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排序方式: 共有648条查询结果,搜索用时 15 毫秒
41.
Response surface methods have been applied to the reliability analysis of laterally loaded piles. Beam elements and a series of discrete springs are used to model the pile–soil system. The pile head displacement and the maximum bending moment in the piles are used as the performance criteria in this study. It is shown in the illustrative example that the CDF and PDF curves of the pile head displacement and the maximum bending moment in the pile obtained from the proposed methods are in good agreement with Monte Carlo simulation. The failure probabilities of the pile under specified performance criteria, the probabilistic responses of the pile-soil system, and the effect of pile-soil parameters to the failure probability of the pile are also studied. 相似文献
42.
The chain entanglement states in high density, linear low density, and low density polyethylenes (HDPE, LLDPE, and LDPE) have been modified by recovering the polymers from solutions in trichlorobenzene (TCB) and p-xylene. In the thermodynamically good solvent, TCB, the entanglement density is assumed to be sharply reduced, a condition which is carried over to the corresponding solids. These display transient, but large increments in tensile moduli, slight changes in stress at rupture, and decreases in dynamic mechanical parameters and in elongation at rupture. Scanning calorimetry also shows these solids to have reduced crystallinity. Much smaller property modifications are noted in corresponding samples recovered from p-xylene. This liquid is a poorer solvent, particularly for HDPE and LLDPE. The results indicate that property modifications due to deliberate changes in the entanglement states of the polymers are a general phenomenon in the polyethylenes, and the magnitude of property changes depends on parameters of the molecular weight distribution. Chain branching does not seem to be a leading factor in the sensitivity of properties to modifications in the entanglement states. The property modifications produced by the present solution treatments are viewed as guides to the magnitude and duration of shear refining effects to be expected in HDPE, LLDPE, and LDPE polymers. 相似文献
43.
Differences in the rheology and surface chemistry of kaolin clay slurries: The source of the variations 总被引:1,自引:0,他引:1
Kaolinite clays from two sources were found to display different rheological and electrokinetic behaviour despite having similar mineral composition. This difference is mainly due to the surface chemistry at the edges of the clay particles. Making the edge surface chemistry similar with an adsorbed small anionic additive such as citrate, produced a similar yield stress-pH behaviour for the different kaolin clay slurries. Heterogeneous attraction between positively charged edges and negatively charged faces of the clay particles is responsible for the yield stress behaviour of the clay slurry. However, the different points of zero charge of the edge caused the clay slurries to display different yield stress-pH behaviour. Adsorption of anionic citrate on negatively charged kaolin clay particles is reflected in a significant increase in the magnitude of the negative zeta potential. The adsorption is likely to be on the edge of the clay particles. Adsorbed citrate generally reduces or eliminates heterogeneous charge attraction leading to a much denser sediment being formed in the kaolin slurries with a coarser particle size distribution. 相似文献
44.
Nagalingam Saravanan Geok Bee Teh Samuel Yong Peen Yap Kar Mun Cheong 《Journal of Materials Science: Materials in Electronics》2008,19(12):1206-1208
ZnS nanoparticles were successfully synthesized by reflux under an alkaline medium. The nanoparticles were characterized by
using X-Ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical
properties of ZnS nanoparticles were examined by photoluminescence (PL) spectrum. The result shows that the as-synthesized
ZnS nanoparticles had a cubic phase. SEM image shows that ZnS nanoparticles are basically in spherical shape and are homogeneous.
The particle size was found to be in the range of 18 nm. 相似文献
45.
This article presents a variational approach for the analysis of downdrag forces of pile groups undergoing soil downward movement. The theoretical load‐transfer curves are employed to describe the soil load‐displacement relationship. A soil with stiffness varying with depth and with stiffer end‐bearing stratum at the pile toe can be easily treated using the present method. The validity of the present method is demonstrated through comparison with existing theoretical solutions and field measurements. 相似文献
46.
Sue‐Siang Teh Rajeev Bhat Rosma Ahmad Wan‐Nadiah Wan‐Abdullah Min‐Tze Liong 《International Journal of Food Science & Technology》2010,45(10):2089-2095
We aimed at evaluating agricultural wastes as solid supports for the immobilisation of lactobacilli in a liquid media, namely soymilk. Lactobacillus acidophilus FTDC 1331, L. acidophilus FTDC 2631, L. acidophilus FTDC 2333, L. acidophilus FTDC 1733 and L. bulgaricus FTCC 0411 were immobilised on solid supports produced from durian (Durio zibethinus), cempedak (Artocarpus champeden) and mangosteen (Garcinia mangostana). The immobilised cells were inoculated into soymilk and stored at 4 °C over 168 h. Soymilk inoculated with non‐immobilised cells was used as the control. Immobilised cells showed higher survivability over 168 h compared to the control, accompanied by higher reduction of simple sugars and oligosaccharides in soymilk. Higher growth and higher utilisation of substrates also led to the higher production of lactic and acetic acids, which lowered the pH in soymilk compared to the control. Our results illustrated that agrowastes could be used as immobilisers to enhance the growth of lactobacilli in a liquid medium. 相似文献
47.
