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   1452篇
  免费   28篇
  国内免费   8篇
电工技术   21篇
化学工业   383篇
金属工艺   30篇
机械仪表   22篇
建筑科学   61篇
矿业工程   3篇
能源动力   39篇
轻工业   133篇
水利工程   9篇
无线电   120篇
一般工业技术   291篇
冶金工业   98篇
原子能技术   11篇
自动化技术   267篇
  2024年   10篇
  2023年   13篇
  2022年   16篇
  2021年   28篇
  2020年   30篇
  2019年   30篇
  2018年   33篇
  2017年   37篇
  2016年   50篇
  2015年   33篇
  2014年   61篇
  2013年   92篇
  2012年   89篇
  2011年   80篇
  2010年   81篇
  2009年   76篇
  2008年   90篇
  2007年   64篇
  2006年   49篇
  2005年   58篇
  2004年   55篇
  2003年   46篇
  2002年   44篇
  2001年   15篇
  2000年   23篇
  1999年   18篇
  1998年   36篇
  1997年   18篇
  1996年   20篇
  1995年   13篇
  1994年   20篇
  1993年   18篇
  1992年   10篇
  1991年   13篇
  1990年   11篇
  1989年   11篇
  1988年   8篇
  1987年   11篇
  1986年   10篇
  1985年   11篇
  1984年   9篇
  1983年   5篇
  1982年   11篇
  1979年   4篇
  1978年   3篇
  1976年   4篇
  1975年   5篇
  1974年   3篇
  1971年   2篇
  1968年   2篇
排序方式: 共有1488条查询结果,搜索用时 0 毫秒
941.
A physical simulation was carried out to investigate the realistic experiment of bulk solidifying the Zn-Bi hyper-monotectic alloy under various compound electric-magnetic fields(CEMF).For this experiment,two crucial parameters determinate the cast microstructure,the one is electric-magnetic force(EMF)and the other is the frequency of AC current.Results show that the minor phase could be mixed in the other phase from the initial layered structure when the EMF above a specific value under fixed frequency,and the average diameter of minor phase droplet decreases with increasing EMF.The evolution of the liquid phases structure is reasonable agree with the realistic experiment of Zn-Bi hyper-monotectic alloy,which suggests that the mechanism revealed by the physical simulation could represent the one in the realistic experiment.  相似文献   
942.
943.
Sarcomatoid carcinoma of head and neck mucosal sites is a rare high-grade malignancy that may cause diagnostic and therapeutic controversies. A characteristic of this entity consistently reported but not entirely validated is its relative radioresistance and the general belief is that surgery is the treatment of choice. The objective of this retrospective study was to determine if patients treated with radiation for early glottic sarcomatoid carcinoma had worse outcomes than those achieved with irradiation for the more typical squamous cell carcinoma. Twenty-eight cases of early stage (T1-T2) sarcomatoid carcinoma of the larynx treated with definitive doses of megavoltage irradiation between 1969 and 1995 at The University of Texas M. D. Anderson Cancer Center form the cohort for this analysis. All pathologic material was reviewed to confirm the diagnosis. All tumors manifested spindle cell features with marked cytomorphologic abnormalities characteristic of this entity. Sixteen tumors (57%) had the more typical polypoid gross morphology of sarcomatoid carcinoma. Twenty-one patients (75%) were staged T1 and seven patients (25%) had stage T2 disease. All patients were treated with small laryngeal fields, median size 20 cm2, and to a median dose of 65 Gy. Follow-up ranged from 1.5 to 24 years (median, 10 years). Four patients (14%) had local disease recurrence, and all had salvage total laryngectomies and remained free of local disease. The 5-year actuarial local control rates for patients with T1 and T2 lesions were 94% and 54%, respectively. Only one patient developed regional and distant disease. The 10-year actuarial disease-specific and overall survival rates were 92% and 63%, respectively. Patients with early stage sarcomatoid carcinoma of the glottis treated with radiation had similar control rates to irradiated patients with similar volume disease with the more typical squamous cell carcinoma. The authors contend that the histologic diagnosis of sarcomatoid carcinoma by itself should not influence the decision to treat a patient with early stage glottic disease with irradiation.  相似文献   
944.
    
