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911.
Enhanced Fibril Fragmentation of N‐Terminally Truncated and Pyroglutamyl‐Modified Aβ Peptides 下载免费PDF全文
Melanie Wulff Monika Baumann Anka Thümmler Dr. Jay K. Yadav Liesa Heinrich Uwe Knüpfer Dagmar Schlenzig Dr. Angelika Schierhorn Dr. Jens‐Ulrich Rahfeld Dr. Uwe Horn Prof. Dr. Jochen Balbach Prof. Dr. Hans‐Ulrich Demuth Prof. Dr. Marcus Fändrich 《Angewandte Chemie (International ed. in English)》2016,55(16):5081-5084
N‐terminal truncation and pyroglutamyl (pE) formation are naturally occurring chemical modifications of the Aβ peptide in Alzheimer's disease. We show herein that these two modifications significantly reduce the fibril length and the transition midpoint of thermal unfolding of the fibrils, but they do not substantially perturb the fibrillary peptide conformation. This observation implies that the N terminus of the unmodified peptide protects Aβ fibrils against mechanical stress and fragmentation and explains the high propensity of pE‐modified peptides to form small and particularly toxic aggregates. 相似文献
912.
Ryan T. McGuire Connor M. Simon Arun A. Yadav Michael J. Ferguson Mark Stradiotto 《Angewandte Chemie (International ed. in English)》2020,59(23):8952-8956
The development of Ni‐catalyzed C?N cross‐couplings of sulfonamides with (hetero)aryl chlorides is reported. These transformations, which were previously achievable only with Pd catalysis, are enabled by use of air‐stable ( L )NiCl(o‐tol) pre‐catalysts (L= PhPAd‐DalPhos and PAd2‐DalPhos ), without photocatalysis. The collective scope of (pseudo)halide electrophiles (X=Cl, Br, I, OTs, and OC(O)NEt2) demonstrated herein is unprecedented for any reported catalyst system for sulfonamide C?N cross‐coupling (Pd, Cu, Ni, or other). Preliminary competition experiments and relevant coordination chemistry studies are also presented. 相似文献
913.
Glyceride‐Mimetic Prodrugs Incorporating Self‐Immolative Spacers Promote Lymphatic Transport,Avoid First‐Pass Metabolism,and Enhance Oral Bioavailability 下载免费PDF全文
Dr. Luojuan Hu Dr. Tim Quach Dr. Sifei Han Dr. Shea F. Lim Preeti Yadav Danielle Senyschyn Dr. Natalie L. Trevaskis Dr. Jamie S. Simpson Prof. Christopher J. H. Porter 《Angewandte Chemie (International ed. in English)》2016,55(44):13700-13705
First‐pass hepatic metabolism can significantly limit oral drug bioavailability. Drug transport from the intestine through the lymphatic system, rather than the portal vein, circumvents first‐pass metabolism. However, the majority of drugs do not have the requisite physicochemical properties to facilitate lymphatic access. Herein, we describe a prodrug strategy that promotes selective transport through the intestinal lymph vessels and subsequent release of drug in the systemic circulation, thereby enhancing oral bioavailability. Using testosterone (TST) as a model high first‐pass drug, glyceride‐mimetic prodrugs incorporating self‐immolative (SI) spacers, resulted in remarkable increases (up to 90‐fold) in TST plasma exposure when compared to the current commercial product testosterone undecanoate (TU). This approach opens new opportunities for the effective development of drugs where oral delivery is limited by first‐pass metabolism and provides a new avenue to enhance drug targeting to intestinal lymphoid tissue. 相似文献
914.
Efficient syntheses of (+)-proto, (−)-gala quercitols and carba-l-rhamnose from d-(−)-quinic acid are described. 相似文献
915.
The coupling of (E)- and (Z)-hex-3-ene-1,6-ditosylamide with various aldehydes in the presence of 10 mol % Sc(OTf)3 gave the corresponding trans- and cis-fused 1,5-ditosyl-octahydro-1H-pyrrolo[3,2-c]pyridines, respectively, in good yields via intramolecular aza-Prins cyclization, whereas the coupling of (E)- and (Z)-N-(6-hydroxyhex-3-enyl)-4-methylbenzenesulfonamide afforded the corresponding trans- and cis-fused octahydro-1-tosylpyrano[4,3-b]pyrroles derivatives, respectively, via intramolecular Prins-cyclization. 相似文献
916.
Jhillu Singh Yadav Dandekar Chandrakanth Yerragorla Gopala Rao Kontham Ravindar Basi V. Subba Reddy 《Helvetica chimica acta》2010,93(7):1432-1438
The stereoselective total synthesis of an antiproliferative and antifungal α‐pyrone natural product (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one is described. The key steps involved are the Prins cyclization, Mitsunobu reaction, and ring‐closing metathesis reaction. 相似文献
917.
P. S. Ramanjaneyulu Komal Chandra A. S. Kulkarni C. S. Yadav Abhijit Saha M. K. Saxena B. S. Tomar K. L. Ramakumar 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(1):117-124
Total gas content and its composition are important specifications for sintered nuclear fuel pellets particularly in the case of fast breeder reactor fuels. Most commonly, total gas content and its composition is determined by hot vacuum extraction-quadrupole mass spectrometry (HVE-QMS). A number of parameters in this methodology such as temperature, duration of heating for quantitative extraction of evolved gases, total volume of the system, gas analysis conditions etc. need to be optimized for reliable measurements. In addition, sensitivity factors for various gases like H2, CH4, N2, CO, O2 and CO2 in quadrupole mass spectrometry required for quantification of results have been determined and validated employing reference gas mixtures of known composition. Employing these optimized conditions total gas content and its composition in blanket pellets (uranium oxide pellets) of Indian prototype fast breeder reactor was determined employing HVE-QMS. The relative expanded uncertainty (at a coverage factor k = 2) in the measurement of total gas content excluding hydrogen was estimated as per ISO guidelines and it was found to be 9.2 %. 相似文献
918.
Veejendra K. Yadav 《合成通讯》2013,43(7):1023-1032
The allylic tin(IV) complex 2 prepared from the dialkoxyanion of diethyl tartarate, tin(II) chloride, and 3-bromocyclohexene reacts with aldehydes to furnish cyclohexenyl substituted homoallylic alcohols. 相似文献
919.
Aldoximes undergo rapid dehydration with H2SO4/ SiO2 solid support, under microwave irradiation in dry media to afford nitriles in high yields. 相似文献
920.
Santosh SinghLal Dhar S. Yadav 《Tetrahedron letters》2012,53(38):5136-5140
An efficient N-heterocyclic carbene (NHC)-catalyzed direct thioesterification of aldehydes and α,β-unsaturated aldehydes (enals) with diaryl disulfides is reported. The protocol involves carbonyl umpolung reactivity of aldehydes and enals in which the carbonyl carbon attacks nucleophilically on diaryl disulfides to afford thioesters and α,β-unsaturated thioesters, respectively. However, aliphatic aldehydes are not suitable substrates for this reaction. No by-product formation, complete atom-economy, shorter reaction time, ambient temperature, operational simplicity, and high yields are the salient features of the present procedure. 相似文献