全文获取类型
收费全文 | 9414篇 |
免费 | 367篇 |
国内免费 | 18篇 |
学科分类
工业技术 | 9799篇 |
出版年
2023年 | 67篇 |
2021年 | 198篇 |
2020年 | 164篇 |
2019年 | 154篇 |
2018年 | 209篇 |
2017年 | 187篇 |
2016年 | 206篇 |
2015年 | 148篇 |
2014年 | 250篇 |
2013年 | 530篇 |
2012年 | 424篇 |
2011年 | 519篇 |
2010年 | 352篇 |
2009年 | 371篇 |
2008年 | 439篇 |
2007年 | 437篇 |
2006年 | 348篇 |
2005年 | 315篇 |
2004年 | 286篇 |
2003年 | 248篇 |
2002年 | 263篇 |
2001年 | 118篇 |
2000年 | 128篇 |
1999年 | 132篇 |
1998年 | 163篇 |
1997年 | 147篇 |
1996年 | 156篇 |
1995年 | 139篇 |
1994年 | 140篇 |
1993年 | 150篇 |
1992年 | 118篇 |
1991年 | 107篇 |
1990年 | 131篇 |
1989年 | 103篇 |
1988年 | 81篇 |
1987年 | 127篇 |
1986年 | 97篇 |
1985年 | 127篇 |
1984年 | 123篇 |
1983年 | 131篇 |
1982年 | 104篇 |
1981年 | 93篇 |
1980年 | 77篇 |
1979年 | 74篇 |
1978年 | 92篇 |
1977年 | 71篇 |
1976年 | 74篇 |
1975年 | 79篇 |
1974年 | 82篇 |
1972年 | 55篇 |
排序方式: 共有9799条查询结果,搜索用时 852 毫秒
101.
102.
Lavine Howard; Huff Joseph W.; Wagner Stephen H.; Sweeney Donna 《Canadian Metallurgical Quarterly》1998,75(2):359
In 3 experiments, the authors assessed whether attitude strength moderates the susceptibility of attitudes to item context effects in surveys. In Experiment 1, respondents completed multiple measures of attitude strength. Three weeks later, respondents participated in a context experiment. Results revealed that respondents with weak attitudes exhibited significantly larger context effect for 1 of 2 issues. In Experiment 2, the results of Experiment 1 were conceptually replicated by use of measures of interattitudinal embeddedness to assess attitude strength. In Experiment 3, significant strength-moderated context effects were found when attitude strength was assessed in a multi-item, multidimensional manner but not when it was assessed with a single item. Discussion focuses on measurement and theoretical issues related to the moderation and mediation of context effects in attitude surveys. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
104.
In the high-performance IC design with increasing design complexity,it is a very important design content to efficiently analyze IC parameters.Thus,the electro-thermal (ET) analyses including power/ground (P/G) analysis and thermal analysis are hot topics in today’s IC research.Since ET analysis equation has a sparse,positive definite and strictly diagonally dominant coefficient-matrix,we prove that the ET analysis has the advantage of locality.Owing to this advantage,localized relaxation method is formally proposed,which has the same accuracy as the global relaxation done with the constraint of the same truncation error limitation.Based on the localized relaxation theory,an efficient and practical localized successive over-relaxation algorithm (LSOR2) is introduced and applied to solve the following three ET analysis problems.(1) Single-node statistical voltage analysis for over-IR-drop nodes in P/G networks;(2) single-node statistical temperature analysis for hot spots in 3D thermal analysis;(3) fast single open-defect analysis for P/G networks.A large amount of experimental data demonstrates that compared with the global successive over-relaxation (SOR) algorithm,LSOR2 can speed up 1-2 orders of magnitudes with the same accuracy in ET analyses. 相似文献
105.
