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   33197篇
  免费   2386篇
  国内免费   486篇
耳鼻咽喉   644篇
儿科学   655篇
妇产科学   701篇
基础医学   4688篇
口腔科学   575篇
临床医学   2752篇
内科学   7495篇
皮肤病学   1011篇
神经病学   2213篇
特种医学   1803篇
外科学   4483篇
综合类   565篇
一般理论   15篇
预防医学   1391篇
眼科学   964篇
药学   2804篇
中国医学   341篇
肿瘤学   2969篇
  2023年   225篇
  2022年   585篇
  2021年   1004篇
  2020年   511篇
  2019年   824篇
  2018年   992篇
  2017年   725篇
  2016年   947篇
  2015年   1297篇
  2014年   1537篇
  2013年   1782篇
  2012年   2496篇
  2011年   2556篇
  2010年   1598篇
  2009年   1393篇
  2008年   1874篇
  2007年   1807篇
  2006年   1638篇
  2005年   1548篇
  2004年   1306篇
  2003年   1257篇
  2002年   1148篇
  2001年   770篇
  2000年   687篇
  1999年   660篇
  1998年   347篇
  1997年   312篇
  1996年   298篇
  1995年   233篇
  1994年   224篇
  1993年   137篇
  1992年   319篇
  1991年   251篇
  1990年   277篇
  1989年   288篇
  1988年   272篇
  1987年   226篇
  1986年   203篇
  1985年   185篇
  1984年   152篇
  1983年   120篇
  1982年   99篇
  1981年   86篇
  1980年   85篇
  1979年   129篇
  1978年   88篇
  1977年   75篇
  1976年   57篇
  1975年   68篇
  1974年   53篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
BACKGROUND: This study investigated the utility of the alveolar - arterial oxygen pressure difference (AaDO (2)) in predicting the short-term prognosis of acute pulmonary embolism (PE). METHODS AND RESULTS: This study retrospectively enrolled 114 consecutive patients with acute PE, diagnosed by either spiral computed tomography or high probability ventilation - perfusion lung scans. During the first 24 h of admission, all patients had initial artery blood gas collected under room air. Patient exclusion criteria were chronic lung disease, septic emboli, and moderate and low probability lung scans. Patients were assigned to 2 groups based on either 30-day death or a 30-day composite event. Receiver operating characteristic analyses was used to determine the AaDO(2) cut-off value for predicting primary and composite endpoints. Statistical analysis demonstrated significant differences in AaDO(2) between the 30-day composite endpoint group and the 30-day composite event-free survival group (p=0.012). The AaDO(2) had a strong trend between the 30-day death group and the survival group (p=0.062). The best cut-off value for AaDO(2) was 53 mmHg and using this, the positive predictive value for 30-day death was 25% and the negative predictive value was 92%. For the 30-day composite endpoint, the positive predictive value for AaDO(2) was 35%, and the negative predictive value was 84%. In this study, thrombocytopenia was also an indicator of poor prognosis for patients with acute PE. CONCLUSION: The AaDO(2) measurement is a highly useful and simple measurement for predicting short-term prognosis in patients with acute PE. It has high negative predictive value and moderate positive predictive value for 30-day death and 30-day composite event. Aggressive thrombolytic treatment strategies should be considered for patients with an initial poor prognostic parameter (ie, AaDO(2) >or=53 mmHg).  相似文献   
82.
83.
84.
85.
86.
Amniotic fluid mesenchymal stem cells have the ability to secrete neurotrophic factors that are able to promote neuron survival in vitro. The purpose of this study was to evaluate the effects of neurotrophic factors secreted by rat amniotic fluid mesenchymal stem cells on regeneration of sciatic nerve after crush injury. Fifty Sprague-Dawley rats weighing 250-300 g were used. The left sciatic nerve was crushed with a vessel clamp. Rat amniotic fluid mesenchymal stem cells embedded in fibrin glue were delivered to the injured nerve. Enzyme-linked immunosorbent assay (ELISA) and immunocytochemistry were used to detect neurotrophic factors secreted by the amniotic fluid mesenchymal stem cells. Nerve regeneration was assessed by motor function, electrophysiology, histology, and immunocytochemistry studies. Positive CD29/44, and negative CD11b/45, as well as high levels of expression of brain-derived neurotrophic factor, glia cell line-derived neurotrophic factor, ciliary neurotrophic factor (CNTF), nerve growth factor, and neurotrophin-3 (NT-3) were demonstrated in amniotic fluid mesenchymal stem cells. Motor function recovery, the compound muscle action potential, and nerve conduction latency showed significant improvement in rats treated with amniotic fluid mesenchymal stem cells. ELISA measurement in retrieved nerves displayed statistically significant elevation of CNTF and NT-3. The immunocytochemical studies demonstrated positive staining for NT-3 and CNTF in transplanted cells. The histology and immunocytochemistry studies revealed less fibrosis and a high level of expression of S-100 and glial fibrillary acid protein at the crush site. Rat amniotic fluid mesenchymal stem cells may facilitate regeneration in the sciatic nerve after crush injury. The increased nerve regeneration found in this study may be due to the neurotrophic factors secreted by amniotic fluid mesenchymal stem cells.  相似文献   
87.
OBJECTIVE: Although cutaneous leishmaniasis (CL) occurs mostly in the facial area, periocular involvement accounts for 2-5% of the facial lesions. CL lesions localized in the periocular region can easily be confused with various other diseases. The aim of this study was to examine the frequency of periocular involvement in CL in the Cukurova region of Turkey, as well as the clinical characteristics, diagnosis and methods of treatment of this disease. METHODS: Between December 1998 and December 2004, patients who were diagnosed with CL were evaluated prospectively with respect to periocular involvement. RESULTS: From the 2066 patients evaluated with CL, 2622 lesions were identified. In 59 (2.9%) of these patients, a total of 66 (2.5%) lesions were located in the periocular area. Thirty-two (48.5%) of these lesions were of the papular type, 15 (22.7%) the nodulo-ulcerative type, 10 (15.2%) the plaque type, and nine (13.6%) the nodular type. Dacryocystitis was identified in four patients with periocular involvement. Over the follow-up period, no ocular or periocular deformities or complications developed in these patients. CONCLUSION: Patients suspected of CL should be evaluated and treated early in the course of their disease to prevent any permanent ocular or periocular deformities.  相似文献   
88.
89.
90.
The retrosplenial cortex is a cytoarchitecturally distinct brain structure located in the posterior cingulate gyrus and bordering the splenium, precuneus, and calcarine fissure. Functional imaging suggests that the retrosplenium is involved in memory, visuospatial processing, proprioception, and emotion.We report on a patient who developed reversible verbal and visual memory deficits following a stroke. Neuropsychological testing revealed both anterograde and retrograde memory deficits in verbal and visual modalities. Brain diffusion-weighted and T2-weighted magnetic resonance imaging (MRI) demonstrated an acute infarction of the left retrosplenium.  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