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   28678篇
  免费   2517篇
  国内免费   1006篇
耳鼻咽喉   133篇
儿科学   533篇
妇产科学   287篇
基础医学   8682篇
口腔科学   459篇
临床医学   2416篇
内科学   5080篇
皮肤病学   890篇
神经病学   940篇
特种医学   280篇
外国民族医学   12篇
外科学   2201篇
综合类   3918篇
现状与发展   5篇
预防医学   897篇
眼科学   206篇
药学   1609篇
  1篇
中国医学   498篇
肿瘤学   3154篇
  2024年   11篇
  2023年   277篇
  2022年   310篇
  2021年   694篇
  2020年   682篇
  2019年   773篇
  2018年   738篇
  2017年   773篇
  2016年   841篇
  2015年   1093篇
  2014年   1591篇
  2013年   1863篇
  2012年   1553篇
  2011年   2175篇
  2010年   1828篇
  2009年   1962篇
  2008年   1739篇
  2007年   1744篇
  2006年   1658篇
  2005年   1442篇
  2004年   1339篇
  2003年   1193篇
  2002年   992篇
  2001年   797篇
  2000年   684篇
  1999年   578篇
  1998年   442篇
  1997年   406篇
  1996年   371篇
  1995年   441篇
  1994年   351篇
  1993年   280篇
  1992年   148篇
  1991年   138篇
  1990年   71篇
  1989年   40篇
  1988年   23篇
  1987年   15篇
  1986年   12篇
  1985年   20篇
  1984年   31篇
  1983年   20篇
  1982年   23篇
  1981年   13篇
  1980年   7篇
  1979年   6篇
  1978年   4篇
  1977年   2篇
  1976年   2篇
  1973年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
Glucose and nutrient uptake is essential in supporting T cell activation and is increased upon CD3/CD28 stimulation. As T cells from pleural effusions secondary to lung cancer show impaired function, we hypothesized that these cells might have altered expression of nutrient transporters. Here, we analysed by flow cytometry the expression of the transferrin receptor CD71, amino acid transporter CD98 and glucose transporter Glut1 and glucose uptake in pleural effusion‐derived T cells from lung cancer patients, after stimulation via CD3/CD28 under normoxia or hypoxia (2% O2). We compared the response of T cells from pleural effusions secondary to lung cancer with that of T cells from nonmalignant effusions. In memory T cells from both groups, anti‐CD3/CD28‐stimulation under normoxia upregulated CD98 and CD71 expression (measured as median fluorescence intensity, MFI) in comparison with anti‐CD3‐stimulation. Costimulation under hypoxia tended to increase CD98 expression compared to CD3‐stimulation in memory T cells from both groups. Remarkably, in the cancer group, memory T cells stimulated via CD3/CD28 under hypoxia failed to increase CD71 and Glut1 expression levels compared to the cells receiving anti‐CD3 stimulation, a phenomenon that contrasted with the behaviour of memory T cells from nonmalignant effusions. Consequently, glucose uptake by memory T cells from the cancer group was not increased after CD3/CD28 stimulation under hypoxia, implying that their glycolytic metabolism is defective. As this process is required for inducing an antitumoural response, our study suggests that memory T cells are rendered dysfunctional and are unable to eliminate lung tumour cells.  相似文献   
85.
CD4+ T cell immunotherapy has potential for treatment in HIV‐infected patients. A large number of expanded CD4+ T cells and confirmation of functional‐related phenotypes are required for ensuring the successful outcomes of treatment. Freshly isolated CD4+ T cells from healthy donors were activated with anti‐CD3/28‐coated magnetic beads at different bead‐to‐cell ratios and cultured in the absence and presence of IL‐2 supplementation for 3 weeks. Fold expansion, cell viability, growth kinetic and lymphocyte subset identities were determined. Data demonstrated that a 1:1 bead‐to‐cell ratio rendered the highest expansion of 1044‐fold with 88% viability and 99.5% purity followed by the 2:1 and 0.5:1 ratios. No significant difference in proliferation and phenotypes was found between non–IL‐2 and IL‐2 supplementation groups. Several specific surface molecule expressions of the expanded cells including chemokine receptors, adhesion molecules, co‐stimulatory molecules, activation molecules, maturation markers, cytokine receptors and other molecules were altered when compared to the unexpanded cells. This optimized expansion protocol using the 1:1 bead‐to‐cell ratio of anti‐CD3/28‐coated magnetic beads and culture condition without IL‐2 supplementation provided the satisfactory yield with good reproducibility. Specific surface molecule expressions of the expanded cells presented potential roles in proliferation, differentiation, homeostasis, apoptosis and organ homing.  相似文献   
86.
