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   5075篇
  免费   441篇
  国内免费   10篇
耳鼻咽喉   53篇
儿科学   143篇
妇产科学   116篇
基础医学   733篇
口腔科学   108篇
临床医学   671篇
内科学   1085篇
皮肤病学   141篇
神经病学   407篇
特种医学   190篇
外科学   680篇
综合类   77篇
一般理论   4篇
预防医学   473篇
眼科学   45篇
药学   272篇
中国医学   6篇
肿瘤学   322篇
  2021年   77篇
  2020年   68篇
  2019年   102篇
  2018年   101篇
  2017年   92篇
  2016年   89篇
  2015年   102篇
  2014年   150篇
  2013年   225篇
  2012年   288篇
  2011年   342篇
  2010年   184篇
  2009年   174篇
  2008年   240篇
  2007年   253篇
  2006年   215篇
  2005年   238篇
  2004年   198篇
  2003年   217篇
  2002年   152篇
  2001年   159篇
  2000年   139篇
  1999年   132篇
  1998年   52篇
  1997年   40篇
  1996年   42篇
  1995年   43篇
  1994年   34篇
  1993年   37篇
  1992年   92篇
  1991年   92篇
  1990年   84篇
  1989年   83篇
  1988年   79篇
  1987年   57篇
  1986年   96篇
  1985年   71篇
  1984年   50篇
  1983年   58篇
  1982年   30篇
  1981年   31篇
  1980年   25篇
  1979年   41篇
  1978年   33篇
  1976年   32篇
  1975年   24篇
  1974年   39篇
  1972年   26篇
  1969年   27篇
  1968年   26篇
排序方式: 共有5526条查询结果,搜索用时 46 毫秒
1.
2.
Steady-state axisymmetric simulations using the Reynolds-Averaged Navier-Stokes equations have been carried out in order to optimize the performance of a Chemical, Biological, Radiological, and Nuclear (CBRN) canister filter for its use in a powered air-purifying respirator (PAPR). Alterations have been made to the shape of the canister, the spacing of the rear wall of the canister with regard to the carbon filter, and the bracketing between (i) the particulate filter and the carbon bed and (ii) the carbon bed and the canister wall. The pressure drops across the canister and the residence time distribution at the rear of the carbon bed have been analyzed in detail based on an extensive parametric analysis involving the aforementioned variations. It has been demonstrated that the non-uniform porosity profile of the carbon bed resulted in alternating regions of high and low velocity close to the canister wall, providing a possible route for breakthrough. Designs, which included a bracket at the rear of the carbon bed, blocked this route and consequently had a longer minimum mean residence time than those, which did not. It has also been shown that the spacing between the carbon bed and the canister rear wall had a large impact on both residence time and pressure drop. In cases where the carbon backed directly onto the canister rear wall flow in the axial direction from the outside wall toward the canister axis resulted in far greater pressure drop and a reduction in minimum mean residence time within the carbon bed.  相似文献   
3.
4.
5.
6.
7.
Information about the prevalence of malarial anemia in areas of low-malaria transmission intensity, like Latin America, is scarce. To characterize the malaria-related anemia, we evaluated 929 malaria patients from three sites in Colombia during 2011–2013. Plasmodium vivax was found to be the most prevalent species in Tierralta (92%), whereas P. falciparum was predominant in Tumaco (84%) and Quibdó (70%). Although severe anemia (hemoglobin < 7 g/dL) was almost absent (0.3%), variable degrees of non-severe anemia were observed in 36.9% of patients. In Tierralta, hemoglobin levels were negatively associated with days of illness. Moreover, in Tierralta and Quibdó, the number of previous malaria episodes and hemoglobin levels were positively associated. Both Plasmodium species seem to have similar potential to induce malarial anemia with distinct cofactors at each endemic setting. The target age in these low-transmission settings seems shifting toward adolescents and young adults. In addition, previous malaria experience seems to induce protection against anemia development. Altogether, these data suggest that early diagnosis and prompt treatment are likely preventing more frequent and serious malaria-related anemia in Colombia.  相似文献   
8.
Introduction: The massive implementation of combination antiretroviral therapy (cART) has forever changed the landscape of HIV infection. This unprecedented success has turned HIV infection into a manageable chronic disease. The increased survival of people living with HIV is, however, shadowed by a high burden of aging-related comorbidities. The pathogenic basis underlying this excess of co-morbid conditions is most likely a persistent inflammatory and immune activation state, despite an optimal control of HIV replication, which in turn has largely been attributed to bacterial or bacterial products translocation from the gut.

Area covered: This review is focused on the relationship between cART and the chronic inflammatory and immune activation status in otherwise virologically well-controlled people living with HIV (PLWH). Particular focus will be placed on the differences, if any, between distinct cART modalities, with emphasis on less-drug cART regimens, and especially on dual therapies.

Expert opinion: Research to address the increased inflammatory and immune activation status of cART-treated, HIV-infected patients, should focus on adjuvant means of therapy, rather than on the cART regime itself. With current antiretrovirals, no difference between dual and triple regimens has been demonstrated, provided that virological and immunological outcomes be non-inferior.  相似文献   

9.
In pancreas transplantation, complications can arise at each step of the process, from the initial selection of donors and recipients through the surgical technique itself and the post-operative period, when lifelong immunosuppression is required. In the early steps, careful retrieval and preservation of the pancreas are crucial for the viability of the organ and ultimate success of the transplant. The pancreas is a low-flow gland, making it highly sensitive to transplantation conditions and presenting risk of pancreatitis due to periods of ischemia. The two groups of donors - after brain death (DBD) or after cardiac arrest (DCD) - require different strategies of retrieval and preservation to avoid or reduce the risk of complications developing during and after the transplantation. For DBD donor transplantation, multiorgan retrieval and cold preservation is the conventional technique. Asystole donor (DCD) transplantation, in contrast, can benefit from the newest technologies, such as hypothermic and especially normothermic preservation machines (referred to as NECMO), to optimize organ preservation. The latter has led to an increase in the pool of donors by facilitating recuperation of organs for transplantation that would have been discarded otherwise.  相似文献   
10.
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