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   18823篇
  免费   1217篇
  国内免费   124篇
耳鼻咽喉   193篇
儿科学   256篇
妇产科学   254篇
基础医学   2547篇
口腔科学   444篇
临床医学   1764篇
内科学   3826篇
皮肤病学   506篇
神经病学   2106篇
特种医学   1210篇
外科学   3561篇
综合类   112篇
一般理论   5篇
预防医学   630篇
眼科学   209篇
药学   1182篇
中国医学   14篇
肿瘤学   1345篇
  2024年   11篇
  2023年   171篇
  2022年   270篇
  2021年   503篇
  2020年   340篇
  2019年   450篇
  2018年   513篇
  2017年   424篇
  2016年   515篇
  2015年   640篇
  2014年   780篇
  2013年   876篇
  2012年   1486篇
  2011年   1594篇
  2010年   970篇
  2009年   897篇
  2008年   1324篇
  2007年   1350篇
  2006年   1268篇
  2005年   1187篇
  2004年   1072篇
  2003年   981篇
  2002年   924篇
  2001年   192篇
  2000年   152篇
  1999年   183篇
  1998年   154篇
  1997年   162篇
  1996年   87篇
  1995年   84篇
  1994年   70篇
  1993年   48篇
  1992年   60篇
  1991年   44篇
  1990年   40篇
  1989年   36篇
  1988年   32篇
  1987年   26篇
  1986年   32篇
  1985年   20篇
  1984年   20篇
  1983年   17篇
  1982年   14篇
  1980年   12篇
  1978年   13篇
  1975年   12篇
  1974年   8篇
  1973年   11篇
  1971年   8篇
  1970年   8篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
941.
942.
Invasion of the nervous system and neuronal spread of infection are critical, but poorly understood steps in the pathogenesis of prion diseases. We have thus analyzed the internalization and signal transduction of the neurotoxic fragment of the prion protein PrP106–126 in the rat neuroblastoma cell line B104 by fluorescence microscopy and quantification by ELISA and in primary neuronal cells from mice. Phospholipase D (PLD) is known to be an enzyme involved in the regulation of secretion, endocytosis and receptor signalling. We determined the PLD activity using a transphosphatidylation assay and could show that PLD is involved in PrP106–126 internalization. The determination of receptor activity via quantification of ERK1/2 phosphorylation and cAMP level measurement verified the PrP106–126-induced signal transduction in B104 cells and primary neuronal cells. PrP106−126-induced a decrease in cAMP level in neuronal cells. These studies indicate the involvement of PLD in PrP106–126-endocytosis and mediated cellular signalling by an unidentified inhibitory G-protein-coupled receptor and may allow the development of therapeutic agents interfering with prion uptake and/or PLD function using PLD as a possible pharmaceutical target.  相似文献   
943.
This is a case report of a 14-year-old girl with a triplane fracture of the distal fibula. The fracture showed displacement and was treated by open reduction, internal fixation, and 5 weeks of external immobilization. The follow-up 5 months after injury yielded an excellent clinical result. Triplane fractures are also seen in locations other than the growth plate of the distal tibia. Due to the occurrence close to the end of the growth period, the potential for growth deformity is negligible. There has been no previous report of a transitional fracture in this location.  相似文献   
944.
Electrical cardiac forces have been previously hypothesized to play a significant role in cardiac morphogenesis and remodeling. In response to electrical forces, cultured cardiomyocytes rearrange their cytoskeletal structure and modify their gene expression profile. To translate such in vitro data to the intact heart, we used a collection of zebrafish cardiac mutants and transgenics to investigate whether cardiac conduction could influence in vivo cardiac morphogenesis independent of contractile forces. We show that the cardiac mutant dcos226 develops heart failure and interrupted cardiac morphogenesis following uncoordinated ventricular contraction. Using in vivo optical mapping/calcium imaging, we determined that the dco cardiac phenotype was primarily due to aberrant ventricular conduction. Because cardiac contraction and intracardiac hemodynamic forces can also influence cardiac development, we further analyzed the dco phenotype in noncontractile hearts and observed that disorganized ventricular conduction could affect cardiomyocyte morphology and subsequent heart morphogenesis in the absence of contraction or flow. By positional cloning, we found that dco encodes Gja3/Cx46, a gap junction protein not previously implicated in heart formation or function. Detailed analysis of the mouse Cx46 mutant revealed the presence of cardiac conduction defects frequently associated with human heart failure. Overall, these in vivo studies indicate that cardiac electrical forces are required to preserve cardiac chamber morphology and may act as a key epigenetic factor in cardiac remodeling.  相似文献   
945.
