全文获取类型
收费全文 | 1495篇 |
免费 | 19篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 1516篇 |
出版年
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 17篇 |
2018年 | 11篇 |
2017年 | 14篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 22篇 |
2013年 | 69篇 |
2012年 | 39篇 |
2011年 | 47篇 |
2010年 | 39篇 |
2009年 | 30篇 |
2008年 | 51篇 |
2007年 | 45篇 |
2006年 | 38篇 |
2005年 | 43篇 |
2004年 | 32篇 |
2003年 | 43篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 18篇 |
1999年 | 41篇 |
1998年 | 122篇 |
1997年 | 82篇 |
1996年 | 63篇 |
1995年 | 60篇 |
1994年 | 48篇 |
1993年 | 35篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 29篇 |
1989年 | 32篇 |
1988年 | 27篇 |
1987年 | 34篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 17篇 |
1977年 | 23篇 |
1976年 | 31篇 |
1975年 | 7篇 |
1969年 | 7篇 |
1967年 | 6篇 |
1966年 | 7篇 |
排序方式: 共有1516条查询结果,搜索用时 265 毫秒
91.
The effects of lesions of the medial dorsal thalamic nucleus (MD) on blocking and latent inhibition (LI) of the rat eyeblink response were examined in the present study. Previous work has demonstrated that the cingulate cortex and related thalamic areas are involved in processing conditioning stimuli throughout training. The experiments in the present study tested the hypothesis that disruption of cingulothalamic stimulus processing produced by lesions of the MD would impair 2 types of associative learning that involve decremental changes in attention. In Experiment 1, MD lesions severely impaired blocking. In Experiment 2, NM lesions severely impaired LT. The results indicate that lesions of the NM impair incremental, decremental, or both types of changes in stimulus processing during learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
92.
B.D. Freeman E.L. Ryba R.C. Bowman Jr J.R. Phillips 《International Journal of Hydrogen Energy》1997,22(12):1125-1131
Sorption cryocoolers utilize metal hydride sorbent beds for the closed-cycle circulation of gaseous hydrogen through heat exchangers and a Joule-Thomson (J-T) expansion valve in order to achieve cold-stage temperatures below 30 K. These devices have high potential for satellite missions that require long term reliability, minimal vibrations, and low operating power. Designs for nominal 25 K liquid and 10 K solid hydrogen refrigerators are described. Prototype hydride sorbent beds for breadboard studies of sorption cryocoolers have been fabricated and tested to simulate expected operation. The sorbents contained in the beds are VHx, LaNi5−ySnyHx, and ZrNiHx. Some of these hydride beds have been integrated with a hydrogen J-T cold-stage. These experiments confirm that the selected metal hydrides and bed designs satisfy the constraints associated with the proposed liquid and solid hydrogen cryocoolers. 相似文献
93.
PURPOSE: In a recent study we found an increased resistive index immediately after extracorporeal shock wave lithotripsy (ESWL) in patients older than 60 years, which suggests renovascular disturbance. The present 26-month followup study was undertaken to investigate the relevance of elevated resistive index levels and the incidence of new onset hypertension. MATERIALS AND METHODS: Of the initial 76 patients 57, including 20 of the 23 at risk patients 60 or greater years, group 3), were followed for more than 26 +/- 6 months after ESWL. Followup included 2 resistive index measurements by Doppler ultrasound of the treated and the contralateral kidney, at least 2 blood pressure measurements 1 week apart and excretory urography as well as determination of plasma renin activity in 9 patients. RESULTS: With 1 exception, elevated resistive index levels and hypertension were observed exclusively in patients older than 60 years. In these patients the resistive index ranged between 0.65 and 0.86 (mean plus or minus standard deviation 0.74 +/- 0.05, normal less than 0.7). This increase in resistive index was statistically significant (p < 0.0001). Compared to the levels obtained immediately after ESWL, the resistive index continued to increase in all 9 patients older than 60 years who had hypertension (45%), whereas in the normotensive patients the resistive index was either stable or decreased. There was a strong positive correlation (0.903) between pathological resistive index levels and blood pressure. CONCLUSIONS: Patients older than 60 years are at risk for disturbances of renal perfusion as assessed by the resistive index, and 45% of these patients have new onset hypertension within 26 months of treatment. 相似文献
94.
95.
96.
97.
Freeman Nicholas; Friedman Ronald S.; Bartholow Bruce D.; Wulfert Edelgard 《Canadian Metallurgical Quarterly》2010,18(2):135
Recent studies have suggested that exposure to rudimentary alcohol cues activates mental representations of alcohol expectancies in long-term memory, thereby promoting expectancy-consistent behavior changes. However, reliance in these previous studies on self-report measures raises the possibility that prior findings were an artifact of experimental demand. The present study was aimed at ruling out this alternative explanation by reinvestigating the effects of alcohol priming on nonconsumptive behavior using an implicit measure of social disinhibition. In three experiments, participants were exposed to either alcohol or control beverage images, then asked to type as quickly as possible the first word that came to mind in response to a series of provocative (e.g., feces) and neutral (e.g., chair) stimulus words. Participants’ response times were surreptitiously measured. Results revealed that participants exposed to images of alcohol, relative to control beverages, were faster to generate free associations to provocative, but not neutral, words, suggesting enhanced social disinhibition. This effect was limited to conditions of heightened evaluation, ruling out alternative explanations based on knowledge activation or arousal. Participants reported no suspicions regarding the connection between the image viewing and free association tasks nor any awareness that their response times had been collected. Results suggest that the behavioral effects of alcohol priming do not result from demand characteristics and offer the first evidence that exposure to rudimentary alcohol-related stimuli may suffice to influence social disinhibition in a manner akin to that expected to result from actual or placebo alcohol consumption. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
Kaiser Susan B.; Wingate Stacy B.; Freeman Carla M.; Chandler Joan L. 《Canadian Metallurgical Quarterly》1987,32(1):51
Investigated appearance management (AM) as a social–psychological variable in 322 physically disabled university students. The questionnaire included an AM and social interaction scale and measures of acceptance of disability. A tendency to regard AM as a form of compensation was associated with a tendency to view physical disability as a central or salient aspect of personal identity. Data suggest that AM is regarded by some as a means for ameliorating the social impact of a physical disability, but is expected to serve only a secondary role in impression formation. The relationship between disability acceptance and predisposition toward AM is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
100.
Edelman H. Brock G.W. Carr T. Freeman J. Smith N. 《IEEE transactions on magnetics》1990,26(6):3004-3009
An 8-track magnetic tape head for high-frequency, high-density applications is described. It includes an unshielded magnetoresistive read head and two thin-film record heads for bidirectional operation with write verification. The MR sensors are biased by specially shaped thin-film permanent magnets (PM) that provide fields along both sensor axes to linearize output and eliminate Barkhausen noise. Nearly all films in the head are deposited using dry processes. Deposition conditions for the PM have been optimized to produce a high-coercivity, high-remanence isotropic film. The final head assembly has a contour that utilizes longitudinal slots to achieve intimate contact with low head-to-tape pressure. The associated data channel uses both read and write equalization to obtain the desired output pulse shape from the unshielded head 相似文献