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排序方式: 共有508条查询结果,搜索用时 15 毫秒
111.
Liu Z Ma N Jia Y Bois-Choussy M Malabarba A Zhu J 《The Journal of organic chemistry》2005,70(7):2847-2850
[reaction: see text] Synthesis of enantiomerically pure beta-amino-alpha-hydroxy esters (1, 2) and beta-amino-alpha-azido ester (3) using Sharpless AA as a key step is described. A hitherto unreported side reaction, the oxidation of the beta-hydroxy-alpha-amino ester (5) into the alpha,alpha-di-tert-butyloxycarbamoyl-beta-ketoester (8) under AA conditions, is documented. 相似文献
112.
Elisabete A. De Nadai Fernandes Fábio S. Tagliaferro Adriano Azevedo-Filho Peter Bode 《Accreditation and quality assurance》2002,7(10):378-387
Samples of green coffee (Coffea arabica) produced in the crop year 1999/2000 in Minas Gerais state, Brazil, were analyzed for the elements Al, Ba, Br, Ca, Cl, Co,
Cs, Cu, Fe, K, Mg, Mn, Na, Rb, S, Sc, and Zn using instrumental neutron activation analysis (INAA), in an attempt to establish
fingerprints of organically grown coffee. Using data mining/KDD techniques the elements Br, Ca, Cs, Co, Mn, and Rb were found
to be suited as markers for discrimination of organic from conventional coffees.
Received: 12 April 2002 Accepted: 31 July 2002
Acknowledgments The authors wish to thank the financial support supplied by FAPESP and CNPq; and TUDelft for granting a research fellowship
to Mr. Tagliaferro. Thanks are also given to MINASCOFFEE for supplying the coffee samples, and to an anonymous referee for
valuable comments. 相似文献
113.
Plasma viral load (VL) values and CD4(+) cell count are employed clinically for initiation of therapy in the treatment of patients infected with human immunodeficiency virus (HIV), as previous clinical studies have shown a marked prevalence of acquired immunodeficiency syndrome (AIDS) development in seropositive individuals with VL values over 30 000 copies/mL. Many studies have shown that reduced glutathione (GSH) and cysteine (Cys) deficiency play an important role in the infection. We have developed capillary zone electrophoresis (CZE)-based assays and have used them to investigate the relationship between plasma and intracellular thiol levels and HIV-1 viremia in plasma. Blood samples from healthy volunteers and seropositive patients undergoing different antiretroviral regimes were analyzed in the study. The VL assay was based on CZE-UV detection of viral RNA at 260 nm. Determination of endogenous reduced Cys and GSH was achieved by CZE-UV detection of their mercurial complexes at 200 nm. We found that a decrease in GSH and Cys levels may be associated with disease progress. In fact, reduced GSH and Cys levels appear progressively reduced with increasing VL. 相似文献
114.
Readily available methyl hydrogen (R)-3-methylglutarate(2) is a useful chiral building block for the synthesis of several biologically active compounds. Enantiomerically pure (R)-2 has been employed to synthesize stereospecifically each of the two enantiomers, 1a and 1b, of 10-methyl-2-tridecanone, the sex pheromone of the southern corn rootworm, Diabrotica undecimpunctata howardi Barber. Compound (R)-2 has been also used to prepare 99% optically pure (R)-3-methyl-1-pentanol (6) and enantiomerically pure (R)-5-methyl-i-tricosyne (7). These compounds are useful building blocks suitable for the further elaboration to other chiral insect pheromones. 相似文献
115.
Sabrina M. Nobre Mauro N. Muniz Marcus Seferin Wagner M. da Silva Adriano L. Monteiro 《应用有机金属化学》2011,25(4):289-293
We have developed a sequential and selective Pd‐catalyzed double‐Heck arylation of ethylene that results in non‐symmetrical nitro‐stilbene analogs of trans‐resveratrol at excellent yields. A catalytic system consisting of Pd(OAc)2 and P(o‐tolyl)3 permitted us to carry out the two consecutive Heck arylations without losing activity from the first to the second Heck reaction. After the first Heck arylation of ethylene, no isolation or additional catalyst loading is required for the second Heck arylation reaction. This protocol was applied to the synthesis of methylated trans‐resveratrol, which was obtained at a 65% overall yield. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
116.
