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281.
Ravindra K. Bisht 《Indagationes Mathematicae》2018,29(2):819-823
In this paper, we give a counterexample to Lemma 2.2 proved by Song-il Ri (2016). Further, we improve the result of Song-il Ri by employing a proper setting. 相似文献
282.
Sagar P. Pathare Ravindra V. Sawant Krishnacharya G. Akamanchi 《Tetrahedron letters》2012,53(26):3259-3263
Sulfated tungstate catalyzed, green, rapid, and practical method for N-formylation of amines using formic acid under solvent-free conditions is described. This method showed improvements over the reported in terms of yield, reaction time, and chemoselectivity. 相似文献
283.
Chate Asha V. Dongre Ravindra M. Khaire Mahadeo K. Bondle Giribala M. Sangshetti Jaiprakash N. Damale Manoj 《Research on Chemical Intermediates》2018,44(10):6119-6136
Research on Chemical Intermediates - Simple and green synthetic procedures constitute an important goal in organic synthesis. The combination of multicomponent reactions (MCRs) and unconventional... 相似文献
284.
Sandip Gurav Anitha Police Mohd Zainuddin Ravindra Ramachandra Punde Purushottam Dewang Chandregowda V Raghava Reddy Kethiri Sriram Rajagopal Ramesh Mullangi 《Biomedical chromatography : BMC》2013,27(2):164-171
A highly sensitive, specific and enantioselective assay has been developed and validated for the estimation of TAK‐700 enantiomers [(+)‐TAK‐700 and (?)‐TAK‐700] in rat plasma on LC‐MS/MS‐ESI in the positive‐ion mode. Liquid–liquid extraction was used to extract (±)‐TAK‐700 enantiomers and IS (phenacetin) from rat plasma. TAK‐700 enantiomers were separated using methanol and 5 mm ammonium acetate (80:20, v/v) at a flow rate of 0.7 mL/min on a Chiralcel OJ‐RH column. The total run time was 7.0 min and the elution of (+)‐TAK‐700, (?)‐TAK‐700 and IS occurred at 3.71, 4.45 and 4.33 min, respectively. The MS/MS ion transitions monitored were m/z 308.2 → 95.0 for TAK‐700 and m/z 180.2 → 110.1 for IS. The standard curves for TAK‐700 enantiomers were linear (r2 > 0.998) in the concentration range 2.01–2015 ng/mL for each enantiomer. The inter‐ and intra‐day precisions were in the ranges 3.74–7.61 and 2.06–8.71% and 3.59–9.00 and 2.32–11.0% for (+)‐TAK‐700 and (?)‐TAK‐700, respectively. Both the enantiomers were found to be stable in a battery of stability studies. This novel method was applied to the study of stereoselective oral pharmacokinetics of (+)‐TAK‐700 and it was unequivocally demonstrated that (+)‐TAK‐700 does not undergo chiral inversion to its antipode in vivo. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
285.
Biswanath Das Cheruku Ravindra ReddySiddavatam Nagendra Maram Lingaiah 《Tetrahedron letters》2011,52(27):3496-3498
Cyclic sulfamidates (prepared from α-amino acids and β-amino alcohols) have been used for the first time for the synthesis of novel β-amino phosphonates (chiral and achiral) by treatment with dialkyl phosphites using sodium hydride. 2-Substituted and 1,2-disubtituted β-amino phosphonates have efficiently been prepared following this method. The products are formed in high yield (79-84%) within 8-12 h. 相似文献
286.
