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   295056篇
  免费   5983篇
  国内免费   1852篇
电工技术   5654篇
技术理论   5篇
综合类   1192篇
化学工业   48304篇
金属工艺   11613篇
机械仪表   8386篇
建筑科学   7692篇
矿业工程   1723篇
能源动力   6282篇
轻工业   30224篇
水利工程   3187篇
石油天然气   6123篇
武器工业   247篇
无线电   29800篇
一般工业技术   55237篇
冶金工业   55586篇
原子能技术   5767篇
自动化技术   25869篇
  2021年   3246篇
  2020年   2310篇
  2019年   2712篇
  2018年   4712篇
  2017年   4666篇
  2016年   5051篇
  2015年   3741篇
  2014年   5812篇
  2013年   13699篇
  2012年   9720篇
  2011年   12048篇
  2010年   9581篇
  2009年   9975篇
  2008年   11014篇
  2007年   10933篇
  2006年   9425篇
  2005年   8218篇
  2004年   7451篇
  2003年   6905篇
  2002年   6824篇
  2001年   6678篇
  2000年   6271篇
  1999年   6353篇
  1998年   15478篇
  1997年   11113篇
  1996年   8302篇
  1995年   6136篇
  1994年   5606篇
  1993年   5468篇
  1992年   4120篇
  1991年   3931篇
  1990年   4007篇
  1989年   3939篇
  1988年   3686篇
  1987年   3157篇
  1986年   3204篇
  1985年   3578篇
  1984年   3471篇
  1983年   3178篇
  1982年   2827篇
  1981年   3043篇
  1980年   2773篇
  1979年   2951篇
  1978年   2835篇
  1977年   2998篇
  1976年   4043篇
  1975年   2530篇
  1974年   2353篇
  1973年   2385篇
  1972年   2022篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
111.
A Biologically-Parameterized Feather Model   总被引:1,自引:0,他引:1  
Feathers, unlike other cutaneous appendages such as hair, fur, or scales have a definite structure. Variation in feather structure creates a wide range of resulting appearances. Collectively, feather structure determines the appearance of the feather coat, which can largely affect the resulting look of a feathered object (bird). In this paper we define the structure of individual feathers using a parameterization based on biological structure and substructures of actual feathers. We show that our parameterization can generate a large variety of feathers at multiple levels of detail and provide an initial step to semi‐automatically generating a wide range of feather coats. his is achieved by specifying an intuitive interpolation between different structures and ages of feathers.  相似文献   
112.
The authors report an exceedingly rare complication of rheumatoid arthritis, i.e. acquired hemophilia due to anti-factor VIII autoantibody production. Treatment with intravenous immune globulin ensured control of hemorrhagic manifestations by inducing a transient rise in factor VIII level.  相似文献   
113.
114.
The mechanisms that control lipolysis in intra-abdominal fat cells from various primate species, the marmoset (Callithrix jacchus), the baboon (Papio papio), and the macaque (Macaca fascicularis), were compared to those of human intraabdominal fat cells. Selective beta 1- or beta 2-adrenoceptor agonists induced lipolysis in all species. Selective beta 3-agonists (BRL 37344, CL 316243, and SR 58611) acted as partial agonists in marmoset but were inefficient in other primates, including humans. alpha 2-Adrenoceptor number ([3H]RX 8210002 binding) equalized (baboon) or exceeded (other primates) beta 1/beta 2-adrenoceptors ([3H]CGP 12177 binding). Baboon fat cell membranes expressed similar amounts of coupled beta- and alpha 2-adrenoceptors. In all species, norepinephrine- or epinephrine-induced lipolysis did not reach the lipolytic effect of isoproterenol but their effects were enhanced after alpha 2-adrenoceptor blockade. N6-phenylisopropyladenosine (PIA) induced a full antilipolytic effect in baboon, macaque, and human adipocytes through adenosine receptors ([3H]DPCPX binding). Peptide YY (PYY) weakly inhibited lipolysis in baboon. Adrenocorticotropic hormone (ACTH) was inactive whereas parathyroid hormone (PTH) partially stimulated lipolysis in primates. Histamine was partially lipolytic in marmoset only. This study emphasizes the similarities of the mechanisms controlling the lipolysis in nonhuman primate and in human adipocytes and suggests that the baboon and the macaque should provide unique models for the study of the regulation of lipolysis.  相似文献   
115.
A solution to autonomous lateral vehicle guidance using a neurocontroller that can learn from measured human-driving data without knowledge of the physical car parameters is discussed. Simulations and practical tests confirm that a small-size feedforward autonomous neural network (21 neurons) can learn to steer a vehicle at high speeds only from looking at human-driving examples. In this way, the network learns the total closed-loop behavior, including the nonlinear dynamics of the vehicle and the driver's individual driving style. The main result of practical investigations is that the neutral controller trained on human-driving examples exhibits an aperiodic behavior that does not vanish at higher speeds (tests performed up to 130 km/h) and produces fewer lateral deviations than the linear state controller  相似文献   
116.
Following two years operation of the 100 kW grid-connected installation N13 near Domat/Ems, Switzerland, considerable data are available. The yield of the installation was calculated on the basis of long-term meteorological data and of the Meteonorm model. The findings show a close correlation between the forecast and the measured yields. With 100% availability of the inverter in 1991, the performance of the installation rose from 59% in 1990 to 79% in 1991. With standardized analysis of the data, the performance of the grid-connected installation N13 can be compared with other grid-connected installations irrespective of size and location.  相似文献   
117.
Methods are described for forming coating specimens and testing them in pure bending. The proposed tester gives adequate accuracy in determining the elastic characteristics and strength for thin specimens (up to 0.1 mm) of brittle materials of powder-coating type.Translated from Problemy Prochnosti, No. 3, pp. 94–97, March, 1993.  相似文献   
118.
Professional software engineering continues to face problems that involve large-scale (complex) software systems development. Such efforts typically require team collaboration over months, possibly years. Once implemented, the system must be maintained for sometimes decades. This development and maintenance life cycle requires not only technical knowledge and skills in software development, but also the knowledge and skills associated with software process. We believe the traditional computer science curriculum fails to consider this spectrum of needs. We also believe, however, that software engineering must use certain elements of the core knowledge and skills taught by computer scientists as its foundation. We describe lessons learned from the 10-year collaboration between Monmouth University and the Software Engineering Center of the US Army's CECOM (Communications Electronics Command). The center recruits electrical engineering and computer science graduates from academic institutions in the geographic regions surrounding its various installations to be part of its intern program; Monmouth University, in turn, incorporates the demands of the intern program in its Master of Science in software engineering curriculum  相似文献   
119.
The authors report the case of a woman admitted to hospital for minor trauma of the left hip and who presented major ST segment elevation on the second day suggesting an acute anterior wall myocardial infarction at the same time as a cerebrovascular accident. Complementary investigations and follow-up excluded the diagnosis of myocardial infarction with normalisation of the ECG on the 5th day. ECG changes during cerebrovascular accidents may be very variable ranging from extrasystoles to ST elevation mimicking myocardial infarction. They carry a poor prognosis with an increased risk of sudden death necessitating continuous ECG monitoring until the ECG reverts to normal. The cardiac involvement is not ischaemic but due to disease of the insular cortex of the brain which induces myocytolysis (centered around the intra-cardiac nerve endings) due to the sudden liberation of catecholamines. These lesions may be treated by propranolol or phentolamine.  相似文献   
120.
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