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131.
Dr. Xiaoyan Shi Felix León Ying Sim Shina Quek Gavin Hum Yi Xin Joycelyn Khoo Zi Xuan Ng Mian Yang Par How Chee Ong Varun K. Singh Dr. Rakesh Ganguly Assoc. Prof. Jack K. Clegg Dr. Jesús Díaz Felipe García 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22284-22292
We have synthesized a completely new family of acyclic trimeric cyclodiphosphazane compounds comprising NH, NiPr, NtBu and NPh bridging groups. In addition, the first NH-bridged acyclic dimeric cyclophosphazane has been produced. The trimeric species display highly tuneable characteristics so that the distance between the terminal N(H)R moieties can be readily modulated by the steric bulk present in the bridging groups (ranging from ≈6 to ≈10 Å). Moreover, these species exhibit pronounced topological changes when a weak non-bonding NH⋅⋅⋅π aryl interaction is introduced. Finally, the NH-bridged chloride binding affinities have been calculated and benchmarked along with the existing experimental data available for monomeric cyclodiphosphazanes. Our results underscore these species as promising hydrogen bond donors for supramolecular host–guest applications. 相似文献
132.
The laminar burning velocity is a fundamental property that is extensively used in the study and modelling of premixed combustion processes. A counterflow flame configuration is commonly used to measure this quantity for different combustion systems. In this procedure, the burning velocities are typically measured at various low stretch conditions and the unstretched burning velocity is extrapolated from these measurements. This extrapolation is done assuming a theoretically one-dimensional system along the centre-line. We analyse the validity of this assumption by performing DNS studies with finite rate chemistry of the experimental counterflow configuration. The extrapolation process using one-dimensional computations is performed on the DNS data and the extrapolated value is compared to the computed laminar burning velocity for the chemical mechanism used. We show that the assumption works well if the nozzle exit velocity has a nearly top-hat profile. For non-uniform velocity profiles, it is shown that the temperature curvature at the centre-line becomes important. This effect cannot be captured by the one-dimensional formulation. Thus, experimental studies measuring laminar burning velocity need to ensure that the nozzle velocity profile is very close to uniform. The extrapolation to zero stretch using 1D counterflow simulations can be performed in different ways. Based on the results obtained in this paper, a simple and accurate extrapolation method is proposed. 相似文献
133.
Sandip Rooj Varun Thakur Uwe Gohs Udo Wagenknecht Anil K. Bhowmick Gert Heinrich 《先进技术聚合物》2011,22(12):2257-2263
Blends of polypropylene (PP) and epoxidized natural rubber (ENR) were prepared by an in‐line electron induced reactive processing technique. The mixing was done in a Brabender mixing chamber coupled with an electron accelerator. The effect of sequence of electron treatment on the compatibilization of non‐polar PP and polar ENR was investigated in the presence of triallyl cyanurate (TAC). Finally, the resulting blends were characterized by different techniques, namely, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), tensile tests, and rheological studies. Generation of phase coupling and chemical compatibilization were observed from FTIR analysis. DMA studies showed enhanced high‐temperature modulus (above the glass transition temperature of both components) followed up by lowering in the tan δ peak. Rheological studies showed increase in modulus at low frequencies. Electron treatment and incorporation of rubber phase into PP showed significant effect on the degree of crystallinity of the blends, which was characterized by DSC study. The results obtained from FTIR, DMA, SEM, rheological studies, and tensile tests strongly affirmed that electron induced reactive processing of PP in presence of TAC before adding of ENR performed the best amongst all samples modified with electrons investigated in this study. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
134.
Peshkov VA Pereshivko OP Sharma S Meganathan T Parmar VS Ermolat'ev DS Van der Eycken EV 《The Journal of organic chemistry》2011,76(14):5867-5872
A one-pot protocol based on a Ag(I)-catalyzed cycloisomerization of propargylic ureas, derived from secondary propargylamines and isocyanates, was developed for the generation of the 2-imidazolone core. 相似文献
135.
