全文获取类型
收费全文 | 67672篇 |
免费 | 6869篇 |
国内免费 | 3999篇 |
专业分类
电工技术 | 4608篇 |
技术理论 | 1篇 |
综合类 | 6766篇 |
化学工业 | 10471篇 |
金属工艺 | 3793篇 |
机械仪表 | 4097篇 |
建筑科学 | 5230篇 |
矿业工程 | 1728篇 |
能源动力 | 1563篇 |
轻工业 | 8480篇 |
水利工程 | 1669篇 |
石油天然气 | 2327篇 |
武器工业 | 688篇 |
无线电 | 7517篇 |
一般工业技术 | 6529篇 |
冶金工业 | 2400篇 |
原子能技术 | 777篇 |
自动化技术 | 9896篇 |
出版年
2024年 | 227篇 |
2023年 | 1050篇 |
2022年 | 2163篇 |
2021年 | 2889篇 |
2020年 | 2224篇 |
2019年 | 1754篇 |
2018年 | 1802篇 |
2017年 | 2023篇 |
2016年 | 1870篇 |
2015年 | 2779篇 |
2014年 | 3733篇 |
2013年 | 4341篇 |
2012年 | 5043篇 |
2011年 | 5561篇 |
2010年 | 5144篇 |
2009年 | 4936篇 |
2008年 | 5112篇 |
2007年 | 4795篇 |
2006年 | 4347篇 |
2005年 | 3533篇 |
2004年 | 2553篇 |
2003年 | 1949篇 |
2002年 | 1986篇 |
2001年 | 1712篇 |
2000年 | 1389篇 |
1999年 | 901篇 |
1998年 | 566篇 |
1997年 | 431篇 |
1996年 | 394篇 |
1995年 | 328篇 |
1994年 | 216篇 |
1993年 | 164篇 |
1992年 | 126篇 |
1991年 | 119篇 |
1990年 | 70篇 |
1989年 | 66篇 |
1988年 | 63篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1980年 | 19篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1959年 | 6篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Ke Xu Min Zhu GuangWu Hu Liang Zhu YiFeng Zhong Ying Liu JianPing Wu Ning Wang 《中国科学:信息科学(英文版)》2014,57(11):1-24
There is a general consensus about the success of Internet architecture in academia and industry. However, with the development of diversified application, the existing Internet architecture is facing more and more challenges in scalability, security, mobility and performance. A novel evolvable Internet architecture framework is proposed in this paper to meet the continuous changing application requirements. The basic idea of evolvability is relaxing the constraints that limit the development of the architecture while adhering to the core design principles of the Internet. Three important design constraints used to ensure the construction of the evolvable architecture, including the evolvability constraint, the economic adaptability constraint and the manageability constraint, are comprehensively described. We consider that the evolvable architecture can be developed from the network layer under these design constraints. What's more, we believe that the address system is the foundation of the Internet. Therefore, we propose a general address platform which provides a more open and efficient network environment for the research and development of the evolvable architecture. 相似文献
992.
针对2013中国国际太阳能十项全能竞赛比赛规则及零能耗建筑的特点,结合比赛地点山西大同的气候数据,给出了厦门大学参赛作品,零能耗小屋Sunny Inside的能源管理与智能监控系统设计方案.以光伏建筑一体化理论为基础,设计15.25kW光伏并网发电系统,并用相关软件对能耗平衡进行了模拟验证.以三菱PLC为核心,构建了能源管理与智能监控系统,分析了不同条件下空调、相变及遮阳系统的控制策略,并给出具体实现方法. 相似文献
993.
随着现代通信技术的发展,无线通信技术已经在移动通信过程中得到了广泛的应用,发展到了3/4G时代。掉话一直是困扰无线通信技术发展的瓶颈,其由于覆盖、前反向不平衡、参数、终端及用户行为等无线通信固有的原因和特点,成为无线通信过程中需要长期实施优化解决的问题之一,得到了许多网优工作者的研究。 相似文献
994.
995.
