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   3339篇
  免费   314篇
  国内免费   7篇
耳鼻咽喉   8篇
儿科学   180篇
妇产科学   62篇
基础医学   423篇
口腔科学   33篇
临床医学   334篇
内科学   630篇
皮肤病学   19篇
神经病学   272篇
特种医学   124篇
外科学   474篇
综合类   115篇
一般理论   1篇
预防医学   467篇
眼科学   62篇
药学   294篇
中国医学   3篇
肿瘤学   159篇
  2021年   56篇
  2020年   36篇
  2019年   48篇
  2018年   56篇
  2017年   57篇
  2016年   48篇
  2015年   51篇
  2014年   89篇
  2013年   109篇
  2012年   159篇
  2011年   164篇
  2010年   91篇
  2009年   79篇
  2008年   145篇
  2007年   129篇
  2006年   168篇
  2005年   138篇
  2004年   133篇
  2003年   130篇
  2002年   107篇
  2001年   119篇
  2000年   83篇
  1999年   68篇
  1998年   33篇
  1997年   23篇
  1996年   23篇
  1995年   25篇
  1994年   23篇
  1992年   52篇
  1991年   60篇
  1990年   61篇
  1989年   55篇
  1988年   64篇
  1987年   70篇
  1986年   61篇
  1985年   68篇
  1984年   59篇
  1983年   33篇
  1982年   30篇
  1979年   53篇
  1978年   39篇
  1977年   28篇
  1976年   29篇
  1975年   41篇
  1974年   44篇
  1973年   35篇
  1972年   50篇
  1971年   24篇
  1969年   30篇
  1967年   24篇
排序方式: 共有3660条查询结果,搜索用时 31 毫秒
71.
Microcrystalline cellulose (MCC) and cross-linked polyvinylpyrrolidone (PVP-CL) were examined as polymeric carriers to support amorphous ibuprofen (IB). Drug/carrier systems were prepared as physical mixes, and drug was loaded onto the polymers by hot mix and solvent deposition methods. The systems were examined using differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD) and by dissolution testing. PVP-CL reduced drug crystallinity more than MCC and, surprisingly, even very simple mixing of ibuprofen with PVP-CL induced disordering of the drug. Increased ibuprofen dissolution rates were achieved with both polymers, in the order of solvent deposition>hot mixes>physical mixes. The increased dissolution rates could be attributed to a combination of faster dissolution from amorphous ibuprofen, microcrystalline drug deposition on carrier surfaces and polymer swelling. However, no clear relationship was observed between ibuprofen dissolution rates (using first order, Higuchi or Hixson-Crowell relationships) and drug crystallinity.  相似文献   
72.
BACKGROUND: Controversy persists about whether chemotherapy benefits all breast cancer patients. PATIENTS AND METHODS: In the International Breast Cancer Study Group (IBCSG) trial VII, 1212 postmenopausal patients with node-positive disease were randomized to receive tamoxifen for 5 years or tamoxifen plus three concurrent courses of cyclophosphamide, methotrexate and 5-fluorouracil ('classical' CMF) chemotherapy, either early, delayed or both. In IBCSG trial IX, 1669 postmenopausal patients with node-negative disease were randomized to receive either tamoxifen alone or three courses of adjuvant classical CMF prior to tamoxifen. Results were assessed according to estrogen receptor (ER) content of the primary tumor. RESULTS: For patients with node-positive, ER-positive disease, adding CMF either early, delayed or both reduced the risk of relapse by 21% (P=0.06), 26% (P=0.02) and 25% (P=0.02), respectively, compared with tamoxifen alone. There was no difference in disease-free survival when CMF was given prior to tamoxifen in patients with node-negative, ER-positive tumors. CONCLUSIONS: CMF given concurrently (early, delayed or both) with tamoxifen was more effective than tamoxifen alone for patients with node-positive, endocrine-responsive breast cancer, supporting late administration of chemotherapy even after commencement of tamoxifen. In contrast, sequential CMF and tamoxifen for patients with node-negative, endocrine-responsive disease was ineffective.  相似文献   
73.
