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   7693篇
  免费   381篇
  国内免费   24篇
耳鼻咽喉   65篇
儿科学   198篇
妇产科学   128篇
基础医学   1153篇
口腔科学   199篇
临床医学   525篇
内科学   1908篇
皮肤病学   127篇
神经病学   635篇
特种医学   213篇
外科学   861篇
综合类   54篇
一般理论   1篇
预防医学   305篇
眼科学   273篇
药学   741篇
中国医学   32篇
肿瘤学   680篇
  2023年   56篇
  2022年   109篇
  2021年   152篇
  2020年   67篇
  2019年   107篇
  2018年   140篇
  2017年   116篇
  2016年   160篇
  2015年   143篇
  2014年   189篇
  2013年   239篇
  2012年   372篇
  2011年   459篇
  2010年   267篇
  2009年   234篇
  2008年   463篇
  2007年   518篇
  2006年   459篇
  2005年   451篇
  2004年   466篇
  2003年   383篇
  2002年   410篇
  2001年   206篇
  2000年   213篇
  1999年   216篇
  1998年   80篇
  1997年   74篇
  1996年   71篇
  1995年   56篇
  1994年   54篇
  1993年   29篇
  1992年   137篇
  1991年   96篇
  1990年   73篇
  1989年   101篇
  1988年   80篇
  1987年   58篇
  1986年   69篇
  1985年   62篇
  1984年   37篇
  1983年   28篇
  1982年   23篇
  1980年   27篇
  1979年   29篇
  1978年   23篇
  1975年   21篇
  1974年   29篇
  1973年   27篇
  1972年   25篇
  1970年   34篇
排序方式: 共有8098条查询结果,搜索用时 15 毫秒
991.
BACKGROUND: Functional neuroimaging studies have implicated hyperactivity of the frontal cortex in obsessive-compulsive disorder (OCD); however, relationships between abnormal brain activity, clinical improvement, and neuropsychological function have not been clarified in OCD. To clarify the pathophysiology of this disorder, regional changes in brain function were examined during administration of cognitive and symptom provocation tasks in patients with OCD before and after treatment. METHODS: Ten outpatients with OCD participated in the study. Functional magnetic resonance imaging (fMRI) was performed before and after treatment. Stroop and symptom provocation tasks were administered during fMRI. Each patient was randomly allocated to receive either pharmacotherapy with fluvoxamine 200 mg/day (n = 4) or behavior therapy (n = 6) for 12 weeks. RESULTS: After 12-week treatment, mean (+/- SD) total score on the Yale-Brown Obsessive-Compulsive Scale decreased from 29.00 +/- 3.59 to 14.60 +/- 9.22, representing symptomatic improvement from moderate to mild. After symptom improvement, symptom provocation-related activation in the orbitofrontal, dorsolateral-prefrontal, and anterior cingulate cortices decreased. Conversely, Stroop task-related activation in the parietal cortex and cerebellum increased. CONCLUSIONS: After improvement of OCD with either fluvoxamine or behavioral therapy, hyperactivation of the frontal lobe related to a symptom-provocative state decreases, and posterior brain activity related to action-monitoring function increases.  相似文献   
992.
Tokai Medical Products developed an intra-aortic balloon pumping (IABP) balloon catheter with the following unique characteristics: the balloon can be applied to any patient irrespective of their physical size, and is therefore suitable for Japanese patients of small stature; a long soft tip is used, which is designed to avoid damage to blood vessels; the size of the catheter is reduced to 7 Fr, and the catheter can be used as a multifunctional balloon catheter, such as the Yoshioka type, that allows simultaneous percutaneous coronary intervention (PCI). The safety of this catheter has been proven in scientific studies. In this review, we report the development of our IABP balloon catheter and give an outline of its characteristics.  相似文献   
993.
994.
995.
We report a suspected early stage of Goldmann-Favre syndrome in a four-year-old girl complaining of poor visual acuity in both eyesOphthalmological examinations were performed including fundus examination, fluorescein angiography, and electrophysiological studies. However, dark adaptation and visual field testing were not performed because of her age.Ophthalmoscopic examinations revealed peripheral retinoschisis in the superior temporal retina, diffusely abnormal retinal pigment epithelium, and lack of macular and foveal reflexes in both eyes. Foveal retinoschisis was not observed and the vitreous did not show severe degeneration. Fluorescein angiography showed many leaking points posterior to the retinoschisis. Scotopic electroretinogram (ERG) was almost non-recordable. Photopic electroretinogram showed a marked reduction of the b-wave with a negative shape and delayed peak time. Flash visual evoked potentials were within normal range.It is very difficult to distinguish this case from X-linked juvenile retinoschisis by ophthalmological findings. However, Goldmann-Favre syndrome is most suspected from the fact that the patient is female and her parents and brothers are normal.  相似文献   
996.
