全文获取类型
收费全文 | 720篇 |
免费 | 50篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 222篇 |
金属工艺 | 9篇 |
机械仪表 | 17篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 37篇 |
轻工业 | 81篇 |
水利工程 | 5篇 |
石油天然气 | 4篇 |
无线电 | 48篇 |
一般工业技术 | 97篇 |
冶金工业 | 24篇 |
原子能技术 | 3篇 |
自动化技术 | 190篇 |
出版年
2023年 | 9篇 |
2022年 | 23篇 |
2021年 | 28篇 |
2020年 | 17篇 |
2019年 | 32篇 |
2018年 | 25篇 |
2017年 | 23篇 |
2016年 | 24篇 |
2015年 | 17篇 |
2014年 | 37篇 |
2013年 | 44篇 |
2012年 | 45篇 |
2011年 | 49篇 |
2010年 | 45篇 |
2009年 | 38篇 |
2008年 | 35篇 |
2007年 | 30篇 |
2006年 | 34篇 |
2005年 | 28篇 |
2004年 | 19篇 |
2003年 | 33篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 11篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有772条查询结果,搜索用时 15 毫秒
81.
Ernesto A. Heredia Zavoni Juan J. Bariola Bernales Julio Vargas Neumann Povindar K. Mehta 《Materials and Structures》1988,21(3):213-221
Mud plasters or soil stuccos are commonly used to protect adobe walls from water erosion. Due to drying shrinkage cracks and
high permeability, the commonly used soil stuccos are not durable. Stucco stabilizers such as Portland cement, lime and asphalt
are expensive. An experimental study undertaken to evaluate some of the locally available, inexpensive, stucco stabilizers
is reported here. Crack-resistant stucco compositions made with a cactus solution are described and techniques to make the
stucco surface impervious to water are discussed. The results of durability tests involving simulated rainfall on stucco panels,
and stucco applied to adobe walls, are presented. Recommendations for field practice are also given. 相似文献
82.
Ernesto H. Perea Emilio Mendez Clifton G. Fonstad 《Journal of Electronic Materials》1980,9(2):459-466
The electron effective mass in InuGa1−uPvAs1−v has been measured on seven samples lattice-matched to InP and evenly spaced in values of v between 0 and 1, using the temperature
dependence of the amplitude of the Shubnikov-de Haas oscillations at high magnetic fields. Values of the carrier concentrations,
Hall mobilities and Dingle temperatures measured on these samples are also reported.
Work sponsored in part by the National Science Foundation, Grant No. ENG 76-09586, and in part by International Telephone
and Telegraph Electro-Optical Products Division. Work done in part at the M.I.T. Francis Bitter National Magnet Laboratory.
Funded in part by the National Science Foundation under Grant No. DMR-76-80895. 相似文献
83.
Richard Le Heron Glen W. Atkinson Henry Teune Greg Mason Henk Voogd Brenda J. Moscove Patricia Gober Thomas A. Reiner Richard F. Curtis Stephen F. Seninger W. W. Hall Jr. John E. Keith M. Van Naelten R. W. Keyes John Huttman Robert B. Weeden Clarence G. Ray Steven E. Daniels F. Larry Leistritz Patrizia Spinetti Peter D. Beaulieu F. J. Potgieter David L. Barkley Charles A. Berry Jean E. Weber Wieslaw Rozlucki Jesse Burkhead John R. Ottensmann Noel D. Uri Erlet Cater J. Barry Riddell Ernesto Quintanilla John F. McDonald Jon R. Miller Stan Czamanski 《The Annals of Regional Science》1986,20(1):87-144
84.
85.
Incubation of native, reduced Clostridium pasteurianum ferredoxin with different metals gave a range of modifications in the electronic and EPR spectrum of the protein, or made the signals disappear. The reduced protein, isolated after incubation with different metals under identical conditions (50 microM protein, 1 mM metal, 1 h incubation) was found to contain amounts of foreign metals increasing with their thiophylicity, i.e. Cd2+ > Zn2+ > Co2+. Little, if any, incorporation was observed for Ni2+, Cu2+, Mn2+ or in the absence of reductant. The activity of substituted ferredoxins in a hydrogenase-coupled assay was proportional to the amount of residual iron, suggesting that the residual iron is present in a population of intact active molecules rather than in partially substituted clusters distributed among individual molecules. The cadmium-substituted ferredoxin did not contain iron, but contained eight cadmium atoms and six labile sulfide atoms/mol. Folding of the isolated, substituted proteins was investigated by CD and 1H-NMR. Both techniques showed retention of the main structural features of the protein upon metal substitution. The rate and extent of the substitution of iron by cadmium were essentially independent of pH, but were found to decrease with increasing ionic strength and to increase with the cadmium concentration. In the cadmium-substituted protein, cadmium was replaced by iron upon incubation with iron and mercaptoethanol in the absence of dithionite. In the presence of dithionite, cadmium was not replaced by iron upon incubation of the cadmium-substituted protein with excess iron and mercaptoethanol. In competition experiments, incubation of iron-containing ferredoxin with stoichiometric amounts of cadmium in the presence of dithionite and excess iron and mercaptoethanol resulted in quantifiable replacement of iron by cadmium. Therefore, substitution of iron by cadmium was only achieved under reducing conditions, and was only reversible in the absence of strong reductants. 相似文献
86.
