全文获取类型
收费全文 | 1412篇 |
免费 | 60篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 17篇 |
综合类 | 2篇 |
化学工业 | 242篇 |
金属工艺 | 26篇 |
机械仪表 | 55篇 |
建筑科学 | 34篇 |
矿业工程 | 1篇 |
能源动力 | 26篇 |
轻工业 | 74篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 144篇 |
一般工业技术 | 262篇 |
冶金工业 | 326篇 |
原子能技术 | 6篇 |
自动化技术 | 252篇 |
出版年
2023年 | 12篇 |
2022年 | 13篇 |
2021年 | 26篇 |
2020年 | 12篇 |
2019年 | 19篇 |
2018年 | 36篇 |
2017年 | 17篇 |
2016年 | 36篇 |
2015年 | 25篇 |
2014年 | 42篇 |
2013年 | 55篇 |
2012年 | 72篇 |
2011年 | 98篇 |
2010年 | 67篇 |
2009年 | 55篇 |
2008年 | 58篇 |
2007年 | 57篇 |
2006年 | 41篇 |
2005年 | 45篇 |
2004年 | 39篇 |
2003年 | 38篇 |
2002年 | 44篇 |
2001年 | 31篇 |
2000年 | 19篇 |
1999年 | 37篇 |
1998年 | 75篇 |
1997年 | 66篇 |
1996年 | 30篇 |
1995年 | 25篇 |
1994年 | 23篇 |
1993年 | 32篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 11篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1978年 | 5篇 |
1977年 | 13篇 |
1976年 | 18篇 |
1973年 | 6篇 |
1965年 | 4篇 |
1962年 | 4篇 |
1956年 | 4篇 |
排序方式: 共有1474条查询结果,搜索用时 15 毫秒
1.
2.
Marks L D Ciston J Deng B Rondinelli J 《电子显微学报》2006,25(B08):1-2
Many areas of structure analysis have focused on finding the locations of the atoms. If, instead of the atoms, we knew the positions of the electrons we would in fact know much more, and in most respects knowing where the nuclei are is not important. There is a long history of measurements using precise electron diffraction or X-ray diffraction of the average charge density in materials, but extending beyond to local charge density is, as yet, an unexplored area. 相似文献
3.
4.
OBJECTIVE: We examined the test-retest reliability and the construct validity of the measurement of knee position sense for describing the functional weightbearing performance of women with osteoarthritis (OA) of the knee. METHODS: For the purpose of this study, position sense was defined as the error occurring when subjects attempted to reproduce a criterion angle in standing with visual cues eliminated. Five such tests were recorded photographically on 3 different occasions. On each occasion the 10 subjects also completed a self-paced walking test over a 13 m indoor walkway. RESULTS: The photographic measurements were reproducible (r = 0.90) and there was no change in positioning accuracy across sessions. There was a significant (p < 0.05) inverse correlation of 0.70 between the standard deviation of the mean individual measurements of position sense (precision of the test) and those of walking speed. CONCLUSION: Our study demonstrates good measurement reliability and a comparable mean angular error with repeated tests. It also suggests the amplitude of the variability of this error is a strong determinant of an individual OA patient's functional performance in walking. 相似文献
5.
Mark Sherman Jonathan Rosenberg Ann Marks Jaap Akkerhuis 《Computer Standards & Interfaces》1991,11(3):177-182
Many advanced document systems provide a formatting mechanism called ‘style sheets’ Style sheets provide a great deal of flexibility in describing a document's format, and allow easy maintenance of different house styles for a collection of documents. In this paper, we describe the basics of general style sheet systems, argue that successful document interchange must include the exchange of style sheet information, and evaluate ODA's style mechanism against this requirement. 相似文献
6.
7.
8.
Arun K. Nanda Honda Shing Ten-Hwan Tzen Lionel M. Ni 《Journal of Parallel and Distributed Computing》1991,12(4)
A standard metric conventionally employed to compare the performance of different multiprocessor systems is speedup. Although providing a measure of the improvement in execution speed achievable on a system, this metric does not yield any insight into the factors responsible for limiting the potential improvement in speed. This paper studies the performance degradation in shared-memory multiprocessors as a result of contention for shared-memory resources. A replicate workload framework with a flexible mechanism for workload specification is proposed for measuring performance. Two normalized performance metrics—efficiency and overhead factor—are introduced to quantify the factors limiting performance and facilitate comparison across architectures. Finally, the proposed model is employed to measure and compare the performance of three contemporary shared-memory systems, with special emphasis on the newly released BBN Butterfly-II (TC2000), currently undergoing Beta test. 相似文献
9.
KE Goodwill C Sabatier C Marks R Raag PF Fitzpatrick RC Stevens 《Canadian Metallurgical Quarterly》1997,4(7):578-585
Tyrosine hydroxylase (TyrOH) catalyzes the conversion of tyrosine to L-DOPA, the rate-limiting step in the biosynthesis of the catecholamines dopamine, adrenaline, and noradrenaline. TyrOH is highly homologous in terms of both protein sequence and catalytic mechanism to phenylalanine hydroxylase (PheOH) and tryptophan hydroxylase (TrpOH). The crystal structure of the catalytic and tetramerization domains of TyrOH reveals a novel alpha-helical basket holding the catalytic iron and a 40 A long anti-parallel coiled coil which forms the core of the tetramer. The catalytic iron is located 10 A below the enzyme surface in a 17 A deep active site pocket and is coordinated by the conserved residues His 331, His 336 and Glu 376. The structure provides a rationale for the effect of point mutations in TyrOH that cause L-DOPA responsive parkinsonism and Segawa's syndrome. The location of 112 different point mutations in PheOH that lead to phenylketonuria (PKU) are predicted based on the TyrOH structure. 相似文献
10.
Schmitter-Edgecombe Maureen; Marks William; Fahy John F. 《Canadian Metallurgical Quarterly》1993,7(2):136
The 2-process theory of semantic priming (J. H. Neely, 1977; M. I. Posner and C. R. Snyder, 1975) was used to determine the maintenance of automatic processes after severe closed head injury (CHI) and to determine whether processes that demand attention suffer a deficit. Ss with severe CHI (N?=?18,?>?2 yrs postinjury) and 18 matched control Ss completed a lexical decision task in which a category prime was followed by a target. Automatic and attentional priming were determined by orthogonally varying prime–target relatedness, expectancy, and stimulus onset asynchrony. Although the CHI Ss had slower reaction times (RTs) overall, there were no significant group differences in the magnitude of either the automatic or attentional component of semantic priming. The present results indicate the integrity of semantic processes and normal semantic priming in long-term patients with severe CHI. The results are discussed in relation to an attentional resource hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献