全文获取类型
收费全文 | 843篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 229篇 |
金属工艺 | 29篇 |
机械仪表 | 21篇 |
建筑科学 | 23篇 |
能源动力 | 28篇 |
轻工业 | 66篇 |
水利工程 | 8篇 |
石油天然气 | 1篇 |
无线电 | 54篇 |
一般工业技术 | 198篇 |
冶金工业 | 110篇 |
原子能技术 | 27篇 |
自动化技术 | 61篇 |
出版年
2023年 | 5篇 |
2022年 | 28篇 |
2021年 | 19篇 |
2020年 | 10篇 |
2019年 | 22篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 11篇 |
2014年 | 30篇 |
2013年 | 58篇 |
2012年 | 44篇 |
2011年 | 57篇 |
2010年 | 43篇 |
2009年 | 46篇 |
2008年 | 41篇 |
2007年 | 44篇 |
2006年 | 30篇 |
2005年 | 37篇 |
2004年 | 27篇 |
2003年 | 22篇 |
2002年 | 21篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 11篇 |
1998年 | 35篇 |
1997年 | 25篇 |
1996年 | 26篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有875条查询结果,搜索用时 15 毫秒
91.
In single-objective optimization problems, with only one optimal design objective, the absolute optimal solution to maximize/minimize the objective function can be determined. However, in most real design problems, the optimization problems are multi-objective, where two or more independent design objectives must be optimized simultaneously, and no single absolute optimal solution necessarily exists. In these cases, it is helpful for designers to recognize the range of alternative solutions that exist in Pareto-optimal sets and choose an acceptable solution from among them. In this paper, the authors carried out multi-objective optimization using Multiple Objective Genetic Algorithms through a real case study involved in indoor environmental design – the design of outer windows. Then the authors analyzed structure of Pareto-optimal solution sets. Here we present the analysis process as well as the case study details, and show how the method proposed here is effective at finding an acceptable solution for multi-objective optimization problems. 相似文献
92.
Haruyuki Makio Takashi Ochiai Hidetsugu Tanaka Terunori Fujita 《Advanced Synthesis \u0026amp; Catalysis》2010,352(10):1635-1640
A bis(phenoxyimine) group 4 transition metal catalyst (now known as FI catalysts) can discern ethylene from a mixture of ethylene and propylene at more than 99% selectivity. Denisty function theory (DFT) calculations revealed a spatially confined reaction site in the transition states of the migratory insertion which is just the right size for an ethylene molecule but too small for a propylene one. The substituents adjacent to the phenoxy‐oxygens are of crucial importance in developing the size/shape‐selectivity. 相似文献
93.
94.
Tetsuya Shishido Tomoyuki Kitano Kentaro Teramura Tsunehiro Tanaka 《Topics in Catalysis》2010,53(7-10):672-677
Nb2O5/Al2O3 catalysts calcined at high temperatures exhibited the Brønsted acid property. A monolayer of niobic acid-like compound, which has distorted octahedral symmetry, was stabilized over 16 wt% Nb2O5/Al2O3 catalyst calcined at 1,173 K. The two-dimensional Nb–O–Nb network of stabilized niobic acid-like compound probably accounts for the generation of Brønsted acid. 相似文献
95.
Dyeing wastewater collected in Kyoto city, Japan, was investigated for the occurrence of aryl hydrocarbon receptor (AhR) ligands by using an AhR-responsive reporter gene assay. Concentrated extracts of wastewater samples elicited a dose-dependent increase in AhR ligand activity, and several hydrophobic HPLC fractions of the extracts were highly effective in inducing AhR ligand activity. Three potential AhR ligands were isolated from these fractions and identified to be Disperse Red 92, Disperse Yellow 64, and 3'-hydroxybenzo[b]quinophthalone by using HPLC and LC-MS/MS. Disperse Red 92, which has also been detected in the treated effluent from a sewage plant receiving the wastewater, is an anthraquinone disperse dye showing weak AhR binding affinity in the assay. Disperse Yellow 64 and 3'-hydroxybenzo[b]quinophthalone are quinoline disperse dyes capable of activating the AhR at nanomolar concentrations. In particular, Disperse Yellow 64 is a highly potent AhR ligand that was 3 times more effective in inducing AhR ligand activity than beta-naphthoflavone in the assay. Quinoline disperse dyes are suggested to be a new class of xenobiotic AhR ligands which pose a danger to aquatic biota and human health. 相似文献
96.
