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   9056篇
  免费   1077篇
  国内免费   287篇
耳鼻咽喉   134篇
儿科学   161篇
妇产科学   319篇
基础医学   1010篇
口腔科学   154篇
临床医学   866篇
内科学   1192篇
皮肤病学   145篇
神经病学   528篇
特种医学   262篇
外国民族医学   2篇
外科学   579篇
综合类   1518篇
预防医学   649篇
眼科学   1037篇
药学   1050篇
  7篇
中国医学   374篇
肿瘤学   433篇
  2024年   25篇
  2023年   112篇
  2022年   207篇
  2021年   307篇
  2020年   281篇
  2019年   385篇
  2018年   385篇
  2017年   400篇
  2016年   456篇
  2015年   426篇
  2014年   695篇
  2013年   725篇
  2012年   576篇
  2011年   604篇
  2010年   460篇
  2009年   420篇
  2008年   411篇
  2007年   393篇
  2006年   381篇
  2005年   357篇
  2004年   323篇
  2003年   317篇
  2002年   243篇
  2001年   229篇
  2000年   213篇
  1999年   134篇
  1998年   124篇
  1997年   101篇
  1996年   66篇
  1995年   47篇
  1994年   61篇
  1993年   46篇
  1992年   52篇
  1991年   31篇
  1990年   38篇
  1989年   35篇
  1988年   27篇
  1987年   31篇
  1986年   31篇
  1985年   31篇
  1984年   29篇
  1983年   22篇
  1982年   30篇
  1981年   22篇
  1980年   19篇
  1979年   22篇
  1978年   18篇
  1977年   19篇
  1976年   19篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
31.
A combination of the anti-progesterone mifepristone and gemeprostprovides an effective non-surgical method for the inductionof abortion at gestations up to 63 days, achieving completeabortion rates of over 95%. We report our experience with analternate regimen, comprising a reduced dose of mifepristonein combination with vaginal misoprostol. A consecutive seriesof 2000 women requesting early medical abortion at gestationsup to 63 days was studied retrospectively. Each woman receivedmifepristone 200 mg orally, followed 36–48 h later bymisoprostol 800 µg vaginally. Of the 2000 women, 39 (2.0%)aborted completely following administration of mifepristonealone and a further 1912 experienced complete abortion followingadministration of misoprostol (a complete abortion rate of 97.5%).Surgical intervention was required in 49 women (2.5%): for incompleteabortion in 27 (1.4%), for missed abortion in seven (0.4%),for continuing pregnancy in 11 (0.6%) and to exclude ectopicpregnancy in four (0.2%). The surgical intervention rate wassignificantly higher among women at gestations 49 days thanamong those at 49 days (3.3 versus 1.5%, P = 0.0193). The regimenappears as effective, in terms of high complete abortion rateand low continuing pregnancy rate, as any published alternative.This regimen has the benefit of being less costly as the doseof mifepristone is 67% lower and misoprostol is substantiallyless expensive than gemeprost. Additionally, misoprostol doesnot require special transport or storage requirements. As such,the combination of mifepristone and gemeprost.  相似文献   
32.
A mAb J43 has been produced against the product of the mousePD-1 gene, a member of the Ig gene superfamily, which was previouslyisolated from an apoptosis-induced T cell hybridoma (2B4.11)by using subtractive hybridization. Analyses by flow cytometryand immunoprecipitation using the J43 mAb revealed that thePD-1 gene product is a 50–55 kDa membrane protein expressedon the cell surface of several PD-1 cDNA transfectants and 2B4.11cells. Since the molecular weight calculated from the aminoacid sequence is 29,310, the PD-1 protein appears to be heavilyglycosylated. Normal murine lymphoid tissues such as thymus,spleen, lymph node and bone marrow contained very small numbersof PD-1+ cells. However, a significant PD-1+ population appearedin the thymocytes as well as T cells in spleen and lymph nodesby the in vivo anti-CD3 mAb treatment. Furthermore, the PD-1antigen expression was strongly induced in distinct subsetsof thymocytes and spleen T cells by in vitro stimulation witheither anti-CD3 mAb or concanavalin A (Con A) which could leadT cells to both activation and cell death. Similarly, PD-1 expressionwas induced on spleen B cells by in vitro stimulation with anti-IgMantibody. By contrast, PD-1 was not significantly expressedon lymphocytes by treatment with growth factor deprivation,dexamethasone or lipopolysaccharide. These results suggest thatthe expression of the PD-1 antigen is tightly regulated andinduced by signal transduction through the antigen receptorand do not exclude the possibility that the PD-1 antigen mayplay a role in clonal selection of lymphocytes although PD-1expression is not required for the common pathway of apoptosis.  相似文献   
33.
34.
脐血来源的树突状细胞增强CIK细胞的杀伤作用   总被引:7,自引:2,他引:7  
为确认体外诱导出的成熟脐血来源树突状细胞 (CBDC )可以引发强大抗肿瘤免疫反应 ,CBDC培养 12d后用电镜分析形态 ,用流式细胞仪检测其表型。在不同培养时间 ,用3 H TdR掺入法检测CBDC和细胞因子诱导杀伤细胞 (CIK )的扩增功能 ;用MTT法检测被CBDC激活的CIK抗肿瘤活性。结果表明 ,体外诱导出形态典型的DC ,高表达主要组织相容性抗原I、II类分子、CD5 4 ,也表达CD80、CD83、CD1a,不表达CD6 8。体外培养 12d成熟的CBDC ,能使CIK以最高的比率扩增 ,2种细胞最佳混合比为 1∶10时被激活的CIK杀伤BEL 74 0 2肝癌细胞的功能最强 ,最佳效靶比为 80∶1  相似文献   
35.
〔摘要〕 妊娠高血压综合征(妊高征)产科常见的并发症,是引起孕产妇和围产儿死亡的主要原因之一,对其发病原因和机理尚不清楚。一般认为是由环境因素和遗传因素共同作用造成的,目前的研究热点是易感基因与妊高征的关系。本文对内皮型一氧化氮合酶(eNOS)基因和亚甲基四氢叶酸还原酶(MTHFR)基因多态性与妊高征发病的相关性进行了综述。  相似文献   
36.
Pharmacokinetics of a novel oral slow-release form of misoprostol   总被引:1,自引:0,他引:1  
BACKGROUND: The pharmacokinetics of a novel slow-release (SR) misoprostol was studied and compared to conventional misoprostol. METHODS: Thirty-one women, pregnant between 8 and 12 weeks, requesting surgical abortion were randomly allocated to receive orally 400 microg conventional misoprostol, 400 microg SR misoprostol or 800 microg SR misoprostol. Venous blood samples were taken at 0, 30, 60, 120, 240 and 360 min after the administration of misoprostol. Misoprostol acid (MPA) was determined in serum samples using liquid chromatography/tandem mass spectrometry. RESULTS: Serum peak concentration (Cmax) was highest for conventional oral misoprostol. The time to peak concentration (Tmax) was similar for all groups. The area under the curve up to 360 min was similar for conventional and for 800 microg SR misoprostol and significantly greater for these groups compared to 400 microg SR misoprostol (P = 0.013). CONCLUSION: The new SR form of misoprostol demonstrated lower peak levels but longer-lasting elevation in plasma levels compared to conventional oral misoprostol. The AUC for 800 microg SR misoprostol was similar to that of 400 microg of conventional oral misoprostol. SR misoprostol may offer an alternative to repeated administration of oral misoprostol or to vaginal administration.  相似文献   
37.
The lymphotoxin-beta receptor (LTbetaR) pathway is critical for maintenance of organized lymphoid structures and is involved in the development of colitis. To investigate the mechanisms by which LTbetaR activation contributes to the pathology of chronic inflammation we used a soluble LTbetaR-Ig fusion protein as a competitive inhibitor of LTbetaR activation in the mouse model of chronic colitis induced by oral administration of dextran sulphate sodium. Strong expression of LTbeta which constitutes part of the LTalpha(1)beta(2) ligand complex was detected in colonic tissue of mice with chronic colitis. Treatment with LTbetaR-Ig significantly attenuated the development and histological manifestations of the chronic inflammation and reduced the production of inflammatory cytokines such as TNF, IL-1beta, and IL-6. Moreover, LTbetaR-Ig treatment significantly down-regulated mucosal addressin cell adhesion molecule-1 (MAdCAM-1) expression, leading to reduced leucocyte rolling and sticking in postcapillary and collecting venules and reduced extravasation into the intestinal mucosa as quantified by in vivo fluorescence microscopy. Thus, LTbetaR pathway inhibition ameliorates DSS-induced experimental chronic colitis in mice by MAdCAM-1 down-regulation entailing reduced lymphocyte margination and extravasation into the inflamed mucosa. Therefore, a combined treatment with reagents blocking T cell-mediated perpetuation of chronic inflammation such as LTbetaR-Ig together with direct anti-inflammatory reagents such as TNF inhibitors could constitute a promising treatment strategy for chronic colitis.  相似文献   
38.
