全文获取类型
收费全文 | 1374篇 |
免费 | 66篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 18篇 |
综合类 | 3篇 |
化学工业 | 390篇 |
金属工艺 | 13篇 |
机械仪表 | 20篇 |
建筑科学 | 80篇 |
矿业工程 | 2篇 |
能源动力 | 47篇 |
轻工业 | 241篇 |
水利工程 | 7篇 |
石油天然气 | 3篇 |
无线电 | 103篇 |
一般工业技术 | 218篇 |
冶金工业 | 152篇 |
原子能技术 | 5篇 |
自动化技术 | 140篇 |
出版年
2023年 | 13篇 |
2022年 | 27篇 |
2021年 | 44篇 |
2020年 | 18篇 |
2019年 | 43篇 |
2018年 | 41篇 |
2017年 | 39篇 |
2016年 | 26篇 |
2015年 | 37篇 |
2014年 | 50篇 |
2013年 | 85篇 |
2012年 | 74篇 |
2011年 | 100篇 |
2010年 | 76篇 |
2009年 | 80篇 |
2008年 | 84篇 |
2007年 | 76篇 |
2006年 | 48篇 |
2005年 | 51篇 |
2004年 | 45篇 |
2003年 | 29篇 |
2002年 | 45篇 |
2001年 | 27篇 |
2000年 | 26篇 |
1999年 | 20篇 |
1998年 | 39篇 |
1997年 | 21篇 |
1996年 | 12篇 |
1995年 | 24篇 |
1994年 | 12篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1971年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有1442条查询结果,搜索用时 31 毫秒
151.
Spencer L. Tomarken Daniel M. Silevitch Gabriel Aeppli Braden A.W. Brinkman Jian Xu Karin A. Dahmen Thomas F. Rosenbaum 《Advanced functional materials》2014,24(20):2986-2992
Random magnetic fields, varying from site to site in a magnetic material, are a form of disorder that can determine the local architecture and stability of the magnetic state. In a ferromagnet, the application of an external magnetic field can amplify the effects of the internal random fields and, in principle, harden a magnetic domain, without changing temperature and only for as long as the external field is present. Here, the rare‐earth compound Nd2Fe14B, formed with a granular morphology of random‐packed, elongated grains, is an experimental realization of the Random Field Ising Model in a room temperature ferromagnet. The application of magnetic fields transverse to the easy axis tunes the coupling between the structural disorder and the magnetic pinning properties. This material both illuminates the intricacies of tunable disorder and serves as a guidepost along the way to developing increased‐density magnetic storage media. 相似文献
152.
Effects of dietary supplementation of vitamins D(3) and E on quality characteristics of pigs and longissimus muscle antioxidative capacity 总被引:1,自引:0,他引:1
Lahucky R Bahelka I Kuechenmeister U Vasickova K Nuernberg K Ender K Nuernberg G 《Meat science》2007,77(2):264-268
The effects of addition of vitamin D3 and vitamin E to pig diets on blood plasma calcium concentration, meat quality (longissimus muscle) and antioxidative capacity were investigated. Two treatments consisted of supplementation with vitamin D3 (500,000 IU/d) for 5 days separately (group D) and a combination of vitamin E (500 mg α-tocopheryl acetate/kg diet) for 30 days and vitamin D3 (500,000 IU/d) for 5 days (group D + E) to growing-finishing pigs before slaughter. Pigs fed with vitamin D3 had higher (P < 0.01) plasma calcium concentration compared with control pigs. Dietary supplementation of vitamin E significantly (P < 0.05) increased the concentration of α-tocopherol in meat (longissimus muscle). Vitamin D3 supplementation resulted in higher (P = 0.07) a∗ values of loin chops at 5 days of storage. Vitamin D3 and vitamin E supplementation did not affect other meat quality characteristics or tenderness (quantified by Warner–Bratzler shear force). Antioxidative capacity (measured as MDA production after incubation of longissimus muscle homogenates with Fe2+/ascorbate) was improved by vitamin E and partly by vitamin D3 supplementation. 相似文献
153.
Predictions from a cognitive schema model of anxiety were tested by comparing generally anxious patients and normal controls on their incidental recall of positive and negative, threatening and nonthreatening, self- and other-referenced words. There was no evidence of a self-referent recall bias favoring negative or threatening words in anxiety. Contrary to expectation, the results indicated relatively poorer memory for threatening material in anxious patients. We argue that the cognitive schema model could not adequately account for these and other recent research findings and suggest an alternative formulation of information-processing biases in anxiety. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
154.
