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   5699篇
  免费   244篇
  国内免费   31篇
耳鼻咽喉   138篇
儿科学   67篇
妇产科学   28篇
基础医学   752篇
口腔科学   122篇
临床医学   363篇
内科学   1278篇
皮肤病学   105篇
神经病学   323篇
特种医学   182篇
外科学   1178篇
综合类   27篇
预防医学   151篇
眼科学   47篇
药学   496篇
中国医学   30篇
肿瘤学   687篇
  2022年   62篇
  2021年   81篇
  2020年   48篇
  2019年   57篇
  2018年   95篇
  2017年   69篇
  2016年   90篇
  2015年   92篇
  2014年   128篇
  2013年   133篇
  2012年   240篇
  2011年   269篇
  2010年   143篇
  2009年   134篇
  2008年   210篇
  2007年   241篇
  2006年   263篇
  2005年   272篇
  2004年   271篇
  2003年   267篇
  2002年   274篇
  2001年   176篇
  2000年   203篇
  1999年   196篇
  1998年   63篇
  1997年   53篇
  1996年   58篇
  1995年   55篇
  1994年   55篇
  1993年   42篇
  1992年   123篇
  1991年   127篇
  1990年   119篇
  1989年   112篇
  1988年   119篇
  1987年   121篇
  1986年   125篇
  1985年   103篇
  1984年   69篇
  1983年   79篇
  1982年   31篇
  1979年   45篇
  1977年   36篇
  1974年   32篇
  1973年   42篇
  1972年   38篇
  1971年   36篇
  1970年   27篇
  1969年   29篇
  1968年   34篇
排序方式: 共有5974条查询结果,搜索用时 15 毫秒
101.
Adeno-associated virus (AAV) vector system has several useful advantages with regard to in vitro and in vivo gene transfer. However, their usages have been limited by cumbersome and labor-intensive vector production in the traditional method. To overcome limitations in AAV production, in this report, we explored the possibility of generating AAV packaging cell line, 293T R/C.VA.E2A.E4. cells, by using lentivirus-mediated transduction of Rep/Cap gene of AAV-2, VA RNA, E2A, and E4 genes of Ad5 into 293T cells. In packaging cell lines, it is important that supply of the AAV vector can be stably performed for long time. We showed that the 293T R/C.VA.E2A.E4. cells have stably maintained the transduced components after more than 10 passages and yielded high-titer AAV vectors, and the titer of AAV vectors did not decline even if culture of the packaging cells was continued for long time. The Rep/Cap and E4 gene products caused no remarkable cytotoxicity. The 293T R/C.VA.E2A.E4. cells might be able to tolerate the Rep/Cap and E4 gene products, or have less copy numbers of the Rep/Cap and E4 genes than the traditional method. Moreover, we showed that the AAV vectors derived from 293T R/C.VA.E2A.E4. cells infected the primary human CD34+ haematopoietic progenitor cells with high efficiency (50-70%). In the 293T R/C.VA.E2A.E4. cells, the AAV vectors can be generated by the transfection of one AAV vector plasmid, and large-scale AAV production can be easily achieved. It is important that cumbersome, variable, and costly transfection is avoided.  相似文献   
102.
The systemic hemodynamic and coronary dilative responses to sublingual nitroglycerin were studied in patients receiving transdermal nitroglycerin. A total of 48 patients with coronary artery disease were divided into 4 groups: 12 patients receiving 1 tablet of sublingual nitroglycerin without transdermal nitroglycerin (Group 1), 12 patients receiving 1 tablet of sublingual nitroglycerin with 12-hour-daily intermittent therapy of transdermal nitroglycerin (Group 2), 12 patients receiving 1 tablet of sublingual nitroglycerin with continuous therapy of transdermal nitroglycerin (Group 3), and 12 patients receiving 2 tablets of sublingual nitroglycerin with continuous therapy of transdermal nitroglycerin (Group 4). Before and during administration of sublingual nitroglycerin, aortic pressure, left ventricular pressure, and coronary artery diameter were examined at diagnostic cardiac catheterization in all patients. During sublingual nitroglycerin, the decreases of aortic systolic pressure and left ventricular end-diastolic pressure were greater in Group 1, 2, and 4 than in Group 3. Dilation of coronary arteries by sublingual nitroglyerin tended to be greater in Group 1, 2, and 4 than in Group 3. Thus, the effects of sublingual nitroglycerin for the relief of ischemia might be more prominent in patients with intermittent therapy of transdermal nitroglycerin than in those with continuous therapy. The increased dose of sublingual nitroglycerin for the relief of ischemia might be more effective in patients with continuous therapy of transdermal nitroglycerin.  相似文献   
103.
ABSTRACT— To clarify the discrepancy in hepatitis B surface antigen (HBsAg) subtypes present in the serum and liver, as well as among hepatocytes, liver specimens which were resected from 37 HBsAg-positive patients with hepatocellular carcinoma (HCC) were examined. We evaluated HBsAg and the subtypic determinants of HBsAg and hepatitis B core antigen (HBcAg) using the peroxidase-antiperoxidase (PAP) staining method. Hepatitis B antigens were more frequently detected in small tumors (HBsAg in 67%, HBcAg in 40%) than in large ones (HBsAg in 36%, HBcAg in 14%). The prevalence of each subtypic determinant in the HBsAg positive non-tumorous vs. tumorous areas was 100% vs. 67% in a, 100% vs. 57% in d, 100% vs. not tested in y, 100% vs. 53% in r and 25% vs. 0% in w (a, d, y, r and w represent subtypic determinants). There was virtually no difference in a set of subtypic determinants between the serum and liver. However, there were some variations in a set of subtypic determinants among the hepatocytes. On the other hand, liver tissue of compound subtype adyr in serum contained both cells with a,d,r and with a,y,r as well as a few cells with a,d,y,r. These findings suggest that HBV genomes in hepatocytes of type B chronic liver disease may differ genetically among cells even in the same liver tissue.  相似文献   
104.
