全文获取类型
收费全文 | 17582篇 |
免费 | 1812篇 |
国内免费 | 1258篇 |
专业分类
电工技术 | 1549篇 |
综合类 | 1759篇 |
化学工业 | 2203篇 |
金属工艺 | 871篇 |
机械仪表 | 1165篇 |
建筑科学 | 1082篇 |
矿业工程 | 510篇 |
能源动力 | 489篇 |
轻工业 | 1877篇 |
水利工程 | 417篇 |
石油天然气 | 399篇 |
武器工业 | 249篇 |
无线电 | 1806篇 |
一般工业技术 | 1419篇 |
冶金工业 | 2176篇 |
原子能技术 | 297篇 |
自动化技术 | 2384篇 |
出版年
2024年 | 87篇 |
2023年 | 261篇 |
2022年 | 588篇 |
2021年 | 774篇 |
2020年 | 546篇 |
2019年 | 400篇 |
2018年 | 423篇 |
2017年 | 496篇 |
2016年 | 423篇 |
2015年 | 702篇 |
2014年 | 831篇 |
2013年 | 1064篇 |
2012年 | 1291篇 |
2011年 | 1330篇 |
2010年 | 1305篇 |
2009年 | 1235篇 |
2008年 | 1244篇 |
2007年 | 1256篇 |
2006年 | 1037篇 |
2005年 | 908篇 |
2004年 | 652篇 |
2003年 | 472篇 |
2002年 | 441篇 |
2001年 | 385篇 |
2000年 | 325篇 |
1999年 | 143篇 |
1998年 | 544篇 |
1997年 | 304篇 |
1996年 | 245篇 |
1995年 | 145篇 |
1994年 | 121篇 |
1993年 | 132篇 |
1992年 | 37篇 |
1991年 | 36篇 |
1990年 | 36篇 |
1989年 | 40篇 |
1988年 | 33篇 |
1987年 | 28篇 |
1986年 | 21篇 |
1985年 | 24篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 23篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 48篇 |
1976年 | 112篇 |
1971年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
G La Nasa A Pizzati A Ledda A Vacca M Arras L Contu 《Canadian Metallurgical Quarterly》1996,81(2):178-181
OBJECTIVE: To determine the distribution and amount of elastic fibers in the dermis of clinically normal dogs and dogs with dermatoses, particularly solar dermatitis. DESIGN: Skin specimens from 7 anatomic sites were obtained from 19 clinically normal dogs after euthanasia to evaluate the normal distribution of elastic fibers. Biopsy specimens also were obtained from 34 dogs with dermatoses, including 16 with solar dermatitis. Tissue sections were stained with H&E, Verhoeff-van Gieson, and periodic acid-Schiff. ANIMALS: 19 clinically normal dogs and 34 dogs with dermatoses. PROCEDURE: Numbers of elastic fibers were graded subjectively. Comparisons between clinically normal dogs and dogs with dermatoses were made. RESULTS: Normal elastic fibers were present in low numbers in the dermis of adult dogs, regardless of anatomic site or presence or severity of dermatitis. Condensed elastotic material was visualized in only 2 dogs with solar dermatitis. In both dogs, the elastotic material was Verhoeff-van Gieson and periodic acid-Schiff stain positive but was not visible with H&E stain. The most frequent histopathologic finding in the dermis of dogs with solar dermatitis was superficial dermal fibrosis. CONCLUSIONS: The dermis of clinically normal dogs does not contain abundant elastic fibers. Alterations of elastic fibers in dogs with solar dermatitis are rare. Superficial dermal fibrosis may be a better indicator of solar damage. 相似文献
12.
Methodological issues in geropsychological assessment research are discussed and exemplified with recent investigations. Increased use of short-term longitudinal designs, more diverse and representative sampling, and routine inclusion of measures of health are among the recommendations made for future studies. Caution is urged in the application of new tests or screening batteries until sufficient independent validation studies are completed. Research contrasting neuropsychological performance of older persons from different racial and ethnic groups is briefly reviewed, and applications of geropsychological assessment to practical arenas such as competency determination are critiqued. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
本文首先概述了编辑出版自动化技术的概念及最新进展,然后就其在医药专业期刊编辑部的初步应用进行了探讨,论述了计算机、网络、数据库技术在稿件的选题、组稿、编辑、审校、排版、印刷、出版中的具体应用,强调了构建基于网络的编辑出版自动化系统对期刊现代化建设的重要作用。 相似文献
14.
