全文获取类型
收费全文 | 1629篇 |
免费 | 257篇 |
国内免费 | 262篇 |
专业分类
化学 | 1243篇 |
晶体学 | 19篇 |
力学 | 50篇 |
综合类 | 15篇 |
数学 | 84篇 |
物理学 | 737篇 |
出版年
2024年 | 7篇 |
2023年 | 5篇 |
2022年 | 53篇 |
2021年 | 62篇 |
2020年 | 53篇 |
2019年 | 35篇 |
2018年 | 52篇 |
2017年 | 50篇 |
2016年 | 62篇 |
2015年 | 47篇 |
2014年 | 63篇 |
2013年 | 145篇 |
2012年 | 80篇 |
2011年 | 82篇 |
2010年 | 94篇 |
2009年 | 112篇 |
2008年 | 92篇 |
2007年 | 76篇 |
2006年 | 88篇 |
2005年 | 76篇 |
2004年 | 90篇 |
2003年 | 85篇 |
2002年 | 78篇 |
2001年 | 69篇 |
2000年 | 61篇 |
1999年 | 55篇 |
1998年 | 50篇 |
1997年 | 31篇 |
1996年 | 22篇 |
1995年 | 30篇 |
1994年 | 42篇 |
1993年 | 20篇 |
1992年 | 26篇 |
1991年 | 11篇 |
1990年 | 21篇 |
1989年 | 16篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 4篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有2148条查询结果,搜索用时 406 毫秒
41.
Moon Hwan Cho Seung Chang Yang Nam Keun Yang Yongjin Kang Jaejung Ko 《Journal of inclusion phenomena and macrocyclic chemistry》1998,30(4):279-287
The thermodynamic parameters for the interaction of Cu2+, Ni2+, Co2+, Cd2+, andAg+ with the new title ligand have been determined by titration calorimetry in 50% THF–methanol (V/V) at 25 °C.Ag+ exhibited remarkably higher complexation selectivity.Ag+ and several transition metal ions have been transportedusing this ligand as carrier in a bulk liquid membrane. CompetitiveAg+–M2+ transport studies have also beencarried out for the same system. In this membrane transport study, high transport of Ag+ was observed in both single and competitiveAg+–M2+ transport studies. The complexformation of N,N-bis[o-(diphenylphosphino)benzylidene]ethylenediamine (P2N2) with silver,[Ag(P2N2)] (NO3), (1) is reported. Complex 1 has been characterized by X-ray crystallography. 1 ismonoclinic, space group P21/n (No. 14), with cell dimensionsa = 13.398(4) , b=12.577(5) , c = 21.521(4) , =100.14(2) , V = 3570(2) 3 and Z = 4. 相似文献
42.
43.
蛋白质变性机理与变性时的热力学参数研究进展 总被引:7,自引:0,他引:7
生物大分子是近年来生命科学的研究热点和难点之一,而对蛋白质变性的研究有助于深刻揭示生命现象的机理.利用光谱学和热力学可以分别从微观和宏观角度对蛋白质变性进行研究,并由此得到表征蛋白质变性的热力学参数.这对深入了解蛋白质的折叠与伸展、变性机理、结构稳定性及生命体的新陈代谢等问题具有很大意义.近年来,国内外学者在此方面做了大量的工作,主要涉及蛋白质在水溶液中的变性机理、在有变性剂存在下水溶液中的变性机理及在含有其它物质水溶液中的变性机理.用来表征蛋白质变性的热力学参数有热容、变性自由能、变性焓和变性熵等.本文对这些研究进行了概述. 相似文献
44.
Jose L. Zurita Maria L. G. de Soria Miguel A. Postigo Miguel Katz 《Journal of solution chemistry》1987,16(2):163-170
Densities, viscosities, enthalpies, vapor-liquid equilibria, and surface tensions were determined at 25°C for the 2-propanol+dichloromethane system. From the experimental results excess volumes, viscosities, enthalpies, Gibbs energies, and excess surface tensions were calculated. An attempt has been made to explain the observed deviations from ideal behavior on the basis of intermolecular interactions. 相似文献
45.
