全文获取类型
收费全文 | 122788篇 |
免费 | 30436篇 |
国内免费 | 1142篇 |
专业分类
耳鼻咽喉 | 2686篇 |
儿科学 | 3150篇 |
妇产科学 | 2843篇 |
基础医学 | 6164篇 |
口腔科学 | 5913篇 |
临床医学 | 28687篇 |
内科学 | 29193篇 |
皮肤病学 | 3555篇 |
神经病学 | 14914篇 |
特种医学 | 4558篇 |
外国民族医学 | 2篇 |
外科学 | 20731篇 |
综合类 | 455篇 |
现状与发展 | 40篇 |
一般理论 | 25篇 |
预防医学 | 15248篇 |
眼科学 | 2607篇 |
药学 | 3109篇 |
中国医学 | 33篇 |
肿瘤学 | 10453篇 |
出版年
2024年 | 753篇 |
2023年 | 5124篇 |
2022年 | 1255篇 |
2021年 | 3083篇 |
2020年 | 5541篇 |
2019年 | 2319篇 |
2018年 | 7193篇 |
2017年 | 7650篇 |
2016年 | 8282篇 |
2015年 | 8470篇 |
2014年 | 11048篇 |
2013年 | 13098篇 |
2012年 | 5350篇 |
2011年 | 5249篇 |
2010年 | 7816篇 |
2009年 | 9958篇 |
2008年 | 5125篇 |
2007年 | 4039篇 |
2006年 | 5152篇 |
2005年 | 3847篇 |
2004年 | 3107篇 |
2003年 | 2732篇 |
2002年 | 2591篇 |
2001年 | 2113篇 |
2000年 | 1354篇 |
1999年 | 1984篇 |
1998年 | 2458篇 |
1997年 | 2179篇 |
1996年 | 2203篇 |
1995年 | 1943篇 |
1994年 | 1285篇 |
1993年 | 1099篇 |
1992年 | 918篇 |
1991年 | 787篇 |
1990年 | 659篇 |
1989年 | 671篇 |
1988年 | 645篇 |
1987年 | 510篇 |
1986年 | 494篇 |
1985年 | 434篇 |
1984年 | 415篇 |
1983年 | 454篇 |
1982年 | 437篇 |
1981年 | 368篇 |
1980年 | 304篇 |
1979年 | 158篇 |
1978年 | 248篇 |
1977年 | 230篇 |
1976年 | 175篇 |
1975年 | 154篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
133.
134.
135.
136.
137.
138.
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
139.
140.
Kerstin Schmidt Johannes Hoffend Annette Altmann Ludwig G Strauss Antonia Dimitrakopoulou-Strauss Britta Engelhardt Dirk Koczan J?rg Peter Thomas J Dengler Walter Mier Michael Eisenhut Uwe Haberkorn Ralf Kinscherf 《Journal of nuclear medicine》2006,47(3):543-551
Growth of malignant tumors is dependent on sufficient blood supply. Thus, inhibition of tumor angiogenesis is emerging as a promising target in the treatment of malignancies. Human angiostatin (hANG) is one of the most potent inhibitors of endothelial cell proliferation, angiogenesis, and tumor growth in vivo. However, its mechanisms operating in vivo are not well understood. METHODS: To obtain more information about functional changes in the angiogenic process, we established Morris hepatoma (MH3924A) cell lines expressing hANG (hANG-MH3924A). The effects of hANG expression on proliferation and apoptosis of human umbilical vein endothelial cells (HUVECs) were measured in coculture experiments in vitro. To evaluate changes in tumor perfusion and blood volume, H2 15O and 68Ga-DOTA-albumin (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N',N'-tetraacetic acid) were used for PET studies in vivo. Additionally, immunohistologic quantification of vascularization, apoptosis, and proliferation as well as gene array analyses were performed. RESULTS: Our in vitro experiments demonstrate reduced proliferation and increased apoptosis in HUVECs when being cocultured with hANG-MH3924A. In support, tumor growth of hANG-MH3924A is diminished by 95% in vivo. However, tumor perfusion and blood volume are increased in hANG-MH3924A corresponding to an increased microvessel density. Furthermore, hANG-transfected tumors show changes in expression of genes related to apoptosis, stress, signal transduction, and metabolism. CONCLUSION: hANG expression leads to inhibition of tumor growth, increased apoptosis, and changes in the expression of multiple genes involved in stress reactions, signal transduction, and apoptosis, which indicates a multifactorial reaction of tumors. An enhanced microvessel density is seen as part of these reactions and is associated with increased perfusion as measured by PET. 相似文献