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   1589篇
  免费   39篇
电工技术   7篇
综合类   1篇
化学工业   137篇
金属工艺   10篇
机械仪表   13篇
建筑科学   16篇
矿业工程   1篇
能源动力   24篇
轻工业   106篇
水利工程   3篇
石油天然气   2篇
无线电   46篇
一般工业技术   84篇
冶金工业   1071篇
原子能技术   6篇
自动化技术   101篇
  2024年   3篇
  2023年   7篇
  2022年   18篇
  2021年   27篇
  2020年   14篇
  2019年   14篇
  2018年   21篇
  2017年   17篇
  2016年   21篇
  2015年   14篇
  2014年   27篇
  2013年   39篇
  2012年   30篇
  2011年   32篇
  2010年   27篇
  2009年   29篇
  2008年   26篇
  2007年   13篇
  2006年   21篇
  2005年   21篇
  2004年   13篇
  2003年   10篇
  2002年   13篇
  2001年   14篇
  2000年   5篇
  1999年   37篇
  1998年   310篇
  1997年   191篇
  1996年   117篇
  1995年   72篇
  1994年   82篇
  1993年   64篇
  1992年   5篇
  1991年   11篇
  1990年   20篇
  1989年   17篇
  1988年   14篇
  1987年   9篇
  1986年   6篇
  1985年   12篇
  1984年   6篇
  1983年   6篇
  1982年   10篇
  1981年   7篇
  1980年   11篇
  1978年   6篇
  1977年   37篇
  1976年   85篇
  1975年   5篇
  1969年   4篇
排序方式: 共有1628条查询结果,搜索用时 15 毫秒
1.
Theoretical Foundations of Chemical Engineering - The corona onset voltage is an important operating parameter in the electrostatic precipitation of nanoparticulate, however, its experimental...  相似文献   
2.
3.
We determined apolipoprotein E (ApoE) genotypes in 122 autopsied demented patients. The frequency of the ApoE epsilon 4 allele was 39.6% in Alzheimer's disease (AD), 29.0% in the Lewy body variant of AD (LBV), and 6.25% in diffuse Lewy body disease. For AD and LBV patients, the epsilon 4 frequency was significantly higher than that reported in nondemented controls (10 to 15%). Therefore, LBV and AD share ApoE epsilon 4 as a genetic risk factor, providing further evidence that these conditions overlap.  相似文献   
4.
5.
6.
Critical systems are aptly named - from electric power to water and gas to the telephone system and the Internet, they're all critical to some aspect of our daily lives. We're a networked society and as such, it's important to both know whether critical systems are trustworthy and be able to communicate, review, and debate the level of trust achieved in them. In the safety domain, explicit safety cases are increasingly required by law, regulations, and standards. In this article, we outline what a small, international group of experts, spanning various disciplines in safety, security, reliability, and critical infrastructure, been doing with the International Working Group on Assurance Cases (for Security), what we hope to achieve, and where we go next.  相似文献   
7.
This paper introduces a methodology for symbolic pole/zero extraction based on the formulation of the time-constant matrix of the circuits. This methodology incorporates approximation techniques specifically devoted to achieve an optimum trade-off between accuracy and complexity of the symbolic root expressions. The capability to efficiently handle even large circuits will be demonstrated through several practical circuits.  相似文献   
8.
9.
OBJECTIVE: To discuss the case of an 8-yr-old boy with an aneurysmal bone cyst of the right proximal humerus, including the features imaged on plain film radiography, computed tomography (CT), magnetic resonance imaging (MRI), including spin echo and fast field echo imaging. CLINICAL FEATURES: The patient suffered for 1 yr from intermittent but progressive pain in his right upper arm and shoulder area. There was no history of trauma or known systemic disease. There was decreased range of motion in abduction of the glenohumeral joint and pain on focal pressure along the deltoid muscle. A complete imaging evaluation consisting of plain film radiography, CT and MRI was performed, which revealed the classical imaging features of an aneurysmal bone cyst. An additional cystic lesion was detected by the MRI that was not appreciated on the plain films or CT. INTERVENTION AND OUTCOME: The patient was referred for biopsy to confirm the preliminary diagnosis of aneurysmal bone cyst. No treatment was instituted. CONCLUSION: Evaluation of aneurysmal bone cyst may be completed with CT scanning and more specifically with MRI MRI coronal T2, weighted images are advantageous for visualization of the main cystic lesion and any additional cysts. Fast field echo images show a better contrast between the cyst and bone marrow with extension of the cyst into the epiphysis as evident in this case. Follow-up studies revealed complete healing of the cyst with only residual densities in the humeral metaphyseal area.  相似文献   
10.
Previous results, using a passive transfer assay, have shown that recrudescences of Plasmodium chabaudi chabaudi AS strain are antigenically different from the infecting parental population and also that the recrudescence appears to be a mix of antigenic types. This present study examines further these recrudescent populations using an indirect fluorescent antibody test on live, schizont-infected red blood cells. This analysis shows that ten clones derived from a recrudescence are all antigenically different from the parent population and that some are different from each other. The use of this method to examine the antigenic types of recrudescent clones after transmission through mosquitoes also demonstrates a resulting change in antigenicity. Such results showing a link between mosquito transmission and varying antigenicity may have important implications in terms of immunity and vaccine development.  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