全文获取类型
收费全文 | 7949篇 |
免费 | 317篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 72篇 |
综合类 | 7篇 |
化学工业 | 1523篇 |
金属工艺 | 106篇 |
机械仪表 | 149篇 |
建筑科学 | 327篇 |
矿业工程 | 9篇 |
能源动力 | 226篇 |
轻工业 | 542篇 |
水利工程 | 61篇 |
石油天然气 | 29篇 |
武器工业 | 2篇 |
无线电 | 578篇 |
一般工业技术 | 1107篇 |
冶金工业 | 2366篇 |
原子能技术 | 34篇 |
自动化技术 | 1144篇 |
出版年
2023年 | 65篇 |
2022年 | 86篇 |
2021年 | 170篇 |
2020年 | 122篇 |
2019年 | 125篇 |
2018年 | 176篇 |
2017年 | 157篇 |
2016年 | 193篇 |
2015年 | 160篇 |
2014年 | 223篇 |
2013年 | 407篇 |
2012年 | 366篇 |
2011年 | 428篇 |
2010年 | 326篇 |
2009年 | 370篇 |
2008年 | 353篇 |
2007年 | 368篇 |
2006年 | 264篇 |
2005年 | 253篇 |
2004年 | 207篇 |
2003年 | 188篇 |
2002年 | 157篇 |
2001年 | 105篇 |
2000年 | 112篇 |
1999年 | 134篇 |
1998年 | 511篇 |
1997年 | 384篇 |
1996年 | 230篇 |
1995年 | 203篇 |
1994年 | 161篇 |
1993年 | 154篇 |
1992年 | 76篇 |
1991年 | 41篇 |
1990年 | 62篇 |
1989年 | 83篇 |
1988年 | 64篇 |
1987年 | 50篇 |
1986年 | 59篇 |
1985年 | 62篇 |
1984年 | 44篇 |
1983年 | 57篇 |
1982年 | 37篇 |
1981年 | 47篇 |
1980年 | 54篇 |
1979年 | 26篇 |
1978年 | 21篇 |
1977年 | 76篇 |
1976年 | 154篇 |
1975年 | 31篇 |
1974年 | 22篇 |
排序方式: 共有8282条查询结果,搜索用时 578 毫秒
61.
Application of a Neuroelectric Model to Electrocutaneous Sensory Sensitivity: Parameter Variation Study 总被引:1,自引:0,他引:1
A previous publication discussed results from a neuro-electric model for analyzing excitation of myelinated nerve by external electrical stimuli. The studied model is an adaptation of the one developed by McNeal. The present paper examines how membrane and geometric parameter variations affect electrical sensitivity calculated with the model. 相似文献
62.
Forty-three patients with spastic quadriplegia (mean age 7.9 years, range 3.3 to 17.2 years) underwent bone mineral density (BMD) measurement of the lumbar spine and were evaluated between 2.6 and 5.5 years (mean 3.8) later to determine whether this measurement had predicted risk of fracture over the subsequent period of observation. Other potential risk factors that were evaluated include body weight z score, serum vitamin D levels, previous fracture, and hip spica casting. The baseline measurements showed that BMD falls further below normal with increasing age and was more than one standard deviation below age-matched normal mean in 38 of the 43 patients. Fracture rate did not differ between those with low and those with very low spinal BMD. Similarly, serum vitamin D levels and body weight z scores were not predictive of fracture. However, fracture rate was over fourfold greater following spica casting and more than threefold greater following an initial fracture. Fracture rates in the study group were similar to those reported for age- and sex-matched normal children, though generally the location of the fractures and mechanisms of injury differed. 相似文献
63.
Witold Brostow Bernard Bujard Patrick E. Cassidy Haley E. Hagg Pablo E. Montemartini 《Materials Research Innovations》2002,6(1):7-12
Samples were prepared by addition of a fluorinated poly(aryl ether ketone) (12F-PEK) to a commercial epoxy resin and curing
at either 24 °C or 70 °C. The concentrations of fluoropolymer in the samples were 0, 5, 10, 20, 30, 40, and 50%. Phase inversion
facilitates the formation of more and more smooth surfaces for scratch testing with increasing fluoropolymer concentration.
A progressively increasing load from 0.03 N to 12 N was administered with a diamond tip to the surfaces of the samples; depths
were determined within ±7.5 nm. The original scratch depth is a function of the fluoropolymer concentration. Scratch recovery
(healing) reaches values up to 95%. Plots of the residual depth versus concentration of the fluoropolymer at 4, 6, 8, and
10 N reveal minima for all forces and both temperatures. Addition of only 5% or 10% 12F-PEK improves the scratch recovery
significantly. The results are explained by changes of material morphology with the fluoropolymer concentration.
Electronic Publication 相似文献
64.
65.
Sylvia V A Uzochukwu Esther Balogh Owen G Tucknot Mervyn J Lewis Patrick O Ngoddy 《Journal of the science of food and agriculture》1994,64(4):405-411
Palm wine and pasteurised palm sap volatiles were collected, concentrated on a Tenax GC and analysed by gas chromatography and gas chromatography-mass spectrometry. Eighty-two components were identified: 47 esters, 9 alcohols, 5 acids, 6 carbonyls, 2 acetals, 4 terpenes and 9 hydrocarbons. These had all been found previously in conventional wines. Odour evaluation of the separated palm wine components as they eluted suggested that no one compound is responsible for the characteristic palm wine odour. The acetates of higher alcohols and the ethyl esters of straight-chain aliphatic C6-C10 acids seemed to be important and may play a big role in imparting the fruity nuances of characteristic palm wine odour. Their association with alcohols seemed also to be necessary for the expression of typical palm wine odour. The qualitative difference between palm sap aroma and palm wine aroma appeared to be due mainly to the presence of these esters and alcohols in palm wine and their apparent absence from palm sap, as well as to the presence of some low-boiling esters and alcohols in palm sap and their apparent absence from palm wine. 相似文献
66.
