全文获取类型
收费全文 | 1860篇 |
免费 | 91篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 28篇 |
综合类 | 1篇 |
化学工业 | 541篇 |
金属工艺 | 31篇 |
机械仪表 | 44篇 |
建筑科学 | 50篇 |
矿业工程 | 3篇 |
能源动力 | 56篇 |
轻工业 | 129篇 |
水利工程 | 16篇 |
石油天然气 | 31篇 |
无线电 | 133篇 |
一般工业技术 | 364篇 |
冶金工业 | 203篇 |
原子能技术 | 39篇 |
自动化技术 | 285篇 |
出版年
2023年 | 24篇 |
2022年 | 71篇 |
2021年 | 62篇 |
2020年 | 43篇 |
2019年 | 56篇 |
2018年 | 59篇 |
2017年 | 54篇 |
2016年 | 66篇 |
2015年 | 53篇 |
2014年 | 63篇 |
2013年 | 125篇 |
2012年 | 107篇 |
2011年 | 106篇 |
2010年 | 79篇 |
2009年 | 85篇 |
2008年 | 82篇 |
2007年 | 60篇 |
2006年 | 56篇 |
2005年 | 51篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 35篇 |
2001年 | 28篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 31篇 |
1997年 | 19篇 |
1996年 | 25篇 |
1995年 | 18篇 |
1994年 | 21篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 13篇 |
1985年 | 10篇 |
1984年 | 16篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1979年 | 10篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 19篇 |
1975年 | 11篇 |
1974年 | 21篇 |
1972年 | 10篇 |
1971年 | 13篇 |
1970年 | 10篇 |
1966年 | 20篇 |
排序方式: 共有1954条查询结果,搜索用时 15 毫秒
171.
172.
173.
A modulated force thermomechanical analysis (mf-TMA) and thermodilatometric analysis (TDA) of the green ceramic mixture of kaolin (27 wt.%), Al2O3 (50 wt.%) and feldspar (23 wt.%) up to 1000 °C is presented. The mf-TMA reflects changes during heating the green ceramics with higher sensitivity than TDA. Discrepancies between mf-TMA and TDA revealed that the elastic behavior of the green porcelain samples is determined most importantly by processes on the crystal boundaries (escaping of the water molecules at the low temperatures up to 150 °C and solid state sintering at the temperatures above 450 °C). Processes in the crystal interiors (e.g. dehydroxylation) have a lesser function. Thermodilatometric results depend more on the processes which take place inside the crystals than on the processes on the crystal surfaces. 相似文献
174.
175.
Anton A. Kovalchuk Vitaliy G. Shevchenko Alexander N. Shchegolikhin Polina M. Nedorezova Alla N. Klyamkina Alexander M. Aladyshev 《Journal of Materials Science》2008,43(22):7132-7140
Isotactic polypropylene (iPP) and syndiotactic polypropylene (sPP) nanocomposites containing 0.1–3.5 wt.% multi-wall carbon
nanotubes (MWCNTs) have been synthesized via in situ polymerization method with the use of C2- and Cs- symmetry zirconocenes activated by methylaluminoxane (MAO) in liquid propylene medium. Fracture morphology studies by SEM
reveal different MWCNT dispersion efficiency in various polymer matrices, which arises from the catalytic peculiarities of
the composite synthesis. Considerable Young’s modulus enhancement of iPP and sPP (25–66%) takes place even at low MWCNT loadings
(below 0.5 wt.%). The obtained nanocomposites can find use as efficient electromagnetic shielding materials and microwave
absorbing filters due to relatively low permittivity values and considerable dielectric losses in microwave range. Calorimetry
data demonstrate that MWCNTs exert evident influence as nucleating agents causing the rise of iPP and sPP crystallization
temperature. Considerable retardation effect on iPP thermal oxidative degradation has been observed: the temperature of maximal
weight loss rate rises by ~52 °C upon incorporating only 1.4 wt.% MWCNTs. 相似文献
176.
The supercritical carbon dioxide (S-CO2) Brayton cycle is a promising advanced alternative to the Rankine steam cycle and recuperated gas Brayton cycle for the energy converters of specific reactor concepts belonging to the U.S. Department of Energy Generation IV Nuclear Energy Systems Initiative. A new plant dynamics analysis computer code has been developed for simulation of the S-CO2 Brayton cycle coupled to an autonomous, natural circulation lead-cooled fast reactor (LFR). The plant dynamics code was used to simulate the whole-plant response to accident conditions. The specific design features of the reactor concept influencing passive safety are discussed and accident scenarios are identified for analysis. Results of calculations of the whole-plant response to loss-of-heat sink, loss-of-load, and pipe break accidents are demonstrated. The passive safety performance of the reactor concept is confirmed by the results of the plant dynamics code calculations for the selected accident scenarios. 相似文献
177.
178.
We propose a mathematical model for the Towers of Hanoi and London based on state graphs. The analysis of this model allows to address questions like equivalence of puzzles, difficulty of tasks and optimality of solutions using topological, metric and symmetry properties of the corresponding graphs.The mathematical model serves as a base for a computer program to administer tower puzzles in a variety of psychological test situations. It is suitable for bedside use and is equipped with numerous devices for post-processing of recorded data. Among these features is the graphical representation of the projection of the path taken by a test person onto the state graph. 相似文献
179.
Novel composite materials BaCl2/vermiculite, BaCl2/γ-Al2O3 and BaCl2/(carbon Sibunit) have been synthesised by impregnation of the three porous matrices with barium chloride and studied as ammonia sorbents. Isosters of ammonia sorption are measured at T = 15–80 °C and P = 0.7–9 bar. It was found that a modification of the host matrices by the salt increases the ammonia uptake due to a chemical reaction between ammonia and barium chloride. The enthalpy and entropy of ammonia sorption by the salt confined to the mesopores of alumina and Sibunit are significantly smaller with regard to those for the bulk salt. This indicates that the salt confinement to the small pores allows tuning its sorption properties. In the large vermiculite pores the properties remain unchanged. Based on the experimental isosteric charts, the feasibility of the new materials for adsorptive heat transformation has been analyzed. For composite BaCl2/vermiculite the coefficient of performance (COP) for ice making and air conditioning cycles calculated from the ammonia sorption data can reach 0.6 which seems quite encouraging from a practical point of view. 相似文献
180.
Antonín Minařík Petr Smolka Lubomír Lapčík 《International Journal of Heat and Mass Transfer》2011,54(17-18):4135-4142
Factors determining creation of self-organized structures, Bénar–Marangoni cells, during the process of solvent evaporation from the polymer solution and formation of polymer film were studied. Examined parameters were temperature, temperature gradient, rate of drying, height of a liquid layer, area for film preparation, viscosity, molecular weight distribution, etc. A special apparatus, micro condensation drying system, was engineered for this study. As a model system, hydroxyethyl cellulose aqueous solution was used for its excellent film-forming ability and the tendency to self-aggregation. Experimental results, presented in a wide spectrum of self-organized patterns, show the complexity of the problem and the crucial role of molecular weight distribution of the polymer in the fixation of organized structures under highly non-equilibrium conditions. 相似文献