全文获取类型
收费全文 | 545篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
化学 | 414篇 |
晶体学 | 13篇 |
力学 | 18篇 |
数学 | 62篇 |
物理学 | 54篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 10篇 |
2015年 | 13篇 |
2014年 | 10篇 |
2013年 | 19篇 |
2012年 | 26篇 |
2011年 | 36篇 |
2010年 | 30篇 |
2009年 | 43篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 26篇 |
2005年 | 9篇 |
2004年 | 20篇 |
2003年 | 39篇 |
2002年 | 31篇 |
2001年 | 25篇 |
2000年 | 23篇 |
1999年 | 15篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有561条查询结果,搜索用时 15 毫秒
41.
42.
An alternative approach to synthesize pedamide,a key building block of pederin was described.Iodine-induced asymmetric heterocyclization was used as the key step to construct the skeleton,a tetrahydropyran ring with three chiral centers.Brown's asymmetric allylation and Lewis acid-mediated allylation were investigated to introduce chains and chiral alcohols.Sharpless dihydroxylation decorated the side chain.And high optically pure target was obtained by removing the epimers formed in these reactions on c... 相似文献
43.
44.
45.
46.
A convenient route for the synthesis of 3,4-dihydrocoumarin derivates from salicylaldehyde derivates and 1,3-dicarbonyl compounds under solvent-free microwave irradiation conditions was described. In this way, a range of compounds was obtained in moderate to good yields in a short reaction time. 相似文献
47.
Steady laminar forced convection gaseous slip-flow through parallel-plates micro-channel filled with porous medium under Local
Thermal Non-Equilibrium (LTNE) condition is studied numerically. We consider incompressible Newtonian gas flow, which is hydrodynamically
fully developed while thermally is developing. The Darcy–Brinkman–Forchheimer model embedded in the Navier–Stokes equations
is used to model the flow within the porous domain. The present study reports the effect of several operating parameters on
velocity slip and temperature jump at the wall. Mainly, the current study demonstrates the effects of: Knudsen number (Kn),
Darcy number (Da), Forchheimer number (Γ), Peclet number (Pe), Biot number (Bi), and effective thermal conductivity ratio
(K
R) on velocity slip and temperature jump at the wall. Results are given in terms of skin friction (C
f
Re
*) and Nusselt number (Nu). It is found that the skin friction: (1) increases as Darcy number increases; (2) decreases as Forchheimer
number or Knudsen number increases. Heat transfer is found to (1) decreases as the Knudsen number, Forchheimer number, or
K
R increases; (2) increases as the Peclet number, Darcy number, or Biot number increases. 相似文献
48.
49.
Wenjun Tang Dr. Andrew G. Capacci Xudong Wei Dr. Wenjie Li Dr. Andre White Dr. Nitinchandra D. Patel Jolaine Savoie Joe J. Gao Sonia Rodriguez Dr. Bo Qu Dr. Nizar Haddad Dr. Bruce Z. Lu Dr. Dhileepkumar Krishnamurthy Dr. Nathan K. Yee Dr. Chris H. Senanayake Dr. 《Angewandte Chemie (International ed. in English)》2010,49(34):5879-5883
50.
Mohamed Dawod Michael C. BreadmoreRosanne M. Guijt Paul R. Haddad 《Journal of chromatography. A》2010,1217(3):386-393
Three strategies were investigated for the simultaneous separation and on-line preconcentration of charged and neutral hypolipidaemic drugs in micellar electrokinetic chromatography (MEKC). A background electrolyte (BGE) consisting of 20 mM ammonium bicarbonate buffer (pH 8.50) and 50 mM sodium dodecyl sulfate (SDS) was used for the separation and on-line preconcentration of the drugs. The efficiencies of sweeping, analyte focusing by micelle collapse (AFMC), and simultaneous field-amplified sample stacking (FASS) and sweeping, were compared for the preconcentration of eight hypolipidaemic drugs in different conductivity sample matrices. When compared with a hydrodynamic injection (5 s at 50 mbar, 0.51% of capillary volume to detection window) of drug mixture prepared in the separation BGE, improvements of detection sensitivity of 60-, 83-, and 80-fold were obtained with sweeping, AFMC and simultaneous FASS and sweeping, respectively, giving limits of detection (LODs) of 50, 36, and 38 μg/L, respectively. The studied techniques showed suitability for focusing different types of analytes having different values of retention factor (k). This is the first report for the separation of different types of hypolipidaemic drugs by capillary electrophoresis (CE). The three methods were validated then applied for the analysis of target analytes in wastewater samples from Hobart city. 相似文献