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   580篇
  免费   27篇
  国内免费   26篇
耳鼻咽喉   1篇
儿科学   45篇
妇产科学   9篇
基础医学   35篇
口腔科学   24篇
临床医学   55篇
内科学   146篇
皮肤病学   4篇
神经病学   6篇
特种医学   116篇
外科学   74篇
综合类   4篇
预防医学   13篇
眼科学   5篇
药学   72篇
肿瘤学   24篇
  2022年   3篇
  2021年   4篇
  2020年   3篇
  2019年   2篇
  2018年   6篇
  2017年   2篇
  2016年   4篇
  2015年   7篇
  2014年   6篇
  2013年   11篇
  2012年   7篇
  2011年   4篇
  2010年   8篇
  2009年   17篇
  2008年   12篇
  2007年   24篇
  2006年   9篇
  2005年   19篇
  2004年   10篇
  2003年   14篇
  2002年   11篇
  2001年   13篇
  2000年   14篇
  1999年   14篇
  1998年   40篇
  1997年   48篇
  1996年   58篇
  1995年   42篇
  1994年   33篇
  1993年   30篇
  1992年   12篇
  1991年   10篇
  1990年   8篇
  1989年   19篇
  1988年   18篇
  1987年   12篇
  1986年   10篇
  1985年   11篇
  1984年   9篇
  1983年   5篇
  1982年   7篇
  1981年   5篇
  1980年   5篇
  1979年   4篇
  1978年   2篇
  1977年   6篇
  1976年   6篇
  1975年   8篇
  1954年   1篇
排序方式: 共有633条查询结果,搜索用时 62 毫秒
101.
102.
����ϵͳ�����������ε���״�ͽ�չ   总被引:5,自引:0,他引:5  
胆道系统恶性肿瘤包括胆管癌和胆囊癌 ,前者主要指原发于肝内、肝门部和远端肝外胆管的恶性肿瘤。至今胆系肿瘤仍依TNM分类法分为 0~Ⅳ期。 0期 :为原位癌 ;Ⅰ期 :肿瘤局限于粘膜层、肌层 ;Ⅱ期 :出现局部浸润 ;Ⅲ期 :在Ⅰ或Ⅱ期基础上肿瘤累及邻近组织或肝十二指肠韧带上淋巴结 ;Ⅳ期 :出现肝脏等器官受累或远处转移或出现以下之一区域的淋巴结转移 ,如胰周、十二指肠周、肝门周、腹腔及肠系膜。1 诊断胆系恶性肿瘤的诊断 ,主要依靠临床表现、实验室检查以及影象学检查。临床表现特异性不强 ,其中最基本的表现为胆道梗阻症状 ,同时可…  相似文献   
103.
Background: Gastroesophageal reflux disease (GERD) is a common condition and may frequently lead to dysphagia and respiratory symptoms. The aim of this study was to investigate the effects of medical and surgical therapy to control these symptoms. Methods: Eighty GERD patients with either dysphagia or respiratory symptoms were studied by means of a detailed symptom questionnaire, upper gastrointestinal endoscopy, esophageal manometry, 24-h esophageal pH monitoring and a barium esophagogram. All patients had been receiving medical therapy with proton-pump inhibitors and cisapride for 6 months. After withdrawal of medical therapy and relapse of GERD, 62 patients decided to undergo anti-reflux surgery (laparoscopic Nissen fundoplication in 19 and laparoscopic partial posterior fundoplication in 43 patients). Symptoms were assessed prior to treatment, at 6 months following medical therapy and 6 months after surgery. Results: Heartburn and esophagitis were effectively treated by medical and surgical therapy. Dysphagia was improved in all patients following surgery but only in 27% of patients following medical therapy. Improvement of respiratory symptoms was found in 86% of patients following surgery but only in 14% following medical therapy. Improvement of regurgitation was registered only following surgical therapy. Conclusions: Since medical treatment is likely to fail in GERD patients with complex symptoms such as dysphagia, regurgitation and respiratory symptoms, the need for surgery arises in these patients and may be the only successful treatment in the long term. Received: 5 March 1999 Accepted: 7 July 1999  相似文献   
104.
目的:中性粒细胞粘附在缺血再灌注损伤中有非常重要的作用。本文用SD大鼠趾长屈肌缺血再灌注损伤模型,观察L一粘附素单抗LAM1—116在缺血再灌注损伤中的作用。方法:30只SD大鼠被均分为2组:LAM1—116组和生理盐水对照组。每只大鼠的一侧趾长屈肌作为正常对照,另外一侧进行 3 h缺血 4 h再灌注。结果:LAM1— 116组实验侧的髓过氧化物酶为正常的2倍(2.3±2.2),生理盐水对照组则为正常的28倍(27.5±11.7)(P<0.001);LAM1—116组的湿重比(1.10± 0.10)、疲劳肌力(77. 1%±12.1%)与对照组相比(分别为 1. 23± 0. 10和 49. 7%± 9 .3%)明显改善(P< 0.05);组织学上,LAM1—116组的中性粒细胞局部浸润显著减少,水肿减轻。结论:通过 L-粘附素单克隆抗体 LAM1— 116阻断 L-粘附素的功能,可以有效地降低中性粒细胞在再灌注肌肉中的浸润,防止组织水肿,从而改善肌肉的功能。  相似文献   
105.
106.
马蓝的化学成分研究   总被引:15,自引:0,他引:15  
Seven compounds have been isolated from the whole plant of Strobilanthes cusia (Nees) O. Ktze. Three of them are triterpenes (Ⅰ~Ⅲ), two are indole alkaloids (Ⅳ, Ⅴ), two are quinazolinone alkaloids (Ⅵ, Ⅶ). On the basis of spectral analysis and physicochemical properties, their structures were established as lupeol (Ⅰ), betulin (Ⅱ), lupenone (Ⅲ), indigo (Ⅳ), indirubin (Ⅴ), 4 (3H)-quinazolinone (Ⅵ), 2, 4 (1H, 3H)-quinazolinedione (Ⅶ). Ⅵ and Ⅶ were found from natural plant for the first time.The results of the pharmacological tests demonstrate that compound Ⅴ has anticancer activity and compound Ⅵ has hypotensive action. Compound Ⅶ can be quantitatively determined by HPLC, which may serve as a quality control standard for materia medica and its preparations. Compounds Ⅵ and Ⅶ have been confirmed by means of synthesis.  相似文献   
107.

