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991.
Three-dimensionally ordered long-range macroporous carbon structures were prepared using commercially available phenolic resin
by utilizing sacrificial colloidal silica crystalline arrays as templates that were subsequently removed by HF etching after
pyrolysis in an argon atmosphere. SEM, TEM, and BET were employed to characterize the morphology and the surface area of the
porous carbon structures. The pore size (150–1000 nm) and BET surface area, which reflect pore volume (298.6 m2/g (1.32 cm3/g) ∼ 93.7 m2/g (0.12 cm3/g)), of the macroporous carbon structures produced were approximately proportional to the size (150–1000 nm) of the sacrificial
silica sphere templates used (annealing temp. 550°C). The achieved 550 nm porous carbon structures were examined to function
as potential catalyst carriers and were successfully impregnated with Ag or Pt-Ru on their inner walls after borohydride reduction
at room temperature. In addition, porous carbon patterns were fabricated using the ‘micromolding in capillary’ technique,
which has potential applications in the microreaction technology. 相似文献
992.
基于背景和帧间差分法的运动目标提取 总被引:1,自引:0,他引:1
在自动人脸识别系统中,人体目标的检测是该系统识别人脸的前期关键步骤之一。为了能快速准确地检测出运动的人体目标,提出了背景差分法和帧间差分法相结合的运动目标提取检测方法。针对视频中的背景因镜头摆动或物体的移入/移出而有所变动,给出了几种提取背景的方法,比较各种方法后决定采用中值法快速地进行背景建模,随后采用自适应背景更新,结合两种差分法检测运动目标。通过实验验证了本文算法的有效性。 相似文献
993.
目前高校不断扩招,生源却逐渐减少,于是预防和减少学生流失正成为各高校必须面对的问题。通过对高校学生流失情况进行数据挖掘,可发现一些有价值的信息,为解决高校学生流失问题提供帮助。基于糊模理论提出了糊模ID3算法,并将该算法运用于分析高校学生流失原因之中。通过实验证明,该算法生成的决策树更加合理,分类速度更快,为解决高校学生流失问题提供了理论依据。 相似文献
994.
煤部分气化燃烧集成系统最优化模型及其求解 总被引:1,自引:1,他引:1
运用已有的基础动力学数据,将流化床气化过程用全混流模型描述,同时认为部分气化煤焦的燃烧速率相当快,其产生的电能只与燃烧的炭量成线性关系,不受其他因素的影响,在此简化条件的基础上建立了一个部分气化、燃烧集成优化的经济评价模型。通过对模型的模拟计算发现:煤部分气化、燃烧集成优化是可行的,采用这一集成技术在提高煤炭利用率的同时,也可提高经济效益;1000℃时,三种煤的最优气化率在60%~80%之间,活性好的神木煤其最优部分气化率最高;提高气化温度,可以提高煤焦最优气化率,从而可提高总体经济效益。 相似文献
995.
对硝基苯酚臭氧化反应动力学研究 总被引:6,自引:0,他引:6
在T=298K,pH=2.1~6,采用停流光谱仪研究了对硝基苯酚与臭氧在水溶液中的臭氧化反应动力学。实验结果表明,对硝基苯酚臭氧化总的反应是2级,对臭氧浓度和对硝基苯酚浓度分别为1级。臭氧化反应速率常数随溶液pH值的增大而增大;T=298K时,当pH值从2.1变化到6,总的反应速率常数从5.88×104L(mol·s)-1增大到1.56×106L(mol·s)-1。为了验证其适用性,对臭氧在搅拌釜中在对硝基苯酚溶液中的吸收过程进行了模拟。采用MATLAB软件求解臭氧在搅拌釜中在对硝基苯酚溶液中吸收过程的质量平衡方程,模拟得到了吸收过程中臭氧和对硝基苯酚浓度的变化,并与实验值进行了比较。结果表明,在85%的对硝基苯酚降解之前,模拟值和实验值能很好地一致。在反应末期,模拟值和实验值出现了一定的偏差。 相似文献
996.
Isidoro Izquierdo Cubero Maria T. Plaza López-Espinosa Rafael Acuña Castillo 《Journal of chemical ecology》1991,17(8):1529-1541
The synthesis of the title compound13 has been carried out through the preparation of its precursor, (3R,4R,5S,6R)-3,4,5-trihydroxy-1,7-dioxaspiro[5.5]undecane (6), obtained fromd-fructose using Wittig's methodology, reduction, and spiroketalation. Compound6 was transformed into13 by a Barton deoxygenation at C-5 followed by a Corey dideoxygenation at C-3,4 of the appropriately protected derivatives.Enantiospecific synthesis of spiroacetals. Part II. For Part I, see Izquierdo and Plaza (1990). 相似文献
997.
研究了不同外加剂对陶瓷釉面表面性质的影响。研究表明 ,外加剂的加入可改变陶瓷釉面的表面张力 ,即影响液体对陶瓷釉面的润湿性能。在所选择的外加剂中 ,降低陶瓷釉面表面张力最强的为PbO ,其合适的加入量为 1.5 %。 相似文献
998.
The anionic polymerization of lauryllactam was initiated at 270°C using sodium hydride as an initiator and N,N′‐ethylene‐bisstearamide (EBS) as an activator (NaH:EBS molar ratio of 2). Polymerization occurred in less than 2 min and was successfully performed in an internal mixer and a twin‐screw extruder with corotating intermeshing screws (Werner & Pfleiderer ZSK 25). The content of residual monomer, as determined by thermogravimetric analysis, was lower than 0.5 wt %. Molecular weight, as measured by size exclusion chromatography, was governed by the lauryllactam:NaH molar ratio calculated on a Mn of 25 kg/mol at a constant NaH:EBS molar ratio of 2. Blends were prepared in situ by polymerization of lauryllactam solutions of various polymers. When poly(ethylene‐co‐butylacrylate) (Lotryl®; Atofina) was dissolved in lauryllactam, rubber‐toughened polyamide 12 blends were obtained. Mechanical properties of the injection‐molded polymers were examined by stress–strain as well as notched Charpy impact tests at different temperatures. Blend morphologies were imaged by scanning electron microscopy (SEM). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 344–351, 2003 相似文献
999.
1000.
Coordination between strategic forest management and tactical logistic and production planning in the forestry supply chain 总被引:1,自引:0,他引:1
Jiehong Kong Mikael Rönnqvist 《International Transactions in Operational Research》2014,21(5):703-735
In this paper, we study the coordination mechanism in the forestry supply chain between strategic forest management and tactical production planning. We first formulate an integrated model to establish a theoretical benchmark for performance of the entire supply chain. It is a mixed integer programming model that involves harvesting, bucking, transportation, production, and sales decisions for both tactical and strategic planning levels. We then present two sequential approaches S‐A and S‐B where the coordination is done through internal pricing. S‐A is the approach currently used in practice where harvesting in the forest is the main driver of the supply chain activities and internal pricing is introduced to control bucking decision in a separate stage. In contrast, S‐B takes downstream demand information into consideration and internal pricing directly influences harvesting decision in the first stage. In order to find the appropriate setting of internal pricing that leads to the system optimum, we suggest two heuristics H‐I and H‐II. The internal pricing in H‐I is based on dual values and in H‐II, it is derived from a Lagrangian decomposition. A real‐life case study in the Chilean forestry industry is used to compare the results of different approaches. It is shown that the new sequential approach S‐B generates as good feasible solution as that obtained from the integrated approach but in much less time. Both heuristics H‐I and H‐II bring about near‐optimal feasible solutions. H‐II also provides optimistic bound of the optimal objective function value, which can be used as a measure of the solution quality. 相似文献