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   47002篇
  免费   3679篇
  国内免费   2371篇
耳鼻咽喉   299篇
儿科学   869篇
妇产科学   733篇
基础医学   6041篇
口腔科学   930篇
临床医学   3879篇
内科学   7597篇
皮肤病学   461篇
神经病学   2981篇
特种医学   1173篇
外国民族医学   13篇
外科学   4028篇
综合类   8540篇
现状与发展   6篇
预防医学   1501篇
眼科学   2284篇
药学   6794篇
  8篇
中国医学   2366篇
肿瘤学   2549篇
  2024年   31篇
  2023年   366篇
  2022年   593篇
  2021年   1091篇
  2020年   961篇
  2019年   926篇
  2018年   1060篇
  2017年   1154篇
  2016年   1292篇
  2015年   1401篇
  2014年   2390篇
  2013年   3114篇
  2012年   2637篇
  2011年   3210篇
  2010年   2681篇
  2009年   2899篇
  2008年   3043篇
  2007年   3102篇
  2006年   2816篇
  2005年   2729篇
  2004年   2473篇
  2003年   2307篇
  2002年   1977篇
  2001年   1736篇
  2000年   1494篇
  1999年   1212篇
  1998年   990篇
  1997年   781篇
  1996年   564篇
  1995年   430篇
  1994年   334篇
  1993年   226篇
  1992年   155篇
  1991年   107篇
  1990年   99篇
  1989年   69篇
  1988年   66篇
  1987年   52篇
  1986年   52篇
  1985年   80篇
  1984年   81篇
  1983年   57篇
  1982年   40篇
  1981年   47篇
  1980年   35篇
  1979年   31篇
  1978年   25篇
  1977年   9篇
  1976年   10篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 291 毫秒
11.
12.
Intravascular papillary endothelial hyperplasia or Masson's tumour is a non-neoplastic vascular lesion of reactive character. It is a rare diagnosis, clinically non-specific and with diverse locations. It is essential to take it into consideration and make a differential diagnosis with malignant vascular tumours such as angiosarcoma. Pathological study is fundamental for diagnosis. Treatment consists of complete resection of the tumour, including sufficiently wide margins to avoid recurrence.The case reported is an exceptional event, because of the pelvic location of the Masson's tumour that was diagnosed as part of the surgical staging of an ovarian cancer.  相似文献   
13.
BackgroundIn patients with melanoma, sentinel lymph node (SLN) status is pivotal for treatment decisions. Current routine for SLN detection combines Technetium99m (Tc99) lymphoscintigraphy and blue dye (BD). The primary aim of this study was to examine the feasibility of using a low dose of superparamagnetic iron oxide (SPIO) injected intracutaneously to detect and identify the SLN, and the secondary aim was to investigate if a low dose of SPIO would enable a preoperative MRI-evaluation of SLN status.MethodsPatients with melanoma of the extremities were eligible. Before surgery, a baseline MRI of the nodal basin was followed by an injection of a low dose (0.02–0.5 mL) of SPIO and then a second MRI (SPIO-MRI). Tc99 and BD was used in parallel and all nodes with a superparamagnetic and/or radioactive signal were harvested and analyzed.ResultsFifteen patients were included and the SLNB procedure was successful in all patients (27 SLNs removed). All superparamagnetic SLNs were visualized by MRI corresponding to the same nodes on scintigraphy. Micrometastatic deposits were identified in four SLNs taken from three patients, and SPIO-MRI correctly predicted two of the metastases. There was an association between MRI artefacts in the lymph node and the dose SPIO given.DiscussionIt is feasible to detect SLN in patients with melanoma using a low dose of SPIO injected intracutaneously compared with the standard dual technique. A low dose of SPIO reduces the lymph node MRI artefacts, opening up for a non-invasive assessment of SLN status in patients with cancer.  相似文献   
14.
