全文获取类型
收费全文 | 1157篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 21篇 |
综合类 | 4篇 |
化学工业 | 129篇 |
金属工艺 | 28篇 |
机械仪表 | 13篇 |
建筑科学 | 46篇 |
矿业工程 | 1篇 |
能源动力 | 12篇 |
轻工业 | 516篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
无线电 | 35篇 |
一般工业技术 | 196篇 |
冶金工业 | 80篇 |
原子能技术 | 24篇 |
自动化技术 | 57篇 |
出版年
2018年 | 17篇 |
2014年 | 13篇 |
2013年 | 36篇 |
2012年 | 16篇 |
2011年 | 28篇 |
2010年 | 13篇 |
2009年 | 13篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 17篇 |
2005年 | 24篇 |
2004年 | 18篇 |
2003年 | 26篇 |
2002年 | 18篇 |
2001年 | 11篇 |
1998年 | 29篇 |
1997年 | 23篇 |
1996年 | 22篇 |
1995年 | 21篇 |
1994年 | 20篇 |
1993年 | 17篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 21篇 |
1978年 | 16篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1975年 | 12篇 |
1974年 | 17篇 |
1973年 | 14篇 |
1970年 | 11篇 |
1941年 | 20篇 |
1940年 | 17篇 |
1939年 | 22篇 |
1938年 | 10篇 |
1911年 | 10篇 |
1908年 | 17篇 |
1907年 | 12篇 |
1906年 | 34篇 |
1905年 | 29篇 |
1904年 | 13篇 |
1903年 | 20篇 |
排序方式: 共有1166条查询结果,搜索用时 15 毫秒
1.
S. Klages M. Schöck C. Sürgers H. v. Löhneysen 《Journal of Low Temperature Physics》2004,137(3-4):509-522
The morphology and electronic transport of ultrathin Au films with thicknesses d = 1 ? 5 monolayers (ML) deposited on Si(111)7 × 7 surfaces is investigated by in situ scanning tunneling microscopy and electrical resistance measurements for temperatures T = 2 ? 300 K. With decreasing film thickness, i.e. decreasing sheet conductance Gs, a transition from a weakly conducting regime described by a logarithmic temperature dependence to an insulating regime occurs. In the insulating regime, the temperature dependence is described by Gs ∝ exp[?(T 0 /T) n] with an exponent n which gradually changes from 0.69 to 1 with decreasing film thickness. In contrast, for the Si(111)6 × 6-Au reconstruction obtained after annealing, an exponent n = 1/2 is found suggesting the formation of a soft Coulomb gap due to electron-electron interaction. PACS numbers: 68.37.-d, 68.55.-a, 73.50.-h, 73.25.+i, 81.15.-z 相似文献
2.
RJ Wilkinson K Hasl?v R Rappuoli F Giovannoni PR Narayanan CR Desai HM Vordermeier J Paulsen G Pasvol J Ivanyi M Singh 《Canadian Metallurgical Quarterly》1997,35(3):553-557
The diagnosis of infection caused by Mycobacterium tuberculosis is of increased public health concern following increases in the number of cases in developed countries and major increases in developing countries associated with the spread of human immunodeficiency virus (HIV) infection. The specificity of purified protein derivative skin testing for the detection of infection is compromised by exposure to environmental mycobacteria. Examination of sputum detects the most infectious patients, but not those with extrapulmonary disease. The 38-kDa antigen of M. tuberculosis contains two M. tuberculosis-specific B-cell epitopes. We overexpressed the gene for this antigen in Escherichia coli and evaluated the recombinant product in in vitro assays of T-cell function and as a target for the antibody response in humans. The sensitivity and specificity of the antigen as a skin test reagent were also assessed in outbred guinea pigs. We found that 69% of healthy sensitized humans recognize the antigen in vitro, as manifested by both cell proliferation and the production of gamma interferon. Untreated patients initially have a lower frequency of response (38%); this recovers to 72% during therapy. A total of 292 patients (20 with HIV coinfection) and 58 controls were examined for production of antibody to the 38-kDa antigen by using a commercially available kit. The sensitivity of the test in comparison with that of culture was 72.6%, and the specificity was 94.9%. The antigen was also tested for its ability to induce skin reactions in outbred guinea pigs sensitized by various mycobacterial species. The antigen provoked significant skin reactions in M. tuberculosis-, M. bovis BCG-, and M. intracellulare-sensitized animals. The significance of these findings and the usefulness of this antigen in immunodiagnosis are discussed. 相似文献
3.
