全文获取类型
收费全文 | 39896篇 |
免费 | 4227篇 |
国内免费 | 2631篇 |
专业分类
电工技术 | 2881篇 |
技术理论 | 1篇 |
综合类 | 3458篇 |
化学工业 | 5363篇 |
金属工艺 | 2447篇 |
机械仪表 | 2517篇 |
建筑科学 | 2713篇 |
矿业工程 | 1239篇 |
能源动力 | 1189篇 |
轻工业 | 4177篇 |
水利工程 | 1180篇 |
石油天然气 | 1256篇 |
武器工业 | 511篇 |
无线电 | 4228篇 |
一般工业技术 | 4013篇 |
冶金工业 | 3475篇 |
原子能技术 | 487篇 |
自动化技术 | 5619篇 |
出版年
2024年 | 254篇 |
2023年 | 670篇 |
2022年 | 1667篇 |
2021年 | 2106篇 |
2020年 | 1486篇 |
2019年 | 1090篇 |
2018年 | 1182篇 |
2017年 | 1360篇 |
2016年 | 1210篇 |
2015年 | 1745篇 |
2014年 | 2213篇 |
2013年 | 2585篇 |
2012年 | 3041篇 |
2011年 | 3139篇 |
2010年 | 2989篇 |
2009年 | 2725篇 |
2008年 | 2720篇 |
2007年 | 2581篇 |
2006年 | 2246篇 |
2005年 | 1785篇 |
2004年 | 1266篇 |
2003年 | 920篇 |
2002年 | 817篇 |
2001年 | 843篇 |
2000年 | 603篇 |
1999年 | 391篇 |
1998年 | 788篇 |
1997年 | 554篇 |
1996年 | 384篇 |
1995年 | 225篇 |
1994年 | 183篇 |
1993年 | 183篇 |
1992年 | 78篇 |
1991年 | 64篇 |
1990年 | 74篇 |
1989年 | 65篇 |
1988年 | 50篇 |
1987年 | 49篇 |
1986年 | 32篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 23篇 |
1982年 | 23篇 |
1981年 | 45篇 |
1980年 | 33篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 46篇 |
1976年 | 70篇 |
1959年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A broadly cross-protective monoclonal antibody binding to Escherichia coli and Salmonella lipopolysaccharides 总被引:1,自引:0,他引:1
FE Di Padova H Brade GR Barclay IR Poxton E Liehl E Schuetze HP Kocher G Ramsay MH Schreier DB McClelland 《Canadian Metallurgical Quarterly》1993,61(9):3863-3872
During the last decade, episodes of sepsis have increased and Escherichia coli has remained the most frequent clinical isolate. Lipopolysaccharides (LPS; endotoxin) are the major toxic and antigenic components of gram-negative bacteria and qualify as targets for therapeutic interventions. Molecules that neutralize the toxic effects of LPS are actively investigated. In this paper, we describe a murine monoclonal antibody (MAb; WN1 222-5), broadly cross-reactive and cross-protective for smooth (S)-form and rough (R)-form LPS. As shown in enzyme-linked immunosorbent assay and the passive hemolysis assay, WN1 222-5 binds to the five known E. coli core chemotypes, to Salmonella core, and to S-form LPS having these core structures. In immunoblots, it is shown to react with both the nonsubstituted core LPS and with LPS carrying O-side chains, indicating the exposure of the epitope in both S-form and R-form LPS. This MAb of the immunoglobulin G2a class is not lipid A reactive but binds to E. coli J5, an RcP+ mutant which carries an inner core structure common to many members of the family Enterobacteriaceae. Phosphate groups present in the inner core contribute to the epitope but are not essential for the binding of WN1 222-5 to complete core LPS. Cross-reactivity for clinical bacterial isolates is broad. WN1 222-5 binds to all E. coli clinical isolates tested so far (79 blood isolates, 80 urinary isolates, and 21 fecal isolates) and to some Citrobacter, Enterobacter, and Klebsiella isolates. This pattern of reactivity indicates that its binding epitope is widespread among members of the Enterobacteriaceae. WN1 222-5 exhibits biologically relevant activities. In vitro, it inhibits the Limulus amoebocyte lysate assay activity of S-form and R-form LPS in a dose-dependent manner and it neutralizes the LPS-induced release of clinically relevant monokines (interleukin 6 and tumor necrosis factor). In vivo, WN1 222-5 blocks endotoxin-induced pyrogenicity in rabbits and lethality in galactosamine-sensitized mice. The discovery of WN1 222-5 settles the long-lasting controversy over the existence of anti-core LPS MAbs with both cross-reactive and cross-protective activity, opening new possibilities for the immunotherapy of sepsis caused by gram-negative bacteria. 相似文献
72.
