全文获取类型
收费全文 | 690篇 |
免费 | 20篇 |
国内免费 | 2篇 |
专业分类
化学 | 442篇 |
晶体学 | 7篇 |
力学 | 25篇 |
数学 | 101篇 |
物理学 | 137篇 |
出版年
2023年 | 2篇 |
2022年 | 27篇 |
2021年 | 23篇 |
2020年 | 15篇 |
2019年 | 20篇 |
2018年 | 13篇 |
2017年 | 18篇 |
2016年 | 31篇 |
2015年 | 23篇 |
2014年 | 24篇 |
2013年 | 52篇 |
2012年 | 47篇 |
2011年 | 59篇 |
2010年 | 27篇 |
2009年 | 40篇 |
2008年 | 45篇 |
2007年 | 35篇 |
2006年 | 29篇 |
2005年 | 22篇 |
2004年 | 27篇 |
2003年 | 11篇 |
2002年 | 19篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1996年 | 7篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
1932年 | 1篇 |
1914年 | 1篇 |
1913年 | 1篇 |
1905年 | 1篇 |
1904年 | 1篇 |
1890年 | 1篇 |
排序方式: 共有712条查询结果,搜索用时 15 毫秒
1.
2.
The effect of ohmic and conventional heat processing of different food products on their chemical and physical parameters
was studied. Depending on the food being analysed, parameters such as pH, total solids, ash, titratable acidity, ascorbic
acid, total sugars, total fatty acids, total phenolic compounds, and anthocyanins content were determined before and after
ohmic and conventional pasteurization techniques and the results were compared using one-way analysis of variance. In goat
milk samples treated by ohmic technology the pH value (6.58) and total fatty acids content in milk fat (86.5 mass %) were
comparable to those found in milk treated by conventional process, however, ohmically treated samples presented a lower content
of lactic acid, 0.13 %. In cloudberry jam samples treated by ohmic technology the results of some of the main parameters tested,
such as total sugar content 46.1 mass %, ascorbic acid content 2.83 mass %, and titratable acidity 6.01 mass % (as citric
acid) did not show significant differences when compared with samples treated by conventional technology.
Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May
2006. 相似文献
3.
4.
Expanded bed adsorption was used to purify a marketable xylanase often used in the kraft pulp bleaching process. Experiments in packed and expanded beds were carried out mainly to study the adsorption of xylanase on to a cationic adsorbent (Streamline SP) in the presence of cells. In order to study the presence of cells, a Bacillus pumilus mass (5% wet mass) was mixed with the enzyme extract and submitted to an expanded bed adsorption system. One xylanase was purified to homogeneity in the packed bed. However, the 5% cell content hampered purification. 相似文献
5.
Fonseca GS Umpierre AP Fichtner PF Teixeira SR Dupont J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(14):3263-3269
Stable transition-metal nanoparticles of the type [M(0)](n) are easily accessible through the reduction of Ir(I) or Rh(III) compounds dissolved in "dry" 1-n-butyl-3-methylimidazolium hexafluorophosphate ionic liquid by molecular hydrogen. The formation of these [M(0)](n) nanoparticles is straightforward; they are prepared in dry ionic liquid whereas the presence of the water causes the partial decomposition of ionic liquid with the formation of phosphates, HF and transition-metal fluorides. Transmission electron microscopy (TEM) observations and X-ray diffraction analysis (XRD) show the formation of [Ir(0)](n) and [Rh(0)](n) nanoparticles with 2.0-2.5 nm in diameter. The isolated [M(0)](n) nanoparticles can be redispersed in the ionic liquid, in acetone or used in solventless conditions for the liquid-liquid biphasic, homogeneous or heterogeneous hydrogenation of arenes under mild reaction conditions (75 degrees C and 4 atm). The recovered iridium nanoparticles can be reused several times without any significant loss in catalytic activity. Unprecedented total turnover numbers (TTO) of 3509 in 32 h, for arene hydrogenation by nanoparticles catalysts, have been achieved in the reduction of benzene by the [Ir(0)](n) in solventless conditions. Contrarily, the recovered Rh(0) nanoparticles show significant agglomeration into large particles with a loss of catalytic activity. The hydrogenation of arenes containing functional groups, such as anisole, by the [Ir(0)](n) nanoparticles occurs with concomitant hydrogenolysis of the C-O bond, suggesting that these nanoparticles behave as "heterogeneous catalysts" rather than "homogeneous catalysts". 相似文献
6.
I. M. Miranda Salvado F. M. A. Margaça J. Teixeira 《Journal of Sol-Gel Science and Technology》1994,2(1-3):289-294
Silica-titania gels, prepared in acidic conditions, with contents of TiO2 up to 6 mol%, have been studied by small angle neutron scattering (SANS) as wet gel with increasing aging times. In all samples, small primary particles have been found with a diameter of about 3 nm. At the gel point, cylindrical clusters, ca. 10 nm long, were observed as well. These grow with aging time, becoming branched. The cluster-cluster diffusion limited aggregation model is found to be consistent with the SANS results. The growth process is independent of the TiO2 content. It is mainly influenced by the ratio of the aging time to the gelation time. 相似文献
7.
Alvarez Carrillo Pavel Anselmo Roselli Lucia Reis Peixoto Frej Eduarda Asfora de Almeida Adiel Teixeira 《Annals of Operations Research》2022,314(2):377-392
Annals of Operations Research - The aim of this paper is to solve an agricultural technology packages selection problem by considering multiple dimensions which influence a maize producer’s... 相似文献
8.
Silva Julio Cezar Soares de Lima Silva Diogo Ferreira Ferreira Luciano de Almeida-Filho Adiel Teixeira 《4OR: A Quarterly Journal of Operations Research》2022,20(1):139-164
4OR - Even though sovereign bonds represent low-risk alternatives that give investors a healthy income, the risk assessment process for these bonds is still considered subjective because of the... 相似文献
9.
V. G. Kravchenko A. B. Lebre G. S. Litvinchuk F. S. Teixeira 《Integral Equations and Operator Theory》1995,21(3):342-354
The solution to a normalization problem for singular integral operators with Carleman shift and degenerate and unbounded coefficients inL
p
() is obtained, where is either the unit circle or the real line. The approach followed consists mainly in two steps: the reduction to a singular integral operator with bounded coefficients and the use of the solution to an abstract normalization problem.This research was supported by JNICT under the grant PBIC/C/CEN/1040/92. 相似文献
10.