Dr. Vandana Bhalla Varun Vij Abhimanew Dhir Dr. Manoj Kumar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(12):3765-3772
New hetero‐oligophenylene derivative ( 2 ) was synthesized which exhibits aggregation‐induced emission enhancement (AIEE) in H2O/THF (80:20). The aggregates serve as a biological probe for three different proteins, that is bovine serum albumin (BSA), cytochrome c, and lysozyme, and DNA in contrasting modes. Further, among 29 metal ions tested, the contrasting fluorescence behavior of aggregates of 2 is observed with only Pb2+ and Pd2+ ions. Multiple output logic circuits based upon the fluorescence behavior between BSA and cytochrome c and between Pb2+ and Pd2+ ions are constructed. 相似文献
136.
Phosphoenolpyruvate (PEP)-dependent kinases are central to numerous metabolic processes and mediate the production of adenosine triphosphate (ATP) by substrate-level phosphorylation (SLP). While pyruvate kinase (PK, EC: 2.7.1.40), the final enzyme of the glycolytic pathway is critical in the anaerobic synthesis of ATP from ADP, pyruvate phosphate dikinase (PPDK, EC: 2.7.9.1), and phosphoenolpyruvate synthase (PEPS, EC: 2.7.9.2) help generate ATP from AMP coupled to PEP as a substrate. Here we demonstrate an inexpensive and effective electrophoretic technology to determine the activities of these enzymes by blue-native polyacrylamide gel electrophoresis (BN-PAGE). The generation of pyruvate is linked to exogenous lactate dehydrogenase (LDH), and the oxidation of reduced nicotinamide adenine dinucleotide (NADH) coupled to 2,6-dichloroindophenol (DCIP) and iodonitrotetrazolium chloride (INT) results in a formazan precipitate which is easily quantifiable. The selectivity of the enzymes is ensured by including either AMP or ADP and pyrophosphate (PP(i) ) or inorganic phosphate (P(i) ). Activity bands were readily obtained after incubation in the respective reaction mixtures for 20-30 min. Cell-free extract concentrations as low as 20 μg protein equivalent yielded activity bands and substrate levels were manipulated to optimize sensitivity of this analytical technique. High-pressure liquid chromatography (HPLC), two-dimensional (2-D) SDS-PAGE (where SDS is sodium dodecyl sulfate), and immunoblot studies of the excised activity band help further characterize these PEP-dependent kinases. Furthermore, these enzymes were readily identified on the same gel by incubating it sequentially in the respective reaction mixtures. This technique provides a facile method to elucidate these kinases in biological systems. 相似文献
137.
Prof. Dr. Mohan Patel Deepen S. Gandhi Pradhuman A. Parmar Bhupesh S. Bhatt Anshul P. Patidar 《无机化学与普通化学杂志》2012,638(5):838-843
The complexes [Pt(3′′‐clpbpy)Cl2] ( 1 ) [3′′‐clpbpy = 4‐(3′′‐chlorophenyl)‐6‐phenyl‐2, 2′‐bipyridine], [Pt(4′′‐clpbpy)Cl2] ( 2 ) [4′′‐clpbpy = 4‐(4′′‐chlorophenyl)‐6‐phenyl‐2, 2′‐bipyridine], [Pt(3′′‐brpbpy)Cl2] ( 3 ) [3′′‐brpbpy = 4‐(3′′‐bromophenyl)‐6‐phenyl‐2, 2′‐bipyridine], and [Pt(4′′‐brpbpy)Cl2] ( 4 ) [4′′‐brpbpy = 4‐(4′′‐bromophenyl)‐6‐phenyl‐2, 2′‐bipyridine] were synthesized and characterized. The binding of the complexes with herring sperm DNA (HS DNA) was investigated by absorption titration and viscosity measurements. It was found that the complexes have ability of interaction with DNA by covalent mode. The intrinsic binding constant Kb of the complexes with HS DNA is 8.76 × 104 ( 1 ), 9.89 ×104 ( 2 ), 1.52 × 105 ( 3 ), and 2.31 × 105 ( 4 ) M–1. The slight depression in relative specific viscosity was observed, which also attributes to covalent binding of complexes with DNA bases. Gel electrophoresis assay demonstrated the ability of the complexes to unwind negatively supercoiled pUC19 plasmid by 14° ( 1 ), 13° ( 2 ), 13° ( 3 ), and 11° ( 4 ). The in vitro cytotoxic property of the synthesized metal complexes was also carried out against brine shrimp bioassay. 相似文献
138.
