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   7272篇
  免费   292篇
  国内免费   35篇
耳鼻咽喉   26篇
儿科学   111篇
妇产科学   91篇
基础医学   746篇
口腔科学   156篇
临床医学   485篇
内科学   1846篇
皮肤病学   77篇
神经病学   584篇
特种医学   293篇
外科学   1282篇
综合类   37篇
预防医学   151篇
眼科学   455篇
药学   416篇
中国医学   12篇
肿瘤学   831篇
  2022年   52篇
  2021年   109篇
  2020年   55篇
  2019年   94篇
  2018年   99篇
  2017年   96篇
  2016年   148篇
  2015年   122篇
  2014年   176篇
  2013年   182篇
  2012年   317篇
  2011年   307篇
  2010年   191篇
  2009年   157篇
  2008年   283篇
  2007年   289篇
  2006年   320篇
  2005年   295篇
  2004年   313篇
  2003年   307篇
  2002年   331篇
  2001年   300篇
  2000年   322篇
  1999年   267篇
  1998年   86篇
  1997年   79篇
  1996年   65篇
  1995年   58篇
  1994年   62篇
  1993年   50篇
  1992年   192篇
  1991年   167篇
  1990年   150篇
  1989年   165篇
  1988年   153篇
  1987年   99篇
  1986年   135篇
  1985年   123篇
  1984年   78篇
  1983年   75篇
  1979年   73篇
  1978年   43篇
  1977年   46篇
  1974年   47篇
  1973年   49篇
  1972年   45篇
  1971年   58篇
  1970年   38篇
  1969年   41篇
  1968年   44篇
排序方式: 共有7599条查询结果,搜索用时 8 毫秒
1.
The phosphodiesterase-5 (PDE-5) inhibitor, sildenafil, has been reported to produce sustained pulmonary vasodilatation in patients with pulmonary hypertension (PH). Recently, vardenafil, a more potent and selective PDE-5 inhibitor than sildenafil, has been approved for the treatment of erectile dysfunction. However, the long-term effects of oral vardenafil in patients with PH are unknown. We studied five consecutive patients with PH; one with primary pulmonary hypertension, two with chronic pulmonary thromboembolism, one with Eisenmenger syndrome (ventricular septal defect) and one with secondary pulmonary hypertension after a ventricular septal defect closure operation. In an acute hemodynamic trial, vardenafil (5 mg) significantly decreased both the pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) with an increase in cardiac output. In a chronic hemodynamic trial, the maintenance dose of vardenafil (10 to 15 mg) for 3 months significantly decreased the PVR, but not the SVR, with a 20.7% reduction of the PVR/ SVR ratio. Plasma brain natriuretic peptide (BNP) levels were also significantly decreased after 3 months. This pilot study demonstrates that long-term oral vardenafil therapy may be a safe and effective treatment for patients with PH.  相似文献   
2.
A case of cystadenocarcinoma of the liver is reported. The patient was a 73-year-old woman in whom a tumor was detected in the lateral segment of the liver during a health examination. Ultrasonograms and computed tomograms showed a multilocular cystic mass. Magnetic resonance imaging (MRI) showed a multilocular lowintensity mass, including a high-intensity portion and a portal branch compressed by the tumor. MRI with gadolinium showed an enhanced cyst wall. The cystic part of the tumor became smaller and the solid part became larger over a 1-month period, indicating that the tumor was malignant. Subsegmentectomy (S3) was performed and cystadenocarcinoma with cystadenoma was diagnosed by histopathological examination. Identification of changes in the appearance of a tumor should be helpful for the differential diagnosis of cystadenoma and cystadenocarcinoma.  相似文献   
3.
