全文获取类型
收费全文 | 1948篇 |
免费 | 171篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 7篇 |
儿科学 | 101篇 |
妇产科学 | 54篇 |
基础医学 | 307篇 |
口腔科学 | 29篇 |
临床医学 | 245篇 |
内科学 | 332篇 |
皮肤病学 | 62篇 |
神经病学 | 206篇 |
特种医学 | 31篇 |
外科学 | 194篇 |
综合类 | 31篇 |
一般理论 | 2篇 |
预防医学 | 234篇 |
眼科学 | 13篇 |
药学 | 131篇 |
中国医学 | 3篇 |
肿瘤学 | 150篇 |
出版年
2023年 | 9篇 |
2022年 | 27篇 |
2021年 | 39篇 |
2020年 | 29篇 |
2019年 | 54篇 |
2018年 | 57篇 |
2017年 | 47篇 |
2016年 | 46篇 |
2015年 | 55篇 |
2014年 | 78篇 |
2013年 | 112篇 |
2012年 | 148篇 |
2011年 | 156篇 |
2010年 | 77篇 |
2009年 | 67篇 |
2008年 | 83篇 |
2007年 | 123篇 |
2006年 | 104篇 |
2005年 | 104篇 |
2004年 | 99篇 |
2003年 | 74篇 |
2002年 | 85篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 21篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 18篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 20篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 16篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 7篇 |
1980年 | 19篇 |
1978年 | 10篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1971年 | 10篇 |
1965年 | 7篇 |
1937年 | 6篇 |
排序方式: 共有2132条查询结果,搜索用时 15 毫秒
1.
2.
Patricia K P Burnell Lars Asking Lars Borgstr?m Steve C Nichols Bo Olsson David Prime Ian Shrubb 《Journal of aerosol medicine》2007,20(3):269-281
Magnetic resonance imaging (MRI) of the oropharyngeal region from 20 adult volunteers using four model inhalation devices (varying mouthpiece diameters, airflow resistances) and tidal breathing was carried out. Statistical analysis (convex hull method) selected 12 scans from 80 data sets representing the extremes of all dimensions in the population. Twelve physical mouth-throat models were made by stereolithography using the exact scan data. The aim was to produce models with varying dimensions to span the adult population, and to investigate if oropharyngeal dimensions affected throat retention for different delivery systems. In an in vitro analysis, the models were used to determine the retention effect of the oropharyngeal airspaces when drug aerosols were administered from four inhalation delivery systems: a pressurised metered dose inhaler (pMDI), two different dry powder inhalers (DPIs A and B), and a nebulizer. