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911.
Zhang Y Gao J Li W Lee H Lu BZ Senanayake CH 《The Journal of organic chemistry》2011,76(15):6394-6400
A one-pot process has been developed for the synthesis of 8-arylquinolines via Pd-catalyzed borylation of quinoline-8-yl halides and subsequent Suzuki-Miyaura coupling with aryl halides using n-BuPAd(2) as ligand. Yields of up to 98% were obtained. 相似文献
912.
Wei X Henriksen NM Skalicky JJ Harper MK Cheatham TE Ireland CM Van Wagoner RM 《The Journal of organic chemistry》2011,76(14):5515-5523
Four new tris-bromoindole cyclic guanidine alkaloids, araiosamines A-D, were isolated from the methanol extract of a marine sponge, Clathria (Thalysias) araiosa, collected from Vanuatu. Their carbon skeletons delineate a new class of indole alkaloids apparently derived from a linear polymerization process involving a carbon-carbon bond formation. Comparison of the structures including the relative configurations suggests a common intermediate containing a dihydroaminopyrimidine moiety capable of undergoing various modalities of conjugate addition to yield unprecedented ring systems. 相似文献
913.
Stephen Hull Stefan T. Norberg Istaq Ahmed Sten G. Eriksson Chris E. Mohn 《Journal of solid state chemistry》2011,184(11):2925-2935
The structural properties of the binary alkaline-earth halides SrCl2, SrBr2, BaCl2 and BaBr2 have been investigated from ambient temperature up to close to their melting points, using the neutron powder diffraction technique. Fluorite-structured SrCl2 undergoes a gradual transition to a superionic phase at 900–1100 K, characterised by an increasing concentration of anion Frenkel defects. At a temperature of 920(3) K, the tetragonal phase of SrBr2 undergoes a first-order transition to a cubic fluorite phase. This high temperature phase shows the presence of extensive disorder within the anion sublattice, which differs from that found in superionic SrCl2. BaCl2 and BaBr2 both adopt the cotunnite crystal structure under ambient conditions. BaCl2 undergoes a first-order structural transition at 917(5) K to a disordered fluorite-structured phase. The relationship between the (disordered) crystal structures and the ionic conductivity behaviour is discussed and the influence of the size of the mobile anion on the superionic behaviour is explored. 相似文献
914.
Richard Clements James R. Hester Chris D. Ling 《Journal of solid state chemistry》2011,184(8):2108-2113
Twelve members of the Ho2−yNdyZr2O7 series, prepared using conventional solid state methods, have been characterised by neutron powder diffraction. Ho2Zr2O7 has a defect fluorite structure whereas Nd2Zr2O7 is found to adopt the ordered pyrochlore structure with the composition induced fluorite-pyrochlore transformation occurring near y=1. Rietveld analysis on the neutron data for all the compositions reveals an increase in lattice parameter as a function of y across the entire series, with a small discontinuity associated with the transformation. The neutron profile results suggest that domains of pyrochlore-type initially begin to form before crystallising into a separate phase, and therefore that anion and cation ordering processes are distinct. There is a strong correlation between the extent of disorder in the anion sublattice and the x-parameter of 48f oxygen. These results point the way to a better understanding of the stability observed in pyrochlore structures. 相似文献
915.
Chandra Wahyu Purnomo Chris Salim Hirofumi Hinode 《Journal of Analytical and Applied Pyrolysis》2011,91(1):257-262
Activated carbons from bagasse fly ash (BFA) were prepared by one step chemical activation using ZnCl2 as activating agent, or combination method of chemical with CO2 physical activation (physicochemical activation). The development of porosity was studied in correlation with the method of activation, activation temperature, and also the chemical weight ratio. A typical sample by the combination method at 600 °C and weight ratio of ZnCl2:BFA = 2 exhibited micropore volume of 0.528 cc/g, mesopore volume of 0.106 cc/g and surface area of 1200 m2/g. For determining the adsorption capacity of the carbon samples in solutions, phenol and methylene blue equilibrium adsorption experiments were conducted. The properties and adsorption capacity of the synthesized activated carbons has been compared to commercial activated carbon (Norit® SX Plus). 相似文献
916.
Camille L.A. HamulaHongquan Zhang Feng LiZhixin Wang X. Chris Le Xing-Fang Li 《Trends in analytical chemistry : TRAC》2011,30(10):1587-1597
DNA aptamers specifically recognizing microbial cells and viruses have a range of analytical and therapeutic applications. This article describes recent advances in the development of aptamers targeting specific pathogens (e.g., live bacteria, whole viral particles, and virally-infected mammalian cells). Specific aptamers against pathogens have been used as affinity reagents to develop sandwich assays, to label and to image cells, to bind with cells for flow-cytometry analysis, and to act as probes for development of whole-cell biosensors. Future applications of aptamers to pathogens will benefit from recent advances in improved selection and new aptamers containing modified nucleotides, particularly slow off-rate modified aptamers (SOMAmers). 相似文献
917.
