全文获取类型
收费全文 | 1216篇 |
免费 | 112篇 |
专业分类
电工技术 | 10篇 |
综合类 | 2篇 |
化学工业 | 411篇 |
金属工艺 | 10篇 |
机械仪表 | 47篇 |
建筑科学 | 29篇 |
能源动力 | 17篇 |
轻工业 | 308篇 |
水利工程 | 4篇 |
石油天然气 | 5篇 |
无线电 | 50篇 |
一般工业技术 | 170篇 |
冶金工业 | 133篇 |
原子能技术 | 12篇 |
自动化技术 | 120篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 59篇 |
2021年 | 81篇 |
2020年 | 34篇 |
2019年 | 56篇 |
2018年 | 55篇 |
2017年 | 57篇 |
2016年 | 53篇 |
2015年 | 42篇 |
2014年 | 45篇 |
2013年 | 83篇 |
2012年 | 63篇 |
2011年 | 91篇 |
2010年 | 58篇 |
2009年 | 47篇 |
2008年 | 55篇 |
2007年 | 52篇 |
2006年 | 34篇 |
2005年 | 31篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 16篇 |
2001年 | 23篇 |
2000年 | 6篇 |
1999年 | 17篇 |
1998年 | 39篇 |
1997年 | 36篇 |
1996年 | 21篇 |
1995年 | 17篇 |
1994年 | 11篇 |
1993年 | 15篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1328条查询结果,搜索用时 575 毫秒
101.
María Elena Escuderos Marino Uceda Sebastián Sánchez Antonio Jiménez 《European Journal of Lipid Science and Technology》2007,109(5):536-546
At present, two systems have been usually used to identify olive oil aroma: the official panel test, according to the European Union Regulation [1], and the gas chromatographic method and its improvements. However, both types of techniques have two principal disadvantages: They need a long time for analysis and cannot be applied on‐line. Recently, there has been increasing interest in the development of a new device, the so‐called “electronic nose”. The aim of this work is to perform both a review of these techniques used for olive oil sensory analysis and their advantages and disadvantages. 相似文献
102.
María C. Caracoche Jorge A. Martinez Patricia C. Rivas Fernanda Andreola Federica Bondioli Anna Maria Ferrari Tiziano Manfredini 《Journal of the American Ceramic Society》2008,91(7):2357-2359
This paper deals with the phase stability of an aqueous suspension of tetragonal Zr0.9 Pr0.1 O2 (20 wt%/vol%) at room temperature as a function of the aging time. The suspension is investigated in situ using the highly localized Perturbed Angular Correlations technique. The results indicate that an almost fully reversible degradation process toward monoclinic zirconia takes place through a first-order reaction of rate constant k =0.7 day−1 . Two successive diffusion mechanisms are observed that are interpreted as OH− ions' migration in the grain surface and then, as proton defects' diffusion into the bulk. 相似文献
103.
S De Marino M Iorizzi F Zollo L Minale CD Amsler BJ Baker JB McClintock 《Canadian Metallurgical Quarterly》1997,60(10):959-966
A total of 19 steroids, of which 13 steroidal oligoglycosides (nine new and four known) and six polyhydroxylated steroids (four new and two known), has been isolated from the Antarctic starfish Acodontaster conspicuus. The mixture is dominated by glycosides composed of steroidal aglycons having the hydroxyl groups typically disposed on one side of the tetracyclic nucleus, i.e., 3 beta,4 beta,6 alpha,8,15 beta-, with some having a sulfate at C-6, and differing in the side chains and/or in the disaccharide moieties that are usually attached at C-26, with some at C-28 and C-29. Those compounds are accompanied by minute amounts of glycosides with a delta 8(14)-double bond in the steroid, which is a structural feature not previously found among polyhydroxysteroids derived from starfish. Small amounts of six related unglycosidated polyhydroxysteroids and three higher-molecular-weight asterosaponins complete the composition of the mixture. The structures of the new compounds were determined by interpretation of their spectral data and by comparison with spectral data of known compounds. Eighteen of these compounds were evaluated for their ability to inhibit growth in Antarctic marine bacteria isolated from either the water column or the surfaces of benthic marine invertebrates. Of these compounds, 50% were active against at least one Antarctic marine bacterium. This suggests that these compounds may play an important role in deterring microbial fouling. 相似文献
104.
Plane inertial gravity currents running over horizontal permeable surfaces are studied. An analytical simple model based on local and global balances is derived which describes the propagation and infiltration of an incompressible dense fluid on and through the surface. Results of laboratory experiments are presented which are in accordance with scaling laws suggested analytically. It is found that the loss of mass, the velocity, and the position of the front of the current follow exponential relationships. The dynamics is governed by a particular decay time related to the initial volume released and reduced gravity g0′. However this decay time exhibits a different functional relationship from that obtained for currents evolving over thin permeable bottoms when the downward flow is viscous. As a consequence of the loss of mass, the distance to extinction of the current is found to be independent of g0′. 相似文献
105.
