions, which would otherwise be difficult to achieve. Two applications of the method to the enhanced biological phosphorus removal processes are presented and discussed to demonstrate the principle and effectiveness of the method. 相似文献
5.
6.
Analysis of characteristic odors from human male axillae 总被引:7,自引:0,他引:7
Xiao -nong Zeng James J. Leyden Henry J. Lawley Kiyohito Sawano Isao Nohara George Preti 《Journal of chemical ecology》1991,17(7):1469-1492
A number of studies concerning the analysis of axillary odors have assumed that the characteristic odor produced in the axillae is due to volatile steroids and isovaleric acid. Organoleptic evaluation of Chromatographic eluants from axillary extracts was employed to isolate the region in the chromatogram where the characteristic odor eluted. The odor of the dissolved eluant was eliminated when it was treated with base, suggesting that acids make up the characteristic axillary odor. Subsequent extraction of the pH-adjusted axillary extract in conjunction with organoleptic evaluation of the Chromatographic eluant, preparative gas chromatography, and analysis by GC-MS as well as GC-FTIR showed the presence of a number of C6 to C11 straight-chain, branched, and unsaturated acids as important contributors to the axillary odor. The major odor component is (E)-3-methyl-2-hexenoic acid. Three homologous series of minor components are also important odor contributors; these consist of the terminally unsaturated acids, the 2-methyl-C6 to -C10 acids and the 4-ethyl-C5 to -C11 acids. These types of acids have not been reported previously as components of the human axillary secretions and have not been proposed previously as part of the principal odor components in this area. 相似文献
7.
8.
为了将高纯锗(HPGe)探测器用于快定时的物理实验中,本实验研究厂影响高纯锗探测器定时谱仪时间性能的各种因素,找出了获得谱仪最小时间分辨的各种最佳参数。并建立了分辨时间为4.19ns,能量分辨率为20keV,微分非线性好于±2.0%,计效率可承受120×10 ̄3s ̄(-1)的时间微分扰动角关联谱仪。利用此谱仪,以 ̄(204)Bi为探针核,研究了Bi系高温超导的微观机理,取得了较好的结果。 相似文献
9.
Zeng Yanwei Xue Wanrong A. Benedetti G. Fagherazzi 《Journal of Materials Science》1994,29(4):1045-1050
By using the X-ray diffraction profile-fitting technique, the microstructures of Sm, Mn-modified PbTiO3 piezoelectric ceramic discs, including ferroelectric domain sizes, microstrains, and their variations with the poling strength have been quantitatively investigated. The results manifest that the modified PbTiO3 ceramics contain a high density of domain walls due to the presence of finely-divided coherent domain structures (tens of nanometres in dimension). The poling treament can evidently influence the domain-size distribution, with a more homogeneous microstructure being developed; however, it simultaneously causes high anisotropic microstrains within the structure which, together with the high density of domain walls, is expected to be responsible for the unusual high electromechanical coupling properties possessed by this material. 相似文献
10.