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   7468篇
  免费   303篇
  国内免费   35篇
耳鼻咽喉   26篇
儿科学   115篇
妇产科学   88篇
基础医学   790篇
口腔科学   151篇
临床医学   491篇
内科学   1920篇
皮肤病学   75篇
神经病学   592篇
特种医学   347篇
外科学   1270篇
综合类   37篇
预防医学   152篇
眼科学   454篇
药学   430篇
中国医学   12篇
肿瘤学   856篇
  2022年   56篇
  2021年   114篇
  2020年   56篇
  2019年   93篇
  2018年   107篇
  2017年   101篇
  2016年   146篇
  2015年   123篇
  2014年   176篇
  2013年   190篇
  2012年   327篇
  2011年   320篇
  2010年   203篇
  2009年   169篇
  2008年   293篇
  2007年   308篇
  2006年   331篇
  2005年   309篇
  2004年   329篇
  2003年   312篇
  2002年   352篇
  2001年   298篇
  2000年   326篇
  1999年   268篇
  1998年   88篇
  1997年   81篇
  1996年   66篇
  1995年   64篇
  1994年   63篇
  1993年   54篇
  1992年   194篇
  1991年   168篇
  1990年   151篇
  1989年   167篇
  1988年   156篇
  1987年   101篇
  1986年   136篇
  1985年   123篇
  1984年   78篇
  1983年   75篇
  1979年   74篇
  1978年   44篇
  1977年   46篇
  1974年   46篇
  1973年   49篇
  1972年   46篇
  1971年   58篇
  1970年   38篇
  1969年   41篇
  1968年   45篇
排序方式: 共有7806条查询结果,搜索用时 15 毫秒
101.
Purpose We compared the clinicopathologic features affecting outcome after surgery for hepatocellular carcinoma (HCC) between patients with concurrent and previous chronic hepatitis B.Methods Group A consisted of 58 patients with concurrent chronic hepatitis B, defined by seropositivity for the hepatitis B surface antigen (HBsAg), and group B consisted of 18 patients whose HCC was detected after disappearance of the HBsAg. We assessed the influence of various characteristics on outcome.Results The mean age and percentage of patients suffering from alcohol abuse or diabetes mellitus were significantly greater in group B than in group A, whereas histologic hepatitis activity, hepatic fibrosis, and alanine aminotransferase activity were significantly lower in group B than in group A. The tumor-free survival rates were similar between the two groups, but the risk factors of recurrence differed. In group A, relative youth, high aspartate aminotransferase activity, low platelet count, multiple tumors, large tumor size, portal invasion, cirrhosis, nonanatomic resection, and positive surgical margin were risk factors. In group B, large tumor size and poor differentiation were risk factors.Conclusion Hepatitis B status, tumor factors, and the type of operation affected cancer recurrence after surgery for HCC in patients with concurrent chronic HBV, as opposed to only tumor factors in patients with previous chronic hepatitis B.  相似文献   
102.
Reye's syndrome with cortical laminar necrosis: MRI   总被引:1,自引:0,他引:1  
Serial MRI findings are described in two patients with Reye's syndrome, demonstrating diffuse cortical and white matter changes. In the acute stage, T2-weighted images showed subtle but definite laminar high signal and contrast-enhanced T1-weighted images laminar enhancement, along the entire cerebral cortexbilateraly. In the chronic stage, unenhanced T1-weighted images showed diffuse cortical laminar high signal. These characteristic MRI features seemed very similar to those of laminar cortical necrosis in hypoxic brain damage. MRI also displayed delayed white matter changes with cerebral atrophy.  相似文献   
103.
A transjugular snare technique was used to retrieve a stretched, residual mechanical detachable coil which extended from the cavernous sinus to the femoral vein, obliterating the transpetrosal route for further embolisation. The coil was snared by a microguidewire. Our new technique is described in this paper. Received: 19 April 1995 Accepted: 31 July 1995  相似文献   
104.
Tl-201 SPECT was performed on 12 patients with Nasopharyngeal carcinoma (NPC) by means of a three-head rotating gamma camera to evaluate whether or not Tl-201 SPECT was useful and reliable for assessing the tumor viability of NPC. Tl-201 clearly accumulated in the tumor in 3 patients before radiation treatment and increased Tl-201 uptake by the lesion ceased after the treatment. Three of 9 patients who were followed up after radiotherapy developed apparent local recurrence and Tl-201 SPECT clearly visualized these recurrent lesions. Tl-201 SPECT was very useful for assessing the tumor response to irradiation and for detecting local recurrent tumor. A High resolution SPECT system employing Tl-201 chloride is a new reliable and accurate diagnostic tool for the assessment of NPC.  相似文献   
105.
We applied bone SPECT for the examination of the cervical spine. A three-head rotating gamma camera SPECT system was employed for this study. The SPECT image disclosed 42.7 % of abnormal accumulations in the skeleton not seen with planar imagings. SPECT could separately visualize the trachea and thyroid cartilage and also provided interpretation of abnormality in the anterior part of the vertebral body being difficult with planar imagings only. The trachea cartilage was seen in 55.4% and the thyroid cartilage was seen in 47.3% of patients with anterior neck density in planar imagings. SPECT clarified that marked cervical curvature and diffuse high uptake by the skeleton might cause high intensity of the anterior neck in planar imagings in the case of non-pathological change. We concluded that bone SPECT is a useful diagnostic tool in detecting occult lesion in the skeleton and to rule out extraskeletal accumulations in examination of the cervical spine.  相似文献   
106.
