全文获取类型
收费全文 | 173篇 |
免费 | 1篇 |
专业分类
化学 | 69篇 |
晶体学 | 4篇 |
力学 | 2篇 |
数学 | 12篇 |
物理学 | 87篇 |
出版年
2023年 | 2篇 |
2021年 | 6篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 11篇 |
2011年 | 20篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 8篇 |
1987年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1968年 | 2篇 |
1946年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有174条查询结果,搜索用时 31 毫秒
1.
An ultrasonic Doppler velocimeter (UDV) is used for an experimental investigation of turbulent pipe flow at eight different Reynolds numbers (22,300–854,900). The UDV is a multipoint probe in the sense that it takes instantaneous measurements of fluid velocities at different locations simultaneously, with remarkable resolutions in space and time. The performances of the instrument with respect to the properties of the overlap layer of the turbulent flow field are investigated; the experimental results are compared with both already existing and more recently proposed scaling laws, and with other data of experimental nature. 相似文献
2.
Gallo P Nasi A Vinci F Guadagnuolo G Brambilla G Fiori M Serpe L 《Rapid communications in mass spectrometry : RCM》2005,19(4):574-579
In this work we present a method for confirmatory analysis of chloramphenicol (CAP) in bovine and buffalo raw milk. CAP is extracted in acetonitrile and purified by affinity chromatography on an alpha-1-acid glycoprotein (AAG) column, then is identified and determined by ion-trap liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/ESI-MS/MS) analysis in the negative ion mode. CAP was identified at the minimum required performance limit (MRPL) of 0.30 ppb, by monitoring the [M-H]- ion and at least two product ions, meeting the qualitative and quantitative criteria set by the European Commission in Decision 2002/657/EC for confirmation of prohibited veterinary drugs. The trueness and within-day and between-day repeatability data are also reported. Moreover, the loading capacity of affinity columns towards CAP was tested. This method, based on the molecular recognition between drug and AAG during the purification step to improve sample cleanup, represents a quantitative and repeatable procedure for confirmatory analysis, and fits the requirements for the routine official control of CAP residues in raw milk. 相似文献
3.
4.
5.
The renewal of the urban waterfronts has become a major focus of attention for politicians and decision makers in the city’s management programs. The recognition of the patterns that define the waterfronts’ identity is essential to select new strategies of intervention for the environmental recovery. In order to create adequate environments for everyday life within a sustainable development, new links between human senses, human perception and design need to be created. Within this wide approach, the landscape and the soundscape play a significant role and can become a key driving force in the implementation of the changes. New techniques have to be tested to identify the sonic and visual parameters capable to explain the specificity of a waterfront. With this purpose, an artificial neural network (ANN) was developed, and the relative importance of the input variables was evaluated. The collected database was also analysed by multiple linear regression (MLR) to compare the outcomes of both models. The urban waterfront of Naples (Italy) was chosen as case study. The results obtained show that the performance of the neural network is better than the one of the linear regression (rANN = 0.949, rMLR = 0.639). The interpretation of the relative importance method is also quite satisfactory in the ANN. 相似文献
6.
Short and concise total asymmetric syntheses of (−)-isoretronecanol and (−)-trachelantamidine are reported. Oxidative cleavage of tert-butyl (S,S,S,Z)-7-[N-benzyl-N-(α-methylbenzyl)amino]cyclohept-3-ene-1-carboxylate, followed by hydrogenolysis promoted in situ cyclisation/reduction, which provided rapid access to the bicyclic core within (−)-isoretronecanol. Analogous treatment of the C(1)-epimer gave (−)-trachelantamidine. Overall, the syntheses of (−)-isoretronecanol and (−)-trachelantamidine were completed in eight and seven steps and 20 and 9.5% yield, respectively, from commercially available starting materials. 相似文献
7.
Stocker Mariele K. Sanson Murilo L. Bernardes Arthur A. Netto Antonio Marchi Brambilla Rodrigo 《Journal of Sol-Gel Science and Technology》2021,98(3):568-579
Journal of Sol-Gel Science and Technology - In this work, silica capsules containing bromothymol blue (BTB) were synthesized by a modified Stöber sol–gel method. These silica capsules... 相似文献
8.
9.
More specific official methodology is needed to survey the illegal use of clenbuterol in animal production plus the synthesis of new compounds that currently elude routine analytical methods. The identification of a new adrenergic agonist, N1-(2-(4-amino-3,5-dichlorophenyl)-2-hydroxyethyl)-N1-isopropyl-propanamide (known as compound A) in animal feed has prompted studies to verify if the existing cleanup procedures developed for clenbuterol are really effective. This study considers the ion-exchange mechanism on cyanopropyl (CN), sulfonic cation exchange (SCX), mixed phase (MPH) (C8 + SCX), and nonendcapped C18 (C18NE) solid-phase extraction (SPE) columns. Results indicate that compound A (by contrast with clenbuterol) is not efficiently retained on the CN, SCX, and MPH SPE columns (recovery <10%). This finding thus leads to the development of a gas chromatography-tandem mass spectrometry procedure based on C18NE SPE that is able to purify both agonists from bovine livers spiked at 0.5, 1.0, and 2.0 ppb with a mean recovery of 93% for clenbuterol and 92% for compound A. 相似文献
10.
S.?Barland X.?Hachair M.?GiudiciEmail author S.?Balle J. R.?Tredicce G.?Tissoni L.?Spinelli L.?Lugiato M.?Brambilla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2005,32(1):75-82
We analyze experimentally the spatio-temporal dynamics of the
transverse structures appearing in broad area edge-emitting
semiconductor amplifiers under CW optical injection. We
demonstrate that, in certain conditions, the light reflected by
the system exhibits a multipeaked structure whose dependence on
the parameters suggests an interpretation in terms of
cavity solitons. These structures can exhibit self-pulsations with
periods of the order of few milliseconds, which we explain in
terms of regenerative thermal oscillations. In a particular device,
we generate two single-peak structures which are spatially
uncorrelated, as required for cavity solitons. A microscopic model
shows good agreement with the main body of the experimental
results. 相似文献