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   7227篇
  免费   381篇
  国内免费   58篇
耳鼻咽喉   141篇
儿科学   229篇
妇产科学   85篇
基础医学   847篇
口腔科学   153篇
临床医学   431篇
内科学   2067篇
皮肤病学   92篇
神经病学   377篇
特种医学   436篇
外科学   1272篇
综合类   30篇
一般理论   1篇
预防医学   146篇
眼科学   125篇
药学   353篇
中国医学   13篇
肿瘤学   868篇
  2024年   6篇
  2023年   67篇
  2022年   163篇
  2021年   258篇
  2020年   114篇
  2019年   181篇
  2018年   216篇
  2017年   183篇
  2016年   198篇
  2015年   197篇
  2014年   257篇
  2013年   332篇
  2012年   534篇
  2011年   550篇
  2010年   287篇
  2009年   224篇
  2008年   419篇
  2007年   466篇
  2006年   455篇
  2005年   489篇
  2004年   400篇
  2003年   445篇
  2002年   423篇
  2001年   53篇
  2000年   41篇
  1999年   73篇
  1998年   96篇
  1997年   68篇
  1996年   67篇
  1995年   72篇
  1994年   49篇
  1993年   58篇
  1992年   37篇
  1991年   28篇
  1990年   16篇
  1989年   23篇
  1988年   20篇
  1987年   10篇
  1986年   6篇
  1985年   9篇
  1984年   9篇
  1983年   9篇
  1982年   6篇
  1981年   12篇
  1980年   10篇
  1979年   9篇
  1978年   3篇
  1977年   4篇
  1976年   4篇
  1974年   3篇
排序方式: 共有7666条查询结果,搜索用时 15 毫秒
81.
82.
This study aimed to evaluate the clinical use of choline-PET/CT for discriminating viable progressive osteoblastic bone metastasis from benign osteoblastic change induced by the treatment effect and evaluating the response of bone metastasis to treatment in metastatic castration-resistant prostate cancer (mCRPC) patients. Thirty patients with mCRPC underwent a total of 56 11C-choline-PET/CT scans for restaging, because 4 patients received 1 scan and 26 had 2 scans. Using 2 (pre- and post-treatment) 11C-choline-PET/CT examinations per patient, treatment response was assessed according to European Organization for Research and Treatment of Cancer (EORTC) criteria in 20 situations, in which only bony metastases were observed on 11C-choline-PET/CT scans. Viable bone metastases and osteoblastic change induced by the treatment effect were identified in 53 (94.6%) and 29 (51.8%) of 56 11C-choline-PET/CT scans, respectively. In 27 cases (48.2%), 11C-choline-PET/CT scans could discriminate the 2 entities. The mean SUVmax of the metastatic bony lesions was 5.82 ± 3.21, 5.95 ± 3.96, 6.73 ± 5.04, and 7.91 ± 3.25 for the osteoblastic, osteolytic, mixed, and invisible types, respectively. Of the 20 situations analyzed, CMR, PMR, SMD, and PMD, as determined by the EORTC, were seen in 1, 2, 3, and 14 cases, respectively. Of the 13 patients with increasing PSA trend, all 13 showed PMD. Of the 2 patients with PSA response of <50%, both 2 showed SMD. Of the 5 patients with PSA response of ≥50%, 1 showed CMR, 2 showed PMR, 1 showed SMD, and 1 showed PMD. Choline-PET/CT is very useful to discriminate viable progressive osteoblastic bone metastasis from osteoblastic change, and assess treatment response of bone metastases in mCRPC.  相似文献   
83.
Digestive Diseases and Sciences - Hepatocellular carcinoma develops in some patients with hepatitis C virus (HCV), even after achieving sustained virological response (SVR). We examined factors...  相似文献   
84.
A patient with acute myelogenous leukemia developed prolonged bone marrow failure along with the monosomy 7 chromosome abnormality. The patient had undergone bone marrow transplantation with CD34+ selection following induction failure. However, she then suffered engraftment failure and long-term pancytopenia. Her white blood cell count gradually increased with supportive therapy including granulocyte colony-stimulating factor (G-CSF), and chromosomal analysis of bone marrow cells revealed an abnormal karyotype. Thirty months after the bone marrow transplantation we observed monosomy 7 together with the existing chromosomal abnormality in the patient's bone marrow cells. It has been reported that some patients with idiopathic and posthepatitis aplastic anemia develop clonal disorders such as myelodysplastic syndrome/acute myelogenous leukemia with monosomy 7. The findings in our case suggest that the appearance of monosomy 7 in patients with aplastic anemia may be caused by prolonged low-level hematopoiesis, with or without G-CSF stimulation.  相似文献   
85.
