全文获取类型
收费全文 | 259786篇 |
免费 | 3594篇 |
国内免费 | 822篇 |
专业分类
电工技术 | 5131篇 |
综合类 | 331篇 |
化学工业 | 37229篇 |
金属工艺 | 10253篇 |
机械仪表 | 8489篇 |
建筑科学 | 6105篇 |
矿业工程 | 1076篇 |
能源动力 | 6392篇 |
轻工业 | 22859篇 |
水利工程 | 2561篇 |
石油天然气 | 3908篇 |
武器工业 | 68篇 |
无线电 | 34746篇 |
一般工业技术 | 50075篇 |
冶金工业 | 46583篇 |
原子能技术 | 5419篇 |
自动化技术 | 22977篇 |
出版年
2021年 | 2038篇 |
2019年 | 2034篇 |
2018年 | 3468篇 |
2017年 | 3534篇 |
2016年 | 3728篇 |
2015年 | 2319篇 |
2014年 | 4049篇 |
2013年 | 11286篇 |
2012年 | 6563篇 |
2011年 | 8877篇 |
2010年 | 6983篇 |
2009年 | 7852篇 |
2008年 | 8682篇 |
2007年 | 8616篇 |
2006年 | 7804篇 |
2005年 | 7143篇 |
2004年 | 6888篇 |
2003年 | 6733篇 |
2002年 | 6370篇 |
2001年 | 6469篇 |
2000年 | 6172篇 |
1999年 | 6254篇 |
1998年 | 14253篇 |
1997年 | 10274篇 |
1996年 | 8115篇 |
1995年 | 6414篇 |
1994年 | 5715篇 |
1993年 | 5584篇 |
1992年 | 4553篇 |
1991年 | 4216篇 |
1990年 | 4053篇 |
1989年 | 3786篇 |
1988年 | 3626篇 |
1987年 | 3170篇 |
1986年 | 3066篇 |
1985年 | 3611篇 |
1984年 | 3385篇 |
1983年 | 3033篇 |
1982年 | 2854篇 |
1981年 | 2955篇 |
1980年 | 2760篇 |
1979年 | 2651篇 |
1978年 | 2501篇 |
1977年 | 2946篇 |
1976年 | 3556篇 |
1975年 | 2316篇 |
1974年 | 2315篇 |
1973年 | 2318篇 |
1972年 | 1849篇 |
1971年 | 1745篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
941.
The development and creating of new-generation full-scope simulator and new technology of simulation
N. N. Ponomarev-Stepnoi V. A. Lebedev M. M. Khudiykov S. D. Malkin V. V. Shalia I. D. Rakitin 《Nuclear Engineering and Design》1997,173(1-3)
Set out is a brief account of the two major accomplishments by the Russian Research Center ‘Kurchatov Institute’ in creating the full-scope simulators and mathematical modeling technologies. Presented are the basic specifications of one of the world's largest simulators—the full-scope simulator for the Leningrad NPP which is the new-generation one. Owing to the extended modeling scope accomplished is the possibility of training personnel to act in terms of not only the design-basis but rather beyond the design-basis accidents. To minimize the expenditures for creating the simulators, analyzers and other modeling and control means, the RRC ‘Kurchatov Institute' has created the unique technology of mathmodeling automation. Thanks to its versatility and application at its creation of the ELUD philosophy (easy to learn, use and develop) good use is made of this technology both in nuclear and thermal power engineering, as well as in gas industry. 相似文献
942.
Two experiments were conducted to explore the interaction of the two cerebral hemispheres in motor control, by examining hand, space and attentional asymmetries in goal-directed aiming. In Experiment 1, right-handed subjects moved to targets more quickly with their right hand than their left hand. In addition, each hand was faster when moving in its own hemispace. Although in a control condition, movements were initiated more quickly with the left hand, visual distractors disrupted left hand performance more than right hand performance. For contralateral aiming, ipsilateral distractors caused the greatest interference. In Experiment 2, when targets and distractors were all presented at the midline, a right hand advantage was found for movement time along with a left hand advantage for reaction time, independent of target and distractor location. Our findings are discussed in terms of a right hemisphere role in movement preparation and the allocation of attention in space, and greater left hemisphere involvement in movement execution. 相似文献
943.
944.
We first performed autogenous bone grafting for lesions of the hallux sesamoid in 1984. During the next 9 years, 21 patients (11 men and 10 women with an average age of 34 and 32 years, respectively) underwent this surgical procedure for symptomatic tibial hallux sesamoid non-unions. Successful bony union was achieved in all but two patients. The majority of patients obtained concomitant relief of preoperative symptomatology and returned to their preinjury level of activity. We believe that this procedure serves as an alternative to hallux sesamoid excision in selected cases. 相似文献
945.
Emulsifiers are an uncommon cause of allergic contact dermatitis. Five cases of allergic contact dermatitis to cetostearyl alcohol are presented. In all five cases, multiple positive reactions to other allergens were present, usually topical corticosteroid creams. 相似文献
946.
947.
Bez R. Cantarelli D. Moioli L. Ortolani G. Servalli G. Villa C. Dallabora M. 《Electron Device Letters, IEEE》1998,19(2):37-39
A new method to erase a standard (double-poly, stacked-gate NOR-type) flash cell is proposed. The method, still using the tunneling mechanism to extract electrons from the floating gate, is based on the concept of keeping the electric field constant during the whole erasing operation. The new method has two main advantages with respect to the conventional one: (1) it does not depend on the supply voltage variation and (2) it allows a better reliability in terms of endurance-induced stress. Results have shown that flash device performances are greatly improved in terms of stability and endurance reliability up to one million cycles 相似文献
948.
Kang W.P. Wisitsora-at A. Davidson J.L. Kerns D.V. 《Electron Device Letters, IEEE》1998,19(10):379-381
A boron-doped diamond field emitter diode with ultralow turn-on voltage and high emission current is reported. The diamond field emitter diode structure with a built-in cap was fabricated using molds and electrostatic bonding techniques. The emission current versus anode voltage of the capped diamond emitter diode with boron doping, sp2 content, and vacuum thermal electric (VTE) treatment shows a very low turn-on voltage of 2 V. A high emission current of 1 μA at an anode voltage of less than 10 V can be obtained from a single diamond tip. The turn-on voltage is significantly lower than comparable silicon field emitters 相似文献
949.
D. Dietrich ÖVE H. Reiter Th. Sauter H. -J. Schweinzer 《e & i Elektrotechnik und Informationstechnik》1997,114(5):225-230
The past decade may be regarded as the phase of the fundamental developments in fieldbus systems that were based on the OSI model. Today we are entering a second stage. It is the objective of this issue to present the current state and where the further developments will lead to. This introductory article is intended to give an overview on the subject. 相似文献
950.
The admixture test (A-test) is a popular method for the analysis of linkage data when locus heterogeneity is suspected. It can be applied on pairwise linkage data, multipoint data and even for the simultaneous analysis of data from multiple dispersed candidate regions. However, very little is known about the conditions for the use of the method under these divergent circumstances. By performing analytical evaluations, we demonstrate that the A-test is inconsistent if there is a relationship between the phenotype and the probability of being linked. Biased estimates of the recombination fraction (theta) and the proportion of linked families (alpha) may occur if the actual frequency of linked families is not identical among small and large families. We conclude that the A-test should be used with caution if the phenotype and the probability of developing the phenotype at a certain age cannot be shown to be equal for family members of linked and unlinked families. If dissimilarities in family size cannot be ruled out, the extent of bias should be considered and size specific alpha-values should be used in risk calculations. 相似文献