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   126929篇
  免费   5217篇
  国内免费   2428篇
电工技术   3314篇
技术理论   5篇
综合类   5320篇
化学工业   18656篇
金属工艺   7256篇
机械仪表   5527篇
建筑科学   5425篇
矿业工程   1671篇
能源动力   2290篇
轻工业   7972篇
水利工程   2146篇
石油天然气   2600篇
武器工业   291篇
无线电   13781篇
一般工业技术   21262篇
冶金工业   4741篇
原子能技术   781篇
自动化技术   31536篇
  2024年   258篇
  2023年   892篇
  2022年   1578篇
  2021年   2001篇
  2020年   1630篇
  2019年   1389篇
  2018年   15745篇
  2017年   14892篇
  2016年   11304篇
  2015年   2643篇
  2014年   2639篇
  2013年   3257篇
  2012年   6273篇
  2011年   12569篇
  2010年   11077篇
  2009年   8188篇
  2008年   9340篇
  2007年   10138篇
  2006年   2493篇
  2005年   3185篇
  2004年   2359篇
  2003年   2188篇
  2002年   1424篇
  2001年   845篇
  2000年   947篇
  1999年   879篇
  1998年   721篇
  1997年   524篇
  1996年   521篇
  1995年   403篇
  1994年   330篇
  1993年   241篇
  1992年   214篇
  1991年   149篇
  1990年   120篇
  1989年   68篇
  1988年   94篇
  1987年   60篇
  1986年   52篇
  1985年   46篇
  1984年   50篇
  1980年   35篇
  1968年   47篇
  1966年   43篇
  1965年   47篇
  1959年   41篇
  1958年   39篇
  1957年   37篇
  1955年   66篇
  1954年   69篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
杜世俊 《贵州化工》2002,27(3):49-51
通过对尿素包装工艺的不断改进,提高了尿素粒度、减少粉尘含量,效果明显。  相似文献   
102.
利用有效折射率和修正的有效折射率方法对矩形光波导的损耗作了简单有效的分析,并且计算出了纵向传播系数和衰减系数的大小。  相似文献   
103.
We consider the problem of rescheduling trains in the case where one track of a railway section consisting of two tracks in opposing directions is closed due to construction activities. After presenting an appropriate model for this situation we derive a polynomial algorithm for the subproblem of finding an optimal schedule with minimal latenesss if the subsequences of trains for both directions outside the construction site are fixed. Based on this algorithm we propose a local search procedure for the general problem of finding good schedules and report test results for some real world instances. Received: December 8, 1999 / Accepted: May 2, 2001  相似文献   
104.
Three interesterified vegetable oils (IVOs) prepared from palm, cottonseed, and olive oil, respectively, have been studied for application to Frankfurters. Beef fat (10%) was replaced by one of the IVOs at 20, 60 or 100%. Fatty acid composition of the lipid fraction in the Frankfurters and saturated/unsaturated ratios were established for all batches. We found that total or partial replacement of beef fat by IVOs did not lead to significant changes in appearance, colour, texture, flavour or sensory score. We conclude that IVOs may be successfully applied as beef fat substitutes in Frankfurters.  相似文献   
105.
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms.  相似文献   
106.
107.
108.
In real speech, not like lexical words (LWs), prosodic words (PWs) are basic rhythmic units. The naturalness of a Text-to-Speech (TTS) system is directly influenced by the segmentation of the PWs. Most of the PWs are the combination of several LWs. In this paper, three Lexical Combination Models are proposed to combine LWs into PWs, including a Directed Acyclic Graph Model, a Segmentation Model and a Markov Model (MM). To cope with the situation where some long LWs should be segmented into two or more PWs, a Lexical Split Model (LSM) is applied to the long LWs. Experimental results prove that relatively constant results with various training data can be obtained from a MM. The Transformation-Based Error Driven Learning (TBED) algorithm, for its high performance of individual property, is applied in combination with the MM to improve the precision of PW segmentation. Experiments show that among the three proposed models, the MM combined with TBED and LSM, leads to the best performance, in which a precision of 93.00% and a recall of 93.23% are achieved. The perception test indicates that by using PWs as the lowest prosodic units a speech sounds more natural and acceptable than by using LWs. This paper is supported by NSFC Project (60503071); 973 Natural Basic Research Program of China (2004CB318102); Postdoctor Science Foundation of P. R. China (20070420275).  相似文献   
109.
The physical gestures that operate music instruments are responsible for the qualities of the sound being produced in a performance. Gestural information is thereby crucial for a model of music performance, paired with a model of sound synthesis where this information is applied. The highly constrained nature of performers gestures makes this task suitable to be modeled via a constraint-based approach, coupled with a strategy aimed at maximizing the gestural comfort of performers. We illustrate the problem representation, the search strategy and a validation of the model against human performance.  相似文献   
110.
Approximately 80% of the international transport of goods is carried on by means of ships. A large portion of the transport capacity is represented by Roll-on-Roll-off (RoRo) ships. Especially in Europe this is a relevant potential for the RoRo segment. Consequently, the design and construction of RoRo ships plays an increasing role for German shipyards and their suppliers. In order to make the loading and unloading procedure of trailer economically more competitive, ship owners would like to improve the lashing of trailers on the ship. On the basis of a multibody system formalism, a software tool has been developed which allows for an optimization of the loading of trailers on RoRo ships. Commemorative Contribution.  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