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   2837篇
  免费   153篇
  国内免费   31篇
耳鼻咽喉   74篇
儿科学   64篇
妇产科学   72篇
基础医学   448篇
口腔科学   42篇
临床医学   241篇
内科学   651篇
皮肤病学   91篇
神经病学   199篇
特种医学   91篇
外科学   446篇
综合类   13篇
预防医学   133篇
眼科学   48篇
药学   145篇
中国医学   1篇
肿瘤学   262篇
  2023年   33篇
  2022年   43篇
  2021年   90篇
  2020年   51篇
  2019年   61篇
  2018年   89篇
  2017年   64篇
  2016年   75篇
  2015年   89篇
  2014年   108篇
  2013年   144篇
  2012年   197篇
  2011年   215篇
  2010年   133篇
  2009年   101篇
  2008年   169篇
  2007年   173篇
  2006年   178篇
  2005年   191篇
  2004年   184篇
  2003年   142篇
  2002年   126篇
  2001年   27篇
  2000年   29篇
  1999年   26篇
  1998年   29篇
  1997年   23篇
  1996年   26篇
  1995年   18篇
  1994年   13篇
  1993年   9篇
  1992年   22篇
  1991年   11篇
  1990年   10篇
  1989年   22篇
  1988年   11篇
  1987年   8篇
  1986年   8篇
  1985年   12篇
  1984年   3篇
  1983年   9篇
  1981年   3篇
  1980年   5篇
  1979年   5篇
  1976年   8篇
  1975年   3篇
  1968年   3篇
  1966年   2篇
  1964年   2篇
  1963年   2篇
排序方式: 共有3021条查询结果,搜索用时 15 毫秒
91.
The introduction of biological therapies, particularly anti-TNFα agents, has revolutionized the management of inflammatory bowel disease in those cases which are refractory to conventional treatment; however these drugs are not risk-free and their use has substantially increased the cost of treatment. As marketing protection expires for original, first-generation biopharmaceuticals, lower-cost “copies” of these drugs produced by competitor companies—referred to as biosimilars—are already entering the market. In September 2013, the European Medicines Agency approved two infliximab biosimilars for treatment of adult and paediatric inflammatory bowel disease patients, a decision based largely on efficacy and safety data generated in studies of patients with ankylosing spondylitis and rheumatoid arthritis. For many clinicians, extrapolation practices and the general question of interchangeability between biosimilars and reference biologics are cause for concern. In the present paper, the Italian Group for inflammatory bowel disease presents its statements on these issues, with emphasis on the peculiar clinical characteristics of inflammatory bowel disease and the importance of providing physicians and patients with adequate information and guarantees on the safety and efficacy of these new drugs in the specific setting of inflammatory bowel disease.  相似文献   
92.
93.
94.
95.
This study hypothesized that the well-being of community residents in remission from major depression disorder (MDD) would not be significantly different from those without MDD. Data from the Midlife in the United States Survey (MIDUS), a prospective general population survey conducted in 1995 and 2004, were analysed. A comparison of the psychological well-being scores, Big Five personality scores and life satisfaction scores of remitted and non-remitted respondents revealed generally small effect size differences. The remitted group were more likely than the non-remitted group to have had past-year panic disorder at follow-up. In general, these results suggest that the well-being of respondents in MDD remission was relatively high.  相似文献   
96.
