全文获取类型
收费全文 | 533篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 27篇 |
综合类 | 1篇 |
化学工业 | 165篇 |
金属工艺 | 18篇 |
机械仪表 | 7篇 |
建筑科学 | 7篇 |
能源动力 | 22篇 |
轻工业 | 24篇 |
无线电 | 33篇 |
一般工业技术 | 80篇 |
冶金工业 | 99篇 |
原子能技术 | 10篇 |
自动化技术 | 54篇 |
出版年
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 15篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 15篇 |
2014年 | 19篇 |
2013年 | 36篇 |
2012年 | 17篇 |
2011年 | 27篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 16篇 |
2005年 | 17篇 |
2004年 | 10篇 |
2003年 | 20篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 17篇 |
1998年 | 35篇 |
1997年 | 30篇 |
1996年 | 18篇 |
1995年 | 12篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有547条查询结果,搜索用时 0 毫秒
41.
In vitro transdifferentiation of retinal pigmented epithelial cells of the chick embryo into lens cells can be markedly enhanced by culture in the presence of testicular hyaluronidase and phenylthiourea. Since the commercial preparations of hyaluronidase that had previously been used were very crude, a search for the actual effective molecule(s) enhancing lens transdifferentiation was conducted. First, we purified the enzyme and tested the effect of the purified hyaluronidase. Highly purified hyaluronidase itself did not enhance lens transdifferentiation. The crude hyaluronidase was then separated according to affinity with heparin, considering the possibility that the fibroblast growth factor (FGF) is contained in the crude hyaluronidase. Transdifferentiation-enhancing activity was detected in the fraction which was bound to heparin and eluted with 2 M NaCl, where no hyaluronate-degrading activity existed. Analysis of the fraction by SDS-PAGE revealed the existence of an 18 kDa protein whose NH2-terminal sequence was identical to that of basic FGF. The basic FGF derived from bovine brain also enhanced lens transdifferentiation of pigmented epithelial cells. These findings suggest that basic FGF must play a major role in enhancing transdifferentiation of pigmented epithelial cells to lens cells. 相似文献
42.
Y Ueki K Eguchi H Shimada M Nakashima H Ida S Miyake S Nagataki Y Tominaga 《Canadian Metallurgical Quarterly》1994,21(6):1003-1010
OBJECTIVE: To elucidate the role of adhesion molecules in the pathogenesis of rheumatoid arthritis (RA). METHODS: We evaluated their expression and that of an activation marker on CD4+ cell populations and CD4+ cell subsets in specimens of peripheral blood (PB) and synovial fluid (SF) obtained from 10 patients with RA and 7 with osteoarthritis (OA). A 2 or 3-color immunofluorescent method was used for analysis. RESULTS: The SF from both groups of patients showed a greater density of adhesion molecules including LFA-1 alpha, LFA-1 beta, CD2, VLA-4 alpha and VLA-5 alpha on CD4+ cells, and a higher percentage of CD4+HLA-DR+ cells compared with their PB. IN PB-CD4+ cell subsets from the arthritic and healthy subjects, the CD4+CD45RO+ cell population showed an increased expression of adhesion molecules compared with CD4+CD45RA+ cell population. The expression of adhesion molecules on circulating CD4+ cell population and CD4+ cell subsets from the patients with RA and OA was comparable to that from healthy subjects. SF from both groups of patients showed a higher percentage of CD4+CD45RO+ cells and a lower percentage of CD4+CD45RA+ cells. In SF-CD4+ cell subsets from patients with RA, the CD4+CD45RO+ cell population had an increased expression of VLA-4 alpha compared to the CD4+CD45RA+ cell population; however, there was no significant difference in other adhesion molecule expression and the percentage of HLA-DR+ cells between the 2 cell subsets. Furthermore, the expression of VLA-4 alpha on the CD4+CD45RO+ cell population in SF from patients with RA was significantly higher than that in matched PB. In CD4+CD45RA+ cell population from both groups of patients, SF showed an enhanced expression of adhesion molecules and an increased percentage of HLA-DR+ cells compared with matched PB. CONCLUSION: Our results suggest that increased expression of adhesion molecules and increased percentage of HLA-DR+ cells on CD4+ cells in SF may be responsible for cellular interactions between these cells and synovial cells or extracellular matrix. 相似文献
43.