Vasospastic angina in Kawasaki disease   总被引:1,自引:0,他引:1  
We report vasospastic angina in a young female with a history of Kawasaki disease (KD). She had had KD at the age of 20 months. Selective coronary angiograms at the age of 4 years revealed no coronary aneurysms or stenosis. She remained symptom-free for 29 years, but coronary angiograms at the age of 31 years revealed a localized 50% stenosis of the left anterior descending artery. Aging in addition to endothelial dysfunction of the coronary arterial wall resulting from acute KD vasculitis may underlie the late development of angina. This is the first case which is reported as vasospastic angina after KD. The occurrence of acute coronary syndromes in patients with a history of KD should be investigated carefully from now on. Attention should be paid to coronary endothelial dysfunction after KD in adults.  相似文献   
105.
Conversion of T4 to T3 was studied in normal, Graves', and neoplastic thyroid tissues obtained at surgery. Homogenates of human thyroid follicular adenoma and carcinomas were incubated with [125I]T4 and dithiothreitol (DTT) at 37 C for 60 min under N2 gas. T3 formation was assessed by measuring [125I]T3 formed, using paper chromatography. In the second series of experiments, the suspensions of the 100,000 X g pellet of normal thyroid tissues adjacent to the tumor and Graves' thyroid tissues were incubated with unlabeled T4 and DTT at 37 C for 60 min under N2 gas. T3 generated was measured by RIA. T3 generation in the thyroid tissue was dependent on incubation time, amount of the tissue used, concentration of DTT, temperature, and pH. Propylthioracil inhibited T3 formation, while methimazole had no effect. A kinetic study with the homogenate of a thyroid adenoma and 100,000 X g pellet suspensions of two normal and three Graves' thyroids gave apparent Km values of 2.7, 4.9, and 4.1 microM for T4, respectively, and Vmax values of 0.8, 3.0, and 10.9 pmol T3/mg protein.min, respectively. Conversion of T4 to T3 was observed in two of three tumor tissues studied and was markedly enhanced in Graves' thyroid tissues (mean +/- SE, 11.9 +/- 2.0 pmol/mg protein.min) compared to that of normal thyroid tissues (3.2 +/- 0.6 pmol/mg protein.min; P less than 0.01). It is concluded that T4 is enzymatically converted to T3 in normal and Graves' thyroids and differentiated thyroid neoplasms. Moreover, enhanced conversion of T4 to T3 was found in Graves' thyroid tissue.  相似文献   
106.
107.
A successful surgical palliative procedure, consisting of an arterial switch operation, pulmonary artery banding, and arch repair, was performed in a neonate with Taussig-Bing anomaly and aortic arch interruption, subaortic stenosis, and multiple muscular ventricular septal defects. Such anatomical complexity made treatment difficult. This palliative procedure allows future biventricular repair.  相似文献   
108.
109.
The role of active oxygen species and lipidperoxidation in the pathogenesis of duodenal ulcersinduced by mepirizole was investigated in rats. Oraladministration of mepirizole (200 mg/kg) resulted in ulcer lesions in the proximal duodenum.Thiobarbituric acid-reactive substances (TBA-reactivesubstances), an indicator of lipid peroxidation, alsosignificantly increased in the duodenal mucosa.Myeloperoxidase (MPO) activity in the duodenal mucosa, a signof polymorphonuclear leukocyte (PMN) accumulation,significantly increased. Combination treatment withpolyethylene glycol-modified Serratia Mn-SOD andcatalase significantly decreased the size of the ulcersand TBA-reactive substances in the duodenal mucosa.Allopurinol, a xanthine oxidase inhibitor, also reducedthe size of duodenal ulcers. Both the size of the ulcers and the increase in TBA-reactivesubstances in the duodenal mucosa were significantlylower in PMN-depleted rats. Mepirizole increased thesurface expression of adhesion molecule CD18 on PMNs in vitro. These results suggest that lipidperoxidation, mediated by active oxygen speciesgenerated from xanthine oxidase and PMNs, plays animportant role in the pathogenesis of duodenal ulcersinduced by mepirizole.  相似文献   
110.
Introduction: Although successful ablation of ventricular tachycardia (VT) is feasible in arrhythmogenic right ventricular cardiomyopathy (ARVC), long-term recurrence is common. The aim of this study was to assess the usefulness of a change in the isolated delayed component (IDC) as an endpoint of the catheter ablation in ARVC.
Methods and Results: Eighteen patients (48 ± 11 years) with ARVC were studied. Detailed endocardial mapping of the right ventricle (RV) was performed during sinus rhythm. IDCs were recorded in 16 patients and the latest IDCs were related to the VT circuit. Catheter ablation was carried out in the areas with the IDCs. At the end of the session, the IDC was electrically dissociated in one, disappeared in five, exhibited second-degree block in one, was significantly delayed (≥50 ms) in three, and remained unchanged in six. The change in the IDC was correlated with the change in the type II/III late potentials in the signal-averaged electrocardiography (ECG) and the inducibility of the clinical VT after the ablation. During a follow-up of 61 ± 38 months, VT recurred in six. The patients with a changed IDC had a significantly lower VT recurrence than those with no IDC or an unchanged IDC (P < 0.02).
Conclusion: In patients with ARVC, (1) the IDCs during sinus rhythm are related to the clinical VT and can be a target for the ablation, (2) a change in the IDC can be used as an endpoint, and (3) qualitative analyses of the serial signal-averaged ECGs may be useful for the long-term follow-up.  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