全文获取类型
收费全文 | 2156篇 |
免费 | 56篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 15篇 |
综合类 | 6篇 |
化学工业 | 308篇 |
金属工艺 | 76篇 |
机械仪表 | 26篇 |
建筑科学 | 74篇 |
矿业工程 | 5篇 |
能源动力 | 48篇 |
轻工业 | 214篇 |
水利工程 | 16篇 |
无线电 | 214篇 |
一般工业技术 | 274篇 |
冶金工业 | 695篇 |
原子能技术 | 20篇 |
自动化技术 | 223篇 |
出版年
2021年 | 30篇 |
2020年 | 17篇 |
2019年 | 21篇 |
2018年 | 36篇 |
2017年 | 38篇 |
2016年 | 50篇 |
2015年 | 22篇 |
2014年 | 38篇 |
2013年 | 83篇 |
2012年 | 53篇 |
2011年 | 85篇 |
2010年 | 64篇 |
2009年 | 65篇 |
2008年 | 85篇 |
2007年 | 83篇 |
2006年 | 73篇 |
2005年 | 62篇 |
2004年 | 59篇 |
2003年 | 44篇 |
2002年 | 50篇 |
2001年 | 55篇 |
2000年 | 35篇 |
1999年 | 35篇 |
1998年 | 156篇 |
1997年 | 93篇 |
1996年 | 78篇 |
1995年 | 53篇 |
1994年 | 43篇 |
1993年 | 59篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 24篇 |
1989年 | 24篇 |
1988年 | 24篇 |
1987年 | 29篇 |
1986年 | 17篇 |
1985年 | 26篇 |
1984年 | 28篇 |
1983年 | 28篇 |
1982年 | 24篇 |
1981年 | 12篇 |
1980年 | 21篇 |
1979年 | 12篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 28篇 |
1975年 | 34篇 |
1974年 | 16篇 |
1973年 | 14篇 |
1972年 | 15篇 |
排序方式: 共有2214条查询结果,搜索用时 15 毫秒
51.
Scott J. Cobb; Woods Steven Paul; Vigil Ofilio; Heaton Robert K.; Schweinsburg Brian C.; Ellis Ronald J.; Grant Igor; Marcotte Thomas D. 《Canadian Metallurgical Quarterly》2011,25(4):511
Objective: A subset of individuals with HIV-associated neurocognitive impairment experience related deficits in “real world” functioning (i.e., independently performing instrumental activities of daily living [IADL]). While performance-based tests of everyday functioning are reasonably sensitive to HIV-associated IADL declines, questions remain regarding the extent to which these tests' highly structured nature fully captures the inherent complexities of daily life. The aim of this study was to assess the predictive and ecological validity of a novel multitasking measure in HIV infection. Method: Participants included 60 individuals with HIV infection (HIV+) and 25 demographically comparable seronegative adults (HIV?). Participants were administered a comprehensive neuropsychological battery, questionnaires assessing mood and everyday functioning, and a novel standardized test of multitasking, which involved balancing the demands of four interconnected performance-based functional tasks (i.e., financial management, cooking, medication management, and telephone communication). Results: HIV+ individuals demonstrated significantly worse overall performance, fewer simultaneous task attempts, and increased errors on the multitasking test as compared to the HIV? group. Within the HIV+ sample, multitasking impairments were modestly associated with deficits on standard neuropsychological measures of executive functions, episodic memory, attention/working memory, and information processing speed, providing preliminary evidence for convergent validity. More importantly, multivariate prediction models revealed that multitasking deficits were uniquely predictive of IADL dependence beyond the effects of depression and global neurocognitive impairment, with excellent sensitivity (86%), but modest specificity (57%). Conclusions: Taken together, these data indicate that multitasking ability may play an important role in successful everyday functioning in HIV+ individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
52.
Staub Adrian; Grant Margaret; Clifton Charles Jr.; Rayner Keith 《Canadian Metallurgical Quarterly》2011,37(5):1326
In this brief rejoinder, we respond to Farmer, Monaghan, Misyak, and Christiansen (2011). We argue that the data still do not support the claim that reading time is affected by the phonological typicality of a word for its part of speech. We also question Farmer et al.'s claim that interleaving syntactic structures in an experiment modifies grammatically based syntactic expectations. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
53.
Optimising the ventilation configuration of naturally ventilated livestock buildings for improved indoor environmental homogeneity 总被引:1,自引:0,他引:1
Due to the geometrical structure and ventilation configuration of naturally ventilated livestock buildings the animal occupied zone can experience large heterogeneities in ventilation efficiency. Ensuring a homogeneous indoor environment is important when designing naturally livestock buildings as producers should be confident that all animals are receiving the same environmental conditions, at least for the prevailing climate. Moreover, by including climate homogeneity in the building design process, the occurrence of high airspeeds in specific regions of a building can be reduced during windy outdoor conditions, thereby reducing the cold-stressing of animals in these regions. Therefore, it is desirable to know how to alter the geometrical features of a building in order to promote homogeneity in the indoor environment. In the present study, response surface methodology and computational fluid dynamics were used to develop predictive models that described the homogeneity of the indoor environment of a naturally ventilated livestock building as a function of its geometry and ventilation configuration. Three different eave opening conditions were chosen in order to improve the applicability of the developed response surfaces to practical situations encountered in Ireland. Results showed that for high to medium porosity eave opening conditions the environmental homogeneity was most sensitive to the building's roof pitch. However, when low porosity eave opening conditions were used the homogeneity was found to be highly sensitive to the sidewall height. Overall, this study found that modifying the building geometry has the greatest effect on environmental heterogeneity when the most restrictive eave opening condition was employed. It is also hoped that with the developed equations, a designer can subsequently select the best combination of design variables in order to achieve good uniformity in a naturally ventilated calf building. 相似文献
54.
