全文获取类型
收费全文 | 1234篇 |
免费 | 51篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 70篇 |
综合类 | 3篇 |
化学工业 | 353篇 |
金属工艺 | 23篇 |
机械仪表 | 20篇 |
建筑科学 | 28篇 |
矿业工程 | 1篇 |
能源动力 | 73篇 |
轻工业 | 92篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 114篇 |
一般工业技术 | 219篇 |
冶金工业 | 167篇 |
原子能技术 | 28篇 |
自动化技术 | 93篇 |
出版年
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 29篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 31篇 |
2015年 | 27篇 |
2014年 | 27篇 |
2013年 | 64篇 |
2012年 | 36篇 |
2011年 | 57篇 |
2010年 | 39篇 |
2009年 | 62篇 |
2008年 | 47篇 |
2007年 | 60篇 |
2006年 | 54篇 |
2005年 | 36篇 |
2004年 | 39篇 |
2003年 | 33篇 |
2002年 | 27篇 |
2001年 | 24篇 |
2000年 | 31篇 |
1999年 | 30篇 |
1998年 | 51篇 |
1997年 | 45篇 |
1996年 | 43篇 |
1995年 | 23篇 |
1994年 | 33篇 |
1993年 | 26篇 |
1992年 | 22篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有1287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.
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
5.
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
6.
K Sudo Y Matsumoto M Matsushima M Fujiwara K Konno K Shimotohno S Shigeta T Yokota 《Canadian Metallurgical Quarterly》1997,238(2):643-647
This study evaluated the inhibitory effects of thiazolidine derivatives on hepatitis C virus (HCV) protease and other human serine proteases. The inhibition efficacy was tested with a reversed-phase high-performance liquid chromatography (HPLC) assay system using a NS3-NS4A fusion protein as the HCV protease and a synthetic peptide substrate that mimics the NS5A-5B junction. Nine thiazolidine derivatives showed more than 50% inhibition at 50 microg/ml. The most potent derivative was RD4-6250, with 50% inhibition at a concentration of 2.3 microg/ml; this concentration was lower than those of other protease inhibitors reported previously. The most selective derivative was RD4-6205, with 50% inhibition at a concentration of 6.4 microg/ml, a lower concentration than those on other serine proteases (chymotrypsin, trypsin, plasmin, and elastase). These results suggest that the RD4-6205 skeleton is an important structure for inhibitory activity on the HCV protease NS3-NS4A. 相似文献
7.
8.
Hideaki Katayama Tsutomu Tawa Shinzaburo Ito Masahide Yamamoto Yoshio Wada 《Polymer Bulletin》1992,29(3-4):365-367
Summary The effect of side chain length on intramolecular triplet energy migration of naphthalene containing polymers was investigated by a delayed fluorescence (DF) spectroscopy for the solid solution of the polymers. The degree of triplet energy migration depends strongly on whether the chromophores are directly attached to the main chain or not. 相似文献
9.
This paper deals with an advanced static Var compensator (ASVC) using quad-series voltage-source PAM inverters. The ASVC consists of four three-phase voltage-source inverters with a common dc capacitor and four three-phase transformers, each primary winding of which is connected in series with each other. Each inverter outputs a square-wave voltage, while the synthesized output voltage of the ASVC has a 24-step wave shape. This results not only in a great reduction of harmonic currents and dc voltage ripples but also in fewer switching and snubbing losses. In this paper, transient analysis is performed with the focus on the response of reactive power and the resonance between the dc capacitor and ac reactors. Experimental results obtained from a small-rated laboratory model of 10 kVA are also shown to verify analytical results based on the p-q transformation. The analytical results help in the design of system parameters such as the capacity of the dc capacitor and feedback gains. 相似文献
10.
Optical and electronic properties of cobalt-doped zinc oxide films prepared by the sputtering method
In-doped ZnO, Co-doped ZnO and Li-doped NiO are successively deposited on quartz by the sputtering method. A current versus voltage curve of the three-layer device, in which the Indoped ZnO and Li-doped NiO are used as electrodes, reveals that the In-doped ZnO is an ohmic electrode and the Li-doped NiO is a blocking electrode with respect to electron injection. In photocurrent spectra of the three-layer device, there are two distinct peaks around 410 and 640 nm. The former is ascribed to the photoionization caused by the electric-dipole transition from the ground states,4A2(F), to the conduction band, and the latter to the thermal emission from electronic excited states of Co2+,4T1(P). 相似文献