全文获取类型
收费全文 | 26391篇 |
免费 | 582篇 |
国内免费 | 103篇 |
专业分类
化学 | 14821篇 |
晶体学 | 159篇 |
力学 | 794篇 |
综合类 | 9篇 |
数学 | 3654篇 |
物理学 | 7639篇 |
出版年
2023年 | 123篇 |
2022年 | 356篇 |
2021年 | 431篇 |
2020年 | 385篇 |
2019年 | 344篇 |
2018年 | 444篇 |
2017年 | 396篇 |
2016年 | 694篇 |
2015年 | 562篇 |
2014年 | 659篇 |
2013年 | 1063篇 |
2012年 | 1346篇 |
2011年 | 1510篇 |
2010年 | 885篇 |
2009年 | 819篇 |
2008年 | 1293篇 |
2007年 | 1261篇 |
2006年 | 1149篇 |
2005年 | 1555篇 |
2004年 | 1584篇 |
2003年 | 1103篇 |
2002年 | 756篇 |
2001年 | 634篇 |
2000年 | 564篇 |
1999年 | 380篇 |
1998年 | 308篇 |
1997年 | 314篇 |
1996年 | 371篇 |
1995年 | 334篇 |
1994年 | 321篇 |
1993年 | 344篇 |
1992年 | 330篇 |
1991年 | 266篇 |
1990年 | 224篇 |
1989年 | 212篇 |
1988年 | 183篇 |
1987年 | 181篇 |
1986年 | 178篇 |
1985年 | 235篇 |
1984年 | 221篇 |
1983年 | 192篇 |
1982年 | 191篇 |
1981年 | 186篇 |
1980年 | 171篇 |
1979年 | 155篇 |
1978年 | 180篇 |
1977年 | 141篇 |
1976年 | 134篇 |
1974年 | 133篇 |
1973年 | 125篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
de Souza P. A. Garg V. K. Klingelhöfer G. Gellert R. Gütlich P. 《Hyperfine Interactions》2002,139(1-4):705-714
A portable Mössbauer spectrometer, developed for extraterrestrial applications, opens up new industrial applications of MBS. But for industrial applications, an available tool for fast data analysis is also required, and it should be easy to handle. The analysis of Mössbauer spectra and their parameters is a barrier for the popularity of this wide-applicable spectroscopic technique in industry. Based on experience, the analysis of a Mössbauer spectrum is time-consuming and requires the dedication of a specialist. However, the analysis of Mössbauer spectra, from the fitting to the identification of the sample phases, can be faster using by genetic algorithms, fuzzy logic and artificial neural networks. Industrial applications are very specific ones and the data analysis can be performed using these algorithms. In combination with an automatic analysis, the Mössbauer spectrometer can be used as a probe instrument which covers the main industrial needs for an on-line monitoring of its products, processes and case studies. Some of these real industrial applications will be discussed. 相似文献
23.
The occurrence and formation of black spots areas in PolyLED devices has been studied by time-of-flight SIMS (TOFSIMS). The composition, shape and position of the black spots is visualised by three-dimensional (3D)-TOFSIMS depth-profiling. It has been established that the formation of non-emissive spots is due to the growth of aluminium oxide clusters at the AlBa/polymer interface. Electron injection in the black spots is lost by the resulting local increase of the resistivity of the cathode. 相似文献
24.
Thierry de la Rue 《Bulletin of the Brazilian Mathematical Society》2006,37(4):503-521
V.A. Rohlin asked in 1949 whether 2-fold mixing implies 3-fold mixing for a stationary process (ξi )i2ℤ, and the question remains open today. In 1978, F. Ledrappier exhibited a counterexample to the 2-fold mixing implies 3-fold
mixing problem, the socalled 3-dot system, but in the context of stationary random fields indexed by ℤ2.
In this work, we first present an attempt to adapt Ledrappier's construction to the onedimensional case, which finally leads
to a stationary process which is 2-fold but not 3-fold mixing conditionally to the σ-algebra generated by some factor process. Then, using arguments coming from the theory of joinings, we will give some strong obstacles proving that Ledrappier's counterexample
can not be fully adapted to one-dimensional stationary processes. 相似文献
25.
Robert de Levie 《The Chemical Educator》2002,7(3):132-135
Using contemporary accounts, we describe the scope of the Henderson approximation, and its relationship to the mass action law of Guldberg & Waage. The Henderson approximation, apparently written in logarithmic form by Hasselbalch, has the same form as the mass action law, but has a completely different meaning and a much more restricted range of applicability. The Guldberg-Waage law is the fundamental mass action relationship valid for all chemical equilibria, whereas the Henderson approximation is useful only within a limited range of a sufficiently concentrated two-component buffer mixture. 相似文献
26.
J.-C. Thomas L. Achouri J. Äystö R. Béraud B. Blank G. Canchel S. Czajkowski P. Dendooven A. Ensallem J. Giovinazzo N. Guillet J. Honkanen A. Jokinen A. Laird M. Lewitowicz C. Longour F. de Oliveira Santos K. Peräjärvi M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):419-435
27.
Affine Arithmetic: Concepts and Applications 总被引:2,自引:0,他引:2
Affine arithmetic is a model for self-validated numerical computation that keeps track of first-order correlations between computed and input quantities. We explain the main concepts in affine arithmetic and how it handles the dependency problem in standard interval arithmetic. We also describe some of its applications. 相似文献
28.
29.
W M Niessen M A de Kraa E R Verheij P J Bergers G F La Vos U R Tjaden J van der Greef 《Rapid communications in mass spectrometry : RCM》1989,3(1):1-4
On-line sample pretreatment by means of the phase-system switching approach is an interesting technique for the analysis of aqueous samples, e.g., plasma, by means of supercritical-fluid chromatography. In order to analyse plasma samples the following analytical procedure is used. The plasma sample is injected on to a short precolumn, which is washed with water and subsequently dried with nitrogen. Next, the solutes are desorbed with the supercritical mobile phase, analysed with packed-column supercritical-fluid chromatography and detected with either a UV detector or a mass spectrometer, equipped with a moving-belt interface. The herbicide diuron is selected as a test compound to study the feasibility of this approach. Using a selective detector the procedure is sufficiently sensitive to detect diuron in plasma, but not appropriate to detect the diuron metabolites in a post-mortem plasma sample. These have been identified with liquid chromatography/mass spectrometry. The detection limit of diuron in plasma using the procedure described is about 30 ng/mL. 相似文献
30.
Tereza C. R. dos Santos Ricardo Q. Aucélio Reinaldo C. Campos 《Mikrochimica acta》2003,142(1-2):63-66
A simple and direct spectrofluorimetric method has been developed for the determination of aluminum using alizarin red PS
(1,2,4-trihydroxy 9,10-anthraquinone-3-sulfonic acid). The method is based on the strong fluorescence (480/564 nm) of Al3+ and alizarin red. Experimental parameters such as pH, concentration of the ligand, ionic strength of the solution, reaction
time and temperature were optimized in order to maximize the analytical signal. Interferences of several ions (anions and
cations) were studied and evaluated. The linear range of the method extends from 3 to 100 μg L−1. Limit of detection (3sb) was 0.9 μg L−1. The method was tested with a silicate certified reference material. Interferences were eliminated by a liquid extraction
with cupferron.
Author for correspondence. E-mail: aucelior@rdc.puc-rio.br
Received September 10, 2002; accepted January 15, 2003
Published online May 5, 2003 相似文献