首页 | 官方网站   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   262篇
  免费   2篇
工业技术   264篇
  2017年   2篇
  2016年   2篇
  2013年   6篇
  2012年   6篇
  2011年   3篇
  2010年   4篇
  2008年   3篇
  2007年   5篇
  2006年   2篇
  2005年   6篇
  2003年   2篇
  2002年   3篇
  2001年   10篇
  2000年   6篇
  1999年   10篇
  1998年   30篇
  1997年   29篇
  1996年   10篇
  1995年   8篇
  1994年   10篇
  1993年   10篇
  1992年   3篇
  1991年   3篇
  1990年   4篇
  1989年   4篇
  1988年   4篇
  1987年   4篇
  1986年   9篇
  1985年   2篇
  1984年   2篇
  1982年   6篇
  1981年   2篇
  1979年   2篇
  1978年   3篇
  1977年   6篇
  1976年   7篇
  1975年   8篇
  1974年   4篇
  1973年   1篇
  1972年   1篇
  1971年   2篇
  1970年   2篇
  1969年   3篇
  1968年   1篇
  1967年   2篇
  1966年   1篇
  1963年   1篇
  1957年   1篇
  1955年   1篇
  1954年   1篇
排序方式: 共有264条查询结果,搜索用时 0 毫秒
1.
A patient who developed a mixed neuroendocrine carcinoma and adenocarcinoma at the site of a previous long-standing ileostomy is reported. The neuroendocrine features are documented by both ultrastructural and immunocytochemical findings. Carcinoma arising in an ileostomy site is rare but has been recorded in patients with long-standing ileostomies after colectomy for chronic inflammatory bowel disease, as in this patient. Neuroendocrine carcinoma developing in this setting apparently has not been described before, however.  相似文献   
2.
3.
Advances in technology and changes in necessary workplace skills have made the ability to think critically more important than ever before, yet there is ample evidence that many adults consistently engage in flawed thinking. Numerous studies have shown that critical thinking, defined as the deliberate use of skills and strategies that increase the probability of a desirable outcome, can be learned in ways that promote transfer to novel contexts. A 4-part empirically based model is proposed to guide teaching and learning for critical thinking: (a) a dispositional component to prepare learners for effortful cognitive work, (b) instruction in the skills of critical thinking, (c) training in the structural aspects of problems and arguments to promote transcontextual transfer of critical-thinking skills, and (d) a metacognitive component that includes checking for accuracy and monitoring progress toward the goal. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
4.
This study was undertaken to determine the effect of various lipid emulsions on the hepato-biliary system in rats. Rats were randomly divided into six groups and infused continuously for 48 hr with either long-chain triglycerides (LCT), medium-chain triglycerides (MCT) or a mixture of MCT and LCT. One group infused with physiological saline solution served as controls. Throughout this period the rats received a fat free dietad libitum. During the last hour of lipid infusion bile was collected for determination of bile flow and composition. Subsequently, the rats were sacrificed and the morphology and lipid content of the liver determined. Only LCT lipid emulsions induced morphological changes and increased liver cholesterol content. In two rats infused with radiolabeled LCT, no labeled cholesterol was found in the liver, indicating that the excess hepatic cholesterol level may originate from enhanced cholesterol mobilization to the liver. Biliary cholesterol and phospholipid concentrations in LCT-treated rats were also elevated, as was the lithogenic index, whereas the other emulsions had no such effects. None of the emulsions affected the plasma liver function tests or bile flow. We therefore conclude that the lithogenicity of the bile in rats is directly related to the lipid components of the total parenteral nutrition and the type of triglyceride infused.  相似文献   
5.
