全文获取类型
收费全文 | 1805篇 |
免费 | 27篇 |
国内免费 | 9篇 |
专业分类
化学 | 982篇 |
晶体学 | 18篇 |
力学 | 59篇 |
数学 | 198篇 |
物理学 | 584篇 |
出版年
2020年 | 13篇 |
2019年 | 10篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 15篇 |
2013年 | 61篇 |
2012年 | 80篇 |
2011年 | 83篇 |
2010年 | 36篇 |
2009年 | 38篇 |
2008年 | 79篇 |
2007年 | 84篇 |
2006年 | 75篇 |
2005年 | 81篇 |
2004年 | 65篇 |
2003年 | 40篇 |
2002年 | 46篇 |
2001年 | 40篇 |
2000年 | 36篇 |
1999年 | 19篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 29篇 |
1994年 | 42篇 |
1993年 | 51篇 |
1992年 | 40篇 |
1991年 | 37篇 |
1990年 | 26篇 |
1989年 | 35篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 34篇 |
1984年 | 22篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 29篇 |
1980年 | 24篇 |
1979年 | 28篇 |
1978年 | 27篇 |
1977年 | 27篇 |
1976年 | 27篇 |
1975年 | 28篇 |
1974年 | 31篇 |
1973年 | 35篇 |
1972年 | 22篇 |
1971年 | 12篇 |
1968年 | 11篇 |
1967年 | 10篇 |
排序方式: 共有1841条查询结果,搜索用时 0 毫秒
41.
N. S. Allen J. F. McKellar G. O. Phillips D. G. M. Wood 《Journal of polymer science. Part A, Polymer chemistry》1974,12(11):2647-2650
Phosphorescence from polyolefins was studied from the aspects of excitation and emission wavelength and lifetime. Effects of photochemical oxidation on polypropylene phosphorescence are discussed in contrast to the effects of thermal oxidation. 相似文献
42.
The fluorescence decay of the tertiary aliphatic animes trimethylamine (TMA), triethylamine (TEA) and tri-n-propylamine (TPA) in the vapour phase excited between 260 and 215 nm has been shown to consist of a single, wavelength-dependent, component when the first excited state is uniquely excited, but two components when the first and second excited states are simultaneously excited. This dual exponentiality persists at pressures as low as 10 mTorr, and it is argued that the two-component decay does not arise from collisional vibrational relaxation. 相似文献
43.
Buck KK Gerhardt NI Dungan SR Phillips RJ 《Journal of colloid and interface science》2001,234(2):400-409
The effect of solute concentration on the equilibrium partitioning of sphere-like, colloidal solutes in stiff polymer hydrogels is examined theoretically and experimentally. The theoretical development is a statistical mechanics approach, and allows quantitative calculations to be performed to determine the concentration-dependent partition coefficient correct to first order in solute concentration at specific surface charge densities. The theory predicts that repulsive steric and/or electrostatic solute-fiber interactions exclude solute from the gel phase, but that repulsive solute-solute interactions cause partitioning into the gel to increase with increasing solute concentration. These trends are enhanced for larger solutes, increased fiber volume fractions, or stronger electrostatic repulsion. Partition coefficients have also been measured for two proteins, bovine serum albumin (BSA) and alpha-lactalbumin (ALA), in a system consisting of a salt solution and cubes of agarose hydrogel. To investigate the effect of electrostatic interactions, the experiments were performed at 0.15 M KCl and 0.01 M KCl. The theory underpredicts the strong electrostatic repulsion between BSA macromolecules at the lower ionic strength. The experimental results for ALA show the influence of an attractive interaction between the protein macromolecules, in addition to hard-sphere repulsive and electrostatic interactions. Copyright 2001 Academic Press. 相似文献
44.
45.
46.
47.
48.
49.
Phosphazene rings with (dimethylamino)ethoxy (1, 2), pyridylmethoxy (3), or (dimethylamino)propoxy (4) chains were synthesized and quaternized at the substitutent nitrogen by treatment with methyl iodide at 35 degrees C over 3-6 h to give polyiodo salts, 5-8. Subsequent metathesis with LiN(SO(2)CF(3))(2) or NaBF(4) gave the respective ionic salts, 9-13. The amide salts, 9-12, were viscous liquids with pour points at 55-100 degrees C, and the tetrafluoroborate salt, 13, was a solid, mp 168 degrees C. The compositions of 2 and 5-13 were confirmed by elemental analysis and spectroscopic methods. Compounds 1, 2, and 4 were viscous liquids (d(25) = 1.67 g cm(-3); eta(25) = 0.76-1.56 mPa s(-1) ) with pour points at approximately 15 degrees C. The solid polyquaternary salts, 5-8, melted at 130-194 degrees C. The ionic liquids, 9-12, had an average density of approximately 1.73 g cm(-3) at 25 degrees C, and viscosities (25 degrees C) ranged between 68.3 and 139.2 mPa s(-1). A plot of the viscosities of 9-12 vs temperature revealed an almost linear correlation between 55 and 120 degrees C. Friction and wear properties of water with 0.25 wt % of 9-12 as boundary lubricant additives were evaluated on Si(3)N(4)/Si(3)N(4) ceramic interfaces. The most significant observation is that they caused a decrease in the running-in period. 相似文献
50.
D. Colin Phillips Sandra Spewock William M. Alvino 《Journal of polymer science. Part A, Polymer chemistry》1976,14(5):1137-1150
4-Aminophthalic acid has been polymerized in almost quantitative yield to low molecular weight polymer by electrochemical initiation at a platinum anode. Systems involving the acid, amine salt, and the ammonium salt have been explored; the acid and/or the amine salt of the acid provides the best means of obtaining polymer. Maximum molecular weight is attained in a very short time at low current densities (~2 hr at 50 mA). Thermogravimetric data indicate a temperature stability comparable to polyamide-imide polymers (400°C). Long reaction times and high current densities decrease molecular weight and polymer yield. 相似文献