全文获取类型
收费全文 | 2299篇 |
免费 | 214篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 8篇 |
综合类 | 1篇 |
化学工业 | 499篇 |
金属工艺 | 47篇 |
机械仪表 | 50篇 |
建筑科学 | 90篇 |
矿业工程 | 1篇 |
能源动力 | 67篇 |
轻工业 | 516篇 |
水利工程 | 15篇 |
石油天然气 | 11篇 |
无线电 | 89篇 |
一般工业技术 | 381篇 |
冶金工业 | 445篇 |
原子能技术 | 5篇 |
自动化技术 | 291篇 |
出版年
2024年 | 6篇 |
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 62篇 |
2020年 | 47篇 |
2019年 | 52篇 |
2018年 | 118篇 |
2017年 | 118篇 |
2016年 | 95篇 |
2015年 | 85篇 |
2014年 | 114篇 |
2013年 | 176篇 |
2012年 | 136篇 |
2011年 | 176篇 |
2010年 | 113篇 |
2009年 | 105篇 |
2008年 | 102篇 |
2007年 | 112篇 |
2006年 | 63篇 |
2005年 | 60篇 |
2004年 | 53篇 |
2003年 | 54篇 |
2002年 | 35篇 |
2001年 | 20篇 |
2000年 | 23篇 |
1999年 | 32篇 |
1998年 | 154篇 |
1997年 | 104篇 |
1996年 | 58篇 |
1995年 | 31篇 |
1994年 | 37篇 |
1993年 | 29篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1977年 | 3篇 |
1976年 | 18篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有2516条查询结果,搜索用时 104 毫秒
11.
M Pan J Suárez de Lezo A Medina M Romero E Hernández J Segura F Melian F Wangüemert M Landin F Benítez M Amat F Velasco A Torres 《Canadian Metallurgical Quarterly》1997,80(10):1336-1338
Two hundred twenty-eight patients with successful coronary stent implantation were randomized either to protamine administration and femoral sheath removal (group I, n = 117) or no heparin neutralization and delayed sheath removal (group II, n = 111). The hospital stay after treatment was shorter in patients receiving protamine; therefore, protamine use for neutralizing circulating heparin may be safely administered immediately after stent implantation. 相似文献
12.
13.
14.
Ingrid Martorell Francesc X Grau 《International Journal of Heat and Mass Transfer》2003,46(13):2389-2402
The present work deals with the natural convection flow and heat transfer from a horizontal plate cooled from above. Experiments are carried out for rectangular plates having aspect ratios between φ=0.036 and 0.43 and Rayleigh numbers in the range 290?Raw?3.3×105. These values of Raw and φ have been selected below those commonly considered in previous research in view of a future application to the design of printed circuit boards. The plates are made of two different metals, copper and steel. The choice of a metal is relevant to the present problem because the plates are heated by means of an electric current. Important variations of the surface temperature are observed along the transverse direction for the steel plates. The surface of the copper plates is almost isothermal because of the high thermal conductivity of the metal.Calculations for a semi-infinite plate are carried out to predict the transverse profiles of the surface temperature and heat flux and to visualize the structure of the flow. Three-dimensional calculations are also used at a qualitative level to observe the changes in the flow structure due to the finite length of the plate. Present results are compared with both previous experimental work and analyses that are based on boundary layer theory. It is shown that analyses for an infinite boundary layer are not completely applicable to the present problem because of its different physics. The most relevant feature of the natural convection flow, which is not predicted by boundary layer analyses, is a thermal plume rising near the center of the plate.Present heat transfer results differ from previous experimental work because of the lower Rayleigh numbers and aspect ratios investigated here. The Nusselt number is found to depend on Rawn, with the exponent n=0.17 being lower than most of the values reported in the literature. This comparatively low value is related to the transverse conduction of heat through the air, which becomes increasingly significant as Raw approaches zero. It is shown that such a low-Raw effect can be accounted for in a physically consistent manner by adding a constant term to the heat transfer correlation. On the other hand, it is found that the Nusselt number does not significantly depend on the aspect ratio in the range of φ investigated contrary to what has been previously reported for wider plates. 相似文献
15.
