全文获取类型
收费全文 | 205761篇 |
免费 | 15376篇 |
国内免费 | 7808篇 |
专业分类
电工技术 | 11260篇 |
技术理论 | 14篇 |
综合类 | 11216篇 |
化学工业 | 35696篇 |
金属工艺 | 10538篇 |
机械仪表 | 11997篇 |
建筑科学 | 16408篇 |
矿业工程 | 4943篇 |
能源动力 | 5851篇 |
轻工业 | 12681篇 |
水利工程 | 3211篇 |
石油天然气 | 11072篇 |
武器工业 | 1345篇 |
无线电 | 25483篇 |
一般工业技术 | 26716篇 |
冶金工业 | 10934篇 |
原子能技术 | 2128篇 |
自动化技术 | 27452篇 |
出版年
2024年 | 881篇 |
2023年 | 3262篇 |
2022年 | 5828篇 |
2021年 | 7929篇 |
2020年 | 5799篇 |
2019年 | 5014篇 |
2018年 | 5418篇 |
2017年 | 6202篇 |
2016年 | 5694篇 |
2015年 | 7295篇 |
2014年 | 9522篇 |
2013年 | 12271篇 |
2012年 | 12226篇 |
2011年 | 13871篇 |
2010年 | 11611篇 |
2009年 | 11461篇 |
2008年 | 10872篇 |
2007年 | 10467篇 |
2006年 | 10857篇 |
2005年 | 9630篇 |
2004年 | 6563篇 |
2003年 | 5776篇 |
2002年 | 5251篇 |
2001年 | 4723篇 |
2000年 | 4868篇 |
1999年 | 5639篇 |
1998年 | 5283篇 |
1997年 | 4353篇 |
1996年 | 3957篇 |
1995年 | 3310篇 |
1994年 | 2768篇 |
1993年 | 2188篇 |
1992年 | 1700篇 |
1991年 | 1277篇 |
1990年 | 1018篇 |
1989年 | 877篇 |
1988年 | 681篇 |
1987年 | 496篇 |
1986年 | 394篇 |
1985年 | 334篇 |
1984年 | 212篇 |
1983年 | 198篇 |
1982年 | 163篇 |
1981年 | 145篇 |
1980年 | 131篇 |
1979年 | 97篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
The present study was undertaken to evaluate the postoperative relapse from the period of unwiring to 1 year postoperatively and its correlation to the amount of mandibular setback and change in vertical dimension after mandibular bilateral sagittal split osteotomy. Twenty-seven patients were evaluated cephalometrically by the time preoperatively, 6 weeks, 6 months and 1 year postoperatively. It was found that 1) the average amount of mandibular setback at pogonion point, 6 weeks postoperatively, is 7.6mm backward and 1.9mm downward, 2) the average amount of horizontal relapse at pogonion point, 6 months and 1 year postoperatively, are 1.9mm and 2.3mm respectively. 86% of the horizontal relapse, 1 year postoperatively, occurs in the first 6 months after removal of intermaxillary fixation, 3) the average amount of vertical relapse at pogonion point, 6 months and 1 year postoperatively, are 0.9mm and 1.1mm upward. 82% of the vertical relapse, 1 year postoperatively, occurs in the first 6 months after removal of intermaxillary fixation, 4) the amount of 1 year postoperatively horizontal relapse is significantly correlated both with the amount of horizontal mandibular set back and vertical downward change (r = 0.58, 0.67, p < 0.001), whereas the amount of vertical relapse is with the vertical downward change only, but horizontal setback isn't. 相似文献
104.
105.
V. S. -Kh. Kim V. A. Samoilov E. M. Sherysheva Chen Yun 《Chemical and Petroleum Engineering》1993,29(8):355-358
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 8, pp. 9–11, August, 1993. 相似文献
106.
107.
108.
Hamsters were fed high fiber diets containing cellulose, wheat bran or psyllium. The psyllium was incorporated into high fiber, ready-to-eat (RTE) flakes that were used to formulate the test diet. All the diets contained 0.125% cholesterol. The study was terminated after three weeks. Food intake, weight gain and feed efficiency were not significantly different in the three groups. Serum total and HDL cholesterol levels were reduced significantly by the psyllium diet. Serum triglycerides were 26% lower in the hamsters fed psyllium but because of the large variation the difference did not reach statistical significance. Liver total cholesterol and cholesteryl ester levels were significantly lower in the hamsters fed psyllium. Liver triglycerides were highest in the psyllium-fed hamsters and liver phospholipid levels were similar in the three groups. Liver cholesterol and triglyceride levels were higher in hamsters fed cellulose than in those fed wheat bran. Psyllium formulated into an RTE cereal was effective in reducing serum and liver cholesterol levels in hamsters. 相似文献
109.
The adoption of asymmetrical digital subscriber lines (ADSL) technology in conjunction with the broadcast digital subscriber lines (BDSL) proposed in this paper could provide a cost effective solution for the introduction of digital video services in the near term. BDSL provides the same digital broadcast video programs to all subscribers through existing twisted pair telephone loops. In this paper, the basics of telephone loop-based digital subscriber lines are first discussed. Then the potential of BDSL is explored in the twisted pair loop plant near end crosstalk (NEXT), far end crosstalk (FEXT), and white noise environment. The capability of BDSL is examined with different serving areas and transmit power levels. The possibility of using orthogonal quadrature amplitude modulation (QAM) to implement a zero guard-band BDSL system is studied. Computer BDSL performance simulations are then presented. The combination of high-bit-rate digital subscriber lines (HDSL), ADSL, and BDSL can provide telephone subscribers many digital broadband services 相似文献
110.