全文获取类型
收费全文 | 36333篇 |
免费 | 1301篇 |
国内免费 | 63篇 |
专业分类
电工技术 | 371篇 |
综合类 | 29篇 |
化学工业 | 7237篇 |
金属工艺 | 725篇 |
机械仪表 | 738篇 |
建筑科学 | 1966篇 |
矿业工程 | 114篇 |
能源动力 | 1054篇 |
轻工业 | 2883篇 |
水利工程 | 430篇 |
石油天然气 | 117篇 |
武器工业 | 5篇 |
无线电 | 2475篇 |
一般工业技术 | 6113篇 |
冶金工业 | 6598篇 |
原子能技术 | 268篇 |
自动化技术 | 6574篇 |
出版年
2023年 | 214篇 |
2022年 | 440篇 |
2021年 | 683篇 |
2020年 | 463篇 |
2019年 | 617篇 |
2018年 | 780篇 |
2017年 | 695篇 |
2016年 | 834篇 |
2015年 | 757篇 |
2014年 | 1041篇 |
2013年 | 2372篇 |
2012年 | 1680篇 |
2011年 | 2091篇 |
2010年 | 1651篇 |
2009年 | 1547篇 |
2008年 | 1800篇 |
2007年 | 1774篇 |
2006年 | 1591篇 |
2005年 | 1439篇 |
2004年 | 1174篇 |
2003年 | 1122篇 |
2002年 | 1051篇 |
2001年 | 702篇 |
2000年 | 549篇 |
1999年 | 595篇 |
1998年 | 584篇 |
1997年 | 574篇 |
1996年 | 549篇 |
1995年 | 572篇 |
1994年 | 525篇 |
1993年 | 510篇 |
1992年 | 500篇 |
1991年 | 288篇 |
1990年 | 418篇 |
1989年 | 389篇 |
1988年 | 319篇 |
1987年 | 355篇 |
1986年 | 310篇 |
1985年 | 418篇 |
1984年 | 416篇 |
1983年 | 318篇 |
1982年 | 295篇 |
1981年 | 281篇 |
1980年 | 269篇 |
1979年 | 270篇 |
1978年 | 247篇 |
1977年 | 225篇 |
1976年 | 206篇 |
1975年 | 194篇 |
1974年 | 173篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
111.
David L. Spooner 《Journal of Intelligent Manufacturing》1994,5(1):13-21
A product database for a design and manufacturing enterprise serves as a repository for the data needed to manufacture a product. This paper discusses how an object-oriented persistent object manager named ROSE, under development at Rensselaer, has been used in the Rensselaer CIM program to develop a STEP/PDES-compliant product database for its research test bed. In so doing, it provides an overview of the requirements for a product database system in an integrated design and manufacturing facility, and it discusses how the chosen system meets these requirements. 相似文献
112.
Kring Ann M.; Kerr Sandra L.; Smith David A.; Neale John M. 《Canadian Metallurgical Quarterly》1993,102(4):507
Although accorded historical significance, affective features of schizophrenia have only begun to receive systematic empirical attention. Interestingly, both early psychopathology writers and more recent investigators have reported frequent discrepancies between schizophrenics' feelings and outward expressions of emotion. Using a more comprehensive assessment of emotion, the present study examines the relationship between emotional experience and expression in a sample of medication-free schizophrenics. Compared with their normal counterparts, schizophrenics were indeed much less facially expressive of both positive and negative emotions during emotion-eliciting films, yet they reported experiencing as much positive and negative emotion. Therefore, the blunted affect typical of some schizophrenics misrepresents their underlying emotional experience. Future research into an inhibition hypothesis is recommended. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
113.
