首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   12268篇
  免费   1023篇
  国内免费   16篇
耳鼻咽喉   106篇
儿科学   501篇
妇产科学   386篇
基础医学   1875篇
口腔科学   348篇
临床医学   1298篇
内科学   2494篇
皮肤病学   134篇
神经病学   1302篇
特种医学   641篇
外科学   1228篇
综合类   197篇
一般理论   7篇
预防医学   1102篇
眼科学   195篇
药学   826篇
  1篇
中国医学   19篇
肿瘤学   647篇
  2021年   159篇
  2020年   121篇
  2019年   184篇
  2018年   216篇
  2017年   194篇
  2016年   210篇
  2015年   249篇
  2014年   313篇
  2013年   458篇
  2012年   605篇
  2011年   715篇
  2010年   358篇
  2009年   359篇
  2008年   591篇
  2007年   539篇
  2006年   554篇
  2005年   523篇
  2004年   497篇
  2003年   455篇
  2002年   418篇
  2001年   429篇
  2000年   412篇
  1999年   402篇
  1998年   174篇
  1997年   152篇
  1996年   132篇
  1995年   147篇
  1994年   160篇
  1993年   124篇
  1992年   265篇
  1991年   280篇
  1990年   224篇
  1989年   243篇
  1988年   230篇
  1987年   183篇
  1986年   174篇
  1985年   173篇
  1984年   143篇
  1983年   119篇
  1982年   67篇
  1981年   91篇
  1980年   62篇
  1979年   90篇
  1978年   76篇
  1977年   88篇
  1976年   65篇
  1975年   77篇
  1974年   90篇
  1973年   61篇
  1971年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Dural sinus thrombosis: study using intermediate field strength MR imaging   总被引:1,自引:0,他引:1  
The magnetic resonance (MR) images of six patients with thrombosis of a dural sinus were reviewed. The diagnosis had been verified by computed tomographic scans in three patients and arteriograms in two; in the sixth patient, only MR imaging was used to confirm the clinical syndrome. In all patients, high-intensity signal was seen from the thrombus within the affected dural sinus on all echoes. This persistent signal intensity allowed intravascular clot to be distinguished from normal causes of increased signal such as flow-related enhancement (entry phenomenon) and even-echo rephasing. MR imaging demonstrated the cause of the thrombosis in three patients: two were secondary to adjacent tumors, and one was secondary to unsuspected mastoiditis. Complications such as infarction were also demonstrated. Using MR imaging, one can easily and safely diagnose thrombosis of a dural sinus. MR should be the imaging method of choice in patients suspected of having thrombosis of a dural sinus.  相似文献   
32.
33.
Exposure of ZR-75-1 human breast cancer cells for 48 h to human recombinant interferon alpha (IFN alpha) resulted in increased expression of oestrogen receptors as measured in a whole cell binding assay. This effect was inversely proportional to dose being significant following treatment with 10-100 IU IFN ml-1 and was only observed at a low initial cell plating density. The extent of the increase in oestrogen receptor levels ranged from 1.2- to 7.2-fold following treatment with 10 IU IFN ml-1. No increase in progesterone receptor expression was observed under the same experimental conditions. Concentrations of IFN which increased oestrogen receptor levels had no effect on cell proliferation. IFN (500 IU ml-1) inhibited cell proliferation and the combination of this treatment with tamoxifen (2 microM) had a greater anti-proliferative effect than either drug alone although there was no evidence of synergism. However, a 5-day pretreatment of cells with IFN (10 IU ml-1) markedly sensitised them to the growth-inhibiting effect of a subsequent 6-day exposure to tamoxifen.  相似文献   
34.
35.
Results are presented of a Phase III international multicentre trial to study the effect of a new low-dose oral contraceptive (OC) containing 20 micrograms ethinylestradiol and 150 micrograms desogestrel (Mercilon) regarding efficacy, cycle control, blood pressure, and acceptability. Altogether 1,684 women from 12 European countries were included in the study. Four pregnancies occurred, 3 of them patient failures, one tablet failure. The overall Pearl Index was 0.20. The frequency of irregular bleeding was comparable to that recorded with other commonly used low-dose OCs. No serious side effects occurred. The incidence of the most frequently reported subjective side effects--headache, nausea and breast tension--was already low after the first cycle of treatment and decreased to below pretreatment levels with continued use. There was a small increase in mean body weight, which was confined essentially to young women. The preparation did not affect the mean systolic or diastolic blood pressure. This new preparation has thus proved to be an effective, safe and well-accepted ultra low-dose oral contraceptive.  相似文献   
36.
To obtain more insight into the effect of moderate alcohol intake on vitamin B-6 status indicators, we studied the associations of alcohol intake (unadjusted and adjusted for intake of vitamin B-6 and protein) with the erythrocyte aspartate aminotransferase activation coefficient (EAST-AC) and plasma pyridoxal 5'-phosphate (PLP) level. Data obtained from men (n = 224) and women (n = 217) aged 65-79 (nationwide sample in the Netherlands) were used for this purpose. Although alcohol intake (a maximum of 21% of the energy came from alcohol) tended to be positively associated with PLP, this association never reached statistical significance (p greater than or equal to 0.05). EAST-AC was inversely associated with alcohol intake, whether or not it was adjusted for vitamin B-6 and protein intake. Similar results were found for the total EAST activity (after adding PLP) or apoenzyme activity; the basal EAST activity (before adding PLP) or holoenzyme activity was not associated with the alcohol intake. These results indicate that caution is needed in the interpretation of the specificity of EAST-AC (i.e., the degree to which EAST-AC is unaffected by other factors) as an indicator of vitamin B-6 intake.  相似文献   
37.
38.
39.
40.
Evolution of white matter lesions in neurofibromatosis type 1: MR findings.   总被引:1,自引:0,他引:1  
To characterize further the evolution of white matter lesions in neurofibromatosis type 1, we reviewed 68 MR images in 43 patients (age, 1-31 years), including 25 follow-up studies (mean interval, 27 months). Lesion number, location, morphology, signal characteristics, and contrast enhancement were assessed. Lesion characteristics and changes thereof were correlated with the patients' ages. Thirty-four patients (79%) had white matter lesions. These lesions were hyperintense on T2-weighted images, were isointense on T1-weighted images, and showed no mass effect or contrast enhancement in 31 patients; in three patients, T1-prolongation was observed (one with significant mass effect). None of the lesions evolved into a glioma. The most common locations were the cerebellum (49%), brainstem (22%), and internal capsule (19%). Nineteen patients had white matter lesions and follow-up studies. Lesions decreased in size or number in seven patients (average age, 13 years), showed no change in three (average age, 12 years), increased in size or number in four (average age, 5 years), and showed a mixed pattern (increased/decreased size/number) in four (average age, 7 years). White matter lesions in neurofibromatosis type 1 frequently increase in size or number early in childhood; this did not indicate neoplasia in our study. The lesions tend to resolve with increasing age. Lesion progression in a child more than 10 years old warrants close follow-up to rule out a neoplasm.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号