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   862篇
  免费   39篇
  国内免费   9篇
耳鼻咽喉   1篇
儿科学   22篇
妇产科学   11篇
基础医学   98篇
口腔科学   7篇
临床医学   122篇
内科学   153篇
皮肤病学   11篇
神经病学   27篇
特种医学   189篇
外科学   158篇
综合类   18篇
预防医学   25篇
眼科学   1篇
药学   48篇
肿瘤学   19篇
  2021年   8篇
  2020年   6篇
  2019年   11篇
  2018年   6篇
  2017年   8篇
  2016年   4篇
  2015年   7篇
  2014年   19篇
  2013年   17篇
  2012年   22篇
  2011年   23篇
  2010年   35篇
  2009年   19篇
  2008年   25篇
  2007年   26篇
  2006年   27篇
  2005年   24篇
  2004年   27篇
  2003年   18篇
  2002年   21篇
  2001年   20篇
  2000年   31篇
  1999年   18篇
  1998年   27篇
  1997年   27篇
  1996年   20篇
  1995年   18篇
  1994年   21篇
  1993年   15篇
  1992年   12篇
  1991年   24篇
  1990年   32篇
  1989年   34篇
  1988年   22篇
  1987年   25篇
  1986年   31篇
  1985年   21篇
  1984年   25篇
  1983年   15篇
  1982年   15篇
  1981年   8篇
  1980年   11篇
  1979年   16篇
  1978年   11篇
  1977年   13篇
  1976年   9篇
  1975年   10篇
  1974年   4篇
  1972年   5篇
  1968年   3篇
排序方式: 共有910条查询结果,搜索用时 187 毫秒
1.
Purpose: Despite their efficacy, LVADs remain associated with serious complications. The relationship between haemodynamic changes during support and outcome remains inadequately characterised. This association was investigated in LVAD recipients undergoing prolonged support.Methods: Forty patients receiving LVAD therapy for >2 years were reviewed retrospectively (mean support duration was 38.62 ± 15.28). Pre- and on-LVAD haemodynamic data were assessed in three groups: (1) those receiving ongoing support (n = 24); (2) those who underwent cardiac transplantation (n = 4); (3) those who died during support (n = 12).Results: For group 1 and 2, LVAD support achieved a decrease in mean PAP, mean PCWP, TPG, and PVR and an increase in thermodilution blood flow (TBF) with significance at ≤5% level. For group 3, there were non-significant changes in TPG and PVR at the 5% level but for mean PAP, mean PCWP, and TBF the changes were similar to Groups 1 and 2 with significance at ≤5% level. Aggregated data from all three groups showed a 58% increase in TBF on LVAD support.Conclusion: Highly significant and favourable haemodynamic changes were found. However, group 3 did not undergo decrease in TPG and PVR possibly because of suboptimal LVAD flow, right heart dysfunction and unavoidable prolongation of support.  相似文献   
2.
Cyclosporin nephrotoxicity in heart and lung transplant patients   总被引:1,自引:0,他引:1  
Twenty-two patients with heart, lung or heart and lung transplants maintained on cyclosporin for periods ranging from 3 months to 10 years developed renal insufficiency which was investigated by renal biopsy. The histopathological changes were: (i) severe vascular and glomerular damage due to thrombotic microangiopathy (TM); (ii) a form of focal segmental glomerulosclerosis (FSGS); (iii) glomerular ischaemia. Rather than being separate entities, these changes appeared to represent a spectrum of pathology, some biopsies showing all three forms of glomerular injury. In all cases the glomerular changes were accompanied by arteriolar and arterial pathology, and we identified novel ultrastructural changes in the arteriolar endothelial basal lamina. Tubular atrophy was a consistent feature, the severity of which reflected the severity of the glomerular sclerosis, and which appeared to be a consequence of glomerular loss. Our findings are consistent with the nephrotoxic effects of cyclosporin being mediated chiefly via damage to preglomerular vessels and glomerular capillary endothelium. From an analysis of the clinical aspects of these cases, the effects of cyclosporin appear to be to some extent idiosyncratic, and therefore not entirely preventable, but strict monitoring of blood cyclosporin levels is essential to minimize the risk of permanent renal damage. Monitoring urinary protein in addition to plasma creatinine may detect the onset of FSGS, as proteinuria precedes creatinine elevation.   相似文献   
3.
BACKGROUND: Testing for antibody to hepatitis B core antigen (anti-HBc) as a surrogate for hepatitis C viremia is no longer needed for blood donor screening. Currently, the important question is how much its use supplements hepatitis B surface antigen (HBsAg) donor screening in preventing transfusion-transmitted hepatitis B virus (HBV) infection. STUDY DESIGN AND METHODS: In a study conducted in the 1970s, 64 blood donors were associated with 15 cases of HBV (1.0%) in 1533 transfusion recipients. Sera from 61 donors at donation and 29 follow-up visits were available for present-day assays for HBsAg, HBV DNA, anti-HBc, and antibody to HBsAg (anti-HBs). RESULTS: HBsAg was found in four previously negative blood donors; HBV DNA was limited to three of these four. Anti-HBc was detected in six HBsAg-negative donors. Two other donors were negative in all assays at donation, but positive for anti- HBc and anti-HBs 2 to 4 months later. The remaining donors were negative for all HBV markers, which left five recipient cases unexplained. No HBV transmission was observed when anti-HBs sample-to- negative control values were > or = 10. CONCLUSION: Some 33 to 50 percent of cases of hepatitis B that could be transmitted by transfusion of blood from HBsAg-negative donors are prevented by anti- HBc screening. Anti-HBc-positive donors unequivocally positive for anti- HBs should be considered noninfectious for HBV and should be allowed to donate. Anti-HBc screening of paid plasmapheresis donors, supplemented by anti-HBs testing, would reduce the amount of HBV to be processed by virus inactivation and increase the content of anti-HBs in plasma pools.  相似文献   
4.

