全文获取类型
收费全文 | 866篇 |
免费 | 53篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 196篇 |
金属工艺 | 11篇 |
机械仪表 | 6篇 |
建筑科学 | 24篇 |
矿业工程 | 6篇 |
能源动力 | 26篇 |
轻工业 | 141篇 |
水利工程 | 2篇 |
无线电 | 51篇 |
一般工业技术 | 149篇 |
冶金工业 | 181篇 |
原子能技术 | 3篇 |
自动化技术 | 105篇 |
出版年
2023年 | 24篇 |
2022年 | 30篇 |
2021年 | 31篇 |
2020年 | 21篇 |
2019年 | 14篇 |
2018年 | 28篇 |
2017年 | 28篇 |
2016年 | 20篇 |
2015年 | 23篇 |
2014年 | 21篇 |
2013年 | 43篇 |
2012年 | 39篇 |
2011年 | 53篇 |
2010年 | 30篇 |
2009年 | 17篇 |
2008年 | 19篇 |
2007年 | 21篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 18篇 |
2001年 | 25篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 58篇 |
1997年 | 35篇 |
1996年 | 27篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1974年 | 4篇 |
1973年 | 5篇 |
排序方式: 共有919条查询结果,搜索用时 15 毫秒
41.
Marius Maximini Philip Engelhardt Martin Brenner Frank Beckmann Oliver Moritz 《International Journal of Hydrogen Energy》2014
Fuel cell systems based on liquid fuels are particularly suitable for auxiliary power generation due to the high energy density of the fuel and its easy storage. Together with industrial partners, Oel-Waerme-Institut is developing a 3 kWel PEM fuel cell system based on diesel steam reforming to be applied as an APU for caravans and yachts. The start-up time of a fuel cell APU is of crucial importance since a buffer battery has to supply electric power until the system is ready to take over. Therefore, the start-up time directly affects the battery capacity and consequently the system size, weight, and cost. 相似文献
42.
Thermostable Binding of Aroma Compounds to Starch. Part 1: Binding by Freeze-Drying. By freeze-drying of aqueous emulsions or suspensions of menthol, pyrazine, thymol, vanillin or peppermint oil and solutions of native or modified starches, amylose, amylopectin Or β-cyclodextrin sorbates were prepared. After heating to 180°C the aroma compounds were bound thermostable and in most cases also stable during extrusion. In general the adsorbed amounts decreased in the order cyclodextrin, amylose, potato starch, waxy maize starch, maize or tapioca starch, wheat starch, amylopectin. Some modified maize starches adsorbed greater amounts than native maize starch. Menthol and thymol were better bound to high-amylose starches, vanillin and pyrazine better to high-amylopectin starches, but vanillin best to cyclodextrin and pyrazine to maltodextrin (DE 4–5). The desorption of the aroma compounds during chewing in the mouth was limited after formation of channel inclusion compounds with amylose. 相似文献
43.
Michael Fellows Jörg Flum Danny Hermelin Moritz Müller Frances Rosamond 《Theory of Computing Systems》2010,46(2):311-339
The classes of the W-hierarchy are the most important classes of intractable problems in parameterized complexity. These classes
were originally defined via the weighted satisfiability problem for Boolean circuits. Here, besides the Boolean connectives
we consider connectives such as majority, not-all-equal, and unique. For example, a gate labelled by the majority connective outputs true if more than half of its inputs are true. For any finite set
C\mathcal{C}
of connectives we construct the corresponding W(
C\mathcal{C}
)-hierarchy. We derive some general conditions which guarantee that the W-hierarchy and the W(
C\mathcal{C}
)-hierarchy coincide levelwise. If
C\mathcal{C}
only contains the majority connective then the first levels of the hierarchies coincide. We use this to show that a variant
of the parameterized vertex cover problem, the majority vertex cover problem, is W[1]-complete. 相似文献
44.
This paper demonstrates the ways in which different Chinese bulk energy transport strategies affect the future steam coal market in China and in the rest of the world. An increase in Chinese demand for steam coal will lead to a growing need for additional domestic infrastructure as production hubs and demand centers are spatially separated, and domestic transport costs could influence the future Chinese steam coal supply mix. If domestic transport capacity is available only at elevated costs, Chinese power generators could turn to the global trade markets and further increase steam coal imports. Increased Chinese imports could then yield significant changes in steam coal market economics on a global scale. This effect is analyzed in China, where coal is mainly transported by railway, and in another setting where coal energy is transported as electricity. For this purpose, a spatial equilibrium model for the global steam coal market has been developed. One major finding is that if coal is converted into electricity early in the supply chain, worldwide marginal costs of supply are lower than if coal is transported via railway. Furthermore, China's dependence on international imports is significantly reduced in this context. Allocation of welfare changes particularly in favor of Chinese consumers while rents of international producers decrease. 相似文献
45.
46.
