全文获取类型
收费全文 | 34732篇 |
免费 | 1155篇 |
国内免费 | 37篇 |
专业分类
化学 | 23754篇 |
晶体学 | 262篇 |
力学 | 629篇 |
数学 | 4837篇 |
物理学 | 6442篇 |
出版年
2023年 | 273篇 |
2022年 | 273篇 |
2021年 | 430篇 |
2020年 | 588篇 |
2019年 | 559篇 |
2018年 | 726篇 |
2017年 | 671篇 |
2016年 | 1322篇 |
2015年 | 1067篇 |
2014年 | 1128篇 |
2013年 | 2243篇 |
2012年 | 2472篇 |
2011年 | 2670篇 |
2010年 | 1535篇 |
2009年 | 1306篇 |
2008年 | 2207篇 |
2007年 | 2167篇 |
2006年 | 1888篇 |
2005年 | 1721篇 |
2004年 | 1388篇 |
2003年 | 1083篇 |
2002年 | 983篇 |
2001年 | 720篇 |
2000年 | 628篇 |
1999年 | 468篇 |
1998年 | 337篇 |
1997年 | 262篇 |
1996年 | 378篇 |
1995年 | 258篇 |
1994年 | 251篇 |
1993年 | 296篇 |
1992年 | 266篇 |
1991年 | 183篇 |
1990年 | 164篇 |
1989年 | 151篇 |
1988年 | 153篇 |
1987年 | 143篇 |
1986年 | 141篇 |
1985年 | 196篇 |
1984年 | 184篇 |
1983年 | 142篇 |
1982年 | 131篇 |
1981年 | 114篇 |
1980年 | 95篇 |
1979年 | 105篇 |
1978年 | 102篇 |
1977年 | 99篇 |
1976年 | 91篇 |
1975年 | 83篇 |
1973年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Summary A new gas chromatographic method using an automatic purge-and-trap system coupled to a GC with mass selective detection to analyze styrene at the parts-per-trillions (ng kg–1) level is described. The method shows a good sensitivity and the detection limit is 10 ng kg–1 with a relative standard deviation (RSD) of 4.7% for 164 ng kg–1 styrene in olive oil. This analytical method has been successfully applied to the analysis of styrene in extra-virgin olive oil from the European market. 相似文献
73.
Precipitate-forming chemical reactions have been studied in chemically cross-linked poly(vinyl alcohol) gel medium. One of the reactive components was incorporated into the gel, the other was allowed to diffuse into it. Depending on the experimental conditions the reaction-diffusion process often results in patterns of different type. Experiments performed in tubes and in thin layers were carried out in order to investigate the effects of various factors (cross-linking density, swelling degree as well as the concentrations of the outer and inner electrolytes) on the morphologies of the precipitate patterns. It was found that precipitation occurs not only in the Liesegang bands, but also between bands. Beside Liesegang-type structures, tree-like patterns have been observed, showing a characteristic periodicity in the density profile obtained by digitalized image analyses. 相似文献
74.
B. Vizoso I. R. Matías M. López-Amo M. A. Muriel J. M. López-Higuera 《Optical and Quantum Electronics》1995,27(10):847-857
The design of a double-parallel amplified recirculating optical delay line utilizing an erbium-doped fibre amplifier for a fibre optical bus is described. This structure is used for amplifying, equalizing and filtering multicarrier signals coming from optoelectronic units attached to fibre couplers. The use of this structure for a hybrid multimode-singlemode fibre bus that includes optoelectronic units for sensors is also demonstrated. 相似文献
75.
Miroslav Menšík 《Czechoslovak Journal of Physics》1998,48(4):469-475
A time solution of the excimer-ion pair system is presented here with a special attention to the time asymptote.
Presented at the Czech-Israeli-German Symposium “Dynamical Processes in Condensed Molecular Systems”, Prague, Czech Republic,
26–30 May 1997.
This work was supported by the grant No. C 1050601 of the Grant Agency of the Academy of Sciences of the Czech Republic. 相似文献
76.
77.
A special two-sided condition for the incremental magnetic reluctivity is introduced which guarantees the unique existence of both the weak and the approximate solutions of the nonlinear stationary magnetic field distributed on a region composed of different media, as well as a certain estimate of the error between the two solutions. The condition, being discussed from the physical as well as the mathematical point of view, can be easily verified and is fulfilled for various magnetic reluctivity models used in electrotechnical practice. 相似文献
78.
79.
It is shown that the non-trivial cocycles on simple Lie algebras may be used to introduce antisymmetric multibrackets which
lead to higher-order Lie algebras, the definition of which is given. Their generalised Jacobi identities turn out to be satisfied
by the antisymmetric tensors (or higher-order “structure constants”) which characterise the Lie algebra cocycles. This analysis
allows us to present a classification of the higher-order simple Lie algebras as well as a constructive procedure for them.
Our results are synthesised by the introduction of a single, complete BRST operator associated with each simple algebra.
Received: 3 June 1996 / Accepted: 8 November 1996 相似文献
80.
Carmen Izquierdo María Luisa Moyá Jose Luis Usero Julio Casado 《Monatshefte für Chemie / Chemical Monthly》1992,123(5):383-389
Summary A simple working method for the estimation of the aggregation numbers and core radii from weight measurements of sodium bis-2-ethylhexylsulphosuccinate (aerosol-OT orAOT)/decane/water microemulsions of several compositions is proposed.Starting out from the hypotheses that (i) the density of the water inside the droplets is the same as that of free water, (ii) all the surfactant is localized as interface, and (iii) the penetration of the organic phase into the interface is negligible, values for the aggregation number and core radii comparable to those determined using more sophisticated methods were obtained.The results/methodological simplicity ratio may be of great advantage in kinetic work on reaction mechanisms in microemulsions.
Abschätzung von Aggregationszahl und Radius von Mikroemulsionen
Zusammenfassung Es wird eine einfache Methode zur Abschätzung von Aggregationszahl und Core-Radius von Mikroemulsionen aus Gewichtsmessungen von Natriumbis-2-ethylhexylsulphosuccinat (aerosol-OT oderAOT)/Decan/Wasser-Mikroemulsionen verschiedener Zusammensetzung vorgeschlagen. Unter den Annahmen, daß (i) die Dichte von Wasser innerhalb der Aggregationen die gleiche als bei freiem Wasser ist, (ii) das ganze Emulsionsmittel in der Grenzfläche vorliegt und (iii) das Eindringen der organischen Phase in die Grenzfläche vernachlässigbar ist, können Werte für Aggregationszahlen und Core-Radien erhalten werden, die durchaus mit entsprechenden Werten aus aufwendigeren Methoden vergleichbar sind. Das Leistungsverhältnis (Ergebnisse/geringer Aufwand) ist sehr vorteilhaft und macht die Methode für kinetische Arbeiten zur Bestimmung von Reaktionsmechanismen in Mikroemulsionen interessant.相似文献