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   205311篇
  免费   2574篇
  国内免费   97篇
耳鼻咽喉   1553篇
儿科学   8609篇
妇产科学   3705篇
基础医学   19816篇
口腔科学   2107篇
临床医学   14111篇
内科学   36549篇
皮肤病学   1794篇
神经病学   17887篇
特种医学   9956篇
外科学   33638篇
综合类   3322篇
一般理论   12篇
预防医学   19464篇
眼科学   4186篇
药学   11964篇
中国医学   794篇
肿瘤学   18515篇
  2023年   217篇
  2022年   526篇
  2021年   1068篇
  2020年   596篇
  2019年   726篇
  2018年   22722篇
  2017年   17834篇
  2016年   20222篇
  2015年   1686篇
  2014年   2012篇
  2013年   2177篇
  2012年   8977篇
  2011年   22985篇
  2010年   19850篇
  2009年   12403篇
  2008年   20899篇
  2007年   23178篇
  2006年   1900篇
  2005年   3431篇
  2004年   4441篇
  2003年   5303篇
  2002年   3332篇
  2001年   1007篇
  2000年   1112篇
  1999年   775篇
  1998年   454篇
  1997年   398篇
  1996年   247篇
  1995年   247篇
  1994年   216篇
  1993年   199篇
  1992年   426篇
  1991年   502篇
  1990年   478篇
  1989年   447篇
  1988年   372篇
  1987年   334篇
  1986年   304篇
  1985年   327篇
  1984年   248篇
  1983年   210篇
  1980年   141篇
  1979年   252篇
  1978年   170篇
  1977年   161篇
  1976年   147篇
  1975年   171篇
  1974年   176篇
  1973年   179篇
  1972年   139篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.

Background  

Food behaviours, attitudes, environments and knowledge are relevant to professionals in childhood obesity prevention, as are dietary patterns which promote positive energy balance. There is a lack of valid and reliable tools to measure these parameters. The aim of this study was to determine the reliability and relative validity of a child nutrition questionnaire assessing all of these parameters, used in the evaluation of a community-based childhood obesity prevention project.  相似文献   
992.
Parkinson’s disease (PD) is a complex motor and non-motor disorder and management is often challenging. In this review, we explore emerging approaches to improve the care of patients, drawing from the literature regarding patient-centred care, patient and caregiver perspectives and priorities, gaps in knowledge among patients and caregivers and the need for accurate information, individual variability in disease manifestations, prognostication of disease course, new developments in health technologies and personalized medicine, specialty care, pharmacological and non-pharmacological management, financial burden, lifestyle and work-related issues, support groups and palliative care.  相似文献   
993.
We describe an additional case of spastic paretic hemifacial contracture, an uncommon condition characterized by sustained unilateral contraction of the facial muscles associated with mild ipsilateral facial paresis. This entity has only rarely been associated with multiple sclerosis (MS) and can be mistaken for hemifacial spasm. Early consideration of MS in the differential diagnosis of young patients admitted with these symptoms is essential.  相似文献   
994.
17β-Estradiol (E2) rapidly, by binding to membrane estrogen receptors, activates cell signaling cascades which induce formation of new dendritic spines in the hippocampus of males as in females, but the interaction with other metabolic processes, such as extracellular adenine nucleotides metabolism, are currently unknown. Extracellular adenine nucleotides play significant roles, controlling excitatory glutamatergic synapses and development of neural circuits and synaptic plasticity. Their precise regulation in the synaptic cleft is tightly controlled by ecto-nucleoside triphosphate diphosphohydrolase (NTPDase)/ecto-5′-nucleotidase (eN) enzyme chain. Therefore, we sought to clarify whether a single systemic injection of E2 in male rats is accompanied by changes in the expression of the pre- and postsynaptic proteins and downstream kinases linked to E2-induced synaptic rearrangement as well as alterations in NTPDase/eN pathway in the hippocampal synaptosomes. Obtained data showed activation of mammalian target of rapamycin and upregulation of key synaptic proteins necessary for spine formation, 24 h after systemic E2 administration. In E2-mediated conditions, we found downregulation of NTPDase1 and NTPDase2 and attenuation of adenine nucleotide hydrolysis by NTPDase/eN enzyme chain, without changes in NTPDase3 properties and augmentation of synaptic tissue-nonspecific alkaline phosphatase (TNAP) activity. Despite reduced NTPDase activities, increased TNAP activity probably prevents toxic accumulation of ATP in the extracellular milieu and also hydrolyzes accumulated ADP due to unchanged NTPDase3 activity. Thus, our initial evaluation supports idea of specific roles of different ectonucleotidases and their coordinated actions in E2-mediated spine remodeling and maintenance.  相似文献   
995.
Zhang Z  Liu S  Lin X  Teng G  Yu T  Fang F  Zang F 《Neuroradiology》2011,53(3):177-184

