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   722篇
  免费   35篇
  国内免费   21篇
耳鼻咽喉   3篇
儿科学   38篇
妇产科学   2篇
基础医学   82篇
口腔科学   18篇
临床医学   80篇
内科学   217篇
皮肤病学   21篇
神经病学   31篇
特种医学   121篇
外科学   52篇
综合类   13篇
预防医学   34篇
眼科学   1篇
药学   29篇
中国医学   1篇
肿瘤学   35篇
  2023年   2篇
  2022年   3篇
  2021年   16篇
  2020年   4篇
  2019年   4篇
  2018年   6篇
  2017年   8篇
  2016年   8篇
  2015年   12篇
  2014年   16篇
  2013年   20篇
  2012年   20篇
  2011年   17篇
  2010年   31篇
  2009年   40篇
  2008年   16篇
  2007年   32篇
  2006年   21篇
  2005年   18篇
  2004年   18篇
  2003年   15篇
  2002年   11篇
  2001年   21篇
  2000年   9篇
  1999年   16篇
  1998年   36篇
  1997年   38篇
  1996年   32篇
  1995年   31篇
  1994年   12篇
  1993年   23篇
  1992年   5篇
  1991年   10篇
  1990年   11篇
  1989年   13篇
  1988年   19篇
  1987年   15篇
  1986年   9篇
  1985年   15篇
  1984年   19篇
  1983年   10篇
  1982年   16篇
  1981年   7篇
  1980年   11篇
  1978年   16篇
  1977年   11篇
  1976年   16篇
  1975年   7篇
  1974年   3篇
  1970年   2篇
排序方式: 共有778条查询结果,搜索用时 15 毫秒
41.
42.
BACKGROUND: Gastroesophageal reflux disease (GERD)-induced pulmonary symptoms (PS) can be difficult to control. The effectiveness of laparoscopic fundoplication (LF) in controlling PS among patients with medically recalcitrant GERD is poorly documented. We evaluated our results in controlling important PS in patients with GERD undergoing LF. METHODS: Seventy-four patients (28 men, 46 women) were identified with clinically important PS from a prospective cohort of 155 patients undergoing elective LF for recalcitrant GERD. Median age was 52.5 years (range, 29-84 years). Sixty-seven (91%) patients were taking proton pump inhibitors at the time of operation. Quality of life by using the SF36 physical (PCS) and mental (MCS) component summary scores (normal, 50) and heartburn severity by using the health-related quality of life (HRQOL) (best score, 0; worst score, 45) were measured. RESULTS: All 74 patients with PS survived operation, and minor morbidity occurred in 5 (7%) patients. Median hospital stay was 2 days (range, 1-6 days), and return to normal activity was seen at 2.2 weeks (range, 1-8 weeks). Median follow-up was 12 months. PS were improved significantly (P < .01) for hoarseness (62% to 17.6%), bronchospasm (60% to 9.5%), and aspiration (22% to 1.4%). Before LF, 11 (14.9%) patients required bronchodilators or oral steroids. Postoperatively such therapy was required in only 3 (4.2%) patients (P = .019), with no patient requiring oral steroids. Patients with poorer control of their GERD on the basis of high HRQOL scores had significantly more PS after operation. CONCLUSIONS: A significant number of patients with medically recalcitrant GERD (46% from our prospective database) have important PS. LF can improve PS, decrease requirement for pulmonary medications, as well as improve typical reflux symptoms and quality of life.  相似文献   
43.
Medical ultrasound is a highly valuable diagnostic tool, especially when compared with other imaging modalities. It is a noninvasive, real-time, portable, extremely safe method compared with X-ray and inexpensive relative to magnetic resonance imaging. However, ultrasound is limited in its ability to distinguish between diseased and normal tissue. This limitation has led to the development of contrast agents. We have produced novel poly (lactic-co-glycolic) acid air-filled microcapsules that work well as ultrasound contrast agents, giving up to 24 and 25 dB enhancement when insonated in the medical imaging range at 5 and 7.5 MHz, respectively. The capsules were fabricated by modifying a double emulsion method to encapsulate camphor in the oil phase and ammonium carbonate in the aqueous phase, and later sublime the encapsulated material, leaving voids capable of being filled with a gas in their place. The role of the surfactant, poly vinyl alcohol, solution temperature, was studied and found to play an important role in the morphology of the capsules, altering their acoustic response.  相似文献   
44.
