全文获取类型
收费全文 | 66253篇 |
免费 | 6734篇 |
国内免费 | 3775篇 |
专业分类
电工技术 | 5027篇 |
技术理论 | 2篇 |
综合类 | 6264篇 |
化学工业 | 4489篇 |
金属工艺 | 2984篇 |
机械仪表 | 4872篇 |
建筑科学 | 1811篇 |
矿业工程 | 2013篇 |
能源动力 | 631篇 |
轻工业 | 6186篇 |
水利工程 | 699篇 |
石油天然气 | 1736篇 |
武器工业 | 1118篇 |
无线电 | 13855篇 |
一般工业技术 | 4948篇 |
冶金工业 | 2243篇 |
原子能技术 | 547篇 |
自动化技术 | 17337篇 |
出版年
2024年 | 303篇 |
2023年 | 939篇 |
2022年 | 1401篇 |
2021年 | 1801篇 |
2020年 | 1778篇 |
2019年 | 1323篇 |
2018年 | 1255篇 |
2017年 | 1737篇 |
2016年 | 1939篇 |
2015年 | 2428篇 |
2014年 | 3650篇 |
2013年 | 3562篇 |
2012年 | 4589篇 |
2011年 | 5143篇 |
2010年 | 3872篇 |
2009年 | 4039篇 |
2008年 | 4174篇 |
2007年 | 4986篇 |
2006年 | 4487篇 |
2005年 | 3974篇 |
2004年 | 3192篇 |
2003年 | 2851篇 |
2002年 | 2251篇 |
2001年 | 1822篇 |
2000年 | 1594篇 |
1999年 | 1195篇 |
1998年 | 981篇 |
1997年 | 877篇 |
1996年 | 795篇 |
1995年 | 666篇 |
1994年 | 599篇 |
1993年 | 487篇 |
1992年 | 365篇 |
1991年 | 299篇 |
1990年 | 274篇 |
1989年 | 236篇 |
1988年 | 171篇 |
1987年 | 96篇 |
1986年 | 80篇 |
1985年 | 95篇 |
1984年 | 84篇 |
1983年 | 88篇 |
1982年 | 66篇 |
1981年 | 47篇 |
1980年 | 39篇 |
1979年 | 37篇 |
1978年 | 22篇 |
1977年 | 27篇 |
1976年 | 12篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
反散射成像法是数字辐射成像的主要方法之一,介绍了获得反散射数字图像的实验装置,并着重分析了针对此装置获得的反散性图像的处理方法。 相似文献
13.
14.
P. Powell 《Information Systems Journal》1992,2(4):269-280
Abstract. Expert systems proliferate. They are now a usable and used tool in a variety of organizations. However, little research has been undertaken on the quantification of success or failure of expert system projects. By and large the only test carried out for expert system validation is one of comparison of the conclusions of the system with those of an expert or team of experts. While questioning the validity, this paper accepts that this method is being used and analyses whether or not the results obtained from this type of test should be a surprise. That is, what sort of results should be expected and to what extent do the reported ones live up to these expectations? Earlier research from the field of human information processing casts doubts on the success claims made for current expert systems. The implications of this research are then analysed in order to explore the possible redeeming features of expert systems which are not taken into account in such comparisons. The use of linear models as comparators for expert systems may prove beneficial. 相似文献
15.
We have isolated a mutant which exhibits partial constitutivity for a -specific gene expression in α cells. The wild-type gene was cloned and demonstrated to be allelic to the STE13 gene, which encodes the dipeptidyl aminopeptidase involved in processing of the α-factor prepropheromone. Thus, the mating defect of the ste13 mutations in α cells may result both from the production of incompletely processed α-factor and from the increased expression of a -specific genes. The STE13 open reading frame of 931 amino acids contains a putative membrane-spanning segment near its amino terminus and is 31% identical to a second yeast dipeptidyl aminopeptidase (DAP2). A null mutant of STE13 has been constructed: it is viable and sporulation-proficient. The sequence has been deposited in the GenBank data library under Accession Number L21944. 相似文献
16.
17.
Food products can be high‐pressure processed (HPP) either in bulk or prepackaged in flexible or semi‐rigid packaging materials. In the latter case the packaging material is subjected, together with the food, to high‐pressure treatment. A number of studies have been performed to quantify the effects of high‐pressure processing on the physical and barrier properties of the packaging material, since the integrity of the package during and after processing is of paramount importance to the safety and quality of the food product. This article reviews the results of published research concerning the effect of HPP on packaging materials. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
18.
19.
Reviews the book, ILe choc de l'informatique: Les répercussions psychosociales et le r?le des attitudes by Serge Guimond and Guy Bégin (1987). This monograph is concise and easy to read. The reader knows immediately that technological questions will be explored, as well as the psychological and human questions being attached to the new use of information technology. Three fields are covered, each one the subject of a chapter: 1) computers in the educational circle; 2) computers and work; and 3) computers in the house. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
20.
Narendra Singh Shah & Nirankar Nath 《International Journal of Food Science & Technology》2006,41(9):1073-1081
Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D6 Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis. 相似文献