全文获取类型
收费全文 | 2557篇 |
免费 | 143篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 102篇 |
综合类 | 4篇 |
化学工业 | 629篇 |
金属工艺 | 96篇 |
机械仪表 | 50篇 |
建筑科学 | 92篇 |
矿业工程 | 7篇 |
能源动力 | 90篇 |
轻工业 | 197篇 |
水利工程 | 9篇 |
石油天然气 | 5篇 |
无线电 | 211篇 |
一般工业技术 | 434篇 |
冶金工业 | 393篇 |
原子能技术 | 21篇 |
自动化技术 | 362篇 |
出版年
2023年 | 49篇 |
2022年 | 61篇 |
2021年 | 98篇 |
2020年 | 86篇 |
2019年 | 79篇 |
2018年 | 78篇 |
2017年 | 76篇 |
2016年 | 90篇 |
2015年 | 56篇 |
2014年 | 103篇 |
2013年 | 152篇 |
2012年 | 116篇 |
2011年 | 156篇 |
2010年 | 88篇 |
2009年 | 98篇 |
2008年 | 115篇 |
2007年 | 84篇 |
2006年 | 78篇 |
2005年 | 52篇 |
2004年 | 57篇 |
2003年 | 53篇 |
2002年 | 49篇 |
2001年 | 35篇 |
2000年 | 26篇 |
1999年 | 47篇 |
1998年 | 132篇 |
1997年 | 84篇 |
1996年 | 39篇 |
1995年 | 48篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 19篇 |
1991年 | 15篇 |
1990年 | 19篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 16篇 |
1976年 | 20篇 |
1973年 | 15篇 |
1967年 | 11篇 |
排序方式: 共有2702条查询结果,搜索用时 0 毫秒
1.
Anastasiya Rybak Patrice A. Fokou Michael A. R. Meier 《European Journal of Lipid Science and Technology》2008,110(9):797-804
Olefin metathesis, awarded with the Nobel Prize in Chemistry 2005 for Chauvin, Grubbs and Schrock, has emerged as a powerful tool for organic as well as polymer chemistry. In oleochemistry, this reaction is well known and has been applied for many decades. Examples include the functionalization of the double bonds of different oleochemicals or the (direct) polymerization of plant oils via metathesis. More recent developments, particularly the development of better and more robust catalysts, allow for highly efficient cross‐metathesis reactions opening new possibilities for the direct introduction of chemical functionalities. Within this contribution, the development of metathesis in oleochemistry will be discussed, covering self‐metathesis as well as more recent developments in the field of cross‐metathesis that lead to desired platform chemicals. 相似文献
2.
3.
Occlusion of large atrial septal defects with a centering buttoned device: early clinical experience
EB Sideris M Leung JH Yoon CR Chen R Lochan AM Worms C Rey B Meier 《Canadian Metallurgical Quarterly》1996,131(2):356-359
A feasibility clinical study was conducted for the transcatheter occlusion of large ostium secundum atrial septal defects with the centering buttoned device. The centering buttoned device is a modification of the regular buttoned device in which a centering counter-occluder is sutured at the central 40% portion of the occluder. During centering it is stretched, forming a parachute-shaped structure and pulling the occluder over the center of the defect. During buttoning, the counter-occluder forms a double figure eight, opposing the right atrial side of the atrial septum. Occlusion was performed in 12 patients aged 6 to 56 years. All had been rejected for transcatheter occlusion by the regular buttoned device, because of either their defect size or the lack of adequate septal rim. The defect size varied between 23 and 31 mm, and the device size varied between 45 and 60 mm. Nine had immediate effective occlusions of their defects and three residual shunts. One patient with unbuttoning had hemolysis at 2 weeks and underwent surgery. Early results of the transcatheter occlusion of large atrial septal defects are promising, and larger clinical trials are justified. 相似文献
4.
