全文获取类型
收费全文 | 975篇 |
免费 | 34篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 127篇 |
金属工艺 | 6篇 |
机械仪表 | 11篇 |
建筑科学 | 49篇 |
矿业工程 | 2篇 |
能源动力 | 10篇 |
轻工业 | 100篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 28篇 |
一般工业技术 | 93篇 |
冶金工业 | 395篇 |
原子能技术 | 4篇 |
自动化技术 | 175篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 23篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 43篇 |
2012年 | 30篇 |
2011年 | 53篇 |
2010年 | 30篇 |
2009年 | 35篇 |
2008年 | 49篇 |
2007年 | 36篇 |
2006年 | 32篇 |
2005年 | 29篇 |
2004年 | 39篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 26篇 |
2000年 | 14篇 |
1999年 | 20篇 |
1998年 | 17篇 |
1997年 | 26篇 |
1996年 | 29篇 |
1995年 | 17篇 |
1994年 | 28篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 6篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 15篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 9篇 |
1973年 | 8篇 |
排序方式: 共有1013条查询结果,搜索用时 156 毫秒
71.
Aldwin Carolyn M.; Spiro Avron; Levenson Michael R.; Bossé Raymond 《Canadian Metallurgical Quarterly》1989,4(3):295
Longitudinal changes in self-reported symptoms were investigated using the Cornell Medical Index (CMI) in a sample of 2,041 men. The average man completed 5 CMIs (range?=?2–8) over 17 (range?=?2–25) years. Using a two-stage growth model, we first regressed symptoms against time on study for each man. The average slope of physical symptoms showed a moderate increase over time, but the average slope of psychological symptoms showed little change. Next individual differences in change were examined using age at entry as an explanatory variable. Age accounted for 50% of the variance in physical symptoms at entry and 7% of the variance in slopes, but explained neither baseline level nor change in psychological symptoms. Rather, a U-shaped curve described the relation between age and psychological symptom change. These results, in concert with a developmental perspective, may help reconcile conflicting findings on aging and mental health. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
Reviews the history of the issues addressed in the National Association of School Psychologists (NASP) position statement "Advocacy for the Appropriate Educational Services for All Children." Concerns about required labeling of children for services and the efficacy of resulting programs have been evident since the early years of NASP, with special emphasis since 1983. Numerous NASP activities support the objective of alternative educational service options. Implications of the Advocacy Statement for proactive initiatives are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
Cunningham Michael R.; Barbee Anita P.; Pike Carolyn L. 《Canadian Metallurgical Quarterly》1990,59(1):61
The multiple motive hypothesis of physical attractiveness suggests that women are attracted to men whose appearances elicit their nurturant feelings, who appear to possess sexual maturity and dominance characteristics, who seem sociable, approachable, and of high social status. Those multiple motives may cause people to be attracted to individuals who display an optimal combination of neotenous, mature, and expressive facial features, plus desirable grooming attributes. Three quasi-experiments demonstrated that men who possessed the neotenous features of large eyes, the mature features of prominent cheekbones and a large chin, the expressive feature of a big smile, and high-status clothing were seen as more attractive than other men. Further supporting the multiple motive hypothesis, the 2nd and 3rd studies indicated that impressions of attractiveness had strong relations with selections of men to date and to marry but had a curvilinear relation with perceptions of a baby face vs a mature face. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
Texture mapping is a method commonly used to increase the visual complexity of computer generated images while maintaining simplicity in the underlying geometric models. Texture maps are generally defined in two dimensional space; thus, a primary problem when applying textures to objects is determining a mapping transformation from the three dimensional space of the object to the two dimensional space of the map. A method for mapping complex polygonal geometries is presented. The algorithmunfolds the object polygon by polygon and projects the texture map onto the resulting two dimensional geometry. Enhancements to the basic unfolding algorithm either (1) control the location of map distorition introduced at areas of severe curvature or (2) average distortions over a larger area. 相似文献
75.