David Lloyd Suzie Morrell Helle N. Carlsen Hans Degn Phillip E. James Christopher C. Rowlands 《Yeast (Chichester, England)》1993,9(8):825-833
Saccharomyces cerevisiae HSc was grown with ethanol at concentrations up to 10% (v/v). The immediate effects of additions of externally added ethanol on CO2 production and O2 consumption of washed organisms were studied by stopped-flow membrane inlet quadrupole mass spectrometry. Fermentative activities of organisms grown with ethanol (0–5% v/v) showed similar sensitivities to inhibition by ethanol, whereas those grown with 10% (v/v) ethanol had become protected and were markedly less sensitive. The fluidity of subcellular membrane fractions was measured by determination of the temperature dependence of the rotational order parameter of the spin label 5-doxyl stearic acid (free radical) by electron spin resonance. Mitochondria prepared from yeasts grown with 0, 7 and 9% (v/v) ethanol showed similar overall fluidity, although differences in temperature-dependent behaviour indicate altered lipid composition or lateral phase separations. On the other hand the microsomal fraction from organisms grown with 9% ethanol showed a remarkable increase in fluidity. These data suggest that the protective effects of growth with ethanol near the limit of tolerance on fermentative activities may arise from altered plasma membrane fluidity properties. 相似文献
114.
We consider an extension of the functional programming language Standard ML with a modular structure based upon concepts in category theory such as categories, functors, natural transformations and adjunctions. In essence, we are following the categorical imperative of considering arrows as well as objects. This is intended to enforce a certain mathematical rigour on the programmer, so that the only programs that can be expressed are those with a categorical significance. The essentially algebraic nature of category theory means that we may generate equational correctness conditions for the modular structure of programs, thus separating the correctness of individual functions from that of modules. We describe this programming language, give examples of its use, and explain how it is implemented in a type system. 相似文献
115.
116.
117.
Mammalian mothers provide water to their young via milk. Rodent mothers reclaim much of this water by licking the anogenital areas of their pups, stimulating reflexive urination and consuming the pups' urine. Male rodents do not provide milk (hence water) to the young, but in some species male parents may nevertheless lick their pups. We determined the amount of water transfer from pups to mothers and fathers in the biparental California mouse, Peromyscus californicus, by injecting 5-, 10-, 20-, and 30-day-old pups with tritiated water and measuring the radioactive label in maternal and paternal plasma after 24 hrs of interaction with their litter. On Days 5 and 10, mothers obtained more pup urine than did fathers. Parents consumed equivalent amounts of pup urine on Days 20 and 30. Mothers engaged in more pup anogential licking than did fathers, which accounted for the difference in pup urine consumption. Salt appetite controls, in part, pup anogential licking in lactating rats (Gubernick & Alberts, 1983). Salt appetite was not implicated in the modulation of anogential licking in the California mouse because the mice failed to display a salt appetite. Licking of young and urine consumption are not dependent solely on the bidirectional exchange of water between the dam and her offspring. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
118.
Six measures of divergent thinking were administered to 825 men ranging in age from 17 to 101 over the period from 1959 to 1972; repeat administrations were given to a subset of 278 men after a 6-year interval. Cross-sectional analyses showed curvilinear trends, with an increase in scores for men under 40 and a decline thereafter. Repeated measures analyses on subjects initially aged 33 to 74 generally replicated this finding, whereas cross-sequential analyses suggested a decline for all cohorts tested at a later time. Additional analyses suggested that not all of the decline could be attributed to reduced speed of response production. These longitudinal findings confirm earlier cross-sectional reports of decline in divergent thinking abilities with age. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
119.
120.
Whether tolerance develops to the "anorexia" induced by haloperidol (HAL) was determined. Rats were given HAL (2.5 or 5 mg/kg) either before or after access to milk for 53 days. Controls were given injections of saline. On Day 54, when all groups received pretest injections of the drug, only rats previously given posttest injections of HAL were tolerant. The absence of tolerance in rats previously given pretest injections suggests that tolerance is suppressed when rats are given access to food in the drugged state. It is concluded that tolerance develops to HAL as a result of pharmacological exposure but is suppressed by the "anhedonic" effect of the drug. The relevance of these findings to the role of reinforcement in behavioral tolerance is briefly discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献