Phlebosclerosis of the mesenteric vein is a rare condition causing chronic intestinal ischemia, it has only been reported in Japan. A 56-year-old man with liver cirrhosis and hepatic tumor presented with phlebosclerosis of mesenteric vein without any abdominal symptoms. He was admitted for examination of suspected hepatic tumor. Abdominal plain x-ray films and computed tomography revealed calcification of the mesenteric vein. Barium enema revealed narrowing and thumbprinting from the cecum to transverse colon. On colonoscopic examination, blue-black vessels were visible in the terminal ileum, and hyperemic nodular mucosa with small irregular ulcers surrounded by dark purple mucosa was found from the cecum to transverse colon. The etiology of mesenteric vein phlebosclerosis is unknown, although a physical mechanism rather than inflammatory changes appear to be involved in this rare and usually progressive condition of chronic intestinal ischemia.  相似文献   
86.
OBJECTIVES: We conducted a collaborative cohort study to evaluate the predictive power of microvolt T-wave alternans (TWA) in patients with preserved left ventricular ejection fraction (LVEF) after myocardial infarction (MI). BACKGROUND: There is little information available about the prognostic value of risk stratification markers in this population. Although these patients have a relatively good prognosis, identifying high-risk patients is important in clinical practice. METHODS: This study enrolled 1,041 post-MI patients with an LVEF > or =40% (average 55 +/- 10%). Microvolt TWA testing was performed 48 +/- 66 days after acute MI, and 10 other risk variables were also evaluated. The end points were prospectively defined as sudden cardiac death or life-threatening arrhythmic events. RESULTS: During a follow-up of 32 +/- 14 months, 38 patients (3.7%) died of nonarrhythmic causes and were not considered for analysis. Of the 1,003 evaluable patients, 18 (1.8%) reached an end point. Microvolt TWA was positive in 169 patients (17%), negative in 747 (74%), and indeterminate in 87 (9%). A positive microvolt TWA test, nonsustained ventricular tachycardia, and ventricular late potentials were predictors of events, and percutaneous coronary intervention decreased the risk rate. On multivariate analysis, a positive microvolt TWA test was the most significant predictor, with a hazard ratio of 19.7 (p < 0.0001). This marker had the highest sensitivity and negative predictive value for events. CONCLUSIONS: In patients with preserved cardiac function, the incidence of indeterminate results of microvolt TWA is low, and a positive test result is associated with arrhythmic events. Microvolt TWA could be used for risk stratification in this low-risk population.  相似文献   
87.
OBJECTIVES: The relation between the occurrence of pacing-induced mechanical alternans and prognosis in patients with mild-to-moderate idiopathic dilated cardiomyopathy (IDCM) in sinus rhythm was investigated prospectively. The myocardial expression of genes for Ca2+-handling proteins in such patients was also examined. BACKGROUND: Mechanical alternans occurs in some patients with severe heart failure, but the relation between the occurrence of mechanical alternans and prognosis in patients with IDCM has remained unknown. METHODS: Left ventricular (LV) pressure was measured during atrial pacing, and LV endomyocardial biopsy specimens were collected in 36 IDCM patients and 8 controls. Idiopathic dilated cardiomyopathy patients were divided into two groups consisting of 22 individuals who did not develop mechanical alternans at heart rates up to 140 beats/min (group A) and of 14 individuals who did (group B). The patients were followed up for a mean of 3.7 years. RESULTS: There was no significant difference in LV ejection fraction or the plasma concentration of brain natriuretic peptide between groups A and B. The myocardial abundance of ryanodine receptor 2 messenger ribonucleic acid (mRNA) was significantly lower in groups A and B than in controls, whereas that of sarcoplasmic reticulum Ca2+-ATPase mRNA was significantly lower in group B than in group A or controls. Stepwise multivariate analysis identified pacing-induced mechanical alternans as the strongest predictor of cardiac events. Event-free survival in group A was significantly greater than that in group B. CONCLUSIONS: The occurrence of pacing-induced mechanical alternans is a potentially useful indicator of poor prognosis in patients with mild-to-moderate IDCM in sinus rhythm.  相似文献   