Steiner D Oostenbrink C Diederich F Zürcher M van Gunsteren WF 《Journal of computational chemistry》2011,32(9):1801-1812
An understanding at the atomic level of the driving forces of inhibitor binding to the protein plasmepsin (PM) II would be of interest to the development of drugs against malaria. To this end, three state of the art computational techniques to compute relative free energies-thermodynamic integration (TI), Hamiltonian replica-exchange (H-RE) TI, and comparison of bound versus unbound ligand energy and entropy-were applied to a protein-ligand system of PM II and several exo-3-amino-7-azabicyclo[2.2.1]heptanes and the resulting relative free energies were compared with values derived from experimental IC(50) values. For this large and flexible protein-ligand system, the simulations could not properly sample the relevant parts of the conformational space of the bound ligand, resulting in failure to reproduce the experimental data. Yet, the use of Hamiltonian replica exchange in conjunction with thermodynamic integration resulted in enhanced convergence and computational efficiency compared to standard thermodynamic integration calculations. The more approximate method of calculating only energetic and entropic contributions of the ligand in its bound and unbound states from conventional molecular dynamics (MD) simulations reproduced the major trends in the experimental binding free energies, which could be rationalized in terms of energetic and entropic characteristics of the different structural and physico-chemical properties of the protein and ligands. 相似文献
918.
Mitchell MR Reader SW Johnston KE Pickard CJ Whittle KR Ashbrook SE 《Physical chemistry chemical physics : PCCP》2011,13(2):488-497
The local structure and cation disorder in Y(2)Ti(2-x)Sn(x)O(7) pyrochlores, materials proposed for the encapsulation of lanthanide- and actinide-bearing radioactive waste, is studied using (119)Sn (I = 1/2) NMR spectroscopy. NMR provides an excellent probe of disorder, as it is sensitive to the atomic scale environment without the need for any long-range periodicity. However, the complex and overlapping spectral resonances that often result can be difficult to interpret. Here, we demonstrate how (119)Sn DFT calculations can be used to aid the spectral interpretation and assignment, confirming that Sn occupies only the six-coordinate pyrochlore B site, and that the Sn chemical shift is sensitive to the number of Sn/Ti on the neighbouring B sites. Although distinct resonances are resolved experimentally when the Ti content is low, there is significant spectral overlap for Ti-rich compositions. We establish that this is a result of two competing contributions to the Sn chemical shift; an upfield shift resulting from the incorporation of the more polarizing Ti(4+) cation onto the neighbouring B sites, and a concomitant downfield shift arising from the decrease in unit cell size. Despite the considerably easier spectral acquisition, the lower resolution in the (119)Sn spectra hinders the extraction of the detailed structural information previously obtained using (89)Y NMR. However, the spectra we obtain are consistent with a random distribution of Sn/Ti on the pyrochlore B sites. Finally, we consider whether an equilibrium structure has been achieved by investigating materials that have been annealed for different durations. 相似文献
919.
The irradiation of pure molecular oxygen (O(2)) and carbon dioxide (CO(2)) ices with 5 keV H(+) and He(+) ions was investigated experimentally to simulate the chemical processing of oxygen rich planetary and interstellar surfaces by exposure to galactic cosmic ray (GCR), solar wind, and magnetospheric particles. Deposited at 12 K under ultra-high vacuum conditions (UHV), the irradiated condensates were monitored on-line and in situ in the solid-state by Fourier transform infrared spectroscopy (FTIR), revealing the formation of ozone (O(3)) in irradiated oxygen ice; and ozone, carbon monoxide (CO), and cyclic carbon trioxide (c-CO(3)) in irradiated carbon dioxide. In addition to these irradiation products, evolution of gas-phase molecular hydrogen (H(2)), atomic helium (He) and molecular oxygen (O(2)) were identified in the subliming oxygen and carbon dioxide condensates by quadrupole mass spectrometry (QMS). Temporal abundances of the oxygen and carbon dioxide precursors and the observed molecular products were compiled over the irradiation period to develop reaction schemes unfolding in the ices. These reactions were observed to be dependent on the generation of atomic oxygen (O) by the homolytic dissociation of molecular oxygen induced by electronic, S(e), and nuclear, S(n), interaction with the impinging ions. In addition, the destruction of the ozone and carbon trioxide products back to the molecular oxygen and carbon dioxide precursors was promoted over an extended period of ion bombardment. Finally, destruction and formation yields were calculated and compared between irradiation sources (including 5 keV electrons) which showed a surprising correlation between the molecular yields (~10(-3)-10(-4) molecules eV(-1)) created by H(+) and He(+) impacts. However, energy transfer by isoenergetic, fast electrons typically generated ten times more product molecules per electron volt (~10(-2)-10(-3) molecules eV(-1)) than exposure to the ions. Implications of these findings to Solar System chemistry are also discussed. 相似文献
920.
Shim JU Patil SN Hodgkinson JT Bowden SD Spring DR Welch M Huck WT Hollfelder F Abell C 《Lab on a chip》2011,11(6):1132-1137
A microfluidic device capable of exploiting the permeability of small molecules through polydimethylsiloxane (PDMS) has been fabricated in order to control the contents of microdroplets stored in storage wells. We demonstrate that protein precipitation and crystallization can be triggered by delivery of ethanol from a reservoir channel, thus controlling the protein solubility in microdroplets. Likewise quorum sensing in bacteria was triggered by delivery of the auto-inducer N-(3-oxododecanoyl)-l-homoserine lactone (OdDHL) through the PDMS membrane of the device. 相似文献