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   30956篇
  免费   5099篇
  国内免费   1571篇
电工技术   3357篇
综合类   3641篇
化学工业   1150篇
金属工艺   1073篇
机械仪表   3540篇
建筑科学   1600篇
矿业工程   791篇
能源动力   1085篇
轻工业   623篇
水利工程   655篇
石油天然气   765篇
武器工业   516篇
无线电   3342篇
一般工业技术   2912篇
冶金工业   521篇
原子能技术   160篇
自动化技术   11895篇
  2025年   59篇
  2024年   598篇
  2023年   516篇
  2022年   814篇
  2021年   896篇
  2020年   1089篇
  2019年   972篇
  2018年   894篇
  2017年   1101篇
  2016年   1246篇
  2015年   1299篇
  2014年   1746篇
  2013年   1865篇
  2012年   2068篇
  2011年   2236篇
  2010年   1689篇
  2009年   1802篇
  2008年   1880篇
  2007年   2190篇
  2006年   1969篇
  2005年   1683篇
  2004年   1393篇
  2003年   1269篇
  2002年   997篇
  2001年   875篇
  2000年   785篇
  1999年   673篇
  1998年   567篇
  1997年   460篇
  1996年   360篇
  1995年   348篇
  1994年   273篇
  1993年   184篇
  1992年   165篇
  1991年   132篇
  1990年   112篇
  1989年   102篇
  1988年   87篇
  1987年   36篇
  1986年   30篇
  1985年   32篇
  1984年   20篇
  1983年   15篇
  1982年   20篇
  1981年   12篇
  1980年   14篇
  1979年   4篇
  1978年   5篇
  1977年   9篇
  1975年   5篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Anionic copolymerizations of styrene (M1) with excess 1-(4-dimethyl-aminophenyl)-1-phenylethylene (M2) were conducted in benzene at 25°C for 24h, using sec-butyllithium as initiator. Narrow molecular weight distribution copolymers with M?;n = 16.1 × 103 g/mol (M?w/M?n = 1.04) and 38.2 × 103g/mol (M?w/M?n = 1.05), and 24 and 38 moles of M2 per macromolecule, respectively, were characterized by size exclusion chromatography, 1H NMR spectroscopy and DSC. The monomer reactivity ratio, r1 = 5.6, was obtained from the copolymer composition at complete consumption of M1, assuming that the rate constant k22 =0,i.e. r2 =0. The polymers exhibited Tg values of 128 and 119°C, respectively, which correspond to an estimated Tg = 217°C for the hypothetical homopolymer of M2.  相似文献   
2.
In arc welding processes, because of the complexity and nonlinearity of heat transfer phenomena, it is often difficult to design an effective control system based upon an exact mathematical model. In this paper, a self-organizing fuzzy control method is proposed to obtain a uniform weld quality by regulation of the surface temperature at a desired level. The proposed control system is designed to comprise a combined structure of the fuzzy SOC with conventional PD control for improving the system's stability. The control experiments show that the proposed controller guarantees a uniform weld quality for various welding conditions.  相似文献   
3.
Concurrent reading while writing revisited   总被引:1,自引:0,他引:1  
A modification is proposed to Peterson's construction of 1-writern-reader multivalued atomic shared variableusingn+2 multivalued safe variables and some boolean atomic variables. The resulting construction is elegant and is simpler than the original one. K. Vidyasankar received B.E. (Elec. Engg.) from Thiagarajar College of Engineering, Madurai, M. Tech. from I.I.T. Kanpur, India, and Ph.D. in Computer Science from University of Waterloo, Canada. He is now an Associate Professor in Computer Science at Memorial University of Newfoundland, Canada. His research interests include concurrency control and recovery in database systems, concurrency in interprocess communication, design and analysis of algorithms, and graph theory.A prelininary version of this paper, under the title Improving Peterson's Construction of 1-Writern-Reader Multivalued Atomic Register, appears in the Proc. 26th Annual Allerton Conference on Communication, Control, and Computing, University of Illinois at Urbana Champaign, September 1988, pp 693–700  相似文献   
4.
文章采用模糊规划的方法证明了期望放出体在放矿中的合理性,从而使放矿这个复杂的过程能方便地采用数学手段来处理。同时说明了如何在崩落法矿山利用期望体来解决实际生产中的放矿问题。  相似文献   
5.
