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   9909篇
  免费   408篇
  国内免费   76篇
耳鼻咽喉   126篇
儿科学   124篇
妇产科学   138篇
基础医学   1157篇
口腔科学   133篇
临床医学   561篇
内科学   3042篇
皮肤病学   238篇
神经病学   779篇
特种医学   385篇
外科学   1375篇
综合类   26篇
一般理论   3篇
预防医学   246篇
眼科学   143篇
药学   593篇
中国医学   19篇
肿瘤学   1305篇
  2024年   5篇
  2023年   73篇
  2022年   151篇
  2021年   238篇
  2020年   125篇
  2019年   177篇
  2018年   218篇
  2017年   176篇
  2016年   187篇
  2015年   228篇
  2014年   289篇
  2013年   360篇
  2012年   626篇
  2011年   645篇
  2010年   397篇
  2009年   364篇
  2008年   634篇
  2007年   686篇
  2006年   676篇
  2005年   681篇
  2004年   716篇
  2003年   676篇
  2002年   690篇
  2001年   117篇
  2000年   98篇
  1999年   121篇
  1998年   151篇
  1997年   117篇
  1996年   102篇
  1995年   88篇
  1994年   73篇
  1993年   74篇
  1992年   62篇
  1991年   51篇
  1990年   42篇
  1989年   30篇
  1988年   40篇
  1987年   29篇
  1986年   26篇
  1985年   18篇
  1984年   21篇
  1983年   13篇
  1982年   16篇
  1981年   13篇
  1980年   14篇
  1978年   12篇
  1977年   5篇
  1975年   8篇
  1973年   8篇
  1971年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
In vitro tumor growth in a three-dimensional (3D) architecture has been demonstrated to play an important role in biology not only for developmental organogenesis and carcinogenesis, but also for analyses on reconstitution and maintenance in a variety of biological environments surrounding the cells. In addition to providing architectural similarity to living organisms, 3D culture with a radial flow bioreactor (RFB) can also closely mimic the living hypoxic microenvironment under which specific organogenesis or carcinogenesis occurs. The findings of the present study under the RFB culture conditions show that cancer cells underwent a shift from aerobic to hypoxic energy metabolism, in addition to protein expression to maintain the 3D structure. In RFB-cultured cells, protein stability of hypoxia-inducible factor 1 (HIF1) α, a subunit of HIF1, was increased without upregulation of its mRNA. Under these conditions, PHD2, HIF-prolyl-4-hydroxy-lase 2 and a HIF1 downstream enzyme, were stabilized without affecting the mRNA levels via downregulation of FK506-binding protein 8. PHD2 accumulation, which occurred concomitant with HIF1 stabilization, may have compensated for the lack of oxygen under hypoxic conditions to regulate the HIF levels. 3D-culture-induced overexpression of carbonic anhydrase (another representative HIF downstream enzyme) was found to occur independently of cell density in RFB--cultured cells, suggesting that the RFB provided an adequately hypoxic microenvironment for the cultured cells. From these results, it was hypothesized that the key factors are regulatory molecules, which stabilize and degrade HIF molecules, thereby activating the HIF1 pathway under a hypoxic milieu.  相似文献   
992.
993.
In a novel paradigm of T cell differentiation, type 17 T helper (Th17) cells may play a significant role in endometriosis, a chronic inflammatory disease. However, the mechanism regulating the accumulation of Th17 cells in endometriotic tissues remains unknown. We hypothesized that Th17 cells migrate to endometriotic tissues through an interaction of the chemokine CC chemokine ligand (CCL)20 and its receptor CCR6. Using endometriotic tissues from women with endometriosis, we demonstrated, by flow cytometry, that Th17 cells in endometriotic tissues express CC chemokine receptor (CCR)6. Immunohistochemistry also revealed that CCL20 was expressed in the epithelial cells and stromal cells beneath the epithelium of endometriotic tissues. CCR6+ cells were small and round and scattered in the stroma in which abundant CCL20+ cells were detected. CCL20 caused selective migration of Th17 cells in the peripheral blood in a migration assay. IL-1β, TNF-α, and IL-17A increased the secretion of CCL20 in cultured endometriotic stromal cells. Inhibitors of p38- and p42/44-MAPKs, and stress-activated protein kinase/c-Jun kinase suppressed the secretion of CCL20 increased by IL-1β, TNF-α, and IL-17A. This suggests that the CCL20/CCR6 system is involved in the migration of Th17 cells to endometriotic tissues and that proinflammatory cytokines contribute to the development of endometriosis via up-regulation of CCL20 secretion from endometriotic stromal cells.  相似文献   
994.
