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991.
Dr. George N. Khairallah Dr. Alan T. Maccarone Dr. Huong T. Pham Timothy M. Benton Dr. Tony Ly Dr. Gabriel da Silva Prof. Stephen J. Blanksby Prof. Richard A. J. O'Hair 《Angewandte Chemie (International ed. in English)》2015,54(44):12947-12951
Although the deleterious effects of ozone on the human respiratory system are well‐known, many of the precise chemical mechanisms that both cause damage and afford protection in the pulmonary epithelial lining fluid are poorly understood. As a key first step to elucidating the intrinsic reactivity of ozone with proteins, its reactions with deprotonated cysteine [Cys?H]? are examined in the gas phase. Reaction proceeds at near the collision limit to give a rich set of products including 1) sequential oxygen atom abstraction reactions to yield cysteine sulfenate, sulfinate and sulfonate anions, and significantly 2) sulfenate radical anions formed by ejection of a hydroperoxy radical. The free‐radical pathway occurs only when both thiol and carboxylate moieties are available, implicating electron‐transfer as a key step in this reaction. This novel and facile reaction is also observed in small cys‐containing peptides indicating a possible role for this chemistry in protein ozonolysis. 相似文献
992.
Improved ion optics for introduction of ions into a 9.4‐T Fourier transform ion cyclotron resonance mass spectrometer
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Yu Chen Nathan K. Kaiser Xibei Dang Yehia M. Ibrahim Randolph V. Norheim Gordon A. Anderson Richard D. Smith Alan G. Marshall 《Journal of mass spectrometry : JMS》2015,50(1):280-284
Enhancements to the ion source and transfer optics of our 9.4 T Fourier transform ion cyclotron resonance (ICR) mass spectrometer have resulted in improved ion transmission efficiency for more sensitive mass measurement of complex mixtures at the MS and MS/MS levels. The tube lens/skimmer has been replaced by a dual ion funnel and the following octopole by a quadrupole for reduced ion cloud radial expansion before transmission into a mass‐selective quadrupole. The number of ions that reach the ICR cell is increased by an order of magnitude for the funnel/quadrupole relative to the tube lens/skimmer/octopole. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
993.
994.
Bertrand Reuillard Solène Gentil Marie Carrière Alan Le Goff Serge Cosnier 《Chemical science》2015,6(9):5139-5143
We report the non-covalent functionalization of a multi-walled carbon nanotube (MWCNT) electrode with a biomimetic model of the horseradish peroxidase (HRP) active site. By modifying the MWCNT electrode surface with imidazole-modified polypyrrole, a new biomimetic complex of HRP was synthesized on the MWCNT sidewalls via the coordination of imidazole (Im) to the metal centre of iron protoporphyrin IX, affording (Im)(PP)FeIII. Compared to the pi-stacking of non-coordinated (PP)FeIII on a MWCNT electrode, the (Im)(PP)FeIII-modified MWCNT electrode exhibits higher electrocatalytic activity with an I max = 0.52 mA cm–2 for the reduction of H2O2, accompanied by a high onset potential of 0.43 V vs. Ag/AgCl. The performances of these novel surface-confined HRP mimics were compared to those of a MWCNT electrode modified by HRP. Although the enzyme electrode displays a higher electrocatalytic activity towards H2O2 reduction, the (Im)(PP)FeIII-modified MWCNT electrode exhibits a markedly higher operational stability, retaining 63% of its initial activity after one month. 相似文献
995.
Alan K. Brisdon Abeer M. T. Muneer Robin G. Pritchard 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(10):900-902
Halogen bonding is an intermolecular interaction capable of being used to direct extended structures. Typical halogen‐bonding systems involve a noncovalent interaction between a Lewis base, such as an amine, as an acceptor and a halogen atom of a halofluorocarbon as a donor. Vapour‐phase diffusion of 1,4‐diazabicyclo[2.2.2]octane (DABCO) with 1,2‐dibromotetrafluoroethane results in crystals of the 1:1 adduct, C2Br2F4·C6H12N2, which crystallizes as an infinite one‐dimensional polymeric structure linked by intermolecular N...Br halogen bonds [2.829 (3) Å], which are 0.57 Å shorter than the sum of the van der Waals radii. 相似文献
996.
Analysis of corrosion scales formed on steel at high temperatures in hydrocarbons containing model naphthenic acids and sulfur compounds
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Corrosive naphthenic acids and sulfur compounds in crude oils present a major challenge for refineries from a corrosion perspective. Although it is accepted that some sulfur compounds may form protective FeS scales on the metal surface and deter corrosion, attempting to correlate the characteristics of FeS scale with its protective properties has not been successful. Given the complex chemical compositions of real crudes, model sulfur compound and model naphthenic acids were used to mimic the corrosion by crude fractions in the present study. The iron sulfide scale formed by the model sulfur/acid compounds was challenged by naphthenic acids under high‐velocity conditions to examine its protectiveness against corrosion. Moreover, the scale was analyzed with transmission electron microscope/energy dispersive X‐ray spectroscopy technique, and a layer of iron oxide formed on the 5Cr steel was found when naphthenic acids were present in the solution. The iron oxide layer appeared to be important for maintaining protection against naphthenic acid corrosion, and further analysis revealed that it was composed of magnetite. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
997.
Fourteen common drugs of abuse were identified in spiked oral fluid (ng mL−1 levels), analyzed directly from medical swabs using touch spray mass spectrometry (TS-MS), exemplifying a rapid test for drug detection. Multiple stages of mass analysis (MS2 and MS3) provided identification and detection limits sought by international forensic and toxicological societies, Δ9-THC and buprenorphine excluded. The measurements were made using a medical swab as both the sampling probe and means of ionization. The adaptation of medical swabs for TS-MS analysis allows non-invasive and direct sampling of neat oral fluid. Data acquisition was rapid, seconds per drug, and MS3 ensured reliable identification of illicit drugs. The reported data were acquired to investigate (i) ionization of common drugs from commercial swabs, (ii) ion intensity over spray duration, and (iii) dynamic range, all as initial steps in development of a quantitative method. The approach outlined is intended for point-of-care drug testing using oral fluid in clinical applications as well as in situ settings, viz. in forensic applications. The proof-of-concept results presented will require extension to other controlled substances and refinement in analytical procedures to meet clinical/legal requirements. 相似文献
998.
Synthesis,Characterisation and Reactivity of Copper(I) Amide Complexes and Studies on Their Role in the Modified Ullmann Amination Reaction
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Simon Sung Dr. D. Christopher Braddock Prof. Alan Armstrong Dr. Colin Brennan Dr. David Sale Dr. Andrew J. P. White Dr. Robert P. Davies 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7179-7192
A series of copper(I) alkylamide complexes have been synthesised; copper(I) dicyclohexylamide ( 1 ), copper(I) 2,2,6,6‐tetramethylpiperidide ( 2 ), copper(I) pyrrolidide ( 3 ), copper(I) piperidide ( 4 ), and copper(I) benzylamide ( 5 ). Their solid‐state structures and structures in [D6]benzene solution are characterised, with the aggregation state in solution determined by a combination of DOSY NMR spectroscopy and DFT calculations. Complexes 1 , 2 and 4 are shown to exist as tetramers in the solid state by X‐ray crystallography. In [D6]benzene solution, complexes 1 , 2 and 5 were found by using 1H DOSY NMR to exist in rapid equilibrium between aggregates with average aggregation numbers of 2.5, 2.4 and 3.3, respectively, at 0.05 M concentration. Conversely, distinct trimeric, tetrameric and pentameric forms of 3 and 4 were distinguishable by one‐dimensional 1H and 1H DOSY NMR spectroscopy. Complexes 3 – 5 are found to react stoichiometrically with iodobenzene, in the presence or absence of 1,10‐phenanthroline as an ancillary ligand, to give arylamine products indicative of their role as potential intermediates in the modified Ullmann reaction. The role of phenanthroline has also been explored both in the stoichiometric reaction and in the catalytic Ullmann protocol. 相似文献
999.
Pau Moneva Lorente Dr. Céline Besnard Prof. Alan F. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(24):8851-8858
Assembly of two ditopic units, a phenanthroline substituted by 4‐ethynyl pyridines at the 2‐and 9‐positions and a dimetallic paddlewheel, gives a linear chain polymer rather than a closed cyclic species, which would appear equally possible. The chain may be decorated by binding a copper‐containing macrocycle around the phenanthroline units to form a polypseudorotaxane. When two phenanthroline ligands are assembled in a first step around copper(I), the paddlewheel acceptor can link them in a second step to form a two‐dimensional interwoven grid that resembles the form of a chain‐link fence. Each copper(I) centre in this structure is chiral, and the crystal shows complete homochirality, implying selection during the assembly process. 相似文献
1000.
Adding a Structural Context to the Deprotometalation and Trans‐Metal Trapping Chemistry of Phenyl‐Substituted Benzotriazole
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Dr. M. Ángeles Fuentes Dr. Alan R. Kennedy Prof. Robert E. Mulvey Dr. John A. Parkinson Dr. Toni Rantanen Dr. Stuart D. Robertson Prof. Victor Snieckus 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14812-14822
Organometallic bases are becoming increasingly complex, because mixing components can lead to bases superior to single‐component bases. To better understand this superiority, it is useful to study metalated intermediate structures prior to quenching. This study is on 1‐phenyl‐1H‐benzotriazole, which was previously deprotonated by an in situ ZnCl2 ? TMEDA/LiTMP (TMEDA=N,N,N′,N′‐tetramethylethylenediamine; TMP=2,2,6,6‐tetramethylpiperidide) mixture and then iodinated. Herein, reaction with LiTMP exposes the deficiency of the single‐component base as the crystalline product obtained was [{4‐R‐1‐(2‐lithiophenyl)‐1H‐benzotriazole ? 3THF}2], [R=2‐C6H4(Ph)NLi], in which ring opening of benzotriazole and N2 extrusion had occurred. Supporting lithiation by adding iBu2Al(TMP) induces trans‐metal trapping, in which C?Li bonds transform into C?Al bonds to stabilise the metalated intermediate. X‐ray diffraction studies revealed homodimeric [(4‐R′‐1‐phenyl‐1H‐benzotriazole)2], [R′=(iBu)2Al(μ‐TMP)Li], and its heterodimeric isomer [(4‐R′‐1‐phenyl‐1H‐benzotriazole){2‐R′‐1‐phenyl‐1H‐benzotriazole}], whose structure and slow conformational dynamics were probed by solution NMR spectroscopy. 相似文献