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   2435篇
  免费   177篇
  国内免费   45篇
耳鼻咽喉   17篇
儿科学   122篇
妇产科学   28篇
基础医学   193篇
口腔科学   44篇
临床医学   342篇
内科学   412篇
皮肤病学   47篇
神经病学   118篇
特种医学   288篇
外科学   315篇
综合类   209篇
一般理论   1篇
预防医学   184篇
眼科学   16篇
药学   172篇
  2篇
中国医学   32篇
肿瘤学   115篇
  2022年   34篇
  2021年   41篇
  2020年   36篇
  2018年   26篇
  2017年   28篇
  2016年   26篇
  2015年   42篇
  2014年   56篇
  2013年   97篇
  2012年   98篇
  2011年   93篇
  2010年   107篇
  2009年   115篇
  2008年   85篇
  2007年   87篇
  2006年   91篇
  2005年   64篇
  2004年   63篇
  2003年   71篇
  2002年   58篇
  2001年   49篇
  2000年   34篇
  1999年   38篇
  1998年   88篇
  1997年   83篇
  1996年   80篇
  1995年   77篇
  1994年   46篇
  1993年   55篇
  1992年   26篇
  1991年   26篇
  1990年   26篇
  1989年   47篇
  1988年   52篇
  1987年   48篇
  1986年   35篇
  1985年   40篇
  1984年   26篇
  1983年   26篇
  1982年   16篇
  1980年   17篇
  1978年   18篇
  1977年   20篇
  1963年   17篇
  1959年   22篇
  1958年   29篇
  1957年   19篇
  1956年   30篇
  1955年   42篇
  1954年   35篇
排序方式: 共有2657条查询结果,搜索用时 31 毫秒
61.
Journal of Autism and Developmental Disorders - For over 50 years, intervention methods informed by the principles of applied behavior analysis (ABA) have been empirically researched and...  相似文献   
62.
The purpose of this study was to develop a technique to evaluate the implant-abutment gap of an external hexagon implant system as a function of radius. Six implants of 3.75 mm in diameter (Conexao Sistema de Protese Ltda, Sao Paulo, Brazil) and their respective abutments were screw connected and torqued to 20 N cm(-1). The implants were mounted in epoxy assuring an implant long-axis position perpendicular to the vertical axis. Each implant was grounded through its thickness parallel to implant long-axis at six different distance interval. Implant-abutment gap distances were recorded along the implant-abutment region for each section. Individual measurements were related to their radial position through trigonometric inferences. A sixth degree polynomial line fit approach determined radial adaptation patterns for each implant. Micrographs along implant sections showed a approximately 300 mum length implant-abutment engagement region. All implants presented communication between external and internal regions through connection gaps and inaccurate implant-abutment alignment. Average gap distances were not significantly different between implants (P > 0.086). Polynomial lines showed implant-abutment gap values below 10 mum from 0 mum to approximately 250 mum of the implant-abutment engagement region. Gap distances significantly increased from approximately 250 mum to the outer radius of the implant-abutment engagement region. The technique described provided a broader scenario of the implant-abutment gap adaptation compared with previous work concerning implant-abutment gap determination, and should be considered for better understanding mechanical aspects or biological effects of implant-abutment adaptation on peri-implant tissues.  相似文献   
63.
Standardized instruments are often used to assess the need for mental health services in a community. Such instruments are usually standardized on Caucasian samples and are generally assumed to be appropriate for different ethnocultural minorities. However, this assumption may be in error because cultural groups vary in their expression, manifestation, and reporting of symptoms. This article analyzes the responses to a standardized instrument, the Symptom Checklist (SCL), for four ethnic groups in Hawai'i: Caucasians, Filipinos, Japanese, and Native Hawaiians. Factor analysis using a procrustes rotation was used to force the data to fit into the five hypothesized factors of the SCL (somatization, obsessive-compulsive, interpersonal sensitivity, depression, and anxiety). It showed that the scale item loadings generally did not correspond to the hypothesized factors. Among the ethnic groups, Caucasians appeared to have the best fit between the empirical and hypothesized factors whereas Native Hawaiians had the worst fit. Our results reinforce the importance of assessing established psychiatric symptom scales prior to their use on different ethnocultural minorities.  相似文献   
64.
目的 观察肢带型肌营养不良的MRI表现。方法 回顾性分析7例经临床及病理检查确诊为肢带型肌营养不良患者的MRI资料,观察双侧大腿肌群脂肪沉积与炎性水肿情况,采用4分法进行评价。并进行统计学分析。结果 肢带型肌营养不良患者大腿肌群MRI均可见脂质沉积和炎性水肿性改变。不同肌肉间脂肪沉积(χ2=75.596,P<0.01)与炎性水肿差异均有统计学意义(χ2=41.368,P<0.01),双侧大腿肌群间脂肪沉积与炎性水肿差异均无统计学意义(P均>0.05)。结论 肢带型肌营养不良患者大腿肌群MRI信号特点及分布具有一定特征,MR检查有助于疾病的诊断。  相似文献   
65.

Objective

To determine the frequency of Candida spp., xerostomia, and salivary flow rate (SFR) in three different groups: patients with OLP (OLP group), patients with oral mucosal lesions other than OLP (non‐OLP group), and subjects without oral mucosal lesions (control group).

Material and methods

Xerostomia as well as SFR was investigated in the three groups. Samples for isolation of Candida spp. were collected from OLP lesions (38 patients), non‐OLP lesions (28 patients), and healthy subjects (32 subjects).

