全文获取类型
收费全文 | 22327篇 |
免费 | 806篇 |
国内免费 | 66篇 |
专业分类
电工技术 | 240篇 |
综合类 | 32篇 |
化学工业 | 4568篇 |
金属工艺 | 491篇 |
机械仪表 | 415篇 |
建筑科学 | 1192篇 |
矿业工程 | 75篇 |
能源动力 | 555篇 |
轻工业 | 1794篇 |
水利工程 | 270篇 |
石油天然气 | 90篇 |
武器工业 | 3篇 |
无线电 | 1549篇 |
一般工业技术 | 4093篇 |
冶金工业 | 4467篇 |
原子能技术 | 119篇 |
自动化技术 | 3246篇 |
出版年
2023年 | 131篇 |
2022年 | 253篇 |
2021年 | 410篇 |
2020年 | 309篇 |
2019年 | 320篇 |
2018年 | 447篇 |
2017年 | 387篇 |
2016年 | 509篇 |
2015年 | 388篇 |
2014年 | 624篇 |
2013年 | 1338篇 |
2012年 | 1059篇 |
2011年 | 1400篇 |
2010年 | 1015篇 |
2009年 | 995篇 |
2008年 | 1176篇 |
2007年 | 1158篇 |
2006年 | 949篇 |
2005年 | 889篇 |
2004年 | 773篇 |
2003年 | 634篇 |
2002年 | 730篇 |
2001年 | 404篇 |
2000年 | 396篇 |
1999年 | 367篇 |
1998年 | 406篇 |
1997年 | 366篇 |
1996年 | 338篇 |
1995年 | 368篇 |
1994年 | 327篇 |
1993年 | 349篇 |
1992年 | 278篇 |
1991年 | 184篇 |
1990年 | 264篇 |
1989年 | 228篇 |
1988年 | 193篇 |
1987年 | 241篇 |
1986年 | 181篇 |
1985年 | 262篇 |
1984年 | 250篇 |
1983年 | 212篇 |
1982年 | 170篇 |
1981年 | 155篇 |
1980年 | 122篇 |
1979年 | 126篇 |
1978年 | 134篇 |
1977年 | 98篇 |
1976年 | 109篇 |
1975年 | 101篇 |
1974年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Mark N. Frolick 《Information Systems Management》2003,20(1):29-34
As more companies develop Web sites to show or sell their products online, there is a corresponding increase in attacks by those who want to maliciously damage a company's reputation or steal its resources. Securing a Web site against savvy hackers can be a daunting task for a firm's Webmaster. This article explores the threat of attack and the measures that a company can take to gain its highest level of defense. 相似文献
22.
Kahler Christopher W.; Read Jennifer P.; Wood Mark D.; Palfai Tibor P. 《Canadian Metallurgical Quarterly》2003,17(3):226
Structural equation modeling was used to test the mediational role of social environmental selection on alcohol use in cross-sectional samples of 447 students from a rural state university and 421 students from an urban private university. Results showed that male gender, White ethnicity, and sensation seeking were uniquely associated with greater alcohol use. Mediational analyses indicated that socioenvironmental factors (i.e., Greek involvement, friends' approval of drinking/getting drunk) were positively associated with alcohol use and significantly accounted for parts of the effects of ethnicity and sensation seeking, but not gender, on alcohol use. Results suggest that White students and those high on sensation seeking may drink more heavily in college, in part because they select social environments in which alcohol use is encouraged. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
Notes that, with this issue, the journal Psychoanalytic Psychology begins its 20th year of publication. The journal's editor discusses new features for 2003, and the unique contributions of the journal as the second largest psychoanalytic journal published in the US. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
24.
The author tested the hypothesis that a history of drug-induced antagonism of alcohol impairment would enhance alcohol tolerance in humans. Groups of participants (N = 21) repeatedly performed a psychomotor task under different drug treatments: 0.65 g/kg alcohol, 4 mg/kg caffeine, or both drugs combined. Tolerance to a 0.65 g/kg alcohol dose challenge was then tested. Results showed that a history of combined alcohol and caffeine administrations increased alcohol tolerance compared with an exposure history to either drug alone. The findings contribute to the understanding of the complexities of polydrug use history and provide a useful model to examine how alcohol tolerance might be affected by a history of coadministration with other drugs (e.g., cocaine and nicotine). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
25.