W. Nierle W. Feldheim H. G. Maier P. Schreier W. Grosch G. -W. v. Rymon Lipinski H. -P. Thier W. Feldheim W. Seibel J. Buchberger E. Schlimme G. Engel U. Sacher F. Siewek R. Frommberger R. Frommberger G. -W. v. Rymon Lipinski F. I. Schäfers F. I. Schäfers R. Matissek H. Klostermeyer F. Kiermeier H. -P. Thier M. Miller M. Miller H. Wieczorek F. Jekat W. Feldheim K. Eichner M. Petz D. Gottschalk und W. Nierle 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1987,185(2):134-144
4.
5.
A new analytical method has been developed for the determination of the reactive lysine content of soya bean protein. The method is based on the reaction of the free basic groups of the protein with 1-phenylazo-2 naphthol-6,8 disulphonic acid. With regard to the stoichiometry of the procedure, it has been proved, contrary to earlier reports, that the basic amino acids, histidine, arginine and lysine, each combine with one mole of the dye. After acylation with propionic anhydride lysine alone loses its dye reactivity. The usefulness of the proposed method has been demonstrated by the determination of the reactive lysine content of several untreated, heat-treated and acid-treated soya bean samples. The results show that heat damage of about 5% in reactive lysine content can be measured in 1·5 h with good reproducibility. 相似文献
6.
7.
8.
James?Eves Vassili?V.?ToropovEmail author Harvey?M.?Thompson Nik?Kapur Jian?Fan Daniel?Copley Adrian?Mincher 《Structural and Multidisciplinary Optimization》2012,45(5):739-745
Supersonic jet pumps are simple devices with no moving parts, where a high velocity (primary) flow is used to pump a second
fluid. In this paper, Computational Fluid Dynamics (CFD) is combined with an optimization framework in order to develop a
tool for the rapid generation of jet pump designs. A key feature of the problem formulation is the transformation of the jet
pump design parameters in terms of geometric ratios. This approach dramatically reduces the number of unrealistic designs
covered by the Design of Experiments. Optimal Latin Hypercubes for surrogate model building and model validation points are
constructed using a permutation genetic algorithm and design points are evaluated using CFD. Surrogate models of primary and
entrained flow rates are built using a Moving Least Squares approach. A series of optimizations for various pump sizes are
performed using a genetic algorithm and Sequential Quadratic Programming, with responses calculated from the surrogates. This
approach results in a set of optimized designs, from which pumps for a wide range of flow rates can be interpolated. 相似文献
9.
K. Siegert P. Unseld J. Baur F. Kauffmann E. Arzt K.v. Niessen 《International Journal of Machine Tools and Manufacture》2006,46(11):1227-1232
High strength in combination with low density is the key features for lightweight constructions in automotive and aerospace applications. Tailor-made fiber reinforcements in light-metal matrices could help to achieve this goal. However, the integration of fibers with conventional casting-route manufacturing techniques like squeeze casting or diffusion bonding restricts the component geometry and results in elevated process cost due to long cycle times and the need of additional fiber coatings. In the center of competence for casting and thixoforging Stuttgart (CCT), new processes for manufacturing metal matrix composites are developed. Long-fiber reinforced Al–Si alloys and components are produced by thixoforging of laminates made of alternating metal matrix layers and carbon fiber fabrics. This paper illustrates the manufacturing technology and first experimental results with special focus on fiber penetration and infiltration behavior and also on the formation of fiber-matrix interface to analyze fiber damage by mechanical or chemical attack. 相似文献
10.
Summary The effect of tert-butyl chloride in the polymerizations of isobutylene carried out in the presence of SnCl4 in dichloromethane at temperatures-20°C and-78°C was investigated. Synthesized polyisobutylene samples showed a bimodal molecular
weight distribution (MWD) and it was found that the weight content of the lowermolecular weight (LMW) fraction increased with
increasing t-BuCl concentration in the polymerization mixture. The effect of ageing of the initiation mixture t-BuCl/SnCl4 in CH2Cl2 prepared in advance on MWD of the PIB samples was also studied. Ageing of the initiation system supports the formation of
the LMW fraction and this oily PIB is the only product of the polymerization at-20°C,
. 相似文献