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   43928篇
  免费   4602篇
  国内免费   2987篇
耳鼻咽喉   499篇
儿科学   482篇
妇产科学   372篇
基础医学   4061篇
口腔科学   668篇
临床医学   5325篇
内科学   5166篇
皮肤病学   379篇
神经病学   2070篇
特种医学   1733篇
外国民族医学   16篇
外科学   4937篇
综合类   9897篇
现状与发展   10篇
一般理论   1篇
预防医学   3765篇
眼科学   948篇
药学   4781篇
  56篇
中国医学   2936篇
肿瘤学   3415篇
  2025年   10篇
  2024年   619篇
  2023年   885篇
  2022年   1967篇
  2021年   2239篇
  2020年   1764篇
  2019年   1333篇
  2018年   1402篇
  2017年   1448篇
  2016年   1327篇
  2015年   2125篇
  2014年   2604篇
  2013年   2621篇
  2012年   3778篇
  2011年   4198篇
  2010年   3093篇
  2009年   2559篇
  2008年   2895篇
  2007年   2813篇
  2006年   2458篇
  2005年   2201篇
  2004年   1425篇
  2003年   1136篇
  2002年   888篇
  2001年   707篇
  2000年   602篇
  1999年   491篇
  1998年   309篇
  1997年   277篇
  1996年   213篇
  1995年   202篇
  1994年   129篇
  1993年   115篇
  1992年   116篇
  1991年   114篇
  1990年   89篇
  1989年   55篇
  1988年   65篇
  1987年   57篇
  1986年   50篇
  1985年   39篇
  1984年   23篇
  1983年   8篇
  1982年   13篇
  1981年   10篇
  1979年   12篇
  1978年   5篇
  1974年   8篇
  1972年   5篇
  1969年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Cross-frequency phase-amplitude coupling (PAC) in neuronal oscillations network plays an important functional role in large scale neuronal communication and neuronal encoding. In the present study, a novel approach named permutation mutual information (PMI) was applied in measuring PAC. It is derived from the permutation entropy based on the mutual information theory, by which the mutual information of permutations of two time series can be evaluated. In order to verify the ability of PMI, a numerical test was performed by using both simulation data and experimental data. The performances of PMI were compared with that of two well-known methods, which were the mean vector length (MVL) and the modulation index (MI). It was found that the performance of PMI was similar to that of MI when measuring PAC intensity, but the coupling sensitivity of PMI was the highest among all these three approaches. Moreover, there was the lowest sensitivity in the MVL measurement, suggesting that MVL was a more conservative approach in detecting the existence of PAC. In addition, an ROC analysis showed that PMI performed better in measuring PAC compared to that of others. Furthermore, the experimental data, obtained from rats’ hippocampal CA3 regions, were analyzed by using the three approaches. The result was essentially in line with that of the simulation performances. In a word, the results suggest that PMI is a better choice for assessing PAC under the certain conditions.  相似文献   
92.
Even in the modern era of targeted therapies, allogeneic hematopoietic stem cell transplantation (allo-HCT) can offer a chance of extended survival in B cell non-Hodgkin lymphoma (B-NHL) patients who relapse after or are deemed ineligible for autologous transplantation. A better understanding of the factors influencing the graft-versus-lymphoma (GVL) response would be useful in identifying B-NHL patients who may benefit from allo-HCT. Based on prior single-center reports, we hypothesized that certain HLA alleles, or haplotypes, may be associated with superior GVL compared with others after allo-HCT. To test this possibility we retrospectively evaluated whether the presence of HLA-A2, HLA-C1C1, HLA-DRB1*01:01, or HLA-DRB1*13 alleles or the presence of HLA-A1+, HLA-A2-, and HLA-B44- haplotypes is associated with outcomes in a cohort of 1314 HLA-8/8 matched sibling or unrelated donor HCT for relapsed/refractory B-NHL. We observed no significant association between any HLA allele or haplotype and overall survival or any of the secondary endpoints. In conclusion, this study represents the largest reported series of allo-HCT outcomes of B-NHL patients based on HLA type. Identification of other variables will be required to delineate the immunologic impact of donor–host interactions on outcomes of allo-HCT for B-NHL.  相似文献   
93.