The current study replicated, in a sample of 2,300 outpatients seeking psychiatric treatment, a previous study (R. F. Krueger & M. S. Finger, 2001) that implemented an item response theory approach for modeling the comorbidity of common mood and anxiety disorders as indicators along the continuum of a shared latent factor (internalizing). The 5 disorders examined were major depressive disorder, social phobia, panic disorder/agoraphobia, specific phobia, and generalized anxiety disorder. The findings were consistent with the prior research. First, a confirmatory factor analysis yielded sufficient evidence for a nonspecific factor underlying the 5 diagnostic indicators. Second, a 2-parameter logistic item response model showed that the diagnoses were represented in the upper half of the internalizing continuum, and each was a strongly discriminating indicator of the factor. Third, the internalizing factor was significantly associated with 3 indexes of social burden: poorer social functioning, time missed from work, and lifetime hospitalizations. Rather than the categorical system of presumably discrete disorders presented in DSM-IV, these 5 mood and anxiety disorders may be alternatively viewed as higher end indicators of a common factor associated with social cost. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
26.
Comments on the original article "A New Big Five: Fundamental Principles for an Integrative Science of Personality," by Dan P. McAdams and Jennifer L. Pals (see record 2006-03947-002). McAdams and Pals (April 2006) presented a new model to integrate the field of personality psychology. Cultural and evolutionary factors interact with an individual's basic traits, characteristic adaptations, and life narratives, which in turn are linked to roles, demands, and behaviors. The current authors welcome McAdams and Pals's (2006) model for providing a way to integrate much of the previously disparate empirical findings in personality psychology. However, the current authors also think that McAdams and Pals (2006) overstated the inclusiveness of the model, and more generally, the current authors dispute their assertion that the grand theories of personality can be integrated within a single model. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
NE Joseph C Fiocchi AD Levine 《Canadian Metallurgical Quarterly》1997,122(4):809-14; discussion 814-6
BACKGROUND: Crohn's disease (CD) and ulcerative colitis (UC) are chronic inflammatory diseases, and their pathogenesis is attributed, in part, to alterations of the mucosal immune system. This study was designed to define the possible contribution of epithelial cells to the activation of lamina propria T lymphocytes (LPTs) in CD and UC. METHODS: LPTs isolated from CD, UC, and control surgical specimens were cocultured with freshly isolated allogeneic or autologous epithelial cells or epithelial cell lines. Resulting T-cell proliferation was evaluated by tritiated thymidine incorporation on day 5. RESULTS: When intestinal epithelial cells were used to stimulate mucosal T-cell proliferation, CD and UC LPTs were less responsive than control LPTs (p < 0.05 and p < 0.03, respectively). This difference between inflamed and control T cells was consistently observed by using a variety of different intestinal epithelial cell types. CONCLUSIONS: CD and UC mucosal T cells are hyporesponsive to activation by intestinal epithelial cells when compared with control LPTs. Elucidating the mechanism underlying the differential activation of CD and UC LPTs may help to better understand the immunopathogenesis of these conditions. 相似文献
28.
AJ Joseph 《Canadian Metallurgical Quarterly》1997,17(4):685-699
Conceptually, the Chest Pain Center model is nothing more than a system of delivering health care. It is a model that all hospitals can embrace as a framework for organizational decision making in meeting the heart-care needs of their communities. It also provides a framework for clinical decision making. By adopting some or all of the common features of the model, hospitals develop a common language, similar to what took place when CCUs first opened in the 1960s. Application of evidence-based clinical practice is promoted. Approaches that account for both clinical outcomes and financial outcomes will be further refined. One result will be simultaneous improvement in clinical outcomes and a decrease in costs, but the most important aspect of the Chest Pain Center model is that it puts the patient first. 相似文献
29.
Masako Yudasaka Rie Kikuchi Takeo Matsui Yoshimasa Ohki Mark Baxendale Susumu Yoshimura Etsuro Ota 《Thin solid films》1996,280(1-2):117-123
Thin film formation of graphite by chemical vapor deposition using 2-methyl-1,2′-naphthyl ketone as a starting material was carried out on Ni film substrates. On Ni films directly deposited on quartz glass, the graphite films were obtained when the Ni film thickness was above 1 000 Å and above 5 000 Å at 700 °C and 1 000 °C, respectively. Depositions on thinner Ni film substrates comprise amorphous carbon (a-C) or graphite tubes which was owing to the thermal coagulation of the Ni film into droplets. On the other hand, graphite film was obtained on the Ni film with thickness 10 Å when a-C was inserted between the Ni film and the quartz glass. The coagulation of the Ni film is considered to be avoided by inserting a-C layer. 相似文献
30.
Mark Hawthorne 《Language Resources and Evaluation》1994,28(1):19-27
TACT, a freeware program from the University of Toronto's Centre for Computing in the Humanities, is a highly sophisticated tool for text retrieval; although written for experienced critics and researchers, it can teach undergraduate students to read literature in new, fresh ways. Without requiring that the user become either a programmer, linguist, mathematician, or statistician,TACT introduces the literature student to the computer as a research tool. Studies of imagery and symbolism, of structural patterns, and of prosody can result from the student's careful tagging of a literary text and can yield significant insights into the work of literature. Students who use the computer as such a tool learn to read literary texts more closely and to think more clearly about literary problems. 相似文献