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931.
Christina Allmeling Kerstin Reimers‐Fadhlaoui Peter M. Vogt 《Chemie in Unserer Zeit》2007,41(6):428-434
The experimental data show that the production of artificial nerve grafts with spider silk is a potential alternative therapy. The biologically favourable properties of the fibres from the spider Nephila clavipes should be used in human nerve reconstruction. The biological fibres promote the proliferation of cells. They are immunologically tolerated and not rejected. The muscle attraction line is kept intact which prevents muscle degeneration to a large extent. The spider fibres accelerate the migration of peripheral schwann cells into the nerve construct and promote the alignment of the nerve cells. For surgical interventions the biomechanical stability of spider silk and the composition from essential amino acids make the spider silk fibres interesting as a matrix for the cellular regeneration and in particular as a guiding structure for nerve regeneration. 相似文献
932.
S.R. Klein J. Nystrand R. Vogt 《The European Physical Journal C - Particles and Fields》2001,21(3):563-566
In relativistic heavy ion collisions, top quarks can be produced by photon-gluon fusion when a photon from the Weizs?cker-Williams
virtual photon field of one nucleus interacts with a gluon in the other nucleus. Photoproduction with heavy ions at the Large
Hadron Collider (LHC) will be the first accessible non-hadronic top production channel. We calculate the photoproduction cross sections, pair mass and top quark rapidity distributions in peripheral lead-lead and oxygen-oxygen
collisions. The cross sections are sensitive to the top quark charge and the large- gluon distribution in the nucleus. We find a cross section of 15 pb in oxygen-oxygen collisions, leading to 210 pairs in
a one month ( s) LHC run. In pA collisions, the rate is higher, 1100 pairs per month for pO. A comparison of the AA and pA data might allow for a study of gluon shadowing at high Q
.
Received: 18 May 2001 / Revised version: 13 June 2001 / Published online: 24 August 2001 相似文献
933.
High pressure powder diffraction experiments were carried out on the aluminate sodalite Sr8[Al12O24] · (CrO4)2 using a miniature clamped cell with neutron radiation at the ILL and a diamond anvil cell with synchrotron radiation at Hasylab/Desy. The results of both experiments agree well. Lattice parameters were determined up to a pressure of 7.2 GPa. The average linear compressibility amounts to 4.3 · 10−3 GPa−1, which corresponds to a linear bulk modulus of 233 GPa. The observation of superstructure reflections could be related to two new phase transitions. The first one occurs between 0.37 and 0.5 GPa, the second one at about 2.0 GPa. A final measurement at ambient pressure revealed the reversible character of the pressure induced phase transitions. 相似文献
934.
The large surface area of barks from many tree species enables the effective accumulation of pollutants. Therefore, the analysis
of bark material will provide useful information about the degree of pollution of a certain region. The determination of main,
minor, and trace elements (Al, Ca, Cd, Ce, Cr, Cu, Fe, Mn, P, Pb, S, Ti and Zn) in bark was performed with an Nd:YAG laser
coupled to an ICP-MS system. Bark standards for the calibration by laser ablation ICP-MS were prepared from different bark
layers which differ for some relevant elements in concentrations. Four digestion procedures for the decomposition of the standard
pellets, the numbers of laser shots per sample and of samples per region necessary have been investigated. Representative
results were obtained for 5 or more samples taken from different individuals of one species of a sampling area and the averaged
element concentrations of 10 separately placed laser shots for each sample. Laser ablation ICP-MS was applied for the characterization
of real bark samples from different regions with high and low pollution burden. It was shown that the method is well suited
to characterize different degrees of environmental impact. Anthropogenic sources were responsible for the higher concentrations
of most of the elements under investigation.
Received: 26 April 1999 / Revised: 24 August 1999 / /Accepted: 28 August 1999 相似文献
935.
936.
937.
