全文获取类型
收费全文 | 754494篇 |
免费 | 8118篇 |
国内免费 | 2215篇 |
专业分类
化学 | 393024篇 |
晶体学 | 10726篇 |
力学 | 35921篇 |
综合类 | 23篇 |
数学 | 98392篇 |
物理学 | 226741篇 |
出版年
2021年 | 6309篇 |
2020年 | 6954篇 |
2019年 | 7670篇 |
2018年 | 9883篇 |
2017年 | 9913篇 |
2016年 | 14462篇 |
2015年 | 8633篇 |
2014年 | 13737篇 |
2013年 | 33817篇 |
2012年 | 25964篇 |
2011年 | 31392篇 |
2010年 | 22385篇 |
2009年 | 22212篇 |
2008年 | 29311篇 |
2007年 | 29322篇 |
2006年 | 27196篇 |
2005年 | 24337篇 |
2004年 | 22455篇 |
2003年 | 20085篇 |
2002年 | 19916篇 |
2001年 | 21339篇 |
2000年 | 16492篇 |
1999年 | 12954篇 |
1998年 | 10981篇 |
1997年 | 10734篇 |
1996年 | 10332篇 |
1995年 | 9340篇 |
1994年 | 9144篇 |
1993年 | 8832篇 |
1992年 | 9552篇 |
1991年 | 9929篇 |
1990年 | 9437篇 |
1989年 | 9239篇 |
1988年 | 9271篇 |
1987年 | 8884篇 |
1986年 | 8500篇 |
1985年 | 11265篇 |
1984年 | 11671篇 |
1983年 | 9754篇 |
1982年 | 10376篇 |
1981年 | 9944篇 |
1980年 | 9468篇 |
1979年 | 10057篇 |
1978年 | 10317篇 |
1977年 | 10222篇 |
1976年 | 10136篇 |
1975年 | 9709篇 |
1974年 | 9473篇 |
1973年 | 9890篇 |
1972年 | 6740篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Morey Timothy E. Varshney Manoj Flint Jason A. Seubert Christoph N. Smith W. Brit Bjoraker David G. Shah Dinesh O. Dennis Donn M. 《Journal of nanoparticle research》2004,6(2):159-170
Background: Although microemulsion-based nanoparticles (MEs) may be useful for drug delivery or scavenging, these benefits must be balanced against potential nanotoxicological effects in biological tissue (bio-nano interface). We investigated the actions of assembled MEs and their individual components at the bio-nano interface of thrombosis and hemolysis in human blood.
Methods: Oil-in-water MEs were synthesized using ethylbutyrate, sodium caprylate, and pluronic F-68 (ME4) or F-127 (ME6) in 0.9% NaClw/v. The effects of MEs or components on thrombosis were determined using thrombo-elastography, platelet contractile force, clot elastic modulus, and platelet counting. For hemolysis, ME or components were incubated with erythrocytes, centrifuged, and washed for measurement of free hemoglobin by spectroscopy.
Results and conclusions: The mean particle diameters (polydispersity index) for ME6 and ME4 were 23.6 ± 2.5 nm (0.362) and 14.0 ± 1.0 nm (0.008), respectively. MEs (0, 0.03, 0.3, 3 mM) markedly reduced the thromboelastograph maximal amplitude in a concentration-dependent manner (49.0 ± 4.2, 39.0 ± 5.6, 15.0 ± 8.7, 3.8 ± 1.3 mm, respectively), an effect highly correlated (r2 = 0.94) with similar changes caused by pluronic surfactants (48.7 ± 10.9, 30.7 ± 15.8, 20.0 ± 11.3, 2.0 ± 0.5) alone. Neither oil nor sodium caprylate alone affected the thromboelastograph. The clot contractile force was reduced by ME (27.3 ± 11.1–6.7 ± 3.4 kdynes/cm2, P = 0.02, n = 5) whereas the platelet population not affected (175 ± 28–182 ± 23 106/ml, P = 0.12, n = 6). This data suggests that MEs reduced platelet activity due to associated pluronic surfactants, but caused minimal changes in protein function necessary for coagulation. Although pharmacological concentrations of sodium caprylate caused hemolysis (EC50 = 213 mM), MEs and pluronic surfactants did not disrupt erythrocytes. Knowledge of nanoparticle activity and potential associated nanotoxicity at this bio-nano interface enables rational ME design for in vivo applications. 相似文献
972.
S. H. Park J. H. Chang M. Yang H. S. Ahn S. N. Yi K. Goto M. W. Cho T. Yao J. S. Song 《Current Applied Physics》2004,4(6):607-610
Photoluminescence (PL) linewidth broadening of CdxZn1 − xSe/ZnSe triple quantum wells, grown on GaAs substrates by molecular beam epitaxy (MBE), has been investigated. Various quantum well (QW) samples have been prepared with different QW thickness and composition (Cd-composition). Measured and calculated PL linewidth are compared. Both composition and thickness fluctuations are considered for the calculation with the parameters such as the volume of exciton, nominal thickness and composition of QWs. Surface roughness measured by atomic force microscopy (AFM) is used to estimate the interface roughness. Results show that when Cd-composition increases additional linewidth broadening due to Zn/Cd interdiffusion is enhanced. 相似文献
973.
Experimental analysis, modeling, and theoretical design of McMaster pore-filled nanofiltration membranes 总被引:1,自引:0,他引:1
A side-by-side comparison of the performance of McMaster pore-filled (MacPF) and commercial nanofiltration (NF) membranes is presented here. The single-salt and multi-component performance of these membranes is studied using experimental data and using a mathematical model. The pseudo two-dimensional model is based on the extended Nernst–Planck equation, a modified Poisson–Boltzmann equation, and hydrodynamic calculations. The model includes four structural properties of the membrane: pore radius, pure water permeability, surface charge density and the ratio of effective membrane thickness to water content. The analysis demonstrates that the rejection and transport mechanisms are the same in the commercial and MacPF membranes with different contributions from each type of mechanism (convection, diffusion and electromigration). Solute rejection in NF membranes is determined primarily by a combination of steric and electrostatic effects. The selectivity of MacPF membranes is primarily determined by electrostatic effects with a significantly smaller contribution of steric effects compared to commercial membranes. Hence, these membranes have the ability to reject ions while remaining highly permeable to low molecular weight organics. Additionally, a new theoretical membrane design approach is presented. This design procedure potentially offers the optimization of NF membrane performance by tailoring the membrane structure and operating variables to the specific process, simultaneously. The procedure is validated at the laboratory scale. 相似文献
974.
975.
976.
977.
Mathematical Notes - 相似文献
978.
979.
Guanidinium nitrate: a novel reagent for aryl nitrations 总被引:1,自引:0,他引:1
Nitration of various aromatic compounds utilising guanidinium nitrate in 85% sulfuric acid as a nitrating agent has been studied. 相似文献
980.