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931.
Dong?Seop?LeeEmail author J.?Periaux L.?F.?Gonzalez K.?Srinivas E.?Onate 《Structural and Multidisciplinary Optimization》2012,45(3):433-450
There are many applications in aeronautical/aerospace engineering where some values of the design parameters/states cannot
be provided or determined accurately. These values can be related to the geometry (wingspan, length, angles) and or to operational
flight conditions that vary due to the presence of uncertainty parameters (Mach, angle of attack, air density and temperature,
etc.). These uncertainty design parameters cannot be ignored in engineering design and must be taken into the optimisation
task to produce more realistic and reliable solutions. In this paper, a robust/uncertainty design method with statistical
constraints is introduced to produce a set of reliable solutions which have high performance and low sensitivity. Robust design
concept coupled with Multi-Objective Evolutionary Algorithms (MOEAs) is defined by applying two statistical sampling formulas;
mean and variance/standard deviation associated with the optimisation fitness/objective functions. The methodology is based
on a canonical evolution strategy and incorporates the concepts of hierarchical topology, parallel computing and asynchronous
evaluation. It is implemented for two practical Unmanned Aerial System (UAS) design problems; the first case considers robust
multi-objective (single-disciplinary: aerodynamics) design optimisation and the second considers a robust multidisciplinary
(aero-structures) design optimisation. Numerical results show that the solutions obtained by the robust design method with
statistical constraints have a more reliable performance and sensitivity in both aerodynamics and structures when compared
to the baseline design. 相似文献
932.
Dina Had?iosmanovi? Damiano Bolzoni Pieter H. Hartel 《International Journal of Information Security》2012,11(4):231-251
SCADA (supervisory control and data acquisition) systems are used for controlling and monitoring industrial processes. We propose a methodology to systematically identify potential process-related threats in SCADA. Process-related threats take place when an attacker gains user access rights and performs actions, which look legitimate, but which are intended to disrupt the SCADA process. To detect such threats, we propose a semi-automated approach of log processing. We conduct experiments on a real-life water treatment facility. A preliminary case study suggests that our approach is effective in detecting anomalous events that might alter the regular process workflow. 相似文献
933.
James?Eves Vassili?V.?ToropovEmail author Harvey?M.?Thompson Nik?Kapur Jian?Fan Daniel?Copley Adrian?Mincher 《Structural and Multidisciplinary Optimization》2012,45(5):739-745
Supersonic jet pumps are simple devices with no moving parts, where a high velocity (primary) flow is used to pump a second
fluid. In this paper, Computational Fluid Dynamics (CFD) is combined with an optimization framework in order to develop a
tool for the rapid generation of jet pump designs. A key feature of the problem formulation is the transformation of the jet
pump design parameters in terms of geometric ratios. This approach dramatically reduces the number of unrealistic designs
covered by the Design of Experiments. Optimal Latin Hypercubes for surrogate model building and model validation points are
constructed using a permutation genetic algorithm and design points are evaluated using CFD. Surrogate models of primary and
entrained flow rates are built using a Moving Least Squares approach. A series of optimizations for various pump sizes are
performed using a genetic algorithm and Sequential Quadratic Programming, with responses calculated from the surrogates. This
approach results in a set of optimized designs, from which pumps for a wide range of flow rates can be interpolated. 相似文献
934.
Behrooz?HassaniEmail author Mostafa?Khanzadi S.?Mehdi?Tavakkoli 《Structural and Multidisciplinary Optimization》2012,45(2):223-233
The Isogeometric Analysis (IA) method is applied for structural topology optimization instead of finite elements. For this
purpose, a control point based Solid Isotropic Material with Penalization (SIMP) method is employed and the material density
is considered as a continuous function throughout the design domain and approximated by the Non-Uniform Rational B-Spline
(NURBS) basis functions. To prevent the formation of layouts with porous media, a penalization technique similar to the SIMP
method is used. For optimization an optimality criteria is derived and implemented. A few examples are presented to demonstrate
the performance of the method. It is shown that, dissimilar to the element based SIMP topology optimization, the resulted
layouts by this method are independent of the number of the discretizing control points and checkerboard free. 相似文献
935.
The ability of Lactobacillus jensenii and Streptococcus 17SB to inbhibit Escherichia coli was demonstrated. The practical application of the inhibition was examined. Possible roles for several factors in the mechanism of inhibition by Lactobacillus jensenii and Streptococcus 17SB are briefly discussed. The effects of pH reached and acids produced by starters on the growth of Escherichia coli are described. 相似文献
936.
