全文获取类型
收费全文 | 4999篇 |
免费 | 170篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 63篇 |
综合类 | 2篇 |
化学工业 | 1240篇 |
金属工艺 | 76篇 |
机械仪表 | 113篇 |
建筑科学 | 231篇 |
矿业工程 | 7篇 |
能源动力 | 175篇 |
轻工业 | 367篇 |
水利工程 | 28篇 |
石油天然气 | 11篇 |
无线电 | 579篇 |
一般工业技术 | 856篇 |
冶金工业 | 546篇 |
原子能技术 | 61篇 |
自动化技术 | 820篇 |
出版年
2022年 | 55篇 |
2021年 | 81篇 |
2020年 | 47篇 |
2019年 | 61篇 |
2018年 | 85篇 |
2017年 | 102篇 |
2016年 | 125篇 |
2015年 | 88篇 |
2014年 | 113篇 |
2013年 | 254篇 |
2012年 | 213篇 |
2011年 | 258篇 |
2010年 | 212篇 |
2009年 | 222篇 |
2008年 | 212篇 |
2007年 | 219篇 |
2006年 | 223篇 |
2005年 | 162篇 |
2004年 | 174篇 |
2003年 | 142篇 |
2002年 | 147篇 |
2001年 | 111篇 |
2000年 | 103篇 |
1999年 | 82篇 |
1998年 | 159篇 |
1997年 | 136篇 |
1996年 | 110篇 |
1995年 | 103篇 |
1994年 | 97篇 |
1993年 | 84篇 |
1992年 | 55篇 |
1991年 | 40篇 |
1990年 | 50篇 |
1989年 | 44篇 |
1988年 | 46篇 |
1987年 | 45篇 |
1986年 | 26篇 |
1985年 | 79篇 |
1984年 | 58篇 |
1983年 | 55篇 |
1982年 | 46篇 |
1981年 | 80篇 |
1980年 | 46篇 |
1979年 | 50篇 |
1978年 | 17篇 |
1977年 | 37篇 |
1976年 | 44篇 |
1975年 | 41篇 |
1974年 | 30篇 |
1973年 | 26篇 |
排序方式: 共有5175条查询结果,搜索用时 0 毫秒
141.
142.
Lu Shen Jianming Xue Michel W. Barsoum Qing Huang 《Journal of the American Ceramic Society》2014,97(12):3721-3724
Inspired by pressure resistance welding of metallic materials, herein we describe how two MAX phases—Ti3SiC2 and Ti3AlC2—were successfully joined by a rapid electric current heating method in a pulsed electric current sintering furnace. No welding agent was employed and the total processing time was less than 6 min. When the bulk temperature of the joint couple exceeded 1070°C, good joints, with shear strength above 50 MPa, were achieved in both homo‐ and heterojunction joints. 相似文献
143.
Zhenzhen Li Loic D'eramo Fabrice Monti Anne-Laure Vayssade Benjamin Chollet Bruno Bresson Yvette Tran Michel Cloitre Patrick Tabeling 《Israel journal of chemistry》2014,54(11-12):1589-1601
The goal of this paper is to review progress (mostly recent) made in micro and nanovelocimetry, focusing on two techniques: µPIV (microparticle image velocimetry) and nanoPTV (nanoparticle tracking velocimetry). The paper focuses on the measurement of slippage (taken as a benchmark for these techniques), concentrating on work done in our group. We review the developments of µPIV that led, in the last ten years, to the achievement of 100 nm accuracy in the measurement of slip lengths. Later, this approach was complemented by nanoPTV, which recently obtained ±5 nm precision. Here, we also mention recent application of these techniques toward better characterization of microgel and polymer flows. As a whole, the two techniques have conveyed valuable information on flow behavior within and close to the boundaries of microchannels, on the importance of wetting, and on the role of surface heterogeneities. µPIV is commercially available but nanoPTV is not mature. Interesting instrumental developments are expected in the future for the latter technique. 相似文献
144.
Chamekh Ould M'bareck Michel Metayer Dominique Langevin Sadok Roudesli 《应用聚合物科学杂志》1996,62(1):161-165
The miscibility of poly(vinyl alcohol) (PVA) and poly(styrenesulfonic acid) (PSSA) in dilute aqueous solutions was studied by a viscosimetric method. At a constant molecular weight of PSSA, it was found that the miscibility of both polymers increases with the molecular weight and the number of acetate groups of the PVA samples (1 and 12% unhydrolyzed sites). Moreover, this miscibility increases slightly with the total mixture concentration in the interval 1–2 g/dL. By comparison of the results of reduced viscosity of PVA/PSSA and PVA/poly(sodium styrenesulfonate) (PSSNa) mixtures, it has been deduced that the miscibility of two polymers is due mainly to intermolecular interactions between the hydroxyl and sulfonic groups of PVA and PSSA, respectively. These groups act as acceptors and donors of hydrogen bonds which are the responsible for polymers' miscibility. © 1996 John Wiley & Sons, Inc. 相似文献
145.
