全文获取类型
收费全文 | 229463篇 |
免费 | 24448篇 |
国内免费 | 13878篇 |
专业分类
电工技术 | 19457篇 |
技术理论 | 12篇 |
综合类 | 19040篇 |
化学工业 | 32316篇 |
金属工艺 | 14152篇 |
机械仪表 | 15520篇 |
建筑科学 | 19429篇 |
矿业工程 | 7740篇 |
能源动力 | 7000篇 |
轻工业 | 16519篇 |
水利工程 | 5737篇 |
石油天然气 | 11292篇 |
武器工业 | 2757篇 |
无线电 | 27678篇 |
一般工业技术 | 23343篇 |
冶金工业 | 9023篇 |
原子能技术 | 2775篇 |
自动化技术 | 33999篇 |
出版年
2024年 | 863篇 |
2023年 | 3712篇 |
2022年 | 7581篇 |
2021年 | 10689篇 |
2020年 | 8020篇 |
2019年 | 6174篇 |
2018年 | 6965篇 |
2017年 | 7918篇 |
2016年 | 7084篇 |
2015年 | 10604篇 |
2014年 | 13179篇 |
2013年 | 15600篇 |
2012年 | 18129篇 |
2011年 | 18979篇 |
2010年 | 17208篇 |
2009年 | 16198篇 |
2008年 | 15888篇 |
2007年 | 14902篇 |
2006年 | 13598篇 |
2005年 | 10820篇 |
2004年 | 7458篇 |
2003年 | 6079篇 |
2002年 | 5767篇 |
2001年 | 4974篇 |
2000年 | 4149篇 |
1999年 | 3396篇 |
1998年 | 2253篇 |
1997年 | 1842篇 |
1996年 | 1764篇 |
1995年 | 1432篇 |
1994年 | 1166篇 |
1993年 | 757篇 |
1992年 | 625篇 |
1991年 | 419篇 |
1990年 | 342篇 |
1989年 | 288篇 |
1988年 | 217篇 |
1987年 | 140篇 |
1986年 | 118篇 |
1985年 | 62篇 |
1984年 | 50篇 |
1983年 | 35篇 |
1982年 | 44篇 |
1981年 | 49篇 |
1980年 | 51篇 |
1979年 | 32篇 |
1977年 | 12篇 |
1976年 | 19篇 |
1959年 | 19篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
创新是企业发展不竭的动力,是增强企业竞争力的关键因素。本文就变频器企业在当前激烈的市场矗虿中,如何做好自主创新工作进行了探讨。在简要阐述自主创新的重要意义后,分析了变频器企业目前发展的现状和存在的问题。针对问题提出了变频器企业在开展自主创新时,可供参考的一些基本思路和途径。 相似文献
992.
993.
Kum‐Il Lee Yong‐Sik Yim Sang‐Wook Chung Jiaqiu Wei Jong Il Rhee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):1036-1045
A two‐dimensional (2D) spectrofluorometer was used to monitor various fermentation processes with recombinant E coli for the production of 5‐aminolevulinic acid (ALA). The whole fluorescence spectral data obtained during a process were analyzed using artificial neural networks, ie self‐organizing map (SOM) and feedforward backpropagation neural network (BPNN). The SOM‐based classification of the whole spectral data has made it possible to qualitatively associate some process parameters with the normalized weights and variances, and to select some useful combinations of excitation and emission wavelengths. Based on the classified fluorescence spectra a supervised BPNN algorithm was used to predict some of the process parameters. It was also shown that the BPNN models could elucidate some sections of the process's performance, eg forecasting the process's performance. Copyright © 2005 Society of Chemical Industry 相似文献
994.
渗透率是反映储层渗流能力的重要参数,目前对于单一储层的渗透率表征方法,通常是在岩心分析渗透率或测井解释渗透率的基础上进行厚度加权算术平均。这种方法对于均质的储层来说是适用的,但对于非均质严重的储层,不能准确反映该储层的实际渗流能力。本文提出一种应用可动流体体积权衡表征渗透率的方法,经实际资料验证,能较好地反映储层的实际渗透能力。 相似文献
995.
996.
Xinping Zhu Wei Qin Malik S. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2006,14(7):707-716
In multiprocessor-based system-on-chips (SOCs), optimizing the communication architecture is often as important as, if not more than, optimizing the computation architecture. While there are mature platforms and techniques for the modeling and evaluation of computation architectures, the same is not true for the communication architectures. A major challenge in modeling the communication architecture is managing the concurrency at multiple levels: at the operation level, multiple communication operations may be active at any time; at the microarchitecture level, several microarchitectural components may be operating in parallel. Further, it is important to be able to clearly specify how the operation-level concurrency maps to the microarchitectural-level concurrency. This paper presents a modeling methodology and a retargetable simulation framework which fill this gap. This framework seeks to facilitate the design space exploration of the communication subsystem through a rigorous modeling approach based on a formal concurrency model, the operation state machine (OSM). Our OSM-based modeling methodology enables the entire system including both the computation and communication architectures to be modeled in a single OSM framework. This allows us to develop a tool set that can synthesize cycle-accurate system simulators for multiprocessing-element SOC prototypes. We show that, by simulation, critical system information such as timing and communication patterns can be obtained and evaluated. Consequently, system-level design choices regarding the communication architecture can be made with high confidence in early stages of design. 相似文献
997.
In order to solve the problem that the high computational burden of the multiple signal classification algorithm of non-circular signal (NC-MUSIC) in direction-of-arrival (DOA) estimation,a novel computationally efficient DOA estimation algorithm based on subspace rotation technique was proposed.Firstly,the partitioning of noise subspace matrix and the subspace rotation technique (SRT) were used to construct a new reduced-dimension noise subspace.Then,the two-dimensional peak searching was converted to the one-dimensional peak searching on the basis of the separation of variables and the orthogonality between the new reduced-dimension noise subspace and the space spanned by the columns of the extended manifold matrix.The proposed algorithm can enhance the computational efficiency by means of the conversion of the two-dimensional peak searching into the one-dimensional peak searching and the removal of redundant computations.Theoretical analysis and simulation results show that the proposed algorithm can reduce the computational complexity to less than 5% as compared to NC-MUSIC algorithm on the premise of ensuring the accuracy of DOA estimation.Especially,the efficiency advantage of the proposed algorithm is more obvious in scenarios where the large numbers of sensors are required. 相似文献
998.
Thermal Radiative Properties of Xonotlite Insulation Material 总被引:1,自引:0,他引:1
X inxin ZHANG Gaosheng WEI Fan YU Department of Thermal Engineering University of Science & Technology Beijing Beijing China Professor 《热科学学报(英文版)》2005,14(3):281-283,253
Introduction Xonotlite-type calcium silicate (6CaO?6SiO2?H2O) is synthesized porous insulation material by hydrothermal processing with quartz powder and limestone as the raw material (with CaO/ SiO2≈1:1). Compared with fire- retardant fibre, xonotlite has more excellent insulating performance, such as low thermal conductivity, environment friendly, high intension, and wide applying temperature range, which has been emphasized in recent years by many scholars and widely used in many indu… 相似文献
999.
Hu P.J.-H. Tsang-Hsiang Cheng Chin-Ping Wei Chun-Hui Yu Chan A.L.F. Hue-Yu Wang 《IEEE transactions on systems, man, and cybernetics. Part A, Systems and humans : a publication of the IEEE Systems, Man, and Cybernetics Society》2007,37(4):481-492
Drug-related problems, particularly those that result from sub- or overtherapeutic doses of high-alert medications, have become a growing concern in clinical medicine. In this paper, we use a model-tree-based regression technique (namely, M5) and support vector machine (SVM) for regression to develop learning-based systems for predicting the adequacy of a vancomycin regimen. We empirically evaluate each system's accuracy in predicting patients' peak and trough concentrations in different clinical scenarios characterized by renal functions and regimen types. Our data consist of 1099 clinical cases that were collected from a major tertiary medical center in southern Taiwan. We also examine the use of bagging for enhancing the prediction power of the respective systems and include in our evaluation a salient one-compartment model for performance benchmark purposes. Overall, our evaluation results suggest that both M5 and SVM are significantly more accurate than the benchmark one-compartment model in predicting patients' peak and trough concentrations across all investigated clinical scenarios. M5 appears to benefit considerably from bagging, which has a positive but seemingly smaller effect on SVM. Taken together, our findings indicate supervised learning techniques that are capable of effectively supporting clinicians' use of vancomycin or similar high-alert drugs in their patient care and management. 相似文献
1000.
梅山3号高炉进入炉役后期,炉缸局部侵蚀严重,炉体冷却壁损坏加剧,威胁高炉安全、稳定生产.通过采取规整炉型、控制煤气流分布、加强技术管理、加强炉缸维护、抓好炉前渣铁处理等措施,做到了护炉和保产的统一. 相似文献