Purpose: Enterovirus 71 (EV71) is one of the main pathogens causing hand, foot and mouth disease, which could even induce severe brain damage in some patients. As the underlying mechanism of the invasion and replication process still remains largely unknown, we investigated the role of candidate proteins expressed during EV71 invasion in human brain microvascular endothelial cells (HBMECs) to delineate the pathophysiological mechanism of EV-71 infection. Materials and Methods: Ninety-one candidate EV71-associated proteins which could bind the major capsid protein (viral protein 1 [VP1]) of EV71 on the HBMEC were identified by applying an analysis of glutathione-S-transferase pull-down coupling with liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS). Seventy-eight kDa glucose-regulated protein 78 (GRP78) binding to the VP1 protein was further validated by co-immunoprecipitation, immunofluorescence and western blot analysis. To explore the role of GRP78 in EV71 infection, GRP78 was knocked down and overexpressed in HBMEC and was verified by TCID50 assay. Results: LC-ESI-MS/MS-identified 91 proteins were subjected to gene ontology analysis, and on molecular and biological function analysis revealed GRP78 act as an important binding protein in mediating EV71 infection. In addition, immunofluorescence demonstrated the co-localisation of GRP78 and VP1 in cytoplasm of the infected HBMEC. The TCID50 assay showed that knockdown of GRP78 could attenuate the replication capacity of EV71 in HBMEC, and the overexpression could increase the virus titre in HBEMC at 24 h post-infection suggesting that GRP78 was associated with the replication capacity of EV71 in HBMEC. Conclusion: These findings provided evidence that GRP78 plays an important role during the progression of EV71 infection as a mediator in HBMEC.  相似文献   
15.
The pituitary tumor-transforming gene 1 (PTTG1), also known as Securin, is considered an oncogene. This study aimed to investigate the role of PTTG1 in clear cell renal cell carcinoma (ccRCC) using in silico bioinformatics approaches. A pan-cancer analysis using The Cancer Genome Atlas (TCGA) data indicated that among all cancer types copy number amplification of PTTG1 gene was most frequently found in ccRCC. However, amplification of PTTG1 gene copy number did not correlate with the increase of mRNA level in ccRCC, and did not predict the patients' overall survival. Instead, ccRCC was correlated with overexpression of PTTG1 mRNA, and its expression level was stage-dependent increased in cancer patients. An outlier analysis using the Oncomine database suggested that PTTG1 mRNA expression served as a good biomarker for ccRCC. Pathway analysis for upregulated genes enriched in PTTG1-high expressing ccRCC patients found that PTTG1 overexpression was associated with mitotic defects. Mining drug sensitivity data using the Cancer Therapeutics Response Portal (CTRP) discovered that PTTG1-high expressing ccRCC cell lines were susceptible to a Rac1 (Ras-related C3 botulinum toxin substrate 1) inhibitor NSC23766. Therefore, this study provides an in silico insight into the role of PTTG1 in ccRCC, and repurposes the Rac1 inhibitor NSC23766 for treating PTTG1-high expressing ccRCC.  相似文献   
16.
A pathological feature in atherosclerosis is the dysfunction and death of vascular endothelial cells (EC). Oxidized low‐density lipoprotein (LDL), known to accumulate in the atherosclerotic arterial walls, impairs endothelium‐dependent relaxation and causes EC apoptosis. A major bioactive ingredient of the oxidized LDL is lysophosphatidylcholine (LPC), which at higher concentrations causes apoptosis and necrosis in various EC. There is hitherto no report on LPC‐induced cytotoxicity in brain EC. In this work, we found that LPC caused cytosolic Ca2+ overload, mitochondrial membrane potential decrease, p38 activation, caspase 3 activation and eventually apoptotic death in mouse cerebral bEND.3 EC. In contrast to reported reactive oxygen species (ROS) generation by LPC in other EC, LPC did not trigger ROS formation in bEND.3 cells. Pharmacological inhibition of p38 alleviated LPC‐inflicted cell death. We examined whether heparin could be cytoprotective: although it could not suppress LPC‐triggered Ca2+ signal, p38 activation and mitochondrial membrane potential drop, it did suppress LPC‐induced caspase 3 activation and alleviate LPC‐inflicted cytotoxicity. Our data suggest LPC apoptotic death mechanisms in bEND.3 might involve mitochondrial membrane potential decrease and p38 activation. Heparin is protective against LPC cytotoxicity and might intervene steps between mitochondrial membrane potential drop/p38 activation and caspase 3 activation.  相似文献   
17.
