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541.
Corrigendum: Visible‐Light‐Driven Hydrogen Evolution Using Planarized Conjugated Polymer Photocatalysts 下载免费PDF全文
542.
Nick?DeGraan-Weber Jun?Zhang James?P.?ReillyEmail author 《Journal of the American Society for Mass Spectrometry》2016,27(12):2041-2053
Six ion fragmentation techniques that can distinguish aspartic acid from its isomer, isoaspartic acid, were compared. MALDI post-source decay (PSD), MALDI 157 nm photodissociation, tris(2,4,6-trimethoxyphenyl)phosphonium bromide (TMPP) charge tagging in PSD and photodissociation, ESI collision-induced dissociation (CID), electron transfer dissociation (ETD), and free-radical initiated peptide sequencing (FRIPS) with CID were applied to peptides containing either aspartic or isoaspartic acid. Diagnostic ions, such as the y–46 and b+H2O, are present in PSD, photodissociation, and charge tagging. c?+57 and z–57 ions are observed in ETD and FRIPS experiments. For some molecules, aspartic and isoaspartic acid yield ion fragments with significantly different intensities. ETD and charge tagging appear to be most effective at distinguishing these residues. 相似文献
543.
Inside Cover: Integrin‐Targeting Knottin Peptide–Drug Conjugates Are Potent Inhibitors of Tumor Cell Proliferation (Angew. Chem. Int. Ed. 34/2016) 下载免费PDF全文
544.
Visible‐Light‐Driven Hydrogen Evolution Using Planarized Conjugated Polymer Photocatalysts 下载免费PDF全文
Dr. Reiner Sebastian Sprick Dr. Baltasar Bonillo Rob Clowes Pierre Guiglion Nick J. Brownbill Dr. Benjamin J. Slater Dr. Frédéric Blanc Dr. Martijn A. Zwijnenburg Prof. Dave J. Adams Prof. Andrew I. Cooper 《Angewandte Chemie (International ed. in English)》2016,55(5):1792-1796
Linear poly(p‐phenylene)s are modestly active UV photocatalysts for hydrogen production in the presence of a sacrificial electron donor. Introduction of planarized fluorene, carbazole, dibenzo[b,d]thiophene or dibenzo[b,d]thiophene sulfone units greatly enhances the H2 evolution rate. The most active dibenzo[b,d]thiophene sulfone co‐polymer has a UV photocatalytic activity that rivals TiO2, but is much more active under visible light. The dibenzo[b,d]thiophene sulfone co‐polymer has an apparent quantum yield of 2.3 % at 420 nm, as compared to 0.1 % for platinized commercial pristine carbon nitride. 相似文献
545.
546.
On the dynamics of fragment isomerization in collision-induced dissociation of peptides 总被引:4,自引:0,他引:4
Polfer NC Bohrer BC Plasencia MD Paizs B Clemmer DE 《The journal of physical chemistry. A》2008,112(6):1286-1293
The structures of peptide collision-induced dissociation (CID) product ions are investigated using ion mobility/mass spectrometry techniques combined with theoretical methods. The cross-section results are consistent with a mixture of linear and cyclic structures for both b4 and a4 fragment ions. Direct evidence for cyclic structures is essential in rationalizing the appearance of fragments with scrambled (i.e., permutated) primary structures, as the cycle may not open up where it was initially formed. It is demonstrated here that cyclic and linear a4 structures can interconvert freely as a result of collisional activation, implying that isomerization takes place prior to dissociation. 相似文献
547.
