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   4500篇
  免费   236篇
  国内免费   15篇
耳鼻咽喉   48篇
儿科学   145篇
妇产科学   31篇
基础医学   657篇
口腔科学   79篇
临床医学   256篇
内科学   1005篇
皮肤病学   47篇
神经病学   389篇
特种医学   251篇
外科学   814篇
综合类   11篇
预防医学   65篇
眼科学   28篇
药学   316篇
中国医学   25篇
肿瘤学   584篇
  2023年   28篇
  2022年   31篇
  2021年   89篇
  2020年   43篇
  2019年   69篇
  2018年   69篇
  2017年   61篇
  2016年   77篇
  2015年   81篇
  2014年   95篇
  2013年   128篇
  2012年   232篇
  2011年   255篇
  2010年   142篇
  2009年   125篇
  2008年   247篇
  2007年   265篇
  2006年   268篇
  2005年   266篇
  2004年   281篇
  2003年   263篇
  2002年   259篇
  2001年   71篇
  2000年   63篇
  1999年   74篇
  1998年   73篇
  1997年   73篇
  1996年   59篇
  1995年   53篇
  1994年   58篇
  1993年   54篇
  1992年   59篇
  1991年   70篇
  1990年   50篇
  1989年   48篇
  1988年   49篇
  1987年   53篇
  1986年   54篇
  1985年   43篇
  1984年   53篇
  1983年   45篇
  1982年   24篇
  1981年   39篇
  1980年   22篇
  1979年   24篇
  1978年   21篇
  1977年   14篇
  1975年   13篇
  1974年   16篇
  1973年   13篇
排序方式: 共有4751条查询结果,搜索用时 593 毫秒
91.
Although asymmetric development of the ovary and the oviduct is a unique characteristic in birds, the mechanism of asymmetric development still remains unclear. Recently, degradation of extracellular matrix has been suggested as an important factor related to the regression of the Müllerian duct in mammals. The present study was conducted to examine a possible role of metalloproteinase-2 (MMP-2) in the regression of the right Müllerian duct in the developing chicken embryo. Morphological changes in the Müllerian ducts were studied on day 15 of incubation and mRNA expresseion of MMP-2 was studied on days 12, 15, and 18 of incubation. Morphological observation demonstrated the disappearance of basement membrane in the right Müllerian duct which undergoes the regression. RT-PCR analysis showed that MMP-2 mRNA expression of the right Müllerian duct increased on days 15 and 18 of incubation coincidently with the time of regression. In the right Müllerian duct, regression was prevented by diethylstilbestrol treatment on day 4 of incubation and a coincident decrease in MMP-2 expression was observed when compared to the control group. These results suggest that MMP-2 may be involved in the regression of the right Müllerian duct in the female embryos of the chicken.  相似文献   
92.
B lymphocytes and epithelial cells are the only cell types known to be infected with Epstein-Barr virus (EBV) in normal individuals. Rarely, EBV also infects other cells, including natural killer (NK) cells, almost always in the context of fatal leukaemias or lymphoproliferative disorders. We report on a 6-year-old previously healthy girl who developed fevers and liver function abnormalities for 3 months. The peripheral blood revealed an abnormal expansion of large granular lymphocytes, comprising 24% of the white blood cells. Flow cytometric analysis of the peripheral blood mononuclear cells showed an abnormal increase of CD16-positive NK cells, 62% of which were EBV-infected by in situ EBER-1 hybridization. The circulating B cells were normal in number, but 18% were infected with EBV by in situ EBER-1 hybridization. Approximately 2 years after resolution of all symptoms and continued good health, 35% of the circulating mononuclear cells were EBV-infected, indicative of persistent expansion of EBV-infected cells. We conclude that abnormal expansions of EBV-infected NK and B cells can be associated with a chronic benign course.  相似文献   
93.
94.
