全文获取类型
收费全文 | 80048篇 |
免费 | 7052篇 |
国内免费 | 3707篇 |
专业分类
电工技术 | 4393篇 |
技术理论 | 3篇 |
综合类 | 4977篇 |
化学工业 | 13224篇 |
金属工艺 | 4714篇 |
机械仪表 | 4910篇 |
建筑科学 | 5726篇 |
矿业工程 | 2429篇 |
能源动力 | 2185篇 |
轻工业 | 5610篇 |
水利工程 | 1407篇 |
石油天然气 | 4461篇 |
武器工业 | 629篇 |
无线电 | 9340篇 |
一般工业技术 | 9900篇 |
冶金工业 | 4918篇 |
原子能技术 | 803篇 |
自动化技术 | 11178篇 |
出版年
2024年 | 451篇 |
2023年 | 1434篇 |
2022年 | 2558篇 |
2021年 | 3509篇 |
2020年 | 2602篇 |
2019年 | 2234篇 |
2018年 | 2434篇 |
2017年 | 2742篇 |
2016年 | 2456篇 |
2015年 | 3171篇 |
2014年 | 3924篇 |
2013年 | 4641篇 |
2012年 | 5162篇 |
2011年 | 5641篇 |
2010年 | 4661篇 |
2009年 | 4467篇 |
2008年 | 4265篇 |
2007年 | 4081篇 |
2006年 | 4381篇 |
2005年 | 3618篇 |
2004年 | 2532篇 |
2003年 | 2138篇 |
2002年 | 1917篇 |
2001年 | 1749篇 |
2000年 | 1798篇 |
1999年 | 1949篇 |
1998年 | 2006篇 |
1997年 | 1640篇 |
1996年 | 1401篇 |
1995年 | 1115篇 |
1994年 | 967篇 |
1993年 | 697篇 |
1992年 | 483篇 |
1991年 | 404篇 |
1990年 | 315篇 |
1989年 | 252篇 |
1988年 | 215篇 |
1987年 | 154篇 |
1986年 | 120篇 |
1985年 | 87篇 |
1984年 | 54篇 |
1983年 | 39篇 |
1982年 | 46篇 |
1981年 | 56篇 |
1980年 | 42篇 |
1979年 | 24篇 |
1978年 | 20篇 |
1977年 | 33篇 |
1976年 | 46篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
介绍了一种采用改进型的CLS3700数控测井系统对微电阻率扫描仪数据采集与控制接口的设计及实现方法。基于CLS3700数控测井仪和FMS仪采用89C51单片机设计出通信接口,解决了微电阻率方法。基于CLS3700数控测井仪和FMS仪采用89C51单片机设备出通信接口电路,解决了微电阻主扫描仪现现场实时处理中的瓶颈问题。 相似文献
62.
基于可寻址分支分配器的CATV收费系统 总被引:2,自引:1,他引:1
给出了一种基于可寻址分支分配器的CATV收费管理系统设计方案,并着重介绍了系统的工作原理及可寻址分支分配器的设计。 相似文献
63.
64.
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
65.
66.
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
67.
Z Ma S Ramanadham K Kempe Z Hu J Ladenson J Turk 《Canadian Metallurgical Quarterly》1996,1308(2):151-163
We prepared polymers having a phospholipid polar group, poly [omega-methacryloyloxyalkyl phosphorylcholine (MAPC)-co-n-butyl methacrylate(BMA)], as new biomedical materials and evaluated their blood compatibility with attention to protein adsorption and platelet adhesion. The total amount of proteins adsorbed on the polymer surface from human plasma was determined, and the distribution of adsorbed proteins on the plasma-contacting surface was analyzed. The amount of proteins adsorbed on every poly (MAPC-co-BMA) was small compared with that observed on polymers without the phospholipid polar group. However, there was no significant difference in the amount of adsorbed proteins on the poly(MAPC-co-BMA) even when the methylene chain length between the phospholipid polar group and the backbone in the MAPC moiety was altered. Platelet adhesion on the polymer surface from a platelet suspension in a buffered solution was evaluated with and without plasma treatment on the surface. When a rabbit platelet suspension was brought into contact with the poly(BMA) surface after treatment with plasma, many platelets adhered and aggregated. However, a reduced amount of platelet adhered on the poly(BMA) was found in the case of direct contact with the platelet suspension. On the other hand, the poly(MAPC-co-BMA)s could inhibit platelet adhesion under both conditions. Based on these results, it can be concluded that the proteins adsorbed on the surface play an important role in determining the platelet adhesion and suppression of the protein adsorption on the surface, which is one of the most significant ways of inhibiting platelet adhesion. 相似文献
68.
Q Hu M Trevisan Y Xu W Dong SA Berger SD Lyman MD Minden 《Canadian Metallurgical Quarterly》1995,95(6):2530-2538
The growth of human leukemic cells in culture and in vivo is dependent upon the presence of hematopoietic growth factors. Most populations of human leukemic acute myeloblastic leukemia (AML) cells express c-Kit on their surface and respond to Kit ligand (KL) in culture. To determine if this interaction was of potential significance in vivo we used a mouse model system. 32D cells, a murine IL-3-dependent myeloid cell line, were rendered KL responsive by transfection of the murine c-Kit. After injection of 32D or 32D-Kit cells into syngeneic hosts, animals bearing 32D-Kit cells, but not 32D cells, became moribund and were killed. These animals had circulating leukemic blast cells, infiltration of bone marrow, spleen, brain, liver, lung, and kidney. Cells recovered from some of the animals continued to be dependent upon IL-3 or KL for growth while in other cases the cells were factor independent. This model illustrates that the constitutive expression of c-Kit enhances the leukemic potential of 32D cells. The model will be useful for studying the progression of leukemia in vivo and testing whether interruption of the interaction of Kit and KL can affect the growth of leukemic cells. 相似文献
69.
70.