全文获取类型
收费全文 | 1134篇 |
免费 | 72篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 21篇 |
化学工业 | 315篇 |
金属工艺 | 14篇 |
机械仪表 | 34篇 |
建筑科学 | 26篇 |
矿业工程 | 2篇 |
能源动力 | 34篇 |
轻工业 | 306篇 |
水利工程 | 8篇 |
石油天然气 | 8篇 |
无线电 | 93篇 |
一般工业技术 | 133篇 |
冶金工业 | 91篇 |
原子能技术 | 4篇 |
自动化技术 | 118篇 |
出版年
2024年 | 9篇 |
2023年 | 16篇 |
2022年 | 42篇 |
2021年 | 72篇 |
2020年 | 52篇 |
2019年 | 56篇 |
2018年 | 43篇 |
2017年 | 57篇 |
2016年 | 55篇 |
2015年 | 36篇 |
2014年 | 55篇 |
2013年 | 86篇 |
2012年 | 64篇 |
2011年 | 87篇 |
2010年 | 62篇 |
2009年 | 55篇 |
2008年 | 54篇 |
2007年 | 35篇 |
2006年 | 31篇 |
2005年 | 33篇 |
2004年 | 28篇 |
2003年 | 20篇 |
2002年 | 15篇 |
2001年 | 17篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 26篇 |
1997年 | 20篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1975年 | 1篇 |
排序方式: 共有1207条查询结果,搜索用时 156 毫秒
151.
A.J. Heinrichs B.S. Heinrichs C.M. Jones P.S. Erickson K.F. Kalscheur T.D. Nennich B.J. Heins F.C. Cardoso 《Journal of dairy science》2017,100(10):8451-8454
The estimation of Holstein heifer body weight (BW) from heart girth measurements is needed, as many farms do not have animal scales to make the management decisions that require BW. The correlation between heart girth and BW is known to vary with differing animal conformation. The previous equation to correlate the 2 measures for Holstein dairy heifers was done 25 yr ago. Data were derived from 6 US experiment stations that are part of Regional Research Project NC-2042: Management Systems to Improve the Economic and Environmental Sustainability of Dairy Enterprises. After deriving a new equation from a data set of observations and using a second validation data set, it was determined that the equation developed in 1992 was still valid and further equation development was not needed at this time. 相似文献
152.
153.
A.K. de Freitas J.F.P. Lobato L.L. Cardoso J.U. Tarouco R.M. Vieira D.R. Dillenburg I. Castro 《Meat science》2014
Chemical and mineral composition and the intramuscular fatty acid (IMF) profile of the Longissimus dorsi muscle (LM) of 60 purebred Hereford, 1/4 Braford and 3/8 Braford steers finished either in a feedlot or on improved pastures of the Pampa biome were evaluated. Pastures were improved with the introduction of Lolium multiflorum, Trifolium repens, and Lotus corniculatus. On average, beef from pasture-fed steers presented higher concentrations of the fatty acids C18:3n − 3 (P < 0.001), C20:3n − 3 (P = 0.035), total n − 3 (P < 0.001) and lower n − 6/n − 3 ratio (P < 0.001) in the IMF, and higher Mg and lower K content in muscle relative to those finished in the feedlot. C12:0 concentration in IMF was higher (P = 0.027) for 3/8 Braford than the purebred Hereford steers, whereas purebred Herefords presented lower C14:1 (P = 0.003) and higher C18:0 (P = 0.022) concentrations than the two Braford groups. The meat composition of purebred Hereford and Braford steers was not substantially different; however, beef produced exclusively on improved pastures presented higher concentration of components that are considered beneficial to human health, such as n − 3 fatty acids, and a lower n − 6/n − 3 ratio. 相似文献
154.
Rafael Balbino Cardoso Luiz Augusto Horta Nogueira Edson Palhares de Souza Jamil Haddad 《Energy Efficiency》2012,5(3):433-446
Increasing efficiency of electrical equipment is essential to national energy rationality, enabling energy consumption reduction and postponing inversion in distribution, transmission and generation, as well as mitigating environmental impacts associated with such activities. Considering such purposes, two actions have been promoted in Brazil: (a) minimum energy performance standards (MEPS) have been required for some appliances and (b) consumers have been informed about the most efficient products by ??endorsement labeling.?? The purpose of this study is to assess window and split air-conditioners with Brazilian MEPS. To evaluate the impact of efficient air-conditioners in this market, a model was developed based on estimates for quantity of equipment in operation and unitary consumption, as determined by local temperature records. From this model, it was deduced that using only efficient conditioners (class A for Brazilian Labeling Program/INMETRO, with PROCEL Label) an annual saving of 322?GWh and a reduction in demand of 109?MW could be obtained in 2007. Furthermore, it was observed that the current MEPS established by Brazilian legislation for air-conditioners may be considered relatively low. Considering that MEPS are similar to those observed in China (the main exporter of air-conditioners to the Brazil), an energy saving of roughly 222?GWh could be achieved in the same year. Impacts on emission of greenhouse gases are also estimated. 相似文献
155.
