全文获取类型
收费全文 | 514820篇 |
免费 | 2942篇 |
国内免费 | 900篇 |
专业分类
化学 | 234938篇 |
晶体学 | 7750篇 |
力学 | 29338篇 |
综合类 | 7篇 |
数学 | 78998篇 |
物理学 | 167631篇 |
出版年
2021年 | 4078篇 |
2020年 | 4527篇 |
2019年 | 5375篇 |
2018年 | 12594篇 |
2017年 | 13018篇 |
2016年 | 12659篇 |
2015年 | 5605篇 |
2014年 | 9390篇 |
2013年 | 19262篇 |
2012年 | 18235篇 |
2011年 | 25923篇 |
2010年 | 18489篇 |
2009年 | 18711篇 |
2008年 | 23789篇 |
2007年 | 26031篇 |
2006年 | 16100篇 |
2005年 | 17405篇 |
2004年 | 15051篇 |
2003年 | 14268篇 |
2002年 | 13287篇 |
2001年 | 12894篇 |
2000年 | 10296篇 |
1999年 | 7596篇 |
1998年 | 6738篇 |
1997年 | 6578篇 |
1996年 | 6145篇 |
1995年 | 5586篇 |
1994年 | 5498篇 |
1993年 | 5369篇 |
1992年 | 5718篇 |
1991年 | 6074篇 |
1990年 | 5985篇 |
1989年 | 5787篇 |
1988年 | 5639篇 |
1987年 | 5704篇 |
1986年 | 5262篇 |
1985年 | 6424篇 |
1984年 | 6881篇 |
1983年 | 5777篇 |
1982年 | 6164篇 |
1981年 | 5838篇 |
1980年 | 5481篇 |
1979年 | 6022篇 |
1978年 | 6204篇 |
1977年 | 6222篇 |
1976年 | 6415篇 |
1975年 | 5920篇 |
1974年 | 5757篇 |
1973年 | 6075篇 |
1972年 | 4608篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A nanoscale
multivalent platinum drug based on a poly(amidoamine) [PAMAM] dendrimer (generation
4.5, carboxylate surface) has been synthesized and fully characterized using
a variety of spectroscopic, chromatographic and thermal methods. Treatment
of the dendrimer with an aqueous solution containing an excess diaquo(cis-1,2-diaminocyclohexane)platinum(II) produces
a conjugate containing approximately forty (diaminocyclohexane)platinum(II)
moieties at the surface of the dendrimer. This material undergoes smooth two-stage
thermal decomposition to provide residual platinum oxide reflecting the platinum
loading in the drug. 相似文献
992.
A. Yu. Shvykin V. V. Platonov V. A. Proskuryakov K. B. Chilachava S. I. Podshibyakin 《Russian Journal of Applied Chemistry》2006,79(10):1576-1580
A method of synthesis of acetylacetonated humin-like compounds was developed. The effect of modification on the sorption capacity of humin-like compounds with respect to heavy metals was studied. 相似文献
993.
T. Yu. Gumerov A. F. Dobrynina R. A. Yusupov V. P. Barabanov 《Russian Journal of Applied Chemistry》2006,79(12):1935-1939
The behavior of real disperse systems with organic impurities was examined under conditions of destabilization by inorganic coagulants. A number of physicochemical methods of analysis and a simulation method were used to identify the character and type of the complexes formed and to calculate their stability constants. 相似文献
994.
995.
Chalcones have been synthesized under sonochemical irradiation by Claisen-Schmidt condensation between benzaldehyde and acetophenone. Two basic activated carbons (Na and Cs-Norit) have been used as catalysts. The effect of the ultrasound activation has been studied. A substantial enhancing effect in the yield was observed when the carbon catalyst was activated under ultrasonic waves. This “green” method (combination of alkaline-doped carbon catalyst and ultrasound waves) has been applied to the synthesis of several chalcones with antibacterial properties achieving, in all cases, excellent activities and selectivities. A comparative study under non-sonic activation has showed that the yields are lower in silent conditions, indicating that the sonication exerts a positive effect on the activity of the catalyst. Cs-doped carbon is presented as the optimum catalyst, giving excellent activity for this type of condensation. Cs-Norit carbon catalyst can compete with the traditional NaOH/EtOH when the reaction is carried out under ultrasounds. The role of solvent in this reaction was studied with ethanol. High conversion was obtained in absence of solvent. The carbons were characterized by thermal analysis, nitrogen adsorption and X-ray photoelectron spectroscopy. 相似文献
996.
997.
Girard V Farrenq R Sorokin E Sorokina IT Guelachvili G Picqué N 《Chemical physics letters》2006,419(4-6):584-588
The spectral dynamics of a mid-infrared multimode Cr(2+):ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C(2)H(2) in natural isotopic abundance are recorded around 4000 cm(-1) with kilometric absorption path lengths and sensitivities better than 3 10(-8) cm(-1). Two cold bands are newly identified and assigned to the ν(1)+ν(4) (1) and ν(3)+ν(5) (1) transitions of (12)C(13)CH(2). The ν(1)+ν(5) (1) band of (12)C(2)HD and fourteen (12)C(2)H(2) bands are observed, among which for the first time ν(2)+2ν(4) (2)+ν(5) (-1). 相似文献
998.
Yu. D. Perfiliev V. S. Rusakov L. A. Kulikov A. A. Kamnev K. Alkhatib 《Hyperfine Interactions》2006,167(1-3):881-885
To explain line broadening in emission Mössbauer spectra as compared to the corresponding absorber measurements, the model of trapped electrons has been proposed. Auger electrons (emitted, e.g. after electron capture by 57Co or after the converted isomeric transition of 119mSn), as well as secondary electrons, may be trapped in the proximity to the nucleogenic ion. Electrons captured by lattice traps at different distances from the daughter ion induce an asymmetric distribution of quadrupole splitting in the resulting emission spectra, as shown in a few examples. This model is supported by estimates of quadrupole splitting values which may be caused by such trapped electrons located at specified distances from the nucleogenic atom. 相似文献
999.
A Monte Carlo simulation method is used to study thermal desorption of gas molecules from mixed adlayers containing two species. The effects of lateral interactions among adatoms and initial surface coverage on the desorption spectra are examined. It is shown that attractive lateral interactions lead to sharper peaks and that desorption occurs at high temperatures, whereas repulsive interactions lead to multiple peak spectra. It is found that interactions between unlike molecules affect the spectra for species with lower desorption energy only, and that the two species desorb together only in certain cases. Lateral interactions also affect the desorption kinetics significantly and very different behavior for the two species may be obtained. 相似文献
1000.