Consider a distributed system N in which each agent has an input value and each communication link has a weight. Given a global function, that is, a function f whose value depends on the whole network, the goal is for every agent to eventually compute the value f (N). We call this problem global function computation. Various solutions for instances of this problem, such as Boolean function computation, leader election, (minimum) spanning tree construction, and network determination, have been proposed, each under particular assumptions about what processors know about the system and how this knowledge can be acquired. We give a necessary and sufficient condition for the problem to be solvable that generalizes a number of well-known results (Attyia et al. in J ACM 35(4):845–875, 1988; Yamashita and Kameda in IEEE Trans Parallel Distrib Syst 7(1):69–89, 1996; Yamashita and Kameda in IEEE Trans Parallel Distrib Syst 10(9):878–887, 1999). We then provide a knowledge-based (kb) program (like those of Fagin et al. (Reasoning about knowledge, MIT Press, Cambridge, 1995, Distrib Comput 10(4):199–225, 1997)) that solves global function computation whenever possible. Finally, we improve the message overhead inherent in our initial kb program by giving a counterfactual belief-based program (Halpern and Moses in Distrib Comput 17(2):91–106, 2004) that also solves the global function computation whenever possible, but where agents send messages only when they believe it is necessary to do so. The latter program is shown to be implemented by a number of well-known algorithms for solving leader election.  相似文献   
6.
We examine four approaches for dealing with the logical omniscience problem and their potential applicability: the syntactic approach, awareness, algorithmic knowledge, and impossible possible worlds. Although in some settings these approaches are equi-expressive and can capture all epistemic states, in other settings of interest (especially with probability in the picture), we show that they are not equi-expressive. We then consider the pragmatics of dealing with logical omniscience—how to choose an approach and construct an appropriate model.  相似文献   
7.
We incorporate an arbitrary number of "candidate" positive distinct poles into the scalar l/sub 1/ optimization framework in order to obtain low-order rational suboptimal solutions to constrained l/sub 1/ optimization problems. Our approach uses a single linear program to minimize an upper bound on the l/sub 1/ norm and gives a solution which uses only the best out of the prespecified poles. Rational suboptimal solutions to a scalar two-block problem are obtained similarly.  相似文献   
8.
Keyboard design through physiological strain measurements   总被引:1,自引:0,他引:1  
The physiologically tolerable range of positions for the joints of the upper extremities have been investigated for typing tasks by recording the myoelectric activities of the involved muscles. For long-term typing tasks a split keyboard is recommended allocating a key field to each hand. The fields should be rotated against each other in the horizontal plane and inclined laterally.  相似文献   
9.
Gossip-based ad hoc routing   总被引:3,自引:0,他引:3  
Many ad hoc routing protocols are based on some variant of flooding. Despite various optimizations of flooding, many routing messages are propagated unnecessarily. We propose a gossiping-based approach, where each node forwards a message with some probability, to reduce the overhead of the routing protocols. Gossiping exhibits bimodal behavior in sufficiently large networks: in some executions, the gossip dies out quickly and hardly any node gets the message; in the remaining executions, a substantial fraction of the nodes gets the message. The fraction of executions in which most nodes get the message depends on the gossiping probability and the topology of the network. In the networks we have considered, using gossiping probability between 0.6 and 0.8 suffices to ensure that almost every node gets the message in almost every execution. For large networks, this simple gossiping protocol uses up to 35% fewer messages than flooding, with improved performance. Gossiping can also be combined with various optimizations of flooding to yield further benefits. Simulations show that adding gossiping to AODV results in significant performance improvement, even in networks as small as 150 nodes. Our results suggest that the improvement should be even more significant in larger networks.  相似文献   
10.
Demographic data show that major changes have been occurring in the everyday lives of families over the last generation, with the majority of mothers of young children in the workforce and an increasing number of men and women assuming caregiving responsibilities for older relatives. Thus, the 2 primary identities of most adults, defined by their multiple family and work roles, need to be coordinated in ways that promote positive family outcomes, returns on investments for employers, and societal values. Despite changes in the workforce, the world of work is still largely organized for a family model that is increasingly rare--one with a stay-at-home caregiver. Recommendations based on psychological and other social science research are offered to align the needs of working families and employers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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-23

京公网安备 11010802026262号