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841.
Sulistio A Widjaya A Blencowe A Zhang X Qiao G 《Chemical communications (Cambridge, England)》2011,47(4):1151-1153
Highly functionalized water soluble core cross-linked star (CCS) polymers having degradable cores and hierarchical functionalities spanning from the peripheral groups along the arms to the core have been synthesized entirely from amino acid building blocks. The core-isolated moieties were shown to undergo further reactions, such as click chemistry, as well as being capable of encapsulating water-insoluble drugs. 相似文献
842.
Stefan Feil Greg K. Koyanagi Diethard K. Bohme 《International journal of mass spectrometry》2009,280(1-3):38
Room temperature rate coefficients and product distributions are reported for the reactions initiated in D2O with dications of the alkaline-earth metals Mg, Ca, Sr and Ba. The measurements were performed with a selected-ion flow tube (SIFT) tandem mass spectrometer and electrospray ionization (ESI). Mg2+ reacts with water by a fast electron transfer leading to charge separation with a rate coefficient of 1.4 × 10−9 cm3 molecule−1 s−1. Ca2+ reacts with D2O in a first step to form the adduct Ca2+(D2O), with an effective bimolecular rate coefficient of 2.3 × 10−11 cm3 molecule−1 s−1, which then undergoes rapid charge separation by deuteron transfer to form CaOD+ and D3O+ in a second step with k = 7.9 × 10−10 cm3 molecule−1 s−1. The CaOD+ ion reacts further by clustering up to five more D2O molecules. Sr2+ clusters up to eight D2O molecules and Ba2+ up to seven D2O molecules, with the first addition of D2O being rate determining in each case and the last addition being distinctly slower, as might be expected from a transition in the occupation of the added water molecules from an inner to an outer hydration shell. 相似文献
843.
James T. Wiltshire Greg G. Qiao 《Journal of polymer science. Part A, Polymer chemistry》2009,47(6):1485-1498
Degradable polyester‐based star polymers with a high level of functionality in the arms were synthesized via the “arms first” approach using an acetylene‐functional block copolymer macroinitiator. This was achieved by using 2‐hydroxyethyl 2′‐methyl‐2′‐bromopropionate to initiate the ring‐opening polymerization (ROP) of caprolactone monomer followed by an atom transfer radical polymerization (ATRP) of a protected acetylene monomer, (trimethylsilyl)propargyl methacrylate. The hydroxyl end‐group of the resulting block copolymer macroinitiator was subsequently crosslinked under ROP conditions using a bislactone monomer, 4,4′‐bioxepanyl‐7,7′‐dione, to generate a degradable core crosslinked star (CCS) polymer with protected acetylene groups in the corona. The trimethylsilyl‐protecting groups were removed to generate a CCS polymer with an average of 1850 pendent acetylene groups located in the outer block segment of the arms. The increased functionality of this CCS polymer was demonstrated by attaching azide‐functionalized linear polystyrene via a copper (I)‐catalyzed cycloaddition reaction between the azide and acetylene groups. This resulted in a CCS polymer with “brush‐like” arm structures, the grafted segment of which could be liberated via hydrolysis of the polyester star structure to generate molecular brushes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1485–1498, 2009 相似文献
844.
A simple method of obtaining indole-3-acetic acid/ growth stimulating plant hormone/ labelled with tritium has been described. The preparate has specific radioactivity of 455 MBq/mmol, and 50% yield as compared to the initial amount of used substance. 相似文献
845.
Robert J. Harrison Martyn F. Guest Rick A. Kendall David E. Bernholdt Adrian T. Wong Mark Stave James L. Anchell Anthony C. Hess Rik J. Littlefield George L. Fann Jaroslaw Nieplocha Greg S. Thomas David Elwood Jeffrey L. Tilson Ron L. Shepard Albert F. Wagner Ian T. Foster Ewing Lusk Rick Stevens 《Journal of computational chemistry》1996,17(1):124-132
We discuss issues in developing scalable parallel algorithms and focus on the distribution, as opposed to the replication, of key data structures. Replication of large data structures limits the maximum calculation size by imposing a low ratio of processors to memory. Only applications which distribute both data and computation across processors are truly scalable. The use of shared data structures that may be independently accessed by each process even in a distributed memory environment greatly simplifies development and provides a significant performance enhancement. We describe tools we have developed to support this programming paradigm. These tools are used to develop a highly efficient and scalable algorithm to perform self-consistent field calculations on molecular systems. A simple and classical strip-mining algorithm suffices to achieve an efficient and scalable Fock matrix construction in which all matrices are fully distributed. By strip mining over atoms, we also exploit all available sparsity and pave the way to adopting more sophisticated methods for summation of the Coulomb and exchange interactions. © 1996 by John Wiley & Sons, Inc. 相似文献
846.
Ebert GW Juda WL Kosakowski RH Ma B Dong L Cummings KE Phelps MV Mostafa AE Luo J 《The Journal of organic chemistry》2005,70(11):4314-4317
Functionalized arylcopper reagents have been produced in good yields at 25 degrees C from activated copper and the corresponding functionalized aryl iodides without the need of traditional organolithium or Grignard precursors. These organocopper compounds will undergo carboxylation with CO(2) to form the corresponding copper benzoates. In turn, these salts can be acidified to produce the functionalized aryl acids or treated with appropriate alkyl halides in the presence of a dipolar aprotic solvent to generate the corresponding aryl esters. This methodology permits the formation of functionalized organic acids and esters that could not be generated by the carboxylation of organomagnesium compounds. 相似文献
847.
Thomas G. McKenzie Jing M. Ren Dave E. Dunstan Edgar H. H. Wong Greg G. Qiao 《Journal of polymer science. Part A, Polymer chemistry》2016,54(1):135-143
Core cross‐linked star (CCS) polymers with radiating arms composed of high‐order multiblock copolymers have been synthesized in a one‐pot system via iterative copper‐mediated radical polymerization. The employed “arm‐first” technique ensures the multiblock sequence of the macroinitiator is carried through to the star structure with no arm defects. The versatility of this approach is demonstrated by the synthesis of three distinct star polymers with differing arm compositions, two with an alternating ABABAB block sequence and one with six different block units (i.e. ABCDEF). Owing to the star architecture, CCS polymers in which the arm composition consists of alternating hydrophilic–hydrophobic (ABABAB) segments undergo supramolecular self‐assembly in selective solvents, whereas linear polymers with the same block sequence did not yield self‐assembled structures, as evidenced by DLS analysis. The combination of microstructural and topological control in CCS polymers offers exciting possibilities for the development of tailor‐made nanoparticles with spatially defined regions of functionality. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 135–143 相似文献
848.
849.
850.
D. Kasprowicz A. Trzaskowska A. Majchrowski E. Michalski M. Drozdowski S. Mielcarek 《Crystal Research and Technology》2009,44(12):1263-1266
In this paper we present the study of the acoustic phonons propagating in Er3+‐doped KGd(WO4)2 single crystals by Brillouin spectroscopy. For the investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101] and [110] have been determined. Moreover, the values of the elastic constants: C22, C44 and C66 of Er3+‐doped KGd(WO4)2 single crystals have been estimated. It was revealed that the presence of the Er3+‐ions in KGd(WO4)2 crystals, for the used doping concentration 1 at% does not influence their elastic properties. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献