全文获取类型
收费全文 | 3464篇 |
免费 | 81篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 186篇 |
综合类 | 7篇 |
化学工业 | 666篇 |
金属工艺 | 53篇 |
机械仪表 | 94篇 |
建筑科学 | 63篇 |
矿业工程 | 5篇 |
能源动力 | 121篇 |
轻工业 | 271篇 |
水利工程 | 7篇 |
石油天然气 | 8篇 |
无线电 | 436篇 |
一般工业技术 | 594篇 |
冶金工业 | 797篇 |
原子能技术 | 73篇 |
自动化技术 | 167篇 |
出版年
2023年 | 14篇 |
2022年 | 30篇 |
2021年 | 67篇 |
2020年 | 20篇 |
2019年 | 40篇 |
2018年 | 46篇 |
2017年 | 54篇 |
2016年 | 50篇 |
2015年 | 49篇 |
2014年 | 61篇 |
2013年 | 141篇 |
2012年 | 100篇 |
2011年 | 116篇 |
2010年 | 105篇 |
2009年 | 109篇 |
2008年 | 124篇 |
2007年 | 120篇 |
2006年 | 117篇 |
2005年 | 100篇 |
2004年 | 90篇 |
2003年 | 105篇 |
2002年 | 87篇 |
2001年 | 81篇 |
2000年 | 64篇 |
1999年 | 93篇 |
1998年 | 314篇 |
1997年 | 189篇 |
1996年 | 150篇 |
1995年 | 113篇 |
1994年 | 91篇 |
1993年 | 82篇 |
1992年 | 62篇 |
1991年 | 41篇 |
1990年 | 37篇 |
1989年 | 47篇 |
1988年 | 44篇 |
1987年 | 36篇 |
1986年 | 37篇 |
1985年 | 30篇 |
1984年 | 27篇 |
1983年 | 32篇 |
1982年 | 26篇 |
1981年 | 26篇 |
1980年 | 22篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 28篇 |
1976年 | 46篇 |
1975年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有3548条查询结果,搜索用时 15 毫秒
1.
Hideaki Kaneto Tomohiko Kimura Atsushi Obata Masashi Shimoda Kohei Kaku 《International journal of molecular sciences》2021,22(5)
While there are various kinds of drugs for type 2 diabetes mellitus at present, in this review article, we focus on metformin which is an insulin sensitizer and is often used as a first-choice drug worldwide. Metformin mainly activates adenosine monophosphate-activated protein kinase (AMPK) in the liver which leads to suppression of fatty acid synthesis and gluconeogenesis. Metformin activates AMPK in skeletal muscle as well, which increases translocation of glucose transporter 4 to the cell membrane and thereby increases glucose uptake. Further, metformin suppresses glucagon signaling in the liver by suppressing adenylate cyclase which leads to suppression of gluconeogenesis. In addition, metformin reduces autophagy failure observed in pancreatic β-cells under diabetic conditions. Furthermore, it is known that metformin alters the gut microbiome and facilitates the transport of glucose from the circulation into excrement. It is also known that metformin reduces food intake and lowers body weight by increasing circulating levels of the peptide hormone growth/differentiation factor 15 (GDF15). Furthermore, much attention has been drawn to the fact that the frequency of various cancers is lower in subjects taking metformin. Metformin suppresses the mechanistic target of rapamycin (mTOR) by activating AMPK in pre-neoplastic cells, which leads to suppression of cell growth and an increase in apoptosis in pre-neoplastic cells. It has been shown recently that metformin consumption potentially influences the mortality in patients with type 2 diabetes mellitus and coronavirus infectious disease (COVID-19). Taken together, metformin is an old drug, but multifaceted mechanisms of action of metformin have been unraveled one after another in its long history. 相似文献
2.
3.
4.
5.
