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   29362篇
  免费   1117篇
  国内免费   110篇
电工技术   381篇
综合类   229篇
化学工业   5419篇
金属工艺   642篇
机械仪表   597篇
建筑科学   1048篇
矿业工程   97篇
能源动力   951篇
轻工业   3980篇
水利工程   247篇
石油天然气   153篇
武器工业   6篇
无线电   2275篇
一般工业技术   4213篇
冶金工业   6304篇
原子能技术   238篇
自动化技术   3809篇
  2024年   55篇
  2023年   162篇
  2022年   547篇
  2021年   841篇
  2020年   555篇
  2019年   619篇
  2018年   702篇
  2017年   795篇
  2016年   757篇
  2015年   580篇
  2014年   873篇
  2013年   1473篇
  2012年   1294篇
  2011年   1648篇
  2010年   1210篇
  2009年   1246篇
  2008年   1130篇
  2007年   987篇
  2006年   788篇
  2005年   858篇
  2004年   922篇
  2003年   831篇
  2002年   805篇
  2001年   705篇
  2000年   549篇
  1999年   534篇
  1998年   2049篇
  1997年   1334篇
  1996年   934篇
  1995年   610篇
  1994年   483篇
  1993年   538篇
  1992年   222篇
  1991年   283篇
  1990年   233篇
  1989年   196篇
  1988年   213篇
  1987年   157篇
  1986年   169篇
  1985年   185篇
  1984年   134篇
  1983年   91篇
  1982年   119篇
  1981年   123篇
  1980年   118篇
  1979年   95篇
  1978年   75篇
  1977年   141篇
  1976年   233篇
  1975年   84篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Conservation of food products depends on product quality and packaging suitability. The objective of this work was to develop and evaluate the antimicrobial efficiency of natamycin‐incorporated film in the production process of Gorgonzola cheese. It aims to optimize the production process and increase shelf‐life and food safety for the consumer. Films with different concentrations of natamycin were produced and tested in Gorgonzola cheeses to evaluate its efficiency against Penicillium roqueforti on the cheese surface. Films with 2 and 4% natamycin presented satisfactory results for fungus inhibition and the amount of natamycin released to the cheese was below that allowed by the legislation. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
73.
An efficient method for computing the fields of large scatterers is presented. The current is expanded in terms of modes defined as complex exponential functions. The modes are represented efficiently by means of spline functions. Analytical expressions have been obtained to compute efficiently the fields due to the current modes.  相似文献   
74.
A new approach to study the fracture of quasi-brittle materials is introduced: the design and testing of model materials. By model material is understood a material with enlarged microstructure and which material parameters, such as stacking and mechanical properties of particles and cohesion force, can be fully controlled. In this paper a first example to the model materials approach is presented, consisting in 5 mm steel particles bonded in a precise stacking with an epoxy-based glue. It is shown how it is possible to correlate the different fracture mechanisms and ultimate peak load of the model material to the particle pair force and to the fracture process zone size. It is also seen how a quasi-brittle behaviour is produced in the presence of mechanisms that induced the crack to shift fracture planes, that is, in presence of energy dissipative mechanisms.  相似文献   
75.
Multirate adaptive filters have numerous advantages such as low computational load, fast convergence, and parallelism in the adaptation. Drawbacks when using multirate processing are mainly related to aliasing and reconstruction effects. These effects can be minimized by introducing appropriate problem formulation and employing sophisticated optimization techniques. In this paper, we propose a formulation for the design of a filter bank which controls the distortion level for each frequency component directly and minimizes the inband aliasing and the residual aliasing between different subbands. The advantage of this problem formulation is that the distortion level can be weighted for each frequency depending on the particular practical application. A new iterative algorithm is proposed to optimize simultaneously over both the analysis and the synthesis filter banks. This algorithm is shown to have a unique solution for each iteration. For a fixed distortion level, the proposed algorithm yields a significant reduction in both the inband aliasing and the residual aliasing levels compared to existing methods applied to the numerical examples.  相似文献   
76.
The crystal structure of CaMgGeO4 is described. CaMgGeO4, Mr = 200.9, orthorhombic, Pnam, A = 11.285(5) Å, B = 5.016(2) Å, C = 6.435(2) Å, V = 364.36 Å3, Dx = 3.664 Mg/m3.λ(MoKa = 0.71069 Å, F(000) = 384, room temperature, final R = 0.045 for 1752 observed reflections. The structure is isomorphous with CaMgSiO4 (monticellite).  相似文献   
77.
Venezuela's vast natural resource base has largely shaped the nation's economic and energy-use patterns. Major opportunities exist for improving the efficiency of energy use in Venezuela and, consequently, restraining the growth of energy-related carbon emissions. This paper presents a detailed report of one potential development path for Venezuela and estimates the ensuing levels of energy demand and CO2 emissions associated with pursuing this path through the year 2025. The results indicate that by adopting a development strategy that incorporates structural changes in the economy, fuel-switching measures and improved end-use efficiencies, Venezuela can introduce energy efficiency and carbon restraints as part of its economic development process.  相似文献   
78.
79.
This work reports the results obtained with the application of High Order Boltzmann Machines without hidden units to construct classifiers for some problems that represent different learning paradigms. The Boltzmann Machine weight updating algorithm remains the same even when some of the units can take values in a discrete set or in a continuous interval. The absence of hidden units and the restriction to classification problems allows for the estimation of the connection statistics, without the computational cost involved in the application of simulated annealing. In this setting, the learning process can be sped up several orders of magnitude with no appreciable loss of quality of the results obtained.  相似文献   
80.
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