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   4144篇
  免费   307篇
  国内免费   5篇
耳鼻咽喉   51篇
儿科学   91篇
妇产科学   49篇
基础医学   572篇
口腔科学   55篇
临床医学   562篇
内科学   770篇
皮肤病学   32篇
神经病学   444篇
特种医学   91篇
外科学   327篇
综合类   48篇
预防医学   610篇
眼科学   79篇
药学   337篇
中国医学   22篇
肿瘤学   316篇
  2024年   9篇
  2023年   33篇
  2022年   41篇
  2021年   105篇
  2020年   78篇
  2019年   90篇
  2018年   122篇
  2017年   91篇
  2016年   103篇
  2015年   103篇
  2014年   146篇
  2013年   226篇
  2012年   371篇
  2011年   342篇
  2010年   169篇
  2009年   148篇
  2008年   266篇
  2007年   310篇
  2006年   244篇
  2005年   277篇
  2004年   275篇
  2003年   213篇
  2002年   219篇
  2001年   35篇
  2000年   29篇
  1999年   31篇
  1998年   42篇
  1997年   29篇
  1996年   20篇
  1995年   19篇
  1994年   29篇
  1993年   21篇
  1992年   6篇
  1991年   13篇
  1990年   14篇
  1989年   15篇
  1988年   12篇
  1987年   11篇
  1986年   9篇
  1985年   8篇
  1984年   19篇
  1983年   12篇
  1982年   11篇
  1981年   9篇
  1980年   10篇
  1977年   5篇
  1974年   5篇
  1972年   6篇
  1971年   6篇
  1969年   6篇
排序方式: 共有4456条查询结果,搜索用时 15 毫秒
71.

Objective

Newborn screening (NBS) identifies genetic carriers for sickle cell hemoglobinopathy and cystic fibrosis. We aimed to identify factors during initial NBS carrier results disclosure by primary care providers (PCPs) that influenced parents’ experiences and reactions.

Methods

Open-ended responses from telephone interviews with 270 parents of carriers were analyzed using mixed-methods. Conventional content analysis identified influential factors; chi-square tests analyzed relationships between factors and parent-reported reactions.

Results

Parents reported positive (35%) or negative (31%) reactions to results disclosure. Parents’ experiences were influenced by specific factors: content messages (72%), PCP traits (47%), and aspects of the setting (30%). Including at least one of five specific content messages was associated (p < 0.05) with positive parental reactions; omitting at least one of four specific content messages was associated (p < 0.05) with negative parental reactions. Parents reported positive reactions when PCPs avoided jargon or were perceived as calm. Parents reported negative reactions to jargon usage and results disclosure by voicemail.

Conclusion

Parents identified aspects of PCP communication which influenced their reactions and results disclosure experiences.