Gary S. Groenewold Dr. Michael J. Van Stipdonk Prof. Wibe A. de Jong Dr. Jos Oomens Dr. Garold L. Gresham Dr. Michael E. McIlwain Dr. Da Gao Dr. Bertrand Siboulet Dr. Lucas Visscher Prof. Michael Kullman Nick Polfer Prof. 《Chemphyschem》2008,9(9):1278-1285
UO2+–solvent complexes having the general formula [UO2(ROH)]+ (R=H, CH3, C2H5, and n‐C3H7) are formed using electrospray ionization and stored in a Fourier transform ion cyclotron resonance mass spectrometer, where they are isolated by mass‐to‐charge ratio, and then photofragmented using a free‐electron laser scanning through the 10 μm region of the infrared spectrum. Asymmetric O=U=O stretching frequencies (ν3) are measured over a very small range [from ~953 cm?1 for H2O to ~944 cm?1 for n‐propanol (n‐PrOH)] for all four complexes, indicating that the nature of the alkyl group does not greatly affect the metal centre. The ν3 values generally decrease with increasing nucleophilicity of the solvent, except for the methanol (MeOH)‐containing complex, which has a measured ν3 value equal to that of the n‐PrOH‐containing complex. The ν3 frequency values for these U(V) complexes are about 20 cm?1 lower than those measured for isoelectronic U(VI) ion‐pair species containing analogous alkoxides. ν3 values for the U(V) complexes are comparable to those for the anionic [UO2(NO3)3]? complex, and 40–70 cm?1 lower than previously reported values for ligated uranyl(VI) dication complexes. The lower frequency is attributed to weakening of the O?U?O bonds by repulsion related to reduction of the U metal centre, which increases electron density in the antibonding π* orbitals of the uranyl moiety. Computational modelling of the ν3 frequencies using the B3LYP and PBE functionals is in good agreement with the IRMPD measurements, in that the calculated values fall in a very small range and are within a few cm?1 of measurements. The values generated using the LDA functional are slightly higher and substantially overestimate the trends. Subtleties in the trend in ν3 frequencies for the H2O–MeOH–EtOH–n‐PrOH series are not reproduced by the calculations, specifically for the MeOH complex, which has a lower than expected value. 相似文献
548.
Mullen KM Johnstone KD Webb M Bampos N Sanders JK Gunter MJ 《Organic & biomolecular chemistry》2008,6(2):278-286
The thermodynamically controlled self-assembly of rotaxane and pseudorotaxane systems consisting of (i) a naphthodiimide thread unit terminated at one end with a pyridine ligand, and covalently linked at the other to a gel-phase polystyrene resin support, (ii) a dinaphtho-crown ether shuttle unit, and (iii) a ruthenium carbonyl metalloporphyrin stopper unit, is investigated by high resolution magic angle spinning proton (HR MAS 1H) NMR spectroscopy. The effects of variable concentration of the solution-phase components, the temperature, and added Li+ and Na+ ions are described, and the limitations of the technique are addressed. The dynamic behaviour is compared directly to the solution-phase analogues, where a bulky stopper group is substituted for the polystyrene resin bead. 相似文献
549.
Parigoridi IE Corban GJ Hadjikakou SK Hadjiliadis N Kourkoumelis N Kostakis G Psycharis V Raptopoulou CP Kubicki M 《Dalton transactions (Cambridge, England : 2003)》2008,(38):5159-5165
The reaction of 2-pyrimidone hydrochloride ([C(4)H(5)N(2)O](+)[Cl](-) or [PMOH(2)](+)[Cl](-)) with diiodine in a dichloromethane-methanol solution resulted in the formation of ([C(4)H(5)N(2)O](+))(2)[I(2)Cl(2)](2-) (1) complex. The compound was characterized by elemental analysis, FT-IR, DTA-TG and conductivity titrations. The crystal structure of 1 was also determined by X-ray diffraction at 294(1) K. Compound 1 is monoclinic, space group P2(1)/n, consisting of two cationic [PMOH(2)](+) species and a [I(2)Cl(2)](2-) counter dianion. The cation is in its keto form. Direct reaction of thiazolidine-2-thione (tzdtH), with diiodine in dichloromethane solution, on the other hand, led to the formation of a crystalline solid which contained two complexes of formulae [(tzdtH)(2)I](+)[I(3)](-).2I(2) (2) and [(tzdtH)I(2)](2).I(2) (2a) in a ratio of 90 to 10%. Complex 2a was characterized by X-ray analysis at 180(2) K. Compound is monoclinic, space group C2/c and contains two units of [(tzdtH)I(2)] "spoke" structures. Compound 1, as well as the known species iodonium salt [(tzdtH)(2)I](+)[I(3)](-).2I(2) (2) and the charge transfer (CT) iodine complexes of formulae [(bztzdtH)I(2)] (3) and [(bztzdtH)I(2)].I(2) (4) (bztzdtH = 2-mercaptobenzothiazole) with "spoke" and extended "spoke" structures respectively, were tested for their oxidizing activity towards 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-o-benzoquinone. 相似文献
550.
We prove that, on a complete noncompact Riemannian manifold with bounded geometry, the Lp boundedness of the Riesz transform, for p>2, is stable under a quasi-isometric and integrable change of metric. As an intermediate
step, we treat the case of weighted divergence form operators in the Euclidean space. 相似文献