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   1954篇
  免费   102篇
  国内免费   18篇
耳鼻咽喉   9篇
儿科学   53篇
妇产科学   37篇
基础医学   260篇
口腔科学   80篇
临床医学   240篇
内科学   440篇
皮肤病学   20篇
神经病学   95篇
特种医学   155篇
外科学   203篇
综合类   26篇
预防医学   82篇
眼科学   15篇
药学   207篇
肿瘤学   152篇
  2022年   13篇
  2021年   35篇
  2020年   18篇
  2019年   24篇
  2018年   31篇
  2017年   26篇
  2016年   36篇
  2015年   27篇
  2014年   51篇
  2013年   63篇
  2012年   99篇
  2011年   111篇
  2010年   64篇
  2009年   52篇
  2008年   69篇
  2007年   89篇
  2006年   58篇
  2005年   59篇
  2004年   49篇
  2003年   75篇
  2002年   77篇
  2001年   68篇
  2000年   66篇
  1999年   52篇
  1998年   38篇
  1997年   36篇
  1996年   40篇
  1995年   26篇
  1994年   21篇
  1993年   20篇
  1992年   28篇
  1991年   35篇
  1990年   36篇
  1989年   44篇
  1988年   36篇
  1987年   37篇
  1986年   20篇
  1985年   18篇
  1984年   15篇
  1983年   17篇
  1982年   14篇
  1981年   14篇
  1979年   21篇
  1978年   17篇
  1977年   19篇
  1976年   14篇
  1975年   18篇
  1972年   28篇
  1969年   16篇
  1968年   18篇
排序方式: 共有2074条查询结果,搜索用时 15 毫秒
71.
72.
A human O6-alkylguanine-DNA-alkyltransferase (ATase) cDNA-containing retrovirus was used to infect murine long-term primary bone marrow cultures. High levels of ATase expression were obtained, and colony- forming cells of the granulocyte-macrophage lineage from the cultures transduced with the human ATase retrovirus were three times more resistant to the alkylating agent, N-methyl-N-nitrosourea (MNU), than control cultures. Furthermore, expression of the human ATase protected long-term hematopoiesis, measured as the output of progenitor cells to the nonadherent fraction of the culture, against the cytotoxic effects of repeated exposures to MNU. These results clearly show that a human ATase cDNA-containing retrovirus can be used to infect long-term primary bone marrow cultures and that this attenuates their sensitivity to nitrosoureas.  相似文献   
73.
Direct and indirect biomarkers are widely applied for the determination of alcohol consumption. They help to assess past or present alcohol consumption. Depending on the window of detection and sensitivity of the investigated marker, punctual alcohol consumption may remain undetected. In this study, different sampling strategies for the intermediary long‐term marker phosphatidylethanol (PEth) are evaluated and compared to the determination of the short‐term markers ethyl glucuronide (EtG) and ethyl sulfate (EtS) in urine. Samples from 19 patients undergoing alcohol use disorder treatment were collected during the withdrawal treatment and successive rehabilitation (33 ± 26 days (range: 3–74 days)). With liquid chromatography–tandem mass spectrometry (LC–MS/MS) EtG and EtS in urine, PEth in blood, PEth in dried blood spot (DBS) from venous blood, and PEth in DBS from capillary blood were quantified and compared. The use of volumetric capillary DBS, prepared from 20 μL of blood, provided the same results as the use of venous DBS (95% ± 10%, R2 0.9899 for PEth 16:0/18:1). Capillary DBS sampling has the advantage that it can be performed without venipuncture. The use of PEth in DBS proved to prevent post‐sampling degradation, providing a longer detection in comparison to PEth in liquid blood, which only showed 67% ± 24% of the PEth DBS 16:0/18:1 concentration. When compared with EtG and EtS in urine, PEth monitoring proved to be advantageous for the detection of relapse situations, as the accumulation of PEth in blood prolongs the detectability. In conclusion, volumetric capillary DBS sampling for PEth is a simple and useful tool for compliance monitoring, and avoids hematocrit issues.  相似文献   
74.
Pfeifer M 《Der Internist》2012,53(5):534-544
The total anatomical and functional apparatus which allows normal ventilation of the lungs is known as the respiratory pump. An insufficiency of this system, which can be caused by a multitude of reasons, primarily affects the inspiratory musculature and especially the diaphragm. One of the essential clinical characteristics is rapid shallow breathing. Exhaustion of the repiratory musculature due to acute respiratory insufficiency is normally clinically registered but can also be functionally determined in particular by the maximum static inspiratory closed mouth pressure. A further option is invasive measurement of the transdiaphragmal pressure, which however is not suitable as a routine procedure. Mechanical ventilation is used as treatment of respiratory pump insufficiency independent of the cause. This is initially a non-invasive procedure but if unsuccessful intubation and invasive ventilation are indicated. The technical developments in the field of extracorporeal gas exchange systems are very promising. However, in view of the insufficient data, ventilation procedures using masks and tubes still remain the first choice methods.  相似文献   
75.
We describe a novel clinical phenotype associating T- and B-cell lymphopenia, intermittent neutropenia, and atrial septal defects in 3 members of a consanguineous kindred. Their clinical histories included recurrent bacterial infections, viral infections, mucocutaneous candidiasis, cutaneous warts, and skin abscesses. Homozygosity mapping and candidate gene sequencing revealed a homozygous premature termination mutation in the gene STK4 (serine threonine kinase 4, formerly having the symbol MST1). STK4 is the human ortholog of Drosophila Hippo, the central constituent of a highly conserved pathway controlling cell growth and apoptosis. STK4-deficient lymphocytes and neutrophils exhibit enhanced loss of mitochondrial membrane potential and increased susceptibility to apoptosis. STK4 deficiency is a novel human primary immunodeficiency syndrome.  相似文献   
76.