Emma P. Bullock Allison L. Roxburgh Patricia S. Moyer-Packenham Elif Bektas Joseph S. Webster Kathleen A. Bullock 《Journal of Computer Assisted Learning》2021,37(2):557-586
This study focused on an examination of how type, quality and children's awareness of design features in digital math games, along with an awareness of the mathematics goals of the game, were related to learning outcomes. We conducted a parallel conversion mixed methods study with 45 students in Grades 3 and 4 (ages 9–10). Students participated in clinical interviews using three digital math games. The results suggest a moderated mediation relationship in which the quality of the design features moderated the mediating impact of children's awareness of the game's design features, specifically when the child was aware of the mathematics content learning goal (MCLG) of the game. These findings show how important it is that design features are of high quality in a digital math game, and how this is intertwined with children's awareness of the features and the MCLG. When these variables intertwined in just the right way, the interactions between the children and the digital math game afforded mathematical learning growth. 相似文献
106.
Microsystem Technologies - Tuberculosis is a contagious disease caused by the bacteria, Mycobacterium Tuberculosis. Early detection of TB is vital to increase the chances of cure. In this paper, a... 相似文献
107.
Microsystem Technologies - A force sensor utilizing a transformer concept with a ferrofluid core was developed. A ferrofluid reservoir was machined out of Teflon and the open top of the reservoir... 相似文献
108.
Joseph H. Magill 《Journal of Inorganic and Organometallic Polymers》1992,2(2):213-229
Variations in thermotropic behavior have been investigated for many crystalline polyphosphazenes. Experimental results obtained from DSC, solid-state MAS NMR, dilatometry, mechanical property (creep and dynamic) measurements, birefringence, X-ray (wide and small-angle), and electron diffraction have been made as a function of temperature in an attempt to elucidate the structure-morphology behavior in these polymers. Initially all polyphosphazenes described in this study crystallize from dilute or moderately concentrated solutions in the monoclinic form with relatively low crystallinity (50%). When heated, these specimens expand atT(1) and adopt a chain-extended 2D mesophase morphology in order to relieve congestion. Above this first-orderT(1) temperature a chain-extended –P=N– chain backbone morphology transforms into an isotropic phase at the melting temperatureT
m. When cooled, samples transform into the mesostate. However, crystallization from the mesophase belowT(1) takes place into a 3D orthorhombic state. These two modes of ordering/disordering are in accordance with (i) a hexatic chain packing [betweenT(1) andT
m] with variously mobile side groups that also exhibits smectic features when mesogenic side groups are present and (ii) a 3D orthorhombic structure of high crystallinity belowT(1). The initial monoclinic phase is accessible only via a solution crystallization route. Solid-state MAS NMR, crystallization kinetic measurements, and optical microscopy studies obtained from oriented and unoriented polymers have been especially germane in providing a unifying picture for mesophase formation and ordering in polyoxyphosphazenes. X-ray and electron diffraction evidence is complicated by critical overlapping peaks that are found under these same conditions. They demonstrate that (a) positional disorder exists along the chain direction and (b) the side chain above, as well as below, theT(1) transition is governed by the mobility, size, and type of side group in circumstances where phase transformations occur. 相似文献
109.
Joseph Segman 《Multidimensional Systems and Signal Processing》1992,3(4):353-361
The aim of this paper is to compute the discrete inverse Radon transform over
n
. The Radon transform is a function with domainS
n–1×. It is shown that under different measure this function can be defined with domain
n
. In this case one can compute the discrete inverse Radon transform in the Cartesian coordinate system without interpolating from polar to Cartesian coordinates or using the backprojection operator. 相似文献
110.
Joseph R. Fox P. Costa Kokoropoulos Gary H. Wiseman H. K. Bowen 《Journal of Materials Science》1987,22(12):4528-4531
Organosilanes of the general formula R
x
Si(OR)4–x
(where R is an alkyl group and R = CH3 or CH2CH3) were used to sterically stabilize hexane dispersions of submicrometre silica spheres. The dispersions were characterized according to sediment volume results. For 0.5m silica particles, the sediment density increased by more than a factor of three up to 50 to 55% of theoretical in the presence of organosilanes with 12 or more carbons in the R group. Solid-state13C nuclear magnetic resonance was used to characterize the powder-dispersant interaction; this technique can distinguish between carbons in the R group of the organosilane and residual organic groups in the silica. Scanning electron micrographs of filter compacts were used to further characterize the dispersions and indicated the presence of primary particles as well as small agglomerates. 相似文献