全文获取类型
收费全文 | 528篇 |
免费 | 8篇 |
专业分类
电工技术 | 35篇 |
化学工业 | 133篇 |
金属工艺 | 11篇 |
机械仪表 | 7篇 |
建筑科学 | 6篇 |
矿业工程 | 1篇 |
能源动力 | 4篇 |
轻工业 | 40篇 |
无线电 | 71篇 |
一般工业技术 | 77篇 |
冶金工业 | 89篇 |
原子能技术 | 17篇 |
自动化技术 | 45篇 |
出版年
2022年 | 3篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 25篇 |
2012年 | 19篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 8篇 |
2007年 | 18篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 14篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 19篇 |
1998年 | 34篇 |
1997年 | 32篇 |
1996年 | 12篇 |
1995年 | 22篇 |
1994年 | 10篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 12篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1972年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有536条查询结果,搜索用时 15 毫秒
71.
We discuss theoretically how the resistance of a film deposited on the metal grid affects the efficiency of electron-temperature control by employing a grid-bias method, in which, by using a naked metal grid, the electron temperature decreases from 3.4 to 0.12 eV with a decrease in the grid potential from 40 to − 60 V, being accompanied by an electron-density increase from 0.6 × 109 cm− 3 to 6.0 × 109 cm− 3 at an argon gas pressure of 5.0 mTorr. The electron temperature can be varied even when the grid is covered with a film with finite resistance, although the range of electron temperature variation is restricted. This method is applicable to reactive plasmas in which grids are often covered by films with finite resistance. 相似文献
72.
To investigate the mechanism of nitroso compound-induced inhibition of the respiratory burst in neutrophils, we studied fluorescence quenching of perylene by nitroso-compounds in the membrane fractions of neutrophils at 17, 27, and 37 degrees C and the reagent-induced inhibition of superoxide generation at 28 and 37 degrees C. With increasing temperature, the quenching of perylene fluorescence and inhibition of superoxide generation by nitrosobenzene (NB) were both diminished, while those by 2-nitrosotoluene (NT) were both enhanced. The temperature dependence of the inhibition constants and the quenching constants indicates that the binding of NB is exothermic (deltaH= -27 kJ/mol for inhibition and deltaH= -29 kJ/mol for quenching) and essentially enthalpy-driven. On the other hand, that of NT is endothermic (deltaH= +16 kJ/mol for inhibition and quenching) and essentially entropy-driven. Quenching studies of perylene fluorescence in synthetic vesicles made of endogenous polar lipids of neutrophils showed that the enthalpy changes of NB- and NT-binding with perylene in lipids were similar to each other. Moreover, their values were in good agreement with that of NT, but not of NB, in the membrane fractions, an assembly of proteins and lipids, of neutrophils. These results suggest that NB inhibits the activity by binding to proteins in the membrane, whereas inhibition by NT occurs through hydrophobic interaction with lipids and/or proteins. 相似文献
73.
Semiclassical laser theory is rigorously applied to semiconductor lasers in order to obtain both the complete TE and TM linear gain. The resulting expressions for the modal gain in heterostructure lasers differ in form from those conventionally accepted. In particular, the conventional modal gain written as the product of a confinement factor and a bulk gain is only an approximation of the true modal gain derived. The conventional expression relies on an explicit definition of the active region of the laser, which can be ambiguous when certain heterostructures, such as parabolic quantum wells, are to be treated. This ambiguity is eliminated by the gain expressions as a more natural active region defined by the product of electron and hole wave functions emerges. The relevant approximations which allow the newly derived gain equations to be written in forms similar to the conventional expressions for single quantum well, multiquantum well (MQW), and in wide active region lasers are explicitly shown 相似文献
74.
T Anindyawati H Yamaguchi K Furuichi M Iizuka N Minamiura 《Canadian Metallurgical Quarterly》1995,59(11):2146-2148
An alpha-glucosidase was purified in an electrophoretically pure state from an extract of koji culture of Aspergillus sp. KT-11. This enzyme was found to have a transferring activity when the reaction was done in a high concentration of leucrose at pH 4.5. Two kinds of transfer products, fractions I and II, were obtained from leucrose by the enzyme and they were identified as [(alpha-D-glucopyranosyl-(1-->6)-alpha-D-glucopyranosyl-(1-->6)-alpha-D- glucopyranosyl-(1-->5)-D-fructopyranose] and [alpha-D-glucopyranosyl-(1-->6)-alpha-D-glucopyranosyl-(1-->5)-D- fructopyranose], respectively. These are considered to be novel oligosaccharides. 相似文献
75.
Machiko Shimada Shoji Takigami Yoshio Nakamura Yukio Abe Toshi Iizuka Nobusuke Makiyama 《应用聚合物科学杂志》1993,48(6):1121-1126
Graft copolymerization of methyl methacrylate onto novoloid fiber was carried out by the electron beam mutual irradiation method. The characteristics of the grafted fiber were almost the same as those of the original novoloid fiber. The grafted fiber was carbonized and activated to yield an efficiently activated carbon fiber. The yield and the specific surface area of the activated carbon fiber, derived from the grafted novoloid fiber, were much greater than those derived from the original novoloid fiber. This is because grafted poly(methyl methacrylate) decomposes into monomer and gaseous products, forming pores on the surface and inside of the novoloid fiber on heating. © 1993 John Wiley & Sons, Inc. 相似文献
76.
