全文获取类型
收费全文 | 2287篇 |
免费 | 151篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 47篇 |
综合类 | 6篇 |
化学工业 | 671篇 |
金属工艺 | 60篇 |
机械仪表 | 60篇 |
建筑科学 | 147篇 |
矿业工程 | 2篇 |
能源动力 | 50篇 |
轻工业 | 165篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 186篇 |
一般工业技术 | 487篇 |
冶金工业 | 153篇 |
原子能技术 | 10篇 |
自动化技术 | 388篇 |
出版年
2022年 | 29篇 |
2021年 | 49篇 |
2020年 | 32篇 |
2019年 | 44篇 |
2018年 | 50篇 |
2017年 | 66篇 |
2016年 | 67篇 |
2015年 | 76篇 |
2014年 | 88篇 |
2013年 | 131篇 |
2012年 | 110篇 |
2011年 | 165篇 |
2010年 | 103篇 |
2009年 | 105篇 |
2008年 | 123篇 |
2007年 | 110篇 |
2006年 | 101篇 |
2005年 | 79篇 |
2004年 | 59篇 |
2003年 | 63篇 |
2002年 | 42篇 |
2001年 | 41篇 |
2000年 | 43篇 |
1999年 | 40篇 |
1998年 | 51篇 |
1997年 | 42篇 |
1996年 | 42篇 |
1995年 | 33篇 |
1994年 | 21篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 25篇 |
1985年 | 20篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1976年 | 15篇 |
1974年 | 12篇 |
1973年 | 11篇 |
1970年 | 10篇 |
排序方式: 共有2440条查询结果,搜索用时 15 毫秒
81.
Busarakorn Mahayothee Nilobon Komonsing Pramote Khuwijitjaru Marcus Nagle Joachim Müller 《International Journal of Food Science & Technology》2019,54(2):460-470
In this study, drying of red-fleshed dragon fruit at different temperatures (40, 50, 60, 70 and 80 °C) and air velocities (1.0 and 1.5 m s−1) was conducted under the specific humidity of 25 g H2O kg−1 dry air. The results showed that drying at higher temperatures resulted in shorter drying times. However, temperature and air velocity did not significantly affect the total betacyanin contents and antioxidant capacities in dried products. Seven betacyanins identified by LC-MS were betanin, isobetanin, phyllocactin, isophyllocactin, betanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside, isobetanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside and decarboxylated phyllocactin. In addition, the temperature increased the isomerisation of betacyanins. The most preferable condition for preserving the colour and betacyanin contents of red-fleshed dragon fruit was the drying at a temperature of 80 °C and air velocity of 1.5 m s−1 since it could shorten the drying time and give a bright red colour to the dried product as well as it had no significant impact on the betacyanins. 相似文献
82.
Dr. Remya Rajan Dr. Dirk Schepmann Ruben Steigerwald Dr. Julian A. Schreiber Dr. Ehab El-Awaad Prof. Joachim Jose Prof. Guiscard Seebohm Prof. Bernhard Wünsch 《ChemMedChem》2021,16(20):3201-3209
Recent studies have shown the involvement of GluN2A subunit-containing NMDA receptors in various neurological and pathological disorders. In the X-ray crystal structure, TCN-201 ( 1 ) and analogous pyrazine derivatives 2 and 3 adopt a U-shape (hairpin) conformation within the binding site formed by the ligand binding domains of the GluN1 and GluN2A subunits. In order to mimic the resulting π/π-interactions of two aromatic rings in the binding site, a [2.2]paracyclophane system was designed to lock these aromatic rings in a parallel orientation. Acylation of [2.2]paracyclophane ( 5 ) with oxalyl chloride and chloroacetyl chloride and subsequent transformations led to the oxalamide 7 , triazole 10 and benzamides 12 . The GluN2A inhibitory activities of the paracyclophane derivatives were tested with two-electrode voltage clamp electrophysiology using Xenopus laevis oocytes expressing selectively functional NMDA receptors with GluN2A subunit. The o-iodobenzamide 12 b with the highest similarity to TCN-201 showed the highest GuN2A inhibitory activity of this series of compounds. At a concentration of 10 μM, 12 b reached 36 % of the inhibitory activity of TCN-201 ( 1 ). This result indicates that the [2.2]paracyclophane system is well accepted by the TCN-201 binding site. 相似文献
83.
