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   5656篇
  免费   482篇
  国内免费   238篇
耳鼻咽喉   38篇
儿科学   78篇
妇产科学   66篇
基础医学   909篇
口腔科学   114篇
临床医学   698篇
内科学   656篇
皮肤病学   101篇
神经病学   354篇
特种医学   364篇
外国民族医学   2篇
外科学   347篇
综合类   1008篇
预防医学   229篇
眼科学   80篇
药学   593篇
  1篇
中国医学   263篇
肿瘤学   475篇
  2024年   11篇
  2023年   78篇
  2022年   165篇
  2021年   267篇
  2020年   218篇
  2019年   190篇
  2018年   139篇
  2017年   170篇
  2016年   193篇
  2015年   191篇
  2014年   318篇
  2013年   316篇
  2012年   319篇
  2011年   337篇
  2010年   306篇
  2009年   278篇
  2008年   253篇
  2007年   262篇
  2006年   277篇
  2005年   225篇
  2004年   229篇
  2003年   221篇
  2002年   179篇
  2001年   161篇
  2000年   126篇
  1999年   117篇
  1998年   85篇
  1997年   86篇
  1996年   73篇
  1995年   71篇
  1994年   55篇
  1993年   44篇
  1992年   42篇
  1991年   40篇
  1990年   39篇
  1989年   28篇
  1988年   33篇
  1987年   39篇
  1986年   31篇
  1985年   36篇
  1984年   22篇
  1983年   18篇
  1982年   19篇
  1981年   16篇
  1980年   13篇
  1979年   7篇
  1978年   8篇
  1977年   4篇
  1976年   4篇
  1974年   5篇
排序方式: 共有6376条查询结果,搜索用时 484 毫秒
141.
[目的]分析影像学骶髂关节炎的误诊病例和典型病例,提高对影像学骶髂关节炎包括强直性脊柱炎(AS)、致密性骨炎(OC)及跨专科疾病的认识.[方法](1)筛选出诊断明确,资料齐全的腰背痛或伴骶髂关节炎的误诊病例104例进行分析;(2)收集确诊的OC病例11例和AS病例50例,从临床表现、体格检查、影像学、实验室检查方面进行对比分析.[结果](1)104例误诊病例包括感染性疾病(29.81%)、骨关节疾病(26.92%)、内分泌代谢疾病(22.12%)、血液系统疾病(10.58%)和肿瘤(8.65%);(2)OC和AS的病例特点分析:OC组均为女性,均有下腰痛,大部分活动后加重,部分患者可有与AS相似的夜间痛和晨僵,Schober试验均阴性,CRP和ESR多正常,HLA-B27均阴性,骶髂关节X线和MRI显示OC的改变.AS组41例男性,9例女性,均有炎性腰痛表现,部分病人Schober试验阳性,CRP和ESR多升高,HLA-B27多阳性,骶髂关节X线和MRI显示AS的改变.[结论]影像学显示骶髂关节炎和伴有慢性腰背痛的疾病鉴别诊断需结合临床年龄、病史、症状、体征、实验室检查以及影像学检查等综合分析,注意跨专科疾病的诊断和鉴别,避免误诊.  相似文献   
142.
143.
Malignant gastric lymphoma (MGL) accounts for a small proportion (upto 5%) of gastric malignancies. However, unlike for advanced gastric cancer (AGC) that requires surgical treatment, the standard treatments for MGL are chemotherapy and radiotherapy. Hence, the initial impression of the endoscopist is critical for the differential diagnosis and for planning future treatment. The purpose of this study was to assess the endoscopic diagnostic accuracy and the possibility of distinguishing between AGC and MGL depending on the endoscopist''s experience.A total of 48 patients who had MGL, and 48 age and sex-matched patients who had AGC were assessed by endoscopic review at a tertiary referral hospital between June 2008 and February 2017. Two endoscopic specialists reviewed the endoscopic findings and divided these diagnoses into 5 groups: Borrmann type (1, 2, 3, and 4) and early gastric cancer-like type. After this, 7 experts and 8 trainees were asked to complete a quiz that was comprised of 6 images for each of the 96 cases and to provide an endoscopic diagnosis for each case. The test results were analyzed to assess the diagnostic accuracy according to the pathologic results, endoscopic subgroups, and endoscopists’ experience. For inter-observer agreement was calculated with Fleiss kappa values.The overall diagnostic accuracy of endoscopic findings by the experts was 0.604 and that by the trainees was 0.493 (P = .050). There was no significant difference in the diagnosis according to the final pathology (lymphoma cases, 0.518 vs 0.440, P = .378; AGC cases, 0.690 vs 0.547, P = .089, respectively). In the subgroup analysis, the experts showed significantly higher diagnostic accuracy for the endoscopic Borrmann type 4 subgroup, including lymphoma or AGC cases, than the trainees (P = .001). Inter-observer agreement of final diagnosis (Fleiss kappa, 0.174) and endoscopic classification groups (Fleiss kappa, 0.123–0.271) was slightly and fair agreement.The experts tended to have a higher endoscopic diagnostic accuracy. Distinguishing MGL from AGC based on endoscopic findings is difficult, especially for the beginners. Even if the endoscopic impression is AGC, it is important to consider MGL in the differential diagnosis.  相似文献   
144.
