全文获取类型
收费全文 | 2346篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 126篇 |
金属工艺 | 17篇 |
机械仪表 | 19篇 |
建筑科学 | 45篇 |
矿业工程 | 3篇 |
能源动力 | 10篇 |
轻工业 | 69篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 78篇 |
一般工业技术 | 97篇 |
冶金工业 | 1822篇 |
原子能技术 | 5篇 |
自动化技术 | 57篇 |
出版年
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 31篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 26篇 |
2008年 | 21篇 |
2007年 | 28篇 |
2006年 | 16篇 |
2005年 | 20篇 |
2004年 | 24篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 14篇 |
1999年 | 48篇 |
1998年 | 500篇 |
1997年 | 285篇 |
1996年 | 213篇 |
1995年 | 125篇 |
1994年 | 105篇 |
1993年 | 113篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 21篇 |
1989年 | 34篇 |
1988年 | 35篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 17篇 |
1980年 | 33篇 |
1979年 | 6篇 |
1978年 | 14篇 |
1977年 | 68篇 |
1976年 | 135篇 |
1975年 | 13篇 |
1973年 | 4篇 |
1965年 | 5篇 |
1964年 | 6篇 |
1954年 | 6篇 |
1941年 | 4篇 |
排序方式: 共有2367条查询结果,搜索用时 250 毫秒
51.
The Eysenck Personality Profiler (EPP), a set of 21 scales measuring primary traits hypothesized to be definers of Neuroticism, Extraversion, and Psychoticism factors, was administered to 229 adults together with the Eysenck Personality Questionnaire--Revised (H. J. Eysenck & S. B. G. Eysenck, 1991) and the Revised NEO Personality Inventory (NEO-PI-R; P. T. Costa & R. R. McCrae, 1992b). Correlations of EPP scales with NEO-PI-R facet scales provided preliminary evidence supporting the convergent and discriminant validity of the EPP scales. However, varimax and targeted validimax factor analyses suggested that some EPP scales were misclassified and that EPP scales could better be understood in terms of the 5-factor model than the intended 3-factor model. 相似文献
52.
53.
JA Teresi RR Golden P Cross B Gurland M Kleinman D Wilder 《Canadian Metallurgical Quarterly》1995,48(4):473-483
A study of item bias in standard cognitive screening measures was conducted in a sample of Afro-American, Hispanic and non-Hispanic white elderly respondents who were part of a dementia case registry study. The methods of item-response theory were applied to identify biased items. Both cross-cultural and high and low education groups were examined to determine which items were biased. Out of 50 cognitive items examined from six widely used cognitive screening measures, 16 were identified as biased for either high and low education groups or ethnic/racial group membership. 相似文献
54.
55.
One way hospitals complicate themselves is by increasing the participation of clinical professionals and middle managers in making strategic decisions. Using a survey methodology this article investigates the relationships between the participation of clinical professionals (MDs and RNs) and middle managers with hospital costs, as well as the possible moderating effect of strategic complexity. 相似文献
56.
We have analyzed X-chromosome inactivation patterns in lymphocytes of 264 females from 38 families not known to have any genetic disease. Quantitative measures of X-inactivation showed strong sister-sister correlation in the degree of departure from equal numbers of cells having each X chromosome active, suggesting heritability of this phenotype. Strong sister-sister correlation was also observed for the fraction of cells having the same parent's X chromosome active, consistent with the possibility that this trait might be controlled by a cis-acting, X-linked gene. We used a sib-pair approach to determine whether X-inactivation phenotype was linked to loci in any region of the X chromosome. Both quantitative and discrete measures of X-inactivation phenotype showed evidence of linkage to markers in the region of the X inactivation center (XIC). The quantitative measure of X-inactivation phenotype used in our study also showed linkage to loci at Xq25-q26. This study provides the first evidence for X-linked inheritance of X chromosome inactivation phenotype derived from linkage analysis in phenotypically normal human families. 相似文献
57.
The discriminative stimulus effects of the imidazopyridine hypnotic zolpidem and the classic benzodiazepine hypnotic triazolam were examined in seven healthy volunteers using a three-response drug discrimination procedure and a within-subject design. During an initial sampling phase, the training drug conditions (placebo, 20 mg/70 kg zolpidem, and 0.5 mg/70 kg triazolam) were identified to subjects by letter codes before oral drug administration. During a subsequent training phase, subjects earned money for correct drug identifications made 3.75 h after drug administration. Five out of seven subjects acquired the three-response discrimination. Analyses of standardized and unstructured self-report questionnaires revealed that zolpidem and triazolam produced different profiles of effects; zolpidem was associated with a number of negative somatic symptoms including nausea, blurred vision, visual images/hallucinations, and heavy limbs, whereas triazolam was associated with greater sedative effects. These results demonstrate a distinct profile of discriminative stimulus and subjective effects for zolpidem, relative to triazolam, which is consistent with its somewhat distinct pharmacological profile, and provide evidence for the sensitivity of the three-response drug discrimination procedure for detecting between-drug differences. 相似文献
58.
The Dufour's gland secretion ofXylocopa virginica texana possesses short-term repellency for conspecifics when applied to passion flowers. This secretion contains a number of straight-chain hydrocarbons. The two major components are the methyl esters of palmitic and myristic acid. A mixture of the two esters and two of the available hydrocarbons were as effective as the Dufour's gland extract in eliciting a response in females to the passion flower,Passiflora incarnata, to which the extract was applied.Approved as TA13387 by the Director, Texas Agricultural Experiment Station and conducted in cooperation with the USDA. Supported in part by NSF-DEB-76-03963. 相似文献
59.
N. A. Khan W. E. Tolberg D. H. Wheeler W. O. Lundberg 《Journal of the American Oil Chemists' Society》1954,31(11):460-466
- It has been confirmed that the principal products formed in the oxidation of methyl oleate by oxygen under a variety of conditions are predominantlytrans hydroperoxides. However no inversion of the double bond occurs in unoxidized oleate. Hence the conversion ofcis totrans double bonds and peroxide formation occur together in the same molecules.
- The autoxidation of methyl linoleate at low temperature yields predominantlycis,trans conjugated hydroperoxides. Autoxidation at 25°C., oxidation catalyzed by visible light, or ultraviolet light and copper soap catalyzed oxidation at temperatures appreciably above 0°C., lead to the formation primarily oftrans,trans conjugated hydroperoxides. The inversion of the second double bond in this case appears to be independent of the peroxide-forming reactions.
- The photochlorophyll oxidation of methyl linoleate leads to the formation of some unconjugated hydroperoxides, some of which containtrans double bonds.
- Under all of the conditions employed in the present investigation, the oxidation of methyl oleate and linoleate led primarily to the formation of monomeric peroxides which retained most of the unsaturation of the parent compound.
60.
Summary The rates of polymerization of alpha and beta eleostearates agree with second order kinetics, as would be expected for a bimolecular
Diels-Alder addition. The all-trans, beta isomer reacts faster than thecis, trans, trans alpha isomer, in agreement with knowncis, trans effects on diene activity.
The polymerization of normal linoleate follows an apparent first order reaction. It is suggested that conjugation is the slow
rate determining monomolecular reaction, as has been proposed for the non-conjugated linoleate isomers.
Paper No. 177, Journal Series, Research Laboratories, General Mills Inc. Presented at the 28th fall (Paul Bunyan) meeting
of the American Oil Chemists’' Society, Oct. 12, 1954, Minneapolis, Minn. 相似文献