117.
Adriano Mollica Federica Feliciani Ivana Cacciatore Gino Lucente 《Tetrahedron letters》2010,51(9):1333-1335
In this Letter we present a simple reaction pathway which allows the conversion of the glutamic acid residue of a tripeptide into a proline residue. The reaction was performed by using Boc-Val-Glu-Phe-NH2 as a starting material and is based on a NaH-induced intraresidue alkylation under reaction conditions analogous to that adopted during the Freidinger lactams formation. 相似文献
118.
119.
Bruno Fonsêca Feitosa Charlene Maria de Alcntara Amanda Beatriz Sales de Lima Adriano SantAna Silva Alfredina dos Santos Araújo Mnica Tejo Cavalcanti Edna Mori Isaac Moura Araújo Pablo Antonio Maia de Farias Polrat Wilairatana Henrique Douglas Melo Coutinho 《Molecules (Basel, Switzerland)》2022,27(18)
The inappropriate use of synthetic antibiotics has become a global public health problem. Therefore, the study of new alternatives for the treatment of infectious diseases is relevant and natural bioactive products are on the rise. This study conducted a scientific prospection of bioactive natural products with promising applications in the chemical control of microorganisms. A systematic review of the most recent articles was performed according to the following three steps: (i) eligibility assessment, (ii) screening, and (iii) inclusion of articles and information extraction. There has been an increase in the number of scientific publications on bioactive natural products for microbial control in the CAPES and SciELO databases (2001–2021). Seventeen relevant articles were included, most of which focused on extracts. Ascorbic acid, chlorogenic acid, chrysin, and quercetin were the most cited compounds. Natural products were shown to be effective in inhibiting more than 30 microorganisms. A discussion was presented on the research trends. 相似文献
120.
Victor S. Batista Adriano Marques Gonalves Nailton M. Nascimento-Júnior 《Molecules (Basel, Switzerland)》2022,27(23)
The neuronal nicotinic acetylcholine receptors (nAChRs) belong to the ligand-gated ion channel (GLIC) group, presenting a crucial role in several biological processes and neuronal disorders. The α4β2 and α7 nAChRs are the most abundant in the central nervous system (CNS), being involved in challenging diseases such as epilepsy, Alzheimer’s disease, schizophrenia, and anxiety disorder, as well as alcohol and nicotine dependencies. In addition, in silico-based strategies may contribute to revealing new insights into drug design and virtual screening to find new drug candidates to treat CNS disorders. In this context, the pharmacophore maps were constructed and validated for the orthosteric sites of α4β2 and α7 nAChRs, through a docking-based Comparative Intermolecular Contacts Analysis (dbCICA). In this sense, bioactive ligands were retrieved from the literature for each receptor. A molecular docking protocol was developed for all ligands in both receptors by using GOLD software, considering GoldScore, ChemScore, ASP, and ChemPLP scoring functions. Output GOLD results were post-processed through dbCICA to identify critical contacts involved in protein-ligand interactions. Moreover, Crossminer software was used to construct a pharmacophoric map based on the most well-behaved ligands and negative contacts from the dbCICA model for each receptor. Both pharmacophore maps were validated by using a ROC curve. The results revealed important features for the ligands, such as the presence of hydrophobic regions, a planar ring, and hydrogen bond donor and acceptor atoms for α4β2. Parallelly, a non-planar ring region was identified for α7. These results can enable fragment-based drug design (FBDD) strategies, such as fragment growing, linking, and merging, allowing an increase in the activity of known fragments. Thus, our results can contribute to a further understanding of structural subunits presenting the potential for key ligand-receptor interactions, favoring the search in molecular databases and the design of novel ligands. 相似文献