全文获取类型
收费全文 | 1684篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 24篇 |
化学工业 | 379篇 |
金属工艺 | 25篇 |
机械仪表 | 30篇 |
建筑科学 | 59篇 |
矿业工程 | 8篇 |
能源动力 | 28篇 |
轻工业 | 125篇 |
水利工程 | 7篇 |
石油天然气 | 5篇 |
无线电 | 92篇 |
一般工业技术 | 201篇 |
冶金工业 | 489篇 |
原子能技术 | 29篇 |
自动化技术 | 211篇 |
出版年
2022年 | 15篇 |
2021年 | 26篇 |
2017年 | 16篇 |
2016年 | 24篇 |
2014年 | 27篇 |
2013年 | 100篇 |
2012年 | 28篇 |
2011年 | 53篇 |
2010年 | 35篇 |
2009年 | 49篇 |
2008年 | 55篇 |
2007年 | 60篇 |
2006年 | 47篇 |
2005年 | 39篇 |
2004年 | 42篇 |
2003年 | 33篇 |
2002年 | 37篇 |
2001年 | 20篇 |
2000年 | 25篇 |
1999年 | 22篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 29篇 |
1995年 | 20篇 |
1994年 | 22篇 |
1993年 | 27篇 |
1992年 | 25篇 |
1991年 | 17篇 |
1990年 | 30篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 28篇 |
1986年 | 29篇 |
1985年 | 38篇 |
1984年 | 30篇 |
1983年 | 26篇 |
1982年 | 33篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 30篇 |
1978年 | 28篇 |
1977年 | 27篇 |
1976年 | 33篇 |
1975年 | 20篇 |
1974年 | 26篇 |
1973年 | 34篇 |
1972年 | 20篇 |
1970年 | 16篇 |
1969年 | 14篇 |
1958年 | 14篇 |
排序方式: 共有1712条查询结果,搜索用时 0 毫秒
51.
Proposes that the moral evaluation process is, in part, based on reality and achievement evaluations. This proposition is suggested by certain similarities found between moral evaluations and the other 2 types. Implications are drawn regarding (a) dilemmas and conflicts in moral evaluation which arise from its dual foundations; (b) the different kinds of morality that evolve depending upon which more primary evaluative system becomes predominant; and (c) the susceptibility of moral evaluations to contamination by reality and achievement evaluations. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
52.
Robertshaw C. Stuart; Kelly Thomas J.; Hiebert Harold D. 《Canadian Metallurgical Quarterly》1973,41(3):459
Describes the case of a withdrawn adolescent male outpatient at a mental health clinic who was instructed to record his own verbal behavior. Consequences were implemented to increase the frequency of verbal responses. S "earned" his way out of the clinic by increasing his verbal behavior to an established criterion performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
53.
Williams Jack D.; Dudley Harold K.; Overall John E. 《Canadian Metallurgical Quarterly》1972,80(3):261
Administered the MMPI and 16 PF to 201 15-60 yr. old new admissions to a state mental hospital. Correlations between the 2 sets of scale scores were examined directly and by factor analysis. 3 common factors appeared to be represented to some extent in both instruments. The 16 PF appeared weak in the measurement of the more serious kinds of psychopathology, and had strongest loadings in a common factor identified with the validity scales of the MMPI. The 16 PF was found to measure 3 higher-order factors of personality not represented in the MMPI, but they do not appear highly relevant for assessment in a disturbed mental hospital population. Numerous significant relationships to psychiatrically relevant background variables were identified in analyses of profiles derived from both instruments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
Studied the magnitude and stability of individual differences in the amount of time required to achieve a criterion level of performance (time-to-criterion). Time-to-criterion was defined by (a) the amount of elapsed time and (b) the amount of on-task time required to attain the criterion. 90 8th graders were randomly assigned either to a mastery learning class in which all Ss were helped to attain an 85% mastery standard or to 1 of 2 nonmastery classes. Ss learned a 3-unit sequence of programmed material in matrix arithmetic. Results from the 82 Ss who completed the study indicate that time-to-criterion (defined in both manners) was an alterable human characteristic. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
Harold Margolin 《Metallurgical and Materials Transactions A》1982,13(12):2191-2195
