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   1912篇
  免费   41篇
  国内免费   6篇
电工技术   12篇
综合类   1篇
化学工业   225篇
金属工艺   22篇
机械仪表   43篇
建筑科学   90篇
矿业工程   6篇
能源动力   55篇
轻工业   191篇
水利工程   14篇
石油天然气   4篇
无线电   207篇
一般工业技术   265篇
冶金工业   625篇
原子能技术   26篇
自动化技术   173篇
  2023年   15篇
  2021年   26篇
  2020年   25篇
  2019年   28篇
  2018年   21篇
  2017年   22篇
  2016年   33篇
  2015年   16篇
  2014年   35篇
  2013年   74篇
  2012年   53篇
  2011年   78篇
  2010年   54篇
  2009年   36篇
  2008年   55篇
  2007年   69篇
  2006年   62篇
  2005年   51篇
  2004年   42篇
  2003年   47篇
  2002年   48篇
  2001年   46篇
  2000年   36篇
  1999年   47篇
  1998年   155篇
  1997年   119篇
  1996年   72篇
  1995年   42篇
  1994年   43篇
  1993年   30篇
  1992年   22篇
  1991年   20篇
  1990年   20篇
  1989年   17篇
  1988年   19篇
  1987年   15篇
  1986年   22篇
  1985年   24篇
  1984年   27篇
  1983年   13篇
  1982年   19篇
  1981年   18篇
  1980年   24篇
  1979年   13篇
  1978年   13篇
  1977年   33篇
  1976年   42篇
  1975年   14篇
  1974年   18篇
  1972年   11篇
排序方式: 共有1959条查询结果,搜索用时 31 毫秒
111.
Fischer plots are plots of accommodation (derived by calculating cumulative departure from mean cycle thickness) versus cycle number or stratigraphic distance (proxies for time), for cyclic carbonate platforms. Although many workers have derived programs to do this, there are currently no published, easily accessible programs that utilize Excel. In this paper, we present an Excel-based spreadsheet program for Fischer plots, illustrate how the data are input, and how the resulting plots may be interpreted. The plots can be used to derive periods of increased accommodation, shown on the plots as a rising limb (which commonly matches times of more open marine, subtidal parasequence development). Times of decreased accommodation, shown on the plots as a falling limb, generally are coincident with thin, shallow, peritidal parasequences.  相似文献   
112.
Looks at the data and metrology tools developed by The National Institute of Standards and Technology for the research community, including common middleware for distributed sensor data acquisition and processing.  相似文献   
113.
Zeiosis     
  相似文献   
114.
Dietary supplements on soy based foods and beverages are increasingly gaining prominence all over the world. In this study, liquid chromatography coupled with positive electrospray ionisation tandem mass spectrometry (LC-ESI-MS) and diode array detection was used for the quantitation and characterisation of isoflavones in fermented and unfermented soymilk made from soy protein isolate SUPRO 590. Bifidobacterium animalis ssp. lactis Bb12 was used for the fermentation of soymilk. The isoflavones were found to produce characteristic radical ions as well as molecules of H2O, CO2, a sugar unit, and an alcohol through collision-induced fragmentation. Product ion fragments revealed unique fragmentation pathways for each isoflavone compound. Characteristic fragmentation of different isoflavones were unequivocally identified and differentiated. The occurrence of aldehydes such as pentanal, ethanal and methanal was shown to be specifically linked with isoflavone aglycones, daidzein, genistein and glycitein, respectively. Main glycosides such as genistin, daidzin and glycitin as well as the acetyl-, and malonyl forms also showed respective aglycone ions in their spectra fragmentation. Thus positive ion fragmentation was important in the absolute confirmation of isoflavones and to reveal the occurrence of other related compounds such as aldehydes in soymilk.  相似文献   
115.
Conclusions Mechanical interlocking of topcoat with the nonpolar TPO surface can be achieved through the use of an adhesion promoter, namely a chlorinated poly(olefin). The type of CPO used, in addition to the types of solvents and heat effects used, can substantially influence the degree of adhesion/cohesion obtained within the CPO.TPO system. Heat histories, TPO molding variations, CPO types, including solvent and resin variations, and topcoat (basecoat/clearcoat) chemistries were all found to influence the adhesion/cohesion of the painted TPO assembly. Surface damage resistance was found to mirror the effects of adhesion as described earlier. Control of the interphase formed between the TPO substrate and the subsequent topcoat layers becomes increasingly important if one wishes to maintain damage resistance within the painted composite. Testing methodology development, namely “gouge” chip, abrasion, and scratch resistance, is paramount in predicting performance under specified loads. Through interpretation of data received in the various testing methodologies, the mechanical properties of the topcoat/substrate combination may be varied to obtain the performance required in a variety of applications. The Roy W. Tess Award in Coatings is presented annually by the Division of Polymeric Materials: Science and Engineering (PMSE) in recognition of outstanding contributions to coatings science and technology. Funded by a grant to the Division by Dr. and Mrs. Roy W. Tess, the purpose of the award is to encourage interest and progress in coatings and recognize significant contributions to the field. Dr. Rose Ryntz, Manager and Staff Technical Fellow with Visteon Corporatiom, Dearborn, MI, received the award from Dr. Paul Valint, Jr., Chair of the PMSE Division in September 2003 during the 226th meeting of the American Chemical Society in New York, NY. Dr. Ryntz's award address followed the Award Symposium. The following papers were presented at that symposium.  相似文献   
116.
A universal transformer for two-dimensional separable linear transforms in image coding is proposed. It is not restricted to fast transforms, and switching between transforms only requires writing the appropriate constants into an internal RAM. Look-up tables are used to reduce computational complexity. The linear transform properties are exploited to reduce the memory requirements by decomposing the input vector into smaller arrays and into bit planes. The input is pipelined into parallel data paths. An implementation example on a single gate array with existing technology achieves real-time transformation of 8 × 8 blocks, with area requirements of around 38K gates.  相似文献   
117.
Consider approximate (lossy) matching of a source string ~P, with a random codebook generated from reproduction distribution Q, at a specified distortion d. Previous work determined the minimum coding rate R1=R(P, Q, d) for this setting. We observe that for a large word length and with high probability, the matching codeword is typical with a distribution Q1 which is different from Q. If a new random codebook is generated ~Q1, then the source string will favor codewords which are typical with a new distribution Q2, resulting in a minimum coding rate R2=R(P, Q1, d), and so on. We show that the sequences of distributions Q1, Q 2,... and rates R1, R2,..., generated by this procedure, converge to an optimum reproduction distribution Q*, and the rate-distortion function R(P, d), respectively. We also derive a fixed rate-distortion slope version of this natural type selection process. In the latter case, an iteration of the process stochastically simulates an iteration of the Blahut-Arimoto (1972) algorithm for rate-distortion function computation (without recourse to prior knowledge of the underlying source distribution). To strengthen these limit statements, we also characterize the steady-state error of these procedures when iterating at a finite string length. Implications of the main results provide fresh insights into the workings of lossy variants of the Lempel-Ziv algorithm for adaptive compression  相似文献   
118.
119.
120.
A span task was developed to assess the amount of information infants could hold in short-term memory. In this task, infants were presented with up to 4 items in succession and then tested for recognition by successively pairing each item with a novel one. A large sample of full-terms and low-birth-weight preterms (  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