P Verkade LH Schrama AJ Verkleij WH Gispen AB Oestreicher 《Canadian Metallurgical Quarterly》1997,79(4):1207-1218
Calmodulin and de-phosphorylated B-50/growth-associated protein-43 (GAP-43) have been shown to bind in vitro in a molecular complex, but evidence for an in situ association in the nervous system does not exist. Previously, we have reported that, in the model of the regenerating rat sciatic nerve, the B-50/GAP-43 immunoreactivity is increased and concentrated at the axolemma of unmyelinated axons located proximal to the site of injury and axon outgrowth. To explore a putative function of B-50/GAP-43, namely, the capacity of binding calmodulin to the plasma membrane, we examined the ultrastructural distribution of calmodulin in the proximal unmyelinated axon shafts of this model, using double immunolabelling and detection by fluorescent or gold probes conjugated to second antibodies. Immunofluorescence showed that seven days post-sciatic nerve crush the calmodulin immunoreactivity, similar to B-50/GAP-43 immunoreactivity, was intense in unmyelinated axon shafts located proximal to the site of injury of the regenerating nerve. Ultrastructurally, calmodulin was located at the axolemma of these regenerating unmyelinated axon shafts and inside the axoplasm, where it was associated with vesicles and microtubules. The plasma membrane labelling (approximately 69%) was significantly higher than the axoplasmic labelling. Over 60% of the plasma membrane-associated calmodulin co-localized with B-50/GAP-43 in a non-random distribution. Since normally calmodulin is largely present in the cytoplasm, these data suggest that calmodulin has been concentrated at the plasma membrane of unmyelinated axons, most probably by B-50/GAP-43. If the concentrating effect is due to B-50/GAP-43, then there is a possibility that these proteins may be present as a molecular complex in situ. The physiological significance could be that this association regulates the local availability of both B-50/GAP-43 and calmodulin for other interactions. 相似文献
67.
This paper is the first part of a work devoted to the setting-up of a methodology for the mechanical behaviour characterization of rubber-like materials, using a digital speckle extensometer. We present here the experimental approach, specific to large strain measurements. The proposed method is based on in-plane kinematics measurements using an optical extensometer. The whole two-dimensional field of in-plane displacements is obtained by a digital image processing. We discuss then the correlation calculations and how to achieve the optimal subset matching. Next, we specify how to derive the principal stretch ratios, and the accuracy on these components, issued from a subsequent numerical calibration.Finally, we present experimental data dealing with a carbon black, filled natural rubber, issued from uniaxial traction tests, pure shear tests, and tensile tests performed on double-edge notched tensile specimens. 相似文献
68.
van Gelderen Amos; Schoonen Rob; de Glopper Kees; Hulstijn Jan; Simis Annegien; Snellings Patrick; Stevenson Marie 《Canadian Metallurgical Quarterly》2004,96(1):19
The authors report results of a study into the role of components of first-language (L1; Dutch) and second-language (L2; English) reading comprehension. Differences in the contributions of components of L1 and L2 reading comprehension are analyzed, in particular processing speed in L1 and L2. Findings indicate that regression weights of the L1 and L2 components are different. Although correlations between most processing speed components and reading comprehension are substantial, there are no unique contributions to the explanation of either L1 or L2 reading comprehension when linguistic and metacognitive knowledge are accounted for. In addition, L1 reading comprehension is shown to have a large contribution to L2 reading comprehension, supporting theories of L1-L2 transfer of reading skills. Results are discussed from a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
Monika Backhaus-Ricoult Serge Hagège Aurélie Peyrot Patrick Moreau 《Journal of the American Ceramic Society》1994,77(2):423-430
(Al,Cr)2 O3 single crystals and polycrystals were internally reduced at 1873 K in an Al/Al2 O3 buffer for periods of time ranging from 1 to 100 h. The growth kinetics of the reduction scale were measured. The microstructure of the reduction scale was investigated by SEM and TEM. As a result of the reduction, two types of discrete chromium precipitates developed inside the alumina matrix (inside the single crystal or the polycrystalline grains), each one being characterized by a particular morphology (needle or spheroid) and a low-energy orientation relationship with respect to the alumina matrix. In addition, larger precipitates without special orientation relationship developed along the grain boundaries and at the triple junctions of the polycrystais. In the first part of this paper, the precipitate morphology and size are described in terms of the crystallography of the interface between the two crystal structures in relation to the reduction mechanism. In the second part, the global reduction scale growth is analyzed in terms of point defect fluxes across the reduction scale. 相似文献
70.
Patrick Saint-Dizier 《Computational Intelligence》1988,4(2):143-145
This short text introduces this special issue of Computational Intelligence on artificial intelligence in France. After a brief presentation of the structure and the research activities in artificial intelligence in France, we introduce the papers enclosed herein. 相似文献