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   137634篇
  免费   20455篇
  国内免费   3208篇
电工技术   5237篇
技术理论   4篇
综合类   4379篇
化学工业   34599篇
金属工艺   5695篇
机械仪表   7638篇
建筑科学   7165篇
矿业工程   1337篇
能源动力   4353篇
轻工业   14222篇
水利工程   1727篇
石油天然气   2770篇
武器工业   486篇
无线电   19929篇
一般工业技术   26806篇
冶金工业   6720篇
原子能技术   1375篇
自动化技术   16855篇
  2024年   283篇
  2023年   1372篇
  2022年   2472篇
  2021年   3856篇
  2020年   3864篇
  2019年   5213篇
  2018年   5565篇
  2017年   5972篇
  2016年   6679篇
  2015年   6969篇
  2014年   8123篇
  2013年   10784篇
  2012年   9160篇
  2011年   9876篇
  2010年   8726篇
  2009年   8421篇
  2008年   7942篇
  2007年   6984篇
  2006年   6626篇
  2005年   5644篇
  2004年   4755篇
  2003年   4577篇
  2002年   4646篇
  2001年   3950篇
  2000年   3436篇
  1999年   2601篇
  1998年   2606篇
  1997年   1868篇
  1996年   1590篇
  1995年   1242篇
  1994年   1054篇
  1993年   849篇
  1992年   617篇
  1991年   539篇
  1990年   456篇
  1989年   386篇
  1988年   334篇
  1987年   246篇
  1986年   182篇
  1985年   152篇
  1984年   122篇
  1983年   79篇
  1982年   60篇
  1981年   61篇
  1980年   47篇
  1979年   40篇
  1978年   32篇
  1977年   39篇
  1976年   69篇
  1975年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Cases of isolated hepatic tuberculosis (TB) are rare. The diagnosis is often delayed or missed because of nonspecific symptoms and laboratory findings. Besides, the disease is extremely rare even in a country where TB is an alarming public health problem. This report demonstrates the difficulty in correctly diagnosing local hepatic TB. We report the case of a 62‐year‐old male patient with end‐stage renal disease treated with hemodialysis, who developed 2 months of abdominal distension and general anorexia, with hyperechoic hepatic lesions on ultrasound. Computed tomography suspected multiple liver tumors. The liver biopsy finally led to the diagnosis of TB of the liver without other involvements. We conclude that isolated hepatic TB is one of the rare forms of extrapulmonary TB in dialysis patients. A greater awareness of this rare clinical entity may prevent needless surgical interventions.  相似文献   
62.
63.
64.
65.
与传统比例-积分-微分(PID)控制方法相比,滑模控制(SMC)方法可以比较容易地将不确定性纳入控制器设计中,从而增强系统的鲁棒性。探索了SMC技术在运载器主动段姿态控制中的工程应用,首先通过分析基于趋近律的SMC系统,提出了降低不连续切换项系数的需求,然后研究了基于干扰上界的SMC方法。三通道小偏差仿真结果验证了两种方法的控制效果,表明第2种控制器的鲁棒性更好,稳态误差小,同时发动机喷管摆角需求较小。  相似文献   
66.
Machine Learning - We consider the problem of learning a binary classifier from only positive and unlabeled observations (called PU learning). Recent studies in PU learning have shown superior...  相似文献   
67.
Microsystem Technologies - A color-laser printing system consisting of a tandem laser scanning unit uses four laser diodes and a single polygonal mirror (PM) to expose light onto four...  相似文献   
68.
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research.  相似文献   
69.
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   
70.
This paper addresses a tracking problem for uncertain nonlinear discrete‐time systems in which the uncertainties, including parametric uncertainty and external disturbance, are periodic with known periodicity. Repetitive learning control (RLC) is an effective tool to deal with periodic unknown components. By using the backstepping procedures, an adaptive RLC law with periodic parameter estimation is designed. The overparameterization problem is overcome by postponing the parameter estimation to the last backstepping step, which could not be easily solved in robust adaptive control. It is shown that the proposed adaptive RLC law without overparameterization can guarantee the perfect tracking and boundedness of the states of the whole closed‐loop systems in presence of periodic uncertainties. In addition, the effectiveness of the developed controller is demonstrated by an implementation example on a single‐link flexible‐joint robot. Copyright © 2014 John Wiley & Sons, Ltd.  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