全文获取类型
收费全文 | 404470篇 |
免费 | 4701篇 |
国内免费 | 1364篇 |
专业分类
电工技术 | 7569篇 |
综合类 | 316篇 |
化学工业 | 60002篇 |
金属工艺 | 16465篇 |
机械仪表 | 13505篇 |
建筑科学 | 8377篇 |
矿业工程 | 2155篇 |
能源动力 | 11555篇 |
轻工业 | 28509篇 |
水利工程 | 4268篇 |
石油天然气 | 7915篇 |
武器工业 | 17篇 |
无线电 | 49295篇 |
一般工业技术 | 83082篇 |
冶金工业 | 75166篇 |
原子能技术 | 9190篇 |
自动化技术 | 33149篇 |
出版年
2022年 | 2552篇 |
2021年 | 3889篇 |
2020年 | 2951篇 |
2019年 | 3815篇 |
2018年 | 6492篇 |
2017年 | 6485篇 |
2016年 | 6942篇 |
2015年 | 4324篇 |
2014年 | 7147篇 |
2013年 | 20052篇 |
2012年 | 11433篇 |
2011年 | 15297篇 |
2010年 | 12155篇 |
2009年 | 13731篇 |
2008年 | 14083篇 |
2007年 | 13830篇 |
2006年 | 12432篇 |
2005年 | 11125篇 |
2004年 | 10532篇 |
2003年 | 10431篇 |
2002年 | 9842篇 |
2001年 | 9744篇 |
2000年 | 9148篇 |
1999年 | 9545篇 |
1998年 | 24399篇 |
1997年 | 16745篇 |
1996年 | 12819篇 |
1995年 | 9545篇 |
1994年 | 8384篇 |
1993年 | 8396篇 |
1992年 | 6064篇 |
1991年 | 5700篇 |
1990年 | 5692篇 |
1989年 | 5323篇 |
1988年 | 5050篇 |
1987年 | 4432篇 |
1986年 | 4308篇 |
1985年 | 4826篇 |
1984年 | 4427篇 |
1983年 | 4001篇 |
1982年 | 3660篇 |
1981年 | 3734篇 |
1980年 | 3433篇 |
1979年 | 3337篇 |
1978年 | 3340篇 |
1977年 | 3757篇 |
1976年 | 4859篇 |
1975年 | 2850篇 |
1974年 | 2666篇 |
1973年 | 2736篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
S I Barr 《Progress in food & nutrition science》1987,11(3-4):307-361
Given the heightened interest in nutritional aspects of exercise, and an increase in athletic participation by women, it appeared timely to review the nutritional implications of exercise in women. The initial part of this paper contains a compilation of published studies on the nutrient intakes of female athletes. These reveal that most groups of athletes have adequate nutrient intakes, and that their vitamin and mineral intakes appear to be superior to those of nonathletic women. The average energy intake of athletes in studies summarized in this paper was 2069 kcal, and for certain groups of athletes, energy intakes were even lower. How these women manage to train intensely while consuming energy intakes similar to those of sedentary women is not readily apparent, and for this reason, the remainder of the paper discusses energy balance as affected by activity. Methodological considerations related to assessment of the components of the energy balance equation (food intake, energy expenditure, and body energy stores) are presented, with a focus on considerations in women. The effects of activity on each of these components are then discussed in an attempt to determine whether some form of energy conservation may occur. Finally, effects of activity on the menstrual cycle are reviewed. The observed changes are discussed in relation to nutrition 1) in terms of how nutrition may play a role in their causation; and 2) in terms of their nutritional implications for the amenorrheic athlete, specifically as regards energy balance and bone density. 相似文献
152.
