全文获取类型
收费全文 | 1567篇 |
免费 | 57篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 343篇 |
金属工艺 | 43篇 |
机械仪表 | 37篇 |
建筑科学 | 87篇 |
矿业工程 | 5篇 |
能源动力 | 40篇 |
轻工业 | 79篇 |
水利工程 | 21篇 |
石油天然气 | 15篇 |
无线电 | 169篇 |
一般工业技术 | 338篇 |
冶金工业 | 347篇 |
原子能技术 | 5篇 |
自动化技术 | 81篇 |
出版年
2022年 | 12篇 |
2021年 | 27篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 31篇 |
2015年 | 16篇 |
2014年 | 39篇 |
2013年 | 59篇 |
2012年 | 48篇 |
2011年 | 42篇 |
2010年 | 47篇 |
2009年 | 52篇 |
2008年 | 45篇 |
2007年 | 67篇 |
2006年 | 45篇 |
2005年 | 35篇 |
2004年 | 26篇 |
2003年 | 40篇 |
2002年 | 34篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 36篇 |
1998年 | 118篇 |
1997年 | 87篇 |
1996年 | 60篇 |
1995年 | 42篇 |
1994年 | 44篇 |
1993年 | 31篇 |
1992年 | 15篇 |
1991年 | 27篇 |
1990年 | 24篇 |
1989年 | 20篇 |
1988年 | 17篇 |
1987年 | 21篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 15篇 |
1980年 | 21篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1976年 | 20篇 |
1975年 | 13篇 |
1974年 | 13篇 |
1971年 | 13篇 |
1966年 | 10篇 |
排序方式: 共有1625条查询结果,搜索用时 15 毫秒
31.
Dieter Braun Manfred Rtzsch Peter Fiedler Günter Weber Heinz Hofmann Bernd Gutschalk 《大分子材料与工程》1991,187(1):101-121
Based on the example of PE-LD grades and on model substances obtained by preparative fractionation (fractions in the molecular weight range M?w = 1.2 ? 390·104 g/mol), comprehensive investigations regarding the problems of structure/properties have been carried out. The correlations of M?w with 15 physical and application technological perameters have been investigated taking into account the reaction mechanism during the manufacturing of PE-LD in the tubular and agitated autoclave reactor, resulting in the formation of so-called primary structure perameters M?n, M?w, molar mass distribution, short chain branching and long chain branching. For the interpretation of the results, among other factors, also the morphological conditions have been taken into consideration, which in connection with the molecular parameters reveal — for specific M?w-ranges — strong changes and saturation ranges, resp., for the physical and application technological properties. 相似文献
32.
In addition to pyrolysis and degradation with superheated steam the hydrogenolytic degradation of cured phenolic resins induced by hydrogen-donors has been investigated. Especially with 1,2,3,4-tetrahydronaphthalene (tetralin) a considerable amount of transferred hydrogen to the dispersed resin particles, involved with formation of naphthalene, has been observed at 400°C. With total maximal yields of 98 wt.-% (ref. to the initial amount of phenolic resin) of phenol, methyl phenols, and oligomerous phenolic degradation products a recovering of industrial phenolic resin wastes should be possible. Kinetic and scanning electron microscopic investigations are employed to give some mechanistic explanations involving the hydrogenolytic liquefaction of cured phenolic resins. 相似文献
33.
Gel permeation chromatography and thin layer chromatography have been used respectively to separate and characterize the first seven members of an epoxy resin polymer homologous series on a preparative and analytical scale. The epoxy resin was formed by the reaction between Bisphenol-A and epichlorhydrin. NMR was used to identify the oligomers. The relationship between extinction coefficient and degree of polymerisation was also determined. 相似文献
34.
35.
36.
L. Wieth K. Kelemen S. Braun R. Koch H.-J. Bauer H. P. Schuchmann 《Microfluidics and nanofluidics》2016,20(2):42
High-pressure homogenization is a widely used process in the food, pharmaceutical, and cosmetic industry for producing emulsions. Because of small dimensions and high velocities, the experimental and numerical investigation of such a process is challenging. Hence, the development of products is mostly based on trial and error. In this paper, simulations of a generic high-pressure homogenization process using the Lagrangian, mesh-free smoothed particle hydrodynamics (SPH) method are presented and compared to experimental findings using Micro-Particle Image Velocimetry (μ-PIV). The SPH code has been developed and validated with the scope of simulating technical relevant multi-phase problems (Höfler et al. 2012). The present simulations cover the investigation of two different dynamic viscosities of the dispersed phase as well as different droplet trajectories. The comparison between the simulations and the experiments focusses on the velocity distribution of the continuous phase and the droplet deformation and breakup. In both cases a qualitatively good agreement is observed, demonstrating the ability of our SPH implementation for simulating technical relevant two-phase flows. 相似文献
37.
38.
