全文获取类型
收费全文 | 1879篇 |
免费 | 108篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 10篇 |
综合类 | 2篇 |
化学工业 | 824篇 |
金属工艺 | 36篇 |
机械仪表 | 21篇 |
建筑科学 | 45篇 |
矿业工程 | 7篇 |
能源动力 | 38篇 |
轻工业 | 312篇 |
水利工程 | 9篇 |
石油天然气 | 9篇 |
无线电 | 71篇 |
一般工业技术 | 313篇 |
冶金工业 | 88篇 |
原子能技术 | 2篇 |
自动化技术 | 203篇 |
出版年
2024年 | 6篇 |
2023年 | 38篇 |
2022年 | 197篇 |
2021年 | 193篇 |
2020年 | 55篇 |
2019年 | 60篇 |
2018年 | 76篇 |
2017年 | 60篇 |
2016年 | 71篇 |
2015年 | 57篇 |
2014年 | 83篇 |
2013年 | 138篇 |
2012年 | 96篇 |
2011年 | 121篇 |
2010年 | 95篇 |
2009年 | 95篇 |
2008年 | 108篇 |
2007年 | 56篇 |
2006年 | 70篇 |
2005年 | 58篇 |
2004年 | 49篇 |
2003年 | 30篇 |
2002年 | 39篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
1911年 | 2篇 |
排序方式: 共有1990条查询结果,搜索用时 0 毫秒
991.
Tomas Komprda Radka Burdychová Vlastimil Dohnal Olga Cwiková Pavla Sládková 《European Food Research and Technology》2008,227(1):29-36
Biogenic amines (BA; histamine, tyramine, tryptamine, phenylethylamine, cadaverine) and polyamines (PA; putrescine, spermidine,
spermine) content was determined in Dutch-type semi-hard cheese (ripening 176 days) using an experimental design two producers × two
starter cultures × two fat contents. Content of quantitatively most important BA (tyramine and histamine) and PA (putrescine)
in the cheese samples at the end of ripening varied in the range 5–392 and 22–59, and 1–132 mg kg−1, respectively. Time of ripening accounted for (P < 0.01) 67, 67 and 76% of the explained variability of histamine, tyramine, and putrescine content, respectively. Histamine,
tyramine, and putrescine content in cheese (Y, mg kg−1) increased (P < 0.01) linearly with increasing time of ripening (X, days): Y = 0.24X−1.3 (R
2 = 0.28), Y = 0.69X−18.9 (R
2 = 0.24) and Y = 0.16X−1.3 (R
2 = 0.04), respectively. Biogenic amines (sum of BA) were produced more than three times more rapidly with increasing time
of ripening in the edge part of the cheese than in the core part. Both histamine and tyramine content in cheese was negatively
correlated (P < 0.01) with counts of lactic acid bacteria (LAB) and counts of total anaerobes, respectively. Accordingly, only 3% of both
LAB and enterococci (established tyramine producers) isolates were positive on tyrosine decarboxylase gene sequences using
the PCR method. 相似文献
992.
Johannes Elbs Yuriy M. Bunkov Eddy Collin Henri Godfrin Olga Suvorova Clemens B. Winkelmann 《Journal of Low Temperature Physics》2008,151(3-4):860-864
ULTIMA is a project which proposes to use superfluid 3He as a sensitive medium for direct dark matter search. In this paper we report on new, detailed calibrations of our bolometric
cells as a function of the magnetic field. An influence on the order of 20% on the peak height after an energy deposition
is observed for magnetic fields up to 330 mT. Simultaneous measurements of neutron capture and heater events, releasing both
a well defined energy, show that the effect is similar for both, and that it is possible to maintain a good calibration by
an appropriate correction.
相似文献
993.
Olga Goncharova 《Microgravity science and technology》2008,20(3-4):213-217
The thermal gravitational convection of liquids under conditions of microgravity is studied in a 2D long rectangular domain elongated in the direction of the gravity force. The liquid is located between two solid regions of equal thickness. The solid parts are heat conducting. The mathematical modelling of the coupled problem is presented. Two mathematical models of convection are used to describe a motion of liquid: the classical Oberbeck-Boussinesq model and the microconvection model of isothermally incompressible liquid. The numerical experiments of convection are performed and demonstrate the qualitative and quantitative differences in the flow characteristics. 相似文献
994.
Ordering phenomena in bcc (110) binary thin film intermetallics are studied by a statistical-thermodynamic model. The system is modeled by an Ising approach that includes only nearest-neighbor chemical interactions and is solved in a mean-field approximation. Vacancies and anti-structure atoms are considered on both sublattices. The model describes long-range ordering and simultaneously short-range ordering in the thin film. It is applied to NiAl thin films with B2 structure. Vacancy concentrations, thermodynamic activity profiles and the virtual critical temperature of order-disorder as a function of film composition and thickness are presented. The results point to an important role of vacancies in near-stoichiometric and Ni-rich NiAl thin films. 相似文献
995.
