全文获取类型
收费全文 | 855篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
化学 | 730篇 |
晶体学 | 1篇 |
力学 | 8篇 |
数学 | 65篇 |
物理学 | 79篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 45篇 |
2020年 | 14篇 |
2019年 | 25篇 |
2018年 | 10篇 |
2017年 | 13篇 |
2016年 | 31篇 |
2015年 | 31篇 |
2014年 | 28篇 |
2013年 | 77篇 |
2012年 | 66篇 |
2011年 | 58篇 |
2010年 | 47篇 |
2009年 | 37篇 |
2008年 | 48篇 |
2007年 | 57篇 |
2006年 | 61篇 |
2005年 | 55篇 |
2004年 | 50篇 |
2003年 | 28篇 |
2002年 | 29篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有883条查询结果,搜索用时 15 毫秒
871.
In order to build up tether-supported membranes, we have focused on the synthesis of lipopolymers. Different lipid analog initiators based on 2-bromopropionamide have been synthesized. In addition, fluorescence-labeled lipoinitiators using pyrene were synthesized. These initiators were used for the synthesis of polyacrylamide copolymers by atom-transfer radical polymerization. A final surface-anchor end group was attached to the polymers by polymer analogous reaction. In this way, α,β-functionalized polyacrylamides were obtained. The interaction of these lipopolymers with different lipid bilayer structures was investigated in several experiments. The lipopolymers adsorb onto the surface of vesicles as shown by photon correlation spectroscopy and fluorescence measurements. The fixation of these lipopolymers on flat surfaces was studied using surface plasmon spectroscopy. The film thickness of the adsorbed lipopolymer films is about 12 to 20 Å. The surfaces thus modified can be used for the fixation of lipid vesicles to form polymer-supported bilayers. This leads to an additional thickness increase of 41–62 Å.
872.
Marko kof Jurij Svete Branko Stanovnik Ljubo Goli
Simona Goli
-Grdadolnik Lovro Seli
《Helvetica chimica acta》1998,81(12):2332-2340
(5S)-1-Benzoyl-3-[(E)-cyanomethylidene]-5-(methoxycarbonyl)pyrrolidin-2-one ( 5 ) was prepared in four steps from L -pyroglutamic acid ( 1 ). 1,3-Dipolar cycloadditions of diazomethane ( 6 ) and 2,4,6-trimethoxybenzonitrile oxide ( 7 ) gave substituted 1,2,7-triazaspiro[4.4]non-1-en-6-one 12 and 1-oxa-2,7-diazaspiro[4,4]non-1-en-6-one 13 in 38 and 20% de, respectively. On the other hand, reaction of 5 with N-phenylbenzonitrile imines 8 and 9 , generated in situ from the corresponding hydrazonoyl chlorides 10 and 11 , respectively, and Et3N, furnished racemic pyrrolo[3,4-c]pyrazoles 14 and 15 in 61 and 56% de, respectively. Cycloaddition of nitrile oxide 7 , when performed in the presence of Et3N, led to pyrrolo[3,4-d]isoxazole 16 in 85% de. 相似文献
873.
Reinhard Schwdiauer Johannes Heitz Enno Arenholz Simona BauerGogonea Siegfried Bauer Werner Wirges 《Journal of Polymer Science.Polymer Physics》1999,37(16):2115-2125
Glass‐like and structural first‐order phase transitions are investigated in polytetrafluoroethylene (PTFE) foils and PTFE‐like films prepared by pulsed‐laser deposition (PLD) and plasma polymerization (PP). A structural comparison of the investigated polymers is performed by infrared spectroscopy and dielectric dilatometry. It is shown that dielectric dilatometry (the measurement of the susceptance vs. temperature) provides a simple and elegant means for detecting volumetric transitions in thin nonpolar polymer films. In conventional PTFE foils, the known glass‐like and structural first‐order phase transitions are identified. The structure of pulsed‐laser deposited PTFE strongly depends on the target material, ranging from highly crystalline films showing only structural phase transitions to films strongly deviating from PTFE foils, with structural characteristics comparable to plasma‐polymerized fluorocarbons. The dielectric loss of the highly crystalline PLD films compares favorably with conventional PTFE foils, making the films attractive for new applications in miniature electret devices. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2115–2125, 1999 相似文献
874.
The aim of this paper is to give an overview of the methodological contribution given by Italian researchers in introducing a priori information into multidimensional data analysis techniques, paying special attention to categorical variables. The basic method is Non‐Symmetrical Correspondence Analysis, which enables the analysis of a contingency table when the behaviour of one variable is supposed to be dependent on the other cross‐classified variable. As usual correspondence analysis decomposes an association index (Pearson's Φ2), in a principal component sense, the proposed method is based on a decomposition of a predictability index (Goodman and Kruskal's τb). Non‐symmetrical correspondence analysis has been extended to more than one dependent/explanatory variable(s), by means of proper flattening procedures, i.e. by the use of multiple tables, and the decomposition of Gray and Williams' multiple and partial τb's. In doing so multiple and partial versions have been proposed. A forward selection procedure for choosing the variables with higher predictive power is presented. After a brief review of non‐symmetrical correspondence analysis confirmatory approach, the problem of validating results in terms of analytical stability and replication stability is faced by means of influence functions and resampling techniques. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
875.