Two studies investigated the effects of conditioning to masked stimuli on visuospatial attention. During the conditioning phase, masked snakes and spiders were paired with a burst of white noise, or paired with an innocuous tone, in the conditioned stimulus (CS)+ and CS- conditions, respectively. Attentional allocation to the CSs was then assessed with a visual probe task, in which the CSs were presented unmasked (Experiment 1) or both unmasked and masked (Experiment 2), together with fear-irrelevant control stimuli (flowers and mushrooms). In Experiment 1, participants preferentially allocated attention to CS+ relative to control stimuli. Experiment 2 suggested that this attentional bias depended on the perceived aversiveness of the unconditioned stimulus and did not require conscious recognition of the CSs during both acquisition and expression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
155.
Several species of the genus Haemophilus are well known etiological agents of pneumonia, meningitis, conjunctivitis, epiglottitis and chancroid. However, identification and speciation of Haemophilus is both time consuming and labor intensive. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF-MS) has been used by several investigators to profile proteins from intact and disrupted bacteria; consequently, MALDI/TOF-MS has emerged as a powerful tool in diagnostic bacteriology. This paper reports the use of MALDI/TOF-MS as a technique for the rapid identification and speciation of Haemophilus. This technique was used to not only identify the pathogen, H. ducreyi, but also to determine strain differences from different isolates. Mass spectral 'fingerprints' were obtained which permitted the rapid speciation of not only pathogenic forms of Haemophilus, but also those bacteria which are normally regarded as non-pathogenic and members of the normal flora. MALDI/TOF mass spectra can be acquired in 10 min, allowing the identification of Haemophilus spp. within 24 h rather than the 48 h or more needed for traditional bacteriological methods. In addition, these are the first mass spectral fingerprints available in the literature for many of these organisms. 相似文献
156.
Differential activation of ERK and JNK mitogen-activated protein kinases by Raf-1 and MEKK 总被引:8,自引:0,他引:8
A Minden A Lin M McMahon C Lange-Carter B Dérijard RJ Davis GL Johnson M Karin 《Canadian Metallurgical Quarterly》1994,266(5191):1719-1723
Growth factors activate mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases (ERKs) and Jun kinases (JNKs). Although the signaling cascade from growth factor receptors to ERKs is relatively well understood, the pathway leading to JNK activation is more obscure. Activation of JNK by epidermal growth factor (EGF) or nerve growth factor (NGF) was dependent on H-Ras activation, whereas JNK activation by tumor necrosis factor alpha (TNF-alpha) was Ras-independent. Ras activates two protein kinases, Raf-1 and MEK (MAPK, or ERK, kinase) kinase (MEKK). Raf-1 contributes directly to ERK activation but not to JNK activation, whereas MEKK participated in JNK activation but caused ERK activation only after overexpression. These results demonstrate the existence of two distinct Ras-dependent MAPK cascades--one initiated by Raf-1 leading to ERK activation, and the other initiated by MEKK leading to JNK activation. 相似文献
157.
Several applications for renewable energy conversion make use of variable speed generators. A conversion from variable frequency to grid frequency is therefore essential. One part of the converter is a rectifier. A rectifier model is presented, which is integrated in a time stepping finite element simulation environment where the generator and circuit equations are solved simultaneously. The model handles bidirectional alternator speeds as the application is a linear generator for ocean wave energy conversion. The rectifier model is extended with a load model, consisting of R, L and E, and simulations show what impact the rectifier has on the generator’s behaviour. 相似文献
158.
This study investigated the effects of high temperature and combustion conditions on the attrition of fluidized material in
a fluidized bed. Silica sand was fluidized in air at an atmospheric pressure between 873 K and 1,073 K. The operating parameters
evaluated in investigating the attrition rate of fluidized material included particle size, temperature and both combustion
and non-combustion conditions. Experimental results indicated that the total weight of attrition increased with increasing
temperature and decreased with increasing particle size. The attrition was higher during the initial fluidization period than
the later period, due to the loss of sharp corners and edges of the attrition particles. The initial and final attrition rates
during combustion were higher than those in the non-combustion condition, because the heat and thermal shock were produced
to increase attrition rate during incineration. Comparing the experimental data with previous correlations, that reveals a
significant level of error in the prediction results from existing correlations. This error may occur because the experimental
equations neglected the operating temperature and particle size. 相似文献
159.
160.
Karin Ansttz 《International Journal of Communication Systems》1993,6(3):161-165
The introduction of ATM and broadband-based equipment into the European market requires considerable capital investment. It will result in a structural technological change, affecting the competitiveness of the European economy. Successful introduction depends on how both ATM network equipment and broadband based end-user equipment are brought onto the market. This paper focuses on economic benefits and anticipating marketing strategies, applicable in Europe with its specific, historically evolved structures. The price to pay for this ‘in-sight information’ is leaving out a global comparison. Refraining from evaluation whether conditions are good or bad for Europe or other areas, the article explains what conditions can be found there recently and where are the chances and challenges right now. 相似文献