We show that in a free F-algebra endowed with a strict order we can associate with a complete rewriting system in the sense of Knuth-Bendix an equivalent proper (minimal) complete system. Furthermore, if the complete system is compatible with a strict order, then the equivalent proper complete system is unique.  相似文献   
945.
    
In this paper, we derive time-minimal systolic arrays for Gaussian elimination and the Algebraic Path Problem (APP) that use a minimal number of processors. For a problem of size n, we obtain an execution time T(n) = 3n −1 using A(n) = n2/4+O(n) processors for Gaussian elimination, and T(n) = 5n −2 and A(n) = n3/+O(n) for the APP.  相似文献   
946.
         下载免费PDF全文
In this paper, we define the notion of biRFSA which is a residual finate stateautomaton (RFSA) whose the reverse is also an RFSA. The languages recognized bysuch automata are called biRFSA languages. We prove that the canonical RFSA of abiRFSA language is a minimal NFA for this language and that each minimalNFA for this language is a sub-automaton of the canonical RFSA. This leadsto a characterization of the family of biRFSA languages.In the second part of this paper, we define the family of biseparable automata. We prove that every biseparable NFA is uniquely minimal among all NFAs recognizinga same language, improving the result of H. Tamm and E.Ukkonen for bideterministic automata. https://doi.org/10.1051/ita:2008022  相似文献   
947.
Previous functional MRI findings have indicated that a premotor-parietal network is involved in the perceptual processing of sequential information. Given that premotor functions have traditionally been restricted to behaviors requiring motor or sensorimotor computations, the goal of the present patient study was to further investigate whether the lateral premotor cortex is critical in purely perceptual sequencing. Patients with either ventral premotor or inferior parietal lesions, in addition to patients with prefrontal lesions and age- and gender-matched healthy controls, were tested during the processing of temporal, object-specific, and spatial sequences. Results revealed that premotor patients as well as parietal patients showed significantly higher error rates than did healthy controls on all sequence tasks. In contrast, prefrontal patients showed no behavioral deficits. These findings support the significance of the ventrolateral premotor cortex, in addition to parietal areas, in nonmotor (attentional) functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
948.
A two-dimensional mathematical model developed for vacuum-contact drying of wood was adapted to simulate superheated steam vacuum drying. The moisture and heat equations are based on the water potential concept whereas the pressure equation is formulated considering unsteady-state mass conservation of dry air. A drying test conducted on sugar maple sapwood in a laboratory vacuum kiln was used to infer the convective mass and heat transfer coefficients through a curve fitting technique. The average air velocity was 2.5 m s-1 and the dry-bulb temperature varied between 60 and 66°C. The ambient pressure varied from 15 to 11 kPa. Simulation results indicate that heat and mass transfer coefficients are moisture content dependent. The simulated drying curve based on transfer coefficients calculated from boundary layer theory poorly fits experimental results. The functional relation for the relative permeability of wood to air is a key parameter in predicting the pressure evolution in wood in the course of drying. In the case of small vacuum kilns, radiant heat can contribute substantially to the total heat transfer to the evaporative surface at the early stages of drying. As for conventional drying, the air velocity could be reduced at the latter stage of drying with little or no change to the drying rate.  相似文献   
949.
The main objective of this study is to investigate cutting parameter effects of surface roughness in a lathe dry boring operation. A full factorial design was used to evaluate the effect of six (6) independent variables (cutting speed, feed rate, depth of cut, tool nose radius, tool length and type of boring bar) and their corresponding two-level interactions. In this experiment, the dependant variable was the resulting fast cut surface roughness (R,). In order to perform all possible variable combinations, a total of 216 cuts were.

The results revealed that using short tool length always provide good surface roughness and that only slight improvement on surface roughness can be achieved by properly controlling the cutting parameters and/or the type of boring bar used. The results also revealed that using a long tool length may results in vibration that could be efficiently controlled by the use of a damped boring bar. With such a long tool length, the cutting variables become important factors to control in order to significantly improve surface roughness results with both types of boring bars. A prediction model is proposed for each types of boring bar. Both models are highly significant, p<0.00001, with coefficients of determination of 0.56 and 0.57 for a standard boring bar and a damped boring bar, respectively.  相似文献   

950.
The chemical oxidation of sucrose, isomaltulose and methyl isomaltuloside is described, with special focus on the use of the NaOCl–TEMPO oxidizing system.  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