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   481篇
  免费   15篇
  国内免费   1篇
电工技术   2篇
化学工业   93篇
金属工艺   6篇
机械仪表   2篇
建筑科学   24篇
矿业工程   1篇
能源动力   19篇
轻工业   101篇
水利工程   2篇
石油天然气   6篇
无线电   21篇
一般工业技术   47篇
冶金工业   75篇
自动化技术   98篇
  2024年   2篇
  2023年   6篇
  2022年   11篇
  2021年   20篇
  2020年   4篇
  2019年   10篇
  2018年   13篇
  2017年   10篇
  2016年   10篇
  2015年   5篇
  2014年   16篇
  2013年   23篇
  2012年   26篇
  2011年   39篇
  2010年   17篇
  2009年   26篇
  2008年   17篇
  2007年   22篇
  2006年   21篇
  2005年   23篇
  2004年   24篇
  2003年   15篇
  2002年   14篇
  2001年   2篇
  2000年   10篇
  1999年   3篇
  1998年   3篇
  1997年   6篇
  1996年   9篇
  1995年   8篇
  1994年   9篇
  1993年   8篇
  1992年   6篇
  1991年   3篇
  1990年   2篇
  1988年   4篇
  1986年   2篇
  1985年   3篇
  1984年   5篇
  1983年   3篇
  1982年   6篇
  1981年   2篇
  1980年   3篇
  1979年   6篇
  1978年   6篇
  1977年   2篇
  1976年   3篇
  1972年   3篇
  1969年   1篇
  1955年   1篇
排序方式: 共有497条查询结果,搜索用时 0 毫秒
31.
An existing standard catering cart was compared with two prototypes for pushbar and castor design. The first objective of this study was to find out which cart was accompanied with the lowest manually exerted external forces in pushing in a straight way and in pushing a 90 turn. The second objective was to explore effects of the pushbar and castor design of the carts. In the initial and ending phase, the prototypes were accompanied with higher exerted forces compared with the standard catering cart. In pushing straight. the reversed start position of the bigger castors of the prototypes hampered a fluent acceleration and caused higher initial forces. In decelerating, the lower rolling friction of the bigger castors required higher forces to stop the prototypes compared to the standard cart. During the sustained phase, the prototype carts were more favourable. Effects of pushbar and castor design were studied during a turn. The vertical pushbars of the prototypes resulted in lower time-integrated pushing forces. Providing an axis of rotation for turning activities by means of a fixed wheel was proven to be advantageous.  相似文献   
32.
This paper discusses the development of an enterprise domain model in an environment where part of the domain knowledge is vague and not yet formalised in company-wide business rules. The domain model was developed for a young company starting in the telecommunications sector. The company relied on a number of stand-alone business support systems and sought for a manner to integrate them. There was opted for the development of an enterprise-wide domain model that had to serve as an integration layer to coordinate the stand-alone applications. A specific feature of the company was that it could build up its information infrastructure form scratch, so that many aspects of its business were still in the process of being defined. The paper will highlight parts of the Enterprise Model where there was a need for co-designing business rules together with the domain model. A result of this whole effort was that the company got more insight into important domain knowledge and developed a common understanding across functional areas of the way of doing business.  相似文献   
33.
34.
At present, flexible displays are an important focus of research. Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel. One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate. Here, we demonstrate flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-microm-thick polyimide substrates. The displays can be bent to a radius of 1 cm without significant loss in performance. Using the same process flow we prepared row shift registers. With 1,888 transistors, these are the largest organic integrated circuits reported to date. More importantly, the operating frequency of 5 kHz is sufficiently high to allow integration with the display operating at video speed. This work therefore represents a major step towards 'system-on-plastic'.  相似文献   
35.
Used an auditory lexical decision paradigm to determine occurrence of semantic priming between spoken words and to investigate the organization of the mental lexicon in preliterate children. 30 undergraduates and 24 1st-grade children (aged 6 yrs 2 mo to 7 yrs) were tested on a lexical decision task in which Ss had to decide whether pairs of spoken items were words. In both groups, significant facilitation was found for semantically related words compared with unrelated ones. Results indicate that semantic priming occurred in the auditory modality. The fact that children benefited at least as much from and often more than adults from an appropriate semantic context suggests that the lexicon of the child is organized in the same way as the adult's as early as 6 to 7 yrs of age. (French abstract) (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
36.
The main focus of this article is the motion planning problem for a deeply submerged rigid body. The equations of motion are formulated and presented by use of the framework of differential geometry and these equations incorporate external dissipative and restoring forces. We consider a kinematic reduction of the affine connection control system for the rigid body submerged in an ideal fluid, and present an extension of this reduction to the forced affine connection control system for the rigid body submerged in a viscous fluid. The motion planning strategy is based on kinematic motions; the integral curves of rank one kinematic reductions. This method is of particular interest to autonomous underwater vehicles which cannot directly control all six degrees of freedom (such as torpedo-shaped autonomous underwater vehicles) or in case of actuator failure (i.e. under-actuated scenario). A practical example is included to illustrate our technique.  相似文献   
37.
BACKGROUND: Isoflavone content in soybean seeds is strongly influenced by both environment and genotype. However, little is known about the effect of environment and genotype on isoflavones in germ versus cotyledons. To determine the effect of temperature and soil moisture status during soybean seed development on seed isoflavone concentration and composition, a set of two French and three US cultivars of similar maturity were grown in the greenhouse. At the R6 growth stage, plants were subjected to one of three night/day temperature regimes (13/23°, 18/28° or 23/33 °C) in either optimal or sub‐optimal soil water conditions. RESULTS: In cotyledons, a three‐ to six‐fold variation in total isoflavone content was observed between the high and low temperature treatments, whereas the germ contents had less than a two‐fold variation. Soil water supply had less effect than temperature on the isoflavone contents and compositions. In both seed parts, the isoflavone concentrations were highly dependent on the cultivar. CONCLUSION: These results show that isoflavone content and composition in cotyledon and germ are unrelated and it should be possible to independently manipulate these seed traits through plant breeding and crop management systems. Copyright © 2007 Society of Chemical Industry  相似文献   
38.
39.
The conformation of side-chain liquid crystal polymers with different mesogen-graft amounts has been studied by small-angle neutron scattering in dilute solutions of toluene-d8 and THF-d8. It is shown that the radius of gyration increases by about twofold when the mesogen-graft amount increases from 0 to 100%, which suggests that the persistence length of the backbone increases by about 4-fold. Comparison with the results reported in the literature on the melt state suggests that the persistence length is not an intrinsic property of side chain liquid crystal polymers, but depends on inter-chain interactions.  相似文献   
40.
Iron is a critical metal for several vital biological processes. Most of the body’s iron is bound to hemoglobin in erythrocytes. Iron from senescent red blood cells is recycled by macrophages in the spleen, liver and bone marrow. Dietary iron is taken up by the divalent metal transporter 1 (DMT1) in enterocytes and transported to portal blood via ferroportin (FPN), where it is bound to transferrin and taken up by hepatocytes, macrophages and bone marrow cells via transferrin receptor 1 (TfR1). While most of the physiologically active iron is bound hemoglobin, the major storage of most iron occurs in the liver in a ferritin-bound fashion. In response to an increased iron load, hepatocytes secrete the peptide hormone hepcidin, which binds to and induces internalization and degradation of the iron transporter FPN, thus controlling the amount of iron released from the cells into the blood. This review summarizes the key mechanisms and players involved in cellular and systemic iron regulation.  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