全文获取类型
收费全文 | 21526篇 |
免费 | 5657篇 |
国内免费 | 128篇 |
专业分类
耳鼻咽喉 | 627篇 |
儿科学 | 649篇 |
妇产科学 | 696篇 |
基础医学 | 385篇 |
口腔科学 | 2650篇 |
临床医学 | 4156篇 |
内科学 | 5113篇 |
皮肤病学 | 456篇 |
神经病学 | 1821篇 |
特种医学 | 984篇 |
外科学 | 3825篇 |
综合类 | 54篇 |
现状与发展 | 12篇 |
预防医学 | 2694篇 |
眼科学 | 319篇 |
药学 | 220篇 |
中国医学 | 6篇 |
肿瘤学 | 2644篇 |
出版年
2024年 | 163篇 |
2023年 | 1091篇 |
2022年 | 354篇 |
2021年 | 636篇 |
2020年 | 1213篇 |
2019年 | 482篇 |
2018年 | 1322篇 |
2017年 | 1287篇 |
2016年 | 1499篇 |
2015年 | 1562篇 |
2014年 | 1962篇 |
2013年 | 2370篇 |
2012年 | 771篇 |
2011年 | 728篇 |
2010年 | 1363篇 |
2009年 | 1938篇 |
2008年 | 746篇 |
2007年 | 509篇 |
2006年 | 654篇 |
2005年 | 471篇 |
2004年 | 333篇 |
2003年 | 316篇 |
2002年 | 258篇 |
2001年 | 402篇 |
2000年 | 284篇 |
1999年 | 389篇 |
1998年 | 502篇 |
1997年 | 485篇 |
1996年 | 533篇 |
1995年 | 388篇 |
1994年 | 304篇 |
1993年 | 261篇 |
1992年 | 180篇 |
1991年 | 158篇 |
1990年 | 137篇 |
1989年 | 147篇 |
1988年 | 127篇 |
1987年 | 130篇 |
1986年 | 109篇 |
1985年 | 99篇 |
1984年 | 80篇 |
1983年 | 89篇 |
1982年 | 82篇 |
1981年 | 67篇 |
1980年 | 45篇 |
1979年 | 34篇 |
1978年 | 32篇 |
1977年 | 45篇 |
1976年 | 32篇 |
1975年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Color Stability of Dry Earth Pigmented Maxillofacial Silicone A-2186 Subjected to Microwave Energy Exposure 总被引:2,自引:0,他引:2
Sudarat Kiat-amnuay DDS MS ; Dennis A. Johnston PhD ; John M. Powers PhD ; Rhonda F. Jacob DDS MS 《Journal of prosthodontics》2005,14(2):91-96
PURPOSE: The purpose of this study was to measure spectrophotometrically the color stability of pigmented A-2186 silicone maxillofacial elastomer with 10% by volume of titanium white dry earth opacifier before and after exposure to microwave energy over a simulated 1.5-year period of microwave sterilization. Materials AND METHODS: A-2186 silicone elastomer opacified with titanium white dry earth pigment, pigmented with 5 cosmetic dry earth pigment colors [no pigment (control) group (Pc), red (Pr), yellow ochre (Py), burnt sienna (Po), and a mixture of Pr + Py + Po color group (P3)], was used in this study. Each of the 5 experimental groups consisted of 5 specimens. All specimens were placed in a 250 ml glass beaker filled with 150 ml of water (replenished for each microwave exposure). An exposure of 6 minutes was used 18 times (simulating 1.5 years of microwave sterilization with one 6 minute exposure monthly). Reflectance values were measured by spectrophotometer. Three- and two-way analyses of variance with repeated measures were performed for the color difference (DeltaE*) with the factors of group/color/months, and group/months, respectively. Means were compared by Tukey Honest Significant Difference (HSD) multiple range test calculated at the 0.05 level of significance using SPSS. RESULTS: The trained human eye can detect color changes (DeltaE*) greater than 1.0. Most DeltaE* values of the red pigment group at all intervals and the mixed pigment group at 15- and 18- month intervals increased significantly greater than 1.0 (p < 0.001) compared with the control group. Yellow and burnt sienna groups remained the most color stable over time with DeltaE* values below 0.35. CONCLUSIONS: Lack of color stability of red dry earth pigmented A-2186 silicone maxillofacial elastomers was clinically significant after 12-month exposure to microwave energy as compared with yellow, burnt sienna, and opacified A-2186 dry earth pigments. 相似文献
22.
23.
24.
25.
26.
Robert P. Kusy BS MS PhD 《American journal of orthodontics and dentofacial orthopedics》2004,125(6):726-732
Using an earlier model, which described the critical contact angle for binding from second-order angulation alone, a more generalized model is derived that combines the effects of angulation and torque. From this vantage point, the onset of binding is evaluated for 3 scenarios: second-order angulation alone, third-order torque only, and a combination of second-order angulation and third-order torque. These scenarios are detailed by plotting the critical contact angle for binding against the torque angle as a function of 10 wire dimensions (16 x 16, 16 x 22, 17 x 17, 17 x 22, 17 x 25, 18 x 18, 18 x 22, 18 x 25, 19 x 25, and 21 x 25 mil), 4 bracket widths (70, 100, 130, and 160 mil), and 4 bracket slots (18, 20.5, 22, and 24.5 mil). From these plots, we learn that each wire base dimension (eg, an 18-mil base as found in 18 x 18-mil, 18 x 22-mil and 18 x 25-mil archwires) has a common maximum critical contact angle for binding. Moreover, each wire-slot combination has a common maximum torque angle, which is independent of bracket width. Finally, we learn that archwire-bracket combinations that use a metric 0.5-mm slot might have some advantages with regard to torquing--given the current philosophy that light, continuous forces are more favorable. 相似文献
27.
28.
29.
30.