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   87544篇
  免费   45023篇
  国内免费   61篇
耳鼻咽喉   1700篇
儿科学   4559篇
妇产科学   858篇
基础医学   17523篇
口腔科学   6816篇
临床医学   13306篇
内科学   25772篇
皮肤病学   7765篇
神经病学   14378篇
特种医学   2418篇
外科学   15238篇
综合类   66篇
一般理论   22篇
预防医学   5700篇
眼科学   1424篇
药学   6419篇
中国医学   1147篇
肿瘤学   7517篇
  2023年   144篇
  2022年   331篇
  2021年   1840篇
  2020年   5419篇
  2019年   11240篇
  2018年   10649篇
  2017年   11779篇
  2016年   12493篇
  2015年   12426篇
  2014年   12446篇
  2013年   13060篇
  2012年   5297篇
  2011年   5361篇
  2010年   9506篇
  2009年   5730篇
  2008年   2801篇
  2007年   1720篇
  2006年   1559篇
  2005年   1221篇
  2004年   1176篇
  2003年   1124篇
  2002年   1130篇
  2001年   1110篇
  2000年   956篇
  1999年   506篇
  1998年   111篇
  1997年   68篇
  1996年   55篇
  1995年   74篇
  1994年   49篇
  1993年   44篇
  1992年   108篇
  1991年   111篇
  1990年   105篇
  1989年   95篇
  1988年   70篇
  1987年   61篇
  1986年   50篇
  1985年   67篇
  1984年   47篇
  1983年   28篇
  1979年   36篇
  1978年   31篇
  1975年   24篇
  1974年   33篇
  1973年   39篇
  1971年   25篇
  1970年   26篇
  1967年   26篇
  1966年   34篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
992.
Dynamic contrast‐enhanced MRI (DCE MRI) has been used to study tumor response to treatment for many years. In this study, the modified full width at half‐maximum (mFWHM), calculated from the wash‐in slope histogram, is proposed as a parameter for the evaluation of changes in tumor heterogeneity which respond to radiotherapy. Twenty‐five patients with brain tumors were evaluated and divided into the nonresponder group (n = 11) and the responder group (n = 14) according to the Response Evaluation Criteria in Solid Tumors (RECIST). All selected tumors were evaluated by mFWHM ratios of post‐ to pre‐therapy (the ratio was defined as the therapeutic mFWHM ratio, TMR). The changes in kurtosis of the histograms and the averaged Ktrans within a tumor were also calculated for comparison. The receiver operating characteristic analysis and Kaplan–Meier curves were used to examine the diagnosis ability. The TMR values were significantly higher in nonresponders than in responders (p < 0.001). When compared with the other two parameters, the proposed method also demonstrated better sensitivity and specificity. When adopting the TMR for the estimation of prognosis after therapy, there was a significant difference between the population survival curves. In conclusion, the derived mFWHM reflects tumor heterogeneity, and the ability to depict patient survival probability from TMR corresponds well with that from RECIST. The results reveal that, in brain tumors, progression may be exhibited not only by tumor size, but also by tumor heterogeneity. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
993.
994.
The relationship between consumption of cruciferous vegetables (CV) and risk of gastric cancer has been investigated by many studies, but remains controversial. We carried out a meta‐analysis to summarize available evidence from epidemiological studies on this point. Relevant published reports of CV intake and gastric cancer were identified using MEDLINE (PubMed), EMBASE, and Web of Science databases through to the end of September 2012. We pooled the relative risk from individual studies using a fixed‐ or random‐effects model and carried out heterogeneity and publication bias analyses. Sixteen case–control and six prospective studies were included in our analysis. When all studies were pooled, we yielded a significantly inverse association between CV (relative risk = 0.81; 95% confidence interval, 0.75–0.88) intake and gastric cancer risk, with little heterogeneity (= 27.27, P = 0.292, I2 = 12.0%). Specific analysis for cabbage intake yielded similar result. When separately analyzed, case–control studies of CV intake yielded significant results and the results of prospective studies showed borderline statistical significance. Moreover, significant results were consistent for high‐quality studies, for North American, European, and Asian studies, for studies on males, and for studies on non‐cardia gastric cancer. Findings from this meta‐analysis provide evidence that high intake of CV was inversely associated with the risk of gastric cancer and non‐cardia gastric cancer in humans. Further studies on other specific CV, food preparation methods, and stratified results by anatomic cancer site and histological type should be extended in the future.  相似文献   
995.
996.
997.
998.
It has been reported that EMMPRIN is involved in the regulation of immune response and the induction of MMPs production by fibroblasts. The aim of this study was to describe the intestinal gene expression and protein production of EMMPRIN, MMP23 and MMP10 in patients with ulcerative colitis (UC) and Crohn’s disease (CD) and compared them with a control group. Gene expression of EMMPRIN, MMP10 and MMP23B was measured by RT‐PCR. In order to determine EMMPRIN and MMP protein expression, colonic tissues were immunostained. The results of the study showed EMMPRIN gene expression was upregulated in rectal mucosa from active (a)UC versus aCD patients (= .045), remission (r)CD group (P = .0009) and controls (P < .0001). We detected differences between rUC and aCD (P = .004), rCD (P < .0001) or control group (P < .0001). EMMPRIN showed a higher expression in mucosa (intraepithelial lymphocytes), submucosa and adventitia (endothelial cells) from aCD patients. MMP23 levels were increased in aUC and aCD compared to rUC and rCD and the control group (P = .0001). EMMPRIN+/MMP23+─expressing cells were localized mainly in mucosa, muscular and adventitia from active UC patients. MMP10 gene expression was increased in aUC versus CD patients and the control group (P = .0001). MMP10 gene expression is associated with inflammation in UC patients (P = .0001, r= .585). EMMPRIN+/MMP10+─producing cells were found mainly in all intestinal layers and perivascular inflammatory infiltrates from aUC patients. In conclusion, EMMPRIN, MMP23 and MMP10 were upregulated in patients with active UC versus remission UC , CD and control groups suggesting that, they are involved in the inflammatory process.  相似文献   
999.
In daily practice, the presence of inflammation in gastric biopsies prompts a mental algorithm, an early question being whether the lesion present is Helicobacter‐associated. If Helicobacter organisms are not found, then there is a further algorithm, governed by the predominant type of inflammatory cells present, and the presence of other features such as intraepithelial lymphocytosis, a subepithelial collagen band, granulomas, coexisting chronic inflammation, focality, and superimposed reactive changes including erosions and ulcers. Each of these generates its own differential diagnosis. If no inflammation is present, then the two major changes specifically looked for are the changes associated with hypergastrinaemia, by far the most common cause of which is treatment with proton pump inhibitors, and reactive changes. These may be present with and without accompanying inflammation, and, when the epithelial changes dominate, the term gastropathy is preferred. In this article, we present an approach to non‐Helicobacter inflammation and gastropathies.  相似文献   
1000.
In patients with Mansoni schistosomiasis, it is fundamental to evaluate the disease morbidity, which is reflected by the severity of periportal fibrosis (PPF) and parameters of portal hypertension, as analyzed by ultrasonography (US). This study aimed to evaluate the morbidity of schistosomiasis by hepatic and splenic point shear-wave elastography (pSWE) and relate this to US parameters. The PPF pattern, the diameter of the portal and splenic veins and the size of the spleen were evaluated by US. Then, liver and spleen pSWEs were assessed in 74 patients using the same equipment. As the PPF pattern progressed, the splenic pSWE values significantly increased. Significant correlations between splenic pSWE, the longitudinal and transverse lengths of the spleen and the diameters of the portal and splenic veins were observed. These findings, however, were not observed through hepatic pSWE. In conclusion, the splenic pSWE has the potential for assessing morbidity in schistosomiasis mansoni.  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