全文获取类型
收费全文 | 1184篇 |
免费 | 26篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 31篇 |
综合类 | 43篇 |
化学工业 | 130篇 |
金属工艺 | 37篇 |
机械仪表 | 39篇 |
建筑科学 | 70篇 |
矿业工程 | 3篇 |
能源动力 | 7篇 |
轻工业 | 64篇 |
水利工程 | 15篇 |
石油天然气 | 15篇 |
武器工业 | 2篇 |
无线电 | 35篇 |
一般工业技术 | 24篇 |
冶金工业 | 696篇 |
原子能技术 | 1篇 |
自动化技术 | 30篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2015年 | 21篇 |
2014年 | 71篇 |
2013年 | 48篇 |
2012年 | 31篇 |
2011年 | 97篇 |
2010年 | 25篇 |
2009年 | 54篇 |
2008年 | 31篇 |
2007年 | 37篇 |
2006年 | 29篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 16篇 |
1998年 | 199篇 |
1997年 | 118篇 |
1996年 | 81篇 |
1995年 | 58篇 |
1994年 | 34篇 |
1993年 | 43篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1978年 | 6篇 |
1977年 | 24篇 |
1976年 | 42篇 |
1975年 | 4篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
1961年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有1242条查询结果,搜索用时 8 毫秒
141.
K Dong T Qu FA Ahmed L Zhang K Yamada NG Guison M Miller T Yamadori 《Canadian Metallurgical Quarterly》1996,736(1-2):61-67
A sample of 443 Pakistani infants from four different socioeconomic areas was followed longitudinally study the emergence of the primary teeth. The mean ages of emergence of the primary teeth, without regard what kind of tooth and dental ages of the primary teeth were calculated. The subjects showed no sexual dimorphism in the emergence times of the primary teeth. The children from poor areas. were ahead by statistically significant differences from upper middle class, for emergence of the primary teeth 17-20. On comparison with Swedish standards (H?gg & Taranger, 1985) Pakistani children are delayed, by a statistically significant difference, in the emergence of primary teeth 1-16, however, they were at par in the emergence of 17-20 primary teeth. 相似文献
142.
143.
144.
145.
HM Jin NG Copeland DJ Gilbert NA Jenkins RB Kirkpatrick M Rosenberg 《Canadian Metallurgical Quarterly》1998,54(2):316-322
The induction of Fos protein was examined within LHRH neurons of guinea pigs; the aim was to delineate relationships between subgroups of LHRH neurons during an LH surge in a laboratory rodent in which the distribution of LHRH neurons and the presence of a true luteal phase in the reproductive cycle resemble those in primates. Approximately one third of the forebrain population of LHRH neurons was examined in ovariectomized steroid-treated guinea pigs killed either before or during a steroid-induced LH surge. LHRH/Fos double-labeled neurons were more abundant in surging compared to presurge guinea pigs (p = 0.008) and were most abundant within the preoptic area and anterior hypothalamus. Nonetheless, double-labeled LHRH/Fos neurons were observed throughout the remainder of the population of LHRH neurons in surging guinea pigs. A relative loss of LHRH reaction product was detected by image analysis in the LHRH terminals in the median eminence of surging guinea pigs, consistent with augmented LHRH release. Thus, there appears to be a coordinated increase in Fos expression in subgroups of LHRH neurons, more pronounced in rostral, as compared to caudal, regions in guinea pigs killed after the peak of the steroid-induced LH surge. 相似文献
146.
Undeveloped wheat dough samples were strained in shear and extensional flow between parallel plates to produce a controlled level of development. Dough made in a standard Farinograph, considered developed dough, was used for comparison. Scanning electron microscopy images of deformed dough were subjected to numerical image processing to characterize the protein matrix present. Results were compared to dynamic rheological properties to evaluate the influence of strain deformation on the formation of microstructure. Viscoelastic moduli of wheat dough showed that developed dough had the greatest amount of structure formation, followed by extensionally-strained and shear-strained samples, respectively. Undeveloped dough showed the lowest levels of structure development. Image analysis indicated statistically significant differences between protein matrices in developed and undeveloped samples; however, results were not significantly different between shear- and extension-ally-strained samples. 相似文献
147.
Identified groups of neurons in positive (the lateral hypothalamic area, the lateral preoptic area) and negative (the ventromedial hypothalamus) emotional regions were examined under the different levels of food motivation and emotionally positive and negative intracranial stimulation. The responses of the neurons in classical and operant conditioning were different. This difference was manifested in tonic (during location of the animal into the chamber) and phasic alterations of neuronal activity and at certain stages of conditioned reflex performance. During classical conditioning were revealed the reciprocal relations in unit activity of the positive and negative emotional structures. During the operant reflex more complicated pattern of reactions was observed being connected with realization of a necessity of removing from the negative influences. During defensive reflex in the cases of classical conditioning and avoidance reaction reinforcement was related with engaging the negative emotional mechanisms while in the course of escape reaction the positive emotional mechanism being engaged. 相似文献
148.
NG Wood 《Canadian Metallurgical Quarterly》1976,29(6):530-533
Two blood culturing systems were compared in parallel-a semi-automated radiometric method, BACTEC1, and the conventional method used in our laboratory. BACTEC contains radioactive 14C labelled substrates and monitors the level of 14CO2 evolved by actively metabolizing bacteria. BACTEC was as efficient as the conventional method in detecting positive cultures and indicated that it was superior in detecting positive cultures earlier than the conventional system. 相似文献
149.
150.