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   2572987篇
  免费   212929篇
  国内免费   7677篇
耳鼻咽喉   34510篇
儿科学   84839篇
妇产科学   72161篇
基础医学   360254篇
口腔科学   74573篇
临床医学   230894篇
内科学   512000篇
皮肤病学   58510篇
神经病学   211242篇
特种医学   104290篇
外国民族医学   720篇
外科学   395795篇
综合类   63484篇
现状与发展   5篇
一般理论   911篇
预防医学   205017篇
眼科学   57315篇
药学   187814篇
  7篇
中国医学   4587篇
肿瘤学   134665篇
  2018年   25043篇
  2016年   22787篇
  2015年   26008篇
  2014年   36144篇
  2013年   54747篇
  2012年   70215篇
  2011年   74746篇
  2010年   45553篇
  2009年   43921篇
  2008年   70804篇
  2007年   75113篇
  2006年   76629篇
  2005年   74293篇
  2004年   72170篇
  2003年   69670篇
  2002年   67156篇
  2001年   120173篇
  2000年   123861篇
  1999年   104337篇
  1998年   30391篇
  1997年   27464篇
  1996年   28107篇
  1995年   27828篇
  1994年   26145篇
  1993年   24570篇
  1992年   86968篇
  1991年   84741篇
  1990年   82061篇
  1989年   78972篇
  1988年   73464篇
  1987年   72347篇
  1986年   68524篇
  1985年   66255篇
  1984年   50217篇
  1983年   42795篇
  1982年   26054篇
  1981年   23415篇
  1980年   22069篇
  1979年   46896篇
  1978年   33313篇
  1977年   28187篇
  1976年   26227篇
  1975年   27651篇
  1974年   33304篇
  1973年   32013篇
  1972年   29480篇
  1971年   27570篇
  1970年   25292篇
  1969年   23745篇
  1968年   21837篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
22.
23.
24.
25.
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   
26.
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   
27.
28.
29.
Maternal and Child Health Journal - Early life exposures can have an impact on a child’s developmental trajectory and children born late preterm (34–36&nbsp;weeks gestational age)...  相似文献   
30.
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   
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