全文获取类型
收费全文 | 63187篇 |
免费 | 7188篇 |
国内免费 | 4948篇 |
专业分类
电工技术 | 5384篇 |
技术理论 | 2篇 |
综合类 | 8935篇 |
化学工业 | 4082篇 |
金属工艺 | 1330篇 |
机械仪表 | 4066篇 |
建筑科学 | 5627篇 |
矿业工程 | 1132篇 |
能源动力 | 1657篇 |
轻工业 | 8266篇 |
水利工程 | 1702篇 |
石油天然气 | 1699篇 |
武器工业 | 772篇 |
无线电 | 6732篇 |
一般工业技术 | 6803篇 |
冶金工业 | 2062篇 |
原子能技术 | 913篇 |
自动化技术 | 14159篇 |
出版年
2024年 | 349篇 |
2023年 | 1086篇 |
2022年 | 2153篇 |
2021年 | 2243篇 |
2020年 | 2302篇 |
2019年 | 2038篇 |
2018年 | 2005篇 |
2017年 | 2385篇 |
2016年 | 2549篇 |
2015年 | 2620篇 |
2014年 | 3580篇 |
2013年 | 3953篇 |
2012年 | 4674篇 |
2011年 | 4895篇 |
2010年 | 3564篇 |
2009年 | 3711篇 |
2008年 | 3655篇 |
2007年 | 4154篇 |
2006年 | 3693篇 |
2005年 | 3219篇 |
2004年 | 2625篇 |
2003年 | 2212篇 |
2002年 | 1779篇 |
2001年 | 1531篇 |
2000年 | 1312篇 |
1999年 | 1117篇 |
1998年 | 921篇 |
1997年 | 771篇 |
1996年 | 694篇 |
1995年 | 624篇 |
1994年 | 534篇 |
1993年 | 405篇 |
1992年 | 359篇 |
1991年 | 281篇 |
1990年 | 266篇 |
1989年 | 223篇 |
1988年 | 159篇 |
1987年 | 105篇 |
1986年 | 63篇 |
1985年 | 63篇 |
1984年 | 51篇 |
1983年 | 45篇 |
1982年 | 45篇 |
1981年 | 18篇 |
1980年 | 38篇 |
1979年 | 31篇 |
1965年 | 17篇 |
1964年 | 21篇 |
1963年 | 17篇 |
1957年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
关于Vague集的模糊熵及其构造 总被引:17,自引:3,他引:14
本文分析了Vague集的性质,给出了将Vague集变换为Fuzzy集的转换函数,并讨论了其性质。分析了关于Vague集的模糊熵的直观特性,在此基础上我们给出了Vague集的模糊熵的定义。最后给出了一个关于Vague集的模糊熵的构造方法。 相似文献
102.
AN EXTENDED MODELING OF TIDE-WAVE MOTION 总被引:1,自引:1,他引:0
Zhang Qing hua Xu Hao Qu Yuan yuan First Institute of Oceanography State Oceanic Administration Qingdao China Key Laboratory of Marine Science Numerical Modeling State Oceanic Administration Qingdao China 《水动力学研究与进展(B辑)》2001,(3)
1 . INTRODUCTIONTostudythemotionofthetide waves,theshallowwaterequations ,i.e .theverticalintergra tionofthecontinuityequationandmomentumequa tion ,isconsideredasthegoverningequations.Byaboveequationstwoequationsrelatedtothehorizon talfluxofthetide currentsa… 相似文献
103.
提出了由一个变迹IDT叉指换能器和一个均匀IDT组成的SAW滤波器简化衍射频响的计算方法,即将均匀IDT简化成单根指计算其衍射频响。该方法与未简化衍射频响的计算方法相比,计算量大为减小,前者约为后者的(N为均匀IDT的指对数)。并给出了一个实例,用未简化与简化方法分别计算了其衍射频响,结果表明,两者符合得较好。 相似文献
104.
105.
A Method of Combined SHPB Technique and BP Neural Network to Study Impact Response of Materials 总被引:2,自引:0,他引:2
Abstract: A new method combining the split Hopkinson pressure bar (SHPB) technique with the back-propagation (BP) neural network program is proposed. By this method, the treated strain wave signals become smooth with less noises induced by the transverse inertia. Moreover, the dynamic rate-dependent constitutive behaviour of materials can be identified, without any pre-assumption of a constitutive model. It is found that by taking the experimentally measured data of strain, strain rate and time as 'input' and the corresponding data of stress as 'output' of the BP neural network, the dynamic constitutive behaviour with internal damage or phase transformation evolution is easy to be identified, where the time could represent either the internal damage evolution or phase transformation process accompanied with the deformation process. It is emphasised that the data learnt by the BP neural network must include both loading and unloading processes, if the whole loading and unloading response is to be correctly predicted. The comparisons between the predictions and experimental results are in good agreement for both polyamide (PA) polymer (as an example of nonlinear viscoelastic materials) and Ti–Ni alloy (as an example of superelastic materials with stress-induced phase transformation). 相似文献
106.
