全文获取类型
收费全文 | 427篇 |
免费 | 20篇 |
国内免费 | 10篇 |
专业分类
化学 | 268篇 |
晶体学 | 3篇 |
力学 | 21篇 |
综合类 | 7篇 |
数学 | 60篇 |
物理学 | 98篇 |
出版年
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 18篇 |
2013年 | 22篇 |
2012年 | 26篇 |
2011年 | 25篇 |
2010年 | 14篇 |
2009年 | 14篇 |
2008年 | 27篇 |
2007年 | 21篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 14篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1965年 | 1篇 |
排序方式: 共有457条查询结果,搜索用时 19 毫秒
41.
42.
Tzong‐Ming Wu Sung‐Fu Hsu Yeng‐Fong Shih Chien‐Shiun Liao 《Journal of Polymer Science.Polymer Physics》2008,46(12):1207-1213
The thermal degradation behaviors of biodegradable poly(3‐hydroxybutyrate) (PHB) and PHB/poly(ethylene glycol) phosphonates (PEOPAs)‐modified layered double hydroxide (PMLDH) nanocomposites have been investigated using thermogravimetric analysis. Effects of PMLDH contents on the isothermal degradation kinetics of PHB were explored. These experimental results show that the degradation kinetics of PHB/PMLDH nanocomposites is the chain‐scission process of cyclic β‐elimination reaction with the following autocatalytic reactions, which is very similar to that of pure PHB matrix. Further calculated data based on the autocatalytic model can fit very well with the experimental data. The Ea value of PHB/PMLDH nanocomposites is increased as the content of PMLDH increases. This can be attributed to the incorporation of more PMLDH loading to PHB induced a decrease in the degradation rate and an increase in the residual weight for PHB/PMLDH nanocomposites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1207–1213, 2008 相似文献
43.
Duncan K. H. Fong 《The Journal of the Operational Research Society》1992,43(1):63-69
In the stochastic lead time inventory model with two suppliers and different normal lead times, the mean and variance of the lead-time demand distribution are traditionally computed using numerical integration. Tables are made available to help practitioners determine the minimum size of replenishments when orders to the suppliers are placed at the same time. This paper presents closed-form solutions to evaluate the required quantities of interest and tries to correct some mistakes in the existing tables. The expressions given here may also provide insight into the choice of sole versus dual suppliers. 相似文献
44.
Three groups of 1,2-dipalmitoyl-rac-glycero-3-phosphocholine (DPPC) large unilamellar vesicle (LUV) dispersions were studied: LUV (A) dispersions with only extraliposomal sodium chloride (NaCl), LUV (B) dispersions with intra- and extraliposomal NaCl, and LUV (C) dispersions with only intraliposomal NaCl. The NaCl concentrations ranged from 0 to 150 mM. An abrupt increase in leakage was observed around -10 degree C for all the three groups of LUV, which coincided with the temperature of extraliposomal ice formation. Within the three groups, leakage of LUV (C) was significantly higher than the other groups. Extraliposomal ice formation and the resulting freeze-concentration of LUV may be the major cause of the leakage. Intraliposomal ice formation observed at -43 degree C seemed to stop leakage of LUV when LUV were frozen below -43 degree C. An exotherm of eutectic crystallization of NaCl was occasionally observed at -37 degree C, with a higher probability of formation at 150 mM extraliposomal NaCl than at 50 mM. The eutectic crystals were thought to cause additional leakage from the LUV (B). 相似文献
45.
C. F. Chan Man Fong 《Applied Scientific Research》1971,23(1):16-22
Using Stuart's energy method, the torque on the inner cylinder, for a second order fluid, in the supercritical regime is calculated. It is found that when the second normal stress difference is negative, the flow is more stable than for a Newtonian fluid and the torque is reduced. If the second normal stress difference is positive, then the flow is more stable and there is no torque reduction. Experimental data related to the present work are discussed.Nomenclature
a
amplitude of the fundamentals
-
A
ij
(1)
, A
ij
(2)
first and second Rivlin-Ericksen tensors
-
d
r
2–r
1
- D
d/dx
-
E
-
F
-
g
ij
metric tensor
-
G
torque on the inner cylinder in the supercritical regime
-
h
height of the cylinders
-
k
0
/d
2
-
k
1
/d
2
-
I
1
-
I
2
-
I
3
-
I
4
-
r
1, r
2
radii of inner and outer cylinders respectively
-
r
0
1/2(r
1+r
2)
-
R
Reynolds number
1
r
1
d/
0
-
R
c
critical Reynolds number
-
T
Taylor number r
1
1
2
d
3
2/
0
2
*)
-
T
c
critical Taylor number
-
u
1, v
1, w
1
Fundamentals of the disturbance
-
u
i
, v
i
, w
i
, (i>1)
harmonics
-
mean velocity (not laminar velocity)
-
u
–u
1/ar
1
1
-
v
v
1/Rar
1
1
-
x
(r–r
0)/d
-
,
material constants
-
0
viscosity
-
wave number d
-
density
-
1
angular velocity of inner cylinder
-
tilde denotes complex conjugate 相似文献
46.
Zou J Pan L Li Q Zhao J Pu J Yao P Gong N Lu Y Kondratyuk TP Pezzuto JM Fong HH Zhang H Sun H 《Organic letters》2011,13(6):1406-1409
From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction. 相似文献
47.
Leung CH Chan DS Yang H Abagyan R Lee SM Zhu GY Fong WF Ma DL 《Chemical communications (Cambridge, England)》2011,47(9):2511-2513
The natural product-like 6,6″-biapigenin has been identified as only the second inhibitor of NEDD8-activating enzyme using virtual screening. This compound was active in enzyme and cell-based assays, with potency in the micromolar range. 相似文献
48.
He H Lo PC Yeung SL Fong WP Ng DK 《Chemical communications (Cambridge, England)》2011,47(16):4748-4750
A series of unsymmetrical distyryl BODIPYs have been prepared which function as highly potent photosensitisers with in vitro IC(50) values as low as 15 nM. Their cellular uptake, subcellular localisation and photocytotoxicity depend greatly on the styryl substituents. 相似文献
49.
50.
This paper explored the technical feasibility of surgical calcium alginate stanch fibre steriliged by radiation. By detecting the biological load before and after irridiation the optimum sterilized dose is 10–12KGY. By determing the Ca++ content, a linear regression equation relative to adsorbed dose and Ca++ content percentage is given out. lgD=0.13449+7.966x10-3N(r=0.9935) The result of biological studies of radio sterilized stanch fibre to be applied on adult rabbits and NIH mice by biologic test was performed that the γ-ray sterilized stanchfibre had no irritant effect on both the health and the wound skin, crust formation rate was better than of the check. The total and partial irritation intensity and the allergization rate became zero. 相似文献