Suresh PS Punde RR Gupta M Dixit A Giri S Rajagopal S Mullangi R 《Biomedical chromatography : BMC》2011,25(8):930-937
A highly sensitive and rapid assay method has been developed and validated for the estimation of S‐(−)‐raclopride (S‐RCP) in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive ion mode. The assay procedure involves a simple liquid–liquid extraction technique for extraction of S‐RCP and phenacetin (internal standard, IS) from rat plasma. Chromatographic separation was achieved with 0.2% formic acid : acetonitrile (80:20, v/v) at a flow rate of 0.30 mL/min on a Phenomenex Prodigy C18 column with a total run time of 4.5 min. The MS/MS ion transitions monitored were 347.2 → 112.1 for S‐RCP and 180.1 → 110.1 for IS. Method validation and pre‐clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.05 ng/mL and the linearity range was extended from 0.05 to 152 ng/mL in rat plasma. The intra‐day and inter‐day precisions were 0.23–10.5 and 3.74–7.29%, respectively. This novel method was applied to a pharmacokinetic study of S‐RCP in rats. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
287.
Sivanandam VN Jayaraman M Hoop CL Kodali R Wetzel R van der Wel PC 《Journal of the American Chemical Society》2011,133(12):4558-4566
The 17-residue N-terminus (htt(NT)) directly flanking the polyQ sequence in huntingtin (htt) N-terminal fragments plays a crucial role in initiating and accelerating the aggregation process that is associated with Huntington's disease pathogenesis. Here we report on magic-angle-spinning solid-state NMR studies of the amyloid-like aggregates of an htt N-terminal fragment. We find that the polyQ portion of this peptide exists in a rigid, dehydrated amyloid core that is structurally similar to simpler polyQ fibrils and may contain antiparallel β-sheets. In contrast, the htt(NT) sequence in the aggregates is composed in part of a well-defined helix, which likely also exists in early oligomeric aggregates. Further NMR experiments demonstrate that the N-terminal helical segment displays increased dynamics and water exposure. Given its specific contribution to the initiation, rate, and mechanism of fibril formation, the helical nature of htt(NT) and its apparent lack of effect on the polyQ fibril core structure seem surprising. The results provide new details about these disease-associated aggregates and also provide a clear example of an amino acid sequence that greatly enhances the rate of amyloid formation while itself not taking part in the amyloid structure. There is an interesting mechanistic analogy to recent reports pointing out the early-stage contributions of transient intermolecular helix-helix interactions in the aggregation behavior of various other amyloid fibrils. 相似文献
288.
Tracy EC Bowman MJ Pandey RK Henderson BW Baumann H 《Photochemistry and photobiology》2011,87(6):1405-1418
The ATP-dependent transporter ABCG2 exports certain photosensitizers (PS) from cells, implying that the enhanced expression of ABCG2 by cancer cells may confer resistance to photodynamic therapy (PDT) mediated by those PS. In 35 patient-derived primary cultures of lung epithelial and stromal cells, PS with different subcellular localization and affinity for ABCG2 displayed cell-type specific retention both independent and dependent on ABCG2. In the majority of cases, the ABCG2 substrate 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) was lost from fibroblastic cells more rapidly than from their epithelial counterparts, even in the absence of detectable ABCG2 expression, facilitating selective eradication by PDT of epithelial over fibroblastic cells in tumor/stroma co-cultures. Pairwise comparison of normal and transformed epithelial cells also identified tumor cells with elevated or reduced retention of HPPH, depending on ABCG2. Enhanced ABCG2 expression led to the selective PDT survival of tumor cells in tumor/stroma co-cultures. This survival pattern was reversible through HPPH derivatives that are not ABCG2 substrates or the ABCG2 inhibitor imatinib mesylate. PS retention, not differences in subcellular distribution or cell signaling responses, was determining cell type selective death by PDT. These data suggest that up-front knowledge of tumor characteristics, specifically ABCG2 status, could be helpful in individualized PDT treatment design. 相似文献
289.
Prasada Raju V. N. K. V. Vetukuri Ravindra Vedantham Vijayavitthal Thippannachar Mathad Pratap Reddy Padi Vijaya Anand Ramasamy 《Helvetica chimica acta》2011,94(4):592-596
An efficient and concise synthesis of valacyclovir hydrochloride ( 4 ), which is a prodrug of acyclovir ( 3 ) is described. The synthesis was accomplished in two stages by coupling acyclovir with (2S)‐2‐azido‐3‐methylbutanoic acid followed by reduction (Scheme 2). 相似文献
290.