全文获取类型
收费全文 | 518篇 |
免费 | 25篇 |
专业分类
电工技术 | 10篇 |
综合类 | 1篇 |
化学工业 | 150篇 |
金属工艺 | 7篇 |
机械仪表 | 6篇 |
建筑科学 | 30篇 |
矿业工程 | 7篇 |
能源动力 | 7篇 |
轻工业 | 37篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 35篇 |
一般工业技术 | 89篇 |
冶金工业 | 69篇 |
原子能技术 | 3篇 |
自动化技术 | 85篇 |
出版年
2023年 | 2篇 |
2022年 | 16篇 |
2021年 | 32篇 |
2020年 | 14篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 7篇 |
2014年 | 23篇 |
2013年 | 33篇 |
2012年 | 36篇 |
2011年 | 37篇 |
2010年 | 22篇 |
2009年 | 21篇 |
2008年 | 34篇 |
2007年 | 26篇 |
2006年 | 12篇 |
2005年 | 13篇 |
2004年 | 12篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1984年 | 3篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1970年 | 4篇 |
1969年 | 3篇 |
1967年 | 2篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1961年 | 2篇 |
排序方式: 共有543条查询结果,搜索用时 15 毫秒
91.
92.
Thermoneutrality results in prominent diet‐induced body weight differences in C57BL/6J mice,not paralleled by diet‐induced metabolic differences 下载免费PDF全文
93.
Petrocelli John V.; Percy Elise J.; Sherman Steven J.; Tormala Zakary L. 《Canadian Metallurgical Quarterly》2011,100(1):30
Counterfactual thoughts typically take the form of implied or explicit if–then statements. We propose that the multiplicative combination of “if likelihood” (the degree to which the antecedent condition of the counterfactual is perceived to be likely) and “then likelihood” (the perceived conditional likelihood of the outcome of the counterfactual, given the antecedent condition) determine the strength and impact of counterfactuals. This construct, termed counterfactual potency, is a reliable predictor of the degree of influence of counterfactual thinking upon judgments of regret, causation, and responsibility. Through 4 studies, we demonstrate the predictive power of this construct in a variety of contexts and show that it plays a causal role in determining the strength of the effects of counterfactual thought. Implications of counterfactual potency as a central factor of counterfactual influence are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
Gao Y Talgorn E Aerts M Trinh MT Schins JM Houtepen AJ Siebbeles LD 《Nano letters》2011,11(12):5471-5476
PbSe quantum-dot solids are of great interest for low cost and efficient photodetectors and solar cells. We have prepared PbSe quantum-dot solids with high charge carrier mobilities using layer-by-layer dip-coating with 1,2-ethanediamine as substitute capping ligands. Here we present a time and energy resolved transient absorption spectroscopy study on the kinetics of photogenerated charge carriers, focusing on 0-5 ps after photoexcitation. We compare the observed carrier kinetics to those for quantum dots in dispersion and show that the intraband carrier cooling is significantly faster in quantum-dot solids. In addition we find that carriers diffuse from higher to lower energy sites in the quantum-dot solid within several picoseconds. 相似文献
95.
Wilson PR Roschuk T Dunn K Normand EN Chelomentsev E Zalloum OH Wojcik J Mascher P 《Nanoscale research letters》2011,6(1):168
Silicon nanoclusters (Si-ncs) embedded in silicon nitride films have been studied to determine the effects that deposition
and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed
from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different
types of chemical vapour deposition systems. Photoluminescence (PL) experiments revealed broad, tunable emissions with peaks
ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition
and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra
from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and
growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further
increased. X-ray absorption near edge structure at the Si K- and L3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host
matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra. 相似文献
96.
Fuchs Stefan Leveles Laszlo Seshan K. Lefferts Leon Lemonidou Angeliki Lercher Johannes A. 《Topics in Catalysis》2001,15(2-4):169-174
The oxidative dehydrogenation and cracking of ethane and propane over LiDyMg mixed oxides is reported. High yields of olefins and only moderate formation of carbon oxides was observed. Both are primary products that hardly interconvert under the reaction conditions used. Addition of chloride increases the rate of reaction, while slightly decreasing the selectivity to olefins. The addition of carbon dioxide strongly decreases the rate of reaction, the negative order of 0.5 indicating that two active Li+sites are blocked by the adsorption of one CO2molecule. The reaction proceeds at low oxygen pressure primarily via elimination of dihydrogen, while at higher oxygen partial pressure the hydrogen elimination occurs via water formation. It is speculated that dehydrogenation and cracking involve Li+and a rather nucleophilic oxygen site. 相似文献
97.