Remote ischemic preconditioning (RIPC) with transient upper limb ischemia reduces myocardial injury in patients undergoing on-pump coronary artery bypass grafting (CABG) with cross-clamp fibrillation or blood cardioplegia for myocardial protection. Whether or not such protection is still operative when standard crystalloid cardioplegic arrest is used is uncertain. Fifty-three consecutive, non-diabetic patients with triple-vessel disease and 64 ± 12 years of age (mean ± SD), who underwent elective CABG surgery with crystalloid (Bretschneider) cardioplegic arrest, were allocated in a prospective, randomized, single-blinded protocol to receive either a RIPC protocol (3 cycles of 5 min transient left upper arm ischemia induced by inflating a blood pressure cuff to 200 mmHg with 5 min of reperfusion) or control, respectively, after induction of anesthesia. Cardiac troponin I (cTnI) concentration was measured preoperatively and over 72 h postoperatively, and the area under the curve (AUC) was calculated. Peak postoperative cTnI concentration was significantly reduced from 13.7 ± 7.7 ng/mL in controls to 8.9 ± 4.4 ng/mL in RIPC (P = 0.008). Mean cTnI concentration was significantly lower at 6, 12, 24, and 48 h after surgery (ANOVA; P < 0.0001) in the RIPC patients (N = 27) than in controls (N = 26), resulting in a 44.5% reduction of cTnI (AUC at 72 h). RIPC by repetitive inflation of a cuff around the left upper arm before surgery enhances myocardial protection in patients undergoing CABG surgery with antegrade cold crystalloid cardioplegia.  相似文献   
946.
947.
Objective: The DeBakey classification was used to discriminate the extent of acute aortic dissection (AD) and was correlated to long-term outcome and re-intervention rate. A slight modification of type II subgroup definition was applied by incorporating the aortic arch, when full resectability of the dissection process was given. Methods: Between January 2001 and March 2010, 118 patients (64% male, mean age 59 years) underwent surgery for acute AD. As many as 74 were operated on for type I and 44 for type II AD. Complete resection of all entry sites was performed, including antegrade stent grafting for proximal descending lesions. Results: Patients were comparable with respect to demographics and preoperative hemodynamic status. They underwent isolated ascending replacement, hemiarch, or total arch replacement in 7%, 26%, and 67% in type I, versus 27%, 37%, and 36% in type II, respectively. Additional descending stent grafting was performed in 33/74 (45%) type I patients. In-hospital mortality was 14%, 16% (12/74) in type I versus 9% (4/44, type II), p = 0.405. After 5 years, the estimated survival rate was 63% in type I versus 80% in type II, p = 0.135. In type II, no distal aortic re-intervention was required. In type I, the freedom of distal re-interventions was 82% in patients with additional stent grafting versus 53% in patients without, p = 0.022. Conclusions: The slightly modified DeBakey classification exactly reflects late outcome and aortic re-intervention probability. Thus, in type II patients, the aorta seems to be healed without any probability of later re-operation or re-intervention.  相似文献   
948.
949.
Background: Plasmacytoid dendritic cells (PDC) play a pivotal role in the induction of autoimmune diseases and other skin diseases. The present study focuses on the distribution patterns of PDC in patients with cutaneous lupus erythematosus (LE) and Jessner's lymphocytic infiltrate (LI) of the skin and compares them with other skin diseases. The goal was to scrutinize the involvement of PDC in LI, and to show that PDC present a specific pattern of distribution in various cutaneous disorders. Methods: 353 skin biopsies of LE (various subtypes), LI, and other inflammatory skin diseases as well as two halo melanocytic nevi and 10 epithelial tumors were immunohistochemically investigated for the presence of PDC by employing antibodies against CD123 and CD2AP. Results: PDC were constantly detected as distinct perivascular and periadnexal clusters in LE and LI. In other forms of dermatitis, PDC could be found as single cells or scattered throughout the infiltrate or beneath the epidermis. Conclusions: Our data suggest that the distribution of PDC in tumid LE and LI is identical, and this observation suggests that both designations signify one disease. The distinct PDC arrangement in LE represents as useful diagnostic tool in the differential diagnosis with other forms of dermatitis. Tomasini D, Mentzel T, Hantschke M, Cerri A, Paredes B, Rütten A, Schärer L, Kutzner H. Plasmacytoid dendritic cells: an overview of their presence and distribution in different inflammatory skin diseases, with special emphasis on Jessner's lymphocytic infiltrate of the skin and cutaneous lupus erythematosus.  相似文献   
950.
Recent neuroanatomical and functional neuroimaging studies indicate that the anterior part of the hippocampus, rather than the whole structure, may be specifically involved in episodic memory. In the present work, we examined whether anterior structural measurements are superior to other regional or global measurements in mapping functionally relevant degenerative alterations of the hippocampus in Alzheimer's disease (AD).Twenty patients with early AD (MMSE 25.7 ± 1.7) and 18 healthy controls were studied using magnetic resonance and diffusion-tensor imaging. Using a regions-of-interest analysis, we obtained volumetric and diffusivity measures of the hippocampal head and body-tail-section as well as of the whole hippocampus. Detailed cognitive evaluation was based on the CERAD battery.All volumetric measures as well as diffusivity of the hippocampus head were significantly (p < 0.01) altered in patients as compared to controls. In patients, increased left head diffusivity significantly (p < 0.01) correlated with performance on free delayed verbal recall test (DVR) (r = −0.74, p = 0.0002) and with the CERAD global score. Reduced volume of the left body-tail was also associated with performance on DVR (r = 0.62, p = 0.004). Stepwise regression analyses revealed that increased left head diffusivity was the only predictor for performance on DVR (R2 = 52%, p < 0.0005).These findings suggest that anterior hippocampus diffusivity is more closely related to verbal episodic memory impairment than other regional or global structural measures. Our data support the hypothesis of functional differentiation in general and the specific role of the anterior hippocampus in episodic memory in particular. Diffusivity measurements might be highly sensitive to functionally relevant degenerative alterations of the hippocampus.  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