This study is noteworthy as an application at project design scale of a methodology developed in 1976 by Jones & Jones for the Federal Highway Administation course ‘Esthetics and Visual Resource Management’ currently being given to highway professionals around the country. It also demonstrates the transfer of this methodology from highway facilities to urbanization. 相似文献
55.
Aurea M Almazan Desmond G Mortley Patricia J Grant 《Journal of the science of food and agriculture》1996,70(3):369-372
Sugar beet (Beta vulgaris L cv Great Western Sugar) was grown using the nutrient film technique with a half-strength modified Hoagland nutrient solution to determine its biomass yield and nutritional quality. After 6 months, storage root and foliage weights per plant were 493·1 g and 551·0 g, respectively. Sucrose content in the fresh storage root was 118·4 g kg−1 but was less than 10 g kg−1 in the fresh leaves and petioles. Some nutrients in the leaves and petioles were analysed to evaluate their potential as a leafy vegetable. Fresh leaf protein, total dietary fibre, mineral (Ca, Mg, Zn, Fe and K), vitamin (carotene, ascorbic acid and thiamine) and oxalic acid concentrations were similar to those of consumer-accepted green vegetables. 相似文献
56.
James L. Rand John K. Henderson Debora A. Grant 《Polymer Engineering and Science》1996,36(8):1058-1064
To predict the response of polyethylene thin films subjected to stress for a long time, it is necessary to understand the influence of stress on either the relaxation modulus or creep compliance. Extensive testing has been conducted on 20-micron-thick samples of a particular linear low-density polyethylene film at temperatures from 23°C to −50°C. When reduced to creep compliance and compared with results from dynamic mechanical analysis (DMA), the influence of nonlinearities in the response function is apparent. However, the use of a two-step loading procedure has produced sufficient data to discriminate between the effect of stress on amplitude and time on the creep compliance. It has been found that a master curve of compliance generated by DMA equipment may be used in conjunction with certain nonlinear functions to accurately predict the response of the polyethylene. Perhaps of more importance is the observation that the principles of simple time-temperature superposition, commonly used with linear viscoelastic characterization, are insufficient for use with polyethylene films at most stress levels of interest. 相似文献
57.
Grant Drenkow 《计算机测量与控制》2006,14(5)
2005年9月26日.由众多领先的测试和测量仪器供应商和用户组成的一个联盟发布了测试系统的一项新标准:LXI(LAN eXtensions for Inst rumentation).一年前建立的LXI联盟致力于增加系统速度、降低系统成本、减小系统尺寸、缩短系统设置时间,以及改进软件的通用性.它把Ethernet(IEEE 802.3)作为主要通信媒介;并借用计算机行业已获得的众多成果.利用现有Ethernet标准、Internet工具、LAN协议、IEC物理尺寸和IVI驱动程序的各方优点,从而使测试系统的互连平台了转向更高速的PC标准的IO,而不需要机箱和昂贵的电缆,并可使用标准的软件.联盟找到了能比计算机背板持续远久的体系结构.这一正在创建的体系结构建造在久经证明的工业标准上,使他们能够借用大量已成熟的技术,保证测试系统开发者拥有长期可行的解决方案. 相似文献
58.
Richard S. Parnas J. Grant Howard Thomas L. Luce Suresh G. Advani 《Polymer Composites》1995,16(6):429-445
A three-dimensionally woven fabric is proposed as a standard reference material for permeability characterization. The 3-D woven fabric requires care in cutting and handling, although it is more robust than 2-D woven or braided fabrics. If prepared carefully, the permeability of the 3-D woven fabric can be measured reproducibly within 15% in either radial flow or saturated 1-D flow geometries. The material was characterized for permeability in radial, unsaturated and saturated 1-D, and through-thickness flow geometries. The transient results demonstrated the importance of structural heterogeneity on the unsaturated flow behavior, and agree qualitatively with a simplistic model of flow in heterogeneous unsaturated porous media. The effects of heterogeneity were manifested in the proposed SRM by an increasing trend in the “unsaturated permeability.” Experiments were also conducted with a random mat that displayed transient flows dominated by wicking. The effects of wicking on the macroscopic flow behavior were manifested by transients in the “unsaturated permeability” in which a decreasing trend was observed. 相似文献
59.
The Wairakei geothermal field was the proving ground for the use of electrical resistivity methods for geothermal exploration. At this site it was first demonstrated that a large contrast in resistivity existed between geothermal ground and the cold surroundings. Within the top 500 m of the geothermal field, low-resistivity (5–10 Ωm) reflects the effects of both the hot saline water in the pore spaces and the conductive rock-matrix. The first surveys at Wairakei used a Wenner array (a ∼550 m) to measure the resistivity values along tracks throughout the field; contour maps of the resistivities were used to estimate the lateral extent of the geothermal waters at a few hundred metres depth. In the late 1960s the Wenner array was superseded by the Schlumberger array (AB/2 = 500 m and 1000 m), which enabled deeper penetration and better definition of the extent of the geothermal waters. These early surveys showed that the bounds of the geothermal waters were often sharp, leading to the concept that a ‘resistivity boundary’ could be defined for New Zealand's liquid-dominated geothermal fields. As new methods of measuring electrical structure with greater precision became available, Wairakei was often chosen as the testing ground. 相似文献
60.
As outlined in compression therapy literature, the performance of a compression textile can be characterized by its stiffness and interface pressure. In this study, an indirect approach for measuring pressure from a set of compression bandages and hosiery was developed, from which rigidity (EI) values were determined, and tension–elongation curves and pressure-elongation data were calculated. The calculated pressure values were compared against PicoPress sensor readings measured on 10 participants. Results showed that the correlation between both approaches varied among bandage and hosiery samples. 相似文献