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   677篇
  免费   47篇
  国内免费   5篇
电工技术   83篇
综合类   8篇
化学工业   188篇
金属工艺   17篇
机械仪表   21篇
建筑科学   18篇
矿业工程   6篇
能源动力   32篇
轻工业   45篇
水利工程   2篇
石油天然气   20篇
武器工业   6篇
无线电   70篇
一般工业技术   128篇
冶金工业   29篇
原子能技术   11篇
自动化技术   45篇
  2024年   5篇
  2023年   4篇
  2022年   15篇
  2021年   20篇
  2020年   9篇
  2019年   15篇
  2018年   13篇
  2017年   10篇
  2016年   18篇
  2015年   25篇
  2014年   30篇
  2013年   60篇
  2012年   31篇
  2011年   48篇
  2010年   38篇
  2009年   43篇
  2008年   35篇
  2007年   20篇
  2006年   33篇
  2005年   12篇
  2004年   17篇
  2003年   22篇
  2002年   24篇
  2001年   11篇
  2000年   12篇
  1999年   7篇
  1998年   16篇
  1997年   14篇
  1996年   13篇
  1995年   5篇
  1994年   19篇
  1993年   7篇
  1992年   4篇
  1991年   4篇
  1990年   9篇
  1989年   2篇
  1988年   5篇
  1987年   4篇
  1986年   5篇
  1985年   4篇
  1984年   6篇
  1983年   8篇
  1982年   6篇
  1981年   3篇
  1980年   2篇
  1979年   3篇
  1978年   3篇
  1977年   3篇
  1969年   2篇
  1967年   1篇
排序方式: 共有729条查询结果,搜索用时 15 毫秒
1.
2.
A right-handed patient with a haematoma in the left pulvinar showed impaired stereoacuity. In contrast with previous reports, he did not show peripheral visual extinction or prolonged reaction times for targets on the side contralateral to the lesion.  相似文献   
3.
4.
氮化硅基陶瓷连接技术的研究进展   总被引:2,自引:0,他引:2  
陶瓷连接技术是结构陶瓷实用化的有效手段,焊料成分对连接体的性能具有决定性作用。本文主要从焊料成分选择的角度,总结了氮化硅基陶瓷连接技术的发展现状;并重点讨论了陶瓷/玻璃复合焊料在β-Sialon陶瓷连接中的应用。  相似文献   
5.
Miyamoto S  Kuwata G  Imai M  Nagao A  Terao J 《Lipids》2000,35(12):1411-1414
Beneficial effects of dietary phytic acid (myo-inositol hexaphosphate; IP6) have often been explained by its strong iron ion-chelating ability, which possibly suppresses iron ion-induced oxidative damage in the gastrointestinal tract. Because phytic acid is hydrolyzed during digestion, this work aimed to know whether its hydrolysis products (IP2′ IP3′, IP4′ and IP5) could still prevent iron ion-induced lipid peroxidation. Studies using liposomal membranes demonstrated that hydrolysis products containing three or more phosphate groups are able to inhibit iron ion-induced lipid peroxidation although their effectiveness decreased with dephosphorylation. Similarly, they also prevented iron ion-induced decomposition of phosphatidylcholine hydroperoxide. These results demonstrate that intermediate products of phytic acid hydrolysis still possess iron ion-chelating ability, and thus they can probably prevent iron ion-induced lipid peroxidation in biological systems.  相似文献   
6.
The crystalline complex between poly(γ-methyl l-glutamate) (PMLG) and dimethyl phthalate (DMP) has been formed in films cast from a solution in dichloroethane. It has the stoichiometry of 1 mol of DMP to three or four residues of PMLG and shows two definite characteristics in X-ray diffraction patterns; one is the large hexagonal unit cell with the edge of around 28 Å and another the ‘extra’ 5.07 Å meridional reflection which can not be interpreted by a PMLG α-helical conformation. The structural examination for the films with various DMP contents is carried out by X-ray, viscoelastic, and d.s.c. measurements and the following structure is proposed for the crystalline complex. Four PMLG are associated to form a group which is hexagonally packed and DMP molecules, located in the gaps between groups, form a specific favourable helical structure along PMLG chains in which the van der Waals stacking of benzene rings of DMP is significant.  相似文献   
7.
Diachasmimorpha juglandis is a specialist parasitoid attacking fly larvae in the genus Rhagoletis that feed exclusively on walnut fruit husks. In a free-foraging assay comparing response to uninfested, infested, and mechanically damaged fruits, we first determined that D. juglandis use host feeding damage on the fruit as a cue for host presence. In another free-foraging assay that used artificial walnut models and wind tunnel experiments, D. juglandis distinguished infested from uninfested fruits by using either olfactory or visual cues separately. However, the response rate of wasps in the wind tunnel was raised considerably when visual cues were also available. We analyzed the volatile compounds emitted by cohorts of uninfested, mechanically damaged, and infested fruits 1, 3, 5, 8, and 10 days after oviposition by flies into the infested fruits. Total volatile emissions did not differ significantly among treatments, but quantitative changes in volatiles distinguished infested fruits from uninfested and damaged fruits. The fact that parasitoids did not distinguish between infested and damaged fruits in assays where damage was visible indicates that they rely on visual cues when those are available.  相似文献   
8.
基于Visual C#语言实现了有限状态自动机.该自动机具有小巧轻便、简单易用的优点,可应用于程序复杂界面的操作与控制.  相似文献   
9.
In this study, we propose a revised radial basis function (RBF) neural network algorithm and apply this algorithm to computer-aided diagnosis (CAD) of the liver. First, the revised RBF neural network algorithm is applied to recognition of the liver regions, and the recognition results are compared with those obtained using the conventional RBF neural network and the conventional multilayered neural network trained using the back-propagation algorithm. It is shown that the revised RBF neural network is accurate, and is a useful method because the parameters are automatically determined. Then, the revised RBF neural network is applied to CAD of the liver cancer called hepatocellular carcinoma (HCC).  相似文献   
10.
The points of this presentation are reform of the theory relating to "Dysplasia and Carcinogenesis" and the cytological methods. In 1976, Meisels and Fortin reported that dysplasia is the disease caused by Human papilloma virus (HPV), and surprisingly, intermediate cells infected by HPV possessed the ability of proliferation and mitosis, resulting in binucleation and multinucleation. In cytology, dysplasia is thought to be delivered from basal cells and abnormal cells are differentiated from lower layer to upper layer, the grade of dysplasia is judged from the level of cell-differentiation. In histology, however, differentiated cells are thought to be normal cells from the histological definition. Therefore, the histological theory cannot explain the fact that the appearance of the abnormal cells from the all layers in cytology of the mild dysplasia. This discrepancy can be understood well if we think it is caused by HPV infection. HPV (ds-DNA) can only proliferate using cellular factors. And as keratinocytes is important with relating to this proliferation, HPV affects human intermediate layer and upper layer. In HPV-infected cells, HPV-E6 protein and E7 protein can bind the products of p53 and pRB, suppressor genes, respectively. These lead to degradation of these proteins' function, acceleration of cell proliferation, and abnormality of cell-cycle time. Our fundamental theory of dyskaryosis is based on these findings. Mild dysplasia is transferred from intermediate layer to upper layer and vanish after cell maturation. Immortalization, transformation, and gene alteration are important factors for carcinogenesis. The deletion of chromosome 3p is one of the most important genetic changes during carcinogenesis. On the basis of carcinogenesis theory described above, the cytological findings of HPV-infected cells are classified into three steps.(ABSTRACT TRUNCATED AT 250 WORDS)  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