全文获取类型
收费全文 | 5896篇 |
免费 | 623篇 |
国内免费 | 41篇 |
专业分类
耳鼻咽喉 | 98篇 |
儿科学 | 97篇 |
妇产科学 | 146篇 |
基础医学 | 1031篇 |
口腔科学 | 72篇 |
临床医学 | 627篇 |
内科学 | 1251篇 |
皮肤病学 | 93篇 |
神经病学 | 498篇 |
特种医学 | 226篇 |
外科学 | 762篇 |
综合类 | 139篇 |
一般理论 | 7篇 |
预防医学 | 625篇 |
眼科学 | 155篇 |
药学 | 452篇 |
中国医学 | 23篇 |
肿瘤学 | 258篇 |
出版年
2021年 | 75篇 |
2020年 | 51篇 |
2019年 | 64篇 |
2018年 | 84篇 |
2017年 | 67篇 |
2016年 | 71篇 |
2015年 | 87篇 |
2014年 | 134篇 |
2013年 | 202篇 |
2012年 | 251篇 |
2011年 | 253篇 |
2010年 | 149篇 |
2009年 | 141篇 |
2008年 | 220篇 |
2007年 | 237篇 |
2006年 | 246篇 |
2005年 | 219篇 |
2004年 | 210篇 |
2003年 | 178篇 |
2002年 | 208篇 |
2001年 | 164篇 |
2000年 | 168篇 |
1999年 | 133篇 |
1998年 | 86篇 |
1997年 | 72篇 |
1996年 | 68篇 |
1995年 | 66篇 |
1994年 | 62篇 |
1993年 | 56篇 |
1992年 | 130篇 |
1991年 | 136篇 |
1990年 | 115篇 |
1989年 | 136篇 |
1988年 | 129篇 |
1987年 | 132篇 |
1986年 | 131篇 |
1985年 | 141篇 |
1984年 | 112篇 |
1983年 | 94篇 |
1982年 | 74篇 |
1981年 | 53篇 |
1980年 | 70篇 |
1979年 | 102篇 |
1978年 | 76篇 |
1977年 | 50篇 |
1975年 | 50篇 |
1974年 | 74篇 |
1973年 | 57篇 |
1972年 | 72篇 |
1971年 | 48篇 |
排序方式: 共有6560条查询结果,搜索用时 15 毫秒
1.
Relation between energy expenditure and body composition in man: specific energy expenditure in vivo of fat and fat-free tissue 总被引:2,自引:0,他引:2
L Garby J S Garrow B J?rgensen O Lammert K Madsen P S?rensen J Webster 《European journal of clinical nutrition》1988,42(4):301-305
The relationship between energy expenditure and body composition, in terms of fat and fat-free masses, has previously been described by a variety of predictive regression equations with parameters devoid of physiological content. We present here results obtained by calculating the specific energy expenditure, ie, the energy expenditure per unit of mass, of fat and fat-free tissue on the basis of measurements of the total energy expenditure (EE), the masses of fat (FM), and fat-free (FFM) tissue using the following simple model: EE = k1.FM + k2.FFM where k1 and k2 are the specific energy expenditures of fat and fat-free tissue, respectively. The results of observations on 104 women at rest yielded values for k1 and k2 of 0.31 and 1.35 watts/kg of fat and fat-free mass, respectively, with standard errors of estimate of 0.074 and 0.052 watts/kg, respectively. Analysis of several series of measurements, from other sources and on smaller samples of subjects, yielded similar values at rest but with larger standard errors of estimate. Data from subjects performing varying amounts of work in 24-h measurements showed, as expected, larger values for both tissues. The results explain to a very large extent the well-established relation between resting metabolic rate and body weight, ie, a linear relation with a non-zero intercept. The results also offer a clear-cut explanation for the well known difference in energy expenditure between men and women with the same body weight. 相似文献
2.
3.
Myelinated fiber regeneration after crush injury is retarded in sciatic nerves of aging mice 总被引:2,自引:0,他引:2
To compare nerve regeneration in young adult and aging mice, the right sciatic nerves of 6- and 24-month-old mice were crushed at the sciatic notch. Two weeks later, both groups of mice were perfused with an aldehyde solution, and, after additional fixation, the sciatic nerves were processed so that the transverse sections of each nerve subsequently studied by light and electron microscopy included the entire posterior tibial fascicle 5 mm distal to the crush site. The same level was sectioned in unoperated contralateral nerves; these nerves served as controls. Electron micrographs and the Bioquant Image Analysis System IV were used to measure areas of posterior tibial fascicles and count the number of myelinated axons, the number of unmyelinated axons, and their frequency in Schwann cell units. In aging mice, the total number of regenerating myelinated axons was significantly reduced, but totals of regenerating unmyelinated axons in aging and young adults did not differ significantly. In aging mice, the frequency of Schwann cells that contained a single unmyelinated axon was greater, suggesting that before myelination began, Schwann cell ensheathment of axons also was slowed. After axotomy by a crush injury, the area of the posterior tibial fascicle was less than that in young adults and the distal disintegration of myelin sheath remnants also appeared to be retarded. The results indicate that responses of neurons, axons, and Schwann cells could be important in slowing the regeneration of myelinated fibers found in sciatic nerves from aging mice. 相似文献
4.
