全文获取类型
收费全文 | 3753篇 |
免费 | 282篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 53篇 |
儿科学 | 159篇 |
妇产科学 | 63篇 |
基础医学 | 405篇 |
口腔科学 | 87篇 |
临床医学 | 525篇 |
内科学 | 634篇 |
皮肤病学 | 27篇 |
神经病学 | 171篇 |
特种医学 | 318篇 |
外国民族医学 | 1篇 |
外科学 | 576篇 |
综合类 | 94篇 |
一般理论 | 2篇 |
预防医学 | 496篇 |
眼科学 | 52篇 |
药学 | 252篇 |
1篇 | |
肿瘤学 | 132篇 |
出版年
2021年 | 34篇 |
2020年 | 27篇 |
2019年 | 49篇 |
2018年 | 61篇 |
2017年 | 40篇 |
2016年 | 52篇 |
2015年 | 59篇 |
2014年 | 80篇 |
2013年 | 112篇 |
2012年 | 147篇 |
2011年 | 150篇 |
2010年 | 133篇 |
2009年 | 110篇 |
2008年 | 145篇 |
2007年 | 133篇 |
2006年 | 140篇 |
2005年 | 141篇 |
2004年 | 154篇 |
2003年 | 122篇 |
2002年 | 120篇 |
2001年 | 101篇 |
2000年 | 97篇 |
1999年 | 88篇 |
1998年 | 107篇 |
1997年 | 106篇 |
1996年 | 106篇 |
1995年 | 77篇 |
1994年 | 65篇 |
1993年 | 65篇 |
1992年 | 85篇 |
1991年 | 75篇 |
1990年 | 64篇 |
1989年 | 70篇 |
1988年 | 78篇 |
1987年 | 75篇 |
1986年 | 65篇 |
1985年 | 64篇 |
1984年 | 53篇 |
1983年 | 46篇 |
1982年 | 37篇 |
1981年 | 32篇 |
1980年 | 32篇 |
1979年 | 42篇 |
1977年 | 27篇 |
1976年 | 30篇 |
1975年 | 31篇 |
1974年 | 36篇 |
1973年 | 29篇 |
1972年 | 30篇 |
1966年 | 24篇 |
排序方式: 共有4048条查询结果,搜索用时 15 毫秒
1.
PJ Commerford 《Cardiovascular journal of Africa》2015,26(4):151-Aug;26(4):151
2.
We have previously reported the time trends, design and interventions in randomised controlled trials (RCTs) in cystic fibrosis (CF) from 1961 through 1997 [Cheng K, Smyth RL, Motley J, O'Hea U, Ashby D, Randomised controlled trials in cystic fibrosis (1966-1997) categorized by time, design, and intervention. Pediatr Pulmonol 2000, 29:1-7.]. We maintain an ongoing register of all RCTs and controlled clinical trials (CCTs) in CF and have noted that in the five years since 1997 there has been a 48% increase in published trials. We aimed to assess whether this increase has been associated with an improvement in design quality. All RCTs and CCTs from 1961-2002 were assessed. Two epochs were then compared, 1961-1997 and 1998-2002. For each trial we recorded the design, participant numbers and the intervention studied. 261 trials in 1998-2002 were compared with 544 trials in 1961-1997. Comparing the two epochs a similar proportion of trials were parallel, double-blind and placebo controlled; also the median number of participants was similar. In the later epoch 25% of trials were multicentre, compared with 11% previously. Whilst this recent increase in clinical trials in CF is welcome, this has not been associated with improvements in quality. The trend for an increasing proportion of trials to be multicentre is encouraging. There are however, still deficiencies in the design of clinical trials in CF. 相似文献
3.
