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   1844篇
  免费   88篇
  国内免费   14篇
耳鼻咽喉   17篇
儿科学   31篇
妇产科学   16篇
基础医学   242篇
口腔科学   29篇
临床医学   110篇
内科学   398篇
皮肤病学   37篇
神经病学   286篇
特种医学   58篇
外科学   259篇
综合类   9篇
预防医学   62篇
眼科学   45篇
药学   173篇
中国医学   6篇
肿瘤学   168篇
  2023年   9篇
  2022年   27篇
  2021年   30篇
  2020年   20篇
  2019年   31篇
  2018年   35篇
  2017年   24篇
  2016年   35篇
  2015年   43篇
  2014年   62篇
  2013年   74篇
  2012年   128篇
  2011年   152篇
  2010年   63篇
  2009年   59篇
  2008年   104篇
  2007年   122篇
  2006年   113篇
  2005年   130篇
  2004年   141篇
  2003年   107篇
  2002年   114篇
  2001年   21篇
  2000年   13篇
  1999年   28篇
  1998年   17篇
  1997年   21篇
  1996年   30篇
  1995年   17篇
  1994年   22篇
  1993年   18篇
  1992年   11篇
  1991年   16篇
  1990年   10篇
  1989年   18篇
  1988年   11篇
  1987年   8篇
  1986年   7篇
  1985年   8篇
  1984年   5篇
  1983年   5篇
  1982年   6篇
  1981年   3篇
  1980年   4篇
  1978年   6篇
  1977年   3篇
  1976年   2篇
  1975年   3篇
  1969年   2篇
  1957年   1篇
排序方式: 共有1946条查询结果,搜索用时 15 毫秒
1.
Expression of β-catenin was investigated in normal breast tissue and 66 breast carcinomas in conjunction with expression of epithelial cadherin (E-CD) and α-catenin. In normal mammary ducts and acini, intense β-catenin immunoreactivity was present at the basolateral surfaces of luminal epithelium and weak immunoreactivity was observed at the lateral borders of myoepithelial cells. No β-catenin was revealed at the myoepithelial basal surface. The intercellular expression of β-catenin, as well as of E-CD and α-catenin, was also observed in carcinoma tissues with varying staining intensity. Almost all of 10 intraductal carcinomas and approximately 70% of 41 invasive ductal carcinomas expressed the three molecules at the same level as in normal glands, whereas approximately 80% of 13 invasive lobular carcinomas showed severe deficiency of them. Two lobular carcinomas in situ showed complete absence of all of the proteins. Some of these findings were confirmed biochemically by immunoblotting analysis. In invasive ductal carcinomas, α-catenin was reduced more frequently in diffuse than in solid type tumours, whereas the level of expression of β-catenin and E-CD was unchanged between them. No correlation was present between reduced expression of the adhesion molecules and lymph node metastasis.  相似文献   
2.
We report a patient manifesting seizures with bilateral symmetric tonic posturing, which were markedly reduced after resection of the left precuneus. A 16-year-old man had sudden onset, complex partial seizures with bilateral symmetric tonic posturing since the age of eight years. Magnetic resonance fluid-attenuated inversion-recovery imaging revealed a hyperintense lesion in left precuneus. In almost all focal seizures recorded during an invasive EEG evaluation, ictal onset was detected from the inferomesial aspect of the lesion, but fast paroxysmal discharges from the ipsilateral supplementary motor area (SMA) were observed just before the clinical onset. After surgical excision of the EEG onset zone, including the lesion, seizure frequency was markedly (> 95%) reduced. By the 20th month after surgery, there were only brief nocturnal seizures involving slight elevation of both shoulders and slight abduction of both arms, with preservation of consciousness occurring once every few days. Invasive EEG findings and surgical outcome suggested that the epileptic activity originating from the epileptogenic zone may have propagated to the symptomatogenic zone including mainly the ipsilateral SMA. In summary, we report an interesting case of bilateral symmetric tonic posturing suggesting propagation to the SMA. MRI and invasive EEG confirmed the epileptogenic focus as a precuneate cortical dysplasia lesion.[Published with video sequences].  相似文献   
3.
We describe the case of a 40-year-old man whose disease was initially diagnosed as acute myelocytic leukemia. The patient achieved remission with chemotherapy, but relapsed shortly afterwards with an acute T-cell lymphoblastic leukemia. He died of intracranial bleeding. Karyotyping analysis showed a del(9p?) as a common abnormality in the leukemic cells at onset and relapse. Fluorescence in situ hybridization analysis demonstrated allelic loss of the CDKN2A gene in cells from both stages of the disease. At relapse the leukemia cells had additional abnormalities such as add(1)(p36) and del(12)(p11). We postulate that the loss of CDKN2A is involved in leukemogenesis but does not determine the lineage of the leukemic cells. Instead, abnormalities of genes at 1p36, 12p11, or both may be involved in driving a lymphoid phenotype.  相似文献   
4.
Protodioscin (PD) was purified from fenugreek (Trigonella foenumgraecum L.) and identified by Mass, and 1H- and 13C-NMR. The effects of PD on cell viability in human leukemia HL-60 and human stomach cancer KATO III cells were investigated. PD displayed strong growth inhibitory effect against HL-60 cells, but weak growth inhibitory effect on KATO III cells. Morphological change showing apoptotic bodies was observed in the HL-60 cells treated with PD, but not in KATO III cells treated with PD. Flow cytometric analysis showed that the hypodiploid nuclei of HL-60 cells were increased to 75.2, 96.3, and 100% after a 3-day treatment with 2.5, 5, and 10 microM PD, respectively. The fragmentation by PD of DNA to oligonucleosomal-sized fragments, that is a characteristic of apoptosis, was observed to be both concentration- and time-dependent in the HL-60 cells. These findings suggest that growth inhibition by PD of HL-60 cells results from the induction of apoptosis by this compound in HL-60 cells.  相似文献   
5.
Pacific Islands populations can be broadly divided into Austronesians (AN) and Non-Austronesians (NAN); obesity and type 2 diabetes are prevalent in the former, although leptin levels in both groups have seldom been investigated. Thirty-seven (20 male and 17 female) adult pairs, matched by age and percent body fat, from AN-speaking Balopa and NAN-speaking Huli, all of whom migrated to settle in Port Moresby, the capital of Papua New Guinea, were selected for comparison of their serum leptin concentrations. The Balopa did not differ significantly from the Huli in age (30.5 +/- 9.7 and 30.0 +/- 8.7 years for males, 33.7 +/- 8.9 and 34.1 +/- 7.5 years for females, respectively) or percent body fat (19.4 +/- 5.6 and 18.8 +/- 4.6 for males, 34.1 +/- 6.2 and 33.3 +/- 5.0 for females), although the BMI of females was lower in the Balopa (26.4 +/- 4.9) than in the Huli (29.7 +/- 4.7) (P = 0.02). In both ethnic groups, females had markedly higher leptin concentrations than males, but there was no significant inter-group difference in males (3.5 +/- 2.6 and 3.1 +/- 4.7 ng/ml, P = 0.14) or females (22.7 +/- 12.9 and 19.7 +/- 11.9 ng/ml, P = 0.40), after controlling for lifestyle factors and serum lipids. Multiple regression analysis revealed that significant predictors of leptin concentration were % body fat (beta = 0.58), sex (male, 0; female, 1; beta = 0.27), and smoker status (non-smoker, 0; smoker, 1; beta = -0.15) (R(2) = 0.80), implying that the leptin concentration was primarily determined by lifestyle-derived body fatness. In conclusion, the NAN populations do not endogenously differ in leptin status from the AN populations, who have been recognized as a typical group with a "thrifty" genotype.  相似文献   
6.
7.
2-O-methylisohemigossylic acid lactone, a sesquiterpene, was purified from roots of mokumen (Gossampinus malabarica) and identified by Mass, and (1)H- and (13)-NMR. This sesquiterpene displayed strong growth inhibitory effect against human promyelotic leukemia HL-60 cells. Apoptotic morphological change of the nucleus, including chromatin condensation was induced in the HL-60 cells treated with the sesquiterpene. The fragmentation of DNA by the sesquiterpene to oligonucleosomal-sized fragments, a characteristic of apoptosis, was observed to be dose- and time-dependent in the HL-60 cells. Inhibitors of caspases suppressed the DNA fragmentation induced by the sesquiterpene. These findings suggest that growth inhibition by the sesquiterpene of HL-60 cells results from the induction of apoptosis by the sesqui-terpene, and that caspase cascade is involved in the induction of apoptosis by the compound in the HL-60 cells.  相似文献   
8.
Summary The relationship between the accumulation of isoprenaline and the incidence and duration of ventricular fibrillation was investigated in the perfused rat heart. Isolated rat hearts were perfused with 3H-isoprenaline (1 mol/l) for 30 min at a constant flow rate of 6.5 ml/min at a temperature between 40 and 41° C. Electrocardiograms were recorded during the perfusion period and the isoprenaline content of the tissue was measured after the perfusion. The accumulation of isoprenaline was significantly increased and the duration of ventricular fibrillation was significantly prolonged by the presence of tropolone (100 mol/l). When extraneuronal uptake inhibitors such as normetanephrine (100 mol/l), 3-O-methylisoprenaline (100 mol/l) or phenoxybenzamine (1 mol/l) were added to the perfusion fluid containing 3H-isoprenaline (1 mol/l) and tropolone (100 mol/l), the accumulation of isoprenaline was sifnificantly decreased, the incidence of ventricular fibrillation was significantly reduced and the duration of ventricular fibrillation was significantly shortened. There was a significant correlation for dependence of duration of ventricular fibrillation on the isoprenaline content of rat hearts perfused with various extraneuronal uptake inhibitors in the presence of tropolone (correlation coefficient [r]=0.62, P<0.001).These results indicate that the accumulation of isoprenaline in perfused rat hearts relates to the occurrence and duration of ventricular fibrillation.This study was supported in part by a Grant-in-Aid for Scientific Research (59570980) from the Ministry of Education, Science and Culture, Japan  相似文献   
9.
Malnutrition is a core symptom of the frailty cycle in older adults. The purpose of this study was to investigate whether dysphagia influences nutrition or frailty status in community-dwelling older adults. The study participants were 320 Japanese community-dwelling older adults aged ≥65 years. All participants completed a questionnaire survey that included items on age, sex, family structure, self-rated health, nutritional and frailty status, and swallowing function. Nutritional status was categorized as malnourished, at risk of malnutrition, and well-nourished based on the Mini Nutrition Assessment-Short Form. The participants were then classified into a malnutrition (malnourished/at risk) or a well-nourished group (well-nourished). Frailty was assessed using the Cardiovascular Health Study criteria. The participants were then divided into a frailty (frail/pre-frail) or a non-frailty group (robust). Dysphagia was screened using the 10-item Eating Assessment Tool. Multiple logistic regression analysis was conducted to determine whether dysphagia was associated with nutritional or frailty status. The results revealed that dysphagia influenced both nutrition (odds ratio [OR]: 4.0; 95% confidence interval [CI]: 1.9–8.2) and frailty status (OR: 2.3; 95% CI: 1.0–5.2); therefore, the swallowing function would be an important factor for community-dwelling older adults on frailty prevention programs.  相似文献   
10.
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