BACKGROUND AND PURPOSE

Changes in airway smooth muscle (ASM) phenotype may contribute to the pathogenesis of airway disease. Platelet-derived growth factor (PDGF) switches ASM from a contractile to a proliferative, hypo-contractile phenotype, a process requiring activation of extracellular signal-regulated kinase (ERK) and p70S6 Kinase (p70S6K). The effects of cAMP-elevating agents on these processes is unknown. Here, we investigated the effects of cAMP elevation by prostaglandin E2 (PGE2) and the activation of the cAMP effectors, protein kinase A (PKA) and exchange protein activated by cAMP (Epac) on PDGF-induced phenotype switching in bovine tracheal smooth muscle (BTSM).

EXPERIMENTAL APPROACH

Effects of long-term treatment with the PGE2 analogue 16,16-dimethyl-PGE2, the selective Epac activator, 8-pCPT-2′-O-Me-cAMP and the selective PKA activator, 6-Bnz-cAMP were assessed on the induction of a hypo-contractile, proliferative BTSM phenotype and on activation of ERK and p70S6K, both induced by PDGF.

KEY RESULTS

Treatment with 16,16-dimethyl-PGE2 inhibited PDGF-induced proliferation of BTSM cells and maintained BTSM strip contractility and contractile protein expression in the presence of PDGF. Activation of both Epac and PKA similarly prevented PDGF-induced phenotype switching and PDGF-induced activation of ERK. Interestingly, only PKA activation resulted in inhibition of PDGF-induced phosphorylation of p70S6K.

CONCLUSIONS AND IMPLICATIONS

Our data indicate for the first time that both Epac and PKA regulated switching of ASM phenotype via differential inhibition of ERK and p70S6K pathways. These findings suggest that cAMP elevation may be beneficial in the treatment of long-term changes in airway disease.  相似文献   
108.
PURPOSE: We investigate the patterns of failure in the treatment of glioblastoma(GBM) based on clinical target volume(CTV) margin size,dose delivered to the site of initial failure,and the use of temozolomide and intensity-modulated radiotherapy(IMRT).METHODS: Between August 2000 and May 2010,161 patients with GBM were treated with radiotherapy with or without concurrent temozolomide.Patients were treated with CTV expansions that ranged from 5 to 20 mm using a shrinking field technique.Patterns of failure and time to progression and overall survival were compared based on CTV margin,use of temozolomide,and use of IMRT.Kaplan Meier analysis was used to estimate survival times,and χ test was used for comparison of cohorts.RESULTS: For patients treated with 5-,10-,and 15-to 20-mm CTV,79%,77%,and 86% experienced failures in the 60 Gy volume,respectively.Forty-eight percent,55%,and 66% of patients with 5-,10-,and 15-to 20-mm CTV experienced failures in the 46 Gy volume,respectively.There was no statistical difference between patients treated with 5-,10-,15-to 20-mm margins with regard to 60 Gy failure(P=0.76),46 Gy failure(P=0.51),or marginal failure(P=0.73).Eighty percent of patients receiving temozolomide experienced failures in the 60 Gy volume.There was no increased likelihood of marginal failures in patients receiving IMRT(P =0.97).CONCLUSIONS: Modern treatment techniques including use of concurrent temozolmide,limited CTV margin size,and IMRT have not greatly changed the patterns of failure of GBM.  相似文献   
109.
110.
BACKGROUND: Cellular immunity has been implicated in periodontal destruction for over 25 years. Studies in the 1970s used lymphocyte transformation and lympho-kine assays to establish a role for cell-mediated mechanisms in periodontal disease. lmmunohistological studies subsequently showed that the formation of gingivitis followed a similar pattern to the formation of a delayed type hypersensitivity reaction. Further functional studies suggested that a T cell/macrophage immunoregulatory imbalance may exist locally in the periodontitis lesion and that this imbalance may be antigen specific. RECENT EVIDENCE: More recently, T cell subsets have been dichotomised on the basis of their cytokine profiles. In general, Thl cells produce IL-2 and IFN-gamma while Th2 cells produce IL-4, IL-5 and IL-6. The major function of Th l cells is to mediate delayed type hypersensitivity. In contrast the major function of Th2 cells is to provide B cell help.
HYPOTHESIS: A model for periodontal disease has now been developed based on this functional dichotomy which provides a framework for the study of cytokine profiles in periodontal disease. Early studies in this context have demonstrated a higher proportion of IL-4 producing cells in periodontitis tissues suggesting a role for Th2 cells in the progressive lesion. Clonal studies have shown that the selection of a particular cytokine profile is not antigen dependent and that differences may be due to the host susceptibility although this remains to be determined.
CONCLUSION: These emerging data clearly establish a role for cell-mediated mechanisms in the control of periodontal destruction and raise the possibility that in the future cytokine therapy for the treatment of periodontal disease in susceptible subjects may become a viable option.  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