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   2343816篇
  免费   183347篇
  国内免费   4362篇
耳鼻咽喉   32608篇
儿科学   76879篇
妇产科学   65914篇
基础医学   332808篇
口腔科学   67503篇
临床医学   205548篇
内科学   460912篇
皮肤病学   49968篇
神经病学   191641篇
特种医学   94029篇
外国民族医学   772篇
外科学   359338篇
综合类   55355篇
现状与发展   3篇
一般理论   826篇
预防医学   179379篇
眼科学   53882篇
药学   173844篇
  2篇
中国医学   4371篇
肿瘤学   125943篇
  2018年   23492篇
  2016年   20412篇
  2015年   23513篇
  2014年   32587篇
  2013年   49571篇
  2012年   67454篇
  2011年   70952篇
  2010年   42241篇
  2009年   40361篇
  2008年   67552篇
  2007年   71654篇
  2006年   72215篇
  2005年   70333篇
  2004年   68652篇
  2003年   65524篇
  2002年   64377篇
  2001年   105322篇
  2000年   108790篇
  1999年   92599篇
  1998年   26142篇
  1997年   23761篇
  1996年   23435篇
  1995年   22638篇
  1994年   21252篇
  1993年   20125篇
  1992年   75474篇
  1991年   73060篇
  1990年   71393篇
  1989年   69148篇
  1988年   64219篇
  1987年   63325篇
  1986年   60505篇
  1985年   58220篇
  1984年   43741篇
  1983年   37443篇
  1982年   22360篇
  1981年   19812篇
  1980年   18687篇
  1979年   41177篇
  1978年   28782篇
  1977年   24239篇
  1976年   22846篇
  1975年   24522篇
  1974年   29758篇
  1973年   28620篇
  1972年   26471篇
  1971年   24752篇
  1970年   23117篇
  1969年   21683篇
  1968年   20120篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
21.
In this paper we present a coupled Finite Element Method – Boundary Element Method (FEM-BEM) approach for the solution of the free-boundary axi-symmetric plasma equilibrium problem. The proposed method, obtained from an improvement of the Hagenow-Lackner coupling method, allows to efficiently model the equilibrium problem in unbounded domains by discretizing only the plasma region; the external conductors can be modelled either as 2D or 3D models, according to the problem of interest. The paper explores different iterative methods for the solution of the nonlinear Grad-Shafranov equation, such as Picard, Newton-Raphson and Newton-Krylov, in order to provide a robust and reliable tool, able to handle large-scale problems (e.g. high resolution equilibria). This method has been implemented in the FRIDA code (FRee-boundary Integro-Differential Axisimmetric – https://github. om/matteobonotto/ FRIDA), together with a suitable Adaptive Integration Technique (AIT) for the computation of the source term. FRIDA has been successfully tested and validated against experimental data from RFX-mod device, and numerical equilibria of an ITER-like device.  相似文献   
22.
23.
24.
25.
26.
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   
27.
28.
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   
29.
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   

30.
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