全文获取类型
收费全文 | 695篇 |
免费 | 58篇 |
国内免费 | 1篇 |
学科分类
工业技术 | 754篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 18篇 |
2018年 | 20篇 |
2017年 | 20篇 |
2016年 | 20篇 |
2015年 | 19篇 |
2014年 | 20篇 |
2013年 | 27篇 |
2012年 | 15篇 |
2011年 | 27篇 |
2010年 | 22篇 |
2009年 | 21篇 |
2008年 | 29篇 |
2007年 | 32篇 |
2006年 | 17篇 |
2005年 | 15篇 |
2004年 | 17篇 |
2003年 | 17篇 |
2002年 | 14篇 |
2001年 | 11篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 50篇 |
1997年 | 28篇 |
1996年 | 25篇 |
1995年 | 11篇 |
1994年 | 19篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 5篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有754条查询结果,搜索用时 250 毫秒
11.
J. F. Barbot G. Rivaud C. Blanchard J. C. Desoyer D. Le-Scoul 《Journal of Materials Science: Materials in Electronics》1990,1(1):18-19
We irradiated Cd0.2Hg0.8Te samples at room temperature in the plastic range, with a CO2 laser beam the wavelength of which (=10 500 nm) is 20% longer than the absorption threshold. We observed a positive photoplastic effect (PPE) of the order PPE/4 to 5%. 相似文献
12.
Edwin Ramaroson Gilbert Blanchard Michel Che Jean-Michel Tatibouët 《Catalysis Letters》1992,15(4):393-400
The oxidative dimerisation of propene to 1,5-hexadiene has been investigated on Bi-Zn-O catalysts. The Bi48ZnO73 phase, observed in the catalysts calcined at 700 ° C is an active and selective catalyst for the formation of 1,5-hexadiene. The best catalytic performance (1,5-hexadiene selectivity 64%) has been obtained at 525 ° C, with a propene to oxygen ratio of 26, on a catalyst formed by Bi48ZnO73 with a small excess of ZnO. 相似文献
13.
Uwe Gbureck Jake E. Barralet Michael Hofmann Roger Thull 《Journal of the American Ceramic Society》2004,87(2):311-313
It was found that prolonged high-energy ball-milling of Hilgenstokite (tetracalcium phosphate, TTCP) resulted in a decrease in both particle and crystallite size, leading to a mechanical activation of the compound. This mechanically activated material demonstrated a high reactivity such that, in contrast to highly crystalline TTCP, a setting reaction with water to nanocrystalline hydroxyapatite (HA) and Ca(OH)2 could be achieved at 37°C. However, crystalline TTCP is practically unreactive at physiologic temperatures because of the formation of a thin HA layer on the particle surface preventing further reaction. 相似文献
14.
Petr Štěpànek Jaromír Jakeš Česmír Koňák Robert Johnsen Wyn Brown 《Polymer Bulletin》1987,18(2):175-182
Summary Measurements of autocorrelation functions extending over a broad time range are reported for a sample of polystyrene in ethyl acetate as a function of temperature between –44°C (-temperature) and 70°C. The corresponding spectra of decay times are obtained by two mathematical methods. The existence of three dynamic processes is shown and their temperature and angular behaviour is studied. 相似文献
15.
T. Lesage C. Verrier P. Bazin J. Saussey S. Malo C. Hedouin G. Blanchard M. Daturi 《Topics in Catalysis》2004,(1):31-36
In situ FT-IR spectroscopy coupled with mass spectrometry have been used to study the mechanism of nitrates formation and reduction over a common Pt–Rh/Ba/Al2O3 NO
x
storage catalyst, compared with a different alumina-based compound.The experimental device used consists of a transmission reactor cell (having a very small dead volume) dedicated to the evolution of surface species, and of a mass spectrometer combined with a FT-IR micro-cell for gas analysis, allowing time resolved analysis in stationary and transient conditions.At the first time the nitration properties of the catalysts under a lean flow have been studied in the appropriate temperature window (473–673 K). The dynamics of nitrates formation has been pointed out, as well as the different coordination sites on the compounds surface. Then the catalysts have been alternatively exposed to rich and lean flows very close to the real exhaust composition. This has allowed the identification of reduction pathway, active sites, intermediate species and by-products for NO
X
-trap reaction. In particular, we have differentiated the role of the support and of the noble metal in the mechanism, as well as of isocyanate adspecies and ammonia among the detected species. The very high NO
X
storage properties and the selectivity (near 100%) in nitrogen of the newly designed catalyst have been pointed out. 相似文献
16.
The nucleation, growth and coalescence of grain-boundary cavities is the primary damage mechanism observed during creep of structural ceramics. Furthermore, grain-boundary sliding (GBS) has been identified as the driving force process. Although the creep characteristics of structural ceramics have been extensively studied, very little is known about the details of GBS during creep and how GBS relates to cavitation kinetics. This paper presents the results of a study using a machine vision system to measure Mode II GBS displacements in a Lucalox Al2O3. Specifically, sliding displacements as large as 0.4 m were measured. The measured displacements indicate that some grain boundaries experienced shear strains and strain rates of 4200% and 2.3×10–2 s–1, respectively. The techniques utilized for these measurements are described in detail, and data gathered during a 2 1/2 h compressive creep test under a stress of 138 MPa at 1600 °C are presented and discussed. 相似文献
17.
Jake Cobb Author Vitae Author Vitae 《Journal of Systems and Software》2008,81(9):1539-1558
Web proxy caches are used to reduce the strain of contemporary web traffic on web servers and network bandwidth providers. In this research, a novel approach to web proxy cache replacement which utilizes neural networks for replacement decisions is developed and analyzed. Neural networks are trained to classify cacheable objects from real world data sets using information known to be important in web proxy caching, such as frequency and recency. Correct classification ratios between 0.85 and 0.88 are obtained both for data used for training and data not used for training. Our approach is compared with Least Recently Used (LRU), Least Frequently Used (LFU) and the optimal case which always rates an object with the number of future requests. Performance is evaluated in simulation for various neural network structures and cache conditions. The final neural networks achieve hit rates that are 86.60% of the optimal in the worst case and 100% of the optimal in the best case. Byte-hit rates are 93.36% of the optimal in the worst case and 99.92% of the optimal in the best case. We examine the input-to-output mappings of individual neural networks and analyze the resulting caching strategy with respect to specific cache conditions. 相似文献
18.
J. F. Barbot P. Girault C. Blanchard I. A. Hümmelgen 《Journal of Materials Science》1995,30(13):3471-3474
Deep level transient spectroscopy (DLTS) has been used to study the traps associated with dislocations in n-type Hg0.3Cd0.7Te. Dislocations have been generated by ion implantation at high fluence. Two of the broadened lines (E1=E
c–0.22eV and E1=E
c–0.34eV), we have observed, show a logarithmic dependence with the filling pulse. They are characteristic of point defect clouds surrounding or generated by the dislocations. An unusual broadened line (E2=E
c–0.27eV) has also been observed, its amplitude decreases for filling pulses longer than 50 s. This can be explained by a configuration change of the defect leading to the appearance of a new DLTS line. In addition, an electron trap (EP4=E
c–0.22eV), which seems to behave like an isolated point defect, has also been found. 相似文献
19.
Development of Highly Functional Biomaterials by Decoupling and Recombining Material Properties 下载免费PDF全文
20.