I Chiba M Muthumala Y Yamazaki A Uz Zaman T Iizuka A Amemiya T Shibata H Kashiwazaki C Sugiura H Fukuda 《Canadian Metallurgical Quarterly》1998,77(6):839-842
The PCR copy of the ribR gene of Bacillus subtilis was subcloned in Escherichia coli cells under the control of the phage T7 inducible promoter. The polypeptide of 26 kDa corresponding to the 690-bp gene is the product of the ribR gene. The protein encoded by the ribR gene is flavokinase, and the riboflavin-reduced form is the substrate for it. 相似文献
77.
K Kusumoto K Bessho K Fujimura Y Konishi Y Ogawa T Iizuka 《Canadian Metallurgical Quarterly》1996,24(6):360-365
A combination of recombinant human bone morphogenetic protein-2 (rhBMP-2), atelopeptide Type I collagen (CL) as a carrier and porous hydroxyapatite (pHAP) was implanted in a calf muscle pouch of the rat. Three rhBMP-2-implanted groups (2, 10 and 50 micrograms; each n = 5) and the control group (n = 5), in which only CL and pHAP were implanted, were established. Three weeks later, the implants were examined. 相似文献
78.
SC Marks T Iizuka CA MacKay A Mason-Savas MJ Cielinski 《Canadian Metallurgical Quarterly》1997,29(5):589-595
The role of colony-stimulating factor-1 (CSF-1 or M-CSF) in osteoclast development is illustrated by observations that administration of exogenous CSF-1 increases osteoclast number and improves the skeletal sclerosis of two osteopetrotic mutations, toothless (tl) in the rat and osteopetrotic (op) in the mouse. We examined the effects of CSF-1 treatment on the number and ultrastructure of osteoclasts in the tibial metaphysis of normal and mutant animals of both stocks to understand the similarities and differences between these two mutations. Osteoclasts from normal animals of both stocks were abundant and possessed the ultrastructural features of active cells. These included apical areas in contact with mineralized surfaces with tightly apposed clear zones, extensive ruffled borders, and a vacuolated cytoplasm with numerous mitochondria. In toothless rats osteoclasts were difficult to locate and those present had poorly defined ruffled borders, fewer cytoplasmic vacuoles, and a basal membrane with both smooth and ruffled areas. Large lipid accumulations were often found near tl osteoclasts. Osteoclasts in op mice were difficult to find, but more numerous than in tl rats. Unlike tl osteoclasts, those of op mice possessed very well developed ruffled borders, small clear zones, and large electron-dense cytoplasmic inclusions. These cells also had unusual basal membranes with both smooth and ruffled regions. CSF-1 treatment increased the number of osteoclasts in both mutant stocks, normalizing the numbers in op mice, but not tl rats. CSF-1 injections caused dramatic changes in the morphology of tl osteoclasts, including increased incidence and size of ruffled borders and cytoplasmic vacuolization. The growth factor had little effect on ruffled borders or clear zones in op mice. Interestingly, mutant osteoclasts of both stocks exhibited a ruffled basal membrane in response to CSF-1 treatment. This increase in membrane ruffling may reflect the ability of CSF-1 to promote rapid formation of osteoclasts from mononuclear precursors in a more permissive microenvironment. Our data indicate that CSF-1 is not required for the development of at least some osteoclasts. The differences in response to CSF-1 treatment which we report lead us to speculate that additional factors may be involved in osteoclastogenesis. 相似文献
79.
The effects of serrated grain boundaries on the creep-rupture properties of wrought cobaltbase HS-21 alloys were investigated at 1311 and 1422 K. The amount of grain-boundary sliding and the initiation and growth of grain-boundary cracks were also examined during creep at 1311 K. Specimens with serrated grain boundaries exhibited longer rupture life and larger rupture ductility than those with straight grain boundaries, but these specimens had almost the same rupture life and rupture ductility under lower stresses at 1422 K, because serrated grain boundaries were also formed in specimens with originally straight grain boundaries. The average amount of grain-boundary sliding during creep at 1311 K increased with time (or with creep strain), but was almost the same in both specimens with serrated grain boundaries and those with straight grain boundaries at the same creep strain. Grain-boundary cracks or voids initiated in the early stage of creep in those specimens at 1311 K. Therefore, the strengthening by serrated grain boundaries at high temperatures above about 1311 K was attributed to the retardation of growth and linkage of grain-boundary cracks and voids. 相似文献
80.
T Kitagawa M Kakehi T Kunieda I Tsukiyama M Hamada H Inakoshi M Sakudo K Suemasu K Matsumoto T Yoneyama T Iizuka K Nomura K Kawachi 《Canadian Metallurgical Quarterly》1982,143(2):543-547
An afterloading procedure using iridium 192 seeds was developed for the control of both localized primary lesions that are difficult to remove and superficial residual lesions that remain after the partial removal of tumors in relatively inaccessible, deep-seated organs. This technique makes possible the delivery of a minimal radiation dose to lesions in deep-seated organs. Fewer complications result, the seeds can be adjusted at appropriate intervals in proportion to the amount of radioactivity desired, and radiation exposure to personnel can be reduced. This paper describes the techniques and apparatus used to place the seeds in the tubing. Primary lesions of the urinary bladder, the prostate gland, and the esophagus, residual lesions in the brain and lung, and metastases in intrapelvic lymph nodes were treated. No technical difficulties or complications were encountered. Radiation exposures to personnel were minimized. The results indicate that the procedure has practical applications. 相似文献