全文获取类型
收费全文 | 428628篇 |
免费 | 4898篇 |
国内免费 | 1727篇 |
专业分类
电工技术 | 7900篇 |
综合类 | 391篇 |
化学工业 | 64624篇 |
金属工艺 | 20292篇 |
机械仪表 | 13456篇 |
建筑科学 | 9851篇 |
矿业工程 | 2621篇 |
能源动力 | 10347篇 |
轻工业 | 35236篇 |
水利工程 | 4579篇 |
石油天然气 | 8947篇 |
武器工业 | 25篇 |
无线电 | 49515篇 |
一般工业技术 | 85892篇 |
冶金工业 | 79481篇 |
原子能技术 | 10085篇 |
自动化技术 | 32011篇 |
出版年
2021年 | 3465篇 |
2019年 | 3295篇 |
2018年 | 5766篇 |
2017年 | 5714篇 |
2016年 | 6166篇 |
2015年 | 3945篇 |
2014年 | 6612篇 |
2013年 | 18666篇 |
2012年 | 10529篇 |
2011年 | 14251篇 |
2010年 | 11546篇 |
2009年 | 12807篇 |
2008年 | 13456篇 |
2007年 | 13437篇 |
2006年 | 11961篇 |
2005年 | 10981篇 |
2004年 | 10321篇 |
2003年 | 10294篇 |
2002年 | 10094篇 |
2001年 | 10298篇 |
2000年 | 9482篇 |
1999年 | 10000篇 |
1998年 | 24658篇 |
1997年 | 17439篇 |
1996年 | 13585篇 |
1995年 | 10214篇 |
1994年 | 8949篇 |
1993年 | 9048篇 |
1992年 | 6716篇 |
1991年 | 6670篇 |
1990年 | 6210篇 |
1989年 | 6079篇 |
1988年 | 6078篇 |
1987年 | 5226篇 |
1986年 | 5236篇 |
1985年 | 6038篇 |
1984年 | 5551篇 |
1983年 | 5137篇 |
1982年 | 4696篇 |
1981年 | 4691篇 |
1980年 | 4600篇 |
1979年 | 4501篇 |
1978年 | 4500篇 |
1977年 | 5163篇 |
1976年 | 6869篇 |
1975年 | 4000篇 |
1974年 | 3776篇 |
1973年 | 3859篇 |
1972年 | 3335篇 |
1971年 | 3013篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
In summary, recent literature indicates that the complications of chronic otitis media have been decreasing. However, even with the advent of modern and more powerful antimicrobials and aggressive surgical eradication of disease, the morbidity and mortality are still high. Some complications may initially be quite obvious and some complications may be quite subtle. Therefore, the most important tools in making early diagnosis are careful history and physical examination, and a high index of suspicion for impending complications. 相似文献
122.
Modeling ion implantation of HgCdTe 总被引:2,自引:0,他引:2
H. G. Robinson D. H. Mao B. L. Williams S. Holander-Gleixner J. E. Yu C. R. Helms 《Journal of Electronic Materials》1996,25(8):1336-1340
Ion implantation of boron is used to create n on p photodiodes in vacancy-doped mercury cadmium telluride (MC.T). The junction
is formed by Hg interstitials from the implant damage region diffusing into the MC.T and annihilating Hg vacancies. The resultant
doping profile is n+/n-/p, where the n+ region is near the surface and roughly coincides with the implant damage, the n- region is where Hg vacancies have been annihilated revealing a residual grown-in donor, and the p region remains doped by
Hg vacancy double acceptors. We have recently developed a new process modeling tool for simulating junction formation in MC.T
by ion implantation. The interstitial source in the damage region is represented by stored interstitials whose distribution
depends on the implant dose. These interstitials are released into the bulk at a constant, user defined rate. Once released,
they diffuse away from the damage region and annihilate any Hg vacancies they encounter. In this paper, we present results
of simulations using this tool and show how it can be used to quantitatively analyze the effects of variations in processing
conditions, including implant dose, annealing temperature, and doping background. 相似文献
123.
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
124.
125.
126.
BACKGROUND AND DESIGN: Giant aggressive keratoacanthoma is a rare destructive subset of keratoacanthoma that frequently involves the facial region, grows rapidly to a large size, and often recurs after surgical management. The effectiveness of ionizing radiation therapy was examined in a retrospective study involving 16 patients; 14 of the tumors had recurred after surgical therapy. RESULTS: All tumors resolved with satisfactory cosmetic results and without recurrence following a fractionated course of superficial radiation therapy. CONCLUSIONS: Radiation therapy is an effective therapeutic modality for giant aggressive keratoacanthomas. 相似文献
127.
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
128.
129.
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
130.
T P?usa P Górski H Frank-Piskorska M Kowalski J Kruszewski P Kuna M Kurek R Kurzawa W Silny E Zawisza 《Canadian Metallurgical Quarterly》1996,1(4):292-293
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre. 相似文献