全文获取类型
收费全文 | 92396篇 |
免费 | 15940篇 |
国内免费 | 205篇 |
专业分类
电工技术 | 1586篇 |
综合类 | 94篇 |
化学工业 | 27365篇 |
金属工艺 | 2461篇 |
机械仪表 | 3935篇 |
建筑科学 | 2862篇 |
矿业工程 | 54篇 |
能源动力 | 3105篇 |
轻工业 | 10781篇 |
水利工程 | 536篇 |
石油天然气 | 255篇 |
武器工业 | 1篇 |
无线电 | 15777篇 |
一般工业技术 | 21521篇 |
冶金工业 | 6446篇 |
原子能技术 | 691篇 |
自动化技术 | 11071篇 |
出版年
2023年 | 569篇 |
2022年 | 899篇 |
2021年 | 1669篇 |
2020年 | 2313篇 |
2019年 | 3898篇 |
2018年 | 4200篇 |
2017年 | 4455篇 |
2016年 | 5183篇 |
2015年 | 4868篇 |
2014年 | 5614篇 |
2013年 | 8130篇 |
2012年 | 5808篇 |
2011年 | 6252篇 |
2010年 | 5485篇 |
2009年 | 5582篇 |
2008年 | 4901篇 |
2007年 | 4296篇 |
2006年 | 3828篇 |
2005年 | 3243篇 |
2004年 | 3124篇 |
2003年 | 2936篇 |
2002年 | 2834篇 |
2001年 | 2341篇 |
2000年 | 2229篇 |
1999年 | 1639篇 |
1998年 | 2279篇 |
1997年 | 1488篇 |
1996年 | 1237篇 |
1995年 | 993篇 |
1994年 | 750篇 |
1993年 | 703篇 |
1992年 | 512篇 |
1991年 | 508篇 |
1990年 | 431篇 |
1989年 | 419篇 |
1988年 | 328篇 |
1987年 | 287篇 |
1986年 | 264篇 |
1985年 | 236篇 |
1984年 | 202篇 |
1983年 | 153篇 |
1982年 | 152篇 |
1981年 | 132篇 |
1980年 | 130篇 |
1979年 | 102篇 |
1978年 | 95篇 |
1977年 | 126篇 |
1976年 | 161篇 |
1975年 | 81篇 |
1974年 | 75篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Fundamental Evaluation of Power Supply and Rectifiers for Wireless Power Transfer Using Magnetic Resonant Coupling 下载免费PDF全文
This paper provides a fundamental analysis of a power supply and rectifiers for wireless power transfer using magnetic resonant coupling (MRC). MRC enables efficient wireless power transfer over middle‐range transfer distances. MRC for wireless power transfer should operate at a high frequency in the industry science medical band, such as 13.56 MHz, because the size of the transfer device decreases at higher transfer frequencies. Therefore, the output frequency of the power supply on the transmitting side should be 13.56 MHz. In addition, the rectifier on the receiving side is operated at a high frequency. This paper focuses on the reflected power in the power supply and rectifiers. Thus, the parametric design method is clarified for the power supply, including a low‐pass filter to match the output, the impedance of the power supply with the characteristic impedance of the transmission line. In addition, the effects on the rectifiers of silicon carbide and gallium nitride diodes are confirmed by performing an experiment and a loss analysis. 相似文献
42.
Nazir Kizzie‐Hayford Doris Jaros Yvonne Schneider Harald Rohm 《International Journal of Food Science & Technology》2015,50(2):381-388
A standard method for the extraction of tiger nut milk has been introduced. It has been shown that, although milling duration improves the yield of tiger nut milk solids and its nutrient composition, there is a quantifiable loss of nutrient in the pressing residue during milk extraction. Milling duration improved the colloidal stability of the milk against creaming during 16 h of storage. A higher milling intensity resulted in the aggregation of biological polymers which resulted in colloidal destabilisation. Milling improved the lightness and stability and reduced browning rate of the tiger nut milk during storage. This report is important for the production of tiger nut milk of consistent and comparable characteristics. Milling has been introduced as a processing method for the qualitative and quantitative modulation of the properties of tiger nut milk. It is recommended to develop further strategies to improve the colloidal stability of tiger nut milk as a beverage. 相似文献
43.
44.
45.
46.
Muntasir Hashim Farnoosh Farhad David Smyth‐Boyle Robert Akid Xiang Zhang Philip J. Withers 《工业材料与腐蚀》2019,70(11):2009-2019
The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits. 相似文献
47.
Phytoalexins are inducible secondary metabolites possessing antimicrobial activity against phytopathogens. Rice produces a wide array of phytoalexins in response to pathogen attacks and environmental stresses. With few exceptions, most phytoalexins identified in rice are diterpenoid compounds. Until very recently, flavonoid sakuranetin was the only known phenolic phytoalexin in rice. However, recent studies have shown that phenylamides are involved in defense against pathogen attacks in rice. Phenylamides are amine-conjugated phenolic acids that are induced by pathogen infections and abiotic stresses including ultra violet (UV) radiation in rice. Stress-induced phenylamides, such as N-trans-cinnamoyltryptamine, N-p-coumaroylserotonin and N-cinnamoyltyramine, have been reported to possess antimicrobial activities against rice bacterial and fungal pathogens, an indication of their direct inhibitory roles against invading pathogens. This finding suggests that phenylamides act as phytoalexins in rice and belong to phenolic phytoalexins along with sakuranetin. Phenylamides also have been implicated in cell wall reinforcement for disease resistance and allelopathy of rice. Synthesis of phenolic phytoalexins is stimulated by phytopathogen attacks and abiotic challenges including UV radiation. Accumulating evidence has demonstrated that biosynthetic pathways including the shikimate, phenylpropanoid and arylmonoamine pathways are coordinately activated for phenolic phytoalexin synthesis, and related genes are induced by biotic and abiotic stresses in rice. 相似文献
48.
In vivo Kinetic Biodistribution of Nano‐Sized Outer Membrane Vesicles Derived from Bacteria 下载免费PDF全文
Su Chul Jang Sae Rom Kim Yae Jin Yoon Kyong‐Su Park Ji Hyun Kim Jaewook Lee Oh Youn Kim Eun‐Jeong Choi Dae‐Kyum Kim Dong‐Sic Choi Yoon‐Keun Kim Jaesung Park Dolores Di Vizio Yong Song Gho 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(4):456-461
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo. 相似文献
49.
Yao‐Min Hung Neng‐Chyan Huang Jyh‐Seng Wang Shue‐Ren Wann 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(2):344-346
Cases of isolated hepatic tuberculosis (TB) are rare. The diagnosis is often delayed or missed because of nonspecific symptoms and laboratory findings. Besides, the disease is extremely rare even in a country where TB is an alarming public health problem. This report demonstrates the difficulty in correctly diagnosing local hepatic TB. We report the case of a 62‐year‐old male patient with end‐stage renal disease treated with hemodialysis, who developed 2 months of abdominal distension and general anorexia, with hyperechoic hepatic lesions on ultrasound. Computed tomography suspected multiple liver tumors. The liver biopsy finally led to the diagnosis of TB of the liver without other involvements. We conclude that isolated hepatic TB is one of the rare forms of extrapulmonary TB in dialysis patients. A greater awareness of this rare clinical entity may prevent needless surgical interventions. 相似文献
50.