全文获取类型
收费全文 | 317篇 |
免费 | 8篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 5篇 |
综合类 | 2篇 |
化学工业 | 24篇 |
金属工艺 | 17篇 |
机械仪表 | 3篇 |
建筑科学 | 2篇 |
矿业工程 | 4篇 |
能源动力 | 1篇 |
轻工业 | 10篇 |
石油天然气 | 8篇 |
武器工业 | 4篇 |
无线电 | 31篇 |
一般工业技术 | 11篇 |
冶金工业 | 174篇 |
原子能技术 | 11篇 |
自动化技术 | 40篇 |
出版年
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 8篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2004年 | 17篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 21篇 |
1998年 | 35篇 |
1997年 | 26篇 |
1996年 | 25篇 |
1995年 | 21篇 |
1994年 | 45篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 7篇 |
1976年 | 14篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1958年 | 1篇 |
1943年 | 1篇 |
1882年 | 3篇 |
排序方式: 共有347条查询结果,搜索用时 31 毫秒
1.
The dead-end filtration characteristics of the dimorphic yeast Kluyveromyces marxianus var. marxianus (formerly fragilis) NRRLy2415 were investigated for a range of mean cell morphologies, ranging from predominantly yeast-like to predominantly filamentous. Semiautomated image analysis was used to measure the mean cell specific surface area, Sv, and the mean ratio of cell length to equivalent cylindrical diameter, Ldm, in each broth. The method of Ju and Ho (Biotechnol. Bioeng. 1988, 32, 95-99) was used to show that for broths with Ldm values between 1.72 and 10.03, the voidage of cell pellets formed by centrifugation increased with increasing Ldm. In the pressure range 30-180 kPa, the specific filter cake resistance, alpha, was found to be related to pressure, DeltaP, through the equation alpha = alpha0(1 + kcDeltaP). The dependence of alpha0/Sv2 on Ldm was found to be qualitatively consistent with the pellet voidage data and the Carman-Kozeny equation. Considerably better agreement with the experimental data was obtained when the Kozeny constant, K, was treated as variable and related to Ldm through the equation K = 4.83 + 7.08 log10 Ldm. The cake compressibility constant, kc, was found to increase with increasing Ldm, a phenomenon consistent with the wide range of voidages that can be displayed by beds of long cylinders. 相似文献
2.
3.
本文介绍低轨小卫星的发展和应用前景。低轨小卫星,体积和重量小,轨道低,功能单一,智能化,制造和发射都很容易,投资费用低,受到用户的普遍欢迎,有广阔的发展和应用前景。 小卫星在近几年发展迅速,应用广泛,已经受到世界各国的重视。在许多方面,已经应用小卫星和计划中应用小卫星的例子很多,本文只作简要介绍,目的在于引起人们的重视,发展我国的小卫星事业。 相似文献
4.
本文针对海湾战争后的新形势,介绍了战略防御的新构想、战术防空导弹系统及21世纪的防空概念,论述了AEW、AWACS、战场监视目标攻击雷达及其它雷达的最新发展情况,此外,还对国外的反隐身技术进展情况作了介绍。 相似文献
5.
V. N. Jmerik A. M. Mizerov T. V. Shubina A. V. Sakharov A. A. Sitnikova P. S. Kop’ev S. V. Ivanov E. V. Lutsenko A. V. Danilchyk N. V. Rzheutskii G. P. Yablonskii 《Semiconductors》2008,42(12):1420-1426
Features of plasma-assisted molecular-beam epitaxy of AlGaN compounds at relatively low temperatures of the substrate (no higher than 740°C) and various stoichiometric conditions for growth of the nitrogen- and metal-enriched layers are studied. Discrete submonolayer epitaxy for formation of quantum wells and n-type blocking layers without varying the fluxes of components was used for the first time in the case of molecular- beam epitaxy with plasma activation of nitrogen for the nanostructures with the Al x Ga1 ? x N/Al y Ga1 ? y N quantum wells. Structural and optical properties of the Al x Ga1 ? x N layers in the entire range of compositions (x = 0–1) and nanostructures based on these layers are studied; these studies indicate that there is photoluminescence at room temperature with minimum wavelength of 230 nm. Based on the analysis of the photoluminescence spectra for bulk layers and nanoheterostructures and their temperature dependences, it is concluded that there are localized states in quantum wells. Using the metal-enriched layers grown on the c-Al2O3 substrates, heterostructures for light-emitting diodes with Al x Ga1 ? x N/Al y Ga1 ? y N quantum wells (x = 0.4–0.5, y = x + 0.15) were obtained and demonstrated electroluminescence in the ultraviolet region of the spectrum at the wavelength of 320 nm. 相似文献
6.