Lindenthal Jacob J.; Amaranto Ernesto A.; Jordan Theresa J.; Wepman Barry J. 《Canadian Metallurgical Quarterly》1984,31(4):572
Investigated orientations toward confidentiality of 59 mental health practitioners in US medical schools who were requested to respond to 10 case vignettes representing a range of students' problems by indicating the action they would take. Results suggest that Ss were generally unwilling to break confidentiality in response to cluster of presenting problems that involved suicidal tendencies, sexual coercion/seduction, nonviolent social transgressions, and falsifying data. This was most pronounced when risk of suicide was evident. Only a bomb threat scenario clearly elicited responses suggesting a likely breach of confidence. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
87.
Main‐chain copolybibenzoates with flexible spacers bearing thioether and ether groups were obtained by melt‐transesterification of diethyl 1,1′‐biphenyl‐4,4′‐dicarboxylate and β‐thioether glycols (thiodiethylene glycol or thiotriethylene glycol), using titanium (IV) isopropoxide as catalyst. A side‐reaction of etherification occurred simultaneously with the polycondensation reaction, resulting in the formation of comonomer units with the structure of the dimer of the glycol. This side‐reaction was confirmed by the preparation of model compounds. The most probable mechanism for this etherification reaction is the formation of an intermediate three‐membered cyclic sulfonium ion by neighbouring sulfur participation. The thermal and X‐ray characterization of the synthesised copolymers indicated that a smectic mesophase was rapidly obtained on cooling the copolymers derived from thiodiethylene glycol from the melt and this phase was transformed slowly into a more ordered structure. In contrast, copolymers derived from thiotriethylene glycol did not exhibit liquid‐crystalline phases and their crystallisation from the isotropic melt was very fast. It was found that the copolymerization increased the mesophase stability. Finally, the results obtained were compared with those of corresponding homopolybibenzoates with methylene or oxymethylene spacers. Copyright © 2005 Society of Chemical Industry 相似文献
88.
Summary Samples of poly(ethylene terephthalate) (PET), poly(ethylene terephthalate-co-naphthalene-2,6-dicarboxylate) (PENT) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN), materials which find application in textile and packaging industry, have been investigated, with the aim to obtain narrow molecular weight fractions suitable for further characterization. Preliminary results concerning with the fractionation of gram-quantities of the polyesters are reported, using a method based on the fractional precipitation from a phenol/1,2,4-thrichlorobenzene solution of the polymer, using n-heptane as non-solvent. Obtained fractions have been characterized by intrinsic viscosity measurements and Gel Permeation Chromatography analysis. 相似文献
89.
Hugo Ernesto Eguez Eung Ha Cho 《JOM Journal of the Minerals, Metals and Materials Society》1987,39(7):38-41
This study explores the adsorption behavior of As(III) and As(V) on activated charcoal under the various conditions of solution pH and temperature. The adsorption loading of As(III) remains constant in the pH range from 0.16 to 3.5, while that of As(V) shows a maximum value at pH2.35 when the pH varies from 0.86 to 6.33. The isosteric heat of adsorption for As(III) varies from 4 to 0.75 Kcal/mole and that for As(V), from 4 to 2 Kcal/mole with varying surface loading. The magnitude of these values suggests that the adsorption of arsenic is by physisorption and due to weak forces such as Van der Waals forces. Activated charcoal adsorbs As(V) by 2.5% of its own weight while it absorbs As(III) by 1.2% of its own weight when the equilibrium concentration of each species is 22 × 10?2 molar. Since arsenic has appreciable adsorbability on activated charcoal, this adsorbent may be a viable candidate to be used for removing arsenic from solution. Further studies to determine more information on the selectivity of arsenic over other valuable metal ions and the ones to determine the effects of other cations such as, ferric, calcium, and magnesium ions are suggested as a next step. 相似文献
90.
The authors study the switching network structures with emphasis on the information theory aspects of the problem (definition of combinatorial power and complexity). Different routing rules and rearranging algorithms are surveyed. Finally, a numerical simulation points out the extensivity concept which is useful in the study of switching networks models of reduced size. 相似文献