全文获取类型
收费全文 | 1383篇 |
免费 | 57篇 |
国内免费 | 2篇 |
专业分类
化学 | 1178篇 |
晶体学 | 11篇 |
力学 | 13篇 |
数学 | 100篇 |
物理学 | 140篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 91篇 |
2021年 | 121篇 |
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 32篇 |
2017年 | 31篇 |
2016年 | 73篇 |
2015年 | 46篇 |
2014年 | 63篇 |
2013年 | 116篇 |
2012年 | 127篇 |
2011年 | 112篇 |
2010年 | 85篇 |
2009年 | 62篇 |
2008年 | 73篇 |
2007年 | 59篇 |
2006年 | 71篇 |
2005年 | 65篇 |
2004年 | 31篇 |
2003年 | 30篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 7篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
排序方式: 共有1442条查询结果,搜索用时 281 毫秒
961.
Malinowska Irena Gadzikowska Maria Waksmundzka-Hajnos Monika Kramek Agnieszka 《平面色谱法杂志一现代薄层色谱法》2005,18(3):176-180
JPC – Journal of Planar Chromatography – Modern TLC - Extracts of tertiary and quaternary alkaloids from Chelidonium majus L. have been separated by OPLC. Samples of different volumes... 相似文献
962.
An efficient silylating system for 1°, 2°, and 3° alcohols, consisting of a silyl chloride/N-methylimidazole/iodine, was developed. Synthetic and mechanistic aspects of this new reagent system, and particularly the role of iodine were investigated in detail using 1H NMR spectroscopy. 相似文献
963.
Agnieszka Kaflak Dariusz Chmielewski Andrzej Górecki Waclaw Kolodziejski 《Solid state nuclear magnetic resonance》1998,10(4):191-195
Bloch-decay and cross-polarization (CP) 31P nuclear magnetic resonance (NMR) spectra of healthy human trabecular bone were acquired under magic-angle spinning (MAS) at 3 kHz. A single peak at 3.1 ppm was detected. Variable-contact time 1H → 31P CP experiments revealed three signal components growing at various rates. The fast, moderate and slow components were assigned and assessed in P atom % to proton-rich (24%), hydroxyapatite (58%) and proton-deficient (18%) phosphate domains, respectively. Examination of CP kinetics is useful for the chemical characterization of bone tissue. 相似文献
964.
The effects of different operating conditions on ultrafiltration (regenerated cellulose with a cut-off of 100 kg/mol) of cutting oil were studied for two different cases. The factors, examined at three levels, included: pH, oil concentration, feed flow velocity, and temperature. The salt (NaCl and CaCl2) concentration was examined at three levels as well. A lower concentration range was used initially and was increased in the second case. 相似文献
965.
Agnieszka Chylewska Artur Sikorski Aleksandra D?browska Lech Chmurzyński 《Central European Journal of Chemistry》2013,11(1):8-15
The title compound, trans-K2[Co(C2O4)2(H2O)2]·4H2O, was synthesised, and characterised by elemental analysis. Acid dissociation constants for the complex were determined by potentiometric titration and calculated by STOICHIO program. The crystal structure of trans-K2[Co(C2O4)2(H2O)2]·4H2O was determined by X-ray diffraction studies. The asymmetric part of the unit cell contains one symmetric anion of oxalate and water molecule bound with Co(II) ion in crystallographic special position, one potassium cation and two molecules of water. Thermal properties of the complex were examined by thermogravimetric analysis (TGA). A decomposition mechanism is proposed on the basis of the results. 相似文献
966.
Piotr A. Gauden Artur P. Terzyk Sylwester Furmaniak Marek Wiśniewski Piotr Kowalczyk Agnieszka Bielicka Wojciech Zieliński 《Adsorption》2013,19(2-4):785-793
Experimental data of nitrogen adsorption (T = 77.3 K) from gaseous phase measured on commercial closed carbon nanotubes are presented. Additionally, we show the results of N2 adsorption on compressed (using hydraulic press) CNTs. In order to explain the experimental observations the results of GCMC simulations of N2 adsorption on isolated or bundled multi-walled closed nanotubes (four models of bundles) are discussed. We show that the changes of the experimental adsorption isotherms are related to the compression of the investigated adsorbents. They are qualitatively similar to the theoretical observations. Taking into account all results it is concluded that in the “architecture” of nanotubes very important role has been played by isolated nanotubes. 相似文献
967.
Dr. Agnieszka Bartoszewicz Dr. Nanna Ahlsten Prof. Dr. Belén Martín‐Matute 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(23):7274-7302
The preparation of chiral alcohols and amines by using iridium catalysis is reviewed. The methods presented include the reduction of ketones or imines by using hydrogen (hydrogenations), isopropanol, formic acid, or formate (transfer hydrogenations). Also dynamic and oxidative kinetic resolutions leading to chiral alcohols and amines are included. Selected literature reports from early contributions to December 2012 are discussed. 相似文献
968.
Agnieszka Wasilewska Bartosz A. Woźniak Dr. Gabriel Doridot Kamila Piotrowska Natalia Witkowska Dr. Pascal Retailleau Dr. Yvan Six 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11759-11767
The acid‐catalysed thermal rearrangements of a family of N‐aryl 2‐azabicyclo[3.1.0]hexanes is described. These substrates, designed in such a way that the aromatic system is conjugated with an alkene group located at the ortho position relative to the nitrogen atom, have been prepared by using an intramolecular Kulinkovich–de Meijere reaction. The rearrangements can then be conducted either under standard thermal conditions or with microwave activation. Depending on the conditions applied and the substitution pattern, dihydroquinoline or polycyclic aminocyclobutane derivatives can be obtained. A mechanistic discussion is provided, with the proposition of the initial protonation of the aminocyclopropane moiety to give an iminium intermediate. By analogy with related intermolecular reactions, the involvement of electrocyclic reactions among the series of elementary steps that follow is put forward. 相似文献
969.
Agata Siwek Monika Wujec Maria Dobosz Ewa Jagiełło-Wójtowicz Agnieszka Kleinrok Anna Chodkowska 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2669-2677
Three 3-(thiophen-2-yl)-4-substituted-Δ 2 -1,2,4-triazoline-5-thiones were synthesized by intramolecular cyclization of 1-(thiophen-2-ylcarbonyl)-4-substituted thiosemicarbazides in alkaline medium. Their effects on the central nervous system (CNS) of mice in some behavioral tests were investigated. All investigated compounds displayed antinociceptive activity. The correlation between the structural features and bioactivity has been discussed. 相似文献
970.
Aleksandra Michalska Agnieszka Martyna Janina Ziba‐Palus Grzegorz Zadora 《Journal of Raman spectroscopy : JRS》2015,46(9):772-783
Evidential values of Raman spectra recorded for solid and metallic blue car paints were evaluated using visual comparison as well as a statistical approach, i.e. likelihood ratio (LR) test supported by Empirical Cross Entropy (ECE) results. Raman spectra were obtained using a Renishaw inVia spectrometer equipped with a confocal Leica microscope and a near infrared semiconductor laser (785 nm) as an excitation source. When a visual comparison was performed for solid paints, in 17.7% of comparisons (53 pairs out of 300) the samples were indistinguishable, whereas for metallic paints this value was 8.5% of such comparisons (37 pairs out of 435). Comparing the spectra using an LR approach was based on variables being the areas under the most significant Raman spectra bands of pigments present in the analysed samples. Proposed LR models delivered low false positive and false negative rates (for many models lower than 10%), and the ECE plots confirmed that their performance was much better than visual comparison. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献