The influence of melatonin on hippocampal evoked potentials initiated by low- and high-frequency electrical stimulations and by two pulses applied in rapid succession was investigated. In confirmation of our previous studies, melatonin attenuated the population spike triggered by low-frequency stimulation (0.03 Hz). High-frequency stimulation (HFS; 100 Hz for 1 sec, three times every 10 sec), which in control slices permanently facilitated neuronal excitability (347% +/- 32%), was also able to amplify the melatonin-depressed potential (467.8% +/- 59.6%). Because melatonin is a hydrophobic molecule, it was dissolved and applied in ethanol. Ethanol (0.4%) by itself reduced the magnitude of HFS-induced potentiation (233.5% +/- 16.8%). The slices stimulated with two pulses separated with a delay longer than 15 msec demonstrated a facilitation of the response to the second stimuli (paired-pulse facilitation; PPF). The influence of melatonin (100 microM) on PPF was biphasic: Shortly after addition of melatonin, PPF was briefly (5-10 min) reversed to paired-pulse inhibition (PPI), which gradually returned to a stable PPF. Ethanol (0.4%) applied without melatonin exerted only a marginal, facilitatory effect on PPF. The delay between two successively applied pulses, shorter than 13 msec, resulted in attenuation of the response to the second stimuli (PPI). Melatonin (100 microM) reversed the attenuation of the second potential within 15-20 min following its application. Ethanol applied by itself at the concentration of 0.4% temporarily (5-10 min), but significantly, depressed the second potential. These results demonstrate the ability of melatonin to modulate specific forms of plasticity in hippocampal pyramidal neurons.  相似文献   
45.
46.
A controlled trial of elective intervention with continuous inflating pressure (CIP) was performed in infants with severe hyaline membrane disease who weighed more than 1000 g at birth. Infants entered the trial if their arterial oxygen tension (PaO2) fell below 60 mmHg while breathing a fractional inspired oxygen concentration (F1O2) greater than 0-95. 11 out of 12 infants in the CIP-treated group and 10 out of 12 in the control group survived. 7 treated and 6 control infants required mechanical ventilation. When CIP was started the Pao2 of the treated infants increased, and they breathed high concentrations of oxygen for a significantly shorter period than the control infants. During the 31-month duration of the trial 107 other infants with severe hyaline membrane disease were admitted who did not meet the criteria for entry to the trial. 37 survived after breathing high concentrations of oxygen (F1O2 greater than 0-60) spontaneously without any ventilatory assistance, and the remaining 70 infants were already being ventilated on their arrival in the unit, usually because they had required mechanical ventilation during transfer from other hospitals. The neonatal survival rate for those infants born in this hospital during the study period was 88% (50 out of 57 infants) and for those referred from other hospitals it was 69% (51 out of 74 infants). The maximum further increase in overall survival rate that might have been achieved in our population of infants if CIP had been initiated very early in the course of the illness was 5%--i.e. from 77% (101/131) to 82% (107/131).  相似文献   
47.
Aim: The aim of this study was to determine if asthmatic children have viruses more commonly detected in lower airways during asymptomatic periods than normal children. Methods: Fifty‐five asymptomatic children attending elective surgical procedures (14 with stable asthma, 41 normal controls) underwent non‐bronchoscopic bronchoalveolar lavage. Differential cell count and PCR for 13 common viruses were performed. Results: Nineteen (35%) children were positive for at least one virus, with adenovirus being most common. No differences in the proportion of viruses detected were seen between asthmatic and normal ‘control’ children. Viruses other than adenovirus were associated with higher neutrophil counts, suggesting that they caused an inflammatory response in both asthmatics and controls (median BAL neutrophil count, 6.9% for virus detected vs. 1.5% for virus not detected, p = 0.03). Conclusions: Over one‐third of asymptomatic children have a detectable virus (most commonly adenovirus) in the lower airway; however, this was not more common in asthmatics. Viruses other than adenovirus were associated with elevated neutrophils suggesting that viral infection can be present during relatively asymptomatic periods in asthmatic children.  相似文献   
48.
Albumin is used as a plasma expander in critically ill patients and for several other clinical applications mainly via intravenous infusion. Oral administration of albumin can improve patient compliance although limited oral bioavailability of proteins is still a major challenge. Although nanomaterials have been extensively utilized for improving oral delivery of proteins, albumin has been utilized only as either a model drug or as a carrier for drug delivery. In the current study, for the first time, chitosan nanoparticles have been developed and extensively optimized to improve oral bioavailability of albumin as a therapeutic protein. Several characterizations have been performed for the albumin-loaded nanoparticles (e.g. drug encapsulation efficiency, DSC, FTIR, particle size, zeta potential, morphology, release kinetics, and enzymatic stability). Nanosized spherical particles were prepared and demonstrated high stability over three months either in a powdered form or as suspensions. Sustained release of albumin over time and high enzymatic stability as compared to the free albumin were observed. In vivo, higher serum concentrations of albumin in normal rabbits and cirrhotic rats were attained following oral and intraperitoneal administrations of the albumin-loaded nanoparticles as compared to the free albumin. The nanoparticles developed in the current study might provide efficient nanovehicles for oral administration of therapeutic albumin.  相似文献   
49.
Canine and rodent leishmanial isolates from Egypt   总被引:1,自引:0,他引:1  
Two leishmanial stocks isolated in Egypt, one from a dog and the other from Rattus norvegicus, were typed according to their excreted factor (EF) serotype and the electrophoretic mobility of their glucose phosphate isomerase. The canine isolate was indistinguishable from L. donovani (= L. infantum ) strains. The rat isolate appeared to be different from L. donovani, L. tropica and L. major.  相似文献   
50.
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