Terrence Lyons Jennifer A. Ickes Victor S. Magar Carl S. Albro Lydia Cumming Brenda Bachman Thomas Fredette Tommy Myers Mike Keegan Ken Marcy Olga Guza 《Canadian Metallurgical Quarterly》2006,132(4):505-514
Capping is a common remediation technology for the containment/stabilization of contaminated sediments. During capping activities, clean material is commonly released from a barge at the water surface and falls through the water column to the sediment surface, providing an uncontaminated surface sediment layer. Little information exists on the potential release of in situ contaminated sediments during and after capping operations. This paper focuses on the measured release of contaminants during capping events at Boston Harbor, Mass. (confined aquatic disposal cells for contaminated sediment) and Eagle Harbor, Wash. (creosote-contaminated sediment from a wood treating facility). The water column was sampled during capping events to evaluate whether cap placement resulted in the release of polycyclic aromatic hydrocarbons (PAH)- or polychlorinated biphenyls (PCB)-contaminated sediments at Boston Harbor, or PAH-contaminated sediments at Eagle Harbor. Though results at both sites indicated some contaminant resuspension during capping operations, in general contaminant resuspension was relatively low for all capping events. PCB and PAH concentrations for most samples were in the low ng/L range. The most significant releases occurred when previously uncapped sediments were initially capped, and the magnitude of contaminant resuspension decreased with successive capping layers. These results may have important implications regarding sediment cap installation techniques and their potential impacts on water quality. Resuspension during capping may be minimized by placing cap material in lifts, where the first lift provides a uniform layer of clean material using techniques that minimize sediment disturbance and subsequent lifts are placed more aggressively once contaminated sediment is covered. 相似文献
996.
Maria Joo Cabrita Ana M Costa Freitas Olga Laureano Rocco Di Stefano 《Journal of the science of food and agriculture》2006,86(6):922-931
In order to evaluate the potential aroma of some Portuguese grapes, several glycosidically bound aroma compounds of ten grape varieties grown in Évora, Alentejo, Portugal, were released, identified and quantified using gas chromatography–mass spectrophotometry. White varieties were Arinto, Perrum, Rabo‐de‐Ovelha, Roupeiro and Antão Vaz. Red varieties were Trincadeira, Aragonez, Tinta Caiada, Moreto and Castelão. Grapes of Roupeiro and Trincadeira from five other vines in the Alentejo region were also studied. For each variety pulp and skin were analyzed separately. The compounds produced by enzymatic hydrolysis of glycoside precursors extracted from pulps and skins of these grapes were similar to the ones appearing in the so‐called ‘aromatic’ varieties; however, the amounts found were significantly lower. These results seem to show the neutral characteristic of these grapes to indicate that each variety has a distinctive profile regarding compounds from the linalool class. The ratios of trans : cis forms of some linalool compounds remain the same in all samples of Roupeiro and Trincadeira, regardless their origin. In Trincadeira grapes no linalool was detected. Skins are always richer than pulps. The acid hydrolysis of norisoprenoid aglycons produced highly odorant compounds previously described in grape varieties. Although some differences between varieties could be detected, the red grapes Aragonez and Castelão are richer in vitispiranes while Moreto, Trincadeira and Tinta Caiada are richer in actinidols; in white grapes, only Roupeiro and Perrum show detectable amounts of vitispiranes. These results need further investigation and analysis to be considered as a statement and should be confirmed in an extended study. Copyright © 2006 Society of Chemical Industry 相似文献
997.
998.
Get'man Olga I. Panichkina Valentina V. Skorokhod Valerii V. 《Powder Metallurgy and Metal Ceramics》2004,43(5-6):236-241
The effect of adding fine scandium oxide (1, 5, and 10 vol.% in relation to the metal) on shrinkage kinetics during sintering of tungsten powder with an average particle size of 4 μm and 140 nm is studied. Specimens of coarse and fine powders are sintered at 1800-2000 and 1000-1200°C, respectively. The results obtained are explained on the basis of the Skorokhod structural model for composite mixtures that takes account of the dimensional factor of components and the level of the matrix microstructure. It is established that the lower the level of the latter and consequently the greater the level of the carcass formation, the greater is the effect of a slowdown in volumetric shrinkage with the same volume content of oxide addition. 相似文献
999.
Teresa Garde-Cerdán A. Robert Marsellés-Fontanet Margaluz Arias-Gil Olga Martín-Belloso Carmen Ancín-Azpilicueta 《Food chemistry》2007,103(3):771-777
The aim of this work was to study the influence of SO2 on the use of nitrogenous compounds by yeast during wine alcoholic fermentation. Thus Parellada must was sterilized by a pulsed electric field treatment and inoculated with Saccharomyces cerevisiae Na33 strain. The fermentations were carried out with SO2 (20 mg/l) and without SO2. Results showed that yeast better consumed the amino acids in the first half of fermentation in the presence of SO2. The final concentration of amino acids in the obtained wine was greater when the must was fermented without SO2 than when the latter compound was present. Therefore, the presence of SO2 facilitated the consumption of amino acids and, hence, such wine should have more complex flavour and better microbiological stability than that obtained from fermentation without SO2. 相似文献
1000.
Fernando Rosa-Velardo Olga Marroquín-Alonso David de Frutos-Escrig 《Electronic Notes in Theoretical Computer Science》2006,150(1):103
The term Ubiquitous Computing was coined by Mark Weiser almost two decades ago. Despite all the time that has passed since Weiser's vision, ubiquitous computing still has a long way ahead to become a pervasive reality. One of the reasons for this may be the lack of widely accepted formal models capable of capturing and analyzing the complexity of the new paradigm. We propose a simple Petri Net based model to study some of its main characteristics. We model both devices and software components as a special kind of coloured Petri Nets, located in locations, that can move to other locations and synchronize with other co-located nets, offering and requesting services. We obtain an amenable model for ubiquitous computing, due to its graphical representation. We present our proposal in a progressive way, first presenting a basic model where coordination is formalized by the synchronized firing of pairs of compatible transitions that offer and request a specific service, and ad hoc networks are modeled by constraining mobility by the dynamic acquisition of locality names. Next, we introduce a mechanism for the treatment of robust security properties, namely the generation of fresh private names, to be used for authentication properties. 相似文献