In the focal infarction model of the rat middle cerebral artery (MCA), the thalamus of the occluded side becomes gradually atrophic, mainly because of retrograde degeneration. We determined whether basic fibroblast growth factor (bFGF) administered intracisternally could prevent this thalamic atrophy. We occluded the left MCA through a small cranial opening, and animals were then divided into two groups. One group received intracisternal injections of recombinant bFGF (1 microgram dissolved in 0.1 ml of saline with 2% rat serum) starting 1 day after occlusion and repeated once a week to a total dose of 4 micrograms by four injections. The other group received vehicle solution by the same schedule. The animals were perfused and fixed at 28 days after occlusion, and histological examination was made at the level of the caudoputamen and thalamus. In the bFGF-treated rats, the area of the posterior ventral thalamus of the occluded side was 93% of that of the contralateral side, i.e., significantly larger than in the normal saline-treated rats (75%, p less than 0.01). The infarction size was not statistically different in the two groups. Microscopic observation indicated that normal-saline-treated animals showed shrinkage and disappearance of thalamic neurons, whereas bFGF-treated groups showed preservation of thalamic neurons. Computerized analysis of the cell size substantiated this observation. To assess the effect of bFGF on astrocytes, bFGF or vehicle solution was injected into normal rats, and their histology was evaluated at 1, 2, and 4 weeks after injection. The bFGF-injected group showed a significant increase in glial fibrillary acidic protein-positive astrocytes in the brain tissue facing the ventriculocisternal system.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
4.
Magnetic resonance imaging (MRI) of the brain was performed in 10 patients with amyotrophic lateral sclerosis (ALS) and the findings were evaluated. Four patients had asymmetrical areas of increased signal intensity in the white matter. All patients showing abnormal MRI were young, had a longer clinical course, and clinically were more disabled. These MRI abnormalities were related to the pathological changes in the central white matter of patients with ALS and possible explanations for these findings in ALS are discussed.  相似文献   
5.
If defective cross-localization of fingertips (CLF) in callosal patients is due to a deficit in the interhemispheric transfer of somesthetic information, when the patient's eyes are open, CLF should be affected when the stimulated hand is excluded from vision, not when the responding hand is excluded from vision. In order to investigate this hypothesis, a patient with a callosal lesion was subjected to CLF with eyes closed and open. With eyes closed, the CLF score in the left-to-right direction was significantly lower than that in the right-to-left direction. With eyes open, the CLF performance in the right-to-left direction was impaired when it was the responding hand to be excluded from vision, not when it was the stimulated hand to be excluded from vision. It would, therefore, appear that the patient's CLF disturbance was not due to a somesthetic transfer deficit, but to left unilateral apraxia for the right-to-left direction errors and to left tactile finger anomia for the left-to-right direction errors.  相似文献   
6.
7.
8.
9.
1. We have recently identified a candidate gene for rat genetic hypertension, termed Sa, by identifying an mRN A species that shows markedly higher expression in the kidneys of spontaneously hypertensive rats (SHR) than in those of Wistar-Kyoto rats (WKY). 2. Subsequent genetic co-segregation analyses by ourselves and others indicated that the Sa gene locus did indeed influence blood pressure. Moreover, in a preliminary association study, we found an association of a polymorphism of the human Sa gene with essential hypertension. 3. Further studies to identify functions of the Sa gene products are required before reaching a definite conclusion.  相似文献   
10.
BACKGROUND: The oncologic benefit of avoiding allogenic blood transfusion in oesophageal cancer resection has not been studied. METHODS: The medical records of 68 patients (Auto group) who underwent a potentially curative oesophageal cancer resection without allogenic blood transfusion from 1996 to 1999 receiving 800 g of autologous blood donated preoperatively, and 97 patients (Allo group) who underwent the same operation with allogenic blood transfusion from 1990 to 1995 were compared. RESULTS: There were no differences in age, gender, stage of disease, number of retrieved nodes, or perioperative hemoglobin concentration between the two groups. The survival of the 45 patients with nodal involvement in the Auto group was better than that of the 59 patients in the Allo group (p=0.0435), and the survival of the 35 patients with T3 or T4 lesions in the Auto group was better than that of the 61 patients in the Allo group (p=0.0408). According to logistic regression analysis, allogenic blood transfusion correlated with tumour recurrence in patients with either nodal involvement or a T3-4 lesion. The natural killer cell activity remained higher in the Auto group than in the Allo group (p<0.05). CONCLUSION: Avoidance of allogenic blood transfusion favorably effected the survival of patients with oesophageal cancer at risk for recurrence.  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