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   7557篇
  免费   1239篇
  国内免费   841篇
电工技术   812篇
综合类   808篇
化学工业   508篇
金属工艺   189篇
机械仪表   490篇
建筑科学   255篇
矿业工程   72篇
能源动力   110篇
轻工业   110篇
水利工程   114篇
石油天然气   341篇
武器工业   81篇
无线电   1829篇
一般工业技术   982篇
冶金工业   94篇
原子能技术   36篇
自动化技术   2806篇
  2024年   69篇
  2023年   175篇
  2022年   355篇
  2021年   309篇
  2020年   319篇
  2019年   268篇
  2018年   262篇
  2017年   253篇
  2016年   320篇
  2015年   375篇
  2014年   458篇
  2013年   513篇
  2012年   556篇
  2011年   582篇
  2010年   451篇
  2009年   476篇
  2008年   493篇
  2007年   521篇
  2006年   442篇
  2005年   404篇
  2004年   322篇
  2003年   288篇
  2002年   247篇
  2001年   206篇
  2000年   174篇
  1999年   142篇
  1998年   112篇
  1997年   92篇
  1996年   70篇
  1995年   78篇
  1994年   74篇
  1993年   53篇
  1992年   46篇
  1991年   22篇
  1990年   30篇
  1989年   29篇
  1988年   18篇
  1987年   10篇
  1986年   5篇
  1985年   4篇
  1984年   5篇
  1982年   3篇
  1981年   1篇
  1979年   1篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1957年   1篇
排序方式: 共有9637条查询结果,搜索用时 0 毫秒
1.
Using a comprehensive set of drop weight impact test data (h50) newly compiled from literature for 308 materials, a recent approach to predict impact sensitivities of nitro compounds is generalized to most explosive substances of interest. Compared to previous ones, this procedure is more thoroughly validated and exhibits a good predictive value. Furthermore, it yields new insight into the physical mechanisms involved, explaining for instance the unexpected desensitization of some oxygen-deficient triazoles upon nitration.  相似文献   
2.
From its foundation until 2004, ETRI has registered over 1,000 US patents. This letter analyzes the characteristics of these patents and addresses the explanatory factors affecting their citation counts. For explanatory variables, research team related variables, invention specific variables, and geographical domain related variables are suggested. Zero‐altered count data models are used to test the impact of independent variables. A key finding is that technological cumulativeness, the scale of invention, outputs in the electronic field, and the degree of dependence on the US technology domain positively affect the citation counts of ETRI‐invented US patents. The magnitude of international presence appears to negatively affect the citation counts of ETRI‐invented US patents.  相似文献   
3.
The main objective of the present work is to modify the traditional mapping method for the simulation of distributive mixing of multiphase flows in geometries involving moving parts such as, internal mixers or twin-screw extruders without a limitation on their geometrical periodicity. The periodicity condition, limits the results of traditional mapping method to tracking mapping mesh between specific discrete time intervals or distances for that geometry is repeated, hence, result is only for fixed orientation of rotors. Imaginary domain method is introduced to track mapping mesh from one state to the next free of geometrical periodicity limitations. In this work the method is introduced and its applicability and accuracy is discussed in details. A two-dimensional (2D) simulation of mixing of two Newtonian fluids with different viscosities in an intermeshing internal mixer is used as a test case study. In this example the key issues of ability to predict mixing state in details for all orientations of rotors is presented. To reduce diffusion errors of mapping method in the boundaries of the rotors, mapping mesh refinement technique that relies upon one single reference mesh is also presented.  相似文献   
4.
Many approaches have been proposed to enhance software productivity and reliability. These approaches typically fall into three categories: the engineering approach, the formal approach and the knowledge-based approach. But the optimal gain in software productivity cannot be obtained if one relies on only one of these approaches. This paper describes the work in knowledge-based software engineering conducted by the authors for the past 10 years. The final goal of the research is to develop a paradigm for software engineering which integrates the three approaches mentioned above. A knowledge-based tool which can support the whole process of software development is provided in this paper.  相似文献   
5.
柴油机低频排气噪声规律分析   总被引:4,自引:0,他引:4  
针对柴油机(4-85)低频排气噪声,对其产生机理、规律及其影响因素等作了理论计算、分析及实验。对低频排气噪声信号进行频域分析后可知,其主要由一系列离散的谐波组成,是以柴油机点火频率为基频的一种类周期性噪声,有可能应用有源噪声控制技术。  相似文献   
6.
S Chattopadhyay  P P Das 《Sadhana》1993,18(2):349-364
Reconstruction of an original continuous curve and the estimation of its parameters from the digitized version of the curve is a challenging problem, as quantization always causes some loss of information. In this paper, we have developed a scheme for reconstruction which is applicable to a class of curves having at the most two parameters. The class of curves for which the scheme works has also been characterized. We have shown that for one-parameter curves the exact domain of values of the parameter can be obtained. But in the two-parameter case, only the smallest rectangle containing the domain can be realised. The distinctive feature of our scheme is that it provides a unified approach to solve the reconstruction and the domain-finding problem for a class of curves.  相似文献   
7.
Parity space approach and H2 approach are two important fault detection approaches. This paper studies the relationship between these two approaches, which reveals frequency domain characteristics of the optimal solution of the parity space approach on the one side and provides a numerical solution of the H2-optimal design of residual generators on the other side.  相似文献   
8.
结构-波浪-海床耦合系统中大圆筒结构的波压力响应   总被引:5,自引:2,他引:3  
刘海笑  王仲捷 《水利学报》2003,(4):67-73,79
以沉入式大圆筒结构为对象,通过设计随机波浪水槽实验,测取了在单筒和连续筒两种结构型式、两种沉入深度和两种波谱输入下结构表面的动波压力分布。波面高度以及波压力历程均在领域进行分析。通过计算结构表面沿高程和沿环向的波压力谱及波压力传递函数,将单筒实测结果与基于线性绕射理论的解析解进行了比较,同时也详细对比了两种结构型式下的实测结果。文中汇报了在研究中获得的新发现及进行的相应分析,特别是在结构——波浪——海床动力相互作用下对波压力响应机理以及针对连续筒的研究,可为工程应用提供有价值的参考。  相似文献   
9.
在概率神经的一种改进模型-FDO网络的基础上,提出在设计网络收敛域时进一步考虑每一像素点周围8邻域的影响,对网络的作用函数加以修,使改进后的网络具有稳定性好且收敛速度快的优点。通过实验对改进前后网络的识别性能加以比较,证明改进后的网络特别适用于噪声图像的识别。  相似文献   
10.
应用铁电体极化反转的Orihara Ishibashi理论 ,讨论了圆形铁电薄膜和球形铁电体的开关电流以及开关时间对系统尺寸的依赖性。数值计算表明 ,不论是二维还是三维铁电系统 ,其铁电畴反转过程中产生的开关电流都随系统尺寸减少而下降 ,开关时间随系统尺寸减少而缩短  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