全文获取类型
收费全文 | 827篇 |
免费 | 52篇 |
国内免费 | 14篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 57篇 |
妇产科学 | 10篇 |
基础医学 | 114篇 |
口腔科学 | 18篇 |
临床医学 | 122篇 |
内科学 | 132篇 |
皮肤病学 | 10篇 |
神经病学 | 41篇 |
特种医学 | 191篇 |
外科学 | 40篇 |
综合类 | 35篇 |
预防医学 | 29篇 |
眼科学 | 4篇 |
药学 | 55篇 |
肿瘤学 | 30篇 |
出版年
2021年 | 3篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 22篇 |
2013年 | 20篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 18篇 |
2009年 | 24篇 |
2008年 | 13篇 |
2007年 | 30篇 |
2006年 | 22篇 |
2005年 | 22篇 |
2004年 | 14篇 |
2003年 | 22篇 |
2002年 | 10篇 |
2001年 | 18篇 |
2000年 | 13篇 |
1999年 | 25篇 |
1998年 | 44篇 |
1997年 | 52篇 |
1996年 | 40篇 |
1995年 | 41篇 |
1994年 | 24篇 |
1993年 | 27篇 |
1992年 | 18篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 28篇 |
1987年 | 27篇 |
1986年 | 22篇 |
1985年 | 19篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 19篇 |
1981年 | 14篇 |
1980年 | 22篇 |
1979年 | 6篇 |
1978年 | 12篇 |
1977年 | 24篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1969年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有893条查询结果,搜索用时 0 毫秒
51.
Multispectral analysis of magnetic resonance images 总被引:1,自引:0,他引:1
Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study. 相似文献
52.
53.
The cell-invasive adenylate cyclase toxin (CyaA) of Bordetella pertussis was shown to be highly antigenic in mice, stimulating serum anti-CyaA IgG antibody responses which were able to neutralise the cytotoxic effect of CyaA on J774.2 macrophage-like cells. The effect of co-administration to mice of the fully functional CyaA toxin or a toxin lacking adenylate cyclase enzymic activity (CyaA*) with other antigens from B. pertussis, namely pertussis toxin (PT) or pertussis toxoid (PTd), filamentous haemagglutinin (FHA) and pertactin (PRN), was investigated. CyaA* enhanced the serum IgG antibody responses to each of these antigens whereas, with CyaA, only anti-PRN antibody titres showed a modest increase. Peritoneal macrophages and spleen cells, collected at 2 weeks post-immunisation, were cultured and tested for nitric oxide (NO) and IFNgamma production, respectively, after stimulation in vitro with heat-killed B. pertussis cells or CyaA proteins. NO and IFNgamma production were higher in cells collected from mice immunised with CyaA or CyaA* in combination with a PT, FHA and PRN antigen mixture than from those taken from mice injected with antigen mixture alone, again with CyaA* acting as a better adjuvant than CyaA. The apparent enhancement of immune responses to the antigen mixture by CyaA* in particular was not paralleled by increased protection of mice against aerosol challenge with B. pertussis, but a statistically significant increase in protection was seen after intranasal challenge with B. parapertussis. 相似文献
54.
55.
三尖杉树皮粗提取物中的一个新生物碱—高三尖杉酯碱酰胺(homoharringtonamide)的结构,经质谱—质谱分析,初步建议为16。类似的酰胺类生物碱,例如三尖杉碱酰胺(cephalotaxamide,6)、11-羟基三尖杉碱酰胺(11-hydroxycephalotaxamide,9)、三尖杉酯碱酰胺(harfingtonamide,14)或异三尖杉酯碱酰胺(isoharringtonamide,15)也可能存在,后三者(9,14,15)尚未见报道。 相似文献
56.
57.
PJ Fielder SE Gargosky M Vaccarello K Wilson P Cohen F Diamond J Guevara-Aguirre AL Rosenbloom RG Rosenfeld 《Acta paediatrica (Oslo, Norway : 1992)》1993,82(S389):40-43
Six adult patients with growth hormone receptor deficiency (GHRD) (2 men, 4 women) with an identical defect in the growth hormone receptor (GHR) gene, were treated with recombinant human insulin-like growth factor I (IGF-I), 40 μgikg S.C. twice daily, for 7 days. Serum concentrations of IGF peptide and IGF binding protein-3 (IGFBP-3) were measured by specific radioimmunoassays; serum IGFBPs were also measured by Western ligand blotting. The size distribution of both IGF-I and IGF-II was measured in serum following size-exclusion fast-performance liquid chromatography. IGF-I treatment resulted in a normalization of serum IGF-I levels on days 1–7 of treatment and a decrease in serum IGF-II levels. The fall in IGF-II levels and the simultaneous rise in IGF-I levels, however, resulted in an unchanged total serum IGF level. The low IGFBP-3 values did not significantly change during treatment, whereas there was a slight increase in IGFBP-2 levels. Preliminary analysis of size-fractionated sera suggested an increase in IGF-I levels in the 40 and 150 kDa regions at the expense of IGF-II levels. The results suggest that despite the failure of IGF-I treatment to increase IGFBPs significantly, serum IGFBP concentrations were sufficient to maintain normal levels of IGF-I. 0 Laron syndrome, growth hormone receptor deficiency, insulin-like growth factors, insulin-like growth factor binding protein 相似文献
58.
59.
60.
Blood loss and replacement in total hip arthroplasty: a multicenter study. The Preoperative Autologous Blood Donation Study Group 总被引:1,自引:0,他引:1
To determine blood loss, the number of transfusions, and the hemoglobin levels achieved in patients via transfusion in the course of total hip arthroplasty, 324 patient records from 1987 through 1989 were reviewed at three university and three community hospitals. Calculated blood loss was 3.2 +/- 1.3 units in primary procedures and 4.0 +/- 2.1 units in revision procedures (mean +/- SD). Of 777 red cell units transfused, 455 (59%) were autologous units. Transfused patients received 2.0 +/- 1.8 units for primary procedures and 2.9 +/- 2.3 units for revision procedures (mean +/- SD). The maximum number of units given to 95 percent of the transfused patients was 4 for primary procedures and 6 for revision procedures. The mean postoperative hemoglobin level after all transfusions was 103 to 110 g per L, regardless of patient age group of physical status, autologous donor status, or hospital. No difference in length of hospital stay was observed for patients less than 65 years old with hemoglobin concentrations of 80 to 139 g per L at discharge. 相似文献