Fernando Maccari Tarini Prasad Mishra Monica Keszler Tobias Braun Esmaeil Adabifiroozjaei Iliya Radulov Tianshu Jiang Enrico Bruder Olivier Guillon Leopoldo Molina-Luna Martin Bram Oliver Gutfleisch 《Advanced Engineering Materials》2023,25(18):2300252
Flash spark plasma sintering (flash SPS) is an attractive method to obtain Nd–Fe–B magnets with anisotropic magnetic properties when starting from melt-spun powders. Compared to the benchmark processing route via hot pressing with subsequent die upsetting, flash SPS promises electroplasticity as an additional deformation mechanism and reduced tool wear, while maximizing magnetic properties by tailoring the microstructure—fully dense and high texture. A detailed parameter study is conducted to understand the influence of Flash SPS parameters on the densification and magnetic properties of commercial MQU-F powder. It is revealed that the presintering conditions and preheating temperature before applying the power pulse play a major role for tailoring grain size and texture in the case of hot deformation via Flash SPS. Detailed microstructure and magnetic domain evaluation disclose the texture enhancement with increasing flash SPS temperature at the expense of coercivity. The best compromise between remanence and coercivity (1.37 T and 1195 kA m−1, respectively) is achieved through a combination of presintering at 500 °C for 120 s and preheating temperature of 600 °C, resulting in a magnet with energy product (BH)max of 350 kJm−3. These findings show the potential of flash SPS to obtain fully dense anisotropic nanocrystalline magnets with high magnetic performance. 相似文献
39.
U Fritz M Rohrberg C Lange W Weyland A Br?uer U Braun 《Canadian Metallurgical Quarterly》1996,45(11):1059-1066
Temperature of the tympanic membrane is recommended as a "gold standard" of core-temperature recording. However, use of temperature probes in the auditory canal may lead to damage of tympanic membrane. Temperature measurement in the auditory canal with infrared thermometry does not pose this risk. Furthermore it is easy to perform and not very time-consuming. For this reason infrared thermometry of the auditory canal is becoming increasingly popular in clinical practice. We evaluated two infrared thermometers-the Diatek 9000 Thermoguide and the Diatek 9000 Instatemp-regarding factors influencing agreement with conventional tympanic temperature measurement and other core-temperature recording sites. In addition, we systematically evaluated user dependent factors that influence the agreement with the tympanic temperature. MATERIALS AND METHODS: In 20 volunteers we evaluated the influence of three factors: duration of the devices in the auditory canal before taking temperature (0 or 5 s), interval between two following recordings (30, 60, 90, 120, 180 s) and positioning of the grip relative to the auditory-canal axis (0, 60, 180 and 270 degrees). Agreement with tympanic contact probes (Mon-a-therm tympanic) in the contralateral ear was investigated in 100 postoperative patients. Comparative readings with rectal (YSI series 400) and esophageal (Mon-a-therm esophageal stethoscope with temperature sensor) probes were done in 100 patients in the ICU. The method of Bland and Altman was taken for comparison. RESULTS: Shortening of the interval between two consecutive readings led to increasing differences between the two measurements with the second reading decreasing. A similar effect was seen when positioning the infrared thermometers in the auditory canal before taking temperatures: after 5 s the recorded temperatures were significantly lower than temperature recordings taken immediately. Rotation of the devices out of the telephone handle position led to increasing lack of agreement between infrared thermometry and contact probes. Mean differences between infrared thermometry (Instatemp and Thermoguide, CAL-Mode) and tympanic probes were -0.41 +/- 0.67 degree C (2 SD) and -0.43 +/- 0.70 degree C, respectively. Mean differences between the Thermoquide (Rectal-Mode) and rectal probe were -0.19 +/- 0.72 degree C, and between the Thermoguide (Core Mode) and esophageal probe -0.13 +/- 0.74 degree C. DISCUSSION: Although easy to use, infrared thermometry requires careful handling. To obtain optimal recordings, the time between two consecutive readings should not be less than two min. Recordings should be taken immediately after positioning the devices in the auditory canal. Best results are obtained in the 60 degrees position with the grip of the devices following the ramus mandibulae (telephone handle position). The lower readings of infrared thermometry compared with tympanic contact probes indicate that the readings obtained represent the temperature of the auditory canal rather than of the tympanic membrane itself. To compensate for underestimation of core temperature by infrared thermometry, the results obtained are corrected and transferred into core-equivalent temperatures. This data correction reduces mean differences between infrared recordings and traditional core-temperature monitoring, but leaves limits of agreement between the two methods uninfluenced. 相似文献
40.
The simulation of the wind action over the CAARC (Commonwealth Advisory Aeronautical Council) standard tall building model is performed in the present work. Aerodynamic and aeroelastic analyses are reproduced numerically in order to demonstrate the applicability of CFD techniques in the field of wind engineering. A major topic in this paper is referred to one of the first attempts to simulate the aeroelastic behavior of a tall building employing complex CFD techniques. Numerical results obtained in this work are compared with numerical and wind tunnel measurements and some important concluding remarks about the present simulation are also reported. 相似文献