全文获取类型
收费全文 | 1154篇 |
免费 | 83篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 354篇 |
金属工艺 | 52篇 |
机械仪表 | 56篇 |
建筑科学 | 45篇 |
矿业工程 | 13篇 |
能源动力 | 43篇 |
轻工业 | 96篇 |
水利工程 | 2篇 |
石油天然气 | 9篇 |
无线电 | 78篇 |
一般工业技术 | 226篇 |
冶金工业 | 55篇 |
原子能技术 | 2篇 |
自动化技术 | 200篇 |
出版年
2023年 | 8篇 |
2022年 | 28篇 |
2021年 | 132篇 |
2020年 | 39篇 |
2019年 | 44篇 |
2018年 | 65篇 |
2017年 | 46篇 |
2016年 | 77篇 |
2015年 | 62篇 |
2014年 | 67篇 |
2013年 | 101篇 |
2012年 | 70篇 |
2011年 | 86篇 |
2010年 | 50篇 |
2009年 | 48篇 |
2008年 | 55篇 |
2007年 | 36篇 |
2006年 | 27篇 |
2005年 | 31篇 |
2004年 | 26篇 |
2003年 | 20篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1241条查询结果,搜索用时 15 毫秒
61.
Tomasz Piechowiak Piotr Antos Radosław Józefczyk Patryk Kosowski Karol Skrobacz 《臭氧:科学与工程》2019,41(4):376-385
In the studies conducted, the impact of the innovative ozonation procedure on the microbial state and antioxidant potential of highbush blueberry (Vaccinum corymbosum L.) stored under cold storage conditions was assessed. Microbiological analysis was carried out to determine the total number of mesophilic aerobic bacteria and the total number of fungi during the storage experiment. In addition, changes in the flavonoid, anthocyanins, and vitamin C content and the total antioxidant capacity were monitored during the storage. The degree of fruit infection with gray mold and anthracnose was determined. It was found that daily ozonation of fruits with a dose of 15 ppm for 30 min, every 12 h, for 28 days effectively reduced the development of aerobic mesophilic bacteria and fungi. On the last day of storage, symptoms of the infection by gray mold were observed in 27.5% of the control fruit, while the absence of symptoms was observed in case of the ozonated fruit. On the other hand, ozone was ineffective in case of inhibiting the infection by anthracnose. Nevertheless, the ozonation process allowed maintaining a high antioxidant potential of the fruit and substantially reduced losses of flavonoids, anthocyanins, and vitamin C. The utilized procedure has proved to be effective, providing the possibility of extensive use of ozone as a factor allowing sustaining a high commercial and consumption value of the fruit over extended time. 相似文献
62.
63.
Tomasz Gancarz Katarzyna Berent Wojciech Skuza Katarzyna Janik 《Metallurgical and Materials Transactions A》2018,49(7):2684-2691
Magnesium has applications in the automotive and aerospace industries that can significantly contribute to greater fuel economy and environmental conservation. The Mg alloys used in the automotive industry could reduce mass by up to 70 pct, providing energy savings. However, alongside the advantages there are limitations and technological barriers to use Mg alloys. One of the advantages concerns phenomena occurring at the interface when joining materials investigated in this study, in regard to the effect of temperature and soldering time for pure Mg joints. Eutectic Zn-Al and Zn-Al alloys with 0.05 (wt pct) Li and 0.2 (wt pct) Na were used in the soldering process. The process was performed for 3, 5, and 8 minutes of contact, at temperatures of 425 °C, 450 °C, 475 °C, and 500 °C. Selected, solidified solder-substrate couples were cross-sectioned, and their interfacial microstructures were investigated by scanning electron microscopy. The experiment was designed to demonstrate the effect of time, temperature, and the addition of Li and Na on the kinetics of the dissolving Mg substrate. The addition of Li and Na to eutectic Zn-Al caused to improve mechanical properties. Higher temperatures led to reduced joint strength, which is caused by increased interfacial reaction. 相似文献
64.
The studies of soldered joints were carried out in systems: Al/solder/Al, Al/solder/Cu, Cu/solder/Cu, where the solder was (Al-Zn)EUT, (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Ag and (Al-Zn)EUT with 0.5, 1.0, and 1.5 at.% of Cu addition. Brazing was performed at 500 °C for 3 min. The EDS analysis indicated that the composition of the layers starting from the Cu pad was CuZn, Cu5Zn8, and CuZn4, respectively. Wetting tests were performed at 500 °C for 3, 8, 15, and 30 min, respectively. Thickness of the layers and their kinetics of growth were measured based on the SEM micrographs. The formation of interlayers was not observed from the side of Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed. 相似文献
65.
