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971.
972.
J. Kiener H. J. Gils H. Rebel G. Baur 《Zeitschrift für Physik A Hadrons and Nuclei》1989,334(3):359-360
The neutron coherent scattering length bc=9.26(13) fm of the lead isotope208Pb was determined by neutron interferometry. 相似文献
973.
Sydney C. K. Chu 《The Journal of the Operational Research Society》1989,40(9):771-778
This paper reports the actual implementation of a location-allocation study, which is one aspect of the overall Passive Cooling (Thailand) Project conducted in Northern Thailand since 1985. The goal has been to generate decision supports for ‘optimal’ placements of cooling facilities and the assignment of sites to these facilities as part of the post-harvest handling-chain operation of agricultural products. The basic questions addressed in this work are the issues of how many facilities to set up and where to locate them for maximum utility. Our selected approach is to use discrete location-allocation modelling, as, among other reasons, the problem at hand has a most natural network setting. Direct methods as well as efficient heuristics are examined, and sample numerical results are reported as illustrations of the continual implementation. 相似文献
974.
We study networks of coupled phase oscillators and show that
network architecture can force relations between average
frequencies of the oscillators. The main tool of our analysis is
the coupled cell theory developed by Stewart, Golubitsky, Pivato,
and Torok, which provides precise relations between network
architecture and the corresponding class of ODEs in RM and
gives conditions for the flow-invariance of certain polydiagonal
subspaces for all coupled systems with a given network
architecture. The theory generalizes the notion of fixed-point
subspaces for subgroups of network symmetries and directly extends
to networks of coupled phase oscillators. For systems of coupled phase oscillators (but not generally for ODEs in RM, where M ≥ 2), invariant polydiagonal subsets of
codimension one arise naturally and strongly restrict the network
dynamics. We say that two oscillators i and j coevolve if the polydiagonal θi = θj is flow-invariant, and show that the average frequencies of these
oscillators must be equal. Given a network architecture, it is shown that coupled cell theory
provides a direct way of testing how coevolving oscillators form
collections with closely related dynamics. We give a
generalization of these results to synchronous clusters of phase
oscillators using quotient networks, and discuss implications for
networks of spiking cells and those connected through buffers that
implement coupling dynamics. 相似文献
975.
S. M. Arabei D. V. Novik T. A. Pavich K. N. Solov’ev 《Journal of Applied Spectroscopy》2006,73(4):511-521
We have studied the fluorescence and fluorescence excitation spectra at 300 K, 77 K, and 4.2 K for silicate gel matrices colored
with meso-tetrapropylporphin by impregnation of the matrix with a solution of the pigment. Comparison of the data obtained
with the absorption spectra in acidified solutions and analysis of the low-temperature fine-structure vibronic spectra, and
also taking into account data obtained earlier for octaethylporphin in a xerogel showed formation of two cationic forms of
meso-tetrapropylporphin in the gel matrix: the short-wavelength form has a dicationic structure, while the long-wavelength form
has a monocationic structure. We have traced out the correlations of the vibrational structure in the spectra of the dicationic
form with data for the porphin dication, and we have drawn a number of conclusions concerning the normal vibrational modes
that are active in the vibronic fluorescence and absorption spectra of the studied cationic forms. Using the AM1 semiempirical
quantum chemical method, we optimized the geometry of the mesotetrapropylporphin dication: the most stable of the possible
conformers is the dication structure with saddleshaped macrocycle nonplanarity.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 453–461, July–August, 2006. 相似文献
976.
We consider a retrial queue with a finite buffer of size N, with arrivals of ordinary units and of negative units (which cancel one ordinary unit), both assumed to be Markovian arrival
processes. The service requirements are of phase type. In addition, a PHL,N bulk service discipline is assumed. This means that the units are served in groups of size at least L, where 1≤ L≤ N. If at the completion of a service fewer than L units are present at the buffer, the server switches off and waits until the buffer length reaches the threshold L. Then it switches on and initiates service for such a group of units. On the contrary, if at the completion of a service
L or more units are present at the buffer, all units enter service as a group. Units arriving when the buffer is full are not
lost, but they join a group of unsatisfied units called “orbit”. Our interest is in the continuous-time Markov chain describing
the state of the queue at arbitrary times, which constitutes a level dependent quasi-birth-and-death process. We start by
analyzing a simplified version of our queueing model, which is amenable to numerical calculation and is based on spatially
homogeneous quasi-birth-and-death processes. This leads to modified matrix-geometric formulas that reveal the basic qualitative
properties of our algorithmic approach for computing performance measures.
AMS Subject Classification: Primary 60K25 Secondary 68M20 90B22. 相似文献
977.
978.
979.
R. A. Wind P. D. Majors K. R. Minard E. J. Ackerman D. S. Daly G. R. Holtom B. D. Thrall T. J. Weber 《Applied magnetic resonance》2002,22(2):145-158
Confocal fluorescence optical microscopy and magnetic resonance microscopy are each used to study live cells in a minimally invasive way. Both techniques provide complementary information. Therefore, by examining cells simultaneously with both methodologies, more detailed information is obtained than is possible with each microscope individually. In this paper two configurations of a combined confocal and magnetic resonance microscope are described. The first configuration is capable of studying large single cells or three-dimensional cell agglomerates, whereas the second configuration is designed for the investigation of monolayers of mammalian cells. In both cases the sample compartment is part of a temperature regulated perfusion system. Images obtained with the combined system are shown forXenopus laevis oocytes, model JB6 tumor spheroids, and a single layer of Chinese hamster ovary cells. Finally, potential applications of the combined microscope are discussed. 相似文献
980.
P G Stelmachowicz D E Lewis L L Larson W Jesteadt 《The Journal of the Acoustical Society of America》1987,81(6):1881-1887
Growth-of-masking functions were obtained from 19 normal and 5 hearing-impaired listeners using a simultaneous-masking paradigm. When masker and probe frequency are identical, the slope of masking approximates 1.0 for both normal-hearing and impaired listeners. For masker frequencies less than or greater than probe frequency, the slopes for impaired listeners are shallower than those of normals. These findings are consistent with previously reported physiological data (single-fiber rate versus level and AP masking functions) for animals with induced cochlear lesions. Results are discussed in terms of a potential masking technique to estimate the growth of response in normal and impaired ears. 相似文献