Practice implications

Our findings suggest ways PCPs may improve communication of carrier results. PCPs should provide specific content messages and consider how their actions, characteristics, and setting can influence parental reactions.  相似文献   
72.
73.
The amplitude and duration of Ca2+ signaling is crucial for B-cell development and self-tolerance; however, the mechanisms for terminating Ca2+ signals in B cells have not been determined. In lymphocytes, plasma membrane Ca2+ ATPase (PMCA) isoforms 1 and 4 (PMCA1 and PMCA4, aka ATP2B1 and ATP2B4) are the main candidates for expelling Ca2+ from the cell through the plasma membrane. We report here that Pmca4 (Atp2b4) KO mice had normal B-cell development, while mice with a conditional KO of Pmca1 (Atp2b1) had greatly reduced numbers of B cells, particularly splenic follicular B cells, marginal zone B cells, and peritoneal B-1a cells. Mouse and naïve human B cells showed only PMCA1 expression and no PMCA4 by western blot, in contrast to T cells, which did express PMCA4. Calcium handling was normal in Pmca4−/− B cells, but Pmca1 KO B cells had elevated basal levels of Ca2+, elevated levels in ER stores, and reduced Ca2+ clearance. These findings show that the PMCA1 isoform alone is required to ensure normal B-cell Ca2+ signaling and development, which may have implications for therapeutic targeting of PMCAs and Ca2+ in B cells.  相似文献   
74.
75.
76.
BACKGROUND: Advances in multidetector computed tomography (MDCT) technology now permit three-dimensional cardiac imaging with high spatial and temporal resolution. Historically, transesophageal echocardiography (TEE) has been the gold standard for assessment of the left atrial appendage (LAA) in patients with atrial fibrillation and other atrial arrhythmias. Findings on TEE, including demonstration of LAA thrombus and dense nonclearing spontaneous echocardiographic contrast (SEC), predict future fatal and nonfatal thromboembolic events. OBJECTIVE: The purpose of this study was to compare the diagnostic performance of 64-detector row MDCT in detecting LAA thrombus and dense nonclearing SEC as identified by TEE in patients undergoing pulmonary vein isolation for treatment of atrial fibrillation. METHODS: A total of 72 consecutive patients (69.4% male; mean age 56.1 +/- 10.3 years) underwent both MDCT and TEE for evaluation of the LAA (median intertest interval 0 days, interquartile range 0-5 days). MDCT assessment of the LAA was performed by two methods: (1) comparison of Hounsfield unit (HU) densities in the LAA apex to the ascending aorta (AscAo) in the same axial plane and (2) nonquantitative visual identification of a filling defect in the LAA. TEE evaluation of the LAA included identification of echodense intracavitary masses in the LAA as well as pulsed-wave Doppler interrogation of the LAA ostium. RESULTS: Patients with LAA thrombus or dense nonclearing SEC by TEE exhibited significantly lower LAA/AscAo HU ratios than patients who did not (0.82 +/- 0.22 vs 0.39 +/- 0.19, P <.001). LAA/AscAo HU cutoff ratios < or = 0.75 correlated to LAA thrombus or dense nonclearing SEC by TEE, with 100% sensitivity, 72.2% specificity, 28.6% positive predictive value, and 100% negative predictive value. HU ratios < or = 0.75 were associated with pulsed-wave Doppler velocities <50 cm/s of the LAA ostium (P <.001). In multivariable analysis, LAA/AscAo HU ratio < or = 0.75 remained a robust predictor of LAA thrombus or dense nonclearing SEC by TEE (P <.001). In contrast, MDCT identification of TEE-identified LAA thrombus or dense nonclearing SEC by visual detection of LAA filling defects resulted in lower sensitivity (50%) and negative predictive value (95.1%). CONCLUSION: Current-generation MDCT successfully identifies LAA thrombus and dense nonclearing SEC with high sensitivity and moderate specificity. Importantly, LAA/AscAo HU ratios >0.75 demonstrate 100% negative predictive value for exclusion of LAA thrombus or dense nonclearing SEC. These results suggest that in patients undergoing pulmonary vein isolation procedures, MDCT examinations that demonstrate LAA/AscAo HU ratios >0.75 may preclude the need for preprocedural TEE.  相似文献   
77.
Understanding fertility desires and preferences for HIV prevention among individuals living with HIV, including the potential use of pre-exposure prophylaxis (PrEP) by HIV uninfected partners, can inform the delivery of safer conception counseling to reduce the risk of HIV transmission during pregnancy attempts. Men and women, predominantly heterosexual, engaged in HIV care in Seattle, WA, self-administered a questionnaire and we abstracted antiretroviral therapy (ART) status and HIV viral levels from medical records. We summarized participants’ sexual behavior, fertility desires, and preferences for safer conception strategies and used log-binomial regression to identify demographic, sexual, and behavioral factors associated with perceived acceptability of PrEP for HIV uninfected partners during pregnancy attempts. 52% of the 150 participants were female and the mean age was 48 years (range 23–74). 94.7% of participants were using ART and 79.3% had HIV viral load < 40 copies/mL. 22.2% of men and 34.6% of women reported that a healthcare provider had initiated discussion about fertility desires. 28.7% of participants were reproductive-age and desired children. Among sexually active reproductive-age participants with fertility desires, 56.3% reported inconsistent condom use and 62.5% did not report using effective birth control. 74.4% of reproductive age participants with fertility desires perceived that PrEP would be acceptable to an HIV uninfected partner and there were no significant predictors of PrEP acceptability. Nearly one third of reproductive-aged individuals living with HIV expressed fertility desires, highlighting a need for safer conception counseling in this setting. PrEP and ART were favored safer conception strategies.  相似文献   
78.
The objective of this study was to investigate the risk of attenuated efficacy due to adaptive resistance for the siderophore-conjugated monocarbam SMC-3176 in Pseudomonas aeruginosa by using a pharmacokinetic/pharmacodynamic (PK/PD) approach. MICs were determined in cation-adjusted Mueller-Hinton broth (MHB) and in Chelex-treated, dialyzed MHB (CDMHB). Spontaneous resistance was assessed at 2× to 16× the MIC and the resulting mutants sequenced. Efficacy was evaluated in a neutropenic mouse thigh model at 3.13 to 400 mg/kg of body weight every 3 h for 24 h and analyzed for association with free time above the MIC (fT>MIC). To closer emulate the conditions of the in vivo model, we developed a novel assay testing activity mouse whole blood (WB). All mutations were found in genes related to iron uptake: piuA, piuC, pirR, fecI, and pvdS. Against four P. aeruginosa isolates, SMC-3176 displayed predictable efficacy corresponding to the fT>MIC using the MIC in CDMHB (R2 = 0.968 to 0.985), with stasis to 2-log kill achieved at 59.4 to 81.1%. Efficacy did not translate for P. aeruginosa isolate JJ 4-36, as the in vivo responses were inconsistent with fT>MIC exposures and implied a threshold concentration that was greater than the MIC. The results of the mouse WB assay indicated that efficacy was not predictable using the MIC for JJ 4-36 and four additional isolates, against which in vivo failures of another siderophore-conjugated β-lactam were previously reported. SMC-3176 carries a risk of attenuated efficacy in P. aeruginosa due to rapid adaptive resistance preventing entry via the siderophore-mediated iron uptake systems. Substantial in vivo testing is warranted for compounds using the siderophore approach to thoroughly screen for this in vitro-in vivo disconnect in P. aeruginosa.  相似文献   
79.
80.
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