Stanley J. Bigos John Holland Carole Holland John S. Webster Michele Battie Judith A. Malmgren 《The spine journal》2009,9(2):147-168
Background contextBack problems (BPs), with their cost and disability, are a substantial burden for individuals, employers, and society.PurposeThis systematic review of controlled trials evaluates the effectiveness of interventions to prevent BP episodes in working age adults.Data sourcesWe searched MEDLINE/EMBASE through May 2007, and COCHRANE/Trials Registry through August 22, 2008 using search terms of back pain, back injuries or sciatica, linked to prevention, control, workplace interventions, or ergonomics and searched article bibliographies.Study selectionFor systematic review inclusion, articles had to describe prospective controlled trials of interventions to prevent BPs in working-age adults, with intervention assignment either to individual participants or preexisting groups. Of 185 articles identified as potentially relevant, 20 trials (11%) met inclusion criteria.Data extractionResearchers extracted relevant information from controlled trials and graded methodological quality. Because of heterogeneity of trials, meta-analysis was not performed.ResultsOnly exercise was found effective for preventing self-reported BPs in seven of eight trials (effect size 0.39 to >0.69). Other interventions were not found to reduce either incidence or severity of BP episodes compared with controls. Negative trials included five trials of education, four of lumbar supports, two of shoe inserts, and four of reduced lifting programs.ConclusionsTwenty high-quality controlled trials found strong, consistent evidence to guide prevention of BP episodes in working-age adults. Trials found exercise interventions effective and other interventions not effective, including stress management, shoe inserts, back supports, ergonomic/back education, and reduced lifting programs. The varied successful exercise approaches suggest possible benefits beyond their intended physiologic goals.Level of evidenceSystematic review Level I evidence. 相似文献
5.
Varicose vein surgery using a pneumatic tourniquet: reduced blood loss and improved cosmesis. 总被引:5,自引:5,他引:0
下载免费PDF全文
![点击此处可从《Annals of the Royal College of Surgeons of England》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J. F. Thompson G. T. Royle P. A. Farrands A. Najmaldin P. C. Clifford J. H. Webster 《Annals of the Royal College of Surgeons of England》1990,72(2):119-122
A prospective controlled randomised study has been performed of 100 consecutive patients undergoing varicose vein surgery. One group underwent saphenofemoral flush ligation and multiple lower leg avulsions with the leg exsanguinated with a Rhys-Davies cuff, and ischaemia maintained with a pneumatic tourniquet. The other group underwent identical surgery but with a 30 degree head down tilt only. Blood loss was significantly less (13.5 +/- 12 ml vs 133 +/- 78 ml; P less than 0.01) and postoperative cosmesis was significantly improved in patients in the tourniquet group. Operating time was similar (27 +/- 11 min vs 30 +/- 13 min) in the two groups. 相似文献
6.
Duplication of the urethra with an accessory phallic urethra in females is a rare anomaly usually discovered early in life because of associated genitourinary anomalies. We report on a thirty-three-year-old female with this anomaly who presented with double urinary stream and recurrent urinary tract infections. The nature of this anomaly, its diagnosis, and management are reviewed. 相似文献
7.
The effect of benserazide on the peripheral and central distribution and metabolism of levodopa after acute and chronic administration in the rat.
下载免费PDF全文
![点击此处可从《British journal of pharmacology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1. The effects of levodopa alone (50 mg kg-1) and levodopa (10 mg kg-1) plus benserazide (50 mg kg-1) were tested on the levels of dopa, dopamine, 3-methoxytyrosine (3-MT), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), measured by h.p.l.c. with electrochemical detection, in samples of plasma, CSF, urine, striatum and hypothalamus of rats taken 30 min after injection. Levodopa plus benserazide produced significantly higher levels of dopa in plasma and brain than levodopa alone and reduced the peripheral synthesis and metabolism of dopamine. 2. When given chronically over 6 weeks the advantages of adding benserazide (50 mg kg-1 day-1) to levodopa (40 mg kg-1 day-1) were less marked and although more dopamine was present in the striatum than with levodopa given alone (200 mg kg-1 day-1) there was no evidence of any increase in its metabolites (HVA and DOPAC) and therefore of its turnover and utilisation. 3. The most striking effect of chronic treatment with levodopa plus benserazide was the appearance of large quantities of 3-MT in plasma, CSF and brain. 4. When levodopa alone, or levodopa plus benserazide, was given as an acute challenge to animals receiving the same treatment chronically, it was found that levodopa alone still produced increases in striatal dopamine, DOPAC and HVA in those animals dosed chronically on levodopa, but it was less effective in this respect when given with benserazide to the animals dosed with levodopa plus benserazide.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
8.
Xian ZH Zhang SH Cong WM Wu WQ Wu MC 《第二军医大学学报》2005,26(11):1320-1320
BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most prevalent fatal cancers in the world. Despite advances in early diagnosis and improvements in surgical techniques, the survival of patients with HCC even after resection is poor because of the high incidence of recurrences. Therefore, the identification of prognostic factors may be helpful in the development of new treatment protocols. AIMS: To investigate HER-2/neu status in HCC by immunohistochemistry (IHC) and fluorescence in situ hybridisation (FISH), and to explore the possibility of using trastuzumab in the treatment of HCC. METH ODS: Eight hundred and sixty eight surgical samples from patients with primary HCC were examined for their HER-2/neu status. IHC for HER-2/neu was performed with the HercepTest kit; FISH analysis was performed with the PathVysion HER-2 DNA probe kit. The correlations between HER-2/neu overexpression and clinicopathological characteristics were analysed statistically. RESULTS: HER-2/neu overexpression was detected in 21 (2.42%) of the 868 primary HCCs. Only one specimen showed HER-2/neu gene amplification by FISH. No significant associations were found between HER-2/neu overexpression and the clinicopathological parameters. CONCLUSIONS: There is a low frequency of HER-2/neu overexpression/amplification in HCC. There appears to be no role for HER-2/neu as a prognostic marker and no benefit of anti-HER-2/neu trastuzumab treatment in patients with HCC. 相似文献
9.
10.