Two experiments examined long-term repetition priming in data entry. In each experiment, participants entered 4-digit numbers displayed as either words or numerals, and responded with digits (Experiment 1), or either digits or initial letters (Experiment 2). At test 1 week later, they entered old and new numbers, with the format changed for half of the old stimuli. Implicit memory was evidenced at test by faster entry of the old than the new numbers, regardless of whether the numbers were in the same or different format, suggesting that the abstract numerical meaning, not the surface form, contributes to repetition priming. Numbers presented as words in training had an advantage over numbers presented as numerals, regardless of response format, implying that type of processing also contributes to the effect and ruling out an explanation based on time spent processing numbers in word format. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
This study empirically identified types of African American families. Adolescents (N=111) were assessed on family functioning. With cluster analytic methods, 3 types of families were identified. The cohesive-authoritative type was above average on parental education and income, averaged about 2 children, exhibited a high quality of family functioning and high self-esteem in adolescents. The conflictive-authoritarian type had average parental education and income, an average of 2.7 children, exhibited controlling and rigid discipline, and placed a high emphasis on achievement. The defensive-neglectful type was predominately headed by single mothers with below average education and income and averaged about 3 children. Such families displayed chaotic family processes, and adolescents tended to suffer from low self-esteem. The typology exhibited good reliability. The implications of the typology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
A group of rhesus monkeys, consisting of 8 matrilines of up to 4 generations each and 9 unrelated adult males, was studied for 2 yrs. Group size varied between 75 and 91 individuals. Data collection consisted of ad lib recording of agonistic interactions. Results indicate that adult male interference in agonistic episodes was strongly biased against adolescent and adult male participants, whereas adult female interference was biased in favor of kin and in support of younger animals against older animals. Although natal males also were biased in favor of their kin, their selective targeting of sexually mature males was independent of kinship. Adolescent males targeted adult males, but only in defense of kin. It is suggested that this selective interference against adolescent and adult males by adult males has the potential to profoundly modify male agonistic participation in intragroup encounters after puberty. Because female support is influenced primarily by kinship, females less consistently interfere against male agonistic participants. Adult males may therefore play an important role in the socialization of male agonistic expression. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
David Greaves James Mulligan Jefferson Creek Carolyn A. Koh 《Chemical engineering science》2008,63(22):5410-5419
The accuracy of the focused beam reflectance measurement (FBRM) probe, which measures a chord length distribution, from Mettler-Toledo Lasentec® has been explored. A particle video microscope (PVM) probe, which provides in situ digital images, was used as a direct visual method to test the reliability of the FBRM results. These probes can provide in situ particle characterization at high pressures. The FBRM has been used to study emulsions and ice and clathrate hydrate formation. The ability of the FBRM to accurately characterize unimodal and bimodal distributions of particles and droplets and to measure agglomeration events was investigated. It was found that while the FBRM can successfully identify system changes, certain inaccuracies exist in the chord length distributions. Particularly, the FBRM was found to oversize unimodal distributions of glass beads, but undersize droplets in an emulsion and was unable to measure full agglomerate sizes. The onset of ice and hydrate nucleation and growth were successfully detected by the FBRM, but quantitative analysis of the particle and agglomerate sizes required simultaneous PVM measurements to be performed. 相似文献
79.
Weisz John R.; Southam-Gerow Michael A.; McCarty Carolyn A. 《Canadian Metallurgical Quarterly》2001,110(1):97
The contingency–competence–control (CCC) model links contingency and competence beliefs to perceived control and, in turn, to depression. However, a developmental perspective suggests that noncontingency may be too abstract a concept to be directly tied to depression before adolescence. We tested the CCC model and this developmental notion, using structural equation modeling, with 360 clinic-referred 8- to 17-year-olds. The CCC model fit the data well for the full sample accounting for 46% of the variance in depression. Separate analyses by age group placed perceived contingency in the best-fit model for adolescents (ages 12–17 years) but not for children (8–11 years). This suggests that abstract cause–effect concepts may have more direct affective impact after the cognitive changes of adolescence (e.g., formal operations) than before. Finally, the CCC model accounted for much more variance in depression than conduct problems, suggesting diagnostic specificity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
Bossé Raymond; Aldwin Carolyn M.; Levenson Michael R.; Workman-Daniels Kathryn; Ekerdt David J. 《Canadian Metallurgical Quarterly》1990,5(1):41
Cross-sectional differences between retirees and workers in the importance of coworkers as a source of support, as well as in general quantitative support (social networks and frequency of interaction) and qualitative support (confidants and the perceived reliability of support) were examined. The sample consisted of 1,513 older men (mean age?=?61), participants in the Normative Aging Study. Half (56%) were working, and the rest were retired. Slightly fewer retirees than workers reported coworker friends, especially among those who were long-term retirees or who did not work at all in retirement. Whereas similar findings were seen with quantitative support, workers and retirees reported nearly identical levels of qualitative support. However, retirees almost never discussed personal problems with former coworkers. The relevance of these findings for the convoy construct is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献