Jean-Luc Caillaud Stphane Deguillaume Michel Vincent Jean-Claude Giannotta Jean-Michel Widmaier 《Polymer International》1996,40(1):1-7
The addition of metallic fillers is recognized to impart improvement of acoustic properties to polyurethane-based materials used for marine applications. The system under consideration was obtained by the reaction of a triisocyanateterminated prepolymer with 1,4-butanediol, in the presence of various concentrations of lead powder. With increasing lead content, gelation time is reduced and an Einstein-type law does not apply. The kinetics of the reaction were determined by Fourier transform infrared spectroscopy. Deviation from the classic second order is observed for the filled systems, and the higher the lead content, the more important the deviation is, showing undoubtedly the catalytic effect of the metallic powder. 相似文献
146.
Addition of natural clay materials in intumescent polypropylene-based formulations (additive: ammonium polyphosphate and pentaerythritol) leads either to a decrease or to an increase of their fire retardant performances versus the chemical or the physical characteristics of the clay materials. A study of the factors affecting these performances has been carried out using linear and principal components analysis. This analysis shows that the results of the evaluation tests (LOI and UL 94) are affected in different ways by the adduct of the different clay material and that an increase in the LOI is not necessarily related to an increase in the UL 94 classification. LOI values are improved by the presence of the montmorillonite and of illite clay minerals which may react with acidic phosphate to form active carbonization catelysts, in addition, the results of the LOI test are improved by the presence of quartz and other foreign minerals in the clay materials. This study discusses the part played by the different constitutive minerals in the formation of defects in the polymer chain during the mixing process. It is proposed that the presence of these defects leads to a change in fire retardant performance. 相似文献
147.
Eric Ongareau Michel Aubourg Juan J. Obregon Michel Gayral Renato G. Bosisio 《International Journal of Numerical Modelling》1994,7(5):309-319
This paper describes a rigorous and systematic procedure to derive a non-linear distributed FET model that an easily be implemented in CAD routines of simulators based on harmonic balance techniques. The new model is derived from a knowldge of the conventional linear lumped equivalent circuit, from non-linear current sources extracted with pulsed measurements, and from the physical dimensions of the FET. For fundamental and haromonic requencies, the FET is modelled by N identical cells. Each cell is made up of a non-linear two-port section inserted between two linear four-port sections that simulate the coupling and the distributed effects along the electrodes of the FET in the width direction only. This non-linear distributed scaling approach to FET modelling has been applied to the analysis of a submicrometre-gate GaAs FET at Millimetre-wave frequencies, and the results were compared to the non-linear lumped element approach. This approach can be applied to other transistors used in non-linear regions at microwave and millimetre-wave frequencies. 相似文献
148.
We developed a simple solution mixing and molding process for the incorporation of graphene nano-flakes (GNFs) in polymer films. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(ethylene-co-methacrylic acid) (PEMAA) were used for preparation of the samples. The orientation and stacking of GNFs were confirmed using a scanning electron microscope. The thermal conductivity values for these composites were obtained using (1) laser flash method (commercially available) and (2) an optothermal Raman (OTR) technique (homemade device). The former measures the thermal diffusivity (α) and one needs to measure the density (ρ) and the heat capacity (Cp) of the composites in order to measure the in-plane thermal conductivity (κ = α.ρ.Cp), while the latter measures the in-plane thermal conductivity directly from the relation between the excitation power and the position of the Raman resonance. The data obtained from Raman spectroscopy were analyzed, assuming heat propagation in three and two dimensions. The Raman results obtained based on the two-dimensional model were very close to the results obtained using the laser flash method with less than 10% difference. The OTRspectroscopy was found to be a promising technique for measuring the in-plane thermal conductivity of carbon-based polymer composites. PVDF-HFP and PEMAA composite films with very high in-plane thermal conductivity (25 W m−1 K−1) were obtained through the incorporation of GNFs (20 wt % concentration). Considering a very low thermal conductivity of these polymers (<0.2 W m−1 K−1), this corresponds to a large enhancement of roughly 12 400%. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48927. 相似文献
149.
150.
Slim Abdelkafi Benjamin Fouquet Nathalie Barouh Sophie Durner Michel Pina Frantz Scheirlinckx Pierre Villeneuve Frédéric Carrière 《Food chemistry》2009
High levels of lipase activity are known to occur in Carica papaya latex, and this activity is being used in some biotechnological applications. The lipolytic activity of C. papaya lipase (CPL) on dietary triacylglycerols (TAG) has not yet been studied. Hence, the aim of this study was to characterise the specific activity of CPL on dietary TAG present in a crude preparation. Also, we have determined its stability during the lipolysis of a test meal at various pH values mimicking those occurring in the gastro-intestinal tract, with or without bile, and have compared these properties with those of porcine pancreatic extract (PPE) and human pancreatic lipase (HPL). CPL showed maximum stability at pH 6.0, both with and without bile. Some residual activity was still observed at pH 2 (20%), whereas the pancreatic lipases tested were immediately completely inactivated at this pH. In the absence of bile, the highest specific activities were measured at pH 6 in the case of CPL, PPE and HPL. Adding bile slightly decreased the CPL activity in the 4–6 pH range, thus shifting the optimum CPL activity to pH 7, where the presence of bile had no effect. Lipolysis levels decreased with the pH, but CPL was still more active than PPE at pH 5 on a relative basis. These results suggest that CPL might be a promising candidate for use as a therapeutic tool on patients with pancreatic exocrine insufficiency. 相似文献