Pinnipeds (Otariidae, Odobenidae, and Phocidae) in the order Carnivora have one or two types (Hb I and Hb II) of hemoglobin components. These hemoglobins consist of identical beta chains and different alpha chains. We determined the complete amino acid sequences of the hemoglobin beta chain of three species of Otariidae (Australian sea lion, South American sea lion, and northern sea lion) and two species of Phocidae (ringed seal and harp seal) from intact beta chain and chemical cleavage fragments. The sequences are similar to beta chains of the already known sequences of pinnipeds. These sequences were compared with those of other carnivores (Mustelidae, Ursidae, Canidae, and Felidae) and adult human hemoglobin beta chain. Using Artiodactyla (pig) as an outgroup, we find that the tree constructed by means of phylogenetic analysis shows that Odobenidae is closest to Otariidae, and that Otariidae and Odobenidae are closer to Mustelidae than to Phocidae. 相似文献
44.
45.
M Tanaka M Sada T Eguchi H Konomi G Naritomi T Takeda Y Ogawa K Chijiiwa GP Deenitchin 《Canadian Metallurgical Quarterly》1996,20(3):267-70; discussion 271
To evaluate the role of endoscopic retrograde cholangiography (ERC) before laparoscopic cholecystectomy, we compared the frequency of concomitant common bile duct stones, their clinical outcome, and the frequency of bile duct injury between a group of 128 patients with routine preoperative ERC (group A) and 1010 patients with selective ERC (group B). Overall, 48 patients (4.2%) had duct stones, but the predictive signs were absent in six of them (12.5%). The stones were demonstrated by ERC and removed by sphincterotomy in all 11 patients in group A. Of 37 patients in group B, 22 were diagnosed by selective ERC and underwent endoscopic removal. Of four patients whose stones were found by operative cholangiography, one had immediate open surgery, another passed a stone spontaneously, and the other two underwent postoperative sphincterotomy, which failed in one. The stones were not recognized until pain recurred in the remaining 11 patients. Sphincterotomy was successful in nine patients but failed in the other two. Thus postoperative sphincterotomy failed in 3 of 13 patients (23%), necessitating open surgery. Forty-two patients overall (3.7%) had aberrant biliary tract anatomy, which did not lead to bile duct injury in any of the patients. Morbidity of routine ERC (3.1%) was lower than that of selective ERC (7.4%) (p < 0.05). It should be noted that a certain proportion of duct stones may be missed by selective ERC, necessitating laparotomy when sphincterotomy fails. The routine use of preoperative ERC may be justified at institutions where the expertise is available, at least until laparoscopic lithotomy becomes easy. 相似文献
46.
47.
H. Rotzinger J. Adams S. R. Bandler J. Beyer H. Eguchi E. Figueroa-Feliciano W. Hsieh G. M. Seidel T. Stevenson 《Journal of Low Temperature Physics》2008,151(1-2):351-356
We have been developing array technology for fabricating magnetic calorimeters for X-ray astronomy. The magnetization change in each pixel of the paramagnetic sensor material due to the heat input of an absorbed X-ray is sensed by a meander shaped coil. With this geometry it is possible to obtain excellent energy sensitivity, low magnetic cross-talk and large format arrays fabricated on wafers that are separate from the SQUID read-out. A magnetic bias field for each pixel is generated by the use of a persistent current that is stored. We report on the results from our prototype arrays, which are coupled to low noise DC-SQUIDs. The first test results are presented and the sensitivity is compared with calculations. 相似文献
48.
Photocatalytic activities of CdS crystallites embedded in TiO2 gel as a stable semiconducting matrix 总被引:2,自引:0,他引:2
Abstracts are not published in this journal
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
49.
Shoji Eguchi 《Fullerenes, Nanotubes and Carbon Nanostructures》1997,5(5):977-987
Recent progress of synthesis of C60 derivatives functionalized with hetero-cycles is reviewed, focusing attention on [4+2]- and [3+2] cycloaddition methodologies and oxidative heterocyclization. 相似文献
50.
Synthesis of TiO2/CdS nanocomposite via TiO2 coating on CdS nanoparticles by compartmentalized hydrolysis of Ti alkoxide 总被引:1,自引:0,他引:1
Hydrolysis of Ti alkoxide in the presence of inverse micelles containing CdS nanoparticles in their hydrophilic interior results in formation of TiO2/CdS nanocomposites in which the CdS nanoparticles are embedded in a TiO2 matrix with a thickness of 10 nm at the surface of the particles. The primary hydroxyl groups introduced by 2-mercaptoethanol as a capping agent used for preparation of the CdS nanoparticles are considered to play an important role for successful adhesion and growth of the TiO2 layer on the CdS surfaces. TEM observation strongly supports formation of semiconductor-in-semiconductor heteronanostructure by compartmentalized hydrolysis of Ti alkoxide within the inverse micelles in which the surface-capped CdS nanoparticles coexist. 相似文献