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   578篇
  免费   27篇
  国内免费   1篇
耳鼻咽喉   2篇
儿科学   4篇
妇产科学   1篇
基础医学   71篇
口腔科学   4篇
临床医学   22篇
内科学   142篇
皮肤病学   4篇
神经病学   41篇
特种医学   2篇
外科学   110篇
预防医学   8篇
眼科学   10篇
药学   108篇
中国医学   2篇
肿瘤学   75篇
  2024年   1篇
  2023年   4篇
  2022年   3篇
  2021年   12篇
  2020年   4篇
  2019年   5篇
  2018年   22篇
  2017年   11篇
  2016年   8篇
  2015年   14篇
  2014年   28篇
  2013年   32篇
  2012年   53篇
  2011年   36篇
  2010年   27篇
  2009年   21篇
  2008年   40篇
  2007年   34篇
  2006年   27篇
  2005年   27篇
  2004年   35篇
  2003年   27篇
  2002年   32篇
  2001年   6篇
  2000年   8篇
  1999年   8篇
  1998年   8篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   2篇
  1993年   4篇
  1992年   6篇
  1991年   13篇
  1990年   7篇
  1989年   8篇
  1988年   5篇
  1986年   1篇
  1985年   4篇
  1984年   3篇
  1981年   4篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1972年   1篇
  1968年   1篇
排序方式: 共有606条查询结果,搜索用时 218 毫秒
1.
2.
A 51-year-old man was admitted because of hemoptysis. Physical examinations and chest XP revealed no abnormal findings. Fiberoptic bronchoscopy showed pulsatile bleeding at the orifice of right B6. Right bronchial arteriography showed a markedly dilated and tortous bronchial artery and shunting to the pulmonary arterial system in the middle and lower lobes. Pulmonary arteriography showed complete obstruction of the right middle lobar and lower lobe segmental arteries (A6, 9, 10). The hemoptysis was thought to be due to increased blood flow of the right bronchial artery, which compensated for reduced right pulmonary arterial flow. Right middle and lower lobe resection was done to prevent further hemoptysis. The resected specimen revealed old thromboemboli in the right middle and lower lobe pulmonary arteries. In this case old pulmonary embolism should be considered as a cause of intrabronchial bleeding.  相似文献   
3.
Changes in MAP2 and clathrin immunoreactivity were studied in gerbil hippocampus after transient cerebral ischemia. MAP2 immuno-reactivity decreased significantly by 1 h in the subiculum-CA1 and CA2 areas which correspond to reactive change, while no decrease was observed in CA1 until day 4. Before the initiation of delayed neuronal death, MAP2 immunoreactivity was not changed in CA1. On the other hand clathrin immunoreactivity increased in the pyramidal cell layer of CA1 by 3 h after ischemia and remained high for 2 days. Clathrin immunoreactivity in the pyramidal cell layer of CA1 diminished after delayed neuronal death. The transient change of clathrin was noted especially in CA1 in the period prior to delayed neuronal death. These results imply an abnormal change in clathrin turnover after ischemia, which may participate in the pathogenesis of delayed neuronal death.  相似文献   
4.
A series of [1,3]thiazeto[3,2-a]quinoline-3-carboxylic acids and their esters were prepared and evaluated for antibacterial activity. The derivatives with a hydrogen or methyl group at C-1, fluorine at C-6, and piperazinyl or 4-methyl-1-piperazinyl group at C-7 showed superior in vitro antibacterial activity, and the derivatives with 4-methyl-1-piperazinyl group at C-7 had potent in vivo activity. Compound 29a (NM394) showed excellent in vitro antibacterial activity and low toxicity but poor absorption from the gastrointestinal tract. Compound 29ee (NM441), an N-[(5-methyl-2-oxo-1,3-dioxol-4-yl)methyl] derivative of 29a, was found to possess a favorable pharmacokinetic profile and oral activity superior to that of ciprofloxacin in experimental animals.  相似文献   
5.
The age-dependent change in activities of seven lysosomal enzymes (cathepsin D, β-glucuronidase, acid phosphatase, acid/alkaline DNases and acid/alkaline RNases) was studied in four brain regions (cerebrum, hippocampus, pons and cerebellum) of Wistar rats. The activity of cathepsin D was significantly increased with aging in the four regions. The age-dependent change in activities of acid and alkaline DNases showed the characteristic regional difference, and the ratio of acid to alkaline DNases was increased with aging in all regions. Acid RNase showed the lowest activity in 18-month-old rats, and alkaline RNase activity was decreased with aging. The activity of β-glucuronidase was higher in 2-month-old rats in all of the regions studied. Acid phophatase showed no significant age-dependent change except in pons. The study demonstrated that all of the lysosomal enzyme activities do not change in parallel with aging, and that the age-dependent change showed the characteristic regional difference.  相似文献   
6.