87.
BackgroundAutoimmune hepatitis is a chronic inflammatory disease, the abnormal immunological function is the main pathogenesis. Interleukin-34 is a newly identified cytokine that shares the same receptor as colony stimulating factor-1.MethodsWe used interleukin-34 knockout and wild-type mice in a Con A-induced hepatitis model and cocultured RAW264.7 macrophage cells with interleukin-34. We then detected associated inflammatory cytokine and chemokine levels to elucidate the role of interleukin-34.ResultsIn this study, we found that the loss of interleukin-34 resulted in higher sensitivity to Con A-induced hepatitis. RAW264.7 macrophage cells were able to differentiate to the M2 phenotype upon interleukin-34 stimulation.ConclusionsWe conclude that interleukin-34 may protect the liver from Con A-mediated hepatitis by driving M2 macrophage polarization and suppressing inflammation.  相似文献   
88.
BackgroundMixed adenoneuroendocrine carcinoma (MANEC) is currently included in the category of neuroendocrine carcinomas but the therapeutically management is not yet defined.AimsTo present the immunohistochemical (IHC) features of the epithelial mesenchymal transition (EMT) of MANEC.Materials and methodsThe clinicopathological features of 13 consecutive cases of MANEC (6 gastric and 7 colorectal) were correlated with the IHC expression of the biomarkers E-cadherin, β-catenin, N-cadherin, vimentin, maspin, CD44 and S100. In all of the cases open surgery was performed.ResultsAll of the cases showed microsatellite stable status, expressed E-cadherin and membrane β-catenin in both components (neuroendocrine and adenocarcinoma) and were negative for N-cadherin, vimentin and S-100. The colorectal MANECs were negative for maspin. In gastric MANECs, maspin showed cytoplasm positivity in the neuroendocrine component and nuclear translocation in the adenocarcinoma cells. CD44 was positive in all of the cases, in both components. No tumor buddings were identified. Three of the 13 patients survived for at least 32 months, all of them showing lymphatic emboli but not lymph node metastases. Pure neuroendocrine lymph node metastases were seen in only four of the cases: one from stomach, two of the ascending colon and two cases of the upper rectum.ConclusionsGastrointestinal MANEC is a microsatellite stable tumor with nodular growth, which components might originate from a CD44-positive stem-like precursor cell. Lymph node status remains the most reliable prognostic parameter and agressivity seems to not be influenced by tumor budding degree or EMT-related features. The histologic aspect of metastatic component (neuroendocrine versus adenocarcinoma) should be included in the histopathological reports and might be used for establishing the proper-targeted therapy of MANEC.  相似文献   
89.
Papillary thyroid carcinoma (PTC) is the most common differentiated thyroid cancer in children; and the follicular variant is the second most common variant after the classic subtype. The histological appearance of follicular variant of papillary thyroid cancer (FVPTC), can be mimicked by benign follicular nodules. Pediatric pathologists encountering such lesions with FVPTC-like appearance may err on diagnosing the benign lesions as malignant. In adult patients, several immunohistochemical markers have emerged recently as a useful adjunct to distinguish differentiated thyroid carcinomas from benign follicular lesions. We undertook an inter-institutional retrospective study to establish the diagnostic utility of immunohistochemical staining for HBME-1, Galectin-3 and CD56 in differentiating FVPTC from its benign mimics, follicular adenoma and adenomatoid nodules, in children. Our specific aim of the project was to define the sensitivity and specificity of the three antibodies in FVPTC. Based on institutional diagnoses, a total of 66 cases were obtained: 32 FVPTC and 34 benign follicular nodules that comprised of 23 follicular adenoma and 11 adenomatoid nodules. Five investigators, who were blinded to the original diagnoses, independently reviewed the slides following pre-determined criteria and semi-quantitatively scoring the immunohistochemical staining. The immunohistochemical staining revealed that a combination of positive HBME-1 and negative CD56 result gave 100% specificity and positive predictive value in distinguishing FVPTC from benign follicular nodules. However, the antibody combination suffered from a lower sensitivity (50%). We used a cutoff of 25% positivity of tumor cells in determining positivity of tumor cells to an antibody. In conclusion, our study found a very high specificity and strong positive predictive value for the combination of HBME-1 and CD56 immunohistochemical stains in distinguishing FVPTC from benign follicular lesions.  相似文献   
90.
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