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   26982篇
  免费   2379篇
  国内免费   965篇
耳鼻咽喉   127篇
儿科学   517篇
妇产科学   267篇
基础医学   8562篇
口腔科学   402篇
临床医学   2354篇
内科学   4700篇
皮肤病学   872篇
神经病学   794篇
特种医学   266篇
外国民族医学   12篇
外科学   1586篇
综合类   3780篇
现状与发展   5篇
预防医学   859篇
眼科学   200篇
药学   1450篇
  1篇
中国医学   444篇
肿瘤学   3128篇
  2024年   36篇
  2023年   251篇
  2022年   450篇
  2021年   664篇
  2020年   597篇
  2019年   653篇
  2018年   653篇
  2017年   682篇
  2016年   771篇
  2015年   1011篇
  2014年   1387篇
  2013年   1698篇
  2012年   1440篇
  2011年   2001篇
  2010年   1702篇
  2009年   1861篇
  2008年   1666篇
  2007年   1647篇
  2006年   1559篇
  2005年   1403篇
  2004年   1257篇
  2003年   1132篇
  2002年   950篇
  2001年   767篇
  2000年   661篇
  1999年   577篇
  1998年   551篇
  1997年   417篇
  1996年   424篇
  1995年   426篇
  1994年   333篇
  1993年   251篇
  1992年   137篇
  1991年   130篇
  1990年   64篇
  1989年   39篇
  1988年   20篇
  1987年   9篇
  1986年   5篇
  1985年   7篇
  1984年   12篇
  1983年   5篇
  1982年   5篇
  1981年   8篇
  1979年   3篇
  1978年   1篇
  1977年   1篇
  1973年   1篇
  1906年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Phosphaturic mesenchymal tumors (PMTs) are the most typical cause of tumor-induced osteomalacia (TIO) associated with mesenchymal neoplasms. Specifically, TIO is attributed to the production of phosphatonins, such as fibroblast growth factor 23 (FGF23), participating in the homeostasis of phosphate. Although immunohistochemistry (IHC) for FGF23 showed characteristic positive staining in PMTs, FGF23 antibodies that can be used for the reliable diagnosis of PMTs are hard to obtain in common pathology laboratories. Somatostatin receptor 2A (SSTR2A) has been previously proposed as an alternatively useful marker for the diagnosis of PMTs. However, SSTR2A is not commonly utilized in pathological laboratories. The CD56 marker is a useful alternative that is comparable to SSTR2A and is similar considering the sensitivity. Even in cases of PMTs originating in the bones, ethylenediaminetetraacetic acid-based decalcification for tissue processing does not seem to affect the IHC of CD56. As CD56 immunopositivity in mesenchymal tumors is limited, it also has some degree of specificity for PMTs. Thus, when PMTs are suspected, the use of CD56 is recommended.  相似文献   
992.
Chemokine receptor CXCR3 has been proved to play an important role in tumorigenesis and tumor progression in many malignancies, but its precise efficacy on gastric cancer (GC) has not been evaluated yet. The present study was aimed to explore the correlation of chemokine receptor CXCR3 with tumor-infiltrating lymphocytes (TILs) and prognosis in advanced gastric cancer (GC). Expression of CXCR3 and CD4+, CD8+ TILs was conducted in 192 advanced GC specimens and 48 corresponding paracancerous tissues by immunohistochemical (IHC) analysis. CXCR3 expression in GC tissues was significantly higher than that in paracancerous tissues (P<0.001) and CD8+, CD4+ TILs infiltration increased with high CXCR3 expression (P=0.032 and P<0.001, respectively). Our study showed significantly lower CXCR3 expression in patients with greater tumor invasion depth and lymph node metastasis compared with patients with lesser tumor invasion depth and without lymph node metastasis (P=0.002 and P=0.001, respectively). Univariate analysis indicated that patients with high CXCR3 expression and high CD8+ TILs infiltration had longer overall survival (OS) (log-rank test, P<0.001 and P=0.002, respectively). Univariate and multivariate analyses indicated that CXCR3 expression was an independent prognostic factor for OS (P=0.002). The present study suggested that CXCR3 expression was upregulated in advanced GC and was associated with increased CD4+, CD8+ TILs infiltration and improved OS. Therefore, CXCR3 overexpression is implicated as a favorable prognostic biomarker in human advanced GC.  相似文献   
993.
Shadow cell differentiation (SCD), commonly found in cutaneous pilomatricoma (PMX), has been said to be extremely rare in extracutaneous tumors and its morphogenesis has not been clarified yet. In the present study, 25 cases of endometrial adenoacanthoma were examined with special reference to SCD and with immunohistochemistry for beta-catenin and CD10. Shadow cell nests (SCNs) were observed in 2 out of 5 cases of adenocarcinoma with squamoid morules and all of 4 cases of adenocarcinoma with squamous differentiation and morules, but not in any cases of adenocarcinoma with squamous differentiation. SCNs were just adjacent to morules with or without a mutual transition. Immunohistochemical examination revealed nuclear accumulation of beta-catenin and expression of CD10 in the squamoid morules around SCNs. These results indicate that SCNs are derived from squamoid morules in endometrial adenoacanthoma, and established a link between matrical basaloid cells in PMX and squamoid morules in endometrial adenoacanthoma, as common original tissues, showing nuclear accumulation of beta-catenin and expression of CD10, of SCNs. It seems that SCD is not so uncommon as previously estimated in endometrial adenoacanthoma.  相似文献   
994.