Formalin-fixed paraffin-embedded hippocampal sections of brains with early-onset and late-onset Alzheimer's disease were studied immunohistochemically with antisera against cathepsin D and cathepsin B. In addition to the staining of neuronal perikarya, some of the senile plaques visualized by Bielshowsky silver staining and some of reactive astrocytes were positively stained with the antisera against cathepsin D and cathepsin B in brains with Alzheimer's disease. Abnormal localization of cathepsin D and cathepsin B immunoreactivity in neuronal perikarya was observed in brains with early-onset Alzheimer's disease. These findings demonstrate that the distribution of lysosomal proteases was altered in brains with Alzheimer's disease, suggesting the primary and/or secondary involvement of the lysosomal proteases in the pathological process of Alzheimer's disease.  相似文献   
7.
In a 2-year carcinogenicity study of potassium iodide (KI) in F344/DuCrj rats, squamous cell carcinomas (SCCs) were observed in the salivary glands of 4/40 males and 3/40 females receiving 1000 ppm KI in the drinking water. Ductular proliferation with lobular atrophy was observed at high incidence in the submandibular glands of the high-dose animals, and squamous metaplasia was frequently evident within the proliferative ductules and the larger interlobular ducts. A transition from metaplasia to SCC was apparent. The results suggest that squamous metaplasia in proliferative ductules, occurring secondarily to lobular impairment induced by KI, may develop into SCCs via a non-genotoxic, proliferation-dependent mechanism.  相似文献   
8.
PURPOSE: Recent studies reported that clinical responsiveness to gefitinib was associated with somatic mutation of epidermal growth factor receptor (EGFR) gene in non-small cell lung cancers (NSCLC). Here, we investigated the relationship between EGFR mutation and clinicopathologic features. EXPERIMENTAL DESIGN: EGFR mutational status of 120 NSCLCs was determined mainly in EGFR exons 18 to 21 by direct sequence and correlated with clinicopathologic parameters. RESULTS: EGFR mutations were present in 38 cases (32%) and the majority of mutations were in-frame deletions of exon 19 (19 cases) and a missense mutation in exon 21 (18 cases). EGFR mutations were frequently associated with adenocarcinoma (P < 0.0001), never smoker (P < 0.0001), and female gender (P = 0.0001). Of interest, increasing smoke exposure was inversely related to the rate of EGFR mutation (P < 0.0001). Multivariate analysis showed that smoking and histology were independent variables. Furthermore, gender difference was observed for the mutational location (P = 0.01) dominance of exon 19 for males and exon 21 for females. Twenty-one cases were treated with gefitinib and found that EGFR mutation was significantly related to gefitinib responsiveness (P = 0.002). In addition, median survival times of patients with and without EGFR mutations treated with gefitinib were 25.1 and 14.0 months, respectively. Patients with EGFR mutations had approximately 2-fold survival advantage; however, the difference was not significant. CONCLUSIONS: We show that EGFR mutations were significantly related to histology and smoke exposure and were a strong predictive factor for gefitinib responsiveness in NSCLC.  相似文献   
9.
10.
We evaluated the association between pulse pressure (PP) and cardiovascular risk factors in a screened cohort. Individuals who were receiving medications for hypertension or heart disease, who had no ECG record, or who had a record of arrhythmia were excluded. In total, 8,508 subjects (5,299 men and 3,209 women; age range, 18 to 89 years) were studied. Subjects were divided into four PP classes: PP.1 (PP < or = 40 mmHg, n=2,127), PP.2 (40 < or = PP < or = 44 mmHg, n=2,127), PP.3 (44 < or = PP < or = 50 mmHg, n=2,127) and PP.4 (50 mmHg < or = PP, n=2,127). Multiple regression analysis was used for evaluating the association between PP and cardiovascular risk factor or lifestyle. In men, the regression coefficient was 0.27 for age, 2.50 for diabetes mellitus, 0.33 for uric acid, 0.20 for body mass index, 0.07 for heart rate, -0.83 for current smoking habit and 1.23 for habitual drinking. In women, the regression coefficient was 0.37 for age, 4.09 for diabetes mellitus, 0.42 for body mass index, 0.14 for heart rate, and 0.84 for habitual exercise. In both men and women, PP was significantly increased in association with an increase in the number of risk factors (diabetes mellitus, obesity, current drinking status, heart rate, and hyperuricemia). In conclusion, higher PP was associated with cardiovascular risk factors. These associations were similar in both men and women.  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