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   27577篇
  免费   2335篇
  国内免费   987篇
耳鼻咽喉   129篇
儿科学   532篇
妇产科学   274篇
基础医学   8626篇
口腔科学   410篇
临床医学   2375篇
内科学   4845篇
皮肤病学   890篇
神经病学   838篇
特种医学   276篇
外国民族医学   12篇
外科学   1676篇
综合类   3807篇
现状与发展   5篇
预防医学   882篇
眼科学   207篇
药学   1491篇
  1篇
中国医学   460篇
肿瘤学   3163篇
  2024年   40篇
  2023年   260篇
  2022年   477篇
  2021年   681篇
  2020年   612篇
  2019年   686篇
  2018年   687篇
  2017年   710篇
  2016年   777篇
  2015年   1025篇
  2014年   1404篇
  2013年   1725篇
  2012年   1457篇
  2011年   2024篇
  2010年   1719篇
  2009年   1880篇
  2008年   1691篇
  2007年   1668篇
  2006年   1573篇
  2005年   1420篇
  2004年   1271篇
  2003年   1142篇
  2002年   955篇
  2001年   774篇
  2000年   667篇
  1999年   580篇
  1998年   553篇
  1997年   419篇
  1996年   425篇
  1995年   431篇
  1994年   339篇
  1993年   256篇
  1992年   141篇
  1991年   131篇
  1990年   65篇
  1989年   39篇
  1988年   23篇
  1987年   10篇
  1986年   7篇
  1985年   10篇
  1984年   26篇
  1983年   13篇
  1982年   11篇
  1981年   23篇
  1980年   14篇
  1979年   9篇
  1978年   10篇
  1976年   11篇
  1974年   6篇
  1973年   8篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
目的 观察结核杆菌低分子多肽抗原(Mtb-Ag)再刺激Mtb-Ag活化的T细胞(Mtb-AT细胞)诱导γδT细胞CD69分子的再表达的情况.方法 分离获取健康人外周血单个核细胞(PBMC),用Mtb-Ag刺激PBMC,采用直接免疫荧光染色法通过CD3PE/CD69FITC、γδPE/CD69FITC细胞双染检测γδT细胞0、6、12、24、48和72 h CD69分子的表达情况.PBMC经Mtb-Ag刺激活化扩增培养至10 d后再次加入Mtb-Ag,经培养0、6、12、24、48和72 h后收集细胞,再次检测CD69分子的表达情况.结果 培养0、6、12、24、48和72 h后,Mtb-Ag初次刺激γδT细胞后CD69分子的表达分别为0.91%、15.1%、35.2%、75.2%、59.4%和50%.再次刺激培养0、6、12、24、48和72 h后,γδT细胞CD69分子的表达分别为1.7%、72.3%、73.5%、50.3%、45.6%、41.7%.结论Mtb-Ag初次刺激γδT细胞表达CD69分子约在24 h达高峰,随后快速下降;Mtb-Ag再次刺激Mtb-AT细胞诱导γδT细胞CD69分子的再表达,6h时CD69分子达高峰,可维持到12 h.这为寻求γδT细胞迅速活化、CD69分子的迅速表达奠定了方法学基础.  相似文献   
992.
CD10分子最初作为普通急性淋巴细胞白血病抗原(CALLA)被发现,是一个相对分子质量为90 000-110 000Ⅱ型单链穿膜糖蛋白.CD10分子广泛分布在各种组织,具有中性肽链内切酶(NEP)的功能,并且表达在不同的组织,其功能不尽相同.目前广泛应用于用血液系统肿瘤以及部分实体肿瘤的诊断和预后判断,还用于造血细胞分化发育研究和部分组织干细胞的研究.  相似文献   
993.
