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   770篇
  免费   19篇
  国内免费   3篇
电工技术   30篇
综合类   1篇
化学工业   124篇
金属工艺   20篇
机械仪表   24篇
建筑科学   18篇
矿业工程   1篇
能源动力   25篇
轻工业   48篇
水利工程   3篇
无线电   128篇
一般工业技术   115篇
冶金工业   161篇
原子能技术   14篇
自动化技术   80篇
  2023年   3篇
  2022年   9篇
  2021年   7篇
  2020年   4篇
  2019年   4篇
  2018年   9篇
  2017年   5篇
  2016年   10篇
  2015年   14篇
  2014年   17篇
  2013年   31篇
  2012年   21篇
  2011年   40篇
  2010年   17篇
  2009年   28篇
  2008年   34篇
  2007年   30篇
  2006年   25篇
  2005年   20篇
  2004年   15篇
  2003年   23篇
  2002年   14篇
  2001年   17篇
  2000年   11篇
  1999年   16篇
  1998年   77篇
  1997年   59篇
  1996年   34篇
  1995年   31篇
  1994年   18篇
  1993年   22篇
  1992年   15篇
  1991年   17篇
  1990年   9篇
  1989年   4篇
  1988年   13篇
  1987年   2篇
  1986年   7篇
  1985年   7篇
  1984年   8篇
  1983年   9篇
  1982年   6篇
  1981年   7篇
  1980年   2篇
  1979年   8篇
  1978年   3篇
  1977年   4篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
排序方式: 共有792条查询结果,搜索用时 31 毫秒
61.
This paper presents an efficient layout method for a high-speed multiplier. The Wallace-tree method is generally used for high-speed multipliers. In the conventional Wallace tree, however, every partial product is added in a single direction from top to bottom. Therefore, the number of adders increases as the adding stage moves forward. As a result, it generates a dead area when the multiplier is laid out in a rectangle. To solve this problem, we propose a rectangular Wallace-tree construction method. In our method, the partial products are divided into two groups and added in the opposite direction. The partial products in the first group are added downward, and the partial products in the second group are added upward. Using this method, we eliminate the dead area. Also, we optimized the carry propagation between the two groups to realize high speed and a simple layout, We applied it to a 54×54-bit multiplier. The 980 μm×1000 μm area size and the 600 MHz clock speed have been achieved using 0.18 μm CMOS technology  相似文献   
62.
A major potential application for ex vivo culture of hematopoietic progenitor cells is the treatment of cytopenia following high-dose chemotherapy and hematopoietic transplantation. We have previously postulated that infusion of a sufficient number of neutrophil postprogenitor cells generated by ex vivo culture of CD34+ cells may be able to abrogate neutropenia. In this article, we describe further development of an efficient stromal-free, cytokine-dependent, static culture system for generation of these cells. Our previous studies indicated that maximal production of nucleated cells and myeloid progenitor cells from PB CD34+ cells occurred with multiple hematopoietic growth factor (HGF), notably the 6-HGF combination of interleukin (IL)-1, IL-3, IL-6, granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage-CSF (GM-CSF), and stem cell factor (SCF). In the present study, we determine the contribution of each of these 6 HGF in generation of neutrophilic precursors. SCF, G-CSF, and IL-3 were found to be the most important HGF for production of neutrophilic cells. The 4-HGF combination of IL-3, IL-6, G-CSF, and SCF was optimized by performing dose-response experiments and shown to be as potent as 6 HGF for production of nascent CFU-GM and neutrophilic precursors.  相似文献   
63.
We report a case of retinal detachment with Kniest dysplasia for which vitreous surgery was effective. The patient was a 7-year-old female who had the typical ocular and physical findings of this disease. Visual acuity was light perception alone due to a hypermature cataract and bullous retinal detachment. We performed cataract surgery and pars plana vitrectomy, and used silicone oil tamponade. After seven months, the silicone oil was removed, and visual acuity improved to 0.09. We conclude that bullous retinal detachment with Kniest dysplasia can be treated by vitreous surgery in combination with the use of silicone oil tamponade.  相似文献   
64.
The mechanism of polyethylene particle growth was investigated using poly(styrene-co-divinylbenzene) (PS beads) supported rac-Ph2Si(Ind)2ZrCl2 catalyst. From the analysis of the resulting polyethylene particles by SEM (scanning electron microscopy) and EPMA (electron probe microanalysis), it was found that the active species are located on the surface layer of catalyst particles and that the catalytic species are uniformly distributed throughout the polymer particles, whereas the cores of PS beads, which lack a potential active species, were not disintegrated during polymerization. These results suggest that the PS beads supported catalyst also follows the fragmentation and replication process as frequently observed with the MgCl2 supported Ziegler–Natta catalysts.  相似文献   
65.
