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   25350篇
  免费   1879篇
  国内免费   48篇
耳鼻咽喉   168篇
儿科学   1035篇
妇产科学   859篇
基础医学   2920篇
口腔科学   312篇
临床医学   4153篇
内科学   4757篇
皮肤病学   443篇
神经病学   2375篇
特种医学   384篇
外科学   2040篇
综合类   347篇
一般理论   28篇
预防医学   3744篇
眼科学   365篇
药学   1569篇
中国医学   34篇
肿瘤学   1744篇
  2023年   176篇
  2022年   227篇
  2021年   403篇
  2020年   347篇
  2019年   554篇
  2018年   634篇
  2017年   513篇
  2016年   552篇
  2015年   614篇
  2014年   838篇
  2013年   1333篇
  2012年   1967篇
  2011年   1931篇
  2010年   1087篇
  2009年   1026篇
  2008年   1656篇
  2007年   1821篇
  2006年   1701篇
  2005年   1754篇
  2004年   1665篇
  2003年   1505篇
  2002年   1460篇
  2001年   229篇
  2000年   180篇
  1999年   205篇
  1998年   296篇
  1997年   218篇
  1996年   195篇
  1995年   203篇
  1994年   173篇
  1993年   151篇
  1992年   116篇
  1991年   98篇
  1990年   119篇
  1989年   101篇
  1988年   78篇
  1987年   73篇
  1986年   74篇
  1985年   92篇
  1984年   99篇
  1983年   73篇
  1982年   95篇
  1981年   77篇
  1980年   71篇
  1979年   54篇
  1978年   55篇
  1977年   41篇
  1975年   35篇
  1973年   24篇
  1972年   31篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A preliminary study measured the contrast sensitivity function (CSF) in 30 children (aged 3 months-5 years). Preferential looking techniques were used to assess CSF to sine wave gratings displayed on one of two screens. To find a meaningful contrast sensitivity procedure we compared the results with a shorter procedure using an edge stimulus. The following problems were encountered: measuring the contrasts required to detect four or five different spatial frequencies took time, resulting in boredom and loss of attention in our subjects; there was poor correlation between CSF and edge detection; an interesting artefact resulted in a plateau rather than a low frequency fall-off in the CSF of five of the children greater than 30 months old. This artefact may have resulted from peripheral rather than central retinal responses and/or motion artefacts in the stimulus onset. A follow up study with 41 additional children aged 3-36 months limited the contrast testing to that of the spatial frequency corresponding to the peak of the CSF. The shortened procedure, plus a lot of encouragement, resulted in higher contrast sensitivities in all but the oldest age group and successful monocular contrast measurements. In order to avoid artefacts arising from peripheral vision, children were encouraged to look at each screen before responding.  相似文献   
92.
93.
94.
95.
PURPOSE: To explore potential indicators of the quality of end-of-life services for cancer patients that could be monitored using existing administrative data. METHODS: Quality indicators were identified and assessed by literature review for proposed indicators, focus groups with cancer patients and family members to assess candidate indicators and generate new ideas, and an expert panel ranking the meaningfulness and importance of each potential indicator using a modified Delphi approach. RESULTS: There were three major concepts of poor quality of end-of-life cancer care that could be examined using currently-available administrative data (such as Medicare claims): institution of new anticancer therapies or continuation of ongoing treatments very near death; a high number of emergency room visits, inpatient hospital admissions, or intensive care unit days near the end of life; and a high proportion of patients never enrolled in hospice, only admitted in the last few days of life, or dying in an acute-care setting. Concepts such as access to psychosocial and other multidisciplinary services and pain and symptom control are important and may eventually be feasible, but they cannot currently be applied in most data systems. Indicators based on limiting the use of treatments with low probability of benefit or indicators based on economic efficiency were not acceptable to patients, family members, or physicians. CONCLUSION: Several promising claims-based quality indicators were identified that, if found to be valid and reliable within data systems, could be useful in identifying health-care systems in need of improving end-of-life services.  相似文献   
96.
97.
98.
BACKGROUND: Formation of long-term memories is critically dependent on extracellular-regulated kinase (ERK) signaling. Activation of the ERK pathway by the sequential recruitment of mitogen-activated protein kinases is well understood. In contrast, the proteins that inactivate this pathway are not as well characterized. METHODS: Here we tested the hypothesis that the brain-specific striatal-enriched protein tyrosine phosphatase (STEP) plays a key role in neuroplasticity and fear memory formation by its ability to regulate ERK1/2 activation. RESULTS: STEP co-localizes with the ERKs within neurons of the lateral amygdala. A substrate-trapping STEP protein binds to the ERKs and prevents their nuclear translocation after glutamate stimulation in primary cell cultures. Administration of TAT-STEP into the lateral amygdala (LA) disrupts long-term potentiation (LTP) and selectively disrupts fear memory consolidation. Fear conditioning induces a biphasic activation of ERK1/2 in the LA with an initial activation within 5 minutes of training, a return to baseline levels by 15 minutes, and an increase again at 1 hour. In addition, fear conditioning results in the de novo translation of STEP. Inhibitors of ERK1/2 activation or of protein translation block the synthesis of STEP within the LA after fear conditioning. CONCLUSIONS: Together, these data imply a role for STEP in experience-dependent plasticity and suggest that STEP modulates the activation of ERK1/2 during amygdala-dependent memory formation. The regulation of emotional memory by modulating STEP activity may represent a target for the treatment of psychiatric disorders such as posttraumatic stress disorder (PTSD), panic, and anxiety disorders.  相似文献   
99.
Although anxiety is a well-established obstacle to the delivery of effective health care, there have been no attempts to measure it in the optometric consulting room. In this paper, we introduce physiological and psychological techniques that may be used to evaluate anxiety and arousal in the consulting room and present data from a small group of patients attending for a routine eye examination. Specifically, arousal was assessed before, during, and after the examination by measuring skin conductance in five patients. Anxiety was evaluated using the State-Trait Anxiety Inventory. Our data confirm the ability of these techniques to quantify arousal and anxiety in the optometric consulting room and reveal a previously unknown but important facet of the eye examination. We conclude that these techniques are suitable for use in further experimental work and may be used to identify factors capable of reducing anxiety in the optometric consulting room.  相似文献   
100.
OBJECTIVES: To critically review and integrate, from a developmental perspective, recent magnetic resonance imaging (MRI) studies of 4 childhood psychiatric disorders: schizophrenia, bipolar disorder (BD), attention-deficit hyperactivity disorder (ADHD), and major depressive disorder (MDD). METHOD: We reviewed published reports in refereed journals. We briefly describe the major findings with respect to the brain morphometry, chemistry, and function of children with psychiatric disorders and synthesize the reports in a summary to update clinicians. RESULTS: Some cortical grey matter abnormalities associated with schizophrenia appear to predate the onset of frank psychosis and continue to advance after the onset of psychosis, at least in more severe cases. Pediatric BD is associated with abnormalities in a circuit, thought to be involved in mood regulation, that encompasses the amygdala, striatum, and ventral PFC. Frontostriatal abnormalities are reported consistently in ADHD, potentially reflecting abnormalities in the development of cognitive control. Children with MDD show prefrontal cortical alterations that may differ in familial and nonfamilial subtypes of MDD. CONCLUSIONS: Results from neuroimaging studies of childhood psychopathology reveal abnormalities in the developmental trajectories observed in healthy children. Although MRI has increased our understanding of the pathophysiology of these disorders, routine neuroimaging for children with severe emotional disturbances is not indicated for diagnostic purposes.  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