Matthias Westerhausen Christian Gückel Holger Piotrowski Martin Vogt 《无机化学与普通化学杂志》2002,628(4):735-740
Metalation of Triisopropylsilylarsane with Bis(tetrahydrofuran)calcium‐bis[tris(trimethylsilylmethyl)zincate] The transmetalation of bis(trimethylsilylmethyl)zinc with distilled calcium in THF yields bis(tetrahydrofuran)calcium bis[tris‐(trimethylsilylmethyl)zincate] ( 1 ). The trialkylzincate anion appears as a bidentate ligand with Ca‐C‐Zn three‐center‐bonds. The CaC bond lengths show values of 265.5(2) and 271.7(2) pm. The metalation of triisopropylsilylarsane gives tetrakis(tetrahydrofuran)calcium [1, 3‐bis(triisopropylsilylarsanyl)‐2, 4‐bis(triisopropylsilyl)‐1, 3‐dizinca‐2, 4‐diarsacyclobutane‐2, 4‐diide] ( 2 ). The central moiety is a sligthly distorted trigonal As2CaZn2 bipyramid with the arsenic atoms in apical positions. The mean Ca‐As bond lengths lie with a mean value of 291.4 pm in the charakteristic region for calcium bis‐(arsanides). 相似文献
938.
The LHCb Collaboration has measured the doubly charmed baryon,■^++cc(ucc),through two different decay channels[1,2]in p+p collisions at center-of-mass energies of 7,8 and 13 TeV.While they have performed similar searches for the doubly charmed baryon ■^+cc(dcc),it has not yet been observed by LHCb[3].However,the fixed-target experiment,SELEX,at Fermilab,reported the observation of the ■^+cc in two different decay channels with a 600 GeV charged hyperon beam[4,5].The beam was composed of an admixture of π^±,p,p components as well as the Σ^- hyperon.Much discussion has arisen over the fact that the fixed-target observations have not been easily reproduced by the collider experiments at higher energies,where one might have expected the production rates to be much higher due to the orders of magnitude increase in the center of mass energy with LHCb. 相似文献
939.
Larissa Bessler Lea-Marie Vogt Marc Lander Dr. Christina Dal Magro Dr. Patrick Keller Dr. Jonas Kühlborn Dr. Christopher J. Kampf Prof. Dr. Till Opatz Prof. Dr. Mark Helm 《Angewandte Chemie (International ed. in English)》2023,62(11):e202217128
The fields of RNA modification and RNA damage both exhibit a plethora of non-canonical nucleoside structures. While RNA modifications have evolved to improve RNA function, the term RNA damage implies detrimental effects. Based on stable isotope labelling and mass spectrometry, we report the identification and characterisation of 2-methylthio-1,N6-ethenoadenosine (ms2ϵA), which is related to 1,N6-ethenoadenine, a lesion resulting from exposure of nucleic acids to alkylating chemicals in vivo. In contrast, a sophisticated isoprene labelling scheme revealed that ms2ϵA biogenesis involves cleavage of a prenyl moiety in the known transfer RNA (tRNA) modification 2-methylthio-N6-isopentenyladenosine (ms2i6A). The relative abundance of ms2ϵA in tRNAs from translating ribosomes suggests reduced function in comparison to its parent RNA modification, establishing the nature of the new structure in a newly perceived overlap of the two previously separate fields, namely an RNA modification damage. 相似文献
940.
C. Ascheron R. Flagmeyer G. Otto J. Vogt H. U. Frey 《Crystal Research and Technology》1987,22(12):1497-1503
On GaP single crystals bombarded with 0.3 MeV and 1.0 MeV protons the fluence and depth dependences of radiation damage are studied by means of particle induced X-ray emission spectrometry under chaneling conditions (PIXE-C) and the Rutherford backscattering/channeling technique (RBS-C). It is demonstrated that PIXE-C is suitable to study depth profiles of damage density by the combination with the bevelling technique. 相似文献