Kazem M. Sadeghi Mohammad-Ali Sadeghi Teh Fu Yen 《Petroleum Science and Technology》1990,8(7):769-791
Reducible aromatic species in coal liquid products from five major processes (Synthoil, FMC COED, HRI H-Coal, PAMCO SRC, and Catalytic Inc. SRC) together with solvent elution chromatography fractions of a selected asphaltene has been evaluated. The half-wave potentials measurments are found to be consistant with other methods. The total polarographic reduction of measurement per average molecule for Synthoil solvent fractions, as measured by diffusion constant (id/C), increases in the following manner: gas oil → resin → asphaltene → carbene → carboid. The same trend was observed when color indices (I) and refractive indices (n25) were individually studied. 相似文献
48.
Teo M. Mhaisalkar S.G. Wong E.H. Poi-Siong Teo Wong C.C. Kristine Ong Chin Foo Goh Lay Kuan Teh 《Components and Packaging Technologies, IEEE Transactions on》2005,28(1):157-164
The anisotropic conductive adhesive (ACA) is a promising solder alternative candidate that shows potential for further pitch reduction. Although much work has been published on ACA joint behavior, study on correlation of material properties with reliability performance is still lacking. The main objective in this study was to identify the impact of material properties on reliability, so as to engineer highly reliable microelectronics assemblies. Four representative ACA materials (both film and paste types) with diverse properties were selected. Material properties were characterized as close as possible to "stress test" conditions so as to allow more accurate correlation predictions. Reliability performance was obtained by assembling test chips of 200-/spl mu/m pitch onto BT-substrates, then subjecting them to reliability tests. Correlation analysis was conducted and key material properties that contributed to good reliability performance were identified. Findings indicated that the best properties for high reliability assemblies were: high adhesion strength after subjecting to "stress aging", low coefficient of moisture expansion (CME) and low elastic modulus (E). 相似文献
49.
Van Quan TRAN Hai-Van Thi MAI Thuy-Anh NGUYEN Hai-Bang LY 《Frontiers of Structural and Civil Engineering》2022,16(7):928
The compressive strength of self-compacting concrete (SCC) needs to be determined during the construction design process. This paper shows that the compressive strength of SCC (CS of SCC) can be successfully predicted from mix design and curing age by a machine learning (ML) technique named the Extreme Gradient Boosting (XGB) algorithm, including non-hybrid and hybrid models. Nine ML techniques, such as Linear regression (LR), K-Nearest Neighbors (KNN), Support Vector Machine (SVM), Decision Trees (DTR), Random Forest (RF), Gradient Boosting (GB), and Artificial Neural Network using two training algorithms LBFGS and SGD (denoted as ANN_LBFGS and ANN_SGD), are also compared with the XGB model. Moreover, the hybrid models of eight ML techniques and Particle Swarm Optimization (PSO) are constructed to highlight the reliability and accuracy of SCC compressive strength prediction by the XGB_PSO hybrid model. The highest number of SCC samples available in the literature is collected for building the ML techniques. Compared with previously published works’ performance, the proposed XGB method, both hybrid and non-hybrid models, is the most reliable and robust of the examined techniques, and is more accurate than existing ML methods (R2 = 0.9644, RMSE = 4.7801, and MAE = 3.4832). Therefore, the XGB model can be used as a practical tool for engineers in predicting the CS of SCC. 相似文献
50.
Chou Yong Tan Ramesh Singh Yee Ching Teh Yoke Meng Tan Boon Kar Yap 《International Journal of Applied Ceramic Technology》2015,12(2):437-442
In this work, the sinterability of forsterite powder synthesized via solid‐state reaction was investigated. X‐ray diffraction (XRD) analyses indicate that the synthesized powder possessed peaks that correspond to stoichiometric forsterite. Scanning electron micrographs revealed that the powders were formed agglomerates, which were made up of loosely packed fine particles. Subsequently, the forsterite powders were cold isostatically pressed into a disk shape under 200 MPa and sintered in air at temperature ranging from 1200°C to 1500°C (interval of 50°C) with ramp rate of 10°C/min and dwelling time of 2 h. The sinterability of each sintered samples was examined in terms of phase stability, relative density, Vickers hardness, fracture toughness, and microstructural examination. XRD examination on all the sintered samples exhibited pure forsterite, in which the generated peaks were found to be in a good agreement with JCPDS card no. 34‐0189. The densification of forsterite progressed to reach a maximum relative density of ~91% at 1500°C. This study also revealed that high‐strength forsterite ceramic can be synthesized via solid‐state reaction as forsterite attained favorable mechanical properties, having fracture toughness of 4.88 MPam1/2 and hardness of 7.11 GPa at 1400°C. 相似文献