The copper complex [Cu((t)BuPhimp)(Cl)] (1) derived from tridentate ligand (t)BuPhimpH having N(2)O donors was synthesized, and its molecular structure was determined. A phenoxyl radical complex was generated in solution at room temperature using Ce(IV). The nuclease and anticancer activities of 1 were investigated. The roles of the tert-butyl group and singlet oxygen in the DNA cleavage activity were also discussed. 相似文献
139.
Bansal S Ponnan P Raj HG Weintraub ST Chopra M Kumari R Saluja D Kumar A Tyagi TK Singh P Prasad AK Saso L Rastogi RC Parmar VS 《Applied biochemistry and biotechnology》2009,157(2):285-298
Our earlier reports documented that calreticulin, a multifunctional Ca2+-binding protein in endoplasmic reticulum lumen, possessed protein acetyltransferase function termed Calreticulin Transacetylase
(CRTAase). The autoacetylation of purified human placental CRTAase concomitant with the acetylation of receptor proteins by
a model acetoxycoumarin, 7,8-Diacetoxy-4-methylcoumarin, was observed. Here, we have examined the autoacetylation property
of CRTAase by immunoblotting and mass spectrometry. Ca2+ was found to inhibit CRTAase activity. The inhibition of both autoacetylation of CRTAase as well as acetylation of the receptor
protein was apparent when Ca2+ was included in the reaction mixture as visualized by interaction with anti-acetyl lysine antibody. The acetylation of lysines
residues: −48, −62, −64, −153, and −159 in N-domain and −206, −207, −209, and −238 in P-domain of CRTAase were located by
high-performance liquid chromatography-electronspray ionization tandem mass spectrometry. Further, computer assisted protein
structure modeling studies were undertaken to probe the effect of autoacetylation of CRTAase. Accordingly, the predicted CRTAase
3D model showed that all the loop regions of both N- and P-domain bear the acetylated lysines. Energy minimization of the
acetylated residues revealed charge neutralization of lysines due to the N-ε-acetylation which may facilitate the interaction
of CRTAase with the protein substrate and the subsequent transacetylase action.
An erratum to this article can be found at 相似文献
140.
Komal R. Parmar Kalpesh A. Patel Sunny R. Shah Navin R. Sheth 《Journal of inclusion phenomena and macrocyclic chemistry》2009,65(3-4):263-268
Lamotrigine (LMN) is an antiepileptic drug, with poor aqueous solubility, which might lead to erratic bioavailability. The objective of the present work was to improve the dissolution characteristics of the LMN using Hydroxy propyl β-cyclodextrin (HP β-CD), which might offer reliable bioavailability. The phase solubility profile was classified as A L -type, revealing 1:1 stoichiometric complexation, with a stability constant (Ks) of 573 M?1. Binary systems of LMN and HP β-CD were prepared in different molar ratios (1:1, 1:2, 1:3 and 1:4) by kneading method. The binary systems were characterized by Fourier Transform Infrared (FT-IR) Spectroscopy, Differential Scanning Calorimetry (DSC) and Powder X-ray Diffraction Analysis (PXRD). Results revealed that in the kneaded products the entire drug was entrapped inside the HP β-CD cavity and reduction in drug crystallinity also took place, which may be responsible for improved dissolution characteristics as compared to that of the pure drug as depicted from the dissolution studies. 相似文献