Simona Alibrandi Fabiana Nicita Luigi Donato Concetta Scimone Carmela Rinaldi Rosalia DAngelo Antonina Sidoti 《Molecules (Basel, Switzerland)》2021,26(22)
Background: Trimethylaminuria (TMAU) is a rare genetic disease characterized by the accumulation of trimethylamine (TMA) and its subsequent excretion trough main body fluids, determining the characteristic fish odour in affected patients. We realized an experimental study to investigate the role of several coding variants in the causative gene FMO3, that were only considered as polymorphic or benign, even if the available literature on them did not functionally explain their ineffectiveness on the encoded enzyme. Methods: Mutational analysis of 26 TMAU patients was realized by Sanger sequencing. Detected variants were, subsequently, deeply statistically and in silico characterized to determine their possible effects on the enzyme activity. To achieve this goal, a docking prediction for TMA/FMO3 and an unbinding pathway study were performed. Finally, a TMAO/TMA urine quantification by 1H-NMR spectroscopy was performed to support modelling results. Results: The FMO3 screening of all patients highlighted the presence of 17 variants distributed in 26 different haplotypes. Both non-sense and missense considered variants might impair the enzymatic kinetics of FMO3, probably reducing the interaction time between the protein catalytic site and TMA, or losing the wild-type binding site. Conclusions: Even if further functional assays will confirm our predictive results, considering the possible role of FMO3 variants with still uncertain effects, might be a relevant step towards the detection of novel scenarios in TMAU etiopathogenesis. 相似文献
876.
We study the one‐dimensional Vlasov equation in a rod with non‐homogeneous dissipative and conservative boundary conditions. The study is carried out by means of the theory of semigroups and affine operators. Existence, uniqueness and positivity of the solution are proved. The explicit form of the solution is derived and an approximating sequence is given. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
877.
Pellegrino Musto Simona Tavone Gaetano Guerra Claudio De Rosa 《Journal of Polymer Science.Polymer Physics》1997,35(7):1055-1066
Fourier transform infrared (FTIR) spectra of syndiotactic polystyrene (s-PS) semicrystalline samples have been examined by using the spectral subtraction approach. For the crystalline forms including trans-planar chains (trigonal α and orthorhombic β) a number of conformational and structural order effects, not previously described in the literature, have been identified. A method based on the results of the spectral subtraction analysis has been developed for the determination of the crystallinity degree and compared with the standard method based on the wide-angle X-ray diffraction patterns. The spectral subtraction analysis on FTIR spectra allows also an easy evaluation of the amount of α and β crystalline phases (often simultaneously present in melt-crystallized samples) although both contain chains in a same conformation. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1055–1066, 1997 相似文献
878.
Stuti Bhagat Simona Tyagi Sanjay Singh 《Particle & Particle Systems Characterization》2023,40(11):2300079
The therapeutic success of nanomedicines requires nanomaterials to either adhere to the surface or internalize within the cytoplasm. The endocytosis phenomenon is controlled by the nanomaterial's shape, size, composition, charge, and capping molecules. The membrane potential-based non-specific internalization of therapeutic nanomedicines offers limited benefits than receptor-based specific delivery. Glut receptor-based internalization of glucose molecules is a well-known process in cancerous cells, which is one of the most exploited strategies to target cancer cells using nanoparticles. However, the internalization process of other structurally similar monosaccharides (D-Galactose, Mannose, and D-Fructose) conjugated nanoparticles remains to be unexplored. Herein, D-Glucose, D-Galactose, Mannose, and D-Fructose-coated AuNPs and AgNPs have been synthesized and studied the role of Glut receptors in their internalization in liver cancer cells, and compared them with non-cancerous cells. Results revealed that almost all monosaccharide-coated NPs exhibited high uptake in liver cancer cells than non-cancerous cells. Glut-1 receptor is observed to play a key role in the uptake and inhibition of Glut-1 receptors by genistein lead to a significant decrease in nanoparticle uptake. In conclusion, monosaccharide-conjugated nanoparticles can be used to direct the selective internalization of AuNPs and AgNPs in hepatic cancer cells to realize therapeutic and imaging applications. 相似文献
879.
Esther Amevor Simona Bronco Giambattista Consiglio Silvia Di Benedetto 《Macromolecular Symposia》1995,89(1):443-454
Strictly alternating copolymers between olefins and carbon monoxide are synthesized using cationic palladium catalysts modified by phosphorus or nitrogen ligands. Basic chelate diphosphines as the ligand allow the regioregular copolymerization of aliphatic olefins thus affording, e.g. in the case of propene, poly(1-oxo-2-methyltrimethylene). Steric control of the copolymerization process towards the production of overwhelmingly isotactic copolymers is possible particularly when using atropisomeric ligands. In the case of styrene as the substrate and for all ligands employed the copolymerization process is regioregular. Prevailing syndiotactic structure is obtained with 1,10-phenanthroline or 2,2′-bipyridine as the ligand. Chelate thioether ligands allow the preparation of a completely atactic material. For 4-tert-butylstyrene an isotactic structure became accessible by using chiral bisoxazolidines. The prevailing structure of the copolymers of cyclopentene corresponds to a 1,3-enchainment of the olefin units most probably associated with a prevailing diisotactic structure 相似文献
880.