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   32547篇
  免费   2517篇
  国内免费   36篇
电工技术   259篇
综合类   19篇
化学工业   7420篇
金属工艺   490篇
机械仪表   713篇
建筑科学   1031篇
矿业工程   59篇
能源动力   810篇
轻工业   6477篇
水利工程   341篇
石油天然气   155篇
武器工业   1篇
无线电   1506篇
一般工业技术   5282篇
冶金工业   5565篇
原子能技术   128篇
自动化技术   4844篇
  2024年   70篇
  2023年   342篇
  2022年   572篇
  2021年   1023篇
  2020年   833篇
  2019年   853篇
  2018年   1444篇
  2017年   1424篇
  2016年   1522篇
  2015年   1131篇
  2014年   1419篇
  2013年   2798篇
  2012年   2160篇
  2011年   2072篇
  2010年   1673篇
  2009年   1493篇
  2008年   1522篇
  2007年   1358篇
  2006年   914篇
  2005年   745篇
  2004年   694篇
  2003年   648篇
  2002年   596篇
  2001年   413篇
  2000年   328篇
  1999年   380篇
  1998年   1963篇
  1997年   1235篇
  1996年   767篇
  1995年   437篇
  1994年   333篇
  1993年   347篇
  1992年   111篇
  1991年   86篇
  1990年   75篇
  1989年   78篇
  1988年   94篇
  1987年   83篇
  1986年   75篇
  1985年   91篇
  1984年   79篇
  1983年   42篇
  1982年   53篇
  1981年   71篇
  1980年   70篇
  1978年   41篇
  1977年   115篇
  1976年   209篇
  1975年   39篇
  1973年   43篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
Food Science and Biotechnology - The enzymatic activity and partial characterization of proteases from Bromelia karatas fruits were evaluated and compared with Bromelia pinguin proteases. The...  相似文献   
74.
Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance.  相似文献   
75.
This paper discusses the convenience of using two-dimensional (2-D) coding techniques for the compression of electrocardiogram (ECG) signals. These signals present a very clear periodicity that can be exploited by the use of a 2-D time/frequency transform to decorrelate it as much as possible. A brief theoretical approach is given to justify the use of this technique, and a comparison is made between a 2-D and a one-dimensional (1-D) uniform quantization scenarios. The influence of the error as well as the frame size on the estimation of the fundamental period is studied.  相似文献   
76.
Presents an obituary and information about the life and accomplishments of Josef Maria Bro?ek. Born August 14, 1913, in the ancient town of Melnik, in central Bohemia, today the Czech Republic, Josef spent his childhood in Poland (Warsaw, 1913- 1915) and in Siberia (1915-1920). His education in Czechoslovakia culminated with a thesis on "Memory, Its Measurement and Structure" and a PhD awarded in June 1937. In the history of psychology, his lifetime project bore the title "Historiography of Psychology Around the World," and it covered about 20 geographical areas. Extensive attention was devoted to institutional and organizational developments as journals, academic settings, archives, museums, research groups, conferences, and institutes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
77.
Currently there are design barriers inhibiting the implementation of high-precision digital signal processing (DSP) objects with field programmable logic (FPL) devices. This paper explores overcoming these barriers by fusing together the popular distributed arithmetic (DA) method with the residue number system (RNS) for use in FPL-centric designs. The new design paradigm is studied in the context of a high-performance filter bank and a discrete wavelet transform (DWT). The proposed design paradigm is facilitated by a new RNS accumulator structure based on a carry save adder (CSA). The reported methodology also introduces a polyphase filter structure that results in a reduced look-up table (LUT) budget. The 2C-DA and RNS-DA are compared, in the context of a FPL implementation strategy, using a discrete wavelet transform (DWT) filter bank as a common design theme. The results show that the RNS-DA, compared to a traditional 2C-DA design, enjoys a performance advantage that increases with precision (wordlength).  相似文献   
78.
The gamma aminobutyric acid-A (GABAA) agonist, muscimol, the glutamate N-methyl-D-aspartate (NMDA) receptor antagonist, D-2-amino-5-phosphonopentanoic acid (AP5), and the inhibitor of the extracellularly regulated kinases (ERKs), UO 126, cause retrograde amnesia when administered to the hippocampus. In the present study, the authors found that they all cause retrograde amnesia for 1-trial inhibitory avoidance, not only when infused into the dorsal CA1 region of the hippocampus, but also when infused into the basolateral amygdala or the entorhinal, parietal, and posterior cingulate cortices. The posttraining time course of the effect of each drug was, however, quite different across brain structures. Thus, in all of them, NMDA receptors and the ERK pathway are indispensable for memory consolidation, and GABAA receptor activation inhibits memory consolidation: but in each case, their influence is interwoven differently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
79.
In this study chick embryo optic cups at HH stage 13 of development were analyzed under normal conditions and after inoculation with colchicine for 1, 2, 4, and 8 h. Several changes were seen after these periods of treatment: 1) modifications of the structure, with thicker regions in the cup and a general decrease in the total volume according to the duration of exposure to the drug (about 4 times less than normal, 5,035 x 10(3) microns 3 vs 1,334 x 10(3) microns 3 after 8 h of treatment); 2) enlargement of the ventricular cavity and its closure, due to failure of approximation of retinal and pigmentary layers; 3) failure of lens development, with delay and impairment of pit formation and deformation of all structures; lens volume was less than normal (about 4 times less, 2,148 x 10(3) microns 3 vs 658 x 10(3) microns 3 after 8 h of treatment); 4) a general segregation of the cells making up the structure, principally in the more active proliferating zones. The local alterations found are described.  相似文献   
80.
Pericardial effusion (PE) as a hypothyroidism associated sign, is something that can be found with relative frequency; nevertheless, cardiac tamponade (CT) as the first sign of this disease may be considered exceptional especially in young patients. We report a 31 years old woman with clinical symptoms and signs of CT that in the forward workshop was diagnosed of primary hypothyroidism as cause of the CT. We shortly describe the case and review the literature, emphasizing the importance of the knowledge of CT trigger factors in myxedematous PE, as well as its usual benign evolution with hormonal treatment, without recurrences of the CT after pericardiocentesis is performed. This justify a conservative approach, in spite of the slow resolution of the PE what can take as long as 1.5 years.  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