全文获取类型
收费全文 | 168691篇 |
免费 | 1180篇 |
国内免费 | 205篇 |
专业分类
电工技术 | 2555篇 |
综合类 | 121篇 |
化学工业 | 26653篇 |
金属工艺 | 9482篇 |
机械仪表 | 5717篇 |
建筑科学 | 3012篇 |
矿业工程 | 1887篇 |
能源动力 | 2714篇 |
轻工业 | 8820篇 |
水利工程 | 2731篇 |
石油天然气 | 8692篇 |
武器工业 | 12篇 |
无线电 | 14510篇 |
一般工业技术 | 38305篇 |
冶金工业 | 27818篇 |
原子能技术 | 6950篇 |
自动化技术 | 10097篇 |
出版年
2018年 | 2981篇 |
2017年 | 3093篇 |
2016年 | 3345篇 |
2015年 | 1675篇 |
2014年 | 2959篇 |
2013年 | 6342篇 |
2012年 | 4316篇 |
2011年 | 5406篇 |
2010年 | 4432篇 |
2009年 | 4904篇 |
2008年 | 4953篇 |
2007年 | 4878篇 |
2006年 | 4145篇 |
2005年 | 3829篇 |
2004年 | 3637篇 |
2003年 | 3523篇 |
2002年 | 3452篇 |
2001年 | 3467篇 |
2000年 | 3366篇 |
1999年 | 3217篇 |
1998年 | 7032篇 |
1997年 | 5151篇 |
1996年 | 3830篇 |
1995年 | 2920篇 |
1994年 | 2599篇 |
1993年 | 2721篇 |
1992年 | 2256篇 |
1991年 | 2308篇 |
1990年 | 2416篇 |
1989年 | 2318篇 |
1988年 | 2316篇 |
1987年 | 2192篇 |
1986年 | 2248篇 |
1985年 | 2294篇 |
1984年 | 2209篇 |
1983年 | 2136篇 |
1982年 | 1980篇 |
1981年 | 2195篇 |
1980年 | 2054篇 |
1979年 | 2270篇 |
1978年 | 2432篇 |
1977年 | 2430篇 |
1976年 | 3096篇 |
1975年 | 2244篇 |
1974年 | 2307篇 |
1973年 | 2342篇 |
1972年 | 2155篇 |
1971年 | 1911篇 |
1970年 | 1701篇 |
1969年 | 1632篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
85.
I Berent 《Canadian Metallurgical Quarterly》1997,23(6):1727-1742
The contribution of assembled phonology in reading English was examined in the lexical decision task by comparing two markers: regularity effects and phonological priming. Strategic control was assessed by manipulating the phonological lexicality of the foils: Experiment 1 used legal nonwords, whereas Experiment 2 used pseudohomophones. Replicating existing findings, null regularity effects were obtained in the presence of legal nonwords. Modest regularity effects, in accuracy only, were observed with pseudohomophone foils. In contrast, phonological priming effects emerged in each of the experiments, regardless of the presence of regularity effects. Assembled phonology thus constrains reading under conditions that strongly discourage its use. However, regularity effects are not necessary evidence for its presence. The dissociation of regularity and phonological priming effects is discussed in terms of the two-cycles model. 相似文献
86.
M Huttova I Hartmanova K Kralinsky J Filka J Uher J Kurak S Krizan V Krcmery 《Canadian Metallurgical Quarterly》1998,17(11):1012-1015
PURPOSE OF THE STUDY: To assess efficacy and safety of fluconazole in neonates with Candida fungemia. STUDY DESIGN: Multicenter prospective protocol of all fungemias appearing between January 1, 1993, and December 31, 1997, in four major university hospitals. RESULTS: Forty neonates, 28 of them with very low birth weight (<1500 g; 30.5 median gestation week), with documented Candida albicans fungemia were treated with intravenous fluconazole in a daily dosage of 6 mg/kg once daily for 6 to 48 days. Thirty-four received fluconazole as monotherapy and 6 received it in combination with amphotericin B. Thirty-two (80%) were cured; 4 of them relapsed despite at least 14 days of therapy, but they were ultimately cured without sequelae. Eight other neonates died, 4 because of fungal infection and 4 because of prematurity or hemorrhage or lung failure, with fungemia (20% overall and 10% attributable mortality). Two neonates had elevated liver enzymes during fluconazole therapy and 2 others had elevated serum creatinine during fluconazole monotherapy. In none of them did these abnormalities necessitate discontinuation of antifungal therapy. In 8 neonates fungal meningitis developed as a complication of fungemia. All but 3 fungemias were C. albicans; 3 were Candida parapsilosis. CONCLUSIONS: Fluconazole was safe and effective antifungal therapy even in complicated or Candida fungemia in neonates and in infants with very low birth weight. 相似文献
87.
