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   17037篇
  免费   813篇
  国内免费   107篇
耳鼻咽喉   202篇
儿科学   278篇
妇产科学   186篇
基础医学   2103篇
口腔科学   278篇
临床医学   1253篇
内科学   4278篇
皮肤病学   224篇
神经病学   1247篇
特种医学   661篇
外科学   3330篇
综合类   45篇
一般理论   1篇
预防医学   496篇
眼科学   369篇
药学   1241篇
中国医学   48篇
肿瘤学   1717篇
  2023年   103篇
  2022年   189篇
  2021年   410篇
  2020年   211篇
  2019年   290篇
  2018年   374篇
  2017年   252篇
  2016年   293篇
  2015年   336篇
  2014年   464篇
  2013年   496篇
  2012年   814篇
  2011年   942篇
  2010年   498篇
  2009年   392篇
  2008年   759篇
  2007年   859篇
  2006年   845篇
  2005年   949篇
  2004年   889篇
  2003年   846篇
  2002年   846篇
  2001年   366篇
  2000年   438篇
  1999年   430篇
  1998年   203篇
  1997年   142篇
  1996年   185篇
  1995年   140篇
  1994年   137篇
  1993年   127篇
  1992年   365篇
  1991年   347篇
  1990年   289篇
  1989年   339篇
  1988年   297篇
  1987年   274篇
  1986年   264篇
  1985年   248篇
  1984年   156篇
  1983年   129篇
  1982年   70篇
  1979年   127篇
  1978年   92篇
  1977年   57篇
  1975年   67篇
  1974年   60篇
  1973年   56篇
  1972年   50篇
  1969年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
The abnormality of coronary arterial take-off is a limiting factor for a successful aortic valve sparing procedure. We present a 13-year-old boy, with Marfan syndrome and annuloaortic ectasia, whose coronary take-off was found to be abnormal during surgery. Two adjacent coronary orifices were located in the left coronary sinus and very close to the right-left commissure. A modified aortic remodeling procedure was successfully performed without translocation of the coronary artery.  相似文献   
913.
We describe a modified arch-first technique for total arch replacement through median sternotomy. This technique involves a short period of circulatory arrest (less than 30 minutes) and subsequent anterior cerebral perfusion. It does not require cannulation of the carotid vessels, which can cause cerebral thromboembolism, and it enables anterior cerebral perfusion to be resumed after a relatively short period of circulatory arrest. This appears to be a useful technique to reduce cerebral complications in complicated arch reconstruction operation for patients with severely atherosclerotic carotid vessels.  相似文献   
914.
Plasma glycerol is a major substrate for hepatic gluconeogenesis. Aquaporin adipose (AQPap/7), an adipose-specific glycerol channel, provides fat-derived glycerol into plasma. In the present study, we cloned the coding and promoter regions of mouse aquaporin 9 (AQP9), a liver-specific glycerol channel. Fasting and refeeding of mice increased and decreased hepatic AQP9 mRNA levels, respectively. Insulin deficiency induced by streptozotocin resulted in increased hepatic AQP9 mRNA. These changes in hepatic AQP9 mRNA were accompanied by those of hepatic gluconeogenic mRNAs and plasma glycerol levels. In cultured hepatocytes, insulin downregulated AQP9 mRNA. The AQP9 promoter contained the negative insulin response element TGTTTTC at -496/-502, similar to the promoter of the AQPap/7 gene. In contrast, in insulin-resistant db+/db+ mice, AQPap/7 mRNA in fat and AQP9 mRNA in liver were increased, despite hyperinsulinemia, with high plasma glycerol and glucose levels. Glycerol infusion in the db+/db+ mice augmented hepatic glucose output. Our results indicate that coordinated regulations of fat-specific AQPap/7 and liver-specific AQP9 should be crucial to determine glucose metabolism in physiology and insulin resistance.  相似文献   
915.
Adiponectin, an adipose-specific secretory protein, exhibits antidiabetic and antiatherogenic properties. In the present study, we examined the effects of sex hormones on the regulation of adiponectin production. Plasma adiponectin concentrations were significantly lower in 442 men (age, 52.6 +/- 11.9 years [mean +/- SD]) than in 137 women (53.2 +/- 12.0 years) but not different between pre- and postmenopausal women. In mice, ovariectomy did not alter plasma adiponectin levels. In contrast, high levels of plasma adiponectin were found in castrated mice. Testosterone treatment reduced plasma adiponectin concentration in both sham-operated and castrated mice. In 3T3-L1 adipocytes, testosterone reduced adiponectin secretion into the culture media, using pulse-chase study. Castration-induced increase in plasma adiponectin was associated with a significant improvement of insulin sensitivity. Our results indicate that androgens decrease plasma adiponectin and that androgen-induced hypoadiponectinemia may be related to the high risks of insulin resistance and atherosclerosis in men.  相似文献   
916.
A 75-year-old woman was admitted to our hospital with an extremely large retroperitoneal tumor that had been detected with ultrasound on a routine health check. She had no complaint except lumbar pain. Computed tomography revealed a heterogenous tumor located outside the right kidney which was enhanced gradually. Doppler ultrasound showed mild vascularity in the tumor. We performed tumorectomy and right nephrectomy because the tumor was adherent to the right kidney. The tumor was 16 x 11 x 7 cm in size and weighed 621 g. The histopathological diagnosis was malignant fibrous histiocytoma. The tumor was considered to have arisen from perirenal tissue.  相似文献   
917.