74.
Fetal growth is dependent on appropriate growth and function of the placenta. This is modulated by a variety of factors, including maternal growth factors that exert their actions by binding to specific receptors on trophoblast to promote activation of signaling events. Kinases and phosphatases within trophoblast act in concert to regulate growth factor actions and recent studies have begun to elucidate a role for microRNAs (miRs) in regulating the levels of these proteins in the placenta. This review will discuss growth factor signaling in the placenta and describe the emerging role of miRs in regulating placental development.  相似文献   
75.
Mimicry involves unconsciously copying the actions of others. Increasing evidence suggests that autistic people can copy the goal of an observed action but show differences in their mimicry. We investigated mimicry in autism spectrum disorder (ASD) within a two-dimensional virtual reality environment. Participants played an imitation game with a socially engaged avatar and socially disengaged avatar. Despite being told only to copy the goal of the observed action, autistic participants and matched neurotypical participants mimicked the kinematics of the avatars’ movements. However, autistic participants mimicked less. Social engagement did not modulate mimicry in either group. The results demonstrate the feasibility of using virtual reality to induce mimicry and suggest mimicry differences in ASD may also occur when interacting with avatars.  相似文献   
76.
77.
Criminal investigators dealing with skeletal remains have the primary concern for determining whether the remains are of anthropological or archaeological interest. If the remains are determined to be from an anthropological era, the next concern becomes the determination of time since death (TSD). Despite advances in modern technology, TSD remains a most elusive determinant. It has critical value for providing police with a time frame in which the person may have gone missing, increasing the likelihood of a positive identification. This article outlines a novel approach to dating skeletal remains in an Australian context, but with global connotations.  相似文献   
78.
A dynamic assessment approach was used to examine the source of poor performance on the Rey–Osterrieth Complex Figure Test (ROCF) among 202 school-age children referred for learning difficulties. The ROCF was administered in the standard format and then in a structured format that highlighted the designs organizational framework. Manipulating encoding in this way improved recall to at least age-level for the majority of children. Those children who did not benefit from the structured format had relatively poor visual organizational skills. For most children with learning problems, poor ROCF performance stems from metacognitive difficulties; for a minority, the source appears to be more perceptual. A dynamic assessment procedure can enhance the diagnostic utility of the ROCF for children.  相似文献   
79.
80.
International recommendations encourage liberal administration of oxygen to patients having surgery under general anaesthesia, ostensibly to reduce surgical site infection. However, the optimal oxygen regimen to minimise postoperative complications and enhance recovery from surgery remains uncertain. The hospital operating theatre randomised oxygen (HOT-ROX) trial is a multicentre, patient- and assessor-blinded, parallel-group, randomised clinical trial designed to assess the effect of a restricted, standard care, or liberal peri-operative oxygen therapy regimen on days alive and at home after surgery in adults undergoing prolonged non-cardiac surgery under general anaesthesia. Here, we report the findings of the internal vanguard feasibility phase of the trial undertaken in four large metropolitan hospitals in Australia and New Zealand that included the first 210 patients of a planned overall 2640 trial sample, with eight pre-specified endpoints evaluating protocol implementation and safety. We screened a total of 956 participants between 1 September 2019 and 26 January 2021, with data from 210 participants included in the analysis. Median (IQR [range]) time-weighted average intra-operative FiO2 was 0.30 (0.26–0.35 [0.20–0.59]) and 0.47 (0.44–0.51 [0.37–0.68]) for restricted and standard care, respectively (mean difference (95%CI) 0.17 (0.14–0.20), p < 0.001). Median time-weighted average intra-operative FiO2 was 0.83 (0.80–0.85 [0.70–0.91]) for liberal oxygen therapy (mean difference (95%CI) compared with standard care 0.36 (0.33–0.39), p < 0.001). All feasibility endpoints were met. There were no significant patient adverse events. These data support the feasibility of proceeding with the HOT-ROX trial without major protocol modifications.  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