Ku T.K. Chen S.H. Yang C.D. She N.J. Wang C.C. Chen C.F. Hsieh I.J. Cheng H.C. 《Electron Device Letters, IEEE》1996,17(5):208-210
Undoped and phosphorus (P)-doped diamond-clad Si field emitter arrays have been successfully fabricated using microwave plasma chemical vapor deposition (MPCVD) technology. The electron emission from the blunt diamond-clad microtips are much higher than those for the pure Si tips with sharp curvature due to a lower work function. Furthermore, the characteristics of emission current against applied voltage for the P-doped diamond-clad tips show superior emission at lower field to the undoped ones. After the examination of Auger electron spectroscopy (AES) and electrical characteristics of as-grown diamond, such a significant enhancement of the electron emission from the P-doped diamond-clad tips is attributed to a higher electron conductivity and defect densities 相似文献
88.
This paper provides a preliminary examination of present and projected land use in Africa to estimate the potential availability of land in 2025 for use in producing biomass energy. Fifty countries are included in the analysis. Future cropland requirements are projected on the basis of average African cereal crop yield improvements since 1972, and minimum nutritional requirements are assumed to be met in 2025 without increasing imports above present absolute levels. Cropland, natural forests and other wilderness areas are excluded from consideration for biomass energy use. Woody biomass energy yields are estimated on the basis of nationally averaged precipitation, using a yield-precipitation correlation for commercial eucalyptus plantations in Brazil. The total African bioenergy production potential in 2025 is estimated to be about 18 EJ per year for a set of baseline assumptions that includes planting only 10% of the available non-crop, non-forest, non-wilderness area with biomass energy crops. A preliminary cost assessment suggests that much of this biomass could be produced for $1–2 GJ−1. A number of uncertainties in the modelling assumptions are examined through a sensitivity analysis. Despite limitations in the model used here, one robust conclusion is that Africa as a whole has a significant biophysical potential for producing biomass energy. This result suggests that more detailed country and sub-country level assessments would be worthwhile to understand better the practical prospects for future biomass energy production in Africa. 相似文献
89.
A. M. Rabasco I. Caraballo M. Fern ndez-Ar valo 《Drug development and industrial pharmacy》1993,19(14):1673-1691
A high-performance liquid chromatographic (HPLC) assay has been developed for thimerosal and some of its degradation products: thiosalicylic and 2,2'-dithiosalicylic acids. Using this method, the influence of formulation factors as: isotonic agent, initial concentration, addition of tromethamine, pH and container material, over thimerosal stability was studied. 相似文献
90.
The development and creating of new-generation full-scope simulator and new technology of simulation
N. N. Ponomarev-Stepnoi V. A. Lebedev M. M. Khudiykov S. D. Malkin V. V. Shalia I. D. Rakitin 《Nuclear Engineering and Design》1997,173(1-3)
Set out is a brief account of the two major accomplishments by the Russian Research Center ‘Kurchatov Institute’ in creating the full-scope simulators and mathematical modeling technologies. Presented are the basic specifications of one of the world's largest simulators—the full-scope simulator for the Leningrad NPP which is the new-generation one. Owing to the extended modeling scope accomplished is the possibility of training personnel to act in terms of not only the design-basis but rather beyond the design-basis accidents. To minimize the expenditures for creating the simulators, analyzers and other modeling and control means, the RRC ‘Kurchatov Institute' has created the unique technology of mathmodeling automation. Thanks to its versatility and application at its creation of the ELUD philosophy (easy to learn, use and develop) good use is made of this technology both in nuclear and thermal power engineering, as well as in gas industry. 相似文献