首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   28007篇
  免费   2464篇
  国内免费   1246篇
电工技术   1634篇
技术理论   3篇
综合类   1738篇
化学工业   4665篇
金属工艺   1950篇
机械仪表   1714篇
建筑科学   2457篇
矿业工程   775篇
能源动力   739篇
轻工业   1755篇
水利工程   464篇
石油天然气   1527篇
武器工业   224篇
无线电   3239篇
一般工业技术   3586篇
冶金工业   1187篇
原子能技术   295篇
自动化技术   3765篇
  2024年   164篇
  2023年   538篇
  2022年   942篇
  2021年   1340篇
  2020年   989篇
  2019年   735篇
  2018年   861篇
  2017年   885篇
  2016年   788篇
  2015年   1037篇
  2014年   1247篇
  2013年   1564篇
  2012年   1676篇
  2011年   1776篇
  2010年   1645篇
  2009年   1517篇
  2008年   1472篇
  2007年   1491篇
  2006年   1450篇
  2005年   1335篇
  2004年   946篇
  2003年   828篇
  2002年   829篇
  2001年   657篇
  2000年   750篇
  1999年   790篇
  1998年   643篇
  1997年   512篇
  1996年   520篇
  1995年   409篇
  1994年   341篇
  1993年   261篇
  1992年   221篇
  1991年   142篇
  1990年   93篇
  1989年   95篇
  1988年   73篇
  1987年   42篇
  1986年   36篇
  1985年   17篇
  1984年   16篇
  1983年   12篇
  1982年   10篇
  1981年   8篇
  1980年   8篇
  1979年   1篇
  1978年   1篇
  1970年   1篇
  1969年   1篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 35 毫秒
51.
This paper presents an intuitive nose surgery planning and simulation system, using 3D laser scan image and lateral X-ray image, to provide high quality prediction of the postoperative appearance, and design the patient specific prosthesis model automatically. After initial registration, the internal surface of soft tissue at the nose region was generated by the statistical data for soft tissue thickness adapted by the individual thickness information from the X-ray image. Then, the sketch contour of the 3D scan data on the lateral X-ray image was modified manually or adjusted automatically according to some aesthetic statistical data, to drive the simulation in real time by the state-of-the-art Laplacian surface deformation method. When satisfied with the 3D postoperative appearance, the deformation was mapped to the internal surface of soft tissue, and the change before and after simulation was utilized to generate the patient specific prosthesis model automatically. The surgeons who used the system confirmed that this planning system is attractive and has potential for daily clinical practice.  相似文献   
52.
An interactive three-dimensional finite element generation method is presented for modelling a multi-connected teeth and mandible structure. The tetrahedron is chosen as the basic element type due to its rigorous adaptability to structures with geometric complexities. The mesh generation is implemented by allocating two quadrangles in adjacent CT image slices to form a set of tetrahedrons. By examining all the possible allocations and their degradations, an algorithm is developed for interactive mesh generation, resulting in a series of tetrahedrons consistent with all the others without overlapping and spacing. The developed system was applied to a tooth-mandibular structure, generating a complicated 3D FEM model consisting of 4762 nodes and 18,534 tetrahedral elements with nine different materials. This 3D model was successfully used to evaluate different tooth restoration strategies, which proved the viability and effectiveness of the proposed method.  相似文献   
53.
面向企业的运输销售管理信息系统设计   总被引:3,自引:0,他引:3  
翟丁  张庆灵 《控制与决策》2001,16(Z1):837-839
以石油企业运输销售经营管理为背景,对运输销售管理信息系统进行了研究.以软件工程为指导,运用先进的设计方法与结构分析,并结合数据库的特点给出了运输销售管理信息系统具体的设计方案.  相似文献   
54.
请求式拨号网络还存在着冗余很大的网络传输和拨号连接,为减少电信成本,文章尝试对Windows NT请求式拨号网络进行优化。  相似文献   
55.
丁振凡 《微型电脑应用》2000,16(5):61-63,58
介绍了利用ASP编写一个聊天室应用的关键技术及程序实现。  相似文献   
56.
中药知母有效组分——知母皂甙元“滋阴”作用的研究   总被引:1,自引:0,他引:1  
本工作以~(123)I-心得静结合分析法及环核苷酸RIA法观察了知母中提取得到的知母皂甙元对甲亢模型(模拟“阴虚”)βAR-cAMP系统的作和,结果表现,知母皂甙元明显降低甲亢小鼠脑β受体的RT值,显著降低甲亢小鼠β受体-cAMP系统的反应性,重现了知母水煎剂的下调作用。体外竞争抑制实验表明,知母皂甙元和知母皂甙元半琥珀酸都不能抑制~(125)I-心得静与β受体的结合。  相似文献   
57.
This paper presents an integration technology for RF passives using benzocyclobutene (BCB)/metal multilayer interconnection for system-in-package applications. This technology has been specially developed for RF subsystem packages in which a thick polymer, BCB (more than 15 μm thick), is adopted as dielectric with lossy silicon as substrate for its excellent characteristics. Both dry-etch BCB and photosensitive BCB are applied in this work, and their processes are briefly introduced and compared. An RF power divider, an MIM capacitor, different types of RF inductors as well as a coupled microstrip based band-pass filter are fabricated and measured at wafer level. The results show good electrical performances, and accordingly the passives are well applicable in RF band. Moreover, the subsystem models including monolithic chips connected with passives are presented.  相似文献   
58.
59.
Control of nanosystems with frictional dynamics using feedback control methods is important to a wide range of applications of nanotribology. This paper studies the tracking control problem of an array of nanoparticles moving on a substrate with friction between the substrate and the particles. The focus of this study is on control design and stability analysis. The major challenges in this problem include nonlinearities and uncertainties in the frictional dynamics and limited availability of measurable states in nanosystems. The particle–substrate interaction is considered to be unknown, and the unknown effect of unmodeled particle dynamics on the dynamics of the center of mass of the array is also considered. A nonlinear identifier is first developed to identify these unmodeled dynamics. A feedback controller is then developed based on the identifier to control the center of mass of the particles to track a desired trajectory. Boundedness of the closed-loop states and semiglobal asymptotic stability of the tracking error are proven using Lyapunov theory for the case of linear inter-particle interactions. An example with more general Morse-type inter-particle interactions is included to provide some level of confidence that the results are general but not assuredness that they are. Numerical simulation results are provided to demonstrate the performance of the developed identification and control law.  相似文献   
60.
In Multiple-Input Multiple-Output (MIMO) system, the number of positive channel matrix eigenvalues ~s directly related to system performance. In order to characterize and model channel matrix eigenvalues, channel measurements at 6. 0 -6. 4GHz by using 4 ~ 4 MIMO structure were conducted in a typical classroom environment. Based on measured data, the eigenvalues were modeled as Log-Normal distributed random variables and parameterized. Furthermore, Cross-Correlation (CC) coefficients of eigenvalues were estimated. The measurement results show that, under both Light-Of-Sight (LOS) and Non- Light-Of-Sight (NLOS) scenarios, eigenvalues are highly de-correlatod so that CC can be ignored for eigenvalue model.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号