We propose two architectures for the direct two-dimensional (2-D) discrete wavelet transform (DWT). The first one is based on a modified recursive pyramid algorithm (MRPA) and performs a “"nonstandard” decomposition (i.e., Mallat's (1989) tree) of an N×N image in approximately 2N2/3 clock cycles (ccs). This result consistently speeds up other known architectures that commonly need approximately N2 ccs. Furthermore, the proposed architecture is simpler than others in terms of hardware complexity. Subsequently, we show how “symmetric”/“anti-symmetric” properties of linear-phase wavelet filter bases can be exploited in order to further reduce the VLSI area. This is used to design a second architecture that provides one processing unit for each level of decomposition (pipelined approach) and performs a decomposition in approximately N2/2 ccs. In many practical cases, even this architecture is simpler than general MRPA-based devices (having only one processing unit) 相似文献
106.
When local stabilization of nonlinear systems is achieved by linear feedback, the resulting stability region may vanish as the feedback gains increase. This is demonstrated by examples in which neglected nonlinearities create an unstable limit cycle around an asymptotically stable equilibrium. As the feedback gains tend to infinity the unstable limit cycle shrinks to the equilibrium. If a feedback linearization design is applied, the same instability mechanism may occur when the nonlinearities are not precisely known. 相似文献
107.
In this work a high-k insulating film is deposited on the SiO2 tunnel oxide of MOS capacitors designed for non-volatile memory applications. The advantages of this approach derive from the asymmetric band diagram, which lowers the Fowler–Nordheim tunnel erase barrier, without affecting the program operation. This results in lower erase voltage and much shorter erase times. In fact, in the proposed structure the erase voltage is about 20% lower and the erase current three thousands times greater than in conventional MOS with pure-SiO2 tunnel oxide and the same equivalent oxide thickness (15 nm). At the same time, the larger physical thickness prevents from charge loss, and guarantees data retention. The goal of such device is to improve the memory performances without degrading reliability. 相似文献
108.
Ioan Cristian Trelea Fernanda Fonseca Stéphanie Passot Denis Flick 《Drying Technology》2015,33(15-16):1849-1858
Monitoring partial vapor pressure in the freeze-drying chamber is a cheap, global, and non-intrusive way to assess the end of the primary drying stage. Most existing dynamic freeze-drying models which predict this partial pressure describe mass transfer between the product and the condenser via a mass transfer resistance or a mass transfer coefficient. Experimental evidence suggests that such models can be significantly in error for some values of the sublimation flux, leading to physically inconsistent predictions and possibly incorrect assessment of primary drying termination, with potential risk of product damage if moving to secondary drying and increasing shelf temperature while some ice is still present. Assuming a binary gas transport model for vapor and inert gas leads to improved and consistent predictions and explains the apparent variation of the mass transfer resistance with total pressure, shelf temperature, and product sublimation area. 相似文献
109.
Renato Martins da Silva Bárbara Della Noce Camila Fernanda Waltero Evenilton Pessoa Costa Leonardo Araujo de Abreu Naftaly Wang’ombe Githaka Jorge Moraes Helga Fernandes Gomes Satoru Konnai Itabajara da Silva Vaz Jr. Kazuhiko Ohashi Carlos Logullo 《International journal of molecular sciences》2015,16(1):1821-1839
110.
Angela Longo do Nascimento Fernanda Hoffmann Busanello Marcus Vinícius Reis Só Milton Carlos Kuga Jefferson Ricardo Pereira Fabiana Soares Grecca 《Microscopy research and technique》2015,78(6):495-499
The aim of this study was to evaluate the presence of residues of sodium hypochlorite gel, chlorhexidine gel, and EDTA gel on dentinal walls after canal preparation through chemical SEM‐ elemental chemical microanalysis (EDS) analysis. Forty‐eight single‐rooted teeth were selected. They had their crowns sectioned and were instrumented with a reciprocating system. The canals were irrigated with 5 mL of saline solution during root canal preparation. After instrumentation, the root canals were irrigated with 3 mL 17% EDTA followed by 1 min of ultrasonic passive activation (3× 20 sec) to remove the smear layer, and then irrigated with 3 mL of saline solution. The specimens were randomized into three groups (n = 12) according to the chemical substance that filled the root canal for 30 min: GI: 5.5% sodium hypochlorite gel; GII: 2% chlorhexidine gel; GIII: 24% EDTA gel; Negative control group: no substance was used. Then, the root canals were irrigated with 6 mL of saline solution followed by 1 min of ultrasonic passive activation (3× 20 sec). After ultrasonic activation, the canals were irrigated with 2 mL saline. The roots were sectioned, and the percentage of each chemical element present in the samples was analyzed through chemical SEM‐EDS microanalysis. All experimental groups showed a significantly higher percentage of chemical elements (Na and/or Cl) than the control group (P < 0.03). This in vitro study has shown that, regardless of chemical solutions used even after the final irrigation protocol, chemical residues of different substances remained attached to the root canal walls. Microsc. Res. Tech. 78:495–499, 2015. © 2015 Wiley Periodicals, Inc. 相似文献