太钢4号高炉喷煤站从1990年起采用MFD-Ⅲ型脉动反吹式布袋除尘器。这种除尘器采用脉动式反吹清灰设施,合理布置布袋间距,布袋支撑骨架及选用针呢材质的布袋,过滤面积大,反吹清灰效果好,设备运行平稳,除尘效率高达99.8%,排放浓度小于10mg/m^3,故障率低。 相似文献
73.
Shihong XU Pengshou XU Mingrong JI Xianming LIU Maosheng MA Jingsheng ZHU Yuheng ZHANG Structure Research Laboratory University of Science Technology of China Hefei ChinaZhenjia XU Institute of Semiconductor Academia Sinica Beijing China 《材料科学技术学报》1993,9(6):437-440
The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxidegrowth have been investigated by means of thermal desorption,work function,Auger electronspectroscopy and photoemission electron spectroscopy.The experimental data showed that therewas a new state,interface electron state,near the Fermi level after the deposition of Na atoms.It wasfound that the presence of Na always caused an increase of the oxygen initial uptake whereas thepromotion of Si oxide growth was observed only at the coverage of Na greater than 0.5 ML.A newmechanism of Na-promoted Si oxide growth is suggested in this paper. 相似文献
74.
VM Coiro AL Segre A Di Nola M Paci A Grottesi G Veglia A Ballio 《Canadian Metallurgical Quarterly》1998,257(2):449-456
Pseudomycin A is a cyclic lipodepsinonapeptide phytotoxin produced by a strain of the plant pathogenic bacterium Pseudomonas syringae. Like other members of this family of bacterial metabolites, it is characterised by a fatty acylated cyclic peptide with mixed chirality and lactonic closure. Several biological activities of Pseudomycin A are lower than those found for some of its congeners, a difference which might depend on the diverse number and distribution of charged residues in the peptide moiety. Hence, it was of interest to investigate its conformation in solution. After the complete interpretation of the two-dimensional NMR spectra, NOE data were obtained and the structure was determined by computer simulations, applying distance geometry and molecular dynamics procedures. The conformation of the large ring of Pseudomycin A in solution includes three rigid structural regions interrupted by three short flexible regions that act as hinges. The overall three-dimensional structure of the cyclic moiety is similar to that of previously studied bioactive lipodepsinonapeptides produced by other pseudomonads. 相似文献
75.
MG Tozzi-Ciancarelli C Di Massimo G Ascani A Corbacelli 《Canadian Metallurgical Quarterly》1998,18(2-3):151-156
A number of retinal proteins are phosphorylated by a variety of kinases, resulting in well-known regulatory effects. The identity and role of corresponding phosphatases is less clear. We simultaneously measured the activity of serine/ threonine protein phosphatases type 1, 2A and 2C in bovine retinae. The enzymes were classified according to substrate specificity, divalent cation requirement and the effect of phosphatase subtype-specific inhibitors. The total- and specific activity of phosphatase type 2A was prevalent. Type 2C was 10-fold less abundant. 80% of type 1 and 50% of type 2A and type 2C, respectively, were soluble. An economic purification scheme was developed. We demonstrated the presence of phosphatase isozymes 2Calpha and 2Cbeta in bovine rod outer segments by enzymatic analysis as well as immunological techniques. The results suggest a yet unknown role of phosphatase type 2C in phototransduction. On the other hand, the immense amount of protein phosphatases found to be soluble - therefore not associated with rod outer segment membranes - points towards participation of these enzymes in the process of visual transduction not considered thus far. 相似文献
76.
钢管内径光电检测装置 总被引:3,自引:0,他引:3
介绍了一种检测细长钢管内径的光电检测装置。该装置利用线阵CCD作传感器,采用8031单片机作为主控制。 相似文献
77.
78.
79.
80.