全文获取类型
收费全文 | 829篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
化学 | 560篇 |
晶体学 | 5篇 |
力学 | 27篇 |
数学 | 105篇 |
物理学 | 152篇 |
出版年
2021年 | 6篇 |
2019年 | 5篇 |
2016年 | 17篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 41篇 |
2012年 | 42篇 |
2011年 | 54篇 |
2010年 | 30篇 |
2009年 | 32篇 |
2008年 | 33篇 |
2007年 | 31篇 |
2006年 | 39篇 |
2005年 | 25篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 19篇 |
2001年 | 14篇 |
2000年 | 17篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1996年 | 14篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1989年 | 6篇 |
1985年 | 6篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1972年 | 9篇 |
1970年 | 5篇 |
1969年 | 7篇 |
1968年 | 7篇 |
1966年 | 11篇 |
1931年 | 5篇 |
1930年 | 6篇 |
1929年 | 8篇 |
1928年 | 14篇 |
1927年 | 11篇 |
1925年 | 5篇 |
1893年 | 6篇 |
1890年 | 4篇 |
1888年 | 5篇 |
1887年 | 4篇 |
1884年 | 5篇 |
1883年 | 8篇 |
1882年 | 4篇 |
排序方式: 共有849条查询结果,搜索用时 15 毫秒
151.
152.
153.
Vijayanand Chandrasekaran Eugen Johannes Hauke Kobarg Frank D S?nnichsen Thisbe K Lindhorst 《ChemistryOpen》2014,3(3):99-108
Spatial orientation of carbohydrates is a meaningful parameter in carbohydrate recognition processes. To vary orientation of sugars with temporal and spatial resolution, photosensitive glycoconjugates with favorable photochromic properties appear to be opportune. Here, a series of azobenzene glycosides were synthesized, employing glycoside synthesis and Mills reaction, to allow “switching” of carbohydrate orientation by reversible E/Z isomerization of the azobenzene N=N double bond. Their photochromic properties were tested and effects of azobenzene substitution as well as the effect of anomeric configuration and the orientation of the sugars 2-hydroxy group were evaluated. 相似文献
154.
George Jîtc Erzsbet Fogarasi Bianca-Eugenia sz Camil Eugen Vari Amelia Tero-Vescan Amalia Miklos Mdlina-Georgiana Btrînu Carmen Maria Rusz Mircea Dumitru Croitoru Maria Titica Dogaru 《Molecules (Basel, Switzerland)》2021,26(16)
In the present study, a HPLC/DAD method was set up to allow for the determination and quantification of malondialdehyde (MDA) in the brain of rodents (rats). Chromatographic separation was achieved on Supelcosil LC-18 (3 μm) SUPELCO Column 3.3 cm × 4.6 mm and Supelco Column Saver 0.5 μm filter by using a mobile phase acetonitrile (A) and phosphate buffer (20 mM, pH = 6) (B). Isocratic elution was 14% for (A) and 86% for (B). The injection volume (loop mode) was 100 μL with an analysis time of 1.5 min. Flow rate was set at 1 mL/min. The eluted compound was detected at 532 nm by a DAD detector by keeping the column oven at room temperature. The results indicated that the method has good linearity in the range of 0.2–20 μg/g. Both intra- and inter-day precision, expressed as RSD, were ≤15% and the accuracies ranged between ±15%. The lower limit of quantification (LLOQ), stability, and robustness were evaluated and satisfied the validation criteria. The method was successfully applied in a study of chronic toxicology following different treatment regimens with haloperidol and metformin. 相似文献
155.
156.
Eugen M. Aschenbrenner Clemens K. Weiss Dr. Katharina Landfester Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(10):2434-2444
Just a drop of water : Esterification in water is possible by confining the reactants in small miniemulsion droplets protected by nonionic surfactants. A lipase located at the interface between the droplet and aqueous surroundings catalyzes the esterification and expels generated water from the reaction site (see picture). High yields of the ester can be obtained after short reaction times under ambient conditions.
157.
