全文获取类型
收费全文 | 266320篇 |
免费 | 2824篇 |
国内免费 | 1238篇 |
专业分类
电工技术 | 4684篇 |
综合类 | 183篇 |
化学工业 | 40565篇 |
金属工艺 | 12774篇 |
机械仪表 | 9013篇 |
建筑科学 | 5392篇 |
矿业工程 | 2505篇 |
能源动力 | 6257篇 |
轻工业 | 18547篇 |
水利工程 | 3606篇 |
石油天然气 | 9265篇 |
武器工业 | 61篇 |
无线电 | 27353篇 |
一般工业技术 | 58064篇 |
冶金工业 | 44744篇 |
原子能技术 | 8623篇 |
自动化技术 | 18746篇 |
出版年
2021年 | 2724篇 |
2019年 | 2574篇 |
2018年 | 4773篇 |
2017年 | 4834篇 |
2016年 | 5265篇 |
2015年 | 2976篇 |
2014年 | 4955篇 |
2013年 | 11638篇 |
2012年 | 7480篇 |
2011年 | 9453篇 |
2010年 | 7710篇 |
2009年 | 8582篇 |
2008年 | 8721篇 |
2007年 | 8546篇 |
2006年 | 7302篇 |
2005年 | 6611篇 |
2004年 | 6135篇 |
2003年 | 6004篇 |
2002年 | 5763篇 |
2001年 | 5860篇 |
2000年 | 5584篇 |
1999年 | 5521篇 |
1998年 | 13394篇 |
1997年 | 9415篇 |
1996年 | 7191篇 |
1995年 | 5463篇 |
1994年 | 4774篇 |
1993年 | 5008篇 |
1992年 | 3803篇 |
1991年 | 3859篇 |
1990年 | 3767篇 |
1989年 | 3707篇 |
1988年 | 3620篇 |
1987年 | 3200篇 |
1986年 | 3253篇 |
1985年 | 3587篇 |
1984年 | 3313篇 |
1983年 | 3166篇 |
1982年 | 2845篇 |
1981年 | 2812篇 |
1980年 | 2860篇 |
1979年 | 2876篇 |
1978年 | 2859篇 |
1977年 | 3112篇 |
1976年 | 3672篇 |
1975年 | 2638篇 |
1974年 | 2498篇 |
1973年 | 2599篇 |
1972年 | 2315篇 |
1971年 | 2114篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
61.
D Sternberg A Peled E Shezen O Abramsky W Jiang F Bertolero D Zipori 《Canadian Metallurgical Quarterly》1996,2(1):29-38
The immunological agglutination reactions of physically absorbed F(ab')2 molecules onto anionic and cationic latex particles have been investigated by means of optical absorbance measurements. These measurements have been conducted under different conditions to determine the most influential factors. Surface F(ab')2 and BSA densities, particle concentration in the reaction medium and polyethylene glycol concentration are some of these factors. Sensitized cationic and anionic latexes differ considerably with respect to their colloidal stability and reactivity. As a general rule, the sensitized cationic latex has a relatively higher colloidal stability and hence, it provides reagents with a better optical response. Less than 0.025 microgram/ml of C-reactive protein has been detected using this particle enhanced optical immunoassay. 相似文献
62.
Known examples of the positive influence of electrohydroimpulse treatment on the quality of weld joints of various steels, particularly including an increase in their long-term and cyclic strength and also corrosion resistance, are analyzed. It is shown that in this case there is a reduction in residual macro- and micro-stresses and also a change in the parameters of the dislocation structure of the joint metal in the direction of stabilization of it.Translated from Problemy Prochnosti, No. 4, pp. 119–123, April, 1996. 相似文献
63.
64.
O. A. Ustrekhova T. G. Ezhikova-Babakhanova G. B. Basov 《Chemistry and Technology of Fuels and Oils》1993,29(11):544-548
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 11, pp. 17–18, 23, November, 1993. 相似文献
65.
N Usui S Kamata S Ishikawa T Sawai H Okuyama K Imura A Okada 《Canadian Metallurgical Quarterly》1996,31(2):258-262
Bone marrow examination revealed a lipid-laden histiocytosis in seven patients undergoing long-term total parenteral nutrition necessitated by extensive short-bowel surgical resection. Clinical abnormalities occurred during this treatment which required bone marrow examination. These included hepatosplenomegaly and peripheral blood cytopenia; the median time to the detection of these abnormalities was 64 months. The most striking change within the bone marrow was the presence of many pigment-laden histiocytes which had the typical morphology of sea-blue histiocytes seen in the so-called idiopathic sea-blue histiocyte syndrome. The occurrence of sea-blue histiocytosis in the bone marrow in association with long-term parenteral nutrition for short-bowel syndrome has not, to our knowledge, been reported previously and should now be considered in the differential diagnosis of bone marrow sea-blue histiocytosis. 相似文献
66.
A low threshold current density of ~100 A/cm2 has been obtained at 1.55 μm using a graded-index separate-confinement-heterostructure strained InGaAsP single-quantum-well laser. The design of the laser structure is based on results calculated from the viewpoint of effective carrier injection into the well 相似文献
67.
A.G. Berkovski G. Chiodi J.-P. Fabre A. Frenkel S.V. Golovkin Yu.I. Gubanov G.N. Kislizkai E.N. Kozarenko I.E. Kreslo A.E. Kushnirenko G. Martellotti D. Mazza A.M. Medvedkov G. Penso 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,380(3):537-543
We present the performance of a high-speed gateable vacuum image pipeline, which permits individual images to be delayed and selected from continuous non-repetitive image stream. This device is composed of a vacuum tube equipped with a photocathode at one end, a phosphor screen at the other end, and a system of metal grids in between. Photoelectrons produced by the images focused on the photocathode, are guided by a uniform magnetic field, parallel to the tube axis. By changing the grid potentials, the drift time of the photoelectrons inside the tube can be varied from 0.35 to 1.5 μs. An image can then be selected by an external trigger with a time resolution in the range of 4–30 ns, depending on the delay time. The selected photoelectrons are finally accelerated onto the phosphor screen, set at 10 kV, where they reproduce the desired image. With a magnetic field of 0.1 T, a spatial resolution of 33 lp/mm was obtained. The high spatial and time resolution make this device an interesting tool for high-energy physics and astrophysics experiments, and for high-speed photography. 相似文献
68.
69.
Results are reported of a detailed optical and electron metallographic study of the effects of variations in quenching rate from the β-phase and aging temperature in the + ZrCr2 phase region, on the recrystallization and grain growth characteristics of Zr-1.14 wt% Cr-0.08 wt% Fe alloy used for nuclear fuel sheathing. It is shown that certain quenching rates, which produce a mixed martensitic-Widmanstätten structure, should be avoided during the fabrication of fuel sheathing, since recrystallization and grain growth occurs at a much lower temperature than a material quenched at such a rate that the structure is wholly Widmanstätten or wholly martensitic. Preaging at 350 or 450°C prior to the high-temperature (700–750°C) aging reduces the incidence of recrystallization and grain growth. 相似文献
70.
The article describes the experience of implementing patient-focused care from a physician's perspective. Pitfalls that guarantee failure are presented, many of which are avoidable with early participation by all parties involved: administrators, nursing staff, physicians, and patients. Contamination of the process with downsizing needs, lack of support for staff in dealing with necessary change, loss of administrative commitment, and withholding of appropriated funds are among the key errors to be avoided. 相似文献