Bio-cryptography is an emerging security technology which combines cryptography with biometrics. A good bio-cryptosystem is required to protect the privacy of the relevant biometric data as well as achieving high recognition accuracy. Fingerprints have been widely used in bio-cryptosystem design. However, fingerprint uncertainty caused by distortion and rotation during the image capturing process makes it difficult to achieve a high recognition rate in most bio-cryptographic systems. Moreover, most existing bio-cryptosystems rely on the accurate detection of singular points for fingerprint image pre-alignment, which is very hard to achieve, and the image rotation transformation during the alignment process can cause significant singular point deviation and minutiae changes. In this paper, by taking full advantage of local Voronoi neighbor structures (VNSs), e.g. local structural stability and distortion insensitivity, we propose an alignment-free bio-cryptosystem based on fixed-length bit-string representations extracted from modified VNSs, which are rotation- and translation-invariant and distortion robust. The proposed alignment-free bio-cryptosystem is able to provide strong security while achieving good recognition performance. Experimental results in comparison with most existing alignment-free bio-cryptosystems using the publicly-available databases show the validity of the proposed scheme.  相似文献   
6.
Due to the complexity of the machine tool structure and the cutting process, the dynamics of machining processes are still not completely understood. This is especially true due to the demand of high-speed machining to increase productivity. In order to model and control these complex processes, new approaches, which can represent complex phenomenon combined with learning ability, are needed. The combined neural–fuzzy approach appears to be ideally suited for this purpose. In this paper, the recently developed fuzzy adaptive network (FAN) is used to model surface roughness in turning operations. The FAN network has both the learning ability of neural network and linguistic representation of complex, not well-understood, vague phenomenon. Furthermore, it can continuously improve the initially obtained rough model based on the daily operating data. To illustrate this approach, a model representing the influences of machining parameters on surface roughness is established and then the model is verified by the use of the results of pilot experiments. Finally, a comparison with the results based on statistical regression is provided.  相似文献   
7.
A.  C.M. Takemura  O. Colliot  O. Camara  I.   《Pattern recognition》2008,41(8):2525-2540
Segmenting the heart in medical images is a challenging and important task for many applications. In particular, segmenting the heart in CT images is very useful for cardiology and oncological applications such as radiotherapy. Although the majority of methods in the literature are designed for ventricle segmentation, there is a real interest in segmenting the heart as a whole in this modality. In this paper, we address this problem and propose an automatic and robust method, based on anatomical knowledge about the heart, in particular its position with respect to the lungs. This knowledge is represented in a fuzzy formalism and it is used both to define a region of interest and to drive the evolution of a deformable model in order to segment the heart inside this region. The proposed method has been applied on non-contrast CT images and the obtained results have been compared to manual segmentations of the heart, showing the good accuracy and high robustness of our approach.  相似文献   
8.
为了帮助顾客从众多对症的非处方药中选出最满意的药品,提出了开发1个基于Web的非处方药满意度评价系统。系统根据顾客提供的典型症状,采用疾病与症状相结合的选药策略,查找出所有对症的非处方药,并以药品安全性、疗效、稳定性、易用性、价格作为评价因素,根据顾客的关注角度和关注程度确定各因素权重,用模型b=W·R对对症药品进行满意度评价,按满意度高低依次推荐。经实际应用,系统推荐准确度在70%以上。  相似文献   
9.
Huan Huang 《Information Sciences》2010,180(19):3806-3813
This paper shows that the Zadeh’s extensions of sendograph-metric-continuous fuzzy-valued functions are sendograph-metric-continuous fuzzy functions.  相似文献   
10.
Robust design (RD) and tolerance design (TD) have received much attention from researchers and practitioners for more than two decades, and a number of methodologies for modeling and optimizing the RD and TD processes have been studied. However, there is ample room for improvement. Because most existing research considers RD and TD as separate research fields, the primary objective of this paper is to develop a sequential robust–tolerance design method to jointly determine the best factor settings and the closed-form solutions for the optimal specification limits. We then apply the proposed method to a destructive quality characteristic. Finally, a case study and sensitivity analyses are performed for verification purposes, and further studies are discussed.  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