全文获取类型
收费全文 | 132篇 |
免费 | 1篇 |
专业分类
化学 | 104篇 |
数学 | 5篇 |
物理学 | 24篇 |
出版年
2020年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 11篇 |
2012年 | 6篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 6篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1906年 | 1篇 |
排序方式: 共有133条查询结果,搜索用时 15 毫秒
91.
The solution and transport of propane in blends of polydimethyl siloxane and poly(ethylene-co-propylene) elastomers has been studied in the range 25–50°C. The dependence of the blend permeability on composition was determined and compared with the Maxwell and other expressions for transport in heterogeneous media. 相似文献
92.
Chromatographic-grade silica gel can be converted to a form of the high-silica zeolite silicalite-1, which is suitable for use as a gas chromatographic column packing and can be used with steam as carrier gas in a suitably modified chromatograph. The material has the expected molecular sieve properties and lends itself to some novel separations based on molecular size and shape. The behaviour of lower aliphatic alcohols and chlorohydrocarbons, acetone and xylenes is reported. 相似文献
93.
Photoemission from the 2p levels of the light metals excited by internally generated Kα1,2 X-rays has been observed, and the intensities compared with valence band to 2p intensity ratios obtained from X-ray photoemission spectroscopy. It is found that internal photoemission from the valence band contributes 0.5% of the intensity of the KL2,3M Auger peak. 相似文献
94.
95.
Gregory MA Hong H Lill RE Gaisser S Petkovic H Low L Sheehan LS Carletti I Ready SJ Ward MJ Kaja AL Weston AJ Challis IR Leadlay PF Martin CJ Wilkinson B Sheridan RM 《Organic & biomolecular chemistry》2006,4(19):3565-3568
The function of gene products involved in the biosynthesis of the clinically important polyketide rapamycin were elucidated by biotransformation and gene complementation. 相似文献
96.
97.
Barrie Rhodes James C. W. Chien John S. Wood A. Chandrasekaran Marvin D. Rausch 《应用有机金属化学》2002,16(6):323-330
Four titanium ansa‐cyclopentadienyl‐amido complexes of the general formula [C5H3RMe2SiN(2,6‐Me2C6H3)]TiX2(R = H,Me,Bz,tBu;X = NMe2 or Cl) have been synthesized. The complexes polymerize both ethylene and propylene in the presence of methylaluminoxane or Ph3CB(C6F5)4–triisobutylaluminum and were most active at lower temperatures. In general, the smaller the substituent on the cyclopentadienyl group, the more active the catalyst. The catalysts were found to be poorly stereoselective for the polymerization of polypropylene, with the tertiary‐butyl substituted catalyst giving a polymer with the greatest [mmmm] (14.2%). The structure of [C5H4Me2SiN(2,6‐Me2C6H3)] Ti(NMe2)2 was determined by X‐ray diffraction. The complex crystallizes in the monoclinic system space group P21/n, with a = 16.437(2), b = 8.652(3), c = 16.494(4),β = 117.54(2) and Z = 4. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
98.
Barrie PJ 《Physical chemistry chemical physics : PCCP》2008,10(12):1688-1696
This paper discusses some methods of analysing TPD data for samples obeying first-order desorption kinetics and proposes several improvements to existing practice. The methods apply in the case when the Arrhenius parameters A and E for each site are independent of coverage, and thus are normally suitable for the characterisation of porous solids. An improved implementation of the condensation approximation method is proposed to gain an initial estimate of the adsorption site distribution. Further, a variation of the method is proposed that can be used when A is a function of E. The initial estimate of the distribution can be used to analyse data obtained by an interrupted TPD experiment, in which heating is halted at a specified temperature. This method provides a reliable method of determining the parameter A for a peak in the distribution. Finally, regularisation procedures for obtaining physically sensible distributions from "noisy" TPD data are discussed. It is shown that a penalty function based on the square of the second derivative of the distribution is normally most suitable for analysing TPD data, at least in the case when the L-curve method is used to select the regularisation parameter. 相似文献
99.
Luis J Park EJ Meyer RJ Smith NB 《The Journal of the Acoustical Society of America》2007,122(4):2022-2030
Circular cymbal ultrasound arrays have been shown to be effective in delivering therapeutic levels of insulin in rats, rabbits, and pigs. To improve delivery efficiency, a rectangular cymbal design was desired in order to achieve a broader spatial intensity field without increasing the size of the device or the spatial-peak temporal-peak intensity (I(SPTP)). With a similar intensity (50 mWcm(2)), the goal was to determine if the 3x1 rectangular cymbal array could perform significantly better than the 3x3 circular array for glucose reduction in hyperglycemic rabbits. Rabbit experiments were performed using three groups: nonsonicated control (n=3), ultrasound exposure using a circular cymbal array (n=3), and ultrasound exposure using a rectangular cymbal array (n=3). Rabbits were anesthetized and a water tight reservoir that held the insulin was fastened on the rabbit's thigh. At the beginning of the experiment and every 15 min for 90 min, the blood glucose level was determined. For comparison between individual rabbits, the absolute level is normalized by subtracting out the baseline in order to arrive at the change in glucose level. For the control group, the normalized glucose level increased (more hyperglycemic) to +80.0+/-28.8 mgdl (mean+/-SEM). Using the circular array, the glucose level decreased to -146.7+/-17.8 mgdl at 90 min. However, using the rectangular cymbal array, the glucose decreased faster and to a level of -200.8+/-5.9 mgdl after 90 min. These results indicated the feasibility of the rectangular cymbal array as an improved device for drug delivery. 相似文献
100.
Sean Goggins Barrie J. Marsh Anneke T. Lubben Christopher G. Frost 《Chemical science》2015,6(8):4978-4985
Signal transduction and signal amplification are both important mechanisms used within biological signalling pathways. Inspired by this process, we have developed a signal amplification methodology that utilises the selectivity and high activity of enzymes in combination with the robustness and generality of an organometallic catalyst, achieving a hybrid biological and synthetic catalyst cascade. A proligand enzyme substrate was designed to selectively self-immolate in the presence of the enzyme to release a ligand that can bind to a metal pre-catalyst and accelerate the rate of a transfer hydrogenation reaction. Enzyme-triggered catalytic signal amplification was then applied to a range of catalyst substrates demonstrating that signal amplification and signal transduction can both be achieved through this methodology. 相似文献