全文获取类型
收费全文 | 3237篇 |
免费 | 233篇 |
国内免费 | 560篇 |
专业分类
化学 | 3404篇 |
晶体学 | 79篇 |
力学 | 47篇 |
综合类 | 46篇 |
数学 | 5篇 |
物理学 | 449篇 |
出版年
2024年 | 5篇 |
2023年 | 37篇 |
2022年 | 73篇 |
2021年 | 103篇 |
2020年 | 121篇 |
2019年 | 103篇 |
2018年 | 98篇 |
2017年 | 123篇 |
2016年 | 122篇 |
2015年 | 123篇 |
2014年 | 132篇 |
2013年 | 371篇 |
2012年 | 191篇 |
2011年 | 158篇 |
2010年 | 153篇 |
2009年 | 169篇 |
2008年 | 153篇 |
2007年 | 173篇 |
2006年 | 166篇 |
2005年 | 169篇 |
2004年 | 155篇 |
2003年 | 132篇 |
2002年 | 127篇 |
2001年 | 89篇 |
2000年 | 66篇 |
1999年 | 87篇 |
1998年 | 85篇 |
1997年 | 78篇 |
1996年 | 74篇 |
1995年 | 58篇 |
1994年 | 52篇 |
1993年 | 33篇 |
1992年 | 41篇 |
1991年 | 22篇 |
1990年 | 29篇 |
1989年 | 22篇 |
1988年 | 23篇 |
1987年 | 13篇 |
1986年 | 20篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1973年 | 7篇 |
1972年 | 3篇 |
排序方式: 共有4030条查询结果,搜索用时 31 毫秒
991.
Baldé CP Hereijgers BP Bitter JH de Jong KP 《Angewandte Chemie (International ed. in English)》2006,45(21):3501-3503
992.
R. G. Bulgakov S. P. Kuleshov Z. S. Valiullina B. A. Mustafin 《Russian Chemical Bulletin》1999,48(6):1091-1094
Chemiluminescence (CL) of triphenylmethyl organometallics (TPM), Ph3CNa, Ph3CMgCl, and Ph3CLnCl2 (Ln=Cd, Eu, and Dy), in THF and toluene during oxidation by O2 and the (NH4)2Ce(NO3)6 complex was found. The first CL is caused by the luminescence of two emitters: (Ph3C)*, emitting in the green spectral region (λmax=524, 550 nm), and an unstable product of substitution of the hydrogen atom in the phenyl ring of the Ph3C radical, emitting in the red region (λmax=580±20 nm). The emitter of the second CL, Ph3C.*, is generated in the elementary electron transfer from the Ph3C− anion to CeIV, reducing the latter to CeIII.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1102–1105, June, 1999. 相似文献
993.
994.
Hensinger W. K. Truscott A. G. Rubinsztein-Dunlop H. Heckenberg N. R. 《Optical and Quantum Electronics》1999,31(5-7):391-403
We have observed dramatic line intensity variations in the saturation spectrum of Rb85 and Rb87 due to magnetic fields of magnitude on the order of 100 nT. These variations are detected by rotation of the plane of polarisation of the pump beam and probe beam relative to the magnetic field axis. A modified rate equation model is proposed which accounts for all experimentally observed features. Our results may explain some discrepancies between theory and experiment observed by other authors. Furthermore, our study should lead to a better understanding of the processes involved in saturation spectroscopy. 相似文献
995.
Rapid liquid chromatographic procedures are proposed for analysis of paracetamol and orphenadrine citrate in pharmaceutical preparations and human serum using acetonitrile: water (50:50) as a mobile phase, adjusting pH to 2.6, UV detection at 215 nm and propylparaben sodium as internal standard. The advantages of this method include good and rapid separation, well resolved peaks, and only a small amount of sample is required for assay and adequate precision. The method showed good linearity in the range of 6 to 10000 ng/mL for paracetamol serum concentrations with a correlation coefficient 0.9999 (inter and intra day CV < 3.15) and in the range 3–10000 ng/mL for orphenadrine citrate serum concentrations with a correlation coefficient of 0.9999 (inter and intra day CV < 3.58). The recovery of paracetamol and orphenadrine citrate was > 96.9% and > 96.7%, respectively. The proposed method may be used for the quantitative analysis of paracetamol and orphenadrine citrate alone or in combination from raw materials, in bulk drugs, dosage formulations and in serum. 相似文献
996.
