全文获取类型
收费全文 | 1412篇 |
免费 | 92篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 58篇 |
妇产科学 | 18篇 |
基础医学 | 132篇 |
口腔科学 | 19篇 |
临床医学 | 213篇 |
内科学 | 349篇 |
皮肤病学 | 17篇 |
神经病学 | 107篇 |
特种医学 | 131篇 |
外科学 | 197篇 |
综合类 | 21篇 |
预防医学 | 96篇 |
眼科学 | 8篇 |
药学 | 100篇 |
肿瘤学 | 39篇 |
出版年
2021年 | 29篇 |
2020年 | 14篇 |
2019年 | 23篇 |
2018年 | 12篇 |
2017年 | 22篇 |
2016年 | 23篇 |
2015年 | 21篇 |
2014年 | 32篇 |
2013年 | 46篇 |
2012年 | 72篇 |
2011年 | 51篇 |
2010年 | 42篇 |
2009年 | 47篇 |
2008年 | 59篇 |
2007年 | 64篇 |
2006年 | 63篇 |
2005年 | 50篇 |
2004年 | 69篇 |
2003年 | 59篇 |
2002年 | 44篇 |
2001年 | 41篇 |
2000年 | 46篇 |
1999年 | 35篇 |
1998年 | 34篇 |
1997年 | 33篇 |
1996年 | 27篇 |
1995年 | 17篇 |
1994年 | 23篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 30篇 |
1988年 | 21篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 15篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 16篇 |
1974年 | 11篇 |
1973年 | 10篇 |
1972年 | 8篇 |
1970年 | 11篇 |
排序方式: 共有1514条查询结果,搜索用时 15 毫秒
1.
2.
This study examined longitudinal health and intelligence data to determine whether sensory or motor deficits account for some of the age-related intellectual changes that are commonly seen from midlife onward. Although sensory and motor functioning did not account for the age-related decrements in performance on speeded, visual perceptual tasks found for this sample in previous work, we did find that hearing deficits added error variance to performance estimates on two verbal subtests of the Wechsler scales. 相似文献
3.
4.
Objective To evaluate the use of the saphenous artery as an alternative access for endovascular procedures in the porcine model. Methods Fourteen adult pigs (25-35kg) were used in this study, 3 pigs from an acute study and 11 from chronic studies. A 2-3 cm incision was made and a saphenous artery cutdown was performed in 24 sides. Micropunc ture sets (Boston Scientific) or 18 G puncture needles were used to access the artery. Different sizes of introducers (4-7F) were used to establish endovascular access. Angiographic catheters were then used to confirm if the access was usable. Four saphenous arteries were explanted in the pigs from a chronic study 4 to 28 days after surgical procedure. Results The saphenous artery was very easy to expose and 4-5 F introducer sheaths were able to be inserted to establish access for endovascular procedures in the pigs. The saphenous artery was unable to accomodate an introducer with a size larger than 6 F. Four saphenous arteries were injured when 5 and 6 F introducers were used, but angiographic procedures could still be performed. Morphologic evaluation of the explanted arteries demonstrated occlusion of the saphenous arteries without injury or disruption of the adjacent femoral arteries. Conclusion The saphenous artery can be used as an access site in pigs for angiographic and interventional procedures if the catheter size is less than 6 F. This vessel is easier to access and can preserve the femoral artery for repeat procedures in the future. 相似文献
5.
ALBERTO Q FARIAS LUCIANA L GONÇALVES EDUARDO LR CANÇADO ANTONIO C SEGURO SILVIA B CAMPOS CLARICE P ABRANTES-LEMOS FLAIR J CARRILHO 《Journal of gastroenterology and hepatology》2006,20(1):147-152
Background and Aims: Primary biliary cirrhosis (PBC) might be complicated by osteoporosis, whose etiology remains unknown but seems to be multifactorial. Prevalence rates of 30% to 60% for distal renal tubular acidosis (DRTA) have been reported in PBC patients, generally as incomplete DRTA. Although it is undisputed that a reduced bone mineral density (BMD) is the expected outcome among patients who have been suffering from longstanding chronic metabolic acidosis, it is unclear if incomplete DRTA is also associated with metabolic bone disease in PBC patients. The present study was undertaken to compare the BMD of PBC patients with and without DRTA.
Methods: The BMD of 23 PBC patients (11 with DRTA and 12 without), all with normal clearance of creatinine, was assessed by dual energy radiograph absorptiometry. The diagnosis of DRTA was made if the urine pH was above 5.4 in all samples after the oral acid overload, showing tubular inability to acidify urine in the presence of test-induced systemic metabolic acidosis.
Results: Densitometric signs of osteoporosis were found in 82% of DRTA cases and in 83% of patients without DRTA (difference not significant). There were no significant differences in BMD measurement, T and Z scores of patients with and without DRTA.
Conclusions: The present study could not support a correlation between the presence of DRTA and the bone loss observed in PBC patients. 相似文献
Methods: The BMD of 23 PBC patients (11 with DRTA and 12 without), all with normal clearance of creatinine, was assessed by dual energy radiograph absorptiometry. The diagnosis of DRTA was made if the urine pH was above 5.4 in all samples after the oral acid overload, showing tubular inability to acidify urine in the presence of test-induced systemic metabolic acidosis.
Results: Densitometric signs of osteoporosis were found in 82% of DRTA cases and in 83% of patients without DRTA (difference not significant). There were no significant differences in BMD measurement, T and Z scores of patients with and without DRTA.
Conclusions: The present study could not support a correlation between the presence of DRTA and the bone loss observed in PBC patients. 相似文献
6.
7.
8.
Prior studies have shown that pneumothorax is one of the more difficult entities to diagnose with digitized radiography. This study was designed to test whether increasing resolution from 1.25 to 2.5 line pairs per millimeter (lp/mm) and image processing (edge enhancement from unsharp masking) would increase accuracy and confidence in the diagnosis of pneumothorax, as well as normal cases and other forms of lung disease. Conventional radiographs were digitized with use of a laser reader and then reformatted as film hard copy. Eleven observers read 35 cases reformatted in three different ways (1.25 lp/mm, 2.5 lp/mm, 1.25 lp/mm unsharp mask). The images with finer resolution (2.5 lp/mm) and unsharp mask images were superior to those with coarser resolution (1.25 lp/mm) for the diagnosis of pneumothorax. There was no difference in diagnostic accuracy for normal patients. For abnormalities other than pneumothorax, the unsharp mask images were significantly worse. Confidence in the diagnosis of pneumothorax and other abnormalities was highest with the finest resolution (2.5 lp/mm). 相似文献
9.
10.
MGC Hendriks P Dogterom JT Ebels B Oosterhuis LR Geertsema T Hulot G Bianchetti and JHG Jonkman 《Fundamental & clinical pharmacology》1998,12(5):559-565
Summary— In the present study we have compared the steady state biopharmaceutic characteristics of four diltiazem once daily controlled release capsules: Mono-Tildiem LP 300® (300 mg), Adizem® XL (300 mg)1, Cardizem® (300 mg) and Dilacor® (240 mg). Sixteen healthy male volunteers (aged 22.9 ± 3.3 years, range 19–31 years) completed an open label, multiple oral dose, randomized, four-period crossover study without a washout period in between. The volunteers received each diltiazem formulation once daily for four days. Trough diltiazem and metabolites plasma concentrations were determined on days 3 and 4. The 24-h plasma concentration-time profiles were assessed after the dose on day 4 of each period. The following steady state pharmacokinetic parameters for diltiazem were calculated: the minimum plasma concentration (cmin), the maximum plasma concentration (cmax), the time to reach that concentration (tmax), the time interval during which the plasma concentration exceeds 50% of cmax (t50), the area under the plasma concentration-time curve (AUC72–96) and the peak-to-trough fluctuation (PTF). For the metabolites of diltiazem, N-mono-desmethyl-diltiazem (NDM) and desacetyldiltiazem (DAD), AUC72–96 (AUCNDM and AUCDAD) and the ratio metabolite/parent compound were calculated. Steady state was achieved on day 3. Except one, all controlled release formulations have satisfactory controlled release properties allowing once daily administration. However, significant (P < 0.05) differences were found between the pharmacokinetic characteristics which do not allow exchange of the various formulations. Concentrations well below 50 ng·mL-1 in the morning hours were observed for Dilacor® (240 mg) and Adizem® XL (300 mg), which could be a disadvantage of these formulations as it is well-known that ischaemic events occur at a higher rate during that part of the day. The plasma concentration profiles of NDM and DAD, the major circulating metabolites, parallel the plasma concentration profiles for the parent compound. From a clinical point of view, all treatments were well tolerated. 相似文献