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   178043篇
  免费   1262篇
  国内免费   44篇
耳鼻咽喉   1149篇
儿科学   6831篇
妇产科学   3042篇
基础医学   16817篇
口腔科学   1651篇
临床医学   12580篇
内科学   31295篇
皮肤病学   732篇
神经病学   16457篇
特种医学   9207篇
外科学   29402篇
综合类   2384篇
一般理论   3篇
预防医学   18233篇
眼科学   2792篇
药学   9612篇
中国医学   637篇
肿瘤学   16525篇
  2023年   45篇
  2022年   72篇
  2021年   172篇
  2020年   79篇
  2019年   103篇
  2018年   22023篇
  2017年   17459篇
  2016年   19622篇
  2015年   1001篇
  2014年   968篇
  2013年   975篇
  2012年   7124篇
  2011年   21122篇
  2010年   18912篇
  2009年   11632篇
  2008年   19578篇
  2007年   21797篇
  2006年   645篇
  2005年   2259篇
  2004年   3402篇
  2003年   4373篇
  2002年   2484篇
  2001年   289篇
  2000年   418篇
  1999年   194篇
  1998年   300篇
  1997年   285篇
  1996年   193篇
  1995年   164篇
  1994年   168篇
  1993年   99篇
  1992年   59篇
  1991年   110篇
  1990年   137篇
  1989年   109篇
  1988年   85篇
  1987年   68篇
  1986年   61篇
  1985年   62篇
  1984年   32篇
  1983年   34篇
  1982年   49篇
  1980年   61篇
  1976年   25篇
  1969年   23篇
  1938年   60篇
  1937年   25篇
  1934年   30篇
  1932年   56篇
  1930年   46篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
Synkopen     
Syncope occurs in approximately 25% of the population at least once during their lifetime. It therefore represents the most frequent differential diagnosis of an epileptic seizure. Depending on the prognosis and therapy, syncopes can be divided in cardiac syncope, syncope due to orthostatic hypotension and reflex syncope, of which vasovagal (neurocardiogenic) syncope is the most frequent type. Vasovagal syncope typically occurs after prolonged standing, the sight of blood, pain and medical procedures. The pathophysiology is not well understood. Genetic factors play a role as well, mainly following a complex mode of inheritance. Syncope can usually be differentiated from an epileptic seizure based on the medical history. Typical vasovagal triggers, a typical prodrome and pallor suggest syncope, whereas cyanosis, tongue biting and a prolonged postictal state favor an epileptic seizure. In cases of doubt or if cardiac syncope is suspected additional diagnostic tests may be necessary. Due to the increased mortality, patients with cardiac syncope need urgent cardiological treatment. The aim of the treatment of vasovagal syncope is to avoid additional events as this type is not associated with increased mortality. This can be achieved by behavioral changes, e.g. avoiding the trigger situation and lying down or tensing of arm and leg musculature during the prodrome to avoid further reduction of blood pressure. There is only sparse evidence for pharmacotherapeutic options. Cardiac pacemakers mostly have no effect. The implantation of a pacemaker seems to be beneficial only in patients over 40 years old with frequent vasovagal syncope, asystole and negative tilt table test.  相似文献   
992.
993.
Healthy food distribution programs that allow small retailers to purchase fresh fruits and vegetables at wholesale prices may increase the profitability of selling produce. While promising, little is known about how these programs affect the availability of fresh fruits and vegetables in underserved communities. This study examined the impacts of a healthy food distribution program in Los Angeles County over its first year of operation (August 2015–2016). Assessment methods included: (1) a brief survey examining the characteristics, purchasing habits, and attitudes of stores entering the program; (2) longitudinal tracking of sales data examining changes in the volume and variety of fruits and vegetables distributed through the program; and (3) the collection of comparison price data from wholesale market databases and local grocery stores. Seventeen stores participated in the program over the study period. One-fourth of survey respondents reported no recent experience selling produce. Analysis of sales data showed that, on average, the total volume of produce distributed through the program increased by six pounds per week over the study period (95% confidence limit: 4.50, 7.50); trends varied by store and produce type. Produce prices offered through the program approximated those at wholesale markets, and were lower than prices at full-service grocers. Results suggest that healthy food distribution programs may reduce certain supply-side barriers to offering fresh produce in small retail venues. While promising, more work is needed to understand the impacts of such programs on in-store environments and consumer behaviors.  相似文献   
994.
995.
Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic stem cell disorder with its protean clinical manifestations. This is due to partial or complete absence of ‘glycophosphatidyl-inositol-anchor proteins’ (GPI-AP). The main aim of this review is to highlight various diagnostic modalities available, basic principle of each test and recent advances in the diagnosis of PNH. Recently among various tests available, the flow cytometry has become ‘the gold standard’ for PNH testing. In order to overcome the difficulties encountered by the testing and research laboratories throughout the world, International Clinical Cytometry Society has come up with guidelines regarding the indications for testing, protocol for sample collection, processing, panel of antibodies as well as gating strategies to be used, how to interpret the test and reporting format to be used. It is essential to test at least two GPI-linked markers on at least two different lineages particularly on red cells and granulocytes/monocytes. The fluorescent aerolysin combined with other monoclonal antibodies in multicolour flow cytometry offered an improved assay not only for diagnosis but also for monitoring of PNH clones. It is equally important to diagnose this rare entity with high index of suspicion.  相似文献   
996.
Bubbles are an intrinsic problem in microfluidic devices and they can appear during the initial filling of the device or during operation. This report presents a generalizable technique to extract bubbles from microfluidic networks using an adjacent microfluidic negative pressure network over the entire microfluidic channel network design. We implement this technique by superimposing a network of parallel microchannels with a vacuum microfluidic channel and characterize the bubble extraction rates as a function of negative pressure applied. In addition, we generate negative pressure via a converging-diverging (CD) nozzle, which only requires inlet gas pressure to operate. Air bubbles generated during the initial liquid filling of the microfluidic network are removed within seconds and their volume extraction rate is calculated. This miniaturized vacuum source can achieve a vacuum pressure of 7.23 psi which corresponds to a bubble extraction rate of 9.84 pL/s, in the microfluidic channels we characterized. Finally, as proof of concept it is shown that the bubble removal system enables bubble removal on difficult to fill microfluidic channels such as circular or triangular shaped channels. This method can be easily integrated into many microfluidic experimental protocols.  相似文献   
997.
998.
Based on theoretical considerations and case reports, possibilities of scenic work with the life line are presented. It is obvious how clients, already in the initial phase of their therapy, are supported in perceiving themselves as “actors on the stages of their lives”. The scenic experiencing of longitudinal and cross sections on the life line enables clients to create a “subjective theory of disease”. Treatment goals become apparent and can be communicated with respect to a treatment planning. When the addiction can be experienced as history and clients can recognize meaningful correlations on their life lines, motivation and at the same time expectation of self-efficacy for the next steps on their paths through life arises. In psychodramatic work with life lines, anamnesis and diagnostics are closely related to the supporting of the experience of identity, appreciation and meaningfulness.  相似文献   
999.
1000.
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