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861.
Measuring knowledge transfer between fields of science 总被引:4,自引:2,他引:2
Rinia Ed J. van Leeuwen Thed N. Bruins Eppo E. W. van Vuren Hendrik G. van Raan Anthony F. J. 《Scientometrics》2002,54(3):347-362
In this paper we report on the results of an exploratory study of knowledge exchange between disciplines and subfields of
science, based on bibliometric methods. The goal of this analysis is twofold. Firstly, we consider knowledge exchange between
disciplines at a global level, by analysing cross-disciplinary citations in journal articles, based on the world publication
output in 1999. Among others a central position of the Basic Life Sciences within the Life Sciences and of Physics within
the Exact Sciences is shown. Limitations of analyses of interdisciplinary impact at the journal level are discussed. A second
topic is a discussion of measures which may be used to quantify the rate of knowledge transfer between fields and the importance
of work in a given field or for other disciplines. Two measures are applied, which appear to be proper indicators of impact
of research on other fields. These indicators of interdisciplinary impact may be applied at other institutional levels as
well.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
862.
S. F. Pankina V. V. Chebotaev V. A. Il'ichev V. P. Petrukhin I. V. Kolybin 《Soil Mechanics and Foundation Engineering》1998,35(2):55-60
A general concept is cited for the design of an underground transportation tunnel in the Lefortovo District. Attention is
focused on problems of the tunnel's layout in plan and profile, the layout of sections, and selection of the driving technology.
Results are presented for the numerical modeling of variations in the stress—strain state of the soil mass, which are associated
with the tunnel's installation. A set of measures to protect existing architectural monuments is proposed.
Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 17–21, March–April, 1998. 相似文献
863.
Podcameni A. Conrado L.F.M. Carvalho M.C.R. Mosso M.M. 《Broadcasting, IEEE Transactions on》1998,44(4):436-444
It is often desirable to increase the capacity and the covered distance in lightwave TV systems. For doing so, the conventional CATV channel set-usually placed within the 50 to 550 MHz frequency range-may be up-shifted, by means of a subcarrier, to a low microwave frequency range, typically located at 2 GHz. Next, this shifted spectrum directly modulates a laser diode, in the analog AM mode. It is shown that this up-shift procedure may dislodge a number of nonlinear distortion components from the useful TV band. Consequently, the system effective optical modulation index may be increased, allowing for an expansion in the channel capacity or covered distance. This enlarged capacity or distance may compensate for the modest price increase concerning the up-shift equipment. All the performance evaluations presented here were carried out with a rigorous numerical model, and assuming the lightwave systems used the economical AM-VSB format 相似文献
864.
Punt J.B. Sparreboom D. Brouwer F. Prasad R. 《Vehicular Technology, IEEE Transactions on》1998,47(4):1302-1313
Dynamic channel selection (DCS) is an algorithm for flexible resource sharing in mobile radio systems. The digital enhanced cordless telecommunications (DECT) standard implements a version of DCS based on time as well as frequency multiplexing. In this paper, mathematical models are developed to evaluate the probabilities of channel availability, desired carrier power, and the carrier-to-interference ratio (CIR) for a constant traffic load. These results can be used to compute the call setup blocking probability. The models reported in this study are based on a decentralized DCS according to the DECT standard specifications. The results show that blocking due to availability of a channel (resource blocking), not interference blocking, generally is the most important factor in overall call blocking. Furthermore, it is seen that resource blocking is sensitive to the implementation of portable sets. Also, with homogeneous static traffic, this type of DCS ran be as good as fixed channel allocation (FCA) with respect to resource blocking 相似文献
865.
Pantic-Tanner Z. Scott Savage J. Tanner D.R. Peterson A.F. 《Microwave Theory and Techniques》1998,46(2):178-184
The finite-element method (FEM) exhibits a reduced convergence rate when used for the analysis of geometries containing sharp edges where the electromagnetic field is singular. The convergence of the method can be-improved by introducing singular elements that model analytically predicted singular behavior. A number of authors have developed singular elements that are compatible with the scalar FEM. In this paper, we propose a new singular element that is compatible with edge-based vector finite elements and can cope with any order of singularity while preserving the sparsity of the FEM equations. Edge-based singular elements more correctly model singular fields and thus require fewer unknowns, while avoiding the introduction of spurious modes in the numerical solution. Numerical results verify that the convergence of the FEM is significantly improved 相似文献
866.
867.
E. V. Astrova V. V. Ratnikov R. F. Vitman A. A. Lebedev A. D. Remenyuk Yu. V. Rud’ 《Semiconductors》1997,31(10):1084-1090
The results of an investigation of layers of porous silicon (PS), which was obtained by electrochemical etching of p-Si under different illumination conditions — natural light, incandescent light, and light from a mercury lamp with and without
a filter — are reported. The structure of the layers was studied by double-crystal x-ray diffractometry, the composition was
monitored by means of the IR absorption spectra, and the radiative properties were monitored according to the photoluminescence
(PL) spectra. It was established that electrochemical etching under illumination produces PS with a higher porosity and more
intense PL whose maximum is shifted into the short-wavelength region. These changes are accompanied by a large disordering
of the structure and an increase in the oxygen content in the layer. It is concluded that illumination accelerates the chemical
interaction of PS with the electrolyte due to oxidation. High-porosity porous silicon stored in air exhibits quenching of
PL. Conversely, PL is excited in layers with a lower porosity. Aging of PS is characterized by an increase in the microdeformation
of the layers, a decrease in the crystallite sizes with a partial loss of coherence between the crystallites and the substrate,
and an increase in the fraction of the amorphous phase.
Fiz. Tekh. Poluprovodn. 31, 1261–1268 (October 1997) 相似文献
868.
869.
870.
Tsuji M. Shigesawa H. Frezza F. Lampariello P. Oliner A.A. 《Antennas and Propagation, IEEE Transactions on》1998,46(7):1047-1055
For pt.II ibid., vol.46, no.7, p.1042-46. The article describes the measurements that verify the validity of the theoretical expressions for this new type of antenna. Measurements were made both at millimeter wavelengths (40 to 60 GHz) and in the X-band (8 to 12 GHz) frequency range and of two different quantities: the propagation wavenumbers β and α and radiation patterns. Comparisons were made with numerical values obtained from the theoretical expressions derived in parts I and II and very good agreement was found in all cases 相似文献