全文获取类型
收费全文 | 36374篇 |
免费 | 1307篇 |
国内免费 | 63篇 |
专业分类
电工技术 | 371篇 |
综合类 | 29篇 |
化学工业 | 7241篇 |
金属工艺 | 725篇 |
机械仪表 | 738篇 |
建筑科学 | 1965篇 |
矿业工程 | 114篇 |
能源动力 | 1054篇 |
轻工业 | 2901篇 |
水利工程 | 430篇 |
石油天然气 | 117篇 |
武器工业 | 5篇 |
无线电 | 2477篇 |
一般工业技术 | 6118篇 |
冶金工业 | 6607篇 |
原子能技术 | 268篇 |
自动化技术 | 6584篇 |
出版年
2023年 | 214篇 |
2022年 | 440篇 |
2021年 | 688篇 |
2020年 | 464篇 |
2019年 | 618篇 |
2018年 | 782篇 |
2017年 | 697篇 |
2016年 | 835篇 |
2015年 | 758篇 |
2014年 | 1044篇 |
2013年 | 2373篇 |
2012年 | 1680篇 |
2011年 | 2093篇 |
2010年 | 1651篇 |
2009年 | 1549篇 |
2008年 | 1800篇 |
2007年 | 1776篇 |
2006年 | 1592篇 |
2005年 | 1440篇 |
2004年 | 1174篇 |
2003年 | 1123篇 |
2002年 | 1052篇 |
2001年 | 702篇 |
2000年 | 550篇 |
1999年 | 595篇 |
1998年 | 585篇 |
1997年 | 576篇 |
1996年 | 552篇 |
1995年 | 574篇 |
1994年 | 527篇 |
1993年 | 511篇 |
1992年 | 500篇 |
1991年 | 288篇 |
1990年 | 418篇 |
1989年 | 389篇 |
1988年 | 319篇 |
1987年 | 356篇 |
1986年 | 310篇 |
1985年 | 418篇 |
1984年 | 416篇 |
1983年 | 318篇 |
1982年 | 296篇 |
1981年 | 281篇 |
1980年 | 270篇 |
1979年 | 270篇 |
1978年 | 249篇 |
1977年 | 226篇 |
1976年 | 207篇 |
1975年 | 195篇 |
1974年 | 173篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
61.
62.
63.
At high temperatures in clean oxidizing environments, SiC forms a very protective SiO2 film, but, in environments containing low levels of gaseous alkali salt contaminants or where condensed salts may deposit on the surface, the resistance of the film is significantly reduced. Oxidation kinetics of SiC were measured by continuous thermogravimetric analysis in a controlled environment containing CO2 , H2 O, and O2 plus low levels of potassium-containing salts. Potassium was found to be incorporated into the SiO2 scale and to significantly change its transport properties and its morphology. The rate of scale formation was found to increase directly in proportion to K in the scale. A change in mechanism was observed when water vapor was added to the reacting gas stream. 相似文献
64.
David C. Apperley Robin K. Harris Gregory L. Marshall Derek P. Thompson 《Journal of the American Ceramic Society》1991,74(4):777-782
The 29 Si MAS NMR spectra of the 2H, 4H, 6H, and 3C polytypes of silicon carbide are presented. An attempt is made to correlate differences in the chemical shifts with local atomic environment. The results of the analysis of the spectra of pure polytypes are used as a basic for the interpretation of the spectra of mixed polytypes and a discussion of the crystallinity and impurity levels of different samples. Carbon-13 chemical shifts obtained from spectra of the same polytypes are also tabulated. 相似文献
65.
David E. Wilkins 《Computational Intelligence》1988,4(3):373-380
Reasoning about actions necessarily involves tracking the truth of assertions about the world over time. The SIPE planning system retains the efficiency of the STRIPS assumption for this while enhancing expressive power by allowing the specification of a causl theory. Separation of knowledge about causality from knowledge about actions relieves operators of much of their representational burden and allows them to be applicable in a wide range of contexts. The implementation of causal theories is described, together with examples and evaluations of the system's expressive power and efficiency. 相似文献
66.
Benson Janette B.; Cherny S. S.; Haith Marshall M.; Fulker David W. 《Canadian Metallurgical Quarterly》1993,29(3):434
Assessed infant predictors of adult IQ with same-sex infant twins (114 pairs) and their parents. The midtwin–midparent design permits the rapid assessment of infant measures to predict later behavior, because the midparent score serves as a proxy for the infant's potential score at maturity. At 5, 7, and 9 mo, Ss were observed on the Fagan Test of Infant Intelligence, hand preference, vocalizations, selected Bayley Scales of Infant Development items, and a modified Bayley Infant Behavior Record. At 8 mo, Ss received the Visual Expectation Paradigm and an auditory discrimination task. Their parents received the Wechsler Adult Intelligence Scale—Revised (WAIS—R). Some infant measures, indicative of information processing, language ability, and temperament, predicted midparent IQ. This study extended and partially replicated findings from a previous midtwin–midparent cohort (L. F. DiLalla et al; see record 1991-04066-001). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
67.
68.
69.
Tobin David L.; Johnson Craig; Steinberg Stacey; Staats Marian; Dennis Amy Baker 《Canadian Metallurgical Quarterly》1991,100(1):14
Investigated a multifactorial approach to the assessment of bulimia nervosa by means of hierarchical factor analysis. 245 bulimia nervosa patients and 68 patients with either anorexia nervosa or eating disorders not otherwise specified were administered a self-report battery that was organized into 21 dimensions relevant to eating disorder patients. When dimensions from this battery were subjected to hierarchical factor analysis, support for bulimia nervosa as a unique diagnostic category was obtained. However, the emergence of 3 secondary factors and 6 primary factors suggests that bulimia nervosa can also be described more complexly. The emergence of a multifactorial model of bulimia nervosa that incorporates several existing unidimensional models suggests the potential for both divergent and complicated clinical presentation in bulimia nervosa patients. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.
David A. Carlson 《The Journal of supercomputing》1992,6(2):107-116
In this paper a set of techniques for improving the performance of the fast Fourier transform (FFT) algorithm on modern vector-oriented supercomputers is presented. Single-processor FFT implementations based on these techniques are developed for the CRAY-2 and the CRAY Y-MP, and it is shown that they achieve higher performance than previously measured on these machines. The techniques include (1) using gather/scatter operations to maintain optimum length vectors throughout all stages of small-to medium-sized FFTs, (2) using efficient radix-8 and radix-16 inner loops, which allow a large number of vector loads/stores to be overlapped, and (3) prefetching twiddle factors as vectors so that on the CRAY-2 they can later be fetched from local memory in parallel with common memory accesses. Performance results for Fortran implementations using these techniques demonstrate that they are faster than Cray's library FFT routine CFFT2. The actual speedups obtained, which depend on the size of the FFT being computed and the supercomputer being used, range from about 5 to over 300%. 相似文献