The pathogenesis and therapy of Shigatoxin 2 (Stx2)‐mediated kidney failure remain controversial. Our aim was to test whether, during an infection with Stx2‐producing E. coli (STEC), Stx2 exerts direct effects on renal tubular epithelium and thereby possibly contributes to acute renal failure. Mice represent a suitable model because they, like humans, express the Stx2‐receptor Gb3 in the tubular epithelium but, in contrast to humans, not in glomerular endothelia, and are thus free of glomerular thrombotic microangiopathy (TMA). In wild‐type mice, Stx2 caused acute tubular dysfunction with consequent electrolyte disturbance, which was most likely the cause of death. Tubule‐specific depletion of Gb3 protected the mice from acute renal failure. In vitro, Stx2 induced secretion of proinflammatory cytokines and apoptosis in human tubular epithelial cells, thus implicating a direct effect of Stx2 on the tubular epithelium. To correlate these results to human disease, kidney biopsies and outcome were analysed in patients with Stx2‐associated kidney failure (n = 11, aged 22–44 years). The majority of kidney biopsies showed different stages of an ongoing TMA; however, no glomerular complement activation could be demonstrated. All biopsies, including those without TMA, showed severe acute tubular damage. Due to these findings, patients were treated with supportive therapy without complement‐inhibiting antibodies (eculizumab) or immunoadsorption. Despite the severity of the initial disease [creatinine 6.34 (1.31–17.60) mg/dl, lactate dehydrogenase 1944 (753–2792) U/l, platelets 33 (19–124)/nl and haemoglobin 6.2 (5.2–7.8) g/dl; median (range)], all patients were discharged after 33 (range 19–43) days with no neurological symptoms and no dialysis requirement [creatinine 1.39 (range 0.84–2.86) mg/dl]. The creatinine decreased further to 0.90 (range 0.66–1.27) mg/dl after 24 months. Based on these data, one may surmise that acute tubular damage represents a separate pathophysiological mechanism, importantly contributing to Stx2‐mediated acute kidney failure. Specifically in young adults, an excellent outcome can be achieved by supportive therapy only. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.  相似文献   
994.
Background: Precursor B acute lymphoblastic leukemia (B-ALL) is the most common cancer in children and overall, has an excellent prognosis. However, the Philadelphia chromosome translocation (Ph+), t(9;22)(q34;q11), is present in a small subset of patients and confers poor outcomes. CD25 (IL-2 receptor alpha chain) expression has been associated with Ph+ B-ALL in adults, but no similar study has been performed in pediatric B-ALL. Methods: A retrospective analysis of 221 consecutive pediatric patients with a diagnosis of B-ALL (blood and/or bone marrow) from 2009 to 2012 was performed to determine an association between Ph+ B-ALL and CD25 expression. A threshold of 25% was used to define positive cases for CD25 expression by flow cytometry. Results: There were 221 patients with a diagnosis of B-ALL ranging from 2 to 22 years (median, 6 years). Eight (3.6%) B-ALL patients were positive for the Philadelphia chromosome translocation (Ph+ B-ALL) and 213 were negative (Ph-negative B-ALL). CD25 expression was observed in 6 of 8 (75%) Ph+ B-ALL patients and 6 of 213 (2.8%) Ph-negative B-ALL patients. CD25 expression was significantly higher in Ph+ B-ALL compared to Ph-negative B-ALL, with median CD25 expression of 64% (range 0-93%) and 0.1% (range 0-91%), respectively (P ≤ 0.0002). Therefore, CD25 expression as a predictor of Ph+ B-ALL had 75% sensitivity, 97% specificity, 50% positive predictive value and 99% negative predictive value. Conclusions: CD25 expression is a specific and relatively sensitive marker for the identification of Ph+ B-ALL in the pediatric population.  相似文献   
995.
Although the influence of transplanted bone marrow (BM) CD34+ cells on neutrophil engraftment (NE) and transplantation outcomes has been discussed controversially, thresholds between 2 and 4 × 106/kg CD34+ cells are commonly accepted. This has substantial consequences for a donor in terms of BM volume to be collected, which frequently covers up to 15 to 20 mL/kg. As the BM CD34+ compartment contains varying fractions of CD34+/CD19+ B lymphoid progenitors, we tested the hypothesis that the infused CD34+/CD45dim/CD19-/CD10- myeloid stem cells might reliably predict NE in 94 children who received BM from 37 HLA-identical sibling donors (MSD) and 57 matched unrelated donors after myeloablative conditioning. The grafts contained a median of 3.6 × 106/kg total CD34+ cells, which consisted of a median of 73% myeloid CD34+ cells and 27% B lymphoid progenitors. Grafts from donors <15 years old yielded significantly lower myeloid fractions compared with grafts from older donors (P < .001). All patients achieved sustained NE after median 20 (range, 11 to 40) days. By multivariate analysis, neither the number of total CD34+ cells (P = .605) nor of myeloid CD34+ cells (P = .981) correlated with NE, whereas transplantation from MSD (hazard ratio [HR] 3.51; P = .019) and the administration of granulocyte colony–stimulating factor (HR 2.24; P = .002) remained independent factors associated with earlier NE. Furthermore, neither total nor myeloid CD34+ cell quantities were associated with incidences of severe infections before NE (P = .271 and P = .132) or transplantation-related mortality (TRM) at day +100 (P = .294 and P = .490). Taking into account that the number of transplanted total CD34+ or myeloid CD34+ cells does not seem to have a relevant impact on time to NE, sepsis rates, or TRM, the need of certain threshold cell numbers should be revisited, at least for pediatric MSD.  相似文献   
996.