Background

Injuries represent a significant and growing public health concern in China. This Review was conducted to document the characteristics of injured patients presenting to the emergency department of Chinese hospitals and to assess of the nature of information collected and reported in published surveillance studies.

Methods

A systematic search of MEDLINE and China Academic Journals supplemented with a hand search of journals was performed. Studies published in the period 1997 to 2007 were included and research published in Chinese was the focus. Search terms included emergency, injury, medical care.

Results

Of the 268 studies identified, 13 were injury surveillance studies set in the emergency department. Nine were collaborative studies of which eight were prospective studies. Of the five single centre studies only one was of a prospective design. Transport, falls and industrial injuries were common mechanisms of injury. Study strengths were large patient sample sizes and for the collaborative studies a large number of participating hospitals. There was however limited use of internationally recognised injury classification and severity coding indices.

Conclusion

Despite the limited number of studies identified, the scope of each highlights the willingness and the capacity to conduct surveillance studies in the emergency department. This Review highlights the need for the adoption of standardized injury coding indices in the collection and reporting of patient health data. While high level injury surveillance systems focus on population-based priority setting, this Review demonstrates the need to establish an internationally comparable trauma registry that would permit monitoring of the trauma system and would by extension facilitate the optimal care of the injured patient through the development of informed quality assurance programs and the implementation of evidence-based health policy.  相似文献   
5.
Responses to the synthetic terpolymer L-glutamic acid, L-lysine, L-tyrosine (GLT) in the mouse are controlled by H-2-1inked Ir-GLTgenes. (Responder × nonresponder) F(1) hybrid mice, themselves phenotypic responders, can be primed with GLT to develop specific helper cells capable of interacting with 2,4-dinitrophenyl hapten (DNP)-primed F(1) B cells in response to DNP-GLT. Unlike the indiscriminant ability of F(1) helper T cells for conventional antigens (i.e. not Ir gene-controlled), which can help B cells of either parental type (as well as F(1)) equally well, GLT-primed F(1) T cells can only provide help under normal circumstances for B lymphocytes of responder parent origin; they are unable to communicate effectively with nonresponder parental B cells (1, and the present studies). The present studies reveal, however, that the induction of a parental cell-induced allogeneic effect during priming of F(1) mice to GLT actually dictates the direction of cooperating preference that will be displayed by such F(1) helper cells for B cells of one parental type or the other. Thus, F(1) T cells, primed to GLT under the influence of an allogeneic effect induced by parental BALB/c cells, develop into effective helpers for nonresponder A/J B cells, but fail to develop effective helpers for responder BALB/c B cells, and vice-versa. In contrast, F(1) T cells, primed to GLT under the influence of an allogeneic effect induced by either parental type, display significantly enhanced levels of helper activity for B cells derived from F(1) donors. These results are interpreted to reflect the existence of two interdependent events provoked by the allogeneic effect: one event augments the differentiation of GLT-specific helper T cells belonging to the subset corresponding to the opposite parental type; this would explain the development of increased helper activity provided to partner B cells of opposite parental type (as well as of F(1) origin). The second event, we postulate, involves the production of responses against the receptors which normally self-recognize native cell interaction determinants; this form of anti-idiotype response is restricted against self- recognizing receptors of the same parental type used for induction of the allogeneic effect, hence explaining diminished helper activity of such F(1) cells for partner B lymphocytes of corresponding parental type.  相似文献   
6.
7.
International Journal of Legal Medicine - Autopsies continue to be the most reliable source of mortality statistics; however, more and more death certificates are based on the post-mortem external...  相似文献   
8.