BACKGROUND: Human umbilical cord mesenchymal stem cells (hUC-MSCs) have low immunogenicity and it is unclear whether insulin producing cells (IPCs) that differentiate from hUC-MSCs have low immunogenicity. OBJECTIVE: To investigate the immunogenicity of IPCs differentiating from hUC-MSCs in vitro and after IPCs transplantation into the host. METHODS: (1) The hUC-MSCs were induced to differentiate into IPCs according to the modified scheme. Flow cytometry assay was used to detect the immunophenotype and apoptotic rate of IPCs in a cytotoxicity test. (2) Cell counting kit-8 was used to detect the proliferative capacity of human peripheral blood mononuclear cells in the one-way mixed lymphocyte assay. (3) The IPCs were then transplanted into the abdominal cavity and left renal capsule of mice, and then the infiltration of immune cells was detected by flow cytometry and immunohistochemistry. RESULTS AND CONCLUSION: The IPCs highly expressed HLA-ABC and lowly expressed HLA-DR, CD40 and CD80. The apoptosis rate of IPCs increased with the increase of pre-sensitized splenocytes in the cytotoxicity test. In the one-way mixxd lymphocyte assay, IPCs inhibited the proliferation of human peripheral blood mononuclear cells when the target ratio was 10:1 and 50:1. After IPCs transplantation, the number of lymphocytts was increased in the transplanttd si. In summary, our results show that IPCs that differentiatt from hUC-MSCs maintain low immunogenicity in vitro, but have some immunogenicity after transplantation into the host due to microenvironment changes. © 2018, Journal of Clinical Rehabilitative Tissue Engineering Research. All rights reserved.  相似文献   
94.
95.
Delayed neurological deterioration in the absence of direct spinal cord insult following surgical decompression is a severe postoperative complication in patients with chronic severe spinal cord compression (SCC). The spinal cord ischemia-reperfusion injury (IRI) has been verified as a potential etiology of the complication. However, the exact pathophysiologic mechanisms of the decompression-related IRI remain to be defined. In this study, we developed a practical rat model of chronic severe SCC. To explore the underlying role of inflammation in decompression-related IRI, immunoreactivity of pro-inflammatory cytokines including tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) before and after decompression were measured. In addition, expression level of TNF-α and IL-1β was examined with Western blot. Immunohistochemical staining showed negative result in gray matters in the sham group and sham-decompression group. In the severe compression group, strong positive staining of TNF-α and IL-1β were found, suggesting a dramatic infiltration of inflammatory cells in gray matters. Furthermore, the severe compression group showed a significant increase in expression level of TNF-α and IL-1β as compared with the sham group (p < 0.05). In the severe compression-decompression group, both immunostaining and Western blot showed significant increase of TNF-α and IL-1β levels in the spinal cord compared with the severe compression group (p < 0.05). The results demonstrated that surgical decompression plays a stimulative role in inflammation through increasing the expression of inflammatory cytokines in the rat model of chronic severe SCC injury. Inflammation may be one of the important pathological mechanisms of decompression-related IRI of chronic ischemia.  相似文献   
96.
目的 观察双氢青蒿素(DHA)对人骨肉瘤细胞活性、转移能力以及细胞中尿激酶型纤溶酶原激活物(uPA)和色素上皮衍生因子(PEDF)表达的影响.方法 将不同浓度的DHA(5、10、20、40、80 μmol/L)作用于体外培养的正常人成骨细胞和人骨肉瘤细胞TE85 12、24、48 h后,噻唑蓝(MTT)法测定DHA对细胞活性的影响,反转录-聚合酶链反应(RT-PCR)法检测细胞中uPA和PEDF mRNA水平的表达,Westen blot法检测uPA和PEDF蛋白水平的表达.结果 DHA对人成骨细胞活性无明显影响(P>0.05).DHA能够明显抑制人骨肉瘤细胞TE85的活性(P<0.05).不同作用时间下DHA对人骨肉瘤细胞TE85的半数抑制浓度(IC50)分别为(12 h)=(41.66±0.53) μmol/L、IC50(24 h)=(32.28 ±0.27)μmol/L和IC50 (48 h)=(22.53±1.26) μmol/L.DHA能够明显减少人骨肉瘤细胞的迁移和细胞中uPA的表达水平,同时细胞中PEDF表达升高(P<0.05).结论 DHA对正常人体骨组织无害,能够有效抑制骨肉瘤细胞生长和转移.  相似文献   
97.