88.
Partial intertarsal joint arthrodesis was performed on 12 feet of 11 patients as a surgical treatment for planovalgus deformity of the foot and lesions of the intertarsal joints caused by rheumatoid arthritis. Single arthrodesis was performed on the talocalcaneal joint in eight feet, two of which underwent simultaneous total ankle arthroplasty, and on the talonavicular joint in two feet. Double arthrodesis was done on the talocalcaneal and talonavicular joints in one foot and on the talonavicular and calcaneocuboid joints in one foot. Screws or staples were used for fixation. Patients were followed for 2 years to 8 years 7 months (average 4 years 3 months). Osseous fusion was achieved in all feet, and satisfactory pain relief was obtained in all cases except one. We performed this surgery in patients who were relatively active, and the results indicated that arthrodesis of a small number of joints that caused pain and deformity was effective in reducing pain and correcting the deformity. We concluded that partial tarsal arthrodesis should be performed on a limited number of joints during the early stages of planovalgus deformity of the foot because more joints are found to be fixed during the advanced stages. However, progression of the osteoarthritis was found in the neighboring joints. Close follow-up observation is needed.  相似文献   
89.
A 73-year-old woman was admitted with consciousness disturbance following a fever. Abdominal computed tomography revealed a large liver abscess with which the presence of Desulfovibrio desulfuricans and Escherichia coli was confirmed by thorough blood and abscess content culture. Empiric meropenem treatment was switched to cefoperazone/sulbactam, followed by ampicillin/sulbactam based on susceptibility testing. Desulfovibrio desulfuricans is a common bacterium that rarely causes liver abscess and may be overlooked during co-infection due to overgrowth of the accompanying bacteria. Clinicians should bear Desulfovibrio desulfuricans in mind and select the appropriate antibiotics according to susceptibility testing when anaerobic bacteria are detected in a liver abscess.  相似文献   
90.

Purpose

Positron emission tomography (PET) in non-human primates (NHP) is commonly performed under anesthesia, with sevoflurane being a widely used inhaled anesthetic. PET measurement in NHP can be repeated, and a difference in radioligand kinetics has previously been observed between the first and second PET measurement on the same day using sevoflurane anesthesia. In this study, we evaluated the effect of prolonged sevoflurane anesthesia on kinetics and binding potential (BPND) of [11C]raclopride in NHP.

Procedures

Three cynomolgus monkeys underwent two to three PET measurements with [11C]raclopride under continuous sevoflurane anesthesia on the same day. The concentration of sevoflurane was adjusted according to the general conditions and safety parameters of the NHP. Time to peak (TTP) radioactivity in the striatum was estimated from time-activity curves (TACs). The BPND in the striatum was calculated by the simplified reference tissue model using the cerebellum as reference region.

Results

In each NHP, the TTP became shorter in the later PET measurements than in the first one. Across all measurements (n = 8), concentration of sevoflurane correlated with TTP (Spearman’s ρ = ? 0.79, p = 0.03), but not with BPND (ρ = ? 0.25, p = 0.55).

Conclusions

These data suggest that sevoflurane affects the shape of TACs but has no evident effect on BPND in consecutive PET measurements.
  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