We investigated the signal transmission pathway by which activation of μ-opioid receptors attenuates acetylcholine (ACh) release in bovine trachealis. Electrical stimulation (ES)-induced [3H]-ACh release was determined in bovine tracheal smooth muscle strips pre-incubated with either the Gi-protein inhibitor pertussis toxin (PTX, 500 ng/ml and 1 μg/ml) or the Gz-protein specific inhibitor arachidonic acid (AA, 10−6 M and 10−5 M) and then treated with DAMGO (D-Ala2,N-MePhe4,Gly-ol5-enkephalin) 10−5 M. Indomethacin 10−5 M was used to block AA cascade. The inhibitory effect of DAMGO on ES-induced [3H]-ACh release was PTX-insensitive, but, by contrast, ablated by AA in a concentration-dependent manner. AA 10−5 M alone reduced [3H]-ACh release, an effect that was prevented by iberiotoxin 10−7 M, suggesting an involvement of Ca2+-activated K+-channels. Western blot analysis consistently showed immunoreactive bands against a specific antibody anti-Gz-α subunit at ∼40 kDa, consistent with the presence of Gz-protein. The present findings suggest that in isolated bovine trachealis, activation of μ-opioid receptors inhibits ACh-release through a signal transmission pathway involving Gz-protein rather than Gi-protein.  相似文献   
97.
A subset of over-expressed microRNAs (miRNAs) identified in parathyroid carcinomas (Ca) compared to normal glands belongs to C19MC, a cluster on chromosome 19q13.4 involved in stem cell biology and tumourigenesis. In this study, the expression of C19MC-MIR371-3 clusters and the molecular mechanisms presiding their modulation were investigated in a series of six normal parathyroids, 24 adenomas (Ad), 15 Ca and five matched metastases. The general expression levels of C19MC or MIR371-3 clusters in Ad lesions did not differ from normal glands, while they distinguished Ad from Ca at unsupervised hierarchical cluster analysis (P=0.0008). MIR517C showed the most significant difference in expression between Ca and Ad (P=0.0003) and it positively correlated with serum calcium, parathormone and tumour weight. In regard to the molecular mechanism determining C19MC cluster activation, we could detect C19MC copy number (CN) gain in ten Ca (67%) extending distal to the MIR371-3 cluster in almost all samples. Conversely, only four Ad (16%) showed C19MC amplification, with one case presenting distal genomic aberration to MIR371-3. Globally, CN variations of 19q13.4 loci were significantly associated with MIR517C up-regulation (P=0.006). Opposite to normal glands where C19MC promoter was methylated, hypomethylation occurred in 15 out of 30 analysed tumours. Though the epigenetic status did not correlate with C19MC miRNA expression levels, loss of C19MC promoter methylation was significantly associated with Ca and metastatic disease (P=0.01). In conclusion, C19MC cluster aberrations are a characteristic of Ca with respect to Ad. Altogether, these evidences point towards a role for 19q13.4 miRNA clusters as oncogenes in parathyroid tumourigenesis.  相似文献   
98.
BackgroundThere is no gold standard for the differential diagnosis of acute dyspnea despite the usefulness of N-terminal pro–B-type natriuretic peptide (NT-proBNP) and lung ultrasound. No study has evaluated the contribution of bioelectrical impedance vector analysis (BIVA) in discriminating between cardiac and noncardiac dyspnea. We sought to determine whether a relationship exists between ultrasound detection of lung congestion, NT-proBNP, and BIVA in patients with acute dyspnea.Methods and ResultsEligible patients were between 50 and 95 years, with an estimated glomerular filtration rate of ≥30 mL min?1 1.73 m?2, who presented to an emergency department with dyspnea. Dyspnea was classified by reviewers blinded to BIVA as cardiac or noncardiac based on physical examination, electrocardiogram, chest X-ray, NT-proBNP, and B-lines of lung congestion on ultrasound. Overall, 315 patients were enrolled (median age 77 years, 48% male). An adjudicated diagnosis of cardiac dyspnea was established in 169 (54%). Using BIVA, vector positions below ?1 SD of the Z-score of reactance were associated with peripheral congestion (χ2 = 115; P < .001). BIVA measures were reasonably accurate in discriminating cardiac and noncardiac dyspnea (69% sensitivity, 79% specificity, 80% area under the receiver operating characteristic curve).ConclusionsIn patients presenting with acute dyspnea, the combination of BIVA and lung ultrasound may provide a rapid noninvasive method to determine the cause of dyspnea.  相似文献   
99.
100.
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