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61.
A derivatization protocol that exploits the rapid reaction between arenediazonium ions and a suitable coupling agent followed by high-performance liquid chromatography analyses of the reaction mixture was employed to determine the product distribution, the rate constants for product formation and the association constant of 4-nitrobenzenediazonium, PNBD, ion with beta-cyclodextrin, beta-CD. The derivatization of PNBD with the coupling agent leads to the formation of a stable azo dye that prevents by-side reactions of PNBD with the solvents of the mobile phase, including water, or the metallic parts of the chromatographic system that would eventually lead to erroneous identification and quantification of dediazoniation products. The results show that in the presence of beta-CD, nitrobenzene is formed at the expense of 4-nitrophenol, which is the major product in its absence. The observed rate constants for the interaction between PNBD and beta-CD increase upon increasing [beta-CD] showing a saturation profile indicative of the formation of an inclusion complex between PNBD and beta-CD. By fitting the experimental data to a simplified Lineaweaver-Burk equation, the corresponding association constant and the maximum acceleration rate of beta-CD towards PNBD were estimated. The protocol is applicable under a variety of experimental conditions provided that the rate of the coupling reaction is much faster than that of dediazoniation. 相似文献
62.
Mauro L. Bonardi Flavia Groppi Simone Manenti Elisa Persico Luigi Gini Kamel Abbas Uwe Holzwarth Federica Simonelli Zeev B. Alfassi 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):1-7
Very high specific activity (AS) 186gRe could be produced by either proton or deuteron cyclotron irradiation on highly enriched 186W target in no-carrier-added (NCA) form, leading to a AS very close to the theoretical carrier free (CF) value of 6.88 GBq μg−1. Thick Target Yields (TTYs), obtained irradiating both thick metal W targets of natural isotopic composition and highly enriched
powdered 186W targets, were measured at different particles energies taking into account high accuracy and precision. The evaluation of
radionuclidic purities of 186gRe obtained activating highly enriched 186W by both p and d were also carried out and accurately compared. The thin-target excitation functions for all Re (A = 181,
182, 183, 184, 186 and their metastable levels), and W and Ta coproduced radionuclides will be presented elsewhere in deep
details. 相似文献
63.
Vincenzo Cunsolo Elisa Cairone Rosaria Saletti Vera Muccilli Salvatore Foti 《Rapid communications in mass spectrometry : RCM》2009,23(13):1907-1916
Two coeluting components, with experimentally measured Mr values of 25529 and 24606 Da, were identified by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and mass spectrometric analysis in the dephosphorylated casein fraction of a milk sample collected from an individual donkey belonging to the Ragusano breed of the east of Sicily. By coupling enzymatic digestions, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) and RP‐HPLC/nano‐electrospray ionization tandem mass spectrometry (nESI‐MS/MS) analysis, the two proteins were identified as donkey β‐CNs and their sequences characterized completely, using the two known β‐CNs from mare as references. The two donkey β‐CNs, showing a mass difference of 923 Da, differ by the presence of the domain E27SITHINK34 in the full‐length component (Mr 25529 Da). In comparison with the mare's β‐CNs used as reference, they present nine amino acid substitutions: L→S37, R→H52, S→N81, P→V84, L→V91, R→Q203, P→L/I206, L→F210 and A→P219. Together, these substitutions account for the increase of 18 Da in the Mr of the donkey β‐CNs with respect to the counterparts from the mare. The molecular mass determination by ESI‐MS for the phosphorylated proteins showed that the full‐length component was composed of highly multi‐phosphorylated isoforms with five to seven phosphate groups. By analogy with the homologous mare's β‐CNs, the full‐length (226 amino acids) β‐CN was termed variant A, whereas the shorter (218 amino acids) β‐CN was termed variant AΔ5. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
64.
J. Badier M. Bardadin-Otwinowska C. Bemporad U. Berthon H. Bienvenu J. Boucrot J. Bourotte G. Burgun O. Callot Ph. Charpentier A. M. Cnops M. Cohen F. Constantini M. Crozon D. Décamp P. Delpierre J. F. Detoeuf P. Espigat B. Gandois G. R. Giannini V. Hajjar M. Hansroul Y. Karyotakis P. Lariccia P. Le D? J. Mas A. Michelini G. C. Moneti M. Moniez E. Paré G. Rahal-Callot M. Rumpf O. Runolfsson A. Tilquin S. Weisz NA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1986,31(3):341-347
Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦P T ≦6 GeV/c and center-of-mass rapidity ?0.4≦y *≦1.2. Inclusive cross sections are given for incident π± and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given. 相似文献
65.