目的 分析哮喘儿童血清中血管内皮功能相关标记物的变化情况及其与疾病预后的关系,为儿童哮喘预后的评估提供依据。方法 收集2016年10月-2017年12月在南通大学附属常州儿童医院就诊的89例5~14岁哮喘患儿在哮喘发作期的血清样本和92例健康儿童的血清样本,运用ELISA和其他商用测试盒检测其中内皮功能相关标志物血管内皮生长因子(VEGF)、精氨酸酶I(Arg I)、骨膜蛋白(POSTN)、脂联素(APN)和瘦素的浓度以及诱导型一氧化氮合酶(iNOS)活性,并用高效液相串联质谱(HPLC-MS/MS)检测L-精氨酸、甲基化精氨酸ADMA和SDMA的浓度。此后对哮喘组患儿进行为期1年的随访,记录在此期间出现喘息发作的次数。运用正交偏最小二乘法-判别分析(OPLS-DA)分析数据,筛选对哮喘疾病预后有关键影响的血管内皮功能相关标记物。结果 哮喘组儿童血清中Arg I、POSTN、VEGF和瘦素的含量显著增加,iNOS活性显著增高,L-精氨酸浓度显著下降(P<0.05)。OPLS-DA模型显示,基于内皮功能多标记物哮喘组可以和对照组显著区分,且Arg I、iNOS活性以及VEGF水平的变量重要性因子(VIP)值分别为2.11、1.23、1.09,是区分哮喘组和对照组的关键内皮标记物。随访后1年,随访成功70例,其中反复喘息组(n=27)与非反复喘息组(n=43)相比,血清ADMA和Arg I的含量显著增加,POSTN和APN含量显著减少(P<0.05)。OPLS-DA模型的S-plot图和VIP值排序都表明区分两组的关键内皮标记物是APN、POSTN和Arg I。结论 哮喘儿童血清中多种内皮功能相关的生物标记物稳态失衡,其中APN、POSTN和Arg I对儿童哮喘的疾病预后有较高的预测价值。  相似文献   
18.
Purpose: To compare the responses of types 1 (sub-pigment epithelial) and 2 (subretinal) neovascularization in neovascular age-related macular degeneration (AMD) to anti-vascular endothelial growth factor (VEGF) treatment.

Methods: Fifty-five treatment-naïve neovascular AMD eyes (53 patients) were retrospectively included for analysis. All patients were treated with three loading injections of anti-VEGF agent, followed by further injections as required. The lesion size and vascular density of type 1 and 2 lesions before and after treatment for 12 months were analyzed using optical coherence tomography angiography (OCTA).

Results: The mean lesion size of the type 1 neovascularization group (42 eyes) showed no significant change from 2.12 ± 1.01 mm2 at baseline to 2.08 ± 0.91 mm2 at 12 months (P = .682). However, the mean lesion size of type 2 neovascularization significantly decreased from 1.23 ± 0.93 mm2 at baseline to 0.79 ± 0.61 mm2 at 12 months (P = .022). The proportion of eyes with lesion sizes that decreased by more than 40% from baseline was also significantly higher for the type 2 compared to the type 1 neovascularization group (46.2% versus 11.9%, P = .007). Vascular density showed no significant changes for both groups after treatment and showed no association with the change in lesion size. There was no significant difference between the groups in terms of visual acuity improvement.

Conclusion: OCTA analysis revealed different responses to anti-VEGF treatment depending on the location of neovascularization in neovascular AMD. Type 2 neovascularization was significantly regressed compared to type 1 neovascularization after anti-VEGF treatment. However, the changes in vascular density and visual outcome showed no significant differences between groups after 12 months of treatment.  相似文献   

19.
《Vaccine》2019,37(31):4382-4391
Cancer-associated fibroblasts (CAFs), major components of the tumor microenvironment (TME), promote tumor growth and metastasis and inhibit the anti-tumor immune response. We previously constructed a DNA vaccine expressing human FAPα, which is highly expressed by CAFs, to target these cells in the TME, and observed limited anti-tumor effects in the 4T1 breast cancer model. When the treatment time was delayed until tumor nodes formed, the anti-tumor effect of the vaccine completely disappeared. In this study, to improve the safety and efficacy, we constructed a new FAPα-targeted vaccine containing only the extracellular domain of human FAPα with a tissue plasminogen activator signal sequence for enhanced antigen secretion and immunogenicity. The number of CAFs was more effectively reduced by CD8+ T cells induced by the new vaccine. This resulted in decreases in CCL2 and CXCL12 expression, leading to a significant decrease in the ratio of myeloid-derived suppressor cells in the TME. Moreover, when mice were treated after the establishment of tumors, the vaccine could still delay tumor growth. To facilitate the future application of the vaccine in clinical trials, we further optimized the gene codons and reduced the homology between the vaccine and the original sequence, which may be convenient for evaluating the vaccine distribution in the human body. These results indicated that the new FAPα-targeted vaccine expressing an optimized secreted human FAPα induced enhanced anti-tumor activity by reducing the number of FAPα+ CAFs and enhancing the recruitment of effector T cells in the 4T1 tumor model mice.  相似文献   
20.
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   
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