全文获取类型
收费全文 | 2986篇 |
免费 | 56篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 168篇 |
综合类 | 23篇 |
化学工业 | 633篇 |
金属工艺 | 67篇 |
机械仪表 | 65篇 |
建筑科学 | 53篇 |
能源动力 | 94篇 |
轻工业 | 270篇 |
水利工程 | 19篇 |
石油天然气 | 7篇 |
无线电 | 355篇 |
一般工业技术 | 433篇 |
冶金工业 | 649篇 |
原子能技术 | 41篇 |
自动化技术 | 178篇 |
出版年
2023年 | 11篇 |
2022年 | 30篇 |
2021年 | 42篇 |
2020年 | 13篇 |
2019年 | 25篇 |
2018年 | 31篇 |
2017年 | 29篇 |
2016年 | 32篇 |
2015年 | 34篇 |
2014年 | 55篇 |
2013年 | 120篇 |
2012年 | 103篇 |
2011年 | 99篇 |
2010年 | 90篇 |
2009年 | 97篇 |
2008年 | 104篇 |
2007年 | 112篇 |
2006年 | 99篇 |
2005年 | 94篇 |
2004年 | 82篇 |
2003年 | 83篇 |
2002年 | 91篇 |
2001年 | 81篇 |
2000年 | 51篇 |
1999年 | 86篇 |
1998年 | 251篇 |
1997年 | 186篇 |
1996年 | 130篇 |
1995年 | 68篇 |
1994年 | 79篇 |
1993年 | 80篇 |
1992年 | 43篇 |
1991年 | 57篇 |
1990年 | 41篇 |
1989年 | 46篇 |
1988年 | 28篇 |
1987年 | 29篇 |
1986年 | 39篇 |
1985年 | 49篇 |
1984年 | 33篇 |
1983年 | 32篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 11篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1973年 | 6篇 |
1972年 | 9篇 |
排序方式: 共有3055条查询结果,搜索用时 0 毫秒
81.
Male Fischer 344 rats were subcutaneously injected with azoxymethane (AOM) twice weekly at a dose of 15 mg/kg and were fed with freeze-dried (FD) samples of beer brewed without hops (non-hops beer), beer with hops at 4 times the amount of regular lager beer (x 4-hops beer), and isomerized hop extract (IHE) for the whole experimental period (I/PI) or for the post-initiation period (PI) only. Feeding FD beer samples at a dose of 1% significantly decreased the number of aberrant cryp foci (ACF) in the PI protocol over five weeks.x4-hops beer showed stronger inhibitory effects on the development of the numbers of aberrant crypts per focus and large ACF with four or more crypts than non-hops beer. Feeding IHE to rats at a dose of 0.01% or 0.05% in either the I/PI or PI experiment significantly reduced the numbers of ACF. Prostaglandin E2 (PGE2) levels in colonic mucosa of AOM-treated rats were significantly reduced by feeding of IHE. PGE2 production induced by lipopolysaccharide/interferon-gamma (LPS/IFN-gamma) in RAW264.7 cells was also reduced by treatment with IHE and isohumulone in a dose-dependent manner. These observations suggest that isohumulones show chemopreventive effects on ACF formation in rat colon by inhibiting the production of PGE2. 相似文献
82.
Jun Nishihira Maremi Sato-Ueshima Kentaro Kitadate Koji Wakame Hajime Fujii 《Journal of Functional Foods》2009,1(4):341-348
The effect of low-molecular-weight polyphenols extracted from lychee (Oligonol) on metabolic syndrome characterized by abdominal obesity was examined. We performed a clinical trial for Oligonol conducted by randomized double-blind, placebo-controlled study. Eighteen (male, 14; female, 4) adult volunteers with abdominal circumference over 85 cm were enrolled and divided into two groups, Oligonol and placebo groups. All subjects took two capsules of Oligonol (50 mg/capsule) or placebo twice a day for 10 weeks. Physical and haematological examinations as well as a CT scan of the abdomen were carried out, before (control) and 10 weeks after Oligonol intake. Clinical parameters of body weight, abdominal circumference and visceral fat volume were significantly decreased in the Oligonol group compared to the control. Insulin resistance was improved by Oligonol in conjunction with elevation of serum adiponectin. These results suggest that Oligonol ameliorates metabolic syndrome by reducing visceral fat obesity. 相似文献
83.
