全文获取类型
收费全文 | 858篇 |
免费 | 16篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 161篇 |
金属工艺 | 17篇 |
机械仪表 | 12篇 |
建筑科学 | 39篇 |
能源动力 | 16篇 |
轻工业 | 43篇 |
水利工程 | 5篇 |
无线电 | 47篇 |
一般工业技术 | 120篇 |
冶金工业 | 311篇 |
原子能技术 | 5篇 |
自动化技术 | 89篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 20篇 |
2013年 | 39篇 |
2012年 | 23篇 |
2011年 | 51篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 22篇 |
2007年 | 27篇 |
2006年 | 35篇 |
2005年 | 27篇 |
2004年 | 15篇 |
2003年 | 23篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 24篇 |
1982年 | 14篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1972年 | 9篇 |
1970年 | 9篇 |
1955年 | 8篇 |
排序方式: 共有880条查询结果,搜索用时 15 毫秒
31.
32.
Compared 25 mental health professionals whose primary duties involved psychotherapy with 52 laypersons aged 18–51 yrs to determine similarities and differences in their expectations of psychotherapy. Ss were administered the Therapy Expectations Scale. Differences between the 2 groups were found in degree of expected change, importance of self in problem-solving, financial emphasis, and expected duration of psychotherapy. Similarities were found in socioenvironmental areas and in emphasis on the early years of life. Laypersons tended to appreciate the active role of the client in psychotherapy and viewed therapists as experts in problem-solving. It is suggested that greater efforts be made to educate the general public as well as individual clients about the realities of psychotherapy. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
Mathematical decision theory can be combined with heuristic techniques to attack Artificial Intelligence problems. As a first example, the problem of breaking an image into meaningful regions is considered. Bayesian decision theory is seen to provide a mechanism for including problem dependent (semantic) information in a general system. Some results are presented which make the computation feasible. A programming system based on these ideas and its application to road scenes is described. 相似文献
34.
Jerome Edward A.; Young Marguerite L.; Bostwick Susan 《Canadian Metallurgical Quarterly》1969,74(2):148
Compared 15 schizophrenics with 15 controls of similar mental test status and educational background on 2 classes of elementary problems from a series of artifact testing tasks monitored by an automatic problem programing machine called the Heuristic Evaluation Problem Programmer. In terms of an index that reflects the ability to conduct the required inquiry efficiently, the groups did not differ significantly on statistical tests that employed between-Ss differences as the error variance. Repeated measures of group differences showed a small, but statistically significant, superiority for the control Ss. Intercorrelations between scores on various problem sets indicated that the tests were reliable. During the 1st 3/4 of the problem series, there was a marked inefficiency of performance in a small group of paranoid schizophrenics as compared with a group of chronic undifferentiated schizophrenics. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
Examined the effects of different types of reinforcement on the performance of 80 Black 2nd grade males on the WISC-R. Ss given candy or culturally relevant social reinforcement obtained significantly higher scores than Ss given either no reinforcement or traditional social reinforcement. (2 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
36.
High density lipoproteins (HDL) isolated by density gradient ultracentrifugation from the plasma of monkeys ingesting semipurified
diets are barely visible. This creates difficulty in separating HDL from other lower density lipoproteins following centrifugation
and necessitates collecting large quantities of background density solution to insure complete recovery of the HDL fraction.
A simple procedure is described involving the addition of β-carotene to nonhuman primate plasma prior to centrifugation which
results in the delineation of HDL as a discrete yellow-orange band without affecting certain physical properties of HDL or
interfering with standard lipid and protein assays. 相似文献
37.
Microchip-based purification of DNA from biological samples 总被引:10,自引:0,他引:10
Breadmore MC Wolfe KA Arcibal IG Leung WK Dickson D Giordano BC Power ME Ferrance JP Feldman SH Norris PM Landers JP 《Analytical chemistry》2003,75(8):1880-1886
A microchip solid-phase extraction method for purification of DNA from biological samples, such as blood, is demonstrated. Silica beads were packed into glass microchips and the beads immobilized with sol-gel to provide a stable and reproducible solid phase onto which DNA could be adsorbed. Optimization of the DNA loading conditions established a higher DNA recovery at pH 6.1 than 7.6. This lower pH also allowed for the flow rate to be increased, resulting in a decrease in extraction time from 25 min to less than 15 min. Using this procedure, template genomic DNA from human whole blood was purified on the microchip platform with the only sample preparation being mixing of the blood with load buffer prior to loading on the microchip device. Comparison between the microchip SPE (microchipSPE) procedure and a commercial microcentrifuge method showed comparable amounts of PCR-amplifiable DNA could be isolated from cultures of Salmonella typhimurium. The greatest potential of the microchipSPE device was illustrated by purifying DNA from spores from the vaccine strain of Bacillus anthracis, where eventual integration of SPE, PCR, and separation on a single microdevice could potentially enable complete detection of the infectious agent in less than 30 min. 相似文献
38.
A Series of comparisons were conducted to test the capabilities of a range of metrological techniques and analytical laboratories engaged in the assay of thorium in the workplace. The results of these exercises are presented together with the decision criteria used to determine whether results are significantly different from the true value. The discussion highlights those aspects which warrant closer and further attention. 相似文献
39.
Jerome R. Bellegarda 《IEEE transactions on audio, speech, and language processing》2007,15(3):957-965
The level of quality that can be achieved by modern concatenative text-to-speech synthesis heavily depends on a judicious composition of the unit inventory used in the unit selection process. Unit boundary optimization, in particular, can make a huge difference in the users' perception of the concatenated acoustic waveform. This paper considers the iterative refinement of unit boundaries based on a data-driven feature extraction framework separately optimized for each boundary region. This guarantees a globally optimal cut point between any two matching units in the underlying inventory. The associated boundary training procedure is objectively characterized, first in terms of convergence behavior, and then by comparing the distributions in inter-unit discontinuity obtained before and after training. Experimental results underscore the viability of this approach for unit boundary optimization. Listening evidence also qualitatively exemplifies a noticeable reduction in the perception of discontinuity between concatenated acoustic units 相似文献
40.
Previously developed micromechanical methods for stiffness and strength prediction are adapted for analysis of multi-layer plain weave textile composites. Utilizing the direct micromechanics method (DMM) via finite element modeling, three methods are presented: (a) direct simulation of a multi-layer plain weave textile composite; (b) micromechanical analysis of a single layer of interest from the force and moment resultants acting on that layer; and (c) application of the previously developed quadratic stress-gradient failure theory to the layer of interest. In comparison to direct modeling, the other two techniques show only 5% difference over a number of random test cases. Several practical design examples of strength prediction are included to illustrate the importance and accuracy of method implementation. 相似文献