Okanojo M Shiraki K Kudou M Nishikori S Takagi M 《Journal of Bioscience and Bioengineering》2005,100(5):556-561
Protein aggregation is a major obstacle in both biological applications and biomedical fields involving proteins. In this study, we investigated the essential structure of small additives that function as chemical chaperones. Aggregation-suppressing competent additives were 1,3-diaminopropane, 1,4-diaminobutane, and 1,5-diaminopentane, which suppressed aggregation in the given order; whereas no diols or monoamines prevented the thermal aggregation and the inactivation of lysozyme. The heat-inactivation rate of lysozyme with 1,3-diaminopropane was almost identical to that of lysozyme with spermine and arginine ethylester, which are the most prominent additives reported yet. 相似文献
97.
Kentaro Kukita Indra Nur Adisusilo Yoshinari Kamakura 《Journal of Computational Electronics》2014,13(1):264-270
Heat conduction properties in Si nanostructures are analyzed using a Monte Carlo method developed for solving the phonon Boltzmann transport equation. The thermal resistances are evaluated for the systems with various sizes, and the transition from the diffusive to the ballistic heat conduction are investigated. We compare the two different phonon dispersion models (the realistic dispersion relation based on the adiabatic bond charge model and the analytically approximated model), and it is shown that the correct implementation of the phonon dispersion relation is essential to accurately simulate the quasi-ballistic heat conduction properties, which becomes obvious in the structures smaller than the phonon mean free path. 相似文献
98.
Akira Matsugi Hiroumi Shiina Akifumi Takahashi Kentaro Tsuchiya Akira Miyoshi 《Combustion and Flame》2014
The combustion characteristics and reaction mechanism of mixtures containing nitrogen trifluoride (NF3) were investigated. Burning velocities for H2/NF3/N2, CH4/NF3/N2, and C3H8/NF3/N2 flames were determined for the first time at various equivalence ratios and N2 mole fractions. The burning velocities of the latter two flames were similar and showed peaks at equivalence ratios of ∼1.0, while those of the H2/NF3/N2 flames had the pronounced peak at low equivalence ratios where the formation of the wrinkled flames was observed. A detailed kinetic model was constructed to simulate the laminar burning velocities of H2/NF3/N2 and CH4/NF3/N2 flames. The model accurately reproduced the experimental results. Analyses of the reaction mechanism revealed the major reaction pathways that involve the decomposition of NF3, the oxidation and chain-fluoridation of H2 and CH4, and the formation of N2. 相似文献
99.
An experimental study of several types of ground heat exchangers (GHEs) installed in a steel pile foundation, including double-tube, U-tube, and multi-tube GHEs, was carried out at Saga University. Water flows through the heat exchangers and exchanges heat to or from the ground. The performance of GHEs was investigated under actual operation in the cooling mode with flow rates of 2, 4, and 8 l/min. Temperatures of the ground and GHE tube wall were measured to find the temperature distributions according to the depth of the ground and depth of the GHE tube wall. The temperatures of the inlet and outlet of circulated water were also measured to calculate the heat exchange rate. The double-tube had the highest heat exchange rate, followed by the multi-tube and U-tube GHEs. For example, the average heat exchange rate of GHEs over 24 h of continuous operation with a flow rate of 4 l/min was 49.6 W/m for the double-tube, 34.8 W/m for the multi-tube, and 30.4 W/m for the U-tube. An increasing flow rate increased the heat exchange rate of the GHEs. The heat exchange rates increased significantly for flow rate increases from 2 to 4 l/min, but only slightly changed from 4 to 8 l/min. 相似文献
100.
This study measured air exchange rates, indoor concentrations of aldehydes and volatile organic compounds (VOCs), and radioactivity levels at 19 temporary houses in different temporary housing estate constructed in Minamisoma City following the Great East Japan Earthquake. The 19 surveyed houses represented all of the companies assigned to construct temporary houses in that Minamisoma City. Data were collected shortly after construction and before occupation, from August 2011 to January 2012. Mean air exchange rates in the temporary houses were 0.28/h, with no variation according to housing types and construction date. Mean indoor concentrations of formaldehyde, acetaldehyde, toluene, ethylbenzene, m/p‐xylene, o‐xylene, styrene, p‐dichlorobenzene, tetradecane, and total VOCs (TVOCs) were 29.2, 72.7, 14.6, 6.35, 3.05, 1.81, 7.29, 14.3, 8.32, and 901 μg/m3, respectively. The levels of acetaldehyde and TVOCs exceeded the indoor guideline (48 μg/m3) and interim target (400 μg/m3) in more than half of the 31 rooms tested. In addition to guideline chemicals, terpenes (α‐pinene and d‐limonene) and acetic esters (butyl acetate and ethyl acetate) were often detected in these houses. The indoor radiation levels measured by a Geiger–Müller tube (Mean: 0.22 μSv/h) were lower than those recorded outdoors (Mean: 0.42 μSv/h), although the shielding effect of the houses was less than for other types of buildings. 相似文献