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991.
Electronic equivalents of traditional cash payment systems are being launched worldwide. Electronic cash can combine the benefits of traditional cash with those of payment by debit and credit card, while circumventing both their shortcomings. As with traditional cash, electronic cash should have high acceptability and be suitable for low value payment from person to person. With the possible exception of online payment platforms such as the Internet, it is preferred that payments be verifiable offline, without the bank's involvement, for reasons of cost effectiveness and speed. To facilitate electronic cash payments over the phone and the Internet, physical proximity of payer and payee should not be necessary. Moreover, electronic cash should offer privacy of payments. In particular, payments by an honest payer should be untraceable, and information about transaction content should remain privy to payer and payee. Yet a payer ought to always be able to trace the payee; traceability suits electronic cash and is as open to extortion, money laundering, and bribery as a check or wire transfer. Lastly, as with payments by debit and credit card, electronic cash should be convenient to store and transport, while protecting users against loss, theft, and accidental destruction 相似文献
992.
Wavelength selection for low-saturation pulse oximetry 总被引:1,自引:0,他引:1
Mannheimer P.D. Cascini J.R. Fein M.E. Nierlich S.L. 《IEEE transactions on bio-medical engineering》1997,44(3):148-158
Conventional pulse oximeters are accurate at high oxygen saturation under a variety of physiological conditions but show worsening accuracy at lower saturation (below 70%). Numerical modeling suggests that sensors fabricated with 735 and 890 nm emitters should read more accurately at low saturation under a variety of conditions than sensors made with conventionally used 660 and 900 nm band emitters. Recent animal testing confirms this expectation. It is postulated that the most repeatable and stable accuracy of the pulse oximeter occurs when the fractional change in photon path lengths due to perturbations in the tissue (relative to the conditions present during system calibration) is equivalent at the two wavelengths. Additionally, the penetration depth (and/or breadth) of the probing light needs to be well matched at the two wavelengths in order to minimize the effects of tissue heterogeneity. At high saturation these conditions are optimally met with 660 and 900 nm band emitters, while at low saturation 735 and 890 nm provide better performance 相似文献
993.
Yu. N. Denisyuk N. M. Ganzherli I. M. Maurer S. A. Pisarevskaya 《Technical Physics Letters》1997,23(4):279-280
A thick-layer light-sensitive material consisting of glycerin-containing bichromated gelatin has been prepared and used to
record real-time volume holograms with 0.44 μm helium-cadmium laser radiation. The thickness of the layers is 400–600 μm.
The holographic sensitivity of the material is 1 J/cm2. The highest diffraction efficiency of holograms recorded using a symmetric system with parallel beams is 32%.
Pis’ma Zh. Tekh. Fiz. 23, 62–65 (April 12, 1997) 相似文献
994.
995.
The perfectly matched layer for use with the finite-difference time-domain method is adapted to our transmission-line matrix simulation as what we call a heaviside absorbing layer (HAL). It is shown that the reflection coefficient for the wave incident on a HAL is less than that of the wave incident on a matched-load termination at all angles of incidence. Furthermore, the dispersion relation of a transmission-line matrix mesh of a symmetrical condensed node with both electric and magnetic loss stubs is derived. It provides guidance on how to choose the losses of HAL and other simulation parameters properly 相似文献
996.
Space diversity reception and forward-error correction coding are powerful techniques to combat multipath fading encountered in mobile radio communications. In this paper, we analyze the performance of a discrete-time switched diversity system using trellis-coded modulation multiple phase-shift keying (TCM-MPSK) on slow, nonselective correlated Nakagami (1960) fading channels. Analytical upper bounds using the transfer function bounding technique are obtained and illustrated by several numerical examples. A simple integral expression for calculating the exact pairwise error probability is presented. The use of optimum adaptive and fixed switching thresholds is considered. Monte Carlo simulation results, which are more indicative of the exact system performance, are also given 相似文献
997.
A new method based on a two-wire line has been developed for noncontact diagnostics of a low-temperature plasma and its fluxes
in channels with complex profiles. This method provides good spatial and time resolution.
Pis’ma Zh. Tekh. Fiz. 23, 1–7 (July 26, 1997) 相似文献
998.