To investigate whether the use of a stentless porcine aortic xenograft can be an alternative for right ventricular outflow tract (RVOT) reconstruction during the Ross procedure, 9 patients underwent the Ross procedure and RVOT reconstruction with a stentless xenograft since January 2000. After the aortic valve was replaced with a pulmonary autograft, a stentless xenograft with a xeno- pericardial roll was implanted in the RVOT. One patient required subsequent aortic valve replacement because of severe regurgitation of the pulmonary autograft. All patients recovered well from the operation. The right ventricle-pulmonary arterial pressure gradient was 18 +/- 7 mm Hg at discharge and was not significantly increased during the 2-year follow-up period. Although 1 patient died of ventricular arrhythmia 5 months after, his cardiac function was normal, and transpulmonary valve pressure was 19 mm Hg in the follow-up. The other 7 patients are currently in New York Heart Association functional Class I. Although long-term follow-up is required to explain the durability, the stentless xenograft with a pericardial roll is considered to be an alternative for reconstruction of the RVOT within 2 years after the Ross procedure.  相似文献   
918.
A follow-up study was conducted on 5725 inhabitants (men 2858, women 2867) in and around the Jinzu River basin to determine the influence of environmental Cd exposure on mortality. In the Jinzu River basin, standardized mortality ratios (SMRs) investigated according to urinary findings (protein, glucose, and protein+glucose) were significantly low in the urinary protein-, glucose-, and protein+glucose-negative groups. SMRs calculated after dividing urinary protein- and glucose-positive status into two levels were lowest in the proteinuria- and glycosuria-negative groups and tended to be high in the higher positive groups. In the Jinzu River basin, Cox's hazard ratios were significantly higher for men and women in the urinary protein, glucose and protein+glucose-positive-groups. In the same analysis where the urinary protein- and glucose-positive subjects were divided into two levels, mortality was demonstrated to be higher in the groups with the greater degrees of proteinuria and glycosuria. In the Jinzu River water system almost all SMRs and Cox's hazard ratios showed statistical significance. This was not the case in the other water systems. Mortality of inhabitants with Cd-induced renal injury is increased in the Jinzu River basin.  相似文献   
919.
BACKGROUND: Phosphorylation of extracellular signal-regulated kinase (ERK) enhances various inflammatory responses in immune cells. It is unknown whether dysfunction of immune cells during malnutrition is attributed to derangement of ERK activation. METHODS: Male Institute of Cancer Research (ICR) mice received chow (146 g/kg per day, ad libitum or 36.5 g/kg per day, diet-restricted) for 7 days. Mice (n = 55) were given 6.5 mg/kg of an ERK inhibitor (PD98059) or vehicle intraperitoneally (IP), at 2 hours before cecal ligation and puncture (CLP). Survival was observed up to 60 hours. Detection of phosphorylated ERK (pERK) in the peritoneal exudative cells (PECs) was done as follows. In a separate study, PECs were harvested by peritoneal lavage 2 hours after an IP injection of 1% glycogen. PECs were incubated with or without 100 nmol/L N-formyl-methionyl-leucyl-phenylalanine (fMLP) for 1 minute. PEC ERK activation was detected with Western blot analysis (n = 38), by densitometric quantification, and with a laser scanning cytometer (LSC; n = 13). Subpopulations of PECs were determined by Wright-Giemsa staining. Unstimulated pERK expression was normalized to 100% for Western blot analysis. RESULTS: Diet restriction reduced survival after CLP compared with the ad libitum mice. ERK inhibition showed no effect on survival in diet-restricted mice but reduced survival in ad libitum mice. There were no differences in subpopulations of PECs 2 hours after glycogen injection between the groups. Western blot analysis revealed that fMLP stimulation significantly increased the phosphorylation of ERK1/2 in PECs from the ad libitum group (ERK1, 199 +/- 41%; ERK2, 211 +/- 49%; p < .03) but not in those from diet-restricted mice (ERK1, 98 +/- 10%; ERK2, 91 +/- 9%). Mean fluorescence intensity (MFI) of pERK in PECs obtained by LSC was significantly elevated after fMLP in the ad libitum group (from 19.4 +/- 1.5 MFI to 22.4 +/- 1.2 MFI; p < .05) but did not change in the diet-restricted group (from 19.4 +/- 1.8 MFI to 19.1 +/- 1.5 MFI). CONCLUSIONS: ERK activation is essential for survival in this murine sepsis model. Impaired ERK activation of PECs may, at least in part, impair host defense during malnutrition.  相似文献   
920.
A 66-year-old-man was admitted to our hospital because of chest pain on effort in October 1999. The initial images of 123I-BMIPP myocardial SPECT (BM) showed moderately decreased tracer uptake in the apex and the delayed images revealed redistribution in the apex. Coronary angiography revealed 99% stenosis in the proximal portion of the left anterior descending artery. Since sudden onset anaphylactic shock induced by contrast media developed, so percutaneous transluminal coronary angioplasty was not performed. The patient's symptoms were improved with medical treatment. On BM in March 2000, the initial images indicated slightly reduced uptake in the apico-anteroseptal region and the delayed images revealed mildly redistribution in the same area. BM in September 2000, the initial images showed moderately reduced uptake in the apico-anteroseptal region and the delayed images revealed high washout in the same area. The patient's symptoms markedly deferiorrated in March 2001, and BM initial images revealed slightly reduced uptake in the apico-anteroseptal region and the delayed images revealed redistribution in the same area again. During the clinical course, electrocardiography and 99mTc-tetrofosmin myocardial SPECT revealed no marked changes. We consider that 123I-BMIPP myocardial SPECT is useful in estimating myocardial ischemia.  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