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   3788篇
  免费   173篇
  国内免费   1篇
电工技术   52篇
综合类   22篇
化学工业   566篇
金属工艺   140篇
机械仪表   75篇
建筑科学   145篇
矿业工程   18篇
能源动力   33篇
轻工业   448篇
水利工程   44篇
石油天然气   1篇
无线电   213篇
一般工业技术   691篇
冶金工业   1060篇
原子能技术   11篇
自动化技术   443篇
  2023年   42篇
  2022年   34篇
  2021年   73篇
  2020年   52篇
  2019年   48篇
  2018年   85篇
  2017年   84篇
  2016年   105篇
  2015年   91篇
  2014年   88篇
  2013年   170篇
  2012年   173篇
  2011年   187篇
  2010年   125篇
  2009年   110篇
  2008年   151篇
  2007年   101篇
  2006年   105篇
  2005年   73篇
  2004年   68篇
  2003年   65篇
  2002年   71篇
  2001年   52篇
  2000年   33篇
  1999年   63篇
  1998年   350篇
  1997年   188篇
  1996年   157篇
  1995年   88篇
  1994年   98篇
  1993年   84篇
  1992年   19篇
  1991年   37篇
  1990年   22篇
  1989年   40篇
  1987年   31篇
  1986年   23篇
  1985年   32篇
  1984年   22篇
  1983年   27篇
  1982年   30篇
  1981年   20篇
  1980年   24篇
  1979年   26篇
  1978年   18篇
  1977年   30篇
  1976年   72篇
  1919年   18篇
  1911年   16篇
  1910年   23篇
排序方式: 共有3962条查询结果,搜索用时 109 毫秒
101.
The Internet Protocol (IP) has been proven very flexible, being able to accommodate all kinds of link technologies and supporting a broad range of applications. The basic principles of the original Internet architecture include end-to-end addressing, global routeability and a single namespace of IP addresses that unintentionally serves both as locators and host identifiers. The commercial success and widespread use of the Internet have lead to new requirements, which include Internetworking over business boundaries, mobility and multi-homing in an untrusted environment. Our approach to satisfy these new requirements is to introduce a new Internetworking layer, the node identity layer. Such a layer runs on top of the different versions of IP, but could also run directly on top of other kinds of network technologies, such as MPLS and 2G/3G PDP contexts. This approach enables connectivity across different communication technologies, supports mobility, multi-homing, and security from ground up. This paper describes the Node Identity Architecture in detail and discusses the experiences from implementing and running a prototype.  相似文献   
102.
The steady-state simplified P N approximation to the radiative transfer equation has been successfully applied to many problems involving radiation. Recently, time-dependent simplified P N equations have been derived by an asymptotic analysis similar to the asymptotic derivation of the steady-state SP N equations (Frank et al. in J. Comput. Phys. 226:2289–2305, 2007). In this paper, we present computational results for the time-dependent SP N equations in two dimensions, obtained by using an adaptive finite element approach. Several numerical comparisons with other existing models are shown.  相似文献   
103.
Storing textures on orthogonal tensor product lattices is predominant in computer graphics, although it is known that their sampling efficiency is not optimal. In two dimensions, the hexagonal lattice provides the maximum sampling efficiency. However, handling these lattices is difficult, because they are not able to tile an arbitrary rectangular region and have an irrational basis. By storing textures on rank‐1 lattices, we resolve both problems: Rank‐1 lattices can closely approximate hexagonal lattices, while all coordinates of the lattice points remain integer. At identical memory footprint texture quality is improved as compared to traditional orthogonal tensor product lattices due to the higher sampling efficiency. We introduce the basic theory of rank‐1 lattice textures and present an algorithmic framework which easily can be integrated into existing off‐line and real‐time rendering systems.  相似文献   
104.
105.