Objective To analyze the risk factors of mortality among patients treated by maintenance hemodialysis (MHD), and identify whether handgrip strength (HGS) or other nutrient markers could predict the mortality independently. Methods One hundred and eight patients receiving regular MHD in Peking Union Medical College Hospital from July to September, 2008 were involved. Baseline data including clinical data, nutrient data such as subjective global assessment, anthropometrics and biochemical measurement were collected. After being followed for 72 months, the patients' mortality and morbidity of cardiovascular event were recorded. Cox regression model was used to estimate the risk factors of mortality. Results The average age of 108 MHD patients was (57.6±13.0) years. During the 6-years following up, 35 patients died (32.4%), of whom 62.9% died of cardiovascular events. Among variables, patients’ age, residual urine volume, serum creatinine level, prealbumin level and mean leg circumference were risk factors for all-cause mortality. The patient with lower HGS bore higher risk for all-cause mortality (HR=2.842, 95%CI 1.390-5.811) and cardiovascular death (HR=2.826, 95%CI 1.150-6.947). After adjusting gender, age, history of cardiovascular disease and diabetes, body mass index (BMI), dialysis vintage, Kt/V, nPCR and prealbumin, lower handgrip strength was still an independent risk factor of all-cause mortality (HR=2.505, 95%CI 1.112-5.642). In prediction for all-cause mortality by HGS, the area under the receiver operating characteristic curve(ROC) were 0.705 and 0.682 among men and women respectively. Conclusion Lower handgrip strength can predict mortality of maintenance hemodialysis patients independently.  相似文献   
98.
Xiao  Ruhui  Chen  Jiao  Zeng  Chen  Feng  Xu  Li  Tao  Das  Sushant-kumar  Li  Bing  Zhang  Chuan  Yang  Hanfeng 《Neurological sciences》2022,43(3):1685-1693
Neurological Sciences - As the incidence of peripheral neurological diseases increases, the precise display of nerves becomes important in imaging examinations. Among them, the pain caused by...  相似文献   
99.
100.
Wu  Jie  Wu  Xiao  Yang  You Qing  Ding  Han  Yang  Le  Bao  You Yuan  Zhou  Lin  Yang  Chen Xing  Hong  Tao 《Neurosurgical review》2022,45(1):139-150

It is controversial whether there is a different risk of recurrence between two histological subtypes in craniopharyngioma (CP) patients. Some reported that adamantinomatous craniopharyngioma (ACP) had a higher risk of recurrence than papillary craniopharyngioma (PCP), but others reported that there is no significant difference between them. So, we conducted this systematic review and meta-analysis to determine the association between the histological subtype of CP and the rate of recurrence. A comprehensive literature search was undertaken in PubMed, EMBASE, and Web of Science for all English articles published up to November 2020. Recurrence data stratified by ACP and PCP were extracted from studies meeting inclusion criteria. A pooled analysis of the association between the histological subtype of craniopharyngioma and rates of recurrence was performed. Thirteen articles containing 974 patients were included. When stratified by two pathological subtypes, the total recurrence rate of ACP was 26.0% and PCP was 14.1%, which showed ACP associated with a higher risk of tumor recurrence than PCP (odds ratio [OR]?=?2.12, 95% confidence interval [CI]?=?1.36, 3.30, P?=?0.00). This is the first meta-analysis focusing on histological subtypes of CP. PCP associates with a lower risk of recurrence than ACP, indicating that ACP could act as one of recurrence risk factors for CP patients. Nevertheless, large sample size and well-designed multicenter studies in which the other clinical variables are controlled to determine the histological subtype of CP as an independent recurrence risk factor are needed.

  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