Clarissa S. Cardoso MarinaA.G. von Keyserlingk Maria José Hötzel 《Journal of dairy science》2019,102(2):1811-1821
The aim of this qualitative study was to explore the shared and divergent views among Brazilian dairy farmers, agricultural advisors, and lay citizens on what characteristics they viewed were most important on an ideal dairy farm. Responses from 107 dairy farmers, 170 agricultural advisors (including veterinarians), and 280 lay citizens were subjected to thematic analyses. Five themes were identified: milk quality, animal welfare, economics, society, and the environment. Although all 3 groups made reference to each of the 5 themes, they emphasized different characteristics. The lay citizens placed the most emphasis on milk quality. In contrast, both the farmers and the advisors highlighted economics as the most important characteristic of an ideal dairy farm. When considering only animal welfare, we noted differences in the use of the constructs of animal welfare: farmers and advisors referred mostly to aspects related to biological functioning, whereas lay citizens emphasized affective states and naturalness. All 3 stakeholder groups referred to the use of pasture as being an important component of an ideal dairy farm but again differed in their reasons; citizens referred to pasture in the context of naturalness, whereas the other 2 stakeholder groups almost always referred to pasture using economic terms. Technology was highlighted by all 3 groups as an important characteristic of an ideal dairy farm but differences were noted in their justification for this view. For example, lay citizens viewed technology as a tool to improve milk quality, whereas farmers and advisors both referred to technology as an important vehicle to improve quality of life for those working in the industry. Lay citizens raised several concerns associated with the overuse of antibiotics and other chemicals, but farmers and advisors rarely mentioned these types of concerns. The latter 2 stakeholders placed considerable emphasis on the quality of life of dairy farmers and workers, an issue rarely discussed by lay citizens. Overall, our findings highlight several disconnects between the expectations of the lay citizens, and farmers and their advisors. We suggest that dairy farmers and agricultural advisors should both reflect on the desires of the lay public in what they view to be an ideal dairy farm, as this may help bridge some of the current disconnects. 相似文献
156.
Maria Eliza de Castro Moreira Rosemary Gualberto Fonseca Alvarenga Pereira Danielle Ferreira Dias Vanessa Silva Gontijo Fabiana Cardoso Vilela Gabriel de Oliveira Isac de Moraes Alexandre Giusti-Paiva Marcelo Henrique dos Santos 《Journal of Functional Foods》2013,5(1):466-474
Green coffee contains a large quantity and variety of polyphenols and flavonoids. The roasting affects the composition of the polyphenols in coffee, due to the formation of compounds generated by Maillard reaction, which can have anti-inflammatory or antioxidant potential. The anti-inflammatory and antioxidant effects of aqueous extracts of green (AGCa) and roasted (ARCa) coffee beans were investigated in animal models and using a DPPH radical scavenging test. In the formalin test the extracts reduced licking activity only in the late phase. The inhibitory values of oedema at 3 h post-carrageenan were 53% and 74% for 100 and 300 mg/kg of the AGCa extract and 36% for ARCa (300 mg/kg). Leukocyte recruitment into the peritoneal cavity was inhibited by the extracts. The antioxidant activities of the extracts were higher than the reference antioxidants, ascorbic acid and butylated hydroxytoluene. These results indicate that coffee extracts exhibit anti-inflammatory and antioxidant properties. 相似文献
157.
Production of xanthan gum was studied and modelled using unstructured kinetic models composed of three differential equations, which considered the microbial biomass, carbon source, and xanthan concentration. The fermentation process, using Xanthomonas campestris pv. campestris NRRL B-1459, was conducted under controlled conditions with diluted sugar cane broth at different initial sucrose concentrations (15.0, 25.0, and 35.0 g L−1). Unstructured kinetic models proposed in the literature for this system were reviewed and applied. These models were tested against the experimental results, calculating the parameters by nonlinear regression. The kinetic models used in this study provided estimations of microbial growth, substrate consumption, and product formation, and, therefore, these parameters were quantified in the fermentation experiments. Higher yield of xanthan per amount of sucrose (0.58 g g−1) and productivity (0.63 g L−1 h−1) were obtained using initial sucrose concentrations of 25.0 and 35.0 g L−1, respectively. The models were used to predict the kinetic parameters for a medium containing an intermediate and a larger initial sucrose concentration (27.0 and 40.0 g L−1). When tested experimentally, the measured fermentation parameters were in close agreement with the values predicted by the model that presented the best adjustment, demonstrating its validity. 相似文献
158.
Physical properties and effective thermal diffusivity of soybean grains as a function of moisture content and broken kernels 下载免费PDF全文
159.
Optimization of cashew gum and chitosan for microencapsulation of pequi oil by complex coacervation 下载免费PDF全文
160.