Primary Sj?gren syndrome (SjS) has a comparatively good prognosis except when it is complicated by non-Hodgkin's lymphoma. We performed an autopsy on a young female patient with primary SjS who had died suddenly during a meal, and we discuss the relationship between primary SjS and the cause of death. Eosinophilic change of the cardiomyocytes and severe arteriolosclerosis were observed within the myocardium. In the conduction system, lymphocyte infiltration was detected in the bundle of His, in addition to arteriosclerosis in the sinoatrial node and atrioventricular node arteries. The cause of death was diagnosed as ischaemic heart disease induced by arteriolosclerosis: its development can probably be attributed mostly to primary SjS. It should thus be kept in mind that primary SjS can occasionally result in the development of cardiovascular complications, such as ischaemic heart disease, as well as systemic lupus erythematosus or rheumatoid arthritis.  相似文献   
107.
Purpose  This study was undertaken to evaluate the changes in the radiopacity and mechanics of polymethylmethacrylate (PMMA) bone cement with the addition of barium. Materials and methods  Barium sulfate powder was added to a PMMA bone cement with an initial 10% barium concentration. The changes in radiopacity and strength were evaluated by testing cement blocks containing four barium concentrations (10%, 20%, 30%, 40%). Radiopacity was evaluated by measuring the computed tomography (CT) values of the bone cement, and strength was evaluated by compressive, three-point bending, and impact load tests. Results  CT values increased in proportion to the barium concentration. The compressive load test showed that cement with a 40% barium concentration was significantly more fragile than cement with lower barium concentrations. The three-point bending load test showed that the cement became more fragile in proportion to the barium concentration. The impact load test showed that cement with 30% and 40% barium concentrations was significantly more fragile than cement with 10% and 20% barium concentrations. Conclusion  Radiopacity is increased and strength is reduced by adding increasing concentrations of barium powder to bone cement. The results of the present study suggest that adding barium permits the radiopacity and strength of bone cement to be adjusted in clinical practice.  相似文献   
108.
BACKGROUND: Carbon dioxide is an important vasodilator of cerebral blood vessels. Cerebral vasodilation mediated by adenosine triphosphate (ATP)-sensitive K+ channels has not been demonstrated in precapillary microvessel levels. Therefore, the current study was designed to examine whether ATP-sensitive K+ channels play a role in vasodilation induced by mild hypercapnia in precapillary arterioles of the rat cerebral cortex. METHODS: Brain slices from rat cerebral cortex were prepared and superfused with artificial cerebrospinal fluid, including normal (Pco2 = 40 mmHg; pH = 7.4), hypercapnic (Pco2 = 50 mmHg; pH = 7.3), and hypercapnic normal pH (Pco2 = 50 mmHg; pH = 7.4) solutions. The ID of a cerebral parenchymal arteriole (5-9.5 microm) was monitored using computerized videomicroscopy. RESULTS: During contraction to prostaglandin F2alpha (5 x 10(-7) m), hypercapnia, but not hypercapnia under normal pH, induced marked vasodilation, which was completely abolished by the selective ATP-sensitive K+ channel antagonist glibenclamide (5 x 10(-6) m). However, the selective Ca2+-dependent K+ channel antagonist iberiotoxin (10(-7) m) as well as the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (10(-4) m) did not alter vasodilation. A selective ATP-sensitive K+ channel opener, levcromakalim (3 x 10(-8) to 3 x 10(-7) m), induced vasodilation, whereas this vasodilation was abolished by glibenclamide. CONCLUSION: These results suggest that in parenchymal microvessels of the rat cerebral cortex, decreased pH corresponding with hypercapnia, but not hypercapnia itself, contributes to cerebral vasodilation produced by carbon dioxide and that ATP-sensitive K+ channels play a major role in vasodilator responses produced by mild hypercapnia.  相似文献   
109.
BACKGROUND: Serious side effects of postoperative analgesia with opioid drugs include nausea and vomiting. METHODS: We investigated the effects of various factors (patient background, anesthesia duration, and intraoperative drug use) on the frequency and degree of postoperative nausea and vomiting (PONV) during the first 24 hours of intravenous patient-controlled analgesia (PCA) with fentanyl. RESULTS: PONV occurred in 34% of the male patients and 68% of the female, and in 31% and 58% of smokers and non-smokers, respectively. CONCLUSIONS: Consideration should be given to gender and smoking status prior to starting preventive antiemetic therapy using PCA with fentanyl following cervical spine surgery.  相似文献   
110.
Background: Carbon dioxide is an important vasodilator of cerebral blood vessels. Cerebral vasodilation mediated by adenosine triphosphate (ATP)-sensitive K+ channels has not been demonstrated in precapillary microvessel levels. Therefore, the current study was designed to examine whether ATP-sensitive K+ channels play a role in vasodilation induced by mild hypercapnia in precapillary arterioles of the rat cerebral cortex.

Methods: Brain slices from rat cerebral cortex were prepared and superfused with artificial cerebrospinal fluid, including normal (Pco2 = 40 mmHg; pH = 7.4), hypercapnic (Pco2 = 50 mmHg; pH = 7.3), and hypercapnic normal pH (Pco2 = 50 mmHg; pH = 7.4) solutions. The ID of a cerebral parenchymal arteriole (5-9.5 [mu]m) was monitored using computerized videomicroscopy.

Results: During contraction to prostaglandin F2[alpha] (5 x 10-7 m), hypercapnia, but not hypercapnia under normal pH, induced marked vasodilation, which was completely abolished by the selective ATP-sensitive K+ channel antagonist glibenclamide (5 x 10-6 m). However, the selective Ca2+-dependent K+ channel antagonist iberiotoxin (10-7 m) as well as the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (10-4 m) did not alter vasodilation. A selective ATP-sensitive K+ channel opener, levcromakalim (3 x 10-8 to 3 x 10-7 m), induced vasodilation, whereas this vasodilation was abolished by glibenclamide.  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