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   3719232篇
  免费   312705篇
  国内免费   14496篇
耳鼻咽喉   50629篇
儿科学   118656篇
妇产科学   97617篇
基础医学   581075篇
口腔科学   102255篇
临床医学   335873篇
内科学   659786篇
皮肤病学   98462篇
神经病学   311813篇
特种医学   146767篇
外国民族医学   262篇
外科学   578680篇
综合类   113554篇
现状与发展   23篇
一般理论   2354篇
预防医学   303513篇
眼科学   88524篇
药学   259835篇
  21篇
中国医学   11028篇
肿瘤学   185706篇
  2021年   50171篇
  2020年   35502篇
  2019年   58641篇
  2018年   72879篇
  2017年   55295篇
  2016年   61195篇
  2015年   74927篇
  2014年   109236篇
  2013年   174716篇
  2012年   104785篇
  2011年   106665篇
  2010年   120969篇
  2009年   123878篇
  2008年   93229篇
  2007年   97803篇
  2006年   107322篇
  2005年   102113篇
  2004年   103805篇
  2003年   93550篇
  2002年   82587篇
  2001年   135673篇
  2000年   128823篇
  1999年   119866篇
  1998年   62905篇
  1997年   59505篇
  1996年   57139篇
  1995年   58034篇
  1994年   52133篇
  1993年   48494篇
  1992年   84898篇
  1991年   81109篇
  1990年   76723篇
  1989年   75134篇
  1988年   68929篇
  1987年   67173篇
  1986年   63501篇
  1985年   62738篇
  1984年   54638篇
  1983年   49239篇
  1982年   43196篇
  1981年   40562篇
  1980年   38007篇
  1979年   44555篇
  1978年   37949篇
  1977年   34520篇
  1976年   31615篇
  1975年   30505篇
  1974年   32294篇
  1973年   31025篇
  1972年   28981篇
排序方式: 共有10000条查询结果,搜索用时 233 毫秒
991.
992.
993.
994.
995.

Background

Pump speed optimization in patients implanted with a ventricular assist device represents a major challenge during the follow-up period. We present our findings on whether combined invasive hemodynamic ramp tests and cardiopulmonary exercise testing (CPX) can help optimize patient management.

Methods

Eighteen patients implanted with a HeartMate 3 (HM3) device underwent ramp tests with right heart catheterization (including central venous pressure [CVP], pulmonary artery pressure, pulmonary capillary wedge pressure [PCWP], and blood pressure) and echocardiography. Data were recorded at up to 4 speed settings. Speed changes were in steps of 200 revolutions/min (rpm). Evaluation of functional capacity by CPX was conducted according to the modified Bruce protocol.

Results

Only 30% of patients had normal PCWPs at their original rpm settings. In going from lowest to highest speeds, cardiac output improved by 0.25 ± 0.35 L/min/step (total change, 1.28 ± 0.3 L/min), and PCWP decreased by 1.9 ± 0.73 mm Hg/step (total change, 6 ± 1.6 mm Hg). CVP and systolic blood pressure did not change significantly with rpm. The rpm assessment was adjusted based on test results to achieve CVPs and PCWPs as close to normal limits as possible, which was feasible in all patients. On CPX, all patients demonstrated good performance (peak VO2, 16.8 ± 3.5 mL/kg/min).

Conclusion

Hemodynamic ramp testing provides an objective means of optimizing rpm, and has the potential to provide good exercise tolerance.  相似文献   
996.
Chronic pain in the UK affects up to 43% of the population. The consequences include physical and psychological distress, loss of function, employment, family and social strain and increased utilization of healthcare services. Modern pain management services operate across primary, secondary and tertiary care and incorporate general practitioners, psychologists, physiotherapists, pharmacists, specialist nurses, pain physicians and surgeons. This allows for a coordinated approach to chronic pain, engaging the patient in a structured pathway from conservative measures, through to surgery if necessary. Surgical interventions have been utilized effectively throughout the 20th century for the treatment of a variety of conditions, some of which are now effectively managed with improved pharmacological approaches or novel neuromodulation techniques. Ablative procedures that aim to permanently interrupt the pain pathway still represent the final solution for some conditions, particularly those with cancer associated pain; however, the search for less invasive, less risky measures continues. This is stimulated by an increased understanding of the neurobiology of pain transmission and the physiological changes which occur in persistent pain.  相似文献   
997.
998.

Background

Major depressive disorder (MDD) is a multifactorial disease which often coexists with cognitive deficits. Depression-induced cognitive deficits are known to be associated with aberrant reward processing, neurochemical and structural alterations. Recent studies have shown that chronic electrical stimulation of brain reward areas induces a robust antidepressant effect. However, the effects of repeated electrical self-stimulation of lateral hypothalamus - medial forebrain bundle (LH-MFB) on depression-induced cognitive deficits and associated neurochemical and structural alterations in the prefrontal cortex (PFC) are unknown.

Objectives

We investigated the effect of chronic rewarding self-stimulation of LH-MFB in neonatal clomipramine (CLI) model of depression. During adulthood, neonatal CLI and saline administered rats were implanted with bilateral electrodes stereotaxically in the LH-MFB and trained to receive intracranial self-stimulation (ICSS) for 14 days. The rats were tested for depressive-like behaviors, learning and memory followed by estimation of PFC volumes, levels of monoamines and its metabolites in the PFC.

Results

We found that chronic ICSS of LH-MFB reverses CLI-induced behavioral despair and anhedonia. Interestingly, self-stimulation normalizes the impaired novel object and location recognition memory in CLI rats. The amelioration of learning impairments in CLI rats was associated with the reversal of volume loss and restoration of monoamine metabolism in the PFC.

Conclusion

We demonstrated that repeated intracranial self-stimulation of LH-MFB ameliorates CLI-induced learning deficits, reverses altered monoamine metabolism and the atrophy of PFC. Our results support the hypothesis that chronic brain stimulation rewarding experience might be evolved as a potential treatment strategy for reversal of learning deficits in depression and associated disorders.  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