Thermal and Electrical Conductivity of Amorphous and Graphitized Carbide‐Derived Carbon Monoliths 下载免费PDF全文
Andreas M. Kern Bodo Zierath Joachim Haertlé Tobias Fey Bastian J. M. Etzold 《化学工程与技术》2016,39(6):1121-1129
The influence of graphitization and composition of carbide‐derived carbon (CDC) monoliths on the electrical and thermal conductivity was investigated. Carbon monoliths with varying porosities were synthesized employing biomorphous macroporous TiC and SiC as precursors. Graphitization was carried out in situ during high‐temperature chlorination with and without addition of nickel, iron, and cobalt chloride to the carbide. The graphitized monoliths showed improved properties. The results demonstrate that despite graphitic carbon also glass‐like carbon, stemming from the carbide synthesis, increases the thermal and electrical conductivity significantly. 相似文献
84.
In lightweight walls and floors, the load‐bearing timber members are protected by cladding on the sides to form a divider between two fire compartments or to provide appropriate fire protection to the load‐bearing members. The spaces between the timber members can be void or filled with insulation materials. Although a huge number of different insulation materials exist, the most commonly used material is mineral wool insulation. The existing design model for glass wool‐insulated timber‐frame constructions, given in European standard 1995‐1‐2, assumes collapse of the glass wool after failure of the cladding. However, a new form of glass wool insulation, suitable for use at high maximum service temperatures, is now available in the market. The charring phase after the cladding's failure is known as the post‐protection phase. The behaviour of the new heat‐resistant glass wool in the post‐protection phase is similar to that of stone wool and considerably better than that of traditional glass wool. The protective properties of stone wool have changed over the last decades. Charring is one of the main parameters needed to calculate the resistance of a structure to fire. Based on experimental investigations, this paper describes the analysis of the effect of the insulation with regard to its ability to protect timber members against charring during the post‐protection phase. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
85.
86.
87.
88.
In this contribution the problem of maximizing the efficiency of a hybrid power unit at a specified output power level by optimizing the generator current trajectory as well as the design variables that can be chosen during the machine design process is investigated. The concept is demonstrated based on a hybrid single-cylinder diesel engine that is coupled to an electric generator. By developing a model of the system and using open-loop optimal control the optimal operating strategy and the optimal machine design are determined. Besides that, the problems occurring in the application of this strategy to a test rig are discussed. For this purpose, a model-free real-time optimization concept based on extremum seeking control is presented. The effectiveness of both the model-based and the model-free concept are demonstrated by simulation and experimental results. 相似文献
89.
Benjamin Papendorf Emanuel Ionescu Hans‐Joachim Kleebe Christoph Linck Olivier Guillon Katharina Nonnenmacher Ralf Riedel 《Journal of the American Ceramic Society》2013,96(1):272-280
In this work, dense monolithic polymer‐derived ceramic nanocomposites (SiOC, SiZrOC, and SiHfOC) were synthesized via hot‐pressing techniques and were evaluated with respect to their compression creep behavior at temperatures beyond 1000°C. The creep rates, stress exponents as well as activation energies were determined. The high‐temperature creep in all materials has been shown to rely on viscous flow. In the quaternary materials (i.e., SiZrOC and SiHfOC), higher creep rates and activation energies were determined as compared to those of monolithic SiOC. The increase in the creep rates upon modification of SiOC with Zr/Hf relies on the significant decrease in the volume fraction of segregated carbon; whereas the increase of the activation energies corresponds to an increase of the size of the silica nanodomains upon Zr/Hf modification. Within this context, a model is proposed, which correlates the phase composition as well as network architecture of the investigated samples with their creep behavior and agrees well with the experimentally determined data. 相似文献
90.
Wachstumsmessungen von Kristallen in sauberen und verunreinigten Lösungen: Einzelkristall vs. Kollektiv 下载免费PDF全文
Information about crystal growth rates and the influence of impurities are essential for the design of industrial crystallization processes. Here, the influence of trivalent metal ions Fe3+ in solution and adsorbed in the crystal on the growth and dissolution rate is investigated. The results clearly show kinetic and thermodynamic effects caused by impurities which have to be taken into account in the equipment design. Furthermore, effects of growth rate dispersion must be excluded by investigation of crystal collectives. Additionally, the crystal growth data should be obtained from real starting solutions. 相似文献