BACKGROUND: About 70% of childhood asthmatics become free of asthma-related symptoms during adolescence. Little is known about bronchial hyperresponsiveness (BHR) and airway inflammation in young adults with "outgrown" childhood asthma. METHODS: We studied 61 nonsmoking medical students (18 intermittent mild asthmatics, 23 students with outgrown childhood asthma but free of asthma-related symptoms for 10 years (asymptomatic asthmatics) and 20 healthy students). BHR and lung function were measured, and induced sputum samples analyzed for eosinophil count, eosinophilic cationic protein (ECP), granulocyte-macrophage colony stimulating factor (GM-CSF), and tumor necrosis factor-alpha (TNF-alpha). RESULTS: BHR was still present in most asymptomatic asthmatics, but it was milder compared with healthy students. Only three subjects with previous asthma had no BHR and no signs of airway inflammation. Percentages of eosinophil, and ECP, TNF-alpha and GM-CSF concentrations in induced sputum of mild asthmatics and asymptomatic asthma groups were higher than in the healthy group. In asymptomatic asthmatics group, the duration of asthma, sputum eosinophil percentage, and the level of TNF-alpha in sputum correlated significantly with BHR. CONCLUSIONS: Only a few subjects with longstanding asymptomatic asthma could be considered as cured; most asymptomatic asthmatics continued to exhibit BHR and signs of airway inflammation. The outcome of childhood asthma and BHR was associated with the degree of airway inflammation and the duration of childhood asthma.  相似文献   
39.
BACKGROUND: Occupational asthma (OA) can be a debilitating disease even when removal from the workplace is achieved. Today, the "gold standard" in the assessment of OA is the bronchial provocation test (BPT). Induced sputum is a non-invasive method of exploring airway inflammation which can provide additional information about such challenges and thus could be applied in OA diagnosis and monitoring. METHODS: We report the study carried out in a grain worker sensitized to Lepidoglyphus destructor (Ld), who suffered from mild asthma at the workplace. Skin prick test and specific serum IgE were measured. Ld-BPT was performed, and the changes in eosinophil rates, and ECP and tryptase levels in induced sputum were studied 30 min and 18 h after Ld-BPT. We also determined the changes in nonspecific bronchial hyperresponsiveness (NSBH), given as PD20 values. To assess the specificity of the changes, we also carried out sputum induction and methacholine challenge after barley-BPT. RESULTS: An isolated immediate response was obtained with Ld-BPT, while barley-BPT was negative. Induced sputum showed higher tryptase levels 30 min after Ld-BPT, and higher eosinophil and epithelial cell percentages and ECP levels 18 h after Ld-BPT. There was also a decrease in methacholine PD20 values after Ld-BPT. Those changes were not observed after barley-BPT. CONCLUSIONS: The study of eosinophilic and mast-cell markers in induced sputum provides additional knowledge about the inflammatory process occurring in the airways, suggesting that the study of induced sputum should be considered in the assessment of OA.  相似文献   
40.
Quercetin has been shown to have anti-obesity effects, but it is unknown whether these effects can be transmitted from mothers to their progeny. In this study, we investigated whether maternal quercetin consumption during pregnancy has a protective effect on high-fat diet–induced hyper lipid levels and overweight in progeny. Female mice consumed a control diet or a diet containing 1.0% quercetin during breeding. The male progeny were then divided into four groups that were (1) sacrificed at postnatal day 3; (2) born to dams fed the control diet and also fed the control diet (C-C), (3) born to dams fed the control diet and then fed a 30% high-fat diet (C-HF), or (4) born to dams fed the Q-diet and then fed the HF diet (Q-HF). Maternal consumption of quercetin did not affect body weight or blood lipid parameters in either dams or neonates at postnatal day 3. After 13 weeks, the Q-HF group exhibited greater body and liver weights, and higher blood cholesterol levels than the C-HF group. However, the total cholesterol/ high density lipoprotein (HDL)-cholesterol ratios in the Q-HF and C-C groups remained similar. In conclusion, maternal quercetin consumption does not appear to protect the next generation from high-fat diet–induced hyper cholesterol level in the blood and liver, and consequently overweight, but may help regulate the total cholesterol/HDL-cholesterol ratio.  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