全文获取类型
收费全文 | 2019篇 |
免费 | 130篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 177篇 |
妇产科学 | 26篇 |
基础医学 | 208篇 |
口腔科学 | 51篇 |
临床医学 | 184篇 |
内科学 | 405篇 |
皮肤病学 | 27篇 |
神经病学 | 41篇 |
特种医学 | 483篇 |
外科学 | 280篇 |
综合类 | 35篇 |
预防医学 | 60篇 |
眼科学 | 13篇 |
药学 | 65篇 |
中国医学 | 4篇 |
肿瘤学 | 109篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 21篇 |
2017年 | 11篇 |
2016年 | 26篇 |
2015年 | 34篇 |
2014年 | 41篇 |
2013年 | 73篇 |
2012年 | 47篇 |
2011年 | 45篇 |
2010年 | 90篇 |
2009年 | 72篇 |
2008年 | 52篇 |
2007年 | 51篇 |
2006年 | 48篇 |
2005年 | 32篇 |
2004年 | 27篇 |
2003年 | 28篇 |
2002年 | 31篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 35篇 |
1998年 | 135篇 |
1997年 | 120篇 |
1996年 | 127篇 |
1995年 | 92篇 |
1994年 | 77篇 |
1993年 | 89篇 |
1992年 | 28篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 67篇 |
1988年 | 52篇 |
1987年 | 54篇 |
1986年 | 49篇 |
1985年 | 56篇 |
1984年 | 28篇 |
1983年 | 34篇 |
1982年 | 45篇 |
1981年 | 22篇 |
1980年 | 37篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 21篇 |
1976年 | 26篇 |
1975年 | 27篇 |
1971年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有2171条查询结果,搜索用时 0 毫秒
1.
2.
3.
L F Hiratzka C L Eastham J G Carter J R Moyers D R Elliott D B Doty C B Wright M L Marcus 《The Annals of thoracic surgery》1988,45(5):474-481
In normal coronary arteries, reactive hyperemic responses to a 20-second occlusion, an index of coronary reserve, usually demonstrate a peak-to-resting flow velocity ratio of 4:1 or more. Most intraoperative studies that have assessed reactive hyperemic responses in bypassed vessels have reported peak-to-resting flow velocity ratios of 2:1 or less following a 20-second occlusion. These decreased reactive hyperemic responses could be due to coronary vasodilatation after cardiopulmonary bypass or to an inadequate physiological result of the surgical procedure. In 14 patients with angiographically normal coronary arteries, the peak-to-resting flow velocity ratio following a 20-second coronary occlusion decreased significantly (p less than 0.05) from 4.4 +/- 0.2 (mean +/- standard error) before bypass to 3.0 +/- 0.3 after bypass. In a similar dog model, the peak-to-resting flow velocity ratio decreased by 36 to 52% during the first hour following one hour of cardiopulmonary bypass and cardioplegia. During the same period, left ventricular perfusion increased 21 to 30%, mean arterial pressure and coronary vascular resistance decreased, and myocardial oxygen consumption was unchanged. In a second group of dogs studied for the effects of duration (200 to 240 minutes) of anesthesia and thoracotomy alone, peak-to-resting flow velocity ratio was significantly lower. These clinical and experimental studies suggest that major coronary vasodilatation occurs early following cardiopulmonary bypass and cold cardioplegia, and may contribute to the blunted coronary reactive hyperemic responses reported during this time. Consequently, an intraoperative peak-to-resting flow velocity ratio of 3:1 for bypassed coronary arteries may represent an excellent physiological result. 相似文献
4.
We report an adult female with a rare giant choledochal cyst. The patient presented following a normal pregnancy with the classical triad of an abdominal mass associated with jaundice and right upper quadrant abdominal pain. The cyst was excised using an intramural technique and biliary reconstruction achieved with a Roux-en-Y hepaticojejunostomy. Our patient has remained well with no evidence of malignancy over a 12 year review period. The aetiology and current management of this condition are discussed. 相似文献
5.
6.
M. Stephen Murphy M.R.C.P. David Gardner-Medwin M.D. M.R.C.P. Edmund J. Eastham M.R.C.P. 《The American journal of gastroenterology》1989,84(10):1329-1330
Achalasia of the cardia, a disorder associated with degenerative loss of esophageal myenteric ganglion cells, is reported in association with a recently described progressive neurological disorder, "early onset cerebellar ataxia with retained reflexes." This form of cerebellar ataxia is thought to be inherited as an autosomal recessive disorder. The occurrence of these two very rare neurodegenerative disorders in a single individual is of interest because of the potential genetic and pathogenetic implications of the association. 相似文献
7.
Na+ dependence of in vitro pancreatic amylase release 总被引:1,自引:0,他引:1
8.
Determination of optimal cryoprotectants and procedures for their addition and removal from human spermatozoa 总被引:9,自引:7,他引:9
The objective was to test the hypothesis that the optimal cryoprotective
agent for cryopreservation of human spermatozoa would be a solute for which
cells have the highest plasma membrane permeability, resulting in the least
amount of volume excursion during its addition and removal. To test this
hypothesis, theoretical simulations were performed using membrane
permeability coefficients to predict optimal procedures for the addition
and removal of a cryoprotectant. Simulations were performed using data from
four different cryoprotectants: (i) glycerol, (ii) dimethyl sulphoxide,
(iii) propylene glycol and (iv) ethylene glycol. Thermodynamic formulations
were applied to determine approaches for the addition and removal of 1 M
and 2 M final concentrations of cryoprotectant, allowing the spermatozoa to
maintain a cell volume within their osmotic tolerance limits. Based on
these data, ethylene glycol was predicted to be optimal for minimizing
volume excursions among the solutes evaluated. These predictions were then
experimentally tested using glycerol as the control cryoprotectant and
ethylene glycol as the experimental cryoprotectant. The results indicate
that there was a higher (P < 0.05) recovery of motile spermatozoa after
cryopreservation when using 1 M ethylene glycol than with 1 M glycerol,
supporting the hypothesis that use of the cryoprotectant for which the cell
has the highest permeability will result in higher cell survival.
相似文献
9.
Comparison of isolation of Haemophilus vaginalis (Corynebacterium vaginale) from peptone-starch-dextrose agar and Columbia colistin-nalidoxic acid agar. 下载免费PDF全文
A total of 447 cervical or vaginal specimens were inoculated in parallel onto peptone-starch-dextrose (PSD) and Columbia colistin (10 mg/ml)-nalidixic acid (15 mug/ml) (CNA) agar and were incubated for 48 h at 35 degrees C in an atmosphere with 2 to 10% CO2. One hundred (22.4%) of the cultures were positive for Haemophilus vaginalis. Forty-eight of the isolates were recovered from both PSD and Columbia CNA agar, five from PSD only, and 47 from Columbia CNA agar only (P less than 0.001). On Columbia CNA agar, 76 of the isolates were detected after 24 h of incubation, and the remainder were detected within 4 days of incubation. 相似文献
10.