Glomerular tip lesion is a newly described histopathological lesion characterized by a focal and segmental widening of the mesangial matrix without hypercellularity together with capillary dilatation, hyaline exudation on the inside of capillary walls and occurrence of vacuolized cells, localized to the peripheral segments of the glomerular tuft. Clinically, these patients have a pronounced nephrotic syndrome with slightly reduced renal function, but terminal renal failure is seldom seen, even after many years of disorder. Two characteristic case histories are presented. The classification of this lesion among the glomerular disorders is at present uncertain. It may represent a transitional form between minor lesion nephritis and focal segmental sclerosis, a separate disorder, or a functional lesion associated with high proteinuria. 相似文献
7.
VD Samuilov Borisov AYu EL Barsky OF Borisova AV Kitashov 《Canadian Metallurgical Quarterly》1998,46(2):333-341
Obese (Lepr(fa)/Lepr(fa)) Zucker rats have a missense mutation in the leptin receptor gene. One amino acid substitution in the extracellular domain common to all known leptin receptor proteins results from this mutation. Obese Zucker rats are unable to respond behaviorally to leptin which is peripherally administered. However, conflicting reports exist on whether obese Zucker rats can respond to centrally administered leptin. The purpose of this study was to determine whether obese Zucker rats responded behaviorally and metabolically to intracerebroventricularly (i.c.v.) administered leptin and to compare the responses of lean and obese Zucker rats. We found that both lean and obese Zucker rats had similar body weight and food intake responses when administered a single i.c.v. leptin injection in a range of doses (1.25, 2.5, 5, and 10 microg), as well as daily i.c.v. administered leptin for five consecutive days. Both single and daily leptin administration also decreased respiratory quotient (RQ) similarly in lean and obese Zucker rats, indicating mobilization of fat as an energy source for leptin-treated rats. After withdrawal of daily leptin treatment, lean and obese Zucker rats exhibited different recovery responses. It is concluded that obese Zucker rats can respond to exogenous leptin when leptin is delivered into the brain ventricles. 相似文献
8.
I. Z. Babievskaya K. S. Gavrichev N. F. Drobot O. A. Noskova N. A. Ovchinnikova A. E. Shubina V. A. Krenev 《Inorganic Materials》2007,43(3):292-295
The water adsorption and retention behaviors of vermiculite, silica gel, activated carbon, and a zeolite are analyzed in relation to their pore structures, and their effects on the dynamics of heat generation in Fe-C-NaCl-H2O-O2-water sorbent systems are investigated. 相似文献
9.
Aluminum has been reported to inhibit long-term potentiation (LTP) following in vivo administration and decrease glutamate release following in vitro exposure. Because glutamate release is critical for synaptic transmission and the development and maintenance of LTP in the hippocampus, we examined the effects of aluminum chloride (AlCl3) on depolarization-induced glutamate release and LTP in rat hippocampal slices. The effects of AlCl3 on [14C]glutamate release were examined by incubation of slices in depolarizing (56 mM)K+ buffer solution in the absence or presence of 2 mM CaCl2. After 15 min depolarization, AlCl3 (100-1000 microM) did not significantly affect Ca(2+)-dependent [14C]glutamate release from slices, whereas a known Ca2+ channel blocker (100 microM CdCl2) decreased Ca(2+)-dependent [14C]glutamate release by approximately 50%. In contrast to a previous report, acute exposure to AlCl3 was without effect on depolarization-dependent glutamate release. LTP of the population spike (PS) in CA1 of hippocampus was induced by the delivery of stimulus trains to the stratum radiatum. LTP of the PS was observed in both control slices and slices bathed in solution containing 100 microM AlCl3. Neither the magnitude nor longevity (measured up to 1 h posttrain) of LTP distinguished control from aluminum-exposed slices. The lack of sensitivity in rat to the encephalopathic changes induced by aluminum, or methodological differences in exposure conditions may account for the lack of effect of aluminum on in vitro LTP in rat hippocampus. 相似文献
10.
智能网(IN)的概念于1984年一被提出,便在世界范围内迅速掀起了IN研究的热潮,虽然至今已有十个年头,但仍可以说,IN技术的发展才刚刚起步。本文就是基于当前国际上对IN的研究,来介绍智能网的基本概念和结构,进而阐述其设计思想及主要特征,并对IN的未来发展趋势进行了探讨,最后为我国发展IN技术提出了可行建议。 相似文献