Summary The chronic effects of the oral administration of OPC-8212 (3,4-DIHYDRO-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)-quinolinone) on resting hemodynamics and exercise capacity were assessed in 15 patients with congestive heart failure (NYHA II–IV). Doses of 30 or 60 mg per day were given per os over 3.0 weeks on average (range 2–6 weeks). Multigated radionuclide ventriculography and multistage exercise testing were performed before and during OPC-8212 therapy to assess the changes in left ventricular volume and exercise capacity respectively. Systolic blood pressure showed a slight increase (from 123±3 to 129±4 mmHg) during OPC-8212 therapy, while heart rate was unchanged (69±3 vs 67±3 beats/min). The left ventricular end-diastolic volume index decreased from 127±9 to 107±7 ml/m2, and ejection fraction and the P/V index (the ratio of peak systolic pressure to left ventricular end-systolic volume index) increased during OPC-8212 therapy (from 27%±3% to 30%±4% and from 1.5±0.2 to 2.0±0.3 mmHg/ml/m2 respectively). NYHA functional class was improved in 9 of 15 patients, and the average peak work load achieved during exercise testing increased from 27±6 to 47±7 W. No significant adverse effect was observed in any patient. These results indicate that OPC-8212 enhances the inotropic state and, hence, reduces heart size with no change in heart rate. Moreover, it increases exercise capacity. Thus, OPC-8212 is an inotropic agent with promise for application in the long-term treatment of congestive heart failure.  相似文献   
95.
The relationship between Helicobacter pylori (H. pylori) and gastric diseases (e.g. peptic ulcer, MALT lymphoma, and stomach cancer) has been widely accepted. Recent studies have also suggested an association between H. pylori infection and idiopathic thrombocytopenic purpura (ITP). In this study, an H. pylori eradication treatment was administered to 20 ITP patients and elucidated for its effectiveness. Among those 20 patients, H. pylori infection was confirmed in 17 (85%) through a C14 urea breath test, a rapid urease test, or a culture examination of a biopsied sample obtained by gastrointestinal endoscopy. Although the other 3 were negative to H. pylori, the H. pylori eradication treatment was also attempted because no other effective treatments had been established at the time of this study. In the H. pylori eradication treatment, lansoprazole (LPZ) 60 mg bid, amoxicillin (AMPC) 1500 mg bid, and clarithromycin (CAM) 400 mg bid were given to each patient for 7 days. For 4 cases, CAM was replaced with metronidazole (MNZ) 750 mg bid. The patients whose H. pylori infection was not eradicated after the first treatment received the re-eradication treatment with LPZ 60 mg bid, AMPC 1500 mg bid, and MNZ 750 mg bid for 7 days. After the treatments, the success of eradicating H. pylori was confirmed in all 17 H. pylori positive patients. In addition, platelet recovery was obtained in 11/20 patients (55%), which included 2 H. pylori negative patients and 2 patients whose H. pylori eradication was not successful after the first treatment. No relationship was found between the eradication effectiveness and the following clinical parameters: age, gender, previous therapies, disease duration, presence of anti-nucleus antibody, endoscopic atrophic change in the stomach, or kinds of antibiotics used for the treatment. These results support the efficacy of an H. pylori eradication treatment for ITP patients. A noteworthy result of this study was that an increase of platelet count was observed not only in H. pylori positive ITP patients, but also in 2 out of 3 H. pylori negative ITP patients after H. pylori eradication. Further studies are required to elucidate the efficacy of H. pylori eradication therapy in the patients negative for H. pylori.  相似文献   
96.
Thrombophilic dysfibrinogen Tokyo V was identified in a 43-year-old man with recurrent thromboembolism. Based on analyses of the patient fibrinogen genes, the amino acid sequence of the aberrant fibrinogen peptide, and deglycosylation experiments, fibrinogen Tokyo V was shown to have an amino acid substitution of gamma Ala327Thr and possibly extra glycosylation at gamma Asn325 because the mutation confers the N-linked glycosylation consensus sequence Asn-X-Thr. The mutation resulted in impaired function and hypofibrinogenemia (hypodysfibrinogen). Polymerization of fibrin monomers derived from patient fibrinogen was severely impaired with a partial correction in the presence of calcium, resulting in very low clottability. Additionally, a large amount of soluble cross-linked fibrin was formed upon thrombin treatment in the presence of factor XIII and calcium. However, Tokyo V-derived fibrin was resistant to degradation by tissue plasminogen activator (tPA)-catalyzed plasmin digestion. The structure of Tokyo V fibrin appeared severely perturbed, since there are large pores inside the tangled fibrin networks and fiber ends at the boundaries. Taken together, these data suggest that Tokyo V fibrin clots are fragile, so that fibrinolysis-resistant insoluble fibrin and soluble fibrin polymers may be released to the circulation, partly accounting for the recurrent embolic episodes in the patient.  相似文献   
97.
98.
99.
100.
Journal of Thrombosis and Thrombolysis - Pulmonary thromboembolism (PTE) is one of the leading causes of maternal mortality. We previously reported that possible contamination of amniotic fluid...  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