攀钢转炉炼钢用碳化硅提温的试验研究 总被引:1,自引:1,他引:0
低品位碳化硅是转炉炼钢的有效提高温剂。工业性试验结果表明,碳化硅加入8.0kg/t钢水提温40.3-70.3℃(平均48.4℃);渣中TFe降低1.3%;加提温剂有利于转炉内造渣脱硫和碱少炉渣对耐火砖的侵蚀。文中还给出了攀钢转炉半钢冶炼铸用钢不水时加与不加碳化硅的tλ,[C]λ区域。 相似文献
15.
16.
BACKGROUND: The matrix metalloproteinases (MMPs) MMP2 and MMP9 play a significant role in epidermal detachment, inflammation and re-epithelialization. We have evaluated their activity in toxic epidermal necrolysis (TEN). DESIGN: The level and pattern of activity of MMP2 and MMP9 were investigated by measuring the degradation of 3H-labelled gelatin and by zymography in blister fluid from six TEN patients and compared the results with three other blistering conditions: bullous pemphigoid (n = 6), second-degree burn (n = 13) or suction blister (n = 3). RESULTS: A higher amount of MMP2 was found in TEN blister fluid with the constant presence of a significantly larger proportion of the activated forms of MMP2, a particular feature of TEN, than the other blistering diseases studied. CONCLUSION: This study emphasizes the potential role of MMP2 in the specific inflammatory reaction and reparation process in TEN skin. 相似文献
17.
18.
19.
Ws/Ws rats are deficient in both mucosal- and connective tissue-type mast cells. To study the role of mast cells in active anaphylaxis, changes in vascular permeability in the trachea upon intravenous antigen challenge with Evans blue dye were examined in Ws/Ws, heterogenic Ws/+, and normal +/ + rats sensitized with the nematode Nippostrongylus brasiliensis. Antigen challenge resulted in fatal anaphylactic shock in some +/+ and Ws/+ rats, but not in Ws/Ws rats. Marked dye leakage developed within 30 min in the trachea of +/+ and Ws/+ rats, while Ws/Ws rats showed no substantial increases in the levels of vascular permeability. Ex vivo stimulation of sensitized lung fragments from +/+ animals with specific antigen induced significant releases of histamine and leukotriene (LT) C4, while sensitized Ws/Ws rat-lung fragments did not. In Ws/Ws rats, levels of nematode-specific IgE, IgG1 and IgG2a antibodies as well as levels of lung eosinophilia were not significantly different from those in +/+ rats. These results show that mast cell-deficient Ws/Ws rats fail to develop active anaphylaxis, and this is mediated probably by the lack of mast cell-derived mediators required for initiation of the reaction. 相似文献
20.
This study sought to determine whether persons of French-Canadian heritage in northern New England are at high risk for the lethal infantile form of Tay-Sachs disease. In order to accomplish this, death records and laboratory diagnostic records were surveyed to ascertain Tay-Sachs deaths in a cohort of 372,000 live births between 1977-1986. The proportion of the total population with French-Canadian or Jewish heritage was determined from census and birth records, and the ethnic background of Tay-Sachs cases was determined from the corresponding birth records. In 1,860 births, both parents were of Ashkenazi Jewish heritage. One of those children was diagnosed with Tay-Sachs disease. In 41,000 births, both parents were of French-Canadian heritage, and in an additional 93,000 births, one parent was of French-Canadian heritage. No cases of Tay-Sachs disease were identified in the offspring of those individuals. Approximately 14 cases (95% confidence interval 8-20) would be expected, if the gene frequency approximated that reported for individuals of Ashkenazi Jewish heritage. Based on the results of this study, routine testing for Tay-Sachs disease heterozygosity is not indicated for persons of French-Canadian heritage in northern New England. This conclusion may not necessarily be valid for persons of French-Canadian heritage residing in other states. Further studies of Tay-Sachs disease mutations and prevalence among persons of French-Canadian heritage will be important to determine possible regional variations in gene frequencies. 相似文献