A major allergenic protein of buckwheat, Fag e 1 prepared from common buckwheat (Fagopyrum esculentum), was covalently linked with food-grade polysaccharides, arabinogalactan or xyloglucan through the controlled dry-heating at 60 °C under 65% relative humidity. The introduction of polysaccharide chain onto the molecular surface of Fag e 1 reduced the allergenicity of Fag e 1. The results revealed that the Maillard-type glycosylation of Fag e 1 with polysaccharides brought about a drastic reduction of the reactivity against human sera of buckwheat-allergy subjects, using immuno dot-blotting, QCM analysis and ELISA. In addition, the glycosylation of Fag e 1 yielded a great improvement of its surface functionality. Solubility of Fag e 1 at the neutral pH was substantially increased up to 13.5 times and 9.6 times by the conjugation with arabinogalactan and xyloglucan, respectively. Emulsifying properties of Fag e 1 were also improved by the glycosylation, of which both emulsifying activity and emulsion stability were more than 6 times higher than those of the native protein.  相似文献   
66.
Now it is recognized that DHA is oxidatively stable fatty acid compared with linoleic acid (LA) in emulsified system, although DHA is oxidatively unstable in a bulk system. In fact, an emulsified mixture of DHA and LA behaves as in a bulk system, namely the oxidative stability of DHA becomes lower than that of LA. Therefore, in this study, tridocosahexaenoate (DDD) and glycerol trilinoleate (LLL) were separately emulsified using TritonX-100 as an emulsifier and DDD emulsion was mixed with the oxidizing LLL emulsion using a water-soluble radical initiator, 2,2'-azobis(2-aminopropane) dihydrochloride. As a result, DHA suppressed the oxidation of LA, while DHA was not significantly oxidized. This suppression ability was examined using glycerol trieicosapentaenoate, glycerol trilinolenate, or glycerol trioleate instead of DDD and it was found that this activity was increased with the increasing number of double bonds in the structure. Furthermore, the same type of experiment was carried out using a lipid-soluble radical initiator, 2,2'-azobisisobutyronitrile and the similar result was obtained. These results indicated that a highly polyunsaturated fatty acid might act as an antioxidant in an emulsion system oxidized by an azo compound.  相似文献   
67.
Our previous study indicated that both 17β-estradiol (E2), known to be an endogenous estrogen, and bisphenol A (BPA), known to be a xenoestrogen, could positively influence the proliferation or differentiation of neural stem/progenitor cells (NS/PCs). The aim of the present study was to identify the signal transduction pathways for estrogenic activities promoting proliferation and differentiation of NS/PCs via well known nuclear estrogen receptors (ERs) or putative membrane-associated ERs. NS/PCs were cultured from the telencephalon of 15-day-old rat embryos. In order to confirm the involvement of nuclear ERs for estrogenic activities, their specific antagonist, ICI-182,780, was used. The presence of putative membrane-associated ER was functionally examined as to whether E2 can activate rapid intracellular signaling mechanism. In order to confirm the involvement of membrane-associated ERs for estrogenic activities, a cell-impermeable E2, bovine serum albumin-conjugated E2 (E2-BSA) was used. We showed that E2 could rapidly activate extracellular signal-regulated kinases 1/2 (ERK 1/2), which was not inhibited by ICI-182,780. ICI-182,780 abrogated the stimulatory effect of these estrogens (E2 and BPA) on the proliferation of NS/PCs, but not their effect on the differentiation of the NS/PCs into oligodendroglia. Furthermore, E2-BSA mimicked the activity of differentiation from NS/PCs into oligodendroglia, but not the activity of proliferation. Our study suggests that (1) the estrogen induced proliferation of NS/PCs is mediated via nuclear ERs; (2) the oligodendroglial generation from NS/PCs is likely to be stimulated via putative membrane-associated ERs.  相似文献   
68.
Recently, a new low‐cost disposable laser disdrometer with the capacity for hydrometeor imaging was proposed by the authors. The laser disdrometer has the drawback of detecting false raindrops, which are splashed droplets and pooled water drops on the housing. Actual raindrops can be sorted from false raindrops by their different fall speeds, but the large size and slow falling speed of false raindrops induce significant observational dead time, affecting the raindrop capture rate and the number density of the raindrops. The ratio between the actual number of raindrops and the total number of drops including the false raindrops provides a reasonable rain intensity correction. This report describes the performance of a laser disdrometer with rain intensity correction in heavy rainfall. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
69.
Toshiharu Tominaka 《低温学》2011,51(11-12):630-634
The calculation method for the current distributions within a coaxial multi-layered power cable consisting of helically wound long superconducting tape conductors have been studied. The analytical expressions for the self- and mutual inductances of the coaxial helical long thin arch-shaped tapes are analytically and numerically compared with straight arch-shaped and flat tapes. It is confirmed that these expressions are consistent with each other. The current distributions within a coaxial 3-layered cable are calculated, using the self- and mutual inductances obtained due to the thin approximation. The effect of the non-uniform gaps between tapes in a coaxial multi-layered power cable is studied.  相似文献   
70.
对日本建筑用密封材料的发展趋势、应用领域、材料标准以及设计施工规范等内容进行了阐述。  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