Objectives: To investigate CD147 and matrix metalloproteinase-9 (MMP-9) expressions in type II/III adenocarcinoma of esophagogastric junction (AEG), and their clinicopathological significances. Methods: Seventy-four patients clinically and pathologically diagnosed with type II/III AEG were analyzed, each undergoing radical total gastrectomy and Roux-en-Y esophagojejunostomy. The avidin streptavidin-perosidase immunohistochemistry technique was used to detect CD147 and MMP-9 in type II/III AEGs and 20 para-tumor controls, and their correlations with clinicopathological data and their reciprocal relationship were then analyzed. Kaplan-Meier survival analysis was conducted to reveal their prognostic significances. SPSS 20.0 was used for data analysis. A difference was statistically significant with P < 0.05, and very significant with P < 0.01. Results: In type II/III AEG CD147 and MMP-9 were mainly expressed on cellular membrane of in tumor cell cytoplasm. MMP-9 expression was significantly stronger at tumor-stroma junction and front edge of invasion. Their positive rates were significantly higher in malignant tissues than para-tumor tissues (P < 0.01 for both). There existed a significant positive correlation between both expressions (P < 0.05). They were significantly more highly expressed in cancers with lymphatic metastasis (P < 0.01 for both), at TNM III/IV stages (P < 0.01 for both), and with poor differentiation grade (P < 0.05 for both). Higher CD147 and MMP-9 expression rates were correlated with inferior postsurgical survivals (P < 0.05 for both). Conclusions: CD147 and MMP-9 could be novel biomarkers for type II/III AEG, and potentially predict tumor progression and prognosis. They are worth further investigation.  相似文献   
995.
Aims and background: To investigate the expressions of TET2 mRNA in bone marrow CD3+ and CD34+ cells of the patients with myelodysplastic syndromes (MDS) and to study the effect of silencing TET2 by small interfering RNA (siRNA) on the biological characteristics of CD34+ cells. Methods: CD3+ and CD34+ cells were sorted by magnetic activated cell-sorting system from bone marrow of MDS patients and controls. The mRNA expressions of TET2 in bone marrow CD3+ and CD34+ cells of 28 MDS patients and 20 controls were detected by qPCR. The silencing effect of RNA interference (RNAi) on TET2 expression in CD34+ bone marrow cells of normal control was identified by qPCR and Western blot analysis. The cell cycle kinetics and cell apoptosis were then detected by flow cytometry. Results: The expression of TET2 mRNA in CD3+ and CD34+ cells was down-regulated in MDS compared with that in controls [(0.16±0.11) vs. (1.05±0.32) (P<0.001); (0.58±0.26) vs. (1.25±0.94) (P<0.005)]. The siRNA targeting TET2 suppressed the expression of TET2 in normal CD34+ cells. Meanwhile, the proliferation activity was significantly enhanced [G0/G1: (87.82±8.25)% vs. (92.65±7.06)% and (93.60±5.54)%, P<0.05; S: (11.50±8.31)% vs. (6.92±7.04)% and (5.95±5.53)%, P<0.05] and the apoptosis rate was declined [(21.28±9.73)% vs. (26.17±9.88)% and (26.20±9.78)%] in the cells which transfected with TET2 siRNA as compared to those in the cells transfected with scrambled siRNA and control cells. Conclusions: The TET2 expression of in CD3+ and CD34+ cells of MDS patients was decreased. Suppression of TET2 expression renders the CD34+ cells harboring more aggressive phenotype. This preliminary finding suggests that CD34+ cells lowering expression of TET2 may play an oncogenic role on myeloid tumor and CD3+ T cells of MDS patients may be derived from the malignant clone.  相似文献   
996.
Platelets play a known role in the maintenance of vascular homeostasis, but these cells are emerging as important cellular mediators of acute and chronic inflammatory diseases. Platelets are key elements in the pathogenesis of acute and chronic liver disease associated with hepatitis B virus (HBV) infection by promoting the accumulation of virus-specific CD8+ T cells and nonspecific inflammatory cells into the liver parenchyma. This review discusses major platelet functions in immune and inflammatory responses, with an emphasis on recent pre-clinical studies that suggest that the inhibition of platelet activation pathways represent an alternative therapeutic strategy with potential use in the reduction of virus-specific T cell-mediated chronic inflammation, liver fibrosis and hepatocellular carcinoma in patients who are chronically infected with HBV.  相似文献   
997.
