全文获取类型
收费全文 | 1760篇 |
免费 | 100篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 12篇 |
儿科学 | 53篇 |
妇产科学 | 33篇 |
基础医学 | 204篇 |
口腔科学 | 25篇 |
临床医学 | 188篇 |
内科学 | 466篇 |
皮肤病学 | 75篇 |
神经病学 | 117篇 |
特种医学 | 30篇 |
外科学 | 205篇 |
综合类 | 23篇 |
一般理论 | 5篇 |
预防医学 | 155篇 |
眼科学 | 14篇 |
药学 | 121篇 |
中国医学 | 2篇 |
肿瘤学 | 137篇 |
出版年
2023年 | 9篇 |
2022年 | 13篇 |
2021年 | 65篇 |
2020年 | 22篇 |
2019年 | 36篇 |
2018年 | 35篇 |
2017年 | 29篇 |
2016年 | 35篇 |
2015年 | 45篇 |
2014年 | 61篇 |
2013年 | 82篇 |
2012年 | 150篇 |
2011年 | 127篇 |
2010年 | 70篇 |
2009年 | 62篇 |
2008年 | 118篇 |
2007年 | 92篇 |
2006年 | 116篇 |
2005年 | 118篇 |
2004年 | 97篇 |
2003年 | 105篇 |
2002年 | 94篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有1865条查询结果,搜索用时 15 毫秒
1.
2.
David L Reich Loren M Horn Sabera Hossain Suzan Uysal 《European journal of cardio-thoracic surgery》2004,25(3):401-6; discussion 406-8
OBJECTIVES: Deep hypothermic circulatory arrest (DHCA) is commonly used during thoracic aortic surgery, and is initiated only after a sufficient degree of cerebral hypothermia is induced. The criteria for initiating DHCA vary among institutions: most centers use temperature criteria, some use electroencephalography, and a minority use jugular bulb oxyhemoglobin saturation SjO(2) criteria. The purpose of this study was to determine whether the use of SjO(2) monitoring to guide the onset of DHCA was associated with better post-operative neuropsychological outcome. METHODS: Sixty-one thoracic aortic surgical patients underwent both pre- and post-operative neuropsychological testing. Patients were divided into three groups: (1) those with SjO(2)> or =95% at DHCA onset; (2) those with SjO(2)<95% at DHCA onset; and (3) those without SjO(2) monitoring. RESULTS: There were no statistically significant differences in the incidence of post-operative decline in neuropsychological function among the three groups of patients. Patients in whom SjO(2) data were used to guide onset of DHCA had lower esophageal and bladder temperatures at that time compared with patients without SjO(2) monitoring. CONCLUSIONS: Monitoring of SjO(2) had no apparent effect upon post-operative neuropsychological outcome, and there were no trends in our small patient cohort suggesting differences that our study was not adequately powered to detect. Use of SjO(2) monitoring was associated with more profound hypothermia prior to DHCA due to more prolonged cooling in attempts to bring the SjO(2) above the 95% threshold. Using our institutional cooling protocol, SjO(2) monitoring does not appear to increase neuroprotection in patients undergoing DHCA for thoracic aortic repairs. 相似文献
3.
L F Hiratzka C L Eastham J G Carter J R Moyers D R Elliott D B Doty C B Wright M L Marcus 《The Annals of thoracic surgery》1988,45(5):474-481
In normal coronary arteries, reactive hyperemic responses to a 20-second occlusion, an index of coronary reserve, usually demonstrate a peak-to-resting flow velocity ratio of 4:1 or more. Most intraoperative studies that have assessed reactive hyperemic responses in bypassed vessels have reported peak-to-resting flow velocity ratios of 2:1 or less following a 20-second occlusion. These decreased reactive hyperemic responses could be due to coronary vasodilatation after cardiopulmonary bypass or to an inadequate physiological result of the surgical procedure. In 14 patients with angiographically normal coronary arteries, the peak-to-resting flow velocity ratio following a 20-second coronary occlusion decreased significantly (p less than 0.05) from 4.4 +/- 0.2 (mean +/- standard error) before bypass to 3.0 +/- 0.3 after bypass. In a similar dog model, the peak-to-resting flow velocity ratio decreased by 36 to 52% during the first hour following one hour of cardiopulmonary bypass and cardioplegia. During the same period, left ventricular perfusion increased 21 to 30%, mean arterial pressure and coronary vascular resistance decreased, and myocardial oxygen consumption was unchanged. In a second group of dogs studied for the effects of duration (200 to 240 minutes) of anesthesia and thoracotomy alone, peak-to-resting flow velocity ratio was significantly lower. These clinical and experimental studies suggest that major coronary vasodilatation occurs early following cardiopulmonary bypass and cold cardioplegia, and may contribute to the blunted coronary reactive hyperemic responses reported during this time. Consequently, an intraoperative peak-to-resting flow velocity ratio of 3:1 for bypassed coronary arteries may represent an excellent physiological result. 相似文献
4.
5.
Stephanie Stouder Loren Jones Scott Brietzke Eric A Mair 《Otolaryngology--head and neck surgery》2007,136(5):827-831
OBJECTIVES: Oral appliances are designed to treat snoring and sleep apnea by advancing the mandible and tongue. We test the hypothesis that an oral appliance affects palatal snoring as well as tongue base obstruction. METHODS: Prospective observational cohort study. Sixty patients with a chief complaint of snoring with or without apnea were enrolled. Each patient underwent a home sleep test followed by 3 weeks sleeping with an oral appliance. Each patient then underwent a repeat home sleep test while using the device. RESULTS: There was a statistically significant improvement in the snores per hour (P = 0.0005), the maximum snoring loudness (P = 0.0001), average snoring loudness (P = 0.00001), and the percentage of palatal snoring (P = 0.0007). There was also a significant decrease in oxygen desaturation events (P = 0.003). CONCLUSIONS: This study suggests oral appliances may be effective treatment for both palatal and tongue base snoring. 相似文献
6.
7.
Leanne Tamm Jeffery N. Epstein Richard E.A. Loren Stephen P. Becker Sarah B. Brenner Morgan E. Bamberger 《Journal of clinical child and adolescent psychology》2019,48(2):S131-S145
This goal of this study was to assess the initial feasibility and efficacy of a play-based intervention targeting executive functions (EF) and parent–child relationships in preschoolers compared with an active control group. Preschoolers with EF deficits (M age = 3.7 ± 0.47, predominantly White boys) and their parents were randomized to intervention (n = 36) or active control (n = 32) conditions. Child performance on EF tasks, parent and masked teacher ratings of EF and behavior, and masked clinician ratings of severity were collected at baseline and at 3 and 6 months postbaseline. Partial eta-squared effect sizes at .02 or higher comparing performance across the two groups was considered evidence of meaningful, albeit small, intervention effects. Intervention effects were observed for parent ratings of inattention, hyperactivity/impulsivity, and number/severity of problems experienced in various home situations, teacher ratings of severity of problems in various school situations, parent and teacher ratings of overall impairment, and clinician ratings of impairment. Intervention effects for functional improvements were maintained at the 6-month follow-up. No effect of the intervention was observed on the objective EF measures, although parent ratings of emotional control were improved for children in the intervention group. An intervention utilizing play-based activities targeting EF, when administered in a structured way by parents, is a promising approach for improving behavior in preschoolers with self-regulation deficits. More work is needed to investigate potential impact on EF and to disentangle mechanisms of action. It may be that the intervention’s focus on the structure and quality of parent–child interactions is a mediator of outcomes, rather than improved EFs. 相似文献
8.
Differential expression of CD22 (Lyb8) on murine B cells 总被引:2,自引:0,他引:2
Erickson Loren D.; Tygrett Lorraine T.; Bhatia Sudershan K.; Grabstein Kenneth H.; Waldschmidt Thomas J. 《International immunology》1996,8(7):1121-1129
Previous studies have established the distribution, biochemistryand functional attributes of human CD22, a B cell-restrictedglycoprotein. Recently, molecular cloning of the murine CD22equivalent revealed this molecule to be the same as the previouslydescribed Lyb8 alloantigen. Using the anti-Lyb8 mAb Cy34.1.2,the present report documents the expression patterns of CD22within the murine B cell compartment. The results demonstratethat in the bone marrow, murine CD22 is absent on the surfaceof pro-B cells, pre-B cells and newly emerging lgM+ B cells.CD22 is present at a low density on immature IgMhi B cells andfully expressed on mature recirculating B cells. In the periphery,murine CD22 is expressed at mature levels on all B cell subsetsincluding follicular, marginal zone, B1 and switched B cells.Further studies showed CD22 to be retained on activated murineB cells for extended periods. Finally, in combination with CD23and heat stable antigen, CD22 can be used to delineate the immaturesplenic B cells, and distinguish them from follicular and marginalzone cells. Together, the results demonstrate murine CD22 tobe a useful pan marker for all mature B cell subsets. 相似文献
9.
Pseudopregnant, pregnant, and ovariectomized rabbits were utilized to study hormonal mediation of uterine epithelial surface negativity and glycocalyx morphology, and to seek local effects of blastocysts at sites of implantation. A loss of surface negativity [polycationic ferritin (PCF) binding] by day 6 of pregnancy or pseudopregnancy was noted, accompanied by alterations in epithelial glycocalyx. Uteri from estrous animals, or ovariectomized animals receiving oil or estradiol injections, bound PCF and exhibited a “globular” glycocalyx. Uteri from day 6 pseudopregnant or pregnant animals, or ovariectomized animals receiving progesterone injections, did not bind PCF or exhibit a globular glycocalyx. Both PCF binding and the globular character of the epithelial glycocalyx were sensitive to neuraminidase and trypsin treatment, suggesting sialoglycoprotein contribution to surface negativity. Implanting blastocysts had no detectable local effect on surface negativity, but did induce local reduction of epithelial glycocalyx at sites of implantation. Results of this study suggest that uterine epithelial glycocalyx alterations during the preimplantation period reflect a general response to prosgesterone stimulation, primarily qualtitative in nature, related to the acquisition of receptivity to ovo-implantation. 相似文献
10.
Numerical simulation of aerosol particle transport by oscillating flow in respiratory airways 总被引:2,自引:0,他引:2
James K. Briant Duane D. Frank Anthony C. James L. Loren Eyler 《Annals of biomedical engineering》1992,20(6):573-581
Particle transport by oscillating flow in a tapered channel or in a tapered tube was computed from the complete equations
of motion. These geometries represent a simplified model of the divergent flow field of the mammalian bronchial tree. The
computed deformation profile of a line of particles, transported by the oscillatory motion, was compared with prior experimental
results and analytical calculations. All three methods agree that there is transport in the divergent direction of the tube
by an axial stream of steady drift in the core for moderately high frequency of oscillation (Womersley parameter in the range
of 1 to 10). Bidirectional flow is established by an annular stream in the convergent direction, with no net flow on integral
cycles of the oscillating fluid. At higher frequency, however, the steady stream transforms to a different shape in the tapered
tube, with transport in the divergent direction nearer the walls of the tube, rather than in the core. Transport by the continuing
streams with oscillatory ventilation of the respiratory tract should deliver medicinal aerosols of low intrinsic particle
mobility to the peripheral regions of the lungs. 相似文献