Introduction  

The purpose of this study is to show the condition of laminar organization on 3.0T and 7.0T postmortem magnetic resonance imaging (MRI) and analyze developmental changes.  相似文献   
996.
Objective Diabetes mellitus is an independent risk factor for acute myocardial infarction. Thus, a surveillance study was conducted as part of studies to create a national database related to electrocardiogram (ECG)-gated myocardial perfusion single-photon emission computed tomography (SPECT) of ischemic heart disease. Methods Single-photon emission computed tomography was conducted in patients with type 2 diabetes mellitus and their prognoses will be followed for 3 years, stratified by patients’ clinical background and SPECT findings. Results A total of 513 patients from 50 institutions were enrolled in this study, 297 of whom were men (age 66.2 ± 0.4 years, mean ± SEM) and 261 women (age 67.8 ± 0.5 years). They have a history of retinopathy (25.3%), neuropathy (19.9%), cerebrovascular disorder, chronic obstructive pulmonary disease, and photocoagulation. Major risk factors for present disease were hypertension (82.3%) and hyperlipidemia (79.7%). In 244 patients (129 men and 115 women), body mass index (BMI) was 25 or more. Fifty-two of them (10.1%) underwent coronary angiography; of these, 26 (50.0%) had no coronary artery lesions with 75% or more stenosis, and only 1 (1.9%) had a left main trunk with 50% or more stenosis. An overwhelming majority of patients (94.3%) underwent SPECT imaging by a 1-day stress-followed-by-rest procedure. Stress procedure was exercise in most (70.8%) patients, followed by dipyridamole infusion in 14.6%, adenosine infusion in 6.6%, and adenosine triphosphate infusion in 5.7%. Endpoint of stress examination was most often fatigue in lower limbs (40.7%), followed by completion of pharmacological stress protocol (28.7%), and achievement of target heart rate (26.3%). The largest number of patients (198, 38.6%) received 99mTc-tetrofosmin at an initial dosage of 200–300 MBq (mean 331 ± 3 MBq) followed by a second dosage of 700–800 MBq (mean 748 ± 8 MBq). Among them, 491 (95.7%) received some kind of therapeutic drug: hypoglycemic drugs were used by the largest number (83.2%), followed by hypotensive (66.7%), hypolipidemic (40.7%), and antiplatelet drugs (27.7%), vasodilators (5.5%), and antioxidants and others (2.3%). Conclusions This study was designed to clarify the correlation between coronary artery disease and diabetes mellitus as its risk factor based on the clinical and imaging findings. Patient enrollment was closed on September 30, 2005, and follow-up is now under way.  相似文献   
997.
Primary renal synovial sarcoma is a rarely seen renal neoplasm. An experienced uropathologist is needed to make the pathological diagnosis. A patient, operated on with a prediagnosis of renal cell carcinoma, the pathology of which was reported as synovial sarcoma, is presented in this article. 18F-fluoro-deoxyglucose positron emission tomography and computed tomography were performed preoperatively and in the postoperative follow-up to detect the primary tumor and lymph node metastases.  相似文献   
998.
Tenosynovial giant cell tumor and pigmented villonodular synovitis   总被引:2,自引:0,他引:2  
  相似文献   
999.
Kim HJ  Jun BY  Kim WH  Cho YK  Lim MK  Suh CH 《Skeletal radiology》2002,31(11):637-642
OBJECTIVE:. The alar ligament plays a critical role in limiting the axial rotation of the head, the left alar ligament being stretched on rotation to the right and vice versa. The purposes of this study were to assess the usefulness of MR imaging in demonstrating the alar ligament and also to identify its morphologic changes during axial rotation of the head in asymptomatic young volunteers. DESIGN AND PATIENTS:. Twenty-two healthy volunteers participated in this study. All subjects underwent four series of contiguous fast spin echo density-weighted MR images with a 2 mm slice thickness including axial and coronal images with the head in neutral position, and coronal images with alternate head rotation to the right and left. The alar ligaments seen on each series of MR images were visually graded 0-2, and grade comparisons were performed between the four series of MR images. We also assessed the morphologic changes of the alar ligament on coronal images during axial rotation of the head. RESULTS:. Grade comparisons for the demonstration of the alar ligament revealed that each of three series of coronal images was statistically significantly better in grade than axial images. During axial rotation of the head, MR images showed rather constant morphologic changes of the alar ligament: elevation and wrapping of the contralateral alar ligament around the dens, associated with slightly upward movement of C1-C2 on that side. This wrap-around effect of the contralateral alar ligament in relation to the dens sometimes caused the apparent shortening of the alar ligament on that side. CONCLUSION:. Reliable assessment of the anatomy and function of the alar ligament can be achieved with MR imaging, preferably in coronal planes. MR imaging with the aid of a functional study may be a valuable imaging modality in the evaluation of alar ligament failure.  相似文献   
1000.
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