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151.
Resonance Raman spectroscopy of red blood cells using near-infrared laser excitation 总被引:5,自引:0,他引:5
Wood BR Caspers P Puppels GJ Pandiancherri S McNaughton D 《Analytical and bioanalytical chemistry》2007,387(5):1691-1703
Resonance Raman spectra of oxygenated and deoxygenated functional erythrocytes recorded using 785 nm laser excitation are
presented. The high-quality spectra show a mixture of enhanced A1g, A2g, B1g, B2g, Eu and vinyl modes. The high sensitivity of the Raman system enabled spectra from four oxygenation and deoxygenation cycles
to be recorded with only 18 mW of power at the sample over a 60-minute period. This low power prevented photo-/thermal degradation
and negated protein denaturation leading to heme aggregation. The large database consisting of 210 spectra from the four cycles
was analyzed with principal components analysis (PCA). The PC1 loadings plot provided exquisite detail on bands associated
with the oxygenated and deoxygenated states. The enhancement of a band at 567 cm−1, observed in the spectra of oxygenated cells and the corresponding PC1 loadings plot, was assigned to the Fe–O2 stretching mode, while a band appearing at 419 cm−1 was assigned to the Fe–O–O bending mode based on previous studies. For deoxygenated cells, the enhancement of B1g modes at 785 nm excitation is consistent with vibronic coupling between band III and the Soret transition. In the case of
oxygenated cells, the enhancement of iron-axial out-of-plane modes and non-totally symmetric modes is consistent with enhancement
into the y,z-polarized transition centered at 785 nm. The enhancement of non-totally symmetric B1g modes in oxygenated cells suggests vibronic coupling between band IV and the Soret band. This study provides new insights
into the vibrational dynamics, electronic structure and resonant enhancement of heme moieties within functional erythrocytes
at near-IR excitation wavelengths.
Part of this work was first presented at SPEC 2006, Shedding New Light on Disease: Optical Diagnosis for the New Millennium, held at Heidelberg, Germany, on 20–24 May 2006. 相似文献
152.
Let M be a finite von Neumann algebra acting on a Hilbert space H and A be a transitive algebra containing M′. In this paper we prove that if A is 2-fold transitive, then A is strongly dense in B(H). This implies that if a transitive algebra containing a standard finite von Neumann algebra (in the sense of [U. Haagerup, The standard form of von Neumann algebras, Math. Scand. 37 (1975) 271-283]) is 2-fold transitive, then A is strongly dense in B(H). Non-selfadjoint algebras related to free products of finite von Neumann algebras, e.g., LFn and , are studied. Brown measures of certain operators in are explicitly computed. 相似文献
153.
Trialkylsiloxy-modified Ta(v) centers on mesoporous silica exhibit excellent selectivity for epoxide formation (>98% after 2 h) in the oxidation of cyclohexene using aqueous H2O2 as the oxidant; the modified catalysts exhibit an increased lifetime, retaining high selectivity after 6 h of reaction (>95% epoxide). 相似文献
154.
9,10-Dichlorooctafluoroanthracene (1) was synthesized from commercially available tetrafluorophthalic acid by an optimized solution-phase route. To establish 1 as a synthon for n-type organic semiconductors, the compound was reacted with phenylboronic acid under modified Suzuki-Miyaura coupling conditions to generate octafluoro-9,10-diphenylanthracene (7) in high yield. Cyclic voltammetry and X-ray crystallography indicate that 7 has a stabilized LUMO energy level and exhibits extended pi stacking, which should lead to efficient electron transport in solid-state devices. 1,2,3,4,5,6,7,8-Octafluoroanthracene (2) was also synthesized as a potential n-type building block, but suitable C-C coupling conditions for this compound were not found, and 2 could not be converted into 9,10-dibromooctafluoroanthracene or octafluoro-9,10-diiodoanthracene. 相似文献
155.
Detonation waves in trinitrotoluene 总被引:1,自引:0,他引:1
Fabry-Perot, ORVIS, and VISAR laser interferometry are used to obtain nanosecond time resolved particle velocity histories
of the free surfaces of copper and tantalum discs accelerated by detonating trinitrotoluene (TNT) charges and of the interfaces
between TNT detonation products and lithium fluoride crystals. TNT detonation reaction zone profiles are measured for self-sustaining
detonation and piston supported overdriven (supracompressed) waves. The experimental records are compared to particle velocity
histories calculated using very finely zoned meshes of the exact dimensions with the DYNA2D hydrodynamic code. The Ignition
and Growth reactive flow model, which is based on the Zeldovich-von Neumann-D?ring (ZND) theory of detonation, yields excellent
agreement with the experimental records for TNT using an unreacted von Neumann spike pressure of 25 GPa, a reaction rate law
which releases 90% of the chemical energy within 80 ns and the remaining 10% over an additional 200 ns, and a reaction product
equation of state fit to cylinder test data assuming a Chapman-Jouguet pressure of 19 GPa. The late time energy release is
attributed to diffusion controlled solid carbon particle formation.
