全文获取类型
收费全文 | 1503篇 |
免费 | 77篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 19篇 |
综合类 | 2篇 |
化学工业 | 286篇 |
金属工艺 | 22篇 |
机械仪表 | 28篇 |
建筑科学 | 82篇 |
矿业工程 | 1篇 |
能源动力 | 45篇 |
轻工业 | 119篇 |
水利工程 | 15篇 |
石油天然气 | 2篇 |
无线电 | 80篇 |
一般工业技术 | 424篇 |
冶金工业 | 191篇 |
原子能技术 | 12篇 |
自动化技术 | 255篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 24篇 |
2021年 | 41篇 |
2020年 | 20篇 |
2019年 | 27篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 38篇 |
2015年 | 44篇 |
2014年 | 71篇 |
2013年 | 90篇 |
2012年 | 98篇 |
2011年 | 138篇 |
2010年 | 89篇 |
2009年 | 81篇 |
2008年 | 102篇 |
2007年 | 115篇 |
2006年 | 87篇 |
2005年 | 88篇 |
2004年 | 55篇 |
2003年 | 48篇 |
2002年 | 40篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 10篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1583条查询结果,搜索用时 15 毫秒
991.
992.
Jeremy T. Howard Jennie E. Pryce Christine Baes Christian Maltecca 《Journal of dairy science》2017,100(8):6009-6024
Traditionally, pedigree-based relationship coefficients have been used to manage the inbreeding and degree of inbreeding depression that exists within a population. The widespread incorporation of genomic information in dairy cattle genetic evaluations allows for the opportunity to develop and implement methods to manage populations at the genomic level. As a result, the realized proportion of the genome that 2 individuals share can be more accurately estimated instead of using pedigree information to estimate the expected proportion of shared alleles. Furthermore, genomic information allows genome-wide relationship or inbreeding estimates to be augmented to characterize relationships for specific regions of the genome. Region-specific stretches can be used to more effectively manage areas of low genetic diversity or areas that, when homozygous, result in reduced performance across economically important traits. The use of region-specific metrics should allow breeders to more precisely manage the trade-off between the genetic value of the progeny and undesirable side effects associated with inbreeding. Methods tailored toward more effectively identifying regions affected by inbreeding and their associated use to manage the genome at the herd level, however, still need to be developed. We have reviewed topics related to inbreeding, measures of relatedness, genetic diversity and methods to manage populations at the genomic level, and we discuss future challenges related to managing populations through implementing genomic methods at the herd and population levels. 相似文献
993.
Jesse Fox Sun Joo Ahn Joris H. Janssen Leo Yeykelis Kathryn Y. Segovia Jeremy N. Bailenson 《Human-Computer Interaction》2013,28(5):401-432
Existing research has investigated whether virtual representations perceived to be controlled by humans (i.e., avatars) or those perceived to be controlled by computer algorithms (i.e., agents) are more influential. A meta-analysis (N = 32) examined the model of social influence in virtual environments (Blascovich, 2002) and investigated whether agents and avatars in virtual environments elicit different levels of social influence. Results indicated that perceived avatars produced stronger responses than perceived agents. Level of immersion (desktop vs. fully immersive), dependent variable type (subjective vs. objective), task type (competitive vs. cooperative vs. neutral), and actual control of the representation (human vs. computer) were examined as moderators. An interaction effect revealed that studies conducted on a desktop that used objective measures showed a stronger effect for agency than those that were conducted on a desktop but used subjective measures. Competitive and cooperative tasks showed greater agency effects than neutral tasks. Studies in which both conditions were actually human controlled showed greater agency effects than studies in which both conditions were actually computer controlled. We discuss theoretical and design implications for human–computer interaction and computer-mediated communication. 相似文献
994.
995.
Wang Yunxia Wang Shuangshuang Zhang Shunping Scherman Oren A. Baumberg Jeremy J. Ding Tao Xu Hongxing 《Nano Research》2018,11(12):6384-6390
Nano Research - Plasmon-induced polymerization can facilitate the site-selectivity and orientation of polymer growth, which enriches the toolbox of polymerization and nanofabrication. Here, we... 相似文献
996.
This study examined the control of standing balance while wearing construction stilts. Motion capture data were collected from nine expert stilt users and nine novices. Three standing conditions were analysed: ground, 60 cm stilts and an elevated platform. Each task was also performed with the head extended as a vestibular perturbation. Both expert and novice groups exhibited lower displacement of the whole body centre of mass and centre of pressure on construction stilts. Differences between the groups were only noted in the elevated condition with no stilts, where the expert group had lower levels of medial–lateral displacement of the centre of pressure. The postural manipulation revealed that the expert group had superior balance to the novice group. Conditions where stilts were worn showed lower levels of correspondence to the inverted pendulum model. Under normal conditions, both expert and novice groups were able to control their balance while wearing construction stilts. 相似文献
997.