Valenzuela R.A. Landron O. Jacobs D.L. 《Vehicular Technology, IEEE Transactions on》1997,46(1):203-212
We explore techniques for the measurement of local mean signal strength at 900 MHz and 2 GHz. In particular, we characterize the impact of transmitter and receiver antenna rotation on the estimated local mean. Then, we explore the collection of high resolution data while moving along a linear trajectory and using linear averaging techniques to estimate the local mean. With this information, the best measurement techniques can be chosen depending on the required speed versus accuracy tradeoff. Finally, we use a ray tracing propagation model to evaluate different methods of calculating the local mean signal strength for indoor environments 相似文献
999.
X. Wang S. B. Lambert 《Fatigue & Fracture of Engineering Materials & Structures》1997,20(12):1637-1655
Abstract— A Fourier series approach is proposed to calculate stress intensity factors using weight functions for semi-elliptical surface cracks in flat plates subjected to two-dimensional stress distributions. The weight functions were derived from reference stress intensity factors obtained by three-dimensional finite element analyses. The close form weight functions derived are suitable for the calculation of stress intensity factors for semi-elliptical surface cracks in flat plates under two-dimensional stress distributions with the crack aspect ratio in the range of 0.1 ≤ a/c ≤ 1 and relative depth in the range of 0 ≤ a/t ≤ 0.8. Solutions were verified using several two-dimensional non-linear stress distributions; the maximum difference being 6%. 相似文献
1000.
A transformational approach for proving termination of parallel logic programs such as GHC programs is proposed. A transformation
from GHC programs to term rewriting systems is developed; it exploits the fact that unifications in GHC-resolution correspond
to matchings. The termination of a GHC program for a class of queries is implied by the termination of the resulting rewrite
system. This approach facilitates the applicability of a wide range of termination techniques developed for rewrite systems
in proving termination of GHC programs. The method consists of three steps: (a) deriving moding information from a given GHC
program, (b) transforming the GHC program into a term rewriting system using the moding information, and finally (c) proving
termination of the resulting rewrite system. Using this method, the termination of many benchmark GHC programs such as quick-sort,
merge-sort, merge, split, fair-split and append, etc., can be proved.
This is a revised and extended version of Ref. 12). The work was partially supported by the NSF Indo-US grant INT-9416687
Kapur was partially supported by NSF Grant nos. CCR-8906678 and INT-9014074.
M. R. K. Krishna Rao, Ph.D.: He currently works as a senior research fellow at Griffith University, Brisbane, Australia. His current interests are in
the areas of logic programming, modular aspects and noncopying implementations of term rewriting, learning logic programs
from examples and conuterexamples and dynamics of mental states in rational agent architectures. He received his Ph.D in computer
science from Tata Institute of Fundamental Research (TIFR), Bombay in 1993 and worked at TIFR and Max Planck Institut für
Informatik, Saarbrücken until January 1997.
Deepak Kapur, Ph.D.: He currently works as a professor at the State University of New York at Albany. His research interests are in the areas
of automated reasoning, term rewriting, constraint solving, algebraic and geometric reasoning and its applications in computer
vision, symbolic computation, formal methods, specification and verification. He obtained his Ph.D. in Computer Science from
MIT in 1980. He worked at General Electric Corporate Research and Development until 1987. Prof. Kapur is the editor-in-chief
of the Journal of Automated Reasoning. He also serves on the editorial boards of Journal of Logic Programming, Journal on
Constraints, and Journal of Applicable Algebra in Engineering, Communication and Computer Science.
R. K. Shyamasundar, Ph.D.: He currently works as a professor at Tata Institute of Fundamental Research (TIFR), Bombay. His current intersts are in
the areas of logic programming, reactive and real time programming, constraint solving, formal methods, specification and
verification. He received his Ph.D in computer science from Indian Institute of Science, Bangalore in 1975 and has been a
faculty member at Tata Institute of Fundamental Research since then. He has been a visiting/regular faculty member at Technological
University of Eindhoven, University of Utrecht, IBM TJ Watson Research Centre, Pennsylvania State University, University of
Illinois at Urbana-Champaign, INRIA and ENSMP, France. He has served on (and chaired) Program Committees of many International
Conferences and has been on the Editorial Committees. 相似文献