Alp H. Alidedeoglu Adam W. York Dale A. Rosado Charles L. McCormick Sarah E. Morgan 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):3052-3061
The synthesis of well‐defined carboxylic acid‐functionalized glycopolymers prepared via one‐step postpolymerization modification of poly(N‐[3‐aminopropyl] methacrylamide) (PAPMA), a water‐soluble primary amine methacrylamide, in aqueous medium is demonstrated. PAPMA was first polymerized via aqueous reversible addition‐fragmentation chain transfer polymerization in aqueous buffer using 4‐cyanopentanoic acid dithiobenzoate as the chain transfer agent and 4,4′‐azobis(4‐cyanovaleric acid) (V‐501) as the initiator at 70 °C. The resulting well‐defined PAPMA was then conjugated with D ‐glucuronic acid sodium salt through reductive amination in alkaline medium (pH 8.5) at 45 °C. The successful bioconjugation was proven through proton (1H) and carbon (13C) nuclear magnetic resonance spectroscopy and matrix‐assisted laser desorption/ionization time of flight mass spectrometry analysis, which indicated near quantitative conversion. A similar bioconjugation reaction was conducted with poly(2‐aminoethyl methacrylate) (PAEMA) and poly(2‐aminoethyl methacrylate‐b‐poly(N‐[2‐hydroxypropyl]methacrylamide) (PAEMA‐b‐PHPMA). For the PAEMA homopolymers and block copolymers, however, lower conversion was obtained, most likely because of degradation reactions of PAEMA in alkaline medium. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3052–3061, 2010 相似文献
997.
The phase equilibria of surfactant aqueous mixtures, hexadecyltrimethylammonium bromide and sodium dodecyl sulfate, have
been studied by polarizing microscopy, quasielastic light scattering, conductivity, potentiometric, electrophoretic, and surface
tension measurements. Adsorption at the air/solution interface, association and precipitation in bulk solution strongly depended
on the molar ratio and the concentration of surfactants. Catanionic vesicles coexisted with crystalline catanionic salts in
a broad concentration range. The relative proportions of crystallites and vesicles varied according to the concentration and
the molar ratio of the surfactants. The solid crystalline phase was progressively converted to catanionic vesicles with increasing
surfactant molar ratio. At the highest excess of one of the surfactants transition from catanionic vesicles to mixed micelles
occurred. The formation and stability of different phases are discussed in terms of surfactant molecular packing constraints
and electrostatic interactions in the headgroup region. Surfactant tail-length asymmetry and the change of electrostatic interactions
in the headgroup region from attractive to repulsive are governing factors for the transition from planar to curved bilayers.
Received: 9 June 1998 Accepted: 18 August 1998 相似文献
998.
CPA-矩阵法测定舒尔芬片剂中两组分的含量 总被引:2,自引:0,他引:2
本文采用CPA-矩阵法不经分离同时测定舒尔芬片剂中双氯芬酸钠和磷酸可待因的含量。计算程序用BASIC语言编制。双氯芬酸钠和磷酸可待因的平均回收率及RSD分别为99.85%,0.46%和99.80%,0.50%。方法简便、快速。 相似文献
999.
Menadione sodium bisulfite (MSB) is a stable water-soluble derivative of Vitamin K3, which is found to be able to enhance the ECL of luminol at potential of 0.88 V in phosphate buffer solution. The conditions for the enhanced ECL, such as the selection of the type of buffer solution, applied potential mode, scanning rate, the effect of pH and concentration of luminol have been investigated in detail in this paper. Under the optimum conditions, the enhanced ECL intensity is linear with the concentration of MSB over a wide range, the detection limit for MSB is 3.0 × 10−7 mol/L. The proposed method has been applied to determine the MSB in the commercial injection samples. A possible mechanism for the enhanced ECL of luminol by MSB has also been proposed. 相似文献
1000.
A. M. Saletskii A. G. Mel’nikov A. B. Pravdin V. I. Kochubei G. V. Meln’ikov 《Journal of Applied Spectroscopy》2008,75(3):402-406
We have studied the interaction between polycyclic aromatic hydrocarbons (pyrene and anthracene) with human serum albumin
(HSA) and human blood plasma. We have shown that the increase in the fluorescence intensity and the decrease in the polarity
index of pyrene on going from an aqueous solution to a pH 7.4 buffer solution of HSA suggests that polycyclic aromatic hydrocarbons
are localized in the hydrophobic microphase of the proteins. The increase in the fluorescence intensity for anthracene and
pyrene, and also the decrease in the polarity index of pyrene on going from HSA to blood plasma is connected with the fact
that polycyclic aromatic hydrocarbons can bind both to plasma proteins and to plasma lipids. When sodium dodecyl sulfate (SDS)
is added to the blood plasma in a concentration greater than the critical micelle concentration, we observe an increase in
the fluorescence intensity and the polarity index of pyrene. We hypothesize that this is connected with localization of pyrene
near the interface between the hydrophobic and hydrophilic phases of the protein-SDS system. We have established that SDS
leads to a change in the structure of blood plasma proteins and promotes escape of polycyclic aromatic hydrocarbons from the
protein globules.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 3, pp. 379–382, May–June, 2008. 相似文献