Sugano M Shimizu T Komatsu A Kakuta Y Hirano K 《Environmental science & technology》2011,45(6):2493-2497
Additive effects of glass powder upon the product yields and chlorine distribution after liquefaction of hydrothermally pretreated mixed waste (HMW) are compared with liquefaction of HMW with any one of water, quartz sand, or glass powder plus water. As a result, addition of either water or quartz sand did not affect liquefaction and dechlorination of HMW. Further, water (5 g) addition did not enhance liquefaction and dechlorination of HMW with glass powder. On the other hand, after liquefaction of HMW with glass powder, the yields of chlorine in the gas and water insoluble constituents decreased and the chlorine yield in the water-soluble constituent increased significantly. Because sodium in glass powder dissolved in a small amount (0.5 g) of water resulted from dehydration of HMW during liquefaction. Further, hydrogen chloride derived from polyvinylchloride in HMW was neutralized by ion exchange between H(+) and Na(+) dissolved in a small amount of water forming NaCl in the Residue (water-soluble) constituent. Therefore, most of chlorine in HMW was removed easily by water extraction of the Residue constituent after liquefaction of HMW with glass powder. Further, upgrading of HMW into the oil constituent was enhanced due to inhibition of production of chlorine containing organic compounds. Accordingly, it was clarified that glass powder was the most effective additive for liquefaction and dechlorination of HMW. 相似文献
84.
Yamamoto T Watanabe H Nishimoto T Aga H Kubota M Chaen H Fukuda S 《Journal of Bioscience and Bioengineering》2006,101(5):427-433
The glucosyl transfer reaction of kojibiose phosphorylase (KP; EC 2.4.1.230) was examined using glycerol or myo-inositol as an acceptor. In the case of glycerol, KP produced two main transfer products: saccharides A and B. The structure of saccharide A was O-alpha-D-glucopyranosyl-(1-->1)-glycerol and that of saccharide B was O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)-glycerol. These results show that KP transferred a glucose residue to the hydroxyl group at position 1 of glycerol. On the other hand, when myo-inositol was used as an acceptor, KP produced four transfer products: saccharides 1-4. The structures of saccharides 1 and 2 were O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively; those of saccharides 3 and 4 were O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->1)- and O-alpha-D-glucopyranosyl-(1-->2)-O-alpha-D-glucopyranosyl-(1-->5)-myo-inositol, respectively. KP transferred a glucose residue to the hydroxyl group at position 1 or 5 of myo-inositol. On the basis of the structures of their glucosyl transfer products, glycerol and myo-inositol were found to have a common structure with three hydroxyl groups corresponding to the hydroxyl group of the glucose molecule at positions 2, 3 and 4. The conformation of these three hydroxyl groups in the structure is equatorial. This structure is the substrate recognition site of KP. It has been suggested that KP strictly recognizes the structures of glycerol and myo-inositol, and catalyzes the transfer reaction of a glucose residue to the hydroxyl group at position 1 in glycerol, and at position 1 or 5 in myo-inositol, corresponding to position 2 in glucose. 相似文献
85.
86.
Kohji Ishida Kazuyuki Shimizu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,66(4):340-346
A novel repeated batch operation mode was proposed for ethanol fermentation, where the fermenter beer was periodically exchanged between the fermenter with biomass recycle and the distillation unit, to promote the selective removal of ethanol. Using the mathematical model developed, as based on the experimental results, the optimal operation of the proposed method was shown to attain high performance, with a productivity of about 12 g dm−3 h−1 and a product concentration of 400 g dm−3. 相似文献
87.
88.
Yasuaki Okamoto Hajime Nakano Takafumi Shimokawa Toshinobu Imanaka Shiichiro Teranishi 《Journal of Catalysis》1977,50(3):447-454
The promotional effects of Co in hydrodesulfurization (HDS) catalysts were studied by means of X-ray photoelectron spectroscopy. The higher MoO3-content catalysts (10 and 20 wt% MoO3) contain mobile Mo, which migrates from the pores to the outermost surface layers of the catalysts and segregates to form less active crystalline MoS2 during the HDS reaction, while in the case of (5 wt% MoO3) catalyst: no migration of Mo was observed. It is revealed that the Co in catalyst inhibits the migration and segregation of Mo and that it keeps Mo effective for the HDS reaction, since no surface enrichment of Mo was observed. It is concluded that stabilization of the Mo monomolecular layer is the main role of Co. The active species of Mo is suggested to have the composition of S/Mo(IV) = 1 on the basis of the sulfur contents of the catalysts under the mild HDS reaction conditions. 相似文献
89.
Mouse embryonic stem (ES) cells have the pluripotent ability to differentiate in vitro into various cell lineages, including neurons. Adding chick dorsal root ganglion (DRG) conditioned medium (CM) to the culture medium promotes the differentiation of ES cells into neurons. We determined the types of neurons that differentiate from ES cells. The addition of DRG-CM caused nearly half of all ES cells on the periphery of the colony sphere to differentiate into neurons. Immunofluorescence analysis showed that the neurons that differentiated from ES cells were mainly motor, GABAergic, serotonergic, and cholinergic neurons. Of particular note, flow cytometry showed that approximately 50% of betaIII-tubulin-positive neurons were motor neurons. This indicates that DRG-CM induces ES cells to differentiate into motor neurons as target of DRG neurons (sensory neurons). 相似文献
90.