In the bone marrow (BM) nucleated differential cell count (NDC), myeloblasts are enumerated as a percentage of total nucleated cells, which are inevitably diluted with peripheral blood nucleated cells (PBNC) during BM aspiration. We propose a partial NDC (PNDC) comprising only immature haemopoietic cells capable of division, i.e. myeloblasts, promyelocytes, myelocytes and erythroblasts. We show that the myeloid : erythroid (M : E) ratio of the PNDC remains approximately constant in progressively dilute aliquots of BM aspirates. We determined the PNDC in 22 healthy subjects and investigated the effect of peripheral blood dilution on disease stratification of 66 BM aspirates with myelodysplastic syndromes (MDS). NDC and PNDC myeloblast counts were compared and the equivalent PNDC myeloblast counts for NDC myeloblast threshold counts of 5, 10 and 20% were derived. Reclassification of MDS samples with the PNDC resulted in a change in disease category in 33.3% of 51 MDS samples with NDC myeloblast counts ranging from 3 to 26%. The PNDC is independent of PBNC dilution and can be determined in dilute BM samples. It alters the disease category in a significant proportion of BM aspirates with MDS and has the potential to better stratify MDS to improve clinical outcomes and treatment.  相似文献   
145.
We have investigated the effects of different patterns of administration of recombinant human growth hormone (rhGH) on weight gain, organ growth, serum GH binding protein (GHBP) and insulin-like growth factor-l (IGF-1) levels in a series of studies using hypophysectomized (Hx) or GH-deficient dwarf (dw/dw) rats. Animals were given rhGH either by subcutaneous (s.c.) injections (1 or 2 per day) or s.c. infusions and rhlGF-1 (2 mg/kg/day) by s.c. infusion. In Hx rats, all rhGH regimes increased body weight, tibial epiphyseal plate width, and organ weights in a dose-related manner. Dwarf rats showed a smaller growth response to rhGH than Hx rats, whereas rhGH induced greater elevations in serum GHBP in drarf rats. Growth responses depended on the pattern of rhGH administration (twice daily injections > continuous infusions > daily injections). The shape of the body growth curves also differed; rhGH injections increased weight gain linearly, whereas infusions gave an initial rapid weight gain which slowed with time (a curvilinear response). For both regimens, tibial epiphyseal plate width increased linearly with rhGH dose but infusions were 5-fold more potent than daily injections. Spleen and thymus weights were markedly increased by rhGH and were also affected by the pattern of GH exposure. At 5 mg rhGH/kg/day, thymus weights were 390±35 mg for injectionsvs. 613 ± 34 mg for infusions (P<0.001) compared with 248 ± 16 mg in vehicle-treated Hx controls. Infusions of rhlGF-1 also stimulated specific organ growth but caused less weight gain. RhlGF-1 additively increased the weight gain caused by rhGH injections but not by rhGH infusions. Circulating IGF-1 and GHBP levels were increased in a dose-dependent manner by rhGH infusion, whereas daily injections were ineffective. Thus, differential organ growth could be related to the higher serum IGF-1 concentrations induced by continuous rhGH administration. These studies show that whole body growth is best maintained by intermittent rhGH exposure, whereas, paradoxically, differential organ growth is most pronounced with continuous rhGH administration.  相似文献   
146.
The reorganization kinetics of the “original” lamellar diblock copolymer poly(ε‐caprolactone)‐block‐poly(4‐vinylpyridine) crystals formed at 260 K is studied in the melting region from 270 K (10 K below the onset of the melting peak of original crystals) to 310 K (the melting peak temperature) on the time scale starting from 10?4 to 102 s by ultrafast differential scanning calorimetry. Different reorganization pathways are observed in this temperature range. Annealing at temperatures below 295 K leads to further stabilization of original crystals by secondary crystallization. At annealing temperatures higher than 295 K, crystals partially melt and the reorganization occurs via the melting–recrystallization. For even higher temperature, such as 310 K, the melting is completed within a few milliseconds and recrystallization starts from the nuclei formation. The sigmoidal recrystallization kinetics is analyzed by the Avrami equation. It is found that the copolymer experiences about one order of magnitude slower recrystallization rate and has higher melting peak temperatures of crystals formed after recrystallization than the homopolymer. The slower recrystallization kinetics in the copolymer is discussed from the viewpoint of the nanoscale spatial constraint and the intermediate state prior to the recrystallization.

  相似文献   

147.