Constanze Hägele Dr. Eugen Wuckert Sabine Laschat Prof. Dr. Frank Giesselmann Prof. Dr. 《Chemphyschem》2009,10(8):1291-1298
Rather uncommon but pronounced odd–even effects in the clearing temperatures of liquid crystals are found for three new homologous series of discotic tetraphenylenes (see figure). Detailed similarities to the well‐known odd‐even effects in calmitic mesogens point towards a more general understanding of odd‐even effects in liquid crystals.
158.
Corina Flangea Catalin Schiopu Eugen Sisu Alina Serb Michael Przybylski Daniela G. Seidler Alina D. Zamfir 《Analytical and bioanalytical chemistry》2009,395(8):2489-2498
Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans display variability of sulfation in their constituent
disaccharide repeats during chain elongation. Since a large proportion of the extracellular matrix of the central nervous
system (CNS) is composed of proteoglycans, CS/DS disaccharide degree and profile of sulfation play important roles in the
functional diversity of neurons, brain development, and some of its pathological states. To investigate the sulfation pattern
of CS/DS structures expressed in CNS, we introduced here a novel method based on an advanced system encompassing fully automated
chip nanoelectrospray ionization (nanoESI) in the negative ion mode and high capacity ion trap multistage mass spectrometry
(MS2–MS3) by collision-induced dissociation (CID). This method, introduced here for the first time in glycomics of brain glycosaminoglycans,
was particularly applied to structural investigation of disaccharides obtained by β-elimination and digestion with chondroitin
B and AC I lyase of hybrid CS/DS chains from wild-type mouse brain. Screening in the chip-MS mode of DS disaccharide fraction
resulting after depolymerization with chondroitin B lyase revealed molecular ions assigned to monosulfated disaccharide species
having a composition of 4,5-Δ-[IdoA-GalNAc]. By optimized CID MS2–MS3, fragment ions supporting the localization of sulfate ester group at C4 within GalNAc were produced. Chip ESI MS profiling
of CS disaccharide fraction obtained by depolymerization of the same CS/DS chain using chondroitin AC I lyase indicated the
occurrence of mono- and bisulfated 4,5-Δ-[GlcA-GalNAc]. The site of oversulfation was determined by MS2–MS3, which provided sequence patterns consistent with a rare GlcA-3-sulfate–GalNAc-6-sulfate structural motif.
相似文献
159.
Sisu E Bosker WT Norde W Slaghek TM Timmermans JW Peter-Katalinić J Cohen-Stuart MA Zamfir AD 《Rapid communications in mass spectrometry : RCM》2006,20(2):209-218
A combined methodology for obtaining at the preparative scale and characterization by nanoelectrospray ionization (nanoESI) quadrupole time-of-flight (QTOF) mass spectrometry (MS) and tandem MS (MS/MS) of linear polysaccharides modified at the reducing end is presented. Two polydisperse maltodextrins (1000 and 3000 Da) and a high molecular weight polydisperse dextran (6000 Da) were coupled with hexamethylenediamine (HMD). The coupling products were analyzed by nanoESI-QTOF-MS in the positive ion mode and MS/MS using collision-induced dissociation (CID) at low energies. In the HMD-M1000 mixture, the polysaccharide chains containing from 2 to 8 Glc residues were detected, while in HMD-M3000 we identified a complete series of chains containing from 8 to 21 Glc moieties. The employed ESI conditions enhanced the detection of chains with up to 46 Glc residues in the HMD-D6000 sample. By optimized MS/MS, HMD-modified polysaccharides of 3, 4, 5, 12 and 46 degrees of polymerization yielded product ion spectra exhibiting the whole set of Y- and B-fragment ions. The MS structural data were obtained within a few minutes of signal acquisition, with a sample consumption situating the analysis sensitivity in the picomolar range. 相似文献
160.
Vera Balan Ivona Andreea Petrache Marcel Ionel Popa Maria Butnaru Eugen Barbu John Tsibouklis Liliana Verestiuc 《Journal of nanoparticle research》2012,14(2):730
Haemocompatible biotinylated superparamagnetic nanoparticles (size range 300–700 nm) have been obtained by coating magnetite
through ionic gelation with a mixture of chitosan and sodium tripolyphosphate, followed by subsequent functionalisation with
biotin. The evaluations of their magnetic properties together with haemocompatibility tests have shown that these nanoparticles
exhibit the prerequisite behaviour for use in magnetic field–assisted separations within biological systems. 相似文献