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   3104篇
  免费   142篇
  国内免费   8篇
电工技术   33篇
综合类   4篇
化学工业   885篇
金属工艺   48篇
机械仪表   61篇
建筑科学   109篇
矿业工程   5篇
能源动力   69篇
轻工业   158篇
水利工程   21篇
石油天然气   3篇
无线电   500篇
一般工业技术   460篇
冶金工业   531篇
原子能技术   5篇
自动化技术   362篇
  2023年   16篇
  2022年   41篇
  2021年   81篇
  2020年   53篇
  2019年   124篇
  2018年   141篇
  2017年   85篇
  2016年   74篇
  2015年   38篇
  2014年   141篇
  2013年   134篇
  2012年   101篇
  2011年   159篇
  2010年   95篇
  2009年   108篇
  2008年   135篇
  2007年   131篇
  2006年   130篇
  2005年   103篇
  2004年   88篇
  2003年   65篇
  2002年   92篇
  2001年   65篇
  2000年   63篇
  1999年   64篇
  1998年   175篇
  1997年   100篇
  1996年   77篇
  1995年   57篇
  1994年   41篇
  1993年   46篇
  1992年   47篇
  1991年   40篇
  1990年   25篇
  1989年   33篇
  1988年   14篇
  1987年   21篇
  1986年   21篇
  1985年   15篇
  1984年   13篇
  1983年   23篇
  1982年   24篇
  1981年   17篇
  1980年   18篇
  1979年   10篇
  1977年   12篇
  1976年   23篇
  1975年   12篇
  1974年   8篇
  1972年   8篇
排序方式: 共有3254条查询结果,搜索用时 15 毫秒
1.
<正>最近,陶氏公司在2019上海国际车展期间介绍了一系列应对汽车行业新挑战的创新产品和解决方案,帮助汽车厂商化挑战为机遇。以"创新为你,续写经典"为主题,陶氏公司从用户体验出发,与车企紧密合作,为消费者提供"声、形、味"俱佳的驾乘体验。陶氏聚氨酯业务部大中华区销售总监陈飞介绍说:"当今汽车行业面临众多挑战,安全性、轻量化、舒适性和环保性要求不断推  相似文献   
2.
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients.  相似文献   
3.
A Distributed Virtual Environment (DVE) system offers a computer-generated virtual world in which individuals located at different places in the physical world can interact with one another. In order to achieve real-time response for a large user base, DVE systems need to have a scalable architecture. In this paper, we present the design of a grid-enabled service oriented framework for facilitating the construction of scalable DVE systems on computing grids. A service component called “gamelet” is proposed, whose distinctive mark is its high mobility for supporting dynamic load sharing. We propose a gamelet migration protocol which can ensure the transparency and efficiency of gamelet migration, and an adaptive gamelet load-balancing (AGLB) algorithm for making gamelet redistribution decisions at runtime. The algorithm considers both the synchronization costs of the DVE system and network latencies inherent in the grid nodes. The activities of the users and the heterogeneity of grid resources are also considered in order to carry out load sharing more effectively. We evaluate the performance of the proposed mechanisms through a multiplayer online game prototype implemented using the Globus toolkit. The results show that our approach can achieve faster response times and higher throughputs than some existing approaches. This research is supported in part by the China National Grid project (863 program) and the HKU Foundation Seed Grant 28506002.  相似文献   
4.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment.  相似文献   
5.
PURPOSE: To examine the management and possible causes of primary valve malfunction of the Krupin eye valve with disk. METHODS: The authors reviewed the results of 113 patients undergoing implantation of the Krupin eye valve with disk and identified eight patients with primary valve malfunction requiring surgical revision. RESULTS: Valve revision involved manipulation (n = 1 case), explantation of the malfunctioning valve and implantation of a new valve (n = 2), and amputation of the valve (n = 5). Six of eight patients had final intraocular pressures of < 21 mmHg on one or no medications at a mean interval of 15.9 months (range 5-36) after surgical revision. Transient postoperative hypotony was noted in three patients and chronic hypotony with loss of light perception in one patient. One explanted valve was examined and found to have partially fused leaflets. CONCLUSIONS: Surgical revision in cases of primary valve malfunction of the Krupin eye valve with disk may be accomplished relatively safely with an acceptable level of postoperative complications. The etiology of primary valve malfunction may be related to the sterilization process and prolonged storage before implantation.  相似文献   
6.
In this paper, we consider a system with K single-antenna client users, n/sub B/ base stations (each base station has n/sub R/ antennas), as well as a centralized controller. A client user could be associated with a single base station at any time. All the base stations operate at the same frequency and have optimal multiuser detection per base station which cancels intracell interference only. We consider a general problem of uplink macroscopic resource management where the centralized controller dynamically determines an appropriate association mapping of the K users with respect to the n/sub B/ base stations over a macroscopic time scale. We propose a novel analytical framework for the above macroscopic scheduling problems. A simple rule is to associate a user with the strongest base station (camp-on-the-strongest-cell), and this has been widely employed in conventional cellular systems. However, based on the optimization framework, we found that this conventional approach is in fact not optimal when multiuser detection is employed at the base station. We show that the optimal macroscopic scheduling algorithm is of exponential complexity, and we propose a simple greedy algorithm as a feasible solution.  相似文献   
7.
An attempt is made to extend schemes for classifying the behaviour of gas—solid contacting modes and other two-phase systems. The regime diagram approach of Reh (1971) is modified and extended to cover the operating regions of common reactors and contactors where a gas flows upwards through a bed of solids including fixed and moving packed beds, conventional fluidized beds, circulating beds, spouted beds, and pneumatically conveyed suspensions. New boundaries are proposed between groups A and B and between groups B and D of the Geldart (1972, 1973) powder classification scheme. These boundaries reflect more recent data and allow the classification scheme to be used for gases other than air and for temperatures and pressures other than atmospheric.  相似文献   
8.
9.
A 78-year-old Chinese woman presented with recurrent postprandial abdominal pain. Computerised tomography revealed a small bowel tumour causing volvulus of a segment of the small bowel. Laparotomy confirmed an extraluminal ileal tumour with partial volvulus of the involved small bowel segment. Small bowel resection was done. Histological and ultrastructural studies confirmed a gastrointestinal autonomic nerve tumour. We review the medical literature on this rare tumour.  相似文献   
10.
Pass-transistor adiabatic logic with NMOS pull-down configuration   总被引:13,自引:0,他引:13  
Liu  F. Lau  K.T. 《Electronics letters》1998,34(8):739-741
A new low power adiabatic logic family, pass-transistor adiabatic logic with NMOS pull-down configuration, is presented. For a 2:1 multiplexer, a power saving of ~800% is achieved, compared to a 2N-2N2P logic circuit at 20 MHz. Compared to pass-transistor adiabatic logic using single power-clock supply (PAL), the `tri-state' problem is solved, while power consumption is comparable. A four phase sinusoidal clock power supply is employed in the new logic family, which facilitates pipelining hence leading to higher throughput, compared to PAL  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