The role of microstructure in affecting fracture toughness is examined by considering how microstructure affects the formation of a critical increment of crack extension leading to catastrophic fracture. It is proposed that this critical increment of crack extension occurs by void formation ahead of the main crack and growth back to it. Factors affecting void nucleation and void growth are, therefore, examined in this connection. Published data on the Ti-5.25Al-5.5V-0.9Fe-0.5Cu alloy are used for this purpose. In equiaxed(E) α structure voids nucleate at Eα/agedβ matrix interfaces for both tensile and fracture toughness tests. Although the interparticle spacing, A, is four times more effective than priorβ grain size,D β, in controlling void growth rate,G L, in a tensile test,D β is at least five times more effective in controlling fracture toughness. For Widmanstätten plus grain boundary (W + GB) α structures there are marked similarities betweenG Lbehavior as a function of GBa thickness, J, and the contribution of J to fracture toughness. These similarities have led to the proposal that the increase in fracture toughness, ΔKQ, with increasingl is due to blunting of the crack tip, and the plateau in ΔKQ which follows, with increasingl, is due to a balance between blunting and sharpening processes. Blunting occurs by crack penetration into GBα. The sharpening occurs by void formation and growth along GBα/agedβ interfaces back to the main crack. 相似文献
56.
Presents general criteria for observation room windows. Various glazing materials available for proper lighting and the typical transmission and reflection characteristics of each, acoustical factors relating to sound control, and general design considerations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
58.
Morris Young Ernest Levine Harold Margolin 《Metallurgical and Materials Transactions B》1974,5(8):1891-1898
In Ti-6-2-4-6 alloys, beta transforms to orthorhombic martensite when quenched from a temperature of 1188 or above, X-ray
analysis showed that aging at 773 or 873 gradually reduces the degree of orthorhombicity until a hexagonal structure equivalent
to alpha, but having the morphological characteristics of the prior martensite, is produced. The orthorhombicity is reduced
by solute rejection to beta which forms as particles both homogeneously and heterogeneously within the martensitic structure.
The structure at maximum hardness is a fine distribution of Burger’s oriented beta particles in a matrix of martensite of
greatly reduced orthorhombicity. Overaging appears to occur as a result of coarsening of the homogeneous beta particles. It
is shown that aging at temperatures from 873 to 1083 K results in growth of one particular varient of the beta which is located
at the interface between twin related regions composing a martensite lath. This beta along with similarly oriented beta at
lath interfaces forms a continuous beta matrix by a gradual growth process. It is shown that this matrix has the identical
orientation and shape of the original beta grain prior to quenching. A mechanism is proposed to account for this “memory effect”. 相似文献
59.
Antioxidant additives in polyethylene films have been shown to diffuse to the surface where they are subsequently lost, exposing the polymer to oxidation. Compatibility of antioxidants with polyethylene may be increased by use of silane coupling agents. In this study, three approaches to antioxidant modification are examined: (1) bonding antioxidant directly to silicon, (2) coupling the silane to an antioxidant hydroxyl function, and (3) dissolving antioxidants in silanes. All three approaches are shown to be effective in reducing antioxidant loss by diffusion. 相似文献
60.
Automobile catalyst emissions have resulted in the occurrence of elevated Pt, Pd, and Rh concentration in the urban and roadside environment. We investigate the chronology of platinum group elements (PGE) accumulation in dated sediments from an urban lake near Boston, MA. Chronological profiles demonstrate that Pt, Pd, and Rh concentrations increased following the introduction in catalysts with accumulation rates 6-16 times larger in 1992-2002 than prior to the introduction of catalysts. Ratios of these elements closely match their ratios in catalysts, providing further evidence of an automobile source. Iridium and Ru accumulation in sediments also increased following the introduction of catalysts, and while past Os contamination is associated with leather tanning, recent changes in the isotopic composition of Os indicate another anthropogenic source for this element. The PGE have similar geochemical properties and are difficult to separate from one another, and therefore, we suggest that automobile catalyst emissions also result in increasing environmental concentrations of Ir, Ru, and Os, which occur as impurities in catalysts. An automobile catalyst source of Ir and Os is supported by elevated concentrations of these elements in a tunnel dust sample. 相似文献