Actinin-4 is an isoform of non-muscular alpha-actinin and actin-bundling protein. By enhancing cell motility, actinin-4 shows different biological properties from another isoform of non-muscular actinin 'actinin-1' and variable clinicopathological implications of actinin-4 have been demonstrated in some human malignancies such as breast cancers, lung cancers, and colorectal cancers. We herein described the clinicopathological and prognostic significance of actinin-4 expression in ovarian cancers. Actinin-4 expression was analyzed immunohistochemically in 265 primary ovarian carcinomas: 116 serous, 71 clear cell, 43 endometrioid, and 35 mucinous adenocarcinomas. With reference to endothelial immunoreactivity, cytoplasmic expression of actinin-4 was classified as either low (including negative) or high. Then, various parameters such as patients' characteristics, histopathological findings including E-cadherin and beta-catenin immunoreactivity, and clinical outcome, were compared between groups showing differences in the intensity or intracellular distribution of actinin-4 immunoreactivity. High expression of actinin-4 was demonstrated in 137 (57%) cases and was associated with serous histology (P=0.0075), high histological grade (P<0.0001), an advanced disease stage (P=0.036), a high degree of residual disease after initial surgery (P=0.0047), poor patient outcome (5-year survival: 52.4% in the high-expression group vs 71.9% in the low expression group, P=0.0043 by log-rank test), and also with reduced E-cadherin and preserved beta-catenin expressions (P=0.0097 and 0.017, respectively). Nuclear immunoreactivity for actinin-4 was detected in 20 (7.5%) cases and was associated with low histological grade (P=0.0079) but not with other variables. Multivariate analysis showed that high actinin-4 expression was an independent prognostic factor for overall survival, as well as a high degree of residual disease and clear-cell histology. Accumulation of actinin-4 in the cytoplasm may be related to a higher propensity for tumor invasiveness and metastasis, probably by enhancing cell motility, and could be a novel prognostic indicator for patients with ovarian carcinomas.  相似文献   
997.
GTPase-activating protein is known to regulate the conversion between ras-GTP and ras-GDP. We studied the basal expression of GTPase-activating protein-like immunoreactivity in mouse cerebral regions using a polyclonal anti-GTPase-activating protein antibody. Cells with GTPase-activating protein-like immunoreactivity were distributed in frontal cortical layers IV and V, and in the parietal cortex, piriform cortex, amygdaloid area, septum, lateral thalamus, and hypothalamus. The GTPase-activating protein-like immunoreactivity was also observed in fiber-like structures in the caudate putamen, stria terminalis, internal capsule, and medial forebrain bundle, and around CA2 pyramidal cells in Ammon’s horn. These results imply that GTPase-activating protein is constitutively expressed in mouse brain regions and may have physiological functions in specific neuronal pathways in the brain.  相似文献   
998.
The effects of sodium channel blockers, propafenone and disopyramide, on post-ischemic contractile dysfunction of perfused rat hearts were examined. Isolated hearts were subjected to 35 min ischemia, followed by 60 min reperfusion with and without administration of either drug during 3 min of pre-ischemia. Ischemia/reperfusion induced complete cardiac dysfunction, rise in left ventricular end-diastolic pressure, increase in perfusion pressure, accumulation of Na+ and Ca2+ and loss of K+ and Mg2+, and release of creatine kinase and purine nucleosides and bases from the heart. These observations suggest that ischemia/reperfusion in the current study induces cardiac cell necrosis or an increase in cell membrane permeability to ions, substrates and macromolecules. Treatment of perfused hearts with either propafenone at concentrations ranging from 5 to 70 μM, or disopyramide at concentrations of 100 μM or higher resulted in a pronounced contractile recovery of the heart, associated with suppression of reperfusion-induced tissue ion alteration and inhibition of reperfusion-induced release of creatine kinase and purine nucleosides and bases. Ischemic insult itself caused tissue Na+ accumulation and K+ loss without any change in tissue Ca2+ and Mg2+. The alterations in the electrolytes were attenuated by treatment with either agent. The results suggest that prevention of ischemia- and reperfusion-induced ionic disturbance of cardiac cells by propafenone and disopyramide plays a role in the improvement of post-ischemic contractile dysfunction.  相似文献   
999.
We have been carrying our mass detection for colorectal cancer with fecal occult blood test and sigmoidoscopy. The occult blood test is negative in 60% with colorectal cancer.  相似文献   
1000.
Clinical Experience of Percutaneous Cardiopulmonary Support   总被引:3,自引:0,他引:3  
Abstract: Recently, percutaneous cardiopulmonary support (PCPS) combined with femoro-femoral bypass without reservoir has become valued because of its quick and easy application. We developed a fully preconnected compact integrated cardiopulmonary bypass (CPB) unit (priming volume of 250 ml) with a blind pore membrane oxygenator (Kuraray Menox) for PCPS. From 1990 to 1995, PCPS was performed in 49 patients of whom 26 were weaned from support. In most cases, we applied this CICU in patients with no active bleeding (22 patients); in patients with active bleeding (n = 13), we used Medtron-ic's heparin-bonded close chest support pack (CCSP). Of these, PCPS was performed uneventfully for 2 h (median) in 8 elective cases; all of these patients were weaned or were switched to a left ventricular assist system (LVAS). In 8 urgent cases, such as those with low cardiac output syndrome, PCPS was performed for 4 days (median), 1 was weaned, and 2 CICU were cases switched to other procedures. In 32 cases of shock, 5 CICU patients were weaned, and 3 of them survived. Eight patients including 5 CICU patients and 1 CCSP patient were switched to operation or LVAS, and 2 CICU patients remain alive. From these data, PCPS has been shown to support the patient's circulation in the acute phase and earn time to switch to operation or LVAS; the quick and easy set-up of the CICU can improve the clinical results. The use of the Medtronic device broadened the indication for PCPS. The CCSP enlarged the indication of PCPS but could not improve the results. To improve the results, a heparin-bonded surface is desired.  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