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991.
992.
PC/TPU共混物的流变性能 总被引:5,自引:0,他引:5
用毛细管流变仪研究了聚碳酸酯(PC)及聚碳酸酯/热塑性聚氨酯弹性体(PC/TPU)共混物的流变性能。实验结果表明:PC熔体粘度对剪切速率(γ)不敏感,而对温度(T)敏感。温度升高,PC粘度降低。加入TPU大大改善了共混物的流动性能,使共混物的成型加工变得容易进行。当TPU含量为40份时,共混物的熔体粘度出现一极小值。加入不同第三组分对于降低共混物的熔体粘度效果不同,第三组分E对共混物有增粘作用 相似文献
993.
We determined the optimal reaction conditions to minimize the energy cost and the quantities of by‐products for a poly(ethylene terephthalate) process by using the iterative dynamic programming (IDP) algorithm. Here, we employed a sequence of three reactor models: the semibatch transesterification reactor model, the semibatch prepolymerization reactor model, and the rotating‐disc‐type polycondensation reactor model. We selectively chose or developed the reactor models by incorporating experimentally verified kinetic models reported in the literature. We established the model for the entire reactor system by connecting the three reactor models in series and by resolving some joint problems arising when different types of reactor models were interconnected. On the basis of the simulation results of the reactor system, we scrutinized the cause and effect between the reaction conditions and the final quality of the polymer product. Here, we set up the optimization strategy by using IDP on the basis of the integrated reactor model, and the process variables with significant influence on the properties of polymer were selected as control variables with the help of a simulation study. With this method, we could refine the reaction conditions at the end of each iteration step by contracting the spectra of control regions, and the iteration process finally stopped when the profile of the optimal trajectory converged. We also took the constraints on the control variables into account to guarantee polymer quality and to suppress side reactions. Constituting six different strategies by setting weighting vectors differently, we examined the differences in optimal trajectories, the trend of optimality, and the quality of the final polymer product. For each of the strategies, we conducted the optimization to examine whether the number‐average degree of polymerization approached the desired value. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 993–1008, 2002 相似文献
994.
F.J. Medellín‐Rodríguez J.M. Mata‐Padilla B.S. Hsiao M.A. Waldo‐Mendoza E. Ramírez‐Vargas S. Sánchez‐Valdes 《Polymer Engineering and Science》2007,47(11):1889-1897
The influence of organomodified nanoclay (montmorillonite) on the crystallization and melting mechanisms of isotactic polypropylene (iPP) was studied. Films of both neat polymer and clay nanocomposites were prepared after molecular weight optimization through melt extrusion. Products exhibited the tactoidlike morphology since no compatibilizers were used. The effect of introduction of nanoclay within the polymer was studied through isothermal crystallization and linear heating. The results indicated that low nanoclay concentrations induce the formation of the β‐crystalline structure, its formation being inhibited with high nanoclay contents. Dynamic nonisothermal bulk crystallization experiments indicated that nanoclays act as nucleating agents of iPP. Isothermal, bulk crystallization studies indicated that the crystallization process (induction time and crystallization kinetics) is proportionally accelerated by the nanoclay presence. There was also an accelerated formation of secondary crystallization when nanoclays were present in high concentrations. POLYM. ENG. SCI., 47:1889–1897, 2007. © 2007 Society of Plastics Engineers 相似文献
995.
Carbon/carbon composites were made through the pyrolysis of stabilized PAN felt and phenolic resin with the addition of 5 or 10 wt % carbon black to the matrix and then heat treatment at 600–2500°C. The effects of adding carbon black to the matrix precursor on the physical properties, microstructure, and mechanical properties of the resultant composites were investigated. Adding carbon black not only reduced the weight loss but also limited the shrinkage of the resultant composites. Adding carbon black also accelerated the formation of carbon basal planes in the matrix. At 2500°C, the crystalline stacking height in the composite with 10 wt % added carbon black was 200% greater than that with no additive. The flexural strength of the composite also increased from 15 to 42 MPa (almost 300%). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 333–337, 2006 相似文献
996.
Novel diastereomeric acrylic ketal monomers derived from (+)‐camphor and (±)‐camphor were synthesized. To investigate the applications of the camphor derivatives on positive‐tone photoresists, the acrylic ketal monomers were copolymerized with methyl methacrylate, methacrylic acid, and n‐butyl methacrylate. The optical activities of the chiral monomers and polymers were all evaluated. After UV irradiation and postexposure baking, the optical activity of the polymers decreased because of the decomposition of the acid‐labile pendant chiral groups. The existence of alicyclic camphyl groups increased the etching resistance of the photoresists. The thermogravimetric properties of the copolymers, the exposure curves, the lithographic evaluation of the positive‐tone photoresists, and the effects of alicyclic groups on the plasma etching resistance of the copolymers were all investigated. A resolution of a line‐and‐space pattern of 0.3 μm was achieved. Acid‐catalyzed dehydration crosslinking was also found in this system. Sufficient UV irradiation and heat treatment could cause the acid‐catalyzed dehydration crosslinking of pendant carboxyl groups and thereby increase the efficiency of the thermal resistance of the polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2969–2978, 2003 相似文献
997.
细颗粒循环料腿的自力平衡原理及实验研究 总被引:3,自引:0,他引:3
本文介绍了一种固体细颗粒循环料腿的自力平衡结构模型(单气路式)及其工作原理,对该结构模型进行了流体力学分析,并分析了各种因素对自力平衡效果的影响趋势。在冷态模型装置上进行的实验测定验证了料腿的自平衡效果,并获得了与理论分析相一致的结论。由于该结构简单,无机械运动部件,并且易满足耐高温、耐高压及耐磨损等性能要求,特别是它能在较宽的工作范围内使料腿自力稳定,它的应用可望改善固体料循环控制的可操作性,从而对特定的工作系统有利。 相似文献
998.
为了辨识具有谐波减速器的柔性关节模型的关键参数,设计了一套基于多传感器融合的离线辨识方法,根据电机的位置传感器、电流传感器和关节力矩传感器的实验数据完成柔性关节模型关键参数的辨识.首先,建立采用谐波减速器柔轮输出的柔性关节模型;然后,使用正反转加载力矩的方法辨识出电机的力矩系数;并在空载的情况下,由关节力矩和电机输出力矩分别辨识出关节端和电机端的摩擦力;最后,采用敲击法初步辨识出关节的刚度和阻尼后,在关节位置受限条件下,逐渐增加电机输出力矩,得到柔性关节刚度和关节力矩的非线性关系.多次实验的结果显示,辨识出的参数具有较高的重复性,验证了该方法的有效性. 相似文献
999.
1000.