Federica Rossella Elisa Polledri Valentina Bollati Andrea Baccarelli Silvia Fustinoni 《Rapid communications in mass spectrometry : RCM》2009,23(17):2637-2646
A method for the determination of DNA global methylation, taken as the ratio (%) of 5‐methylcytosine (5mCyt) versus the sum of cytosine (Cyt) and 5mCyt, via gas chromatography/mass spectrometry (GC/MS), was developed and validated. DNA (2.5 µg) was hydrolyzed with aqueous formic acid 88%, spiked with cytosine‐2,4‐13C2,15N3 and 5‐methyl‐2H3‐cytosine‐6‐2H1 as internal standards, and derivatized with N‐methyl‐N‐(tert‐butyldimethylsilyl)trifluoroacetamide and 1% tert‐butyldimethylchlorosilane, in the presence of acetonitrile and pyridine. GC/MS, operating in single ion monitoring mode, separated and specifically detected all nucleobases as tert‐butyldimethylsilyl derivatives, without interferences, with the exception of guanosine. The method was linear throughout the range of clinical interest and had good sensitivity, with a limit of quantification of 3.2 pmol for Cyt and 0.056 pmol for 5mCyt, the latter corresponding to a methylation level of 0.41%. Intra‐ and inter‐day precision and accuracy were below 4.0% for both analytes and methylation. The matrix absolute effect, process efficiency and coefficient of variation ranged from 96.5 to 101.2%. The matrix relative effect was below 1%. The method was applied to the analysis of different human DNAs, including: nonmethylated DNA from PCR (methylation 0.00%), hypermethylated DNA prepared using M.SssI CpG methyltransferase (methylation 18.05%), DNA from peripheral blood leukocytes of healthy subjects (N = 6, median methylation 5.45%), DNA from bone marrow of leukemia patients (N = 5, 3.58%) and DNA from myeloma cell lines (N = 4, 2.74%). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
66.
67.
68.
Elisa Leyva Socorro Leyva-Ramos Rogelio Jiménez-Cataño Telma A. de Luna-Méndez Agobardo Cárdenas-Chaparro 《合成通讯》2017,47(6):604-608
Reaction of o-halonitrobenzenes with sodium azide under reflux of DMF/H2O gives benzofuroxans in one step in moderate to good yields. This is a faster methodology compared to the conventional procedure involving the preparation and subsequent pyrolysis of o-nitrophenyl azides. For comparison, the reaction was also performed under phase-transfer catalysis. 相似文献
69.
70.
Elisa Barea Dr. Giulia Tagliabue Wen‐Guo Wang Dr. Manuel Pérez‐Mendoza Dr. Laura Mendez‐Liñan Francisco J. López‐Garzon Prof. Simona Galli Dr. Norberto Masciocchi Prof. Jorge A. R. Navarro Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):931-937
The novel coordination polymers [Cu(Hoxonic)(H2O)]n ( 1 ) and [Cu(Hoxonic)(bpy)0.5]n ? 1.5 n H2O ( 2?H2O ) (H3oxonic: 4,6‐dihydroxy‐1,3,5‐triazine‐2‐carboxylic acid; bpy: 4,4′‐bipyridine) have been isolated and structurally characterised by ab initio X‐ray powder diffraction. The dense phase 1 contains 1D zig‐zag chains in which Hoxonic dianions bridge square‐pyramidal copper(II) ions, apically coordinated by water molecules. On the contrary, 2?H2O , prepared by solution and solventless methods, is based on 2D layers of octahedral copper(II) ions bridged by Hoxonic ligands, further pillared by bpy spacers. The resulting pro‐porous 3D network possesses small hydrated cavities. The reactivity, thermal, magnetic and adsorptive properties of these materials have been investigated. Notably, the adsorption studies on 2 show that this material possesses unusual adsorption behaviour. Indeed, guest uptake is facilitated by increasing the thermal energy of both the guest and the framework. Thus, neither N2 at 77 K nor CO2 at 195 K are incorporated, and CH4 is only minimally adsorbed at 273 K and high pressures (0.5 mmol g?1 at 2500 kPa). By contrast, CO2 is readily incorporated at 273 K (up to 2.5 mmol g?1 at 2500 kPa). The selectivity of 2 towards CO2 over CH4 has been investigated by means of variable‐temperature zero coverage adsorption experiments and measurement of breakthrough curves of CO2/CH4 mixtures. The results show the highly selective incorporation of CO2 in 2 , which can be rationalised on the basis of the framework flexibility and polar nature of its voids. 相似文献