Introduction

In 2006 the National Confidential Enquiry into Patient Outcome and Death undertook a large prospective study of trauma care, which revealed several findings pertaining to the management of head injuries in a sample of 493 patients.

Methods

Case note data were collected for all trauma patients admitted to all hospitals accepting emergencies in England, Wales, Northern Ireland and the Channel Islands over a three-month period. Severely injured patients with an injury severity score (ISS) of ≥16 were included in the study. The case notes for these patients were peer reviewed by a multidisciplinary group of clinicians, who rated the overall level of care the patient received.

Results

Of the 795 patients who met the inclusion criteria for the study, 493 were admitted with a head injury. Room for improvement in the level of care was found in a substantial number of patients (265/493). Good practice was found to be highest in high volume centres. The overall head injury management was found to be satisfactory in 84% of cases (319/381).

Conclusions

This study has shown that care for trauma patients with head injury is frequently rated as less than good and suggests potential long-term remedies for the problem, including a reconfiguration of trauma services and better provision of neurocritical care facilities.  相似文献   
77.
78.
79.

Background

Thoracic and extremity injuries are common in polytraumatized patients. The clavicle limits the upper thoracic cage and connects the body and upper extremities. It is easy to examine and is visible on standard emergency room radiographs. We hypothesize that clavicular fracture in polytrauma patients indicates the presence of further injuries of the upper extremities, head, neck and thorax.

Material and methods

Retrospective study including patients admitted between 2008 and 2012 to a level-I trauma center. Inclusion criteria: ISS?>?16, two or more injured body regions, clavicular fracture. Control group: patients admitted in 2011, ISS?>?16, two or more injured body regions, no clavicular fracture. Patient information was obtained from the patients’ charts; evaluation of radiographic findings was performed; scoring was based on the Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS) AIS/ISS; data were analyzed using Pearson’s correlation and the Mann–Whitney U-test in SPSS (version 11.5.1); graphs were drawn using EXCEL®.

Results

Thirty-four patients with clavicular fracture (C+) and 40 without (C-) were included; the mean ISS was 25 (range 16–57), m?=?70%, f?=?30%; age 43.3 years (range 9–88); clavicular fractures were positively correlated with severe thoracic (p?=?0.011, OR 4.5: KI 1.3–15.3), external (p?<?0.001, OR 9.2: KI 2.7–30.9) and upper extremity injuries (p?<?0.001, OR 33.2: KI 6.9–16.04 resp. p?=?0.004, OR 12.5: KI 1.5–102.9). C?+?showed a lower head/neck AIS (p?=?0.033), higher thorax AIS (p?=?0.04), arm/shoulder AIS (p?=?0.001) and external AIS (0.003) than C-. Mean hospital stay and ICU treatment time were longer in the C?+?group (p?=?0.001 and p?=?0.025 respectively).

Conclusion

A clavicular fracture can be diagnosed easily and may be used as a pointer for further thoracic and upper extremity injuries in polytrauma patients that might have been otherwise missed. Special attention should be paid on second and tertiary survey.
  相似文献   
80.
Current challenges in adhesive dentistry include over-hydrophilic bonding formulations, which facilitate water percolation through the hybrid layer and result in unreliable bonded interfaces. This study introduces nanogel-modified adhesives as a way to control the material's hydrophobic character without changing the basic monomer formulation (keeping water-chasing capacity and operatory techniques unaltered). Nanogel additives of varied hydrophobicity were synthesized in solution, rendering 10- to 100-nm-sized particles. A model BisGMA/HEMA solvated adhesive was prepared (control), to which reactive nanogels were added. The increase in adhesive viscosity did not impair solvent removal by air-thinning. The degree of conversion in the adhesive was similar between control and nanogel-modified materials, while the bulk dry and, particularly, the wet mechanical properties were significantly improved through nanogel-based network reinforcement and reduced water solubility. As preliminary validation of this approach, short-term micro-tensile bond strengths to acid-etched and primed dentin were significantly enhanced by nanogel inclusion in the adhesive resins.  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