Maurus Biedermann Konrad Grob Dieter Fr?hlich Werner Meier 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1992,195(5):409-416
Summary On-line coupled liquid chromatography-gas chromatography-flame ionisation detection (LC-GC-FID) enables efficient and unambiguous determination of irradiation for some fat-containing foods (e.g. meat). Other products, however, contain interfering components or are contaminated, e.g., with mineral oil. Since more selective detection by mass spectrometry has limited success, the determination was improved by a more selective isolation of some key components among the fat degradation products, e.g. the dienes or trienes, by LC-LC-GC-FID. Applications are shown for soup mixes, some spices, fish, and shrimps.
Nachweis der Bestrahlung fetthaltiger Lebensmittel durch direkt gekoppelte LC-GC und LC-LC-GC
Zusammenfassung Die Bestrahlung einiger fetthaltiger Lebensmittel, z. B. Fleisch, kann mit direkt gekoppelter LC-GC-FID rationell und eindeutig nachgewiesen werden. In anderen Proben wird die Analyse aber durch Inhaltsstoffe des Produktes oder durch Verunreinigungen (z. B. mit Mineralöl) gestört. Da selektivere Detektion durch Massenspektrqmetrie wenig verspricht, wurde der Nachweis durch selektivere Isolierung von Schlüsselkomponenten unter den Bestrahlungsprodukten, z. B. der Diene oder Triene, mittels LC-LC-GC yerbessert. Anwendungen werden gezeigt für Suppenpulver, einige Gewürze, Fisch und Garnelen.相似文献
5.
6.
Rudolf Felix 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2008,12(2):129-135
Real world applications of a decision model of relationships between goals based on fuzzy relations are presented. In contrast
to other approaches the relationships between decision goals or criteria for each decision situation are represented and calculated
explicitly. The application fields are decision making for financial services and optimization of production sequences in
car manufacturing. 相似文献
7.
E. J. Pavlina A. M. Meier P. Monteleone J. D. Weigner 《Journal of Materials Science》2007,42(2):705-713
Existing multi-layer devices using lead-based piezoelectric ceramics utilize an internal electrode that does not bond the
ceramic layers. Improvements in device performance and processing could be gained if the electrode also acted as a bond between
the ceramic layers. In the current work, the feasibility of brazing lead zirconate titanate (PZT) in ambient conditions utilizing
silver-based alloys containing low melting temperature metal oxides was investigated. Wettability, joint fracture strength,
and microstructural analyses were conducted for various PZT/silver–metal oxide systems. The metal oxide additions included
copper (II) oxide, vanadium pentoxide, lead (II) oxide, and eutectic lead oxide-titanium (IV) oxide. The silver–copper oxide
(Ag–CuO) system demonstrated the most potential; exhibiting an apparent contact angle of approximately 64° and an average
braze joint fracture strength that was approximately 62% of the monolithic PZT strength. In addition, no significant reaction
product formation was observed at the silver/PZT interface. However, a preliminary investigation of multi-layer devices electroded
with Ag–CuO alloys indicated a decrease in the resistivity of the brazed PZT by several orders of magnitude. 相似文献
8.
Perchloric acid (70%) was used to create simulated periapical lesions in tooth sockets of 15 dentate cadaver jaw specimens. Using the Trophy USA direct digital radiographic system, linear images were captured at selected time intervals after initial acid application and altered by contrast reversal, pseudocolor enhancement, and two forms of histogram equalization. The 525 total images were randomized for display on a computer monitor for evaluation by five endodontists. Images were evaluated twice by each rater, with viewings 1 to 2 wk apart. Statistical analysis determined interrater variability, intrarater reproducibility, and the relative merits of each enhancement technique. At 8, 12, 16, and 24 h after acid application, both techniques of histogram equalization yielded a statistically significant improvement over reverse contrast in perception of periapical patholais. Linear and pseudocolor-enhanced images were also significantly more diagnostic than reverse contrast at 12, 16, and 24 h. Intrarater reproducibility showed moderate agreement, but analysis showed only a fair level of interrater agreement. 相似文献
9.
In a review of 328 cases the combination of laparoscopic cholecystectomy with specific use of endoscopic retrograde cholangiography (pre- and postoperatively) proved to be a riskless, secure and time-saving procedure. In our opinion this is a minimal invasive method of treatment for patients with cholecysto-/choledocholithiasis. 相似文献
10.