全文获取类型
收费全文 | 281619篇 |
免费 | 4953篇 |
国内免费 | 2090篇 |
专业分类
电工技术 | 6165篇 |
技术理论 | 6篇 |
综合类 | 2132篇 |
化学工业 | 41182篇 |
金属工艺 | 11308篇 |
机械仪表 | 9333篇 |
建筑科学 | 8325篇 |
矿业工程 | 1674篇 |
能源动力 | 8012篇 |
轻工业 | 22753篇 |
水利工程 | 2698篇 |
石油天然气 | 5184篇 |
武器工业 | 174篇 |
无线电 | 37371篇 |
一般工业技术 | 53552篇 |
冶金工业 | 50062篇 |
原子能技术 | 5462篇 |
自动化技术 | 23269篇 |
出版年
2022年 | 2182篇 |
2021年 | 3224篇 |
2020年 | 2363篇 |
2019年 | 2589篇 |
2018年 | 4035篇 |
2017年 | 4146篇 |
2016年 | 4231篇 |
2015年 | 3204篇 |
2014年 | 5288篇 |
2013年 | 13102篇 |
2012年 | 7893篇 |
2011年 | 10478篇 |
2010年 | 8616篇 |
2009年 | 9550篇 |
2008年 | 9964篇 |
2007年 | 9701篇 |
2006年 | 8767篇 |
2005年 | 7771篇 |
2004年 | 7234篇 |
2003年 | 7536篇 |
2002年 | 7081篇 |
2001年 | 7527篇 |
2000年 | 6757篇 |
1999年 | 7247篇 |
1998年 | 17177篇 |
1997年 | 11970篇 |
1996年 | 9302篇 |
1995年 | 7030篇 |
1994年 | 6270篇 |
1993年 | 6103篇 |
1992年 | 4338篇 |
1991年 | 4173篇 |
1990年 | 3974篇 |
1989年 | 3749篇 |
1988年 | 3632篇 |
1987年 | 3064篇 |
1986年 | 2985篇 |
1985年 | 3223篇 |
1984年 | 2949篇 |
1983年 | 2847篇 |
1982年 | 2652篇 |
1981年 | 2558篇 |
1980年 | 2470篇 |
1979年 | 2315篇 |
1978年 | 2112篇 |
1977年 | 2607篇 |
1976年 | 3571篇 |
1975年 | 1766篇 |
1974年 | 1732篇 |
1973年 | 1669篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
994.
995.
The problem of pattern recognition is discussed in terms of single-entity representation versus multiple-entity representation. A combined syntactic-semantic approach based on attributed grammars is suggested. Syntax-semantics tradeoff in pattern representation is demonstrated. This approach is intended to be an initial step toward unification of syntactic and statistical approaches to pattern recognition. 相似文献
996.
997.
The meat quality of M. longissimus muscle was evaluated in 851 pigs by using the Fibre Optic Probe (FOP) at three sites in the muscle and in both halves of the carcass. A systematic difference between sites was found, with the lowest light scattering (indicating the best meat quality) in the mid-part of the muscle and higher light scattering in the anterior and posterior parts. A non-systematic variation was also observed, with the opposite pattern in some animals, even though it was not frequent. A negative influence of the shackling was found, yielding higher FOP values in the shackled half.
Drip loss measurements in the Longissimus muscle, taken from another 100 pig carcasses, were evaluated using three methods. Drip loss, too, showed a considerable variation along the Longissimus muscle, with minimum losses around the last rib. Repeatability estimates, calculated from two non-consecutive pieces of the Longissimus dorsi muscle from each carcass, varied from 0·4 when keeping samples vacuum packed for 2 days, to 0·5 when the samples were either kept in plain plastic bags for 2 days or in a meat container with a squared inset for 1 or 2 days. 相似文献
998.
999.
1000.
M. longissimus dorsi total pigment concentration, visual color score and 24-h pH values were evaluated in a 2(3) factorial design that included bulls versus steers, Zeranol implants versus control and Angus versus Limousin comparisons. Bulls had greater total pigment concentration than steers (3.25 versus 2·90 mg/g; P < 0·01) and darker colored lean (P < 0·01). Twenty-four hour pH values did not differ between bulls and steers. Zeranol implanting and breed had no effect on total pigment concentration or visual color score; however, Limousin had higher (P < 0·05) 24-h pH values than Angus. The initial slaughter group (N = 10; average age = 256 days) had 34% less total pigment than the final slaughter group (N = 48; average age = 458 days). The correlation between visual color score and total pigment concentration was -0·65. These results indicate that the darker colored lean from bulls is due in part to an increase in pigment concentration. 相似文献