Received 26 July 1997 / Accepted 29 December 1997 相似文献
156.
A method is developed here for doing multiple calculations of lattice sums when the lattice structure is kept fixed, while the molecular orientations or the molecules within the unit cells are altered. The approach involves a two‐step process. In the first step, a multipole expansion is factored in such a way as to separate the geometry from the multipole moments. This factorization produces a formula for generating geometry constants that uniquely define the lattice structure. A direct calculation of these geometry constants, for all but the very smallest of crystals, is computationally impractical. In the second step, an Euler summation method is introduced that allows for efficient calculation of the geometry constants. This method has a worst case computational complexity of O(( log N)2/N), where N is the number of unit cells. If the lattice sum is rapidly converging, then the computational complexity can be significantly less than N. Once the geometry constants have been calculated, calculating a lattice sum for a given molecule becomes computationally very fast. Millions of different molecular orientations or molecules can quickly be evaluated for the given lattice structure. © 2000 John Wiley & Sons, Inc. J Comput Chem 22: 208–215, 2001 相似文献
157.
D. M. Garcia S. K. Huang W. F. Stansbury 《Journal of the American Society for Mass Spectrometry》1996,7(1):59-65
Use of optimized instrument parameters that result from statistical experimentation revealed that the sensitivity of atmospheric pressure chemical ionization (APCI) liquid chromatography-mass spectrometry (LC/MS) is greater than the sensitivity of an optimized Thermabeam? LC/MS interface by about 3 orders of magnitude, when tested on aromatic compounds. APCI is one of the few LC/MS techniques in which the chromatogram is directly comparable with liquid chromatographs that use ultraviolet detection. The optimum instrument parameters for a Finnigan SSQ-7000 APCI LC/MS interface were found at low flow rates (e. g., 0. 1 mL/min), relatively low capillary heat (e. g., 225 °C), and high sheath-gas pressure (e. g., 60 lb/in2). The optimization was achieved by monitoring the responses of sensitivity, fragmentation, and cluster ion formation. The fine tuning for high sensitivity calls for a high percentage of water in the mobile phase. In contrast, a high percentage of organic content in the mobile phase is required to obtain abundant protonated molecular ions with respect to fragmentation and clustering. This is an important consideration for analyses of unknowns. 相似文献
158.
Don S. Lemons Dan Winske William Daughton Brian Albright 《Journal of computational physics》2009,228(5):1391-1403
We construct and investigate a set of stochastic differential equations that incorporate the physics of velocity-dependent small-angle Coulomb collisions among the plasma particles in a particle-in-cell simulation. Each particle is scattered stochastically from all the other particles in a simulation cell modeled as one or more Maxwellians. Total energy and momentum are conserved by linear transformation of the velocity increments. In two test simulations the proposed “particle-moment” collision algorithm performs well with time steps as large as 10% of the relaxation time – far larger than a particle-pairing collision algorithm, in which pairs of particles are scattered from one another, requires to achieve the same accuracy. 相似文献
159.
Novel chromophores formed in the solvent reactions of α-amino acids and small peptides were identified by crystal structure analysis and characterized by UV absorption. The formation of these chromophores in basic solutions was attributed to two strong driving forces—conjugation and cyclization. The discussion of possible reaction pathways could benefit the future design of α-amino acid-based chromophores. 相似文献
160.
Jon Baker Krzysztof Wolinski Massimo Malagoli Don Kinghorn Pawel Wolinski Gábor Magyarfalvi Svein Saebo Tomasz Janowski Peter Pulay 《Journal of computational chemistry》2009,30(2):317-335
This article describes the capabilities and performance of the latest release (version 4.0) of the Parallel Quantum Solutions (PQS) ab initio program package. The program was first released in 1998 and evolved from the TEXAS program package developed by Pulay and coworkers in the late 1970s. PQS was designed from the start to run on Linux‐based clusters (which at the time were just becoming popular) with all major functionality being (a) fully parallel; and (b) capable of carrying out calculations on large—by ab initio standards—molecules, our initial aim being at least 100 atoms and 1000 basis functions with only modest memory requirements. With modern hardware and recent algorithmic developments, full accuracy, high‐level calculations (DFT, MP2, CI, and Coupled‐Cluster) can be performed on systems with up to several thousand basis functions on small (4‐32 node) Linux clusters. We have also developed a graphical user interface with a model builder, job input preparation, parallel job submission, and post‐job visualization and display. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009 相似文献