全文获取类型
收费全文 | 2512篇 |
免费 | 63篇 |
国内免费 | 19篇 |
专业分类
化学 | 1826篇 |
晶体学 | 35篇 |
力学 | 57篇 |
数学 | 301篇 |
物理学 | 375篇 |
出版年
2023年 | 21篇 |
2022年 | 26篇 |
2021年 | 50篇 |
2020年 | 33篇 |
2019年 | 33篇 |
2018年 | 25篇 |
2017年 | 29篇 |
2016年 | 55篇 |
2015年 | 40篇 |
2014年 | 54篇 |
2013年 | 134篇 |
2012年 | 145篇 |
2011年 | 181篇 |
2010年 | 93篇 |
2009年 | 80篇 |
2008年 | 132篇 |
2007年 | 137篇 |
2006年 | 145篇 |
2005年 | 129篇 |
2004年 | 125篇 |
2003年 | 110篇 |
2002年 | 80篇 |
2001年 | 64篇 |
2000年 | 37篇 |
1999年 | 23篇 |
1998年 | 23篇 |
1997年 | 35篇 |
1996年 | 42篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 22篇 |
1992年 | 25篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 27篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 31篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 16篇 |
1979年 | 18篇 |
1978年 | 16篇 |
1977年 | 13篇 |
1976年 | 26篇 |
1975年 | 18篇 |
1974年 | 15篇 |
排序方式: 共有2594条查询结果,搜索用时 15 毫秒
1.
Keller Teichmann Hans Pfeiffer W. Langenbeck A. Reid Heinrich Menzel Th. Höpner W. Mühlsteph M. Ulmann Geib R. E. Liesegang 《Colloid and polymer science》1939,87(1):100-104
Ohne Zusammenfassung 相似文献
2.
Anna Arkhireeva John N. Hay Jackie M. Lane Miguel Manzano Helen Masters Wilberforce Oware Steve J. Shaw 《Journal of Sol-Gel Science and Technology》2004,31(1-3):31-36
The synthesis of ORganically MOdified SILica (ORMOSIL) particles has been carried out using both the hydrolytic and non-hydrolytic sol-gel routes. The hybrid (nano)composites are organically modified with an alkyl or aryl group covalently bonded to silicon. Hybrids have been synthesised in an aqueous sol-gel process by a modified Stöber route, producing spherical nanoparticles with diameters in the range 50–300 nm. The size of the particles can be controlled by control of certain reaction parameters. Smaller ormosil nanoparticles can be synthesised by a base-catalysed emulsion polymerisation route, by varying the type and concentration of surfactant and precursor feed rate. In this case, particles in the size range 3.5–10 nm can be obtained. Hybrids have been synthesised from hyperbranched polyesters by encapsulation in a silica matrix using the hydrolytic sol-gel route. Optimisation of the reaction conditions allows the hybrids to be produced as isolated sub-micron spherical particles. Ormosil particles have also been synthesised using the non-hydrolytic sol-gel route, which may lead to products of different morphologies because of the different polarity of the reaction medium. Different reaction conditions were studied in order to optimise the size and shape of the particles, including choice of solvent, use of surfactants and addition of polystyrene. Dimethylsulfoxide acts as a novel oxygen donor for the catalyst-free formation of colourless silsesquioxanes. 相似文献
3.
4.
5.
Georg Süss-Fink Ulf Bodensieck Lisa Hoferkamp Gerd Rheinwald Helen Stoeckli-Evans 《Journal of Cluster Science》1992,3(4):469-478
The reaction of trirutheniumdodecacarbonyl with various thioureas was found to give, depending upon the substituents and the reaction conditions, a large variety of tri-, tetra-, penta-, and hexanuclear ruthenium clusters. The ligand systems observed in the products are derived from the thioureas employed; the fragmentation of the thiourea molecules involve N-H, C-S, C-H, and C-N activation processes. 相似文献
6.
Muonium in liquid SiCl has been observed for the first time at low temperature (−65°C) The observed polarization of muonium
is as much as 25% of the total spin polarization and shows a fast relaxation rate. 相似文献
7.
8.
John A. Mikroyannidis Helen A. Moshopoulou John A. Anastasopoulos Minas M. Stylianakis Larysa Fenenko Chihaya Adachi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(23):6790-6800
Poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐2,8‐vinylene) (PS) and poly(9,9‐dihexylfluorene‐2,7‐vinylene‐alt‐dibenzothiophene‐5,5‐dioxide‐2,8‐ vinylene) (PSO) as well as corresponding model compounds were synthesized by Heck coupling. Both the polymers and model compounds were readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane, chloroform, and toluene. The polymers showed a decomposition temperature at ~430 °C and a char yield of about 65% at 800 °C in N2. The glass‐transition temperatures of the polymers were almost identical (75–77 °C) and higher than those of the model compounds (26–45 °C). All samples absorbed around 390 nm, and their optical band gaps were 2.69–2.85 eV. They behaved as blue‐greenish light emitting materials in both solutions and thin films, with photoluminescence emission maxima at 450–483 nm and photoluminescence quantum yields of 0.52–0.72 in solution. Organic light‐emitting diodes with an indium tin oxide/poly(ethylene dioxythiophene):poly(styrene sulfonic acid)/polymer/Mg:Ag/Ag configuration with polymers PS and PSO as emitting layers showed green electroluminescence with maxima at 530 and 540 nm, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6790–6800, 2006 相似文献
9.
S. R. Grace 《Mathematische Nachrichten》1989,142(1):297-305
New theorems on the oscillatory and asymptotic behavior of solutions of the damped differential equations with deviating arguments of the form are established. 相似文献
10.
Richard A. Reid Walter A. StarkJr 《The Journal of the Operational Research Society》1988,39(2):135-139
Individual/group replacement models were used to identify the minimum-cost policy for replacing protective gloves that are utilized in product fabrication at a nuclear processing facility. Since historical data on glove longevity were not available to determine the failure-rate distribution, the classical replacement model for items that fail was modified to consider glove life as a normally distributed variable. Moreover, the absence of replacement-cost required that the classical model be transformed to incorporate the ratio of single to unit-group replacement cost. Sensitivity analysis on these two input parameter values provided guidance for the development of an appropriate replacement policy. 相似文献