A new hybrid polymer electrolyte system based on chemical‐covalent polyether and siloxane phases is designed and prepared via the sol–gel approach and epoxide crosslinking. FT‐IR, 13C solid‐state NMR, and thermal analysis (differential scanning calorimetry (DSC) and TGA) are used to characterize the structure of these hybrids. These hybrid films are immersed into the liquid electrolyte (1M LiClO4/propylene carbonate) to form plasticized polymer electrolytes. The effects of hybrid composition, liquid electrolyte content, and temperature on the ionic conductivity of hybrid electrolytes are investigated and discussed. DSC traces demonstrate the presence of two second‐order transitions for all the samples and show a significant change in the thermal events with the amount of absorbed LiClO4/PC content. TGA results indicate these hybrid networks with excellent thermal stability. The EDS‐0.5 sample with a 75 wt % liquid electrolyte exhibits the ionic conductivity of 5.3 × 10?3 S cm?1 at 95°C and 1.4 × 10?3 S cm?1 at 15°C, in which the film shows homogenous and good mechanical strength as well as good chemical stability. In the plot of ionic conductivity and composition for these hybrids containing 45 wt % liquid electrolyte, the conductivity shows a maximum value corresponding to the sample with the weight ratio of GPTMS/PEGDE of 0.1. These obtained results are correlated and used to interpret the ion conduction behavior within the hybrid networks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1000–1007, 2006 相似文献
996.
采用原位插层聚合法,制备了蒙脱土含量较高的共聚酯/蒙脱土纳米复合材料,意在做母料使用,含有该母料的聚合物复合材料的染色性能、吸湿浸润性能、抗静电性能及抗紫外性能等都有所改善。阐述了合适的共聚酯/蒙脱土纳米复合材料的制备工艺,讨论了制备过程中的影响因素,结果发现:在采用酯交换-缩聚反应釜进行原位插层聚合制备共聚酯/蒙脱土纳米复合材料的过程中,蒙脱土在缩聚釜中加入更符合生产实际;缩聚反应的实际过程证明了蒙脱土中含有的金属离子对缩聚反应有催化作用;另外,控制聚合的最终温度不超过278℃。最后,对共聚酯/蒙脱土纳米复合材料的结构进行了表征。 相似文献
997.
The preparation of very hydrophobic poly(vinylidene fluoride) (PVDF) membranes was explored by using two methods. The first one was the modified phase inversion method using a water/N,N‐dimethylacetamide (DMAc) mixture instead of pure water as a soft precipitation bath. The second method was a precipitation‐bath free method, that is, the PVDF/DMAc casting solution underwent gelation in the open air instead of being immersed into a precipitation bath. The morphology of the surface and cross section of the membranes was investigated by using scanning electron microscopy (SEM). It was found that the membranes exhibited certain micro‐ and nanoscale hierarchical roughness on the surface, which brought about an enhanced hydrophobicity of the membrane. The contact angle (CA) of the samples obtained by the second method was as high as 150° with water. The conventional phase inversion method preparing PVDF porous membrane using pure water as precipitation bath usually results in an asymmetric membrane with a dense skin layer having a CA close to that of a smooth PVDF surface. The modified approach avoided the formation of a skin‐layer and resulted in a porous and highly hydrophobic surface of PVDF. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1358–1363, 2005 相似文献
998.
采用细菌纤维素(BC)、聚乙烯醇(PVA)为原料,通过3D打印与冻融循环法制备超拉伸凝胶电解质。采用SEM、接触角测量、XRD、EIS和拉伸测试对凝胶电解质物理特性、电化学性能及拉伸性能进行表征。实验结果表明,当m(BC)∶m(PVA)=0.6∶1时,基于3D打印制备的凝胶电解质具有稳定的三维网络结构、优异的拉伸性能和电化学性能,拉伸强度可达0.9 MPa、断裂伸长率可达961%、离子电导率为1.10×10-1 S/cm。将该凝胶电解质应用于柔性铝空气电池,功率密度可达21 mW/cm2,电流密度为20 mA/cm2时,铝阳极比容量为1124 mA?h/g,电池可稳定放电90 min。 相似文献
999.
本文提出一种基于神经网络的多效并流蒸发过程的模拟以及优化算法,并以一简单三效并流蒸发过程为例,详细阐述了神经网络模拟算法的具体步骤。该算法具有对初始值要求不高、收敛速度快,全局收敛性好的特点。 相似文献
1000.
With the unique ergodicity, irregularity, and special ability to avoid being trapped in local optima, chaos optimization has been a novel global optimization technique and has attracted considerable attention for application in various fields, such as nonlinear programming problems. In this article, a novel neural network nonlinear predictive control (NNPC) strategy based on the new Tent-map chaos optimization algorithm (TCOA) is presented. The feedforward neural network is used as the multi-step predictive model. In addition, the TCOA is applied to perform the nonlinear rolling optimization to enhance the convergence and accuracy in the NNPC. Simulation on a laboratory-scale liquid-level system is given to illustrate the effectiveness of the proposed method. 相似文献