Dagstuhl seminar no. 10102 on discrete event logistic systems recognized a network of persistent models to be a “Grand Challenge.” Such on-line model network will offer an infrastructure that facilitates the management of logistic operations. This ambition to create a network of persistent models implies a radical shift for model design activities as the objective is an infrastructure rather than application-specific solutions. In particular, model developers can no longer assume that they know what their model will be used for. It is no longer possible to design for the expected.This paper presents insights in model development and design in the absence of precise knowledge concerning a model's usage. Basically, model developers may solely rely on the presence of the real-world counterpart mirrored by their model and a general idea about the nature of the application (e.g. coordination of logistic operations). When the invariants of their real-world counterpart suffice for models to be valid, these models become reusable and integrate-able. As these models remain valid under a wide range of situations, they become multi-purpose and durable resources rather than single-purpose short-lived components or legacy, which is even worse.Moreover and more specifically, the paper describes how to build models that allow their users to generate predictions in unexpected situations and atypical conditions. Referring to previous work, the paper concisely discusses how these predictions can be generated starting from the models. This prediction-generating technology is currently being transferred into an industrial MES.  相似文献   
106.
Abstract— A polymer‐dispersed liquid‐crystal (PDLC) matrix template embedded with nano/microparticles can be backfilled/infiltrated with a dye‐doped liquid crystal for a paper‐like reflective display. In this way, a desirable degree of diffusion can be realized to reduce the viewing‐angle dependency of a gain reflector and metallic glare without changing other electro‐optical properties.  相似文献   
107.
108.
Hébert C  Schöne WD  Su DS 《Ultramicroscopy》2006,106(11-12):1115-1119
We show the experimental and calculated q-dependent low energy loss electron energy loss spectrum of Ru and Ag. The spectra were calculated within the time-dependent density-functional theory including local-field effects. For Ag, the momentum transfer was parallel to the (110) direction. For Ru the three main directions (010), (110) and (001) were investigated. The agreement between theory and experiment is very good for Ag and for momentum transfers parallel to the (001) direction of Ru. For momentum transfers parallel to the in-plane directions (110) and (010) the agreement for Ru is not satisfactory, which could be attributed to relativistic effects or to strong localization of the 4d states of Ru.  相似文献   
109.
Heart rate variability (HRV) represents the cardiovascular control mediated by the autonomic nervous system and other mechanisms. In the established task force HRV monitoring different cardiovascular control mechanisms can approximately be identified at typical frequencies of heart rate oscillations by power spectral analysis. HRV measures assessing complex and fractal behavior partly improved clinical risk stratification. However, their relationship to (patho-)physiology is not sufficiently explored. Objective of the present work is the introduction of complexity measures of different physiologically relevant time scales. This is achieved by a new concept of the autonomic information flow (AIF) analysis which was designed according to task force HRV. First applications show that different time scales of AIF improve the risk stratification of patients with multiple organ dysfunction syndrome and cardiac arrest patients in comparison to standard HRV. Each group's significant time scales correspond to their respective pathomechanisms.  相似文献   
110.
Results from investigations on the metabolism of 14C-Fenazox show that in 6-8 weeks old tomato-plants (sort "Harzfeuer") the agent undergoes a biotransformation. After chromatographic separation the structure of the biotransformation products was elucidated by comparison to authentic test substances, by derivatization as well as by means of physico-chemical methods. With that, the following metabolites were identified: non-transformed Fenazox, o-hydroxyazobenzene, o-hydroxyaniline, and p-hydroxyaniline. Probably, the agent is first transformed enzymatically or non-enzymatically into o-hydroxyazobenzene, then follows a reductive cleavage into o-hydroxyaniline and aniline. In its turn, the latter is transformed into o-hydroxy- and p-hydroxyaniline. Experiments in the field of transformation kinetics indicated that the concentration of the applied Fenazox rapidly decreases and that the first transformation product o-hydroxyazobenzene in the beginning increases and then again decreases in its concentration. With increasing application time it comes to an increase of the non-extractable residues.  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