Background

Mood is an independent predictor of mortality and quality of life (QoL) for people with heart failure. However, the underlying belief systems involved in mood are unknown.

Objective

We sought to identify psychological and clinical variables predicting mood and QoL for people diagnosed with heart failure (HF).

Methods

One hundred and forty-six HF patients were assessed with standardized measures, to determine their beliefs about HF, coping styles, mood, and QoL.

Results

Patients with more negative beliefs about the consequences of HF and with less perceived control over symptoms showed maladaptive coping styles such as denial and behavioral disengagement, and more severe levels of depression and anxiety. Depression also independently predicted QoL outcomes.

Conclusions

Anxious and depressed patients have more negative beliefs about HF, leading to negative coping behaviors and poor QoL. Our evidence suggests that changing negative beliefs may improve the psychological well-being and QoL of patients, irrespective of disease severity.  相似文献   
9.
AIMS: To investigate the response to inhaled prostacyclin in patientswith primary and secondary pulmonary hypertension and to compareits effects to those of intravenous prostacyclin and inhalednitric oxide. METHODS AND RESULTS: Twelve patients with pulmonary hypertension (seven primary andfive secondary) were studied. All patients had a pulmonary arteryballoon flotation catheter inserted into the proximal pulmonaryartery and radial arterial line. Prostacyclin was nebulizedwith 81. min–1 of oxygen and administered in doses increasingfrom 15 to 50 ng. kg–1. min–1 via a facemask. Eightof these patients also received intravenous prostacyclin indoses of 1 to 5 ng.kg–1.min–1 and nitric oxide indoses of 10 to 100 ppm via a facemask. Haemodynamic measurementswere taken during each treatment. In the 12 patients, nebulizedprostacyclin produced a significant reduction in mean pulmonaryartery pressure from 56±5 to 45±4 mmHg (P=0·0001).The pulmonary vascular resistance decreased by 38% from 964±169to 595±116 dyne s–1.cm–5 (P=0·0001).Direct comparison with inhaled nitric oxide and intravenousprostacyclin in eight patients demonstrated that nebulized prostacyclinproduced a greater fall in mean pulmonary artery pressure thanthe other two agents without any significant effect on systemicarterial pressure. CONCLUSION: Nebulized prostacyclin appears to be more effective at reducingpulmonary artery pressure in patients with pulmonary hypertensionwhen compared to intravenous prostacyclin and inhaled nitricoxide. This could have important clinical implications for themanagement of patients with pulmonary hypertension.  相似文献   
10.
A variety of common pediatric emergencies were created in anesthetized cats to provide pediatric house officers and practicing physicians with an opportunity to refine diagnostic and management skills in a controlled environment under supervision. We describe the format of the animal model drill, outline protocols for stimulating pediatric critical care emergencies, and present preliminary evaluation data from a continuing medical education workshop and from house staff drills regarding the efficacy of the program.  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