Laszlo J. Kecskes Bradley R. Klotz Kyu C. Cho Robert J. Dowding Matthew D. Trexler 《Metallurgical and Materials Transactions A》2001,32(11):2885-2893
Fine-grained, high-density (97+ pct of theoretical density (TD)), 80W-20Cu wt pct (58W-42Cu at. pct) composites have been
prepared using nonconventional alloying techniques. The W and Cu precursor powders were combined by a high-energy ball-milling
procedure in air or hexane. The mechanically alloyed W+Cu powder mixtures were then cold pressed into green compacts and sintered
at 1523 K. The milling medium and milling time were varied to increase product densities with a concomitant order-of-magnitude
decrease in grain size. For densification, air was found to be a more effective medium than hexane. From microhardness measurements,
it was concluded that the W-Cu alloys were dispersion and solution hardened, but were sensitive to entrapped residual impurities.
X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron micros-copy (SEM) analyses were
used to demonstrate that the as-milled and sintered W-Cu alloy structures were metastable, decomposing into the starting W
and Cu components upon heating at or above 723 K. 相似文献
98.
Coma V Portes E Gardrat C Richard-Forget F Castellan A 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2011,28(2):218-225
Many plant pathogens produce toxic metabolites when growing on food and feed. Some antioxidative components seem to prevent fungal growth and mycotoxin formation. Recently, we synthesized a new class of powerful antioxidative compounds, i.e. tetrahydrocurcuminoids, and its structure/antioxidant activity relationships have been established. The South West of France produces large amounts of corn, which can be infected by Fusarium species, particularly F. proliferatum. In this context, the efficiency of tetrahydrocurcuminoids, which can be obtained from natural curcuminoids, was investigated to control in vitro the growth of F. proliferatum and the production of its associated mycotoxin, fumonisin B?. The relation between structure and antifungal activity was studied. Tetrahydrocurcumin (THC1), with two guaiacyl phenolic subunits, showed the highest inhibitory activity (measured as radial growth on agar medium) against the F. proliferatum development (67% inhibition at a concentration of 13.6 μmol ml?1). The efficiencies of THC2 (36% at a concentration of 11.5 μmol ml?1), which contains syringyl phenolic units, and THC3 (30% at a concentration of 13.6 μmol ml?1), which does not have any substituent on the aromatic rings, were relatively close. These results indicate that the simultaneous presence of guaiacyl phenols and the enolic function of the β-diketone moiety play an important role in the inhibition mechanisms. The importance of this combination was confirmed using n-propylguaiacol and acetylacetone as molecular models. Under the same conditions, ferulic acid and eugenol, other natural phenolic antioxidants, were less efficient in inhibiting fungal growth. THC1 also reduced fumonisin B? production in liquid medium by approximately 35, 50 and 75% at concentrations of 0.8, 1.3, and 1.9 μmol ml?1, respectively. These very low inhibitory concentrations show that tetrahydrocurcuminoids could be one of the most promising biobased molecules for the control of mycotoxinogen fungal strains. 相似文献
99.
Generally, static var generators function as variable reactances (capacitive or inductive impedances) or controllable ac current and voltage sources. Possible methods of var generation and control by static thyristor circuits are reviewed, and new approaches are described in which power frequency changers (cycloconverters) are employed. Oscillographic recordings illustrate the operation and performance of practical systems, including a 35-Mvar arc furnace compensator. 相似文献
100.
Laszlo Szathmary Petko Valtchev Amedeo Napoli Robert Godin Alix Boc Vladimir Makarenkov 《Annals of Mathematics and Artificial Intelligence》2014,70(1-2):81-105
In pattern mining and association rule mining, there is a variety of algorithms for mining frequent closed itemsets (FCIs) and frequent generators (FGs), whereas a smaller part further involves the precedence relation between FCIs. The interplay of these three constructs and their joint computation have been studied within the formal concept analysis (FCA) field yet none of the proposed algorithms is scalable. In frequent pattern mining, at least one suite of efficient algorithms has been designed that exploits basically the same ideas and follows the same overall computational schema. Based on an in-depth analysis of the aforementioned interplay that is rooted in a fundamental duality from hypergraph theory, we propose a new schema that should enable for a more parsimonious computation. We exemplify the new schema in the design of Snow-Touch, a concrete FCI/FG/precedence miner that reuses an existing algorithm, Charm, for mining FCIs, and completes it with two original methods for mining FGs and precedence, respectively. The performance of Snow-Touch and of its closest competitor, Charm-L, were experimentally compared using a large variety of datasets. The outcome of the experimental study suggests that our method outperforms Charm-L on dense data while on sparse one the trend is reversed. Furthermore, we demonstrate the usefulness of our method and the new schema through an application to the analysis of a genome dataset. The initial results reported here confirm the capacity of the method to focus on significant associations. 相似文献