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891.
Marc Renom‐Carrasco Piotr Gajewski Luca Pignataro Johannes G. deVries Umberto Piarulli Cesare Gennari Laurent Lefort 《Advanced Synthesis \u0026amp; Catalysis》2016,358(4):515-519
Herein, we report the successful transformation of a 1st generation Grubbs metathesis catalyst into an asymmetric transfer hydrogenation (ATH) catalyst. Upon addition of a chiral amine ligand, an alcohol and a base, the 1st generation Hoveyda–Grubbs catalyst ( HG‐I ) was found to promote the enantioselective reduction of acetophenone to 1‐phenylethanol. After optimizing the order of addition and the reaction conditions, the substrate scope was assessed leading to enantiomeric excesses up to 97% ee. NMR experiments were run in order to get information about the in situ‐generated ATH catalyst. Furthermore, the possibility to perform olefin metathesis and ketone transfer hydrogenation sequentially in one pot was demonstrated, and the first tandem olefin metathesis–ketone asymmetric transfer hydrogenation was carried out.
892.
Aspheric optical surfaces are often tested using diffractive optics as null elements. For precise measurements, the errors caused by the diffractive optical element must be calibrated. Recently, we reported first experimental results of a three position quasi-absolute test for rotationally invariant aspherics by using combined-diffractive optical elements (combo-DOEs). Here we investigate the effects of the DOE substrate errors on the proposed calibration procedure and present a set of criteria for designing an optimized combo-DOE. It is demonstrated that this optimized design enhances the overall consistency of the procedure. Furthermore, the rotationally varying part of the surface deviations is compared with the rotationally varying deviations obtained by an N-position averaging procedure and is found to be in good agreement. 相似文献
893.
894.
Hulsken B Van Hameren R Gerritsen JW Khoury T Thordarson P Crossley MJ Rowan AE Nolte RJ Elemans JA Speller S 《Nature nanotechnology》2007,2(5):285-289
Many chemical reactions are catalysed by metal complexes, and insight into their mechanisms is essential for the design of future catalysts. A variety of conventional spectroscopic techniques are available for the study of reaction mechanisms at the ensemble level, and, only recently, fluorescence microscopy techniques have been applied to monitor single chemical reactions carried out on crystal faces and by enzymes. With scanning tunnelling microscopy (STM) it has become possible to obtain, during chemical reactions, spatial information at the atomic level. The majority of these STM studies have been carried out under ultrahigh vacuum, far removed from conditions encountered in laboratory processes. Here we report the single-molecule imaging of oxidation catalysis by monitoring, with STM, individual manganese porphyrin catalysts, in real time, at a liquid-solid interface. It is found that the oxygen atoms from an O2 molecule are bound to adjacent porphyrin catalysts on the surface before their incorporation into an alkene substrate. 相似文献
895.
Claudia Wittke Johannes Mayer Franz Schweiggert 《IEEE transactions on information technology in biomedicine》2007,11(4):406-414
Gleason grading is a common method used by pathologists to determine the aggressivity of prostate cancer on the basis of histological slide preparations. The advantage of this grading system is a good correlation with the biological behavior of the tumor, while its drawback is the subjectivity underlying the judgements of pathologists. Therefore, an automation of Gleason grading would be desirable. In this paper, we examined 780 digitized grayscale images of 78 different cases, which were split into a training and a test set. We developed two methods based on combinations of morphological characteristics like area fraction, line length, and Euler number to classify into the categories "Gleason score < 7" and "Gleason score > or = 7." In particular, the distinction between these two classes has great impact on the prognosis of patients. The agreement of each method with visual diagnosis was 87.18% and 92.31% within the training set and 66.67% and 64.10% within the test set, respectively. 相似文献
896.
897.
898.
Nico Scheerlinck Pieter Verboven Johannes D. Stigter Josse De Baerdemaeker Jan F. Van Impe Bart M. Nicolai 《Numerical Heat Transfer, Part B: Fundamentals》2013,63(3):309-330
A first-order perturbation algorithm for the computation of mean values and variances of transient temperature and moisture fields during coupled heat and mass transfer problems with random field parameters has been developed and implemented. The algorithm is based on the Galerkin finite-element discretization of Luikov's heat and mass transfer equations for capillary porous bodies and is computationally less demanding than the Monte Carlo method. The algorithm has been programmed in MATLAB and applied to a published test case of a drying process for soybean kernels. The simulations indicate that the stochastic fluctuations of the thermophysical properties and the process conditions may cause a considerable level of uncertainty in the predicted temperatures and moisture contents inside the product. 相似文献
899.
Dr. mont. Yuriy Lytvynyuk Johannes Schenk Martin Hiebler Herbert Mizelli Axel Sormann 《BHM Berg- und Hüttenm?nnische Monatshefte》2013,158(11):457-458
A thermodynamic and kinetic model of the converter steelmaking process was developed allowing the analysis of the influence of the technological parameters, such as the amount and addition time of a charge material on the chemical composition of the crude steel. The process of the manganese ore addition to the converter to increase the final content of manganese in the crude steel was simulated. The optimal technological parameters for the enhancement of manganese yield were determined. 相似文献
900.
Bernhard Wagner Shea Fen Cheong Thomas Brinz Johannes Khinast 《Drug development and industrial pharmacy》2013,39(9):1523-1536
The aim of this work was to investigate the mean fill weight control of a continuous capsule-filling process, whether it is possible to derive controller settings from an appendant process model. To that end, a system composed out of fully automated capsule filler and an online gravimetric scale was used to control the filled weight. This setup allows to examine challenges associated with continuous manufacturing processes, such as variations in the amount of active pharmaceutical ingredient (API) in the mixture due to fluctuations of the feeders or due to altered excipient batch qualities. Two types of controllers were investigated: a feedback control and a combination of feedback and feedforward control. Although both of those are common in the industry, determining the optimal parameter settings remains an issue. In this study, we developed a method to derive the control parameters based on process models in order to obtain optimal control for each filled product. Determined via rapid automated process development (RAPD), this method is an effective and fast way of determining control parameters. The method allowed us to optimize the weight control for three pharmaceutical excipients. By conducting experiments, we verified the feasibility of the proposed method and studied the dynamics of the controlled system. Our work provides important basic data on how capsule filler can be implemented into continuous manufacturing systems. 相似文献