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Supported metal catalysts, particularly noble metals supported on SiO2, have attracted considerable attention due to the importance of the silica–metal interface in heterogeneous catalysis and in electronic device fabrication. Several important issues, e.g., the stability of the metal–oxide interface at working temperatures and pressures, are not well-understood. In this review, the present status of our understanding of the metal–silica interface is reviewed. Recent results of model studies in our laboratories on Pd/SiO2/Mo(1 1 2) using LEED, AES and STM are reported. In this work, epitaxial, ultrathin, well-ordered SiO2 films were grown on a Mo(1 1 2) substrate to circumvent complications that frequently arise from the silica–silicon interface present in silica thin films grown on silicon. 相似文献
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The space-time distribution of the basic kinetic parameters of a plasma is experimentally determined under conditions of expansion of plasma clusters and jets into vacuum. It is demonstrated that the dynamics and structure of plasmoids injected by pulsed erosion plasma accelerators of the electrothermal type are characterized by two successive stages or two modes of acceleration, namely, the Joule heating of electrons in the initial region of the path and the collisionless expansion of rarefied plasma. 相似文献
5.
VK Tzitzios V Georgakilas TN Angelidis 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(6):699-704
A study of nitrous oxide (N2O) reduction with methane (CH4) and propene (C3H6) in the presence of oxygen (5%) over Ag/Al2O3, Rh/Al2O3 and Ag–Rh/Al2O3 catalysts, with Ag and Rh loadings of 5 wt% and 0.05 wt% respectively, has been performed. From the results, it was observed that the Ag–Rh bimetallic catalyst was the most active for both nitrous oxide removal (more than 95%) and hydrocarbon oxidation. This high activity seems to be connected with a synergistic effect between Ag and Rh. The findings from X‐ray diffraction and X‐ray photoelectron spectroscopy studies showed also, that there were no strong interactions (eg alloying) between Ag and Rh. Copyright © 2005 Society of Chemical Industry 相似文献
6.
A seed-growth method has been applied to synthesize gold (Au) and Au-silver (Ag) bimetallic nanoparticles (NP) by using 12-3-12, a cationic Gemini surfactant, as a capping agent as well as micellar template. A systematic increase in the [12-3-12] from pre- to post-micellar region (up to 5 times the critical micelle concentration, cmc) produces Au NP from spherical to large plate like structures. Keeping [12-3-12] constant (equal to 1 / 2 cmc) and increasing ascorbic acid (AA) concentration lead to the formation of core shell type Au-Ag bimetallic NP. At maximum AA concentration (i.e. [AA] = 5.6 mM), fused bimetallic Au-Ag NP are obtained. The anisotropic growth of such materials is a key factor for various applications in nanotechnology. 相似文献
7.
Xiao-Ying Wang Jonathan M. Garibaldi Benjamin Bird Michael W. George 《Applied Intelligence》2007,27(3):237-248
Recently Fourier Transform Infrared (FTIR) spectroscopic imaging has been used as a tool to detect the changes in cellular
composition that may reflect the onset of a disease. This approach has been investigated as a mean of monitoring the change
of the biochemical composition of cells and providing a diagnostic tool for various human cancers and other diseases. The
discrimination between different types of tissue based upon spectroscopic data is often achieved using various multivariate
clustering techniques. However, the number of clusters is a common unknown feature for the clustering methods, such as hierarchical
cluster analysis, k-means and fuzzy c-means. In this study, we apply a FCM based clustering algorithm to obtain the best number
of clusters as given by the minimum validity index value. This often results in an excessive number of clusters being created
due to the complexity of this biochemical system. A novel method to automatically merge clusters was developed to try to address
this problem. Three lymph node tissue sections were examined to evaluate our new method. These results showed that this approach
can merge the clusters which have similar biochemistry. Consequently, the overall algorithm automatically identifies clusters
that accurately match the main tissue types that are independently determined by the clinician. 相似文献
8.
Hydrothermal process was applied to synthesize zinc oxide nanocrystals. X-ray powder diffraction and scanning electron microscopy were used to analyze the crystal structure and surface morphology. XRD pattern analysis showed that the ZnO clusters are single hexagonal phase of wurtzite structure (space group P63 mc) with no impurity of Zn and Zn(OH)2. Also, SEM images revealed that the size of a single ZnO crystal is between 200-500 nm in diameter and 2-5 μm in length. The influence of potassium iodide (KI) as a surfactant on the crystallinity of ZnO has been investigated. 相似文献
9.
Fadwa T. Eljack Ahmed F. Abdelhady Mario R. Eden Frederico B. Gabriel Xiaoyun Qin Mahmoud M. El-Halwagi 《Computers & Chemical Engineering》2005,29(11-12):2304
Decoupling the constitutive equations from the balance and constraint equations allows for reformulating a conventional forward problem into two reverse problems. The first reverse problem is the reverse of a simulation problem, where the process model is solved in terms of the constitutive (synthesis/design) variables instead of the process variables, thus providing the synthesis/design targets. The second reverse problem (reverse property prediction) solves the constitutive equations to identify unit operations, operating conditions and/or products by matching the synthesis/design targets. Visualization of the problem is achieved by employing recently developed property clustering techniques, which allows a high-dimensional problem to be visualized in two or three dimensions. The clusters by definition satisfy intra-stream and inter-stream conservation through linear “mixing” rules, which allows for the development of consistent additive rules along with their ternary representation. 相似文献
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