全文获取类型
收费全文 | 219篇 |
免费 | 0篇 |
专业分类
化学 | 167篇 |
力学 | 2篇 |
数学 | 27篇 |
物理学 | 23篇 |
出版年
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 9篇 |
2017年 | 22篇 |
2016年 | 14篇 |
2015年 | 46篇 |
2014年 | 3篇 |
2013年 | 20篇 |
2012年 | 4篇 |
2009年 | 2篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 7篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 26篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 6篇 |
1973年 | 5篇 |
1972年 | 1篇 |
排序方式: 共有219条查询结果,搜索用时 15 毫秒
1.
This paper examines the non-linear dynamic behaviour of a flexible shaft. The shaft is mounted on two journal bearings and the axial load is supported by a defective hydrodynamic thrust bearing at one end. The defect is a levelness defect of the rotor. The thrust bearing behaviour must be considered to be non-linear because of the effects of the defect. The shaft is modelled with typical beam finite elements including effects such as the gyroscopic effects. A modal technique is used to reduce the number of degrees of freedom. Results show that the thrust bearing defects introduce supplementary critical speeds. The linear approach is unable to show the supplementary critical speeds which are obtained only by using non-linear analysis. 相似文献
2.
Flow injection system with gas diffusion for the sequential determination of total nitrogen and phosphorus in vegetables 总被引:1,自引:0,他引:1
Jose´ L. F. C. Lima Antoacutenio O. S. S. Rangel M. Renata S. Souto 《Analytical and bioanalytical chemistry》1997,358(5):657-662
A flow injection system was developed for the sequential determination of total nitrogen and phosphorus in digests of vegetables
using potentiometric and spectrophotometric detection systems, respectively. A tubular ammonium selective electrode with a
sensor system composed of nonactin/monactin in tris(2-ethylhexyl) phosphate was used. The selectivity limitations of this
electrode were overcome by the inclusion of a gas-diffusion unit in the system that separated ammonium from the rest of the
sample matrix and allowed the determination of total nitrogen and phosphorus by the partition of the sample plug between two
streams.
The results obtained with the developed FIA system were in good agreement with those of the reference methods. Sampling rates
from 40 to 60 samples per hour and relative standard deviations below 3.5% were achieved.
Received: 17 October 1996/Revised: 21 November 1996/Accepted: 27 November 1996 相似文献
3.
Karl Pays Caroline Mabille Véronique Schmitt Fernando Leal-Calderon J´erôme Bibette 《Journal of Dispersion Science and Technology》2013,34(1-3):175-186
This paper aims to review the various degradation pathays of emulsions. Aging of emulsions may proceed through three distinct microscopic mechanisms: diffusion or permeation, dewetting, and coalescence, each one being associated with a very characteristic growth scenario. We show within this context how double emulsions are a unique tool to complete the basic understanding of emulsion metastability. 相似文献
4.
5.
The effective diffusion coefficient that gives a steady-state xenon concentration of 0.2-0.3wt% in the recrystallised grains of high burn-up UO 2 fuel is calculated to lie in the range 10 m 24 to 10 m 22 m 2 s m 1 . These values are one to three orders of magnitude lower than the value currently accepted for the radiation-enhanced diffusion coefficient. The time required to reach the steady-state concentration depends on the local fission rate, the grain size distribution and the precise magnitude of the radiation-enhanced diffusion coefficient, and can take from 2 to 10 years. Additional calculations reveal that substantially less than 10% of the fission gas inventory is released from the original UO 2 grains in the outer region of the fuel prior to recrystallisation. In contrast, with a diffusion coefficient of 10 m 22 m 2 s m 1 more than 80% of the fission gas is released from the recrystallised grains of the high burn-up structure in one year. 相似文献
6.
Ukhin L. Yu. Kuz´mina L. G. Alexeenko D. V. Belousova L. V. Morkovnik A. S. Shepelenko E. N. Podshibyakin V. A. Borodkin G. S. Dmitrieva O. I. 《Russian Chemical Bulletin》2019,68(12):2290-2297
Russian Chemical Bulletin - New potentially bioactive derivatives comprising spatially hindered pyrocatechol linked to hydrazine, acid hydrazides (including isoniazid), and acetylcysteine by a... 相似文献
7.
8.
Thomas Andre´s Wolcan Ezequiel Fe´liz Mario R. Capparelli Alberto L. 《Transition Metal Chemistry》1997,22(6):541-544
The kinetics of the complexation of NiII by pteroylglutamic acid have been studied in the 545 ∘C range, the ionic strength
(0.6 M) being regulated with KNO3, in the 5.5–7.0pH range, using the stopped-flow method. Under the experimental conditions
two processes were observed. The faster process was detected in the millisecond range and is associated with the reaction
between NiII and the ligand. The slower is observed within a few seconds. Complementary equilibrium studies were made at 25
∘C. The results are consistent with the formation of a 1:1 complex between the reactants, and a mechanism is proposed to account
for the observed behaviour. Equilibrium constants for the NiII plus pteroylglutamic acid system, as well as activation parameters,
are reported.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
A. Marti´n-Esteban P. Fernández C. Cámara 《Analytical and bioanalytical chemistry》1997,357(7):927-933
Immunoaffinity techniques have been widely used for the determination of different analytes in the medical field. However
the use of antibodies immobilized in an appropriate support material to preconcentrate pesticides from environmental samples
is only recent. The production of antibodies, election of supports, antibody immobilization procedures, elution of analytes
from immunosorbents and the more recent applications in the field of pesticide analysis are reviewed. The present review concludes
that immunosorbents have great potential and discusses the present limitations and expected future trends.
Received: 29 July 1996 / Accepted: 14 August 1996 相似文献
10.
In a two-phase system (saturated aqueous calcium hydroxide, tetrabutylamnonium sulfate, dichloromethane, iron pentacarbonyl) benzyl bromides are readily carbonylated to dibenzyl ketones; α-α′ dibromoorthoxylene yields the o-quinodimethane iron tricarbonyl complex 8. It is inferred that the reactions proceed through transient generation of the tetracarbonyl ferrate dianion. 相似文献