全文获取类型
收费全文 | 860篇 |
免费 | 12篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 38篇 |
化学工业 | 105篇 |
金属工艺 | 20篇 |
机械仪表 | 14篇 |
建筑科学 | 8篇 |
能源动力 | 7篇 |
轻工业 | 57篇 |
水利工程 | 1篇 |
无线电 | 95篇 |
一般工业技术 | 94篇 |
冶金工业 | 400篇 |
原子能技术 | 4篇 |
自动化技术 | 32篇 |
出版年
2022年 | 4篇 |
2021年 | 12篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 15篇 |
2012年 | 19篇 |
2011年 | 17篇 |
2010年 | 29篇 |
2009年 | 16篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 16篇 |
2005年 | 26篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 19篇 |
1998年 | 136篇 |
1997年 | 91篇 |
1996年 | 63篇 |
1995年 | 39篇 |
1994年 | 31篇 |
1993年 | 37篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有875条查询结果,搜索用时 388 毫秒
1.
Yamada T. Kawakami Y. Nakano T. Mutoh N. Orihara K. Teranishi N. 《Electron Devices, IEEE Transactions on》1997,44(10):1580-1587
This study reports an optimum design for a two-phase charge-coupled device (CCD) and limitations on its driving voltage reduction. The two-phase CCD to be used as a horizontal-CCD (H-CCD) in a CCD image sensor requires low-voltage and high-speed operation. Reducing the driving voltage, however, may induce potential pockets in the channel under the inter-electrode gaps which results in a fatal decrease in charge-transfer efficiency. In this case it is necessary to optimize the CCD design to be free of pocket generation. For this requirement, we conducted two-dimensional (2-D) device simulations for the two-phase CCD, whose potential barriers are formed by boron ion-implantation. Our simulations indicated that the edge position of the potential barrier region and the dose of boron-ion implantation would be important parameters for controlling the size of potential pockets. At an optimum edge position and a boron dose, the minimum driving voltage appears to be reducible to 1.1 V. Characteristics of potential pockets and methods of their suppression are also discussed 相似文献
2.
Morganella morganii postoperative endophthalmitis 总被引:1,自引:0,他引:1
3.
4.
5.
Wakabayashi R. Kawakami H. Sato G. Amano T. Suzuki Y. 《Vehicular Technology, IEEE Transactions on》1998,47(2):392-405
A VHF omnidirectional radio range (VOR) is a navigation aid radio beacon facility, which provides aircraft with azimuth information relative to the VOR station in question as the origin. In Japan, two types of VOR-the conventional type (referred to as a CVOR) and the Doppler type (referred to as a DVOR)-are currently in use. An element known as the Alford loop antenna (ALA), which changes the loading reactance, is used for the VOR because the horizontally polarized wave and nondirectivity in the horizontal plane are preferred. A VOR antenna consists of a carrier antenna and a sideband antenna-an aircraft receives separate signals from these two antennas and compares them to obtain azimuth information. The mutual coupling between the elements forming the carrier and the sideband antenna affects the directivity of the single elements, resulting in errors in azimuth information. With the mutual coupling between the antenna elements being taken into consideration, a quantitative calculation was made by using the moment method-the results of the calculation made it clear that a loading reactance value of -320 Ω is better to make not mutually coupled elements nondirectional while a loading reactance value of -600 Ω is optimum to minimize the azimuth error of a CVOR 相似文献
6.
An outbreak of Cryptosporidiosis occurred over three months in a British Columbia community, peaking in December 1990. Results of the case-control study and illness surveys support the hypothesis that transmission occurred in a public children's pool at the local recreation centre. Analysis using lab-confirmed cases revealed a matched odds ratio of 4.5 [95% CI 0.97, 20.83], and using clinical cases an unmatched odds ratio of 12.8 [95% CI 3.68, 46.77], associated with swimming in the children's pool within two weeks prior to onset of illness. Other risk factors were not significant. Attack rates in various groups of children's pool users ranged from 8% to 78%. The children's pool was closed for steam cleaning and disinfection. Unusually frequent defecations including liquid stools had occurred before and during the outbreak. Improvements were instituted for removal of feces and superchlorination of pool water. 相似文献
7.
8.
PURPOSE: Normal retina is firmly attached to the retinal pigment epithelium, but the force of this adhesion drops precipitously within the first 2-3 min after enucleation. The purpose was to study metabolic factors that might be relevant to this postmortem failure of adhesion. METHODS: Dutch rabbit retina was manually peeled from the retinal pigment epithelium on strips of enucleated eyecup within a 37 degrees C bath. Retinal adhesiveness was measured by observing the amount of retinal pigment epithelium that remained adherent to the retina. RESULTS: Autologous whole blood in place of salt solution retarded the decrease in adhesiveness. A solution of hemoglobin alone was similarly effective, whereas methemoglobin solution failed to help the persistence of retinal adhesion. Bubbling oxygen into the salt solution and circulating it to avoid oxygen depletion at the tissue boundary also proved effective at sustaining retinal adhesiveness. Eyes made ischemic in vivo for 5 min or longer, by elevating intraocular pressure, showed virtually no retinal adhesion when enucleated immediately thereafter. However, eyes made ischemic for 10 min, but allowed to regain circulation for 5 min before enucleation, showed a return of retinal adhesiveness to 80% of normal. CONCLUSIONS: Oxidative metabolism is critical to the maintenance of retinal adhesiveness, and the effects of oxygen deprivation on adhesion are reversible within a certain time period. 相似文献
9.
Remarkably rapid nitriding which is independent of diffusion theory based on the thermal activation process, was observed during nitriding of austenitic Fe-Ni-Cr steels containing 16 and 19 mass% chromium. Increase of the chromium content in the alloys yielded increasing thickness of the nitrided layer, i.e. the internal nitriding theory did not hold in the nitriding. No rapid nitriding was observed in steels containing less than 13 mass% chromium. Hence the limiting concentration of chromium for the rapid nitriding will lie between 13 and 16 mass% chromium. A solution to the problem of abnormalities arising during nitriding of practical austenitic stainless steels which have been investigated since 1972, has been presented experimentally by nitriding various chromium-containing steels. Based on the experimental results, the origin of the rapid nitriding is discussed in connection with the free-energy function of Cr2N and CrN to temperature. In particular, a plateau of nitrogen concentration measured in the nitrided layers leads to the conclusion that a forced nitrogen diffusion in the layer resulted in the rapid nitriding. 相似文献
10.
RY Poon K Yamashita JP Adamczewski T Hunt J Shuttleworth 《Canadian Metallurgical Quarterly》1993,12(8):3123-3132
Activation of the cyclin-dependent protein kinases p34cdc2 and p33cdk2 requires binding with a cyclin partner and phosphorylation on the first threonine residue in the sequence THEVVTLWYRAPE. We present evidence that this threonine residue, number 160 in p33cdk2, can be specifically phosphorylated by a cdc2-related protein kinase from Xenopus oocytes called p40MO15. Binding to cyclin A and phosphorylation of this threonine are both required to activate fully the histone H1 kinase activity of p33cdk2. In cell extracts, a portion of p40MO15 is found in a high molecular weight complex that is considerably more active than a lower molecular weight form. Wild-type MO15 protein expressed in bacteria does not possess kinase activity, but acquires p33cdk2-T160 kinase activity after incubation with cell extract and ATP. We conclude that p40MO15 corresponds to CAK (cdc2/cdk2 activating kinase) and speculate that, like p33cdk2 and p34cdc2, p40MO15 requires activation by phosphorylation and association with a companion subunit. 相似文献