Andrew M Briggs John D Wark Susan Kantor Rayson Teh Alison M Greig Nicola L Fazzalari Kim L Bennell 《Journal of clinical densitometry》2005,8(3):314-319
Analysis of apparent bone mineral density (BMD) in the lumbar spine is commonly based on anteroposterior (AP) scanning using dual-energy X-ray absorptiometry (DXA). Although not widely used, clinically important information can also be derived from lateral scanning. Vertebral bone density, and therefore strength, can may vary in different subregions of the vertebral body. Therefore, subregional BMD measurements might be informative about fracture risk. However, the intrarater and interrater precision of in vivo subregional BMD assessments from lateral DXA remains unknown. Ten normal, young (mean: 24 yr) and 10 older (mean: 63 yr) individuals with low BMD were scanned on one occasion using an AP/lateral sequence. Each lateral scan was reanalyzed six times at L2 by three raters to determine the intrarater and interrater precision in selecting seven regions of interest (subregions). Precision was expressed using percentage coefficients of variation (% CV) and intraclass correlation coefficients (ICC). Intrarater precision ranged from ICC(1,1) 0.971 to 0.996 (% CV: 0.50-3.68) for the young cohort and ICC(1,1) 0.934 to 0.993 (% CV: 1.46-5.30) for the older cohort. Interrater precision ranged from ICC(2,1) 0.804 to 0.915 (% CV: 1.11-2.35) for the young cohort and ICC(2,1) 0.912 to 0.984 (% CV: 1.85-4.32) for the older cohort. Scanning a subgroup of participants twice with repositioning was used to assess short-term in vivo precision. At L2, short-term in vivo precision ranged from ICC(1,1) 0.867 to 0.962 (% CV: 3.38-9.61), at L3 from ICC(1,1) 0.961 to 0.988 (% CV: 2.02-5.57) and using an L2/L3 combination from ICC(1,1) 0.942 to 0.980 (% CV: 2.04-4.61). This study demonstrated moderate to high precision for subregional analysis of apparent BMD in the lumbar spine using lateral DXA in vivo. 相似文献
4.
J L Woolley G R Barker W K Jacobsen G A Gingrich S C Stewart B A Briggs R D Martin R A Melashenko 《Critical care medicine》1988,16(1):48-51
The ability of the calcium entry blocker verapamil to ameliorate the effects of renal ischemia was studied in ten sheep. Postanesthesia, bilateral cutaneous ureterostomies were placed in each sheep to facilitate urine collection and analysis. Both kidneys were made ischemic for one hour by occluding each renal artery. However, immediately before occlusion of the right renal artery, 0.05 mg/kg of verapamil was injected into the artery. Comparison of urinary creatinine excretion and urine volume for 72 h after reversal of ischemia demonstrated that those kidneys pretreated with verapamil had greater functional preservation (p less than .05). In this study, verapamil appeared to provide protection against renal damage after an ischemic insult. 相似文献
5.
6.
Hans Bosma Martin PJ van Boxtel Gertrudis IJM Kempen Jacques ThM van Eijk Jelle Jolles 《BMC public health》2007,7(1):179
Background
The aims of this study were to examine the extent to which higher intellectual abilities protect higher socio-economic groups from functional decline and to examine whether the contribution of intellectual abilities is independent of childhood deprivation and low birth weight and other socio-economic and developmental factors in early life. 相似文献7.
8.
9.
10.
Specific MR imaging of human lymphocytes by monoclonal antibody-guided dextran-magnetite particles. 总被引:4,自引:0,他引:4
J W Bulte Y Hoekstra R L Kamman R L Magin A G Webb R W Briggs K G Go C E Hulstaert S Miltenyi T H The 《Magnetic resonance in medicine》1992,25(1):148-157
Human lymphocytes were labeled with biotinylated anti-lymphocyte-directed monoclonal antibodies, to which streptavidin and subsequently biotinylated dextran-magnetite particles were coupled. This labeling resulted in a strong and selective negative contrast enhancement of lymphocyte suspensions at 2.0 T, caused predominantly by the specific increase of R2 with a small but significant specific increase of R1. The R1 was found to decrease with increasing field strength. The immunolabeling procedure described here may be used for the selective signal depletion of target cells in MR imaging. 相似文献