In the last decade, peripheral blood was the main source of hematopoietic stem cells (HSC) for autologous and allogeneic transplantation. The exact mechanisms of HSC mobilization are still not clear and the efficacy of the procedure is hardly predictable. Ligand-receptor interactions of adhesion molecules, such as SDF1/CXCR4, VLA4/VCAM-1, or CD44/osteopontin, play an important role in homing of HSC in the hematopoietic niche. There is some evidence that disruption of the ligand-receptor complex leads to the egress of HSCs to the peripheral blood. The aim of the present study was the evaluation of constitutive polymorphism of genes encoding cytokines and receptors present in the HSC niche and their impact on the efficacy of mobilization of HSCs in patients with hematological malignancies. We enrolled 110 patients (60 females and 50 males) in the study. The median age of the patients was 55 (range, 22 to 69) years. The group consisted of patients with multiple myeloma (n = 74), non-Hodgkin lymphoma (n = 19), Hodgkin lymphoma (n = 15), or acute myeloid leukemia (n = 2). The mobilization procedures comprised chemotherapy and subsequent granulocyte-colony stimulating factor (G-CSF) at a dose of 10 μg/kg daily. The poor mobilizers group was defined according to Italian National Bone Marrow Transplant Registry criteria: patients with peak CD34+ in the peripheral blood < 20/μL or total yield < 2 × 106 CD34+ cells/kg body weight in maximum 3 aphereses. Genotyping was performed using standard PCR-based assays. The group of patients (N = 108) who achieved minimal threshold for collections (CD34+ at least 10/μL) proceeded to apheresis. The median total yield of CD34+ in this group was 5.6 × 106 cells/kg body weight, whereas the median number of cells collected during the first apheresis was 3.3 × 106 cells/kg body weight. Median number of days of G-CSF treatment before first apheresis was 10. Fifteen patients fulfilled the criteria for poor mobilizer. The group of poor mobilizers had higher frequency of TT genotype in rs13347 (CD44) gene (CC+ CT versus TT P = .047). Patients homozygous for T allele had a lower total yield of CD34+ cells/kg body weight than the group with allele C (median, 3.7 × 106/kg versus 5.8 × 106/kg; P = .019) and a lower number of CD34+ cells gathered during first apheresis (.95 × 106/kg versus 3.3 × 106/kg, P = .04). Multivariate logistic regression analysis revealed that the CD44 TT genotype was the only factor associated with 5-fold higher risk of poor mobilization (P = .037). Polymorphic variants of CXCR4 and VCAM-1 did not significantly influence the efficacy of HSCs mobilization in our group of patients. In conclusion, our results indicate that among investigated single nucleotide polymorphisms (SNPs), only CD44 rs13347 has an impact on the efficacy of HSCs mobilization in patients with hematologic malignancies. CD44 SNPs analysis may be helpful for predicting the poor mobilizers population who may benefit from newer modalities using adhesion molecules inhibitors.  相似文献   
997.