JC Hernández Guerrero J Portilla Robertson C Ledezma Montes S Ponce-Bravo A Miranda Gómez EM Arias Rivera 《Canadian Metallurgical Quarterly》1996,44(1-4):25-30
Several forms of cell perturbation have been associated with ethanol ingestion. Fetal alcohol syndrome (FAS) as well as diminished maxillofacial development and inhibition of cell regeneration in vitro and in vivo have been described. Epidermal growth factor (EGF) stimulates maxillofacial growth, DNA synthesis, and it is a potent mitogen for a number of various cell types. EGF exerts its effects on cells through binding to a specific cell surface receptor which leads to activation of a thyrosine kinase in the intracellular part of the receptor. The inhibitory effect of alcohol on EGF in the mouse dental follicle was studied in the offspring of alcoholic mothers using immunocytochemistry. Adult female mice were given 22% alcohol in their drinking water and fed a pelleted diet before and during pregnancy. Maternal blood alcohol levels were 262 +/- 1.3 mg/100 ml on gestation day 12.5. The offspring of the alcoholic and control mice were sacrificed on postnatal day 1.5, their mandibles were dissected, weighed and processed by routine immunocytochemistry with the following results. 1) Significant differences were found in mandible weight p < 0.01 after parturition. 2) The tooth germs in the offspring of ethanol treated mice were morphometrically smaller than those of control littermates. 3) Immunoexpression of EGF in the mandibular first molar of the control group was strong and homogeneous while in the experimental group the expression was light and heterogeneous. It is concluded that maternal alcoholism reduces EGF in the offspring. 相似文献
16.
17.
Sebastián Bruque-Cámara Alfonso Vargas-Sánchez M. Jesús Hernández-Ortiz 《欧洲信息系统杂志》2004,13(2):133-146
The aim of this paper is to propose new organizational factors that might explain the differences in the extent and the speed of IT adoption. With this in mind, we carried out an analysis of 16 cases in the pharmaceutical distribution sector in Spain. The results indicate that there are certain intangible assets that favour the introduction and development of IT. Among these are a frank and fluid communication between departments and members of the organization, low levels of conflict, the explicit support of top management towards IT adoption and learning and creative skills of IT-staff. In addition to these factors, we found others that we propose as catalysts of IT adoption. Among these we might mention the special relationship between the member-clients and the company in the case of cooperative firms. 相似文献
18.
E Montserrat J García-Conde N Vi?olas A López-Guillermo L Hernández-Nieto A Zubizarreta J Maldonado A Alcalá MV Faura A Llorente J Bladé M Fontanillas J Estapé 《Canadian Metallurgical Quarterly》1996,57(5):377-383
From May 1985 to May 1989, 175 patients with previously untreated aggressive non-Hodgkin's lymphoma were randomized to receive CHOP or ProMACE-CytaBOM. Eligibility criteria included follicular large-cell diffuse small cleaved-cell, diffuse mixed, diffuse large-cell and immunoblastic lymphoma with an Ann Arbor stage II, III or IV. One hundred and forty-eight patients were evaluable. There were no significant differences between the 2 treatments in response rate (83.5% [57.5% CR] for CHOP vs. 88% [62% CR] for ProMACE-CytaBOM), time to treatment failure (29% vs. 31% at 5 yr), or overall survival (42% in both groups at 5 yr). Furthermore, there were no significant differences between the 2 regimens when response rates and outcome were analyzed for different prognostic subgroups. Toxicity was not significantly different between the 2 regimens, although only 1 patient died as result of treatment-related toxicity in the CHOP arm compared to 6 patient in the ProMACE-CytaBOM group (p = 0.126). In conclusion, in this study ProMACE-CytaBOM has not proved to be superior to CHOP in aggressive lymphomas. This trial gives support to the notion that CHOP still is the standard chemotherapy for aggressive lymphomas, and that new treatment approaches for these lymphomas should be compared to CHOP. 相似文献
19.
20.