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   2317194篇
  免费   181539篇
  国内免费   3671篇
耳鼻咽喉   32037篇
儿科学   71648篇
妇产科学   64171篇
基础医学   329751篇
口腔科学   70113篇
临床医学   203849篇
内科学   451562篇
皮肤病学   49302篇
神经病学   185039篇
特种医学   92349篇
外国民族医学   541篇
外科学   360740篇
综合类   53804篇
现状与发展   3篇
一般理论   759篇
预防医学   171429篇
眼科学   53490篇
药学   177373篇
  5篇
中国医学   4705篇
肿瘤学   129734篇
  2018年   21572篇
  2016年   18788篇
  2015年   21690篇
  2014年   29847篇
  2013年   44997篇
  2012年   61143篇
  2011年   64310篇
  2010年   37979篇
  2009年   36376篇
  2008年   62008篇
  2007年   65375篇
  2006年   66605篇
  2005年   64660篇
  2004年   63342篇
  2003年   60663篇
  2002年   59478篇
  2001年   115843篇
  2000年   120074篇
  1999年   101350篇
  1998年   26097篇
  1997年   23566篇
  1996年   23545篇
  1995年   22657篇
  1994年   21149篇
  1993年   19823篇
  1992年   81849篇
  1991年   79180篇
  1990年   77127篇
  1989年   74852篇
  1988年   69072篇
  1987年   67879篇
  1986年   64179篇
  1985年   62019篇
  1984年   45516篇
  1983年   39072篇
  1982年   22092篇
  1981年   19617篇
  1980年   18264篇
  1979年   42590篇
  1978年   29172篇
  1977年   24824篇
  1976年   22795篇
  1975年   24472篇
  1974年   29770篇
  1973年   28543篇
  1972年   26507篇
  1971年   24972篇
  1970年   23292篇
  1969年   21877篇
  1968年   19935篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
11.
12.
13.
14.
Comprehensive evidence regarding the treatment of non-anaemic iron deficiency in patients undergoing valvular heart surgery is lacking. This study aimed to investigate the association between non-anaemic iron deficiency and postoperative outcomes in these patients. We retrospectively analysed 321 patients of which 180 (56%) had iron deficiency (defined as serum ferritin < 100 ng.ml-1 or < 300 ng.ml-1 with transferrin saturation < 20%). While the iron-deficient group had lower pre-operative haemoglobin levels than the non-iron deficient group (median (IQR [range]) 134 (127–141 [120–172]) g.l-1, 143 (133–150 [120–179]) g.l-1, p = 0.001), there was no between-group difference in allogeneic red blood cell transfusion. Median (IQR [range]) days alive and out of hospital at postoperative day 90 was 1 day shorter in the iron-deficient group (80 (77–82 [9–85]) days vs. 81 (79–83 [0–85]) days, p = 0.026). In multivariable analysis, only cardiopulmonary bypass duration (p = 0.032) and intra-operative allogeneic red blood cell transfusion (p = 0.011) were significantly associated with reduced days alive and out of hospital at postoperative day 90. Iron deficiency did not exert any adverse influence on secondary outcomes except length of hospital stay. Our findings indicate that non-anaemic iron deficiency alone is not associated with adverse effects in patients undergoing valvular heart surgery when it does not translate into an increased risk of allogeneic transfusion.  相似文献   
15.
16.
Cyclotron-produced copper-64 radioisotope tracers offer the possibility to perform both diagnostic investigation by positron emission tomography (PET) and radiotherapy by a theranostic approach with bifunctional chelators. The versatile chemical properties of copper add to the importance of this isotope in medicinal investigation. [64Cu][Cu (ATSM)] has shown to be a viable candidate for imaging of tumor hypoxia; a critical tumor microenvironment characteristic that typically signifies tumor progression and resistance to chemo-radiotherapy. Various production and radiosynthesis methods of [64Cu][Cu (ATSM)] exist in labs, but usually involved non-standardized equipment with varying production qualities and may not be easily implemented in wider hospital settings. [64Cu][Cu (ATSM)] was synthesized on a modified GE TRACERlab FXN automated synthesis module. End-of-synthesis (EOS) molar activity of [64Cu][Cu (ATSM)] was 2.2–5.5 Ci/μmol (HPLC), 2.2–2.6 Ci/μmol (ATSM-titration), and 3.0–4.4 Ci/μmol (ICP-MS). Radiochemical purity was determined to be >99% based on radio-HPLC. The final product maintained radiochemical purity after 20 h. We demonstrated a simple and feasible process development and quality control protocols for automated cyclotron production and synthesis of [64Cu][Cu (ATSM)] based on commercially distributed standardized synthesis modules suitable for PET imaging and theranostic studies.  相似文献   
17.
18.
Gold nanoparticles (Au NPs) hold great promise in food, industrial and biomedical applications due to their unique physicochemical properties. However, influences of the gastrointestinal tract (GIT), a likely route for Au NPs administration, on the physicochemical properties of Au NPs has been rarely evaluated. Here, we investigated the influence of GIT fluids on the physicochemical properties of Au NPs (5, 50, and 100?nm) and their implications on intestinal epithelial permeability in vitro. Au NPs aggregated in fasted gastric fluids and generated hydroxyl radicals in the presence of H2O2. Cell studies showed that GIT fluids incubation of Au NPs affected the cellular uptake of Au NPs but did not induce cytotoxicity or disturb the intestinal epithelial permeability.  相似文献   
19.
Introduction: Percutaneous renal mass biopsy has evolved over the last decade with improvements on previous pitfalls including low tissue yield, high non-diagnostic rates, and complications. As understanding of tumor biology and natural history of renal cortical neoplasms has improved, percutaneous renal mass biopsy is poised to have an expanding role in an area characterized by individualized management and refined risk stratification.

Areas covered: This review summarizes the evolution of renal mass biopsy to its current state with respect to outcomes, indications, and clinical guidelines.

Expert opinion: With improved understanding of differential biological potential of renal cortical neoplasms combined with technical improvements in diagnostic yield and accuracy, utilization of renal mass biopsy is becoming an important adjunct to patient care in a broad range of clinical scenarios, including active surveillance, thermal ablation, and use of primary systemic therapy in localized and advanced settings.  相似文献   

20.
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