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   49646篇
  免费   2488篇
  国内免费   156篇
电工技术   708篇
综合类   65篇
化学工业   10593篇
金属工艺   2136篇
机械仪表   3241篇
建筑科学   1101篇
矿业工程   25篇
能源动力   2111篇
轻工业   3887篇
水利工程   271篇
石油天然气   88篇
武器工业   2篇
无线电   7835篇
一般工业技术   10663篇
冶金工业   3881篇
原子能技术   658篇
自动化技术   5025篇
  2024年   50篇
  2023年   570篇
  2022年   870篇
  2021年   1484篇
  2020年   1069篇
  2019年   1176篇
  2018年   1429篇
  2017年   1413篇
  2016年   1750篇
  2015年   1294篇
  2014年   2088篇
  2013年   3006篇
  2012年   3265篇
  2011年   3890篇
  2010年   2814篇
  2009年   2921篇
  2008年   2811篇
  2007年   2185篇
  2006年   2031篇
  2005年   1723篇
  2004年   1571篇
  2003年   1513篇
  2002年   1329篇
  2001年   1134篇
  2000年   996篇
  1999年   928篇
  1998年   1557篇
  1997年   991篇
  1996年   803篇
  1995年   557篇
  1994年   461篇
  1993年   406篇
  1992年   290篇
  1991年   274篇
  1990年   258篇
  1989年   241篇
  1988年   205篇
  1987年   168篇
  1986年   119篇
  1985年   115篇
  1984年   92篇
  1983年   63篇
  1982年   38篇
  1981年   39篇
  1980年   30篇
  1979年   31篇
  1978年   30篇
  1977年   38篇
  1976年   61篇
  1973年   20篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
161.
162.
Image flow segmentation and estimation using displaced spatial gradient   总被引:2,自引:0,他引:2  
Kim  Y.-H. Kim  S.D. 《Electronics letters》1992,28(24):2213-2215
There are two main causes of inaccuracies in estimating image flows using gradient based techniques. One is the erroneous measurement of gradients in brightness and the other is the blurring of motion boundaries which is caused by the smoothness constraint. In the Letter, the gradient measurement error of conventional methods is analysed and a new technique based on this analysis proposed.<>  相似文献   
163.
164.
165.
166.
Diffusion coefficients for proteins in water are predicted. The numerical method developed is general enough to be applied to a wide range of protein surface shapes, from rodlike to globular. Results are presented for lysozyme and tobacco mosaic virus, and they are compared with actual data and with predictions made by less general methods.  相似文献   
167.
We used the fluorescent labelled dopamine D1-receptor antagonist Bodipy-SCH 23390 for the cellular localization of D1-ligand binding sites in the retinae of different vertebrates (teleosts, Xenopus, turtle, rat and rabbit). Competition experiments with unfixed cryosections of fish retina were performed to characterize the binding conditions of Bodipy-labelled SCH 23390. Tissue bound [3H]SCH 23390 was displaceable with increased amounts of bodipy-SCH 23390. The pharmacological specificity of the D1 fluorescent antagonist was determined by competition experiments with an excess of unlabelled SCH 23390. This treatment significantly reduced the level of fluorescence of the retina confirming the specificity of the binding. We observed a homogeneously distributed fluorescence signal in both plexiform layers in unfixed cryosections of fish, frog, turtle, rat and rabbit. Similar staining intensities of both plexiform layers were found in frog, turtle, rat and rabbit retina. In teleosts, the label of the outer plexiform layer was markedly more intense. Non-specific label was associated with photoreceptor outer and inner segments. The specific labelling of both plexiform layers indicates a mismatch of dopamine releasing and D1-binding sites, and suggests a possible extrasynaptic localization of the D1-receptor. The physiological significance of the observed distribution of D1-ligand binding sites is discussed with respect to the role of dopamine in controlling adaptational processes in the retina.  相似文献   
168.
Abstract— Among various barrier‐rib manufacturing processes, the mold‐pattern‐transfer method has potential to reduce processing cost as well as the manufacture of high‐resolution pixels. In this study, the effects of major processing variables of the mold‐pattern‐transfer process on the formation of air‐trapped pores within barrier ribs were examined. The results indicated that with an optimum combination of the processing variables, barrier ribs without trapped defects can be produced, demonstrating the possibility of reducing the number of processing steps and costs of barrier ribs.  相似文献   
169.
A new physics analysis procedure has been developed for a prismatic very high temperature gas-cooled reactor based on a conventional two-step procedure for the PWR physics analysis. The HELIOS and MASTER codes were employed to generate the coarse group cross sections through a transport lattice calculation, and to perform the 3-dimensional core physics analysis by a nodal diffusion calculation, respectively. Physics analysis of the prismatic VHTRs involves particular modeling issues such as a double heterogeneity of the coated fuel particles, a neutron streaming in the coolant channels, a strong core-reflector interaction, and large spectrum shifts due to changes of the surrounding environment and state parameters. Double heterogeneity effect was considered by using a recently developed reactivity-equivalent physical transformation method. Neutron streaming effect was quantified through 3-dimensional Monte Carlo transport calculations by using the MCNP code. Strong core-reflector interaction could be handled by applying an equivalence theory to the generation of the reflector cross sections. The effects of a spectrum shift could be covered by optimizing the coarse energy group structure. A two-step analysis procedure was established for the prismatic VHTR physics analysis by combining all the methodologies described above. The applicability of our code system was tested against core benchmark problems. The results of these benchmark tests show that our code system is very accurate and practical for a prismatic VHTR physics analysis.  相似文献   
170.
This study employs a relational dialectics approach to gain insights into the nature of relational communication via Cyworld , a Korean social network site. Qualitative analysis of in-depth interview data from 49 users suggests that Cyworld users routinely negotiate multiple dialectical tensions that are created within the online world, transferred from face-to-face contexts, or imposed by interpersonal principles that relate to Korea's collectivistic culture. The interviewees experienced a new relational dialectic of interpersonal relations versus self-relation, analogous to Baxter and Montgomery's (1996) connection-autonomy contradiction. Their responses suggest that Cyworld's design features and functions encourage users to transcend the high-context communication of Korean culture by offering an alternative channel for elaborate and emotional communication, which fosters the reframing of relational issues offline. Cy-Ilchons (online buddies) virtually extend the Korean cultural concept of blood ties, called yons, in ways that intensify the openness-closedness contradiction at early stages of relationship formation.  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