Regulatory T (Treg) cells may participate in mediating a suppressive microenvironment that blunts successful anti-tumor immunotherapy. Recent studies show that CD8+ Treg cells might impede effective immune responses to established tumors. However, there is limited research regarding CD8+ Treg cells in ovarian cancer (OC) patients. Here, we investigated CD8+ Treg cells in OC patients and their in vitro induction. The immunohistochemistry of tumor-infiltrating lymphocytes revealed a significant correlation between the intratumoral CD8+ T cells and the forkhead box p3 (Foxp3)+ cells in the intraepithelial and stromal areas of advanced OC tissues. We examined the expression of Treg markers in CD8+ T cells from the peripheral blood and fresh tumor tissues of OC patients using flow cytometry. Our results indicated an increase in the CD8+ Treg cell subsets of OC patients compared with those in patients with benign ovarian tumors and healthy controls, including an increased expression of CD25, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and Foxp3 and decreased CD28 expression. To demonstrate whether the tumor microenvironment could convert CD8+ effector T cells into suppressor cells, we used an in vitro transwell culturing system. Compared with the CD8+ T cells cultured alone, the CD8+ Treg cells induced in vitro by coculture with SK-OV-3/A2780 showed increased CTLA-4 and Foxp3 expression and decreased CD28 expression. In addition, the in vitro-induced CD8+ Treg cells inhibited naïve CD4+ T-cell proliferation, which was partially mediated through TGF-β1 and IFN-γ. Our study suggests that CD8+ Treg cells were increased in OC patients and could be induced in vitro, which may be the way that tumors limit antitumor immunity and evade immune surveillance.  相似文献   
998.
One important aspect of mesenchymal stromal cells (MSCs)-mediated immunomodulation is the recruitment and induction of regulatory T (Treg) cells. However, we do not yet know whether MSCs have similar effects on the other subsets of Treg cells. Herein, we studied the effects of MSCs on CD8+CD28 Treg cells and found that the MSCs could not only increase the proportion of CD8+CD28 T cells, but also enhance CD8+CD28T cells'' ability of hampering naive CD4+ T-cell proliferation and activation, decreasing the production of IFN-γ by activated CD4+ T cells and inducing the apoptosis of activated CD4+ T cells. Mechanistically, the MSCs affected the functions of the CD8+CD28 T cells partially through moderate upregulating the expression of IL-10 and FasL. The MSCs had no distinct effect on the shift from CD8+CD28+ T cells to CD8+CD28 T cells, but did increase the proportion of CD8+CD28 T cells by reducing their rate of apoptosis. In summary, this study shows that MSCs can enhance the regulatory function of CD8+CD28 Treg cells, shedding new light on MSCs-mediated immune regulation.  相似文献   
999.
Ulcerative colitis (UC) is a chronic gastrointestinal disorder eliciting occurrence of colorectal cancer, the third most common human malignancy. The diagnosis of UC is based on clinical symptoms combined with typical findings on endoscopy, radiology, and ultimately pathology. We investigated the variation trend of CD4+CD29+T cells together with MPO, VCAM-1 in different periods of rat UC model and UC patients. We also evaluated the relationship between CD4+CD29+T cells and disease severity. UC model was induced by administering DNCB liquid and acetate solution. We found upregulated expression of CD4+CD29+T cells in both peripheral blood and colon from rats, and a similar trend for MPO and VCAM-1 in colon (P < 0.05); the expression was especially enhanced in UC rats at two weeks after the model was established (P < 0.01). Such upregulation was also indicated in active and remission UC patients as compared to the healthy and enteritis groups (P < 0.05), with the highest expression level detected in the active UC patients (P < 0.01). Pearson correlation analysis showed a positive correlation of CD4+CD29+T cells in rat and human peripheral blood with DAI score (rrat = 0.712, rhuman = 0.677, P < 0.01), and MPO in colon (rrat = 0.514, rhuman = 0.682, P < 0.05). These results suggest that CD4+CD29+T cells may act as major effector cell subsets in persistent inflammatory responses for UC and that infiltration into colon inflammation may be induced by the combination of VCAM-1 and CD29.  相似文献   
1000.
Aims: Polymorph neutrophils are the predominant inflammatory cells and play a crucial role on the pathogenesis of myocardial injury at the early stage of acute myocardial infarction (AMI). However, the precursors and the differentiation of neutrophils are not fully understood. Here we explored the role of CD11b+Gr-1+ myeloid-derived suppressor cells (MDSCs) on myocardial injury in the absence and presence of advanced glycation end-products (AGEs) in a mice model of AMI. Methods and Results: Male C57BL/6J mice were selected. Fluorescent actived cell sortor (FACS) data demonstrated significantly increased CD11b+Gr-1+ MDSCs both in peripheral blood circulation and in the ischemic myocardium at 24 hours post AMI. Quantitative-real-time PCR results also revealed significantly upregulated CD11b and Ly6G mRNA expression in the ischemic myocardium. AGEs treatment further aggravated these changes in AMI mice but not in sham mice. Moreover, AGEs treatment also significantly increased infarction size and enhanced cardiomyocyte apoptosis. The mRNA expression of pro-inflammatory cytokine IL-6 and iNOS2 was also significantly increased in AMI + AGEs group compared to AMI group. Conclusion: These data suggest enhanced infiltration of MDSCs by AGEs contributes to aggravated myocardial injury in AMI mice, which might be one of the mechanisms responsible for severer myocardial injury in AMI patients complicating diabetes.  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