Curby Timothy W.; Rudasill Kathleen Moritz; Edwards Taylor; Pérez-Edgar Koraly 《Canadian Metallurgical Quarterly》2011,26(2):175
The present study examines the moderating role first grade classroom quality may have on the relations between children's difficult temperament (assessed in infancy) and their academic and social outcomes in early elementary school (first grade). Using data from the National Institute of Child Health and Human Development's Study of Early Child Care and Youth Development, 1032 children were rated by their mothers at 6 months of age on difficult temperament. The quality of first grade classroom environments were then observed and rated along three domains: emotional support, classroom organization, and instructional support. Regression analyses examined the statistical interactions between difficult temperament and classroom quality domains on children's academic and social outcomes. Results indicate high-quality classroom environments may ameliorate the academic and social risks associated with having a difficult temperament. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
47.
A computer simulation of a section of the interior region of a liquid chromatographic column is performed. The detailed fluid flow profile is provided from a microscopic calculation of low Reynolds number flow through a random packed bed of nonporous spherical particles. The fluid mechanical calculations are performed on a parallel processor computer utilizing the lattice Boltzmann technique. Convection, diffusion, and retention in this flow field are calculated using a stochastic-based algorithm. This computational scheme provides for the ability to reproduce the essential dynamics of the chromatographic process from the fundamental considerations of particle geometry, particle size, flow velocity, solute diffusion coefficient, and solute retention parameters when retention is utilized. The simulation data are fit to semiempirical models. The best agreement is found for the "coupling" model of Giddings and the four-parameter Knox model. These models are verified over a wide range of particle sizes and flow velocities at both low and high velocity. The simulations appear to capture the essential dynamics of the chromatographic flow process for non-dimensional flow velocities (Péclet number) less than 500. Since the same packing geometry is utilized for different particle size studies, the interpretation of the parameter estimates from these models can be extended to the physical column model. The simulations reported here agree very well with a number of experiments reported previously. 相似文献
48.
This study was conducted to examine the effect of roasting nonlinted whole cottonseed on ruminal crude protein (CP) degradability and performance in high-yielding dairy cows. Multiparous Israeli Holstein-Friesian cows (parity average 2.5+/-1.5; n = 132) with 571+/-65 kg of body weight (BW), 107+/-48 d in milk (DIM), and 37+/-5.8 kg of milk yield/d were used in the study. Cows were divided into two dietary treatment groups according to their BW, DIM, and milk production. The two diets were similar in CP, net energy for lactation, and neutral detergent fiber content [17%, 1.74 Mcal/kg, and 30% on a dry matter (DM) basis] and included either 15% (on a DM basis) whole cottonseed or roasted whole cottonseed. Ruminal effective degradability of CP, organic matter (OM), and ether extract (EE) decreased 14, 11, and 10%, respectively, compared to whole cottonseed. Total tract digestibilities of CP and EE were similar for both treatments and averaged 57 and 59%, respectively. However, DM and OM digestibilities were 6 and 5% higher in cows offered roasted whole cottonseed relative to those fed whole cottonseed diet. The inclusion of roasted whole cottonseed in the ration decreased ruminal ammonia and blood urea N concentration by 12% compared with diet with the raw whole cottonseed. Milk production, milk fat content, and production, and milk protein yield increased when roasted, nonlinted whole cottonseed was included in the diet. Milk protein content was similar for both treatments, averaging 2.92%. 相似文献
49.
JD Meyer RF Falk RM Kelly JE Shively SJ Withrow WS Dernell DJ Kroll TW Randolph MC Manning 《Canadian Metallurgical Quarterly》1998,87(9):1149-1154
A new method for preparing poly(L-lactide) (PLA) biodegradable beads impregnated with an ionic aminoglycoside, gentamycin, is described. The process employs hydrophobic ion pairing to solubilize gentamycin in a solvent compatible with PLA, followed by precipitation with a compressed antisolvent (supercritical carbon dioxide). The resulting precipitate is a homogeneous dispersion of the ion-paired drug in PLA microspheres. The microspheres are approximately 1 microm in diameter and can be compressed into beads (3-6 mm in diameter) strung on surgical sutures for implantation. The bead strings exhibit no significant change in release kinetics upon sterilization with a hydrogen peroxide plasma (Ster-Rad). The kinetics of gentamycin release from the PLA beads are consistent with a matrix-controlled diffusion mechanism. While nonbiodegradable poly(methyl methacrylate) (PMMA) beads initially release gentamycin in a similar manner, the drug release from PMMA ceases after 8 or 9 weeks, while the PLA beads continue to release drug for over 4 months. Moreover, only 10% of the gentamycin is released from the PMMA beads, while PLA beads release more than 60% of their load, if serum is present in the release medium. The PLA system displays improved release kinetics relative to PMMA, is biodegradable, is unaltered by gas sterilization, can be used for a range of antibiotics, and can be manipulated without disintegration. These are all desirable properties for an implantable drug delivery system for the prevention or treatment of osteomyelitis. 相似文献
50.