全文获取类型
收费全文 | 17830篇 |
免费 | 2011篇 |
国内免费 | 1461篇 |
专业分类
电工技术 | 1025篇 |
综合类 | 2311篇 |
化学工业 | 1339篇 |
金属工艺 | 386篇 |
机械仪表 | 924篇 |
建筑科学 | 1382篇 |
矿业工程 | 508篇 |
能源动力 | 429篇 |
轻工业 | 812篇 |
水利工程 | 423篇 |
石油天然气 | 339篇 |
武器工业 | 203篇 |
无线电 | 1779篇 |
一般工业技术 | 1549篇 |
冶金工业 | 314篇 |
原子能技术 | 250篇 |
自动化技术 | 7329篇 |
出版年
2024年 | 46篇 |
2023年 | 172篇 |
2022年 | 408篇 |
2021年 | 406篇 |
2020年 | 428篇 |
2019年 | 332篇 |
2018年 | 357篇 |
2017年 | 451篇 |
2016年 | 547篇 |
2015年 | 626篇 |
2014年 | 953篇 |
2013年 | 1087篇 |
2012年 | 1245篇 |
2011年 | 1425篇 |
2010年 | 1076篇 |
2009年 | 1353篇 |
2008年 | 1325篇 |
2007年 | 1560篇 |
2006年 | 1151篇 |
2005年 | 1118篇 |
2004年 | 878篇 |
2003年 | 788篇 |
2002年 | 607篇 |
2001年 | 500篇 |
2000年 | 417篇 |
1999年 | 356篇 |
1998年 | 230篇 |
1997年 | 236篇 |
1996年 | 193篇 |
1995年 | 168篇 |
1994年 | 142篇 |
1993年 | 120篇 |
1992年 | 124篇 |
1991年 | 81篇 |
1990年 | 65篇 |
1989年 | 69篇 |
1988年 | 39篇 |
1987年 | 38篇 |
1986年 | 23篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
We propose subspace distance measures to analyze the similarity between intrapersonal face subspaces, which characterize the variations between face images of the same individual. We call the conventional intrapersonal subspace average intrapersonal subspace (AIS) because the image differences often come from a large number of persons. An intrapersonal subspace is referred to as specific intrapersonal subspace (SIS) if the image differences are from just one person. We demonstrate that SIS varies significantly from person to person, and most SISs are not similar to AIS. Based on these observations, we introduce the maximum a posteriori (MAP) adaptation to the problem of SIS estimation, and apply it to the Bayesian face recognition algorithm. Experimental results show that the adaptive Bayesian algorithm outperforms the non-adaptive Bayesian algorithm as well as Eigenface and Fisherface methods if a small number of adaptation images are available. 相似文献
102.
本文介绍了用αβ谱仪系统同时测量αβ谱、实现Rn/Th子体补偿、确定超铀α核素气溶胶体积活度及人工放射性气溶胶总β体积活度的技术途径。利用RaA、RaC′a峰的二段时间计数可确定空气中RaA、RaB、RaC的气溶胶体积活度,相应的,也能给出RaB、RaC对总β计数的贡献。根据一般环境条件下的平衡比,用ThC′的。计数修正Th子体对αβ测量的影响。 ̄[239]pu或/和 ̄[241]Am人工核素的α计数,可通过两段时间分别扣除RaA、RaC′拖尾的方法确定;β计数分别扣除Rn/Th子体β贡献即可确定。在本文规定的测量条件下,对室内天然Rn子体水平在15Bq/m ̄3以下,超铀α核素气溶胶体积活度的测量下限可达到0.1Bq/m ̄3;即使在75Bq/m ̄3环境下,人工核素总β的测量下限也可达lBq/m ̄3以下。 相似文献
103.
Shao Zhiqing 《计算机科学技术学报》1993,8(2):59-65
In this paper we try to introduce a new approach to operational semantics of recursive programsby using ideas in the“priority method”which is a fundamental tool in Recursion Theory.In lieu ofmodelling partial functions by introducing undefined values in a traditional approach,we shall define apriority derivation tree for every term,and by respecting the rule“attacking the subterm of thehighest priority first”we define transition relations,computation sequences etc.directly based on astandard interpretation which includes no undefined value in its domain.Finally,we prove that ournew approach generates the same operational semantics as the traditional one.It is also pointed outthat we can use our strategy to refute a claim of Loeckx and Sieber that the opperational semanticsof recursive programs cannot be built based on predicate logic. 相似文献
104.
We describe the design and operation of a new high-pressure metal ebulliometer which can operate at pressures to at least 3 MPa in the range 220–400 K. Infinite-dilution activity coefficients are presented for the system CHF2Cl + CF3-CH, at 275 K and for the system CF3-CH2F + CH2F2, at 260, 230, and 300 K. The Wilson activity coellicient model and a virial coefficient model are applied to these systems, and the phase equilibrium conditions are calculated. The results are shown to agree well with predicted and with published measured values. The excess enthalpy is calculated and compared with results from a Peng Robinson equation of state. Vapor densities on the dew curves are given. 相似文献
105.
张蓓 《浙江工业大学学报》2007,(2)
本文对我国在明末和清代西学东渐过程中的图书翻译进行了梳理和剖析,总结了这一时期西学翻译的历史概况,阐述了东西文化交流中翻译图书的重要作用,以及历史上有识之士对于西学翻译的贡献。 相似文献
106.
基于语法的元程序设计系统的自动生成技术 总被引:4,自引:0,他引:4
本文提出一种基于语法的元程序设计系统的自动生成技术,并开发了一个元程序设计系统的自动生成系统A-MPS。元程序设计系统是一种以程序作为操作对象的有效的程序设计工具,并具有广泛的应用。 相似文献
107.
V. M. Kravtsov 《Cybernetics and Systems Analysis》2007,43(1):25-33
It is proved that, for any r ∈ { 2n, 2n + 1,…, 3n−2} and only for such r, the polytope of a three-index axial assignment problem
of order n, n ≥ 2, contains completely r-noninteger vertices (r-CNVs), i.e., vertices such that all their positive components
are fractional and their number equals r. For each r ∈ {2n, 2n + 1,…, 3n −2}, all the types of r-CNVs are characterized and
the combinatorial properties of completely r-noninteger vertices of the polytope are studied.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 1, pp. 33–44, January–February 2007. 相似文献
108.
109.
110.
Fluid catalytic cracking (FCC) is one of the most complex processes in the petroleum industry. The large degree of uncertainty in the kinetics of the cracking reactions and catalyst deactivation by coke deposition in the riser reactor are among several factors that contribute to the process complexity. The model developed by the authors (Ali and Rohani, 1995) is used lo investigate the effect of the three-lumped kinetic scheme (Weekman and Nace, 1970) and the four-lumped scheme (Lee ct ah, 1989) on the model predictability and reliability. The effect of changes in the catalyst circulation rate, gas oil feed rate, and oxygen feed concentration on various process variables is compared. It is shown that the three-lumped kinetic scheme, despite its extensive use in the literature (McFarlane et ah, 1993; Elnashaie and Elshishini, 1993; Theologos and Markatos, 1993; Arandes and de Lasa, 1992; Lopez-lsunza and Ruiz-Martinez, 1991), leads to erroneous results and should not be used in the dynamic simulation of the FCC units, 相似文献