Matthew I. Knight Angus M. Tester Matthew B. McDonagh Andrew Brown Jeremy Cottrell Jianghui Wang Peter Hobman Benjamin G. Cocks 《Journal of dairy science》2014
Ribonuclease 5, also known as angiogenin, is a stable and abundant ribonuclease in milk whey protein, which is able to regulate several cellular functions, including capillary formation, neuron survival, and epithelial cell growth. Ribonuclease 5 is important for protein synthesis directly stimulating rRNA synthesis in the nucleolus. Here, we show that biologically active RNase5 can be purified from bovine milk. Furthermore, we show that milk-derived RNase5 directly stimulates muscle cell differentiation in vitro, inducing C2C12 cell differentiation and myogenesis. When supplemented into the diet of healthy adult mice, milk-derived RNase5 preparations promoted muscle weight gain and grip strength. Collectively, these data indicate that milk-derived RNase5 preparations exhibit a novel role in skeletal muscle cell function. 相似文献
998.
André D. Taylor Edward Y. KimVirgil P. Humes Jeremy KizukaLevi T. Thompson 《Journal of power sources》2007
We present a method of using inkjet printing (IJP) to deposit catalyst materials onto gas diffusion layers (GDLs) that are made into membrane electrode assemblies (MEAs) for polymer electrolyte fuel cell (PEMFC). Existing ink deposition methods such as spray painting or screen printing are not well suited for ultra low (<0.5 mg Pt cm−2) loadings. The IJP method can be used to deposit smaller volumes of water based catalyst ink solutions with picoliter precision provided the solution properties are compatible with the cartridge design. By optimizing the dispersion of the ink solution we have shown that this technique can be successfully used with catalysts supported on different carbon black (i.e. XC-72R, Monarch 700, Black Pearls 2000, etc.). Our ink jet printed MEAs with catalyst loadings of 0.020 mg Pt cm−2 have shown Pt utilizations in excess of 16,000 mW mg−1 Pt which is higher than our traditional screen printed MEAs (800 mW mg−1 Pt). As a further demonstration of IJP versatility, we present results of a graded distribution of Pt/C catalyst structure using standard Johnson Matthey (JM) catalyst. Compared to a continuous catalyst layer of JM Pt/C (20% Pt), the graded catalyst structure showed enhanced performance. 相似文献
999.
Continuous fermentative hydrogen production using a two-phase reactor system with recycle 总被引:5,自引:0,他引:5
The effects of effluent recycle were examined in a two-phase anaerobic system where the first phase was operated for fermentative hydrogen production and the second for methanogenesis. The hydrogen reactor was operated as a chemostat at 35 degrees C and pH 5.5 with a 10 h hydraulic retention time, and the methane reactor was operated as an up-flow reactor at 28 degrees C and pH between 6.9 and 7.2. Two recycle ratios were examined: 0 and 0.98. Effluent recycle reduced the required alkalinity for pH control by approximately 40%. The H2 productivity metric, with a basis in electrons and incorporating both gaseous and dissolved H2, was developed as a more fundamental reporting method than the molar H2 yield. Without recycle, the H2 productivity was 0.115 g of H2 COD/g of feed COD, but decreased to 0.015 q of H2 COD/g of feed COD with recycle (COD = chemical oxygen demand). Mass balances indicated the lower H2 productivity during recycle was due to electrons being partitioned to methane and less-oxidized soluble constituents such as propionic acid, ethanol, and butanol. The results indicated that achieving high H2 productivity with nonsterile wastewaters will be challenging and membrane filtration of the recycle liquid may be required to exclude the return of hydrogen-consuming organisms. 相似文献
1000.
Turner EC Hughes J Wilson H Clay M Mylonas KJ Kipari T Duncan WC Fraser HM 《Reproduction (Cambridge, England)》2011,141(6):821-831
Macrophages are the most abundant immune cell within the ovary. Their dynamic distribution throughout the ovarian cycle and heterogenic array of functions suggest the involvement in various ovarian processes, but their functional role has yet to be fully established. The aim was to induce conditional macrophage ablation to elucidate the putative role of macrophages in maintaining the integrity of ovarian vasculature. Using the CD11b-diphtheria toxin receptor (DTR) mouse, in which expression of human DTR is under the control of the macrophage-specific promoter sequence CD11b, ovarian macrophages were specifically ablated in adult females by injections of diphtheria toxin (DT). CD11b-DTR mice were given DT treatment or vehicle and ovaries collected at 2, 8, 16, 24 and 48 h. Histochemical stains were employed to characterise morphological changes, immunohistochemistry for F4/80 to identify macrophages and the endothelial cell marker CD31 used to quantify vascular changes. In normal ovaries, macrophages were detected in corpora lutea and in the theca layer of healthy and atretic follicles. As macrophage ablation progressed, increasing amounts of ovarian haemorrhage were observed affecting both luteal and thecal tissue associated with significant endothelial cell depletion, increased erythrocyte accumulation and increased follicular atresia by 16 h. These events were followed by necrosis and profound structural damage. Changes were limited to the ovary, as DT treatment does not disrupt the vasculature of other tissues likely reflecting the unique cyclical nature of the ovarian vasculature and heterogeneity between macrophages within different tissues. These results show that macrophages play a critical role in maintaining ovarian vascular integrity. 相似文献