全文获取类型
收费全文 | 408篇 |
免费 | 56篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 49篇 |
综合类 | 30篇 |
化学工业 | 79篇 |
金属工艺 | 35篇 |
机械仪表 | 17篇 |
建筑科学 | 18篇 |
矿业工程 | 17篇 |
能源动力 | 9篇 |
轻工业 | 19篇 |
水利工程 | 15篇 |
石油天然气 | 29篇 |
武器工业 | 1篇 |
无线电 | 26篇 |
一般工业技术 | 43篇 |
冶金工业 | 11篇 |
原子能技术 | 15篇 |
自动化技术 | 73篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 28篇 |
2021年 | 23篇 |
2020年 | 21篇 |
2019年 | 10篇 |
2018年 | 18篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 21篇 |
2014年 | 16篇 |
2013年 | 22篇 |
2012年 | 27篇 |
2011年 | 31篇 |
2010年 | 27篇 |
2009年 | 28篇 |
2008年 | 20篇 |
2007年 | 15篇 |
2006年 | 22篇 |
2005年 | 28篇 |
2004年 | 18篇 |
2003年 | 13篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 2篇 |
1988年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有486条查询结果,搜索用时 31 毫秒
11.
分布式地理信息系统基础研究 总被引:15,自引:1,他引:14
地理空间数据是地理信息系统的基础。结合面向对象技术、对象关系数据库技术和索引技术,文章从地理空间数据模型、地理空间数据访问服务器和空间索引等方面对地理空间数据的表示和管理进行了研究和探讨,为分布式地理信息系统的建设提供了良好的基础。 相似文献
12.
空间信息共享与互操作的关键问题分析 总被引:4,自引:0,他引:4
对当前空间信息共享与互操作中的关键问题进行了比较全面和深入的分析。由于GIS产品在服务接口上的各异性和局限性,它很难满足Internet上空间信息互操作的需求,这样Internet用户与空间信息资源之间就出现了两大鸿沟:信息获取鸿沟和信息理解鸿沟。Internet用户与空间信息资源之间的鸿沟可以归纳成空间信息互操作中的3个关键问题:可达性问题,即用户难以获取空间信息;可用性问题,即用户难以理解空间信息;易用性问题,即用户难以方便地使用并处理空间信息。最后,从信息互操作框架和GIS实现技术两个方面分析和总结了当前正在进行的一些相关工作。 相似文献
13.
首先提出在居住区规划中进行生态设计的理念及这一设计要依据的原則和生态学原理,然后概括出其涉及的主要内容与具体设计方法. 相似文献
14.
Performance evaluation of a sequential minimal radial basisfunction (RBF) neural network learning algorithm 总被引:12,自引:0,他引:12
Lu Yingwei Sundararajan N. Saratchandran P. 《Neural Networks, IEEE Transactions on》1998,9(2):308-318
Presents a detailed performance analysis of the minimal resource allocation network (M-RAN) learning algorithm, M-RAN is a sequential learning radial basis function neural network which combines the growth criterion of the resource allocating network (RAN) of Platt (1991) with a pruning strategy based on the relative contribution of each hidden unit to the overall network output. The resulting network leads toward a minimal topology for the RAN. The performance of this algorithm is compared with the multilayer feedforward networks (MFNs) trained with 1) a variant of the standard backpropagation algorithm, known as RPROP and 2) the dependence identification (DI) algorithm of Moody and Antsaklis (1996) on several benchmark problems in the function approximation and pattern classification areas. For all these problems, the M-RAN algorithm is shown to realize networks with far fewer hidden neurons with better or same approximation/classification accuracy. Further, the time taken for learning (training) is also considerably shorter as M-RAN does not require repeated presentation of the training data. 相似文献
15.
Allister Yingwei Tham Chinnasamy Gandhimathi Jayaraman Praveena Jayarama Reddy Venugopal Seeram Ramakrishna Srinivasan Dinesh Kumar 《International journal of molecular sciences》2016,17(8)
Bone transplants are used to treat fractures and increase new tissue development in bone tissue engineering. Grafting of massive implantations showing slow curing rate and results in cell death for poor vascularization. The potentials of biocomposite scaffolds to mimic extracellular matrix (ECM) and including new biomaterials could produce a better substitute for new bone tissue formation. A purpose of this study is to analyze polycaprolactone/silk fibroin/hyaluronic acid/minocycline hydrochloride (PCL/SF/HA/MH) nanoparticles initiate human mesenchymal stem cells (MSCs) proliferation and differentiation into osteogenesis. Electrospraying technique was used to develop PCL, PCL/SF, PCL/SF/HA and PCL/SF/HA/MH hybrid biocomposite nanoparticles and characterization was analyzed by field emission scanning electron microscope (FESEM), contact angle and Fourier transform infrared spectroscopy (FT-IR). The obtained results proved that the particle diameter and water contact angle obtained around 0.54 ± 0.12 to 3.2 ± 0.18 µm and 43.93 ± 10.8° to 133.1 ± 12.4° respectively. The cell proliferation and cell-nanoparticle interactions analyzed using (3-(4,5-dimethyl thiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) MTS assay (Promega, Madison, WI, USA), FESEM for cell morphology and 5-Chloromethylfluorescein diacetate (CMFDA) dye for imaging live cells. Osteogenic differentiation was proved by expression of osteocalcin, alkaline phosphatase activity (ALP) and mineralization was confirmed by using alizarin red (ARS). The quantity of cells was considerably increased in PCL/SF/HA/MH nanoparticles when compare to all other biocomposite nanoparticles and the cell interaction was observed more on PCL/SF/HA/MH nanoparticles. The electrosprayed PCL/SF/HA/MH biocomposite nanoparticle significantly initiated increased cell proliferation, osteogenic differentiation and mineralization, which provide huge potential for bone tissue engineering. 相似文献
16.