Poor graft function (PGF) is characterized by pancytopenia and a hypoplastic marrow, with complete donor chimerism, usually without severe graft-versus-host disease (GVHD). We report 41 patients with PGF, treated with granulocyte colony-stimulating factor–mobilized CD34 selected cells, at a median interval from transplant of 140 days, without conditioning and without GVHD prophylaxis. Donors were HLA matched siblings (n = 12), unrelated donors (n = 18), or mismatched family members (n = 11). The median number of infused CD34+ cells was 3.4 × 106/kg. The rate of trilineage recovery was 75%: 83% for HLA matched siblings and 72% for unrelated and mismatched family members (P = .3). The cumulative incidence of acute grade II GVHD was 15%, and no patient developed de novo chronic GVHD. The actuarial 3-year survival is 63%: 76% and 25% for patients with or without trilineage recovery. These data confirm the role of CD34+ selected cells from the same donor in the treatment of PGF and warrant the request for a second donation also when the donor is unrelated.  相似文献   
998.
Accumulating evidence has indicated the importance of cancer stem cells in carcinogenesis. The goal of the present study was to determine the effect of low-dose cisplatin on enriched liver cancer stem cells (LCSCs). Human hepatoblastoma HepG2 cells were treated with concentrations of cisplatin ranging from 1 to 5 μg/mL. Cell survival and proliferation were evaluated using a tetrazolium dye (MTT) assay. LCSCs were identified using specific markers, namely aldehyde dehydrogenase-1 (ALDH1) and CD133. The percentage of ALDH1+ or CD133+ cells was examined by flow cytometric analysis. The expression of ALDH1 and/or CD133 in HepG2 cells was determined by immunocytochemical analysis. Low-dose cisplatin treatment significantly decreased cell survival in HepG2 cells after 24 or 72 h. However, the percentage of LCSCs in the surviving cells was greatly increased. The percentage of ALDH1+ or CD133+ cells was increased in a time- and dose-dependent manner after treatment with 1-4 μg/mL cisplatin, whereas 5 μg/mL cisplatin exposure slightly reduced the number of positive cells. These findings indicate that low-dose cisplatin treatment may efficiently enrich the LCSC population in HepG2 cells.  相似文献   
999.
Background: The prognostic value of CD117 expression in cancers has been evaluated for several years while the results remain controversial. We thus performed a systematic review and meta-analysis of studies assessing the impact of CD117 expression on overall survival (OS) and disease-free survival (DFS) to clarify this issue. Methods: We searched Pubmed, Embase and Web of Science to identify studies on the prognostic impact of CD117 expression in cancers. A total of 4,458 patients from 39 eligible studies were included in the analysis. Pooled risk ratios (RRs) with 95% confidence interval (95% CI) were calculated to estimate the effect using random-effects model. Results: The analysis indicated that CD117 had significant association with poor OS of osteosarcoma (OR=1.36, 95% CI=1.03-1.79, I2=0%, fixed model) and renal carcinoma (OR=4.86, 95% CI=2.72-8.67, I2=0%, fixed model).However, no significant association between CD117 and DFS was found in overall studies. Conclusions: CD117 expression might be a predictive factor of poor prognosis in some surgically treated cancers, particularly in renal carcinoma.  相似文献   
1000.
Epithelioid gastrointestinal stromal tumors (GISTs) may cause significant diagnostic confusion on fine-needle aspiration (FNA) with carcinomas, neuroendocrine tumors, and melanoma, particularly when metastatic. This study characterizes the cytologic features of nine cases of epithelioid GISTs that were obtained by computerized tomographic guidance in five, by endoscopic ultrasound in three, and from an excised liver tumor in one. Six cases presented as liver masses, one as a perisplenic mass, one as an abdominal mass, and one as a gastric mass. The aspirates revealed mainly single or small clusters of epithelioid cells with a moderate amount of granular to clear cytoplasm, small uniform nuclei with mild to marked nuclear envelope irregularities. Binucleation and intranuclear inclusions were frequent findings. Collagenous stroma was seen in most cases. In three cases, a neuroendocrine tumor was the initial diagnosis. Immunocytochemical staining for c-kit (CD117) was performed on cellblocks in six cases and was positive in five cases. On the subsequent surgical specimen, CD117 was positive in the c-kit-negative cytology case. The diagnosis of GIST should be considered in aspirates of the gastrointestinal tract, liver, mesentery, or abdominal wall mass lesions when epithelioid cells are the predominant cell type. Ancillary studies such as immunohistochemical stains are usually helpful in making a definitive diagnosis.  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