O Prez‐Camacho S Sepúlveda‐Guzmn M Prez‐lvarez M García‐Zamora G Cadenas‐Pliego 《Polymer International》2005,54(12):1626-1631
New functionalized styrene–maleimide copolymers were prepared by free radical copolymerization of styrene (St) and N‐4‐carboxybutylmaleimide (NBMI) in chloroform, using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. Monomer and copolymer characterization was carried out by 1H‐ and 13C‐NMR. Copolymer composition was determined by elemental analysis and Fourier‐transform infrared (FTIR) spectroscopy. The glass transition temperature (from DSC) and the thermogravimetric analysis (TGA) of the copolymers were consistent with the thermal behavior and stability observed for alternating St–maleimide copolymers. St–NBMI copolymers crosslinked with divinylbenzene (DVB) were also synthesized and their cation exchange properties evaluated in order to assess the capacity of the new copolymers to bind metallic ions. Copyright © 2005 Society of Chemical Industry 相似文献
153.
Analysis and synthesis of on-chip spiral inductors 总被引:3,自引:0,他引:3
This paper presents a physically based compact model for estimating high-frequency performance of spiral inductors. The model accurately accounts for skin and proximity effects in the metal conductors as well as eddy current losses in the substrate. The model shows excellent agreement with measured data mostly within 10% across a variety of inductor geometries and substrate dopings up to 20 GHz. A web-based spiral inductor synthesis and analysis tool COILS, which makes use of the compact models, is presented. An optimization algorithm using binary searches speeds up the synthesis of inductor designs. 相似文献
154.
155.
A method for assessing the differential risk of failure among a system's modules is proposed. The procedure has three components: external-risk assessment, module exposure, and module-failure likelihood. External-risk assessment is a consideration of the system's environment, almost independent of the software's details. To estimate module exposure, the model relates individual modules and their potential faults to the external-failure modes and their economic consequences by reverse-engineering the specifications and analyzing each module's expected use. To estimate failure likelihood, the method uses a reliability model. The method constitutes theoretical foundation for the cost-effective development of software that attempts to reduce the risk of failure. Managers can use the failure-risk estimates to better determine how much testing effort can be economically justified 相似文献
156.
157.
158.
The study suggests improvements in the design of new houses to conserve energy and enhance indoor thermal comfort. Summer temperature records show that a new house has an average indoor temperature of 35°C with the ambient average 31°C. The traditional house in the old city recorded 28°C for the same period. Winter temperatures in both types of houses were similar (12°C) when not occupied. Architectural features of the two houses were compared to identify those responsible for difference in the thermal performance. Larger exposed surface and window areas, higher overall heat transfer coefficient and weaker thermal coupling with the ground for the new houses seems to contribute to their inferior thermal performance. 相似文献
159.
Pull-out experiments have been carried out on single production fibres under carefully controlled conditions. Four parameters were determined. The interfacial yield stresses, of about 9–14 MPa, were very much smaller than the shear strengths of the bulk polymers in the case of an epoxy, whether post-cured or not, and a non-post-cured polyester. Values for the work of fracture of the interface varied from 140 to 300 Jm?2, and again were less than those of the polymer. Interface failure sometimes took place in the epoxy rather than at the fibre surface, whereas with the polyester it always took place at the fibre surface. After interface failure, pull-out was governed by friction, with maximum shear stresses of 7–10 MPa for polyester, and 21–34 MPa for epoxy, the higher values being obtained for the post-cured resins. Average frictional shear stresses were sometimes less than a half of the maximum shear stress, indicating that the fibre Poisson's shrinkage was playing an important role in the pull-out process. A silicone release agent reduced the frictional shear stresses to 2·5 MPa, with both resins. 相似文献
160.
I. S. Panidi V. A. Trofimov N. S. Lepikhina 《Chemistry and Technology of Fuels and Oils》2006,42(6):440-445
Equations are proposed for calculating the molar volume of liquid hydrocarbons used in production of surfactants. With such
data, it will be possible to calculate most of the physicochemical properties of these hydrocarbons to solve many process
problems.
__________
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 6, pp. 39–41, Novemmber–December, 2006. 相似文献