Wen Ma Yingwei Qi Ying Liu Yuanming Gao Yu Bai Ruiling Jia Hongying Dong Ruijun Wang Manyu Bao 《International Journal of Applied Ceramic Technology》2022,19(3):1713-1726
In this work, the corrosion behavior, interaction products, and the corrosion mechanism of (1-x)SrZrO3-xLa2Ce2O7(x = 0.3, S7L3; x = 0.5, S5L5; x = 0.7, S3L7) composite bulks after CaO-MgO-Al2O3-SiO2 (CMAS) attack at 1250°C for 1, 4, and 12 h were investigated, respectively. The molten CMAS and the bulks rapidly interacted and generated a dense reaction layer, which mainly composed of La-Ce apatite, Ce2Zr2O7.04, ZrO2 with some Ce, Ca, Si, Mg, and Al elements preventing CMAS from continuous penetration effectively. The formation of CMAS self-crystallizing products such as Ca2Al2SiO7 gehlenite and Mg-Al spinel with high melting points increased the viscosity of CMAS. The elements in the ceramic also diffused into the molten CMAS and formed Ce2Zr2O7.04 and La2Ce2O7, increasing the melt viscosity and blocking the penetration channel of the molten CMAS. The S5L5 bulk has the best corrosion resistance against CMAS attacks. 相似文献
17.
Selective hydrogenation of nitriles to imines over a multifunctional heterogeneous Pt catalyst 下载免费PDF全文
Jilan Long Biaolin Yin Yingwei Li Lianjie Zhang 《American Institute of Chemical Engineers》2014,60(10):3565-3576
Imines and their derivatives are versatile synthetic intermediates for the industrial preparation of both bulk and fine chemicals and for pharmaceuticals, but preparing these compounds efficiently through direct hydrogenation of nitriles are hindered by overhydrogenation to secondary amines. Here we report a highly efficient multifunctional catalyst system for selective hydrogenation coupling of nitriles to secondary imines using a heterogeneous Pt catalyst that was deposited on a nickel‐based metal‐organic framework (MOF) containing DABCO. The catalyst showed excellent synergy in promoting the hydrogenation of a variety of nitriles, giving significantly improved activity and selectivity (up to >99% yield) even under atmospheric pressure of H2. It is suggested that the Lewis base (DABCO) sites on the Ni‐MOF inhibit further hydrogenation of the imines. The influence of H2 pressure, reactant concentration, stirring speed, and reaction temperature was investigated. The kinetics and mechanism of hydrogenation of benzonitrile (BN) by the Pt/Ni‐MOF catalyst has been studied. The reaction showed a first‐order dependence on both BN concentration and H2 pressure. A kinetic model was proposed based on the mechanism of nitriles hydrogenation and compared with experimental observations. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3565–3576, 2014 相似文献
18.
19.
本文以三通管挤胀成形模具为例,采用双三次均匀B样条曲面对该模具的型腔表面进行了几何描述。结果表明,这种方法可以为三通管挤胀成形过程的数值模拟中的动态边界条件处理提供灵活、方便的几何信息,为在数值模拟中实现动态边界条件处理打下良好的基础。 相似文献
20.
采用顶部籽晶提拉法(TSSG)生长出Nd3+:KGd(WO4)2晶体,测得Nd3+实际掺杂浓度3.2at%。测得样品的吸收光谱及荧光光谱,计算得出808nm处吸收截面为0.6799×10-20cm2;荧光输出波长为1068nm和1351nm,测得荧光寿命为112μs。对不同尺寸的两样品进行了激光实验,当LD泵浦源输出功率为900mW时,分别获得326mW,305mW的1064nm激光输出,斜效率分别为62.7%和57.8%。水平和垂直两个方向上光束传输因子M2均小于1.2。经倍频获得532nm的绿光。用Cr:LuAG作为可饱和吸收体进行调Q实验,重复频率为15kHz时,脉冲宽为170ns。 相似文献