The main thermodynamic characteristics of the adsorption of haloadamantanes on graphitized thermal carbon black were determined by experimental measurements and by calculations in terms of molecular-statistic theory of adsorption. Using experimental data, the Kovac retention indices were calculated and the optimum conditions for gas-chromatographic separation of haloadamantanes on stationary phases with different polarity were elucidated. The influence of the cage effect in the adamantane unit on the chromatographic properties of haloadamantanes was established. 相似文献
46.
硅钨杂多酸与牛血红蛋白相互作用的研究 总被引:4,自引:0,他引:4
多金属氧酸盐作为抗艾滋病病毒、抗流感病毒和抗肿瘤的药物,引起了人们对多金属氧酸与蛋白质之间相互作用的极大关注。蛋白质空间结构的任何变化引起的构象变化都意味着蛋白质分子的活性改变,因此,蛋白质与内源性化合物及许多药物分子之间相互作用的研究一直受到人们关注[1 ̄3]。血红蛋白是动物及人体内执行输氧任务的蛋白质,是生命机体进行各种生理活动的主要承担者。血红蛋白分子中每条α链和β链含有的色氨酸(Trp)残基分别为α-14Trp、β-15Trp、β-37Trp。Alpert[4]等认为位于疏水腔内的β-37Trp是血红蛋白内源荧光的主要来源,同时β… 相似文献
47.
Monte Carlo simulations of the bond fluctuation model of symmetrical polymer blends confined between two neutral repulsive walls are presented for chain lengthN
A=N
B=32 and a wide range of film thicknessD (fromD=8 toD=48 in units of the lattice spacing). The critical temperaturesT
c
(D) of unmixing are located by finite-size scaling methods, and it is shown that
, wherev
30.63 is the correlation length exponent of the three-dimensional Ising model universality class. Contrary to this result, it is argued that the critical behavior of the films is ruled by two-dimensional exponents, e.g., the coexistence curve (difference in volume fraction of A-rich and A-poor phases) scales as
, where
2 is the critical exponent of the two-dimensional Ising universality class (
2=1/8). Since for largeD this asymptotic critical behavior is confined to an extremely narrow vicinity ofT
c
(D), one observes in practice effective exponents which gradually cross over from
2 to
3 with increasing film thickness. This anomalous flattening of the coexistence curve should be observable experimentally. 相似文献
48.
本文测定了新疆产新疆党参,新疆元胡等12种中草药中十种微量金属元素的含量.结果表明这些中草药中具有显著生理活性的Zn、Fe、Cu、Mn等元素.它们的含量除了个别样品外均大于或接近于国内其它地区所产的同种中草药、根据冠心病病因的Zn/Cu值假说和微量金属元素的含量关系,新疆产12种中草药也可用于防治冠心病. 相似文献
49.
Vaishali Tiwari 《Thermochimica Acta》2006,443(2):206-211
Densities ρ and viscosities η of two hydroxamic acids, N-phenyl-2-chlorobenzo- and N-o-tolyl-4-chlorobenzo-, have been determined as a function of their concentration in aqueous acetone solution at temperatures 303.15 and 313.15 K. Apparent molar volumes, standard-state partial molar volumes and relative viscosities have been calculated. The viscosity data have been analyzed using Jones-Dole equation. The activation thermodynamic parameters of viscous flow have been evaluated using Feakins equation. These were obtained to throw light on the mechanism of viscous flow. Thermodynamic interactions in solutions have been studied in terms of a number of excess functions calculated from the experimental data. The effect of hydroxamic acid concentration and temperature on these parameters has been discussed. The results were interpreted in the light of solute-solvent interactions in aquo-organic media. 相似文献
50.