全文获取类型
收费全文 | 32740篇 |
免费 | 4131篇 |
国内免费 | 2873篇 |
专业分类
电工技术 | 2953篇 |
技术理论 | 7篇 |
综合类 | 4532篇 |
化学工业 | 1211篇 |
金属工艺 | 500篇 |
机械仪表 | 1492篇 |
建筑科学 | 9688篇 |
矿业工程 | 698篇 |
能源动力 | 630篇 |
轻工业 | 710篇 |
水利工程 | 1042篇 |
石油天然气 | 981篇 |
武器工业 | 302篇 |
无线电 | 3485篇 |
一般工业技术 | 2208篇 |
冶金工业 | 463篇 |
原子能技术 | 272篇 |
自动化技术 | 8570篇 |
出版年
2024年 | 102篇 |
2023年 | 416篇 |
2022年 | 785篇 |
2021年 | 884篇 |
2020年 | 954篇 |
2019年 | 840篇 |
2018年 | 824篇 |
2017年 | 1015篇 |
2016年 | 1197篇 |
2015年 | 1398篇 |
2014年 | 2388篇 |
2013年 | 2047篇 |
2012年 | 2660篇 |
2011年 | 2788篇 |
2010年 | 2295篇 |
2009年 | 2336篇 |
2008年 | 2368篇 |
2007年 | 2531篇 |
2006年 | 2169篇 |
2005年 | 1765篇 |
2004年 | 1384篇 |
2003年 | 1149篇 |
2002年 | 921篇 |
2001年 | 822篇 |
2000年 | 728篇 |
1999年 | 573篇 |
1998年 | 427篇 |
1997年 | 308篇 |
1996年 | 283篇 |
1995年 | 276篇 |
1994年 | 218篇 |
1993年 | 151篇 |
1992年 | 175篇 |
1991年 | 103篇 |
1990年 | 85篇 |
1989年 | 88篇 |
1988年 | 65篇 |
1987年 | 33篇 |
1986年 | 35篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1975年 | 6篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
基于地理信息系统的天津房地产管理数据库 总被引:1,自引:0,他引:1
从地理信息系统CIS的组成开始.提出该类系统的组织与管理方法,同时重点介绍了在现阶段开发该类系统时所使用的高端技术,最后对GIS系统的发展趋势作出分析与顶测。 相似文献
42.
Bedich ika Helena Bendov Ivan Macha
《Chemical Engineering and Processing: Process Intensification》2005,44(12):1312-1319
A procedure has been proposed for the estimation of the terminal falling velocity of non-spherical particles moving in a Carreau model fluid in the transition flow region. The procedure is based on a modification of the relationship formerly developed for the fall of spherical particles including the particle dynamic shape factor. The suitability of the proposed procedure has been confirmed by good agreement between experimental and calculated terminal falling velocity data. In the experiments, the terminal falling velocity of short cylinders and rectangular prisms in polymer solutions of different measure of shear thinning and elasticity has been measured. 相似文献
43.
Teerapong Senjuntichai Yasothorn Sapsathiarn 《Canadian Metallurgical Quarterly》2003,129(11):1330-1341
This paper considers the vertical vibrations of an elastic circular plate in a multilayered poroelastic half space. The plate is subjected to axisymmetric time–harmonic vertical loading and its response is governed by the classical thin-plate theory. The contact surface between the plate and the multilayered half space is assumed to be smooth and either fully permeable or impermeable. The half space under consideration consists of a number of layers with different thicknesses and material properties and is governed by Biot’s poroelastodynamic theory. The vertical displacement of the plate is represented by an admissible function containing a set of generalized coordinates. Contact stress and pore pressure jump are established in terms of generalized coordinates through the solution of flexibility equations based on the influence functions corresponding to vertical and pore pressure loading. Solutions for generalized coordinates are obtained by establishing the equation of motion of the plate through the application of Lagrange’s equations of motion. Selected numerical results are presented to portray the influence of various parameters on dynamic interaction between an elastic plate and a multilayered poroelastic half space. 相似文献
44.
Many problems consist in splitting a set of objects into different groups so that each group verifies some properties. In practice, a partitioning is often encoded by an array mapping each object to its group numbering. In fact, the group number of an object does not really matter, and one can simply rename each group to obtain a new encoding. That is what we call the symmetry of the search space in a partitioning problem. This property may be prejudicial for optimization methods such as evolutionary algorithms (EA) which require some diversity during the search. 相似文献
45.
A stochastic realization problem of a stationary stochastic process is re-visited, and a new stochastically balanced realization algorithm is derived in a Hilbert space generated by second-order stationary processes. The present algorithm computes a stochastically balanced realization by means of the singular value decomposition of a weighted block Hankel matrix derived by a “block LQ decomposition”. Extension to a stochastic subspace identification method explains how the proposed abstract algorithm is implemented in system identification. 相似文献
46.
Somsak Vanit-Anunchai Jonathan Billington Guy Edward Gallasch 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(1):29-56
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration
method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces
the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise
but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially
relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard,
the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we
introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the
peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP
to be analysed for larger parameter values.
Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree
University of Technology.
Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927). 相似文献
47.
ZnS, ZnSe, and CdTe polycrystals are experimentally investigated. Mechanisms are treated which restrict the thermal conductivity in samples prepared by recrystallization pressing and by deposition from the vapor phase and subjected to additional strain. Anomalies are observed on the temperature dependences of the thermal resistance of investigated samples, which are due to the special features of their phonon spectra and to the variation of the contribution made by longitudinal and transverse phonon branches to the heat transfer in the Debye temperature region and higher. 相似文献
48.
钻一口通过主采盐层的水平井与已完成的直井对接,形成连通井(形如“U”字),一口井注水溶解盐/芒硝矿,另一口井采出卤水,这是盐化工业对钻井提出的要求。针对水平对接盐井井身轨迹设计、着陆段、水平段的轨迹控制和连通技术,介绍了水平段侧钻时的钻井液技术。 相似文献
49.
50.
Abstract— The yield criterion is interpreted as defining the metric of the stress space. Hydrostatic stresses correspond to null geodesies. The plastic strain increment represents a normal projection of the increment undergone by a certain scalar function (hardening function) which depends only on the distance between stress points. This establishes a flow rule formally equivalent to the Prandtl-Reuss equations. Consideration of un-loading processes leads to the analysis of equivalent paths and to the definition of a generalized length or separation which provides a new representation of kinematic hardening. 相似文献