The perovskite-type oxide PrCoO3 has been studied by means of X-ray photoelectron spectroscopy (XPS), reduction in H2 and X-ray diffraction. Two types of oxygen were detected: lattice oxygen (binding energy = 528.4 eV) and adsorbed oxygen (binding energy = 530.9 eV). The increase in relative intensity of the peak corresponding to the latter species after reduction of PrCo03 to 3e– per molecule is assigned to the formation of hydroxyl groups. Temperature-programmed reduction (TPR) results showed two reduction steps: to 1 e– per molecule (Co3.1 Co2+) at 475 to 635 K, and to 3e– per molecule (Co21 Co0) at 725 to 815 K. Reduction in the first and second steps occurs according to the contracting sphere model and the nucleation mechanism, respectively. Reduction of Co3+ to Co2+ causes minimal structural changes in the perovskite. Reduction to 3e– per molecule yielded Pr2O3 and metallic cobalt. After this reduction and reoxidation at 973 K, the perovskite structure was regained. By XPS and TPR it was shown that PrCo03 is more easily reducible than LaCo03. It is concluded that the cation in the A position of the structure plays a significant role in the bulk and surface properties of LnCo03 (Ln, lanthanide elements) oxides. 相似文献
937.
Federico Ferreres Alberto Ortiz Carmen Silva Christina Garcia-Viguera Francisco A. Tomás-Barberán Francisco Tomás-Lorente 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1992,194(2):139-143
Summary The flavonoids present in ten selected samples of La Alcarria honey with different pollen compositions have been HPLC analysed in order to establish if correlations between botanical origin and flavonoid profiles are possible. A common flavonoid pattern is observed in the different samples showing that pollen is not the main source of honey flavonoids. A close correlation between the flavonoid patterns of honey flavonoids and propolis flavonoids has been found suggesting that flavonoid analysis could be more useful in geographical origin determinations than in botanical origin studies.
Flavonoide des La-Alcarria-Honigs Eine Studie ihres botanischen Ursprungs
Zusammenfassung Die Flavonoide in Proben in Alcarria-Honig mit unterschiedlicher Pollenzusammensetzung wurden untersucht, um Kortrelationen zwischen dem botanischen Ursprung und den möglichen Flavonoiden zu finden. In den verschiedenen Proben wurde ein Flavonoid-Muster gefunden, wobei der Pollen nicht die Hauptquelle der Honigflavonoide ist. Es wurde jedoch eine enge Korrelation zwischen den Flavonoid-Mustern des Honigs und des Bienenkittharzes gefunden, was für die geographische Herkunft wichtiger ist als die botanische.相似文献
938.
de Munck J.C. Vijn P.C.M. Lopes da Silva F.H. 《IEEE transactions on bio-medical engineering》1992,39(8):791-804
The statistical properties of the EEG and the MEG are described mathematically as the result of randomly distributed dipoles. These dipoles represent the interactions of cortical neurons. For certain dipole distributions, the first- and second-order moments of the electric and magnetic fields are derived analytically. If the dipoles are in a spherical volume conductor and have no preference for any direction, the variance of a differentially measured EEG-signal is only a function of the electrode distance. In this paper, the theoretically derived variance function will be compared with EEG- and MEG-measurements. It is shown that a dipole with a fixed position and a randomly fluctuating amplitude is an adequate model for the alpha-rhythm. An expression for the covariance between the magnetic field and a differentially measured EEG-signal is derived. This covariance is considered as a function of the magnetometer position, and is compared with the measurements of Chapman et al. [23]. The theory can be used to obtain a (spatial) covariance matrix of the background noise, which occurs in evoked potential measurements. Such a covariance matrix can be used to obtain a maximum likelihood estimator of the dipole parameters in evoked potential studies, to evaluate the merits of the so-called "Laplacian derivation," and for the interpolation of electromagnetic data. 相似文献
939.
L M Iakushina Iu P Arkhapchev S I Ale?nik N V Blazheevich V A Isaeva I A Alekseeva E Iu Glinka N L Grishchenko L S Evert E I Prakhin 《Voprosy pitaniia》1992,(3):59-62
The effect of the prophylactic use of multivitamin "Undevitum" on parameters of vitamin providing of schoolchildren in Norilsk was studied. The results of the investigation showed a positive effect of the prophylactic vitamin administration on providing with vitamins of schoolchildren in Norilsk and proved the necessity of conducting mass vitamin administration to schoolchildren. 相似文献
940.
The authors discuss the results of ophthalmodynamometric tests used for the assessment of cerebro-retinal vessels reactivity following carbon dioxide baths and "peat collars". An analysis of systemic and local blood pressure in the ophthalmic artery measured with Weigelin and Lobstein technique enables to assess changes in blood pressures following a/m balneologic procedures. It was found that blood pressure does not change parallelly due to the mechanism of cerebral autoregulation. Transient decrease in blood pressure in the ophthalmic artery is produced by the dilatation of the internal carotid artery indicating a potent vasodilating action of carbon dioxide. 相似文献