Results

There was no statistically significant difference regarding the frequency of xerostomia and hyposalivation among the three groups (P > 0.05). A higher prevalence for colonization by Candida spp. was found in the healthy subject as compared to that of patients with OLP (= 0.03) and non‐OLP (= 0.02) groups. Low SFR was not a factor for colonization by Candida spp.

Conclusions

Xerostomia and hyposalivation occur with similar frequency in subjects with and without oral lesions; also, the presence of oral lesions does not increase the susceptibility to colonization by Candida spp. It seems that any study implicating Candida spp. in the malignant transformation of oral lesions should be carried out mostly on a biochemical basis, that is, by testing the capability of Candida spp. to produce carcinogenic enzyme.  相似文献   
66.
Strain‐dependent induction of allergic rhinitis without adjuvant in mice   总被引:1,自引:0,他引:1  
BACKGROUND: To date, no murine models have been reported to show the induction of both antigen-specific IgE and nasal eosinophilia, two of the major hallmarks of allergic rhinitis, after local sensitization in the absence of adjuvants, a phenomenon which reflects natural exposure. In this report, we attempted to establish a murine model representing an initiation of allergic rhinitis. METHODS: BALB/c, CBA/J, and C57BL/6 mice were sensitized intranasally to Schistosoma mansoni egg antigen (SEA) solely. After repeated sensitization, serum Ab titers, nasal eosinophilia, and cytokine production by nasal lymphocytes were determined. RESULTS: BALB/c mice produced SEA-specific IgE after repeated sensitization. High-dose sensitization to SEA induced IgE production in CBA/J mice, while C57BL/6 mice did not show the production throughout the period observed, suggesting that IgE production was regulated genetically. BALB/c mice also exhibited nasal eosinophilia after the nasal challenge. In addition, nasal lymphocytes sensitized with SEA intranasally produced significant amount of IL-5 in vitro. CONCLUSIONS: These results suggest that intranasal sensitization with SEA in the absence of adjuvants induces a Th2 immune reaction, reflecting the hallmarks of the initiation of allergic rhinitis both in vivo and in vitro, which is genetically regulated.  相似文献   
67.
目的 探讨保乳手术联合腔镜腋窝淋巴结清扫术(MALND)对乳腺癌患者上肢功能、应激反应及血管细胞黏附分子-1 (VCAM-1)、细胞间黏附分子-1(ICAM-1)水平的影响。方法 回顾性分析98例乳腺癌患者的临床资料,依据手术方式的不同分为研究组53例和对照组45例。对照组行保乳手术联合传统腋窝淋巴结清扫术(CALND),研究组行保乳手术联合MALND。比较2组术前、术后6个月上肢功能;收集2组患者术前、术后12 h焦虑自评量表(SAS)、抑郁自评量表(SDS)评分以及心率(HR)、平均动脉压(MAP)水平,并对比2组应激反应程度;比较2组患者术前、术后5 d VCAM-1、ICAM-1水平。结果 术后6个月,研究组前屈、后伸、内收、外展、内旋、外旋活动角度大于对照组,差异有统计学意义(P<0.05);术后12 h,研究组SAS、SDS评分及HR、MAP水平低于对照组,差异有统计学意义(P<0.05);术后5 d,研究组VCAM-1、ICAM-1水平低于对照组,差异有统计学意义(P<0.05)。结论 保乳手术联合MALND对乳腺癌患者上肢功能影响小,术后应激反应程度轻...  相似文献   
68.
69.
Macrophages mediate crucial innate immune responses via caspase-1-dependent processing and secretion of interleukin 1β (IL-1β) and IL-18. Although infection with wild-type Salmonella typhimurium is lethal to mice, we show here that a strain that persistently expresses flagellin was cleared by the cytosolic flagellin-detection pathway through the activation of caspase-1 by the NLRC4 inflammasome; however, this clearance was independent of IL-1β and IL-18. Instead, caspase-1-induced pyroptotic cell death released bacteria from macrophages and exposed the bacteria to uptake and killing by reactive oxygen species in neutrophils. Similarly, activation of caspase-1 cleared unmanipulated Legionella pneumophila and Burkholderia thailandensis by cytokine-independent mechanisms. This demonstrates that activation of caspase-1 clears intracellular bacteria in vivo independently of IL-1β and IL-18 and establishes pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.  相似文献   
70.
Problem: IVIG prepared from plasma of stored human blood can be efficacious in improving pregnancy success in a selected subgroup of patients but RCTs using an IVIG showing inferior suppression of NK activity in vitro have been negative (J Assist Reprod Genet 2006). A significant component of NK suppression by IVIG appears to be due to CD200 released into plasma from PBL during storage at 4C. CD200 receptors (CD200R) are expressed at the fetomaternal interface prior to onset of abortion; CD200R1 mediates direct effects on gamma‐delta T cell development and suppresses alpha‐beta T cell responses in vitro, whereas CD200R2 alters DC so as to facilitate development of alpha‐beta Treg cells. Which receptor(s) mediate NK cell suppression? Methods: Purified human PBL or the CD56+ NK cell subset of PBL were used to lyse 51Cr‐labeled K562 cells in vitro. Different IVIG preparations were tested for suppressive ability, and suppression was blocked by either anti‐huCD200 mAb or rabbit anti‐huCD200R1 or R2 antibodies. Results: CD200‐dependent IVIG NK suppressive potency differed among IVIG types (Gammagard>Gamunex>>Gamimmune). CD200‐dependent suppression was blocked by anti‐CD200R antibody able to react with the type 2 receptor. K562 cells did not express receptor, and purified CD56+ NK cells were suppressed effectively without the need for non‐NK cells. Conclusions: IVIG may directly express NK cell activity via CD200 binding to CD200R2.  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