Aleksandra Maria Staszak Tomasz Andrzej Paw?owski 《International journal of molecular sciences》2014,15(6):10868-10891
The proteome of zygotic embryos of Acer platanoides L. was analyzed via high-resolution 2D-SDS-PAGE and MS/MS in order to: (1) identify significant physiological processes associated with embryo development; and (2) identify changes in the proteome of the embryo associated with the acquisition of seed dormancy. Seventeen spots were identified as associated with morphogenesis at 10 to 13 weeks after flowering (WAF). Thirty-three spots were associated with maturation of the embryo at 14 to 22 WAF. The greatest changes in protein abundance occurred at 22 WAF, when seeds become fully mature. Overall, the stage of morphogenesis was characterized by changes in the abundance of proteins (tubulins and actin) associated with the growth and development of the embryo. Enzymes related to energy supply were especially elevated, most likely due to the energy demand associated with rapid growth and cell division. The stage of maturation is crucial to the establishment of seed dormancy and is associated with a higher abundance of proteins involved in genetic information processing, energy and carbon metabolism and cellular and antioxidant processes. Results indicated that a glycine-rich RNA-binding protein and proteasome proteins may be directly involved in dormancy acquisition control, and future studies are warranted to verify this association. 相似文献
66.
Tomasz Gancarz Przemysław Fima Janusz Pstruś 《Journal of Materials Engineering and Performance》2014,23(5):1524-1529
Thermal expansion and electrical resistivity of alloys based on Sn-Zn eutectic with 0.5, 1.0, 1.5, and 4.0 wt.% additions of In were studied. Thermal expansion measurements were performed using thermomechanical analysis tester over 223-373 K temperature range. Electrical resistivity measurements were performed with four-probe method over 298-423 K temperature range. The electrical resistivity of alloys increases linearly with temperature and concentration of In; also coefficient of thermal expansion of the studied alloys increases with In concentration. Scanning electron microscopy revealed simple eutectic microstructure with In dissolved in Sn-rich matrix. The results obtained were compared with the available literature data. Spreading tests on Cu of Sn-8.8Zn alloys with 0.5, 1.0, and 1.5 at.% of In were performed. Wetting tests were performed at 250 °C, by sessile drop method, by means of flux, and wetting times were 3, 8, 15, 30, and 60 min. In general, no clear effect of wetting time on spreading was observed. 相似文献
67.
Marek Choratzy ;Marta Majcher ;Katarzyna Fedyszyn Urbanowicz ;Jedrzej Gtasek ;Maciej Gawlikowicz ;Tomasz Duniec 《材料科学与工程:中英文B版...》2014,(12):376-384
The authors compared their earlier results of the tumor biopsies performed under computer tomography (CT) guidance against the results of their recently modified-combined method of visualization and measurement of lung tumor parameters by CT imaging followed by US guided biopsy. In 238 (6.36%) of 3,745 patients in CT examination, the lung tumor was located peripherally, and obtaining histopathological confirmation was crucial to start the proper treatment. The patients were divided into two groups, the division was based on the biopsy method. Within the first group in I 18 patients, parietal lung tumor was confirmed and CT guided biopsy was performed. Within the second group, parietal lung tumor was confirmed in 120 patients and combined method of CT pre- biopsy planning and US guided biopsy were used. Pre-biopsy planning was performed using CT, measurements such as depth and distance of the tumor were made, obtained data were then saved on CT image and patient's skin was marked. Then obtained results were analyzed using test for two proportions. The analysis of the results confirmed the higher efficacy of the combined method taking into account the number of complications (p 〈 0.01) and diagnostic histopathological results (P 〈 0.001). Suggested innovative method, involving both CT pre-biopsy planning and US guided biopsy, allows to analyze simultaneously static CT and dynamic US images and it is considered to be an easy and effective method comparing to relying on static in nature CT images only. Our method is related to a lower complication risk rate. 相似文献
68.
69.
70.
Mieczyslaw Korzynski Tomasz Zarski Katarzyna Korzynska 《Journal of Materials Processing Technology》2011,211(12):1982-1988
The present work compares the states of the surface textures and the oscillatory fatigue strengths of specimens made of an AZ91 alloy after turning and dynamic bearing ball peening. It was found that the specimens ball peened at different time have similar surface geometric structure parameters but different strengthening intensity. It was shown that fatigue strength follows greater peening intensity and random and isotropic surface. It was also ascertained that improving (by peening) the condition of the surface layer means enhancing fatigue strength by 20–87% compared with turning. 相似文献