目的:探讨3.0T磁共振(MRI)弥散加权成像(DWI)量化指标对肾脏肿瘤性病变的诊断和鉴别诊断价值。方法:收集行肾脏MRI检查并经病理确诊的肾脏实质肿瘤89例。其中,肾细胞癌60例,包括39例肾透明细胞癌、8例乳头状肾细胞癌、9例肾嫌色细胞癌、4例多房囊性肾细胞癌;良性病变29例,包括肾血管平滑肌脂肪瘤25例,嗜酸细胞瘤4例。所有患者采用GE Signa HD 3.0T MR进行横断面DWI成像并行表观弥散系数(apparent diffusion coefficient,ADC)值测量。结果:肾透明细胞癌、乳头状肾细胞癌、肾嫌色细胞癌、多房囊性肾细胞癌ADC平均值分别为(1.681 5±0.176 9)×10~(-3)、(1.165 0±0.217 0)×10~(-3)、(1.121 0±0.231 6)×10~(-3)、(2.030 0±0.235 1)×10~(-3) mm~2/s,肾血管平滑肌脂肪瘤、肾嗜酸细胞瘤ADC平均值分别为(1.155 2±0.132 0)×10~(-3)、(1.580 0±0.212 3)×10~(-3) mm~2/s。肾透明细胞癌ADC值与乳头状肾细胞癌、肾嫌色细胞癌、肾血管平滑肌脂肪瘤ADC值差异均有统计学意义(P=0.000);而与多房囊性肾细胞癌、肾嗜酸细胞瘤ADC值差异无统计意义。结论:3.0T MR-DWI成像ADC值对肾脏肿瘤性病变具有鉴别诊断价值,有利于指导患者治疗方案的选择。  相似文献   
148.
High‐throughput RNA‐sequencing (RNA‐seq) technology provides an attractive platform for gene expression analysis. In many experimental settings, RNA‐seq read counts are measured from matched samples or taken from the same subject under multiple treatment conditions. The induced correlation therefore should be evaluated and taken into account in deriving tests of differential expression. We proposed a novel method ‘PLNseq’, which uses a multivariate Poisson lognormal distribution to model matched read count data. The correlation is directly modeled through Gaussian random effects, and inferences are made by likelihood methods. A three‐stage numerical algorithm is developed to estimate unknown parameters and conduct differential expression analysis. Results using simulated data demonstrate that our method performs reasonably well in terms of parameter estimation, DE analysis power, and robustness. PLNseq also has better control of FDRs than the benchmarks edgeR and DESeq2 in the situations where the correlation is different across the genes but can still be accurately estimated. Furthermore, direct evaluation of correlation through PLNseq enables us to develop a new and more powerful test for DE analysis. Application to a lung cancer study is provided to illustrate the practical utilities of our method. An R package implementing the method is also publicly available. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
149.
目的探讨髓母细胞瘤临床病理学特征及其影响患者预后的主要危险因素。方法收集85例髓母细胞瘤患者的临床病理学资料,观察其组织病理学及免疫学表型特征,分析其临床特点及影响患者预后的相关危险因素。结果 85例髓母细胞瘤患者中男性49例,女性36例,平均发病年龄(9.35±1.18)岁。75例患者病变位于小脑(其中59例位于小脑半球,16例位于小脑蚓部),10例分别位于脊髓(5例)、第四脑室(1例)、大脑颞叶(1例)、大脑额叶(1例)、大脑枕叶(1例)、中脑(1例)。临床表现主要为颅内压增高、共济失调及患侧肢体运动障碍等,部分病人表现为言语不清、记忆力下降及肢体感觉麻木等。免疫组织化学检查:突触素(Syn)阳性表达率为64%,β连环蛋白(β-catenin)阳性表达率为45%,胶质纤维酸性蛋白(GFAP)阳性表达率为50%;NF、CD99肿瘤细胞散在或弱阳性表达;Vimentin、CK、Neu-N、EMA肿瘤细胞呈阴性表达;肿瘤细胞Ki-67增殖指数较高,约为60%。结论髓母细胞瘤儿童多发,预后不良,β-catenin和Ki-67免疫组化染色对其诊断与鉴别诊断有一定参考价值,可能成为髓母细胞瘤判断预后的重要指标。  相似文献   
150.
陈劼 《重庆医学》2015,(17):2389-2391
目的 通过Meta分析已报道文献中的微小RNA-21(microRNA-21,miR-21)对肺癌的诊断价值,探讨血液中的miR-21对肺癌的诊断价值.方法 检索中国知网、维普、万方、PubMed和Embsase等数据库,按照已定的纳入和排出标准筛选文献.采用Quadas量表评估纳入文献质量.通过Stata12和Meta-Disc软件合并纳入文献的诊断值并检测评估异质性和发表偏倚.结果 共检出994篇相关文献,通过筛选,7篇文献(含1 088例样本)纳入本次Meta分析.通过合并文献得出,miR-21对肺癌的诊断灵敏度、特异度、阳性似然比、和阴性似然分别为0.68(95%CI:0.55~0.79),0.82(95%CI:0.76~0.86),3.70(95%CI:2.60~5.25)和0.39(95%CI:0.27~0.58);综合诊断指标综合曲线下面积(SROC)和诊断比值比(DOR)分别为0.84(95%CI:0.80~0.87)和9.90 (95%CI:4.75~20.63).结论 目前研究证据表明,miR-21对肺癌具有较好诊断价值,可作为肺癌诊断的潜在指标.  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