Metallothionein (MT) synthesis induced by the inflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF), was studied in vivo. Administration of recombinant human IL-6 or TNF to rats caused the acute phase responses including rapid decreases in plasma zinc (Zn), and increases in plasma copper (Cu) and ceruloplasmin. Hepatic concentration of MT-I, one of MT isoforms, began to increase within 3 h after the injection of IL-6 or TNF. In IL-6-treated rats, MT-I concentration in liver reached a maximum level at 12 h and decreased with a transient rebound, whereas, in TNF-treated rats, a high level of MT-I lasted for about 48 h. MT-II, the other MT isoform, was induced more than MT-I in liver by both cytokines. MT-I was also induced in lung and heart by TNF, but little by IL-6. The data suggest that IL-6 may be responsible for MT synthesis in liver, whereas TNF may be responsible not only in liver but also in lung and heart. Furthermore plasma concentration of MT did not always reflect the enhanced concentration of MT by TNF and IL-6 in liver, suggesting involvement of many factors influencing plasma MT levels. The interrelation between IL-6 and TNF for MT synthesis has also been discussed. 相似文献
6.
Sugawara F. Aoki K. Yamaguchi H. Sasaki K. Sasaki T. Fujisaki H. 《Electron Device Letters, IEEE》1997,18(10):483-485
A new lateral MOS-gated thyristor, called the Base-Current-Controlled Thyristor, is described. This device is designed so that most holes at the on-stage reach the P base through the floating P+ region adjacent to the P base and the on-state MOSFET. At the turn-off stage, the interruption of the hole current to the P base due to switching off the above MOSFET occurs simultaneously with the conventional turn-off operation. The concept of this device is verified experimentally by using the fabricated lateral device with the external MOSFET. This device exhibits a better trade-off relation between the on-state voltage and the turn-off time compared uith the conventional MOS-gated thyristor 相似文献
7.
Heterogeneous curable compositions of divalent metal salts of mono(hydroxyethyl) phthalate–anhydride–bisphenol A diglycidyl ether (BADG) systems were prepared by merely mixing these components at room temperature. Stability at room temperature and cure properties at high temperature of the compositions were investigated for evaluating their applicability as one part adhesive. It was found that the systems containing Mg were generally more stable than those containing Ca. Similarly, at 150°C the Ca-containing systems showed generally shorter gelation time than the Mg-containing ones, due to the fact that the Ca salt dissolves more rapidly and enters into the addition reaction with the anhydride, leading to the faster appearance of the catalytic activities of the Ca carboxylate group. Among the various combinations of components, the metal salt–succinic anhydride (SA)–BADG systems were stable at room temperature for more than 6 months and rapidly cured at high temperature, showing excellent adhesive properties. This result indicates that the SA-containing systems should be of interest in applications to one part adhesives. 相似文献
8.
T. Takeuchi T. Sasaki M. Hayashi K. Hamamoto K. Makita K. Taguchi K. Komatsu 《Photonics Technology Letters, IEEE》1996,8(3):361-363
A transceiver PIC consisting of a DFB-LD, a receiver PD and a Y-shaped branch waveguides is realized by in-plane bandgap energy controlled selective MOVPE. Both active and passive core layers are formed in one step selective growth, and complicated fabrication procedure is no longer required. More than 1 mW fiber coupled power and 7 GHz receiver bandwidth are obtained. The modulation and detection operations at 500 Mb/s are successfully demonstrated. 相似文献
9.
10.
Using a mullite (3Al2O3 · 2SiO2)-tube and ZrO2-9 mol pct MgO-plug type solid electrolyte galvanic cells, the activities of supersaturated oxygen in Fe-0.0017 to 0.41 mass
pct Al-M (M=C, Te, Mn, Cr, Si, Ti, Zr, and Ce) alloys were measured as a function of total Al or M contents at 1873 K in an alumina
crucible. Based on these results, the effects of alloying elements on the supersaturated oxygen activity with respect to alumina
precipitation were studied. In the Fe-Al-M (M=C, Te, Mn, Cr, and Si) alloys, the supersaturated oxygen activities for a given Al level approach the equilibrium values
with increasing contents of alloying elements. However, the oxygen activities for a given Al level are still supersaturated
in the Fe-Al-M (M=Ti, Zr, and Ce) alloys even in the presence of considerable amounts of the alloying elements. 相似文献