Daniela D'Amato Maria Rosaria Corbo Matteo Alessandro Del Nobile & Milena Sinigaglia 《International Journal of Food Science & Technology》2006,41(10):1152-1157
In enology, alcoholic fermentation is a complex process involving several mechanisms. Slow and incomplete alcoholic fermentation is a chronic problem for the wine industry and factors leading to sluggish and stuck fermentations have been extensively studied and reviewed. The most studied cause of sluggish and stuck fermentation is the nitrogen content limitation. Nevertheless, other factors, such as temperature of fermentation and sugar concentration can affect the growth of yeasts. In this study we modelled the yeast growth‐cycle in wine model system as a function of temperature, sugar and ammonium concentrations; the individual effects and the interaction of these factors were analysed by means of a quadratic response surface methodology. Cell concentrations and weight loss were monitored in the whole wine fermentation process. The results of central composite design show that lower is the availability of nitrogen, higher is the cell growth rate; moreover, initial nitrogen concentration also influences survival time of Saccharomyces cerevisiae. 相似文献
107.
ZHANG Zu-fan DU Hui-ping JIANG Ze Chongqing University of Posts Telecommunications Chongqing China University of Electronic Science Technology of China Chengdu China 《中国邮电高校学报(英文版)》2006,13(4):29-33
1 Introduction The calling dwell time characteristic is critical for the user network planning and deployment, e.g., global system for mobile communications (GSM), as well as the next generation wireless multimedia networks, such as, the currently standar… 相似文献
108.
MuShanxiang JiXiaoli LiMing LiXingguo 《电子科学学刊(英文版)》2003,20(6):407-413
Linear Modulated Frequency (LMF) Costas Stepped Frequency Radar (SFR) signal is introduced. Its ambiguity function is derived and analyzed in detail and its feasibility is validated in theory. The scheme of the proposed signal processing is also presented. The results of theoretic analysis and simulation show that, by using the proposed signal and increasing the bandwidth of the total stepped frequency, the ambiguity sidelobe is well suppressed and the range-velocity coupling in the stepped frequency radar is also greatly weakened. 相似文献
109.
Reports an error in "Temporal Encoding in Fear Conditioning Revealed Through Associative Reflex Facilitation" by Derick H. Lindquist and Thomas H. Brown (Behavioral Neuroscience, 2004[Apr], Vol 118[2], 395-402). The article contained several errors. On page 396, second paragraph, the sentence beginning on line 6 should read as follows: "Having a stable baseline is critical for studies of reflex facilitation because the experimental designs invariably entail repetitive CR testing, if only to achieve reasonable statistical power (see Choi et al., 2001b; Lindquist & Brown, 2004)." On page 400, the first heading should read as follows: "Comparison of New and Old Reflex Facilitation Procedures." On page 400, the first sentence under the abovementioned heading should read as follows: "We decided not to use the original measure of reflex facilitation, developed by J. S. Brown et al. (1951), because it suffers from severe interpretational limitations, elaborated in detail elsewhere (Choi et al., 2001b; Leaton & Cranney, 1990; Lindquist & Brown, 2004)." (The following abstract of the original article appeared in record 2004-12681-016.) Temporal encoding in Pavlovian fear conditioning was examined through conditional facilitation of the short-latency (Rl) component of the rat eyeblink reflex. Rats were fear-conditioned to a tone conditional stimulus (CS) with either a 3- or 9-s interstimulus interval (ISI) between CS onset and the onset of the grid-shock unconditional stimulus (US). Rl facilitation was tested over 2 days, in counterbalanced order, at a latency of 3 s and 9 s from CS onset. CS-produced Rl facilitation, the conditional response (CR), was 3-4 times larger when the test latency equaled the conditioning ISI. These results, coupled with the known neurophysiology of Rl facilitation, suggest that this CR could disclose differences in the time course of CS-generated output from the amygdala when driven by cortical versus subcortical CS-CR pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
110.
小浪底水电厂位于多泥沙的黄河干流上,水轮机活动导叶会因磨损过大而严重漏水,在水轮机的设计上必须考虑这个因素;同时,为适应混水发电,小浪底水电厂机组采用了筒阀。文中介绍了筒阀的结构特点、功能及控制原理等,并对其在现场的实际应用情况进行了分析。 相似文献