We performed this study to determine whether both eating cadmium (Cd)-polluted rice and drinking and/or cooking with Jinzu River water are associated with renal tubular dysfunction. A multiple logistic regression analysis of retrospective data indicated that both factors may contribute to this condition. Estimated threshold values of rice Cd concentration in men were 0.13–0.27 ppm and 0.09–0.18 ppm in women, without adjustment for use of Jinzu River water. The additional influence of drinking and/or cooking with Jinzu River water was estimated to be about 0.008 ppm.  相似文献   
995.
Background: The magnetocardiogram (MCG) is a promising medical tool for detecting and visualizing abnormal cardiac electrical activation in heart-disease patients. However, there is no large-scale MCG database of healthy subjects, and there is little knowledge of gender- and age-related influences on MCG data.
Methods and Results: We obtained MCG data from 869 subjects (554 men, 315 women) using a conventional 64-channel MCG system, which covers the whole heart. Electrocardiogram (ECG) data were also obtained; 464 people (268 men, 196 women) were identified as a normal group using ECG data. Time intervals (PQ, QRS, QT, and QTc), current distributions (maximum current vector (MCV), and the total current vector (TCV)) of MCG data of the 464 normal subjects were analyzed to obtain basic MCG parameters.
Although mean values of PQ and QRS intervals of the male subjects were slightly longer than those of the female subjects, no intervals were correlated with gender or age. The correlation between PQ intervals of ECG and those of MCG was better than the correlation between QRS and QT intervals of ECG and those of MCG. Both MCV and TCV angles were much smaller than the electrical-axis angle in ECG. Although TCVs of the QRS and T waves were stable, the women's mean T-wave-TCV angles significantly increased with age. The maximum amplitude of the P wave was about 1.7 pT, and the value of the QRS complex was about 20–25 pT. Moreover, the T-wave amplitude decreases with age.
Conclusion: The MCG standard space-time parameters determined here provide a normal range for MCG parameters.  相似文献   
996.
997.
Associations of objective measures of trauma exposure with psychological sequelae following motor vehicle accidents (MVA) were examined in a Japanese population. Impact and injury severity of 93 MVA victims was assessed using on-the-scene in-depth investigations measured by the Injury Severity Score (ISS), barrier equivalent speed (BES), and change in velocity during the impact (Delta-v). Results showed that ISS, BES, and Delta-v were not related to posttraumatic stress symptoms (PTSS) or psychiatric symptoms at 5 and 14 months after the MVA. Subjective measures (e.g., perceived life risk, persistent medical problems) were significantly related to psychological sequelae. These findings suggest that the objective measures of trauma exposure are not associated directly with PTSS or psychiatric symptoms after an MVA.  相似文献   
998.
999.
1000.
Background  The aim of this study was to evaluate the prognostic value of tumor diameter in gastric cancer. Methods  The study group comprised a series of 1215 patients who underwent curative gastrectomy. The appropriate tumor diameter cutoff value was determined. Prognostic factors were evaluated by univariate and multivariate analyses. Results  The tumor diameter cutoff value was 100 mm. Multivariate analysis showed that tumor site, macroscopic appearance, tumor diameter, depth of invasion, and presence of lymph node metastasis independently affected prognosis in all patients. Multivariate analysis of patients with larger tumors identified depth of invasion as an independent prognostic factor. A comparison between patients with smaller and larger tumors showed marked differences in the survival of those with stage II, IIIA, and IIIB tumors. A comparison of clinicopathological factors between stage II and III patients revealed that tumors occupying the entire stomach, ill-defined, undifferentiated, and serosa-penetrating tumors, and peritoneal metastases were far more frequent in patients with larger tumors. Conclusions  Tumor diameter in gastric cancer is a reliable prognostic factor that might be a candidate for use in the staging system. To improve outcomes for patients with tumors ≥100 mm in diameter, it is necessary to establish therapeutic strategies for peritoneal metastasis, particularly in stage II and III tumors.  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