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   1113篇
  免费   13篇
  国内免费   3篇
电工技术   15篇
化学工业   237篇
金属工艺   38篇
机械仪表   17篇
建筑科学   42篇
矿业工程   7篇
能源动力   12篇
轻工业   130篇
水利工程   3篇
石油天然气   17篇
无线电   113篇
一般工业技术   152篇
冶金工业   173篇
原子能技术   8篇
自动化技术   165篇
  2021年   11篇
  2020年   12篇
  2019年   19篇
  2018年   34篇
  2017年   10篇
  2016年   19篇
  2015年   15篇
  2014年   16篇
  2013年   56篇
  2012年   19篇
  2011年   59篇
  2010年   51篇
  2009年   38篇
  2008年   52篇
  2007年   38篇
  2006年   26篇
  2005年   46篇
  2004年   28篇
  2003年   27篇
  2002年   28篇
  2001年   18篇
  2000年   12篇
  1999年   14篇
  1998年   38篇
  1997年   29篇
  1996年   24篇
  1995年   17篇
  1994年   15篇
  1993年   21篇
  1992年   28篇
  1991年   16篇
  1990年   18篇
  1989年   18篇
  1987年   8篇
  1986年   11篇
  1985年   16篇
  1984年   10篇
  1983年   8篇
  1982年   9篇
  1981年   10篇
  1980年   8篇
  1979年   13篇
  1977年   10篇
  1976年   17篇
  1974年   8篇
  1973年   8篇
  1971年   9篇
  1969年   7篇
  1963年   8篇
  1955年   11篇
排序方式: 共有1129条查询结果,搜索用时 0 毫秒
51.
We introduce a simple and practical method for repairing inconsistent databases. Given a possibly inconsistent database, the idea is to properly represent the underlying problem, i.e., to describe the possible ways of restoring its consistency. We do so by what we call signed formulae, and show how the ‘signed theory’ that is obtained can be used by a variety of off-the-shelf computational models in order to compute the corresponding solutions, i.e., consistent repairs of the database. *This paper is a revised and extended version of [9].  相似文献   
52.
We have studied the pulsed laser deposition (PLD) of Zr1-xCexO2 and Ce1-xLaxO2-x/2 initially to grow buffer layers for perovskite films deposited on Si, LaAlO3, SrTiO3 and MgO and then to produce tunneling barriers for cuprate or manganite heterostructures. On (1 0 0) Si, the deposition of Zr1-xCexO2 (x = 0.12) produces a smooth epitaxial layer (R RMS = 0.25/1m2), which allows the further deposition of high quality YBa2Cu3O7 (Tc 88 K) and La0.7Sr0.3MnO3 films. On the other hand, the use of Ce1-xLaxO2-x/2 (0 x 0.4) makes it possible to match the YBa2Cu3O7 and La0.7Sr0.3MnO3 layers to various substrates. The buffer layers are epitaxially grown with a 45° rotation of the in-plane axes with respect to those of the substrate, and the smoothness is high (R RMS = 0.25/1m2). In the case of an ultra-thin barrier (2.5 nm) of Ce1-xLaxO2-x/2 sandwiched in a La0.7Sr0.3MnO3, the out-of-plane mismatch of 2 induces distortions at the interface steps, which propagate into the topmost La0.7Sr0.3MnO3 layer. This is in contrast to the case of SrTiO3 barriers where an ideal crystal continuity in the growth direction is observed.  相似文献   
53.
We introduce a linear systolic array for the Longest Common Subsequence (LCS, for short) problem. We first present an array of m identical cells which computes the length of an LCS of two strings of length m and n, respectively, in linear time (i.e., in time proportional to m + n). Then we show that, by extending any cell with the systolic stack introduced by Guibas and Liang (1982), a new array can be designed to recover an LCS in linear time.  相似文献   
54.
55.
Pulmonary tuberculosis: primary tuberculosis, usually asymptomatic, represents the first infection and is shown by a parenchymal mostly mid-pulmonary focus and satellite lymphadenopathy. Postprimary pulmonary tuberculosis, mostly located in the upper fields may be caused by endogenous reinfection for reactivation of a hematogenous focus formed during primary infection or from exogenous reinfection. Extrapulmonary tuberculosis: it includes numerous forms mostly from hematogenous spread. Miliary tuberculosis may involve a number of organs and apparatus besides the lung. Tuberculous meningitis predominantly involves the base of the skull, the fluid is clear with hypoglycorrhachia and lymphocyte pleocytosis. Lymph node tuberculosis is generally unilateral and cervical. Tuberculous pleuritis is exudative or dry. Other forms of tuberculous serositis are pericarditis and peritonitis. Renal tuberculosis involves the medullaris and intestinal tuberculosis the ileocecum; tuberculous spondilitis (Pott's disease) involves the last dorsal vertebrae. Other forms are osteoarthritis, genital tract tuberculosis, pancreatitis, laryngitis, otitis.  相似文献   
56.
In this study, the effects of forearm static exercise were determined on local blood flow and oxygen consumption in 15 normal individuals (NL) and their responses were compared with ten patients in congestive heart failure (CHF). Forearm blood flow was determined by a plethysmographic technique before and during 15% of maximum voluntary contraction of the forearm. Regional arterial and venous oxygen contents were sampled and forearm oxygen consumption calculated by the Fick principle. At rest, forearm blood flow was less in patients with heart failure than in normal individuals; however, this was compensated for by an increased oxygen extraction, thus maintaining forearm oxygen consumption at a normal level. In contrast, during static exercise, forearm blood flow failed to rise normally with heart failure (NL 9.31; CHF 4.35 ml/min-100 ml, P less than 0.001) and the increased oxygen extraction was not sufficient to maintain a normal forearm oxygen consumption (NL .82; CHF .44 ml/min-100 ml, P less than 0.01). Therefore, patients with congestive heart failure demonstrate regional circulatory and metabolic abnormalities during static exercise that are comparable to those present during dynamic exercise. Because of a limited ability of their skeletal muscle resistance vessels to respond to dilator stimuli, they have an attenuation of their exercise hyperemia which leads to an earlier shift to anaerobic metabolism.  相似文献   
57.
Oxide layers grown on the surface provide an effective way of protecting metallic materials against corrosion for sustainable use in a broad range of applications. However, the growth of cavities at the metal/oxide interface weakens the adherence of the protective layer and can promote its spallation under service conditions, as observed for alumina layers formed by selective oxidation of aluminide intermetallic alloys used in high-temperature applications. Here we show that direct atomic-scale observations of the interface between an ultrathin protective oxide layer (alumina) grown on an intermetallic titanium aluminide substrate (TiAl) can be performed with techniques sensitive to the topmost atomic layers at the surface. Nanocavities resulting from the self-assembling of atomic vacancies injected at the interface by the growth mechanism of the protective oxide are observed for the first time, bringing new insight into the understanding of the fate of injected cavities in oxidation processes.  相似文献   
58.
A read-modify-write register for a set of functions F provides an operation that atomically (1) returns the variables current value v, and (2) replaces that value with f(v), where f is a function in F.A read-modify-write network is a distributed data structure that implements a concurrent, lock-free, low-contention read-modify-write register. For example, counting networks ([3]) are a family of read-modify-write networks that support atomic increments and decrements.We consider the problem of constructing read-modify-write networks for particular sets of functions. Of particular interest are the read-modify-write networks fetch&add, which add to the value an arbitrary number, and fetch&mul, which multiply the value by an arbitrary number.We identify a simple algebraic property of the function set F that requires any distributed read-modify-write implementation for F to have high latency. Any such network has sequential executions in which each token traverses a number of switching elements essentially linear in the number of processes. By contrast, there exist counting networks ([9, 18]) in which tokens traverse a logarithmic number of switches.We provide a matching upper bound for a large class of read-modify-write networks including fetch&add, fetch&mul, and related networks of interest.Received: 15 October 2002, Accepted: 15 May 2003, Published online: 6 February 2004Panagiota Fatourou: Partially supported by funds from the Program E. .E.A.E.K.II of the Greek Ministry of Education. Part of the work of theauthor was performed while at the Max-Planck Institut für Informatik,Saarbrücken, Germany, while at the Department of Computer Science,University of Toronto, Canada, and while visiting the Departmentof Computer Science, Brown University, Providence, USA.Maurice Herlihy: Partially supported by NSF grant 9912401.A preliminary version of this work appears in the Proceedings of the 15th International Symposium on DIStributed Computing, pp. 330-341, Lisbon, Portugal, October 2001. This work also appears as a brief announcement in the Proceedings of the 20th Annual ACM Symposium on Principles of Distributed Computing, Newport, Rhode Island, August 2001.  相似文献   
59.
"A sample of 423 psychotic patients from five veterans hospitals was observed and rated on behavior in the interview and on the ward. The intercorrelations between 55 of the rating scales were subjected to a multiple group factor analysis. The 11 oblique first order factors were interpreted." (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
60.
A series of 34 nitrogen-containing compounds with a wide range of basicities was examined under differential nonaqueous potentiometric conditions in acetophenone and nitrobenzene. These compounds could be resolved into five classes based on pKaand half-neutralization-potential (HNP) values. Asphaltenes isolated from the vacuum still overhead (VSO) and vacuum still bottoms (VSB) fractions of the H-coal process were titrated under similar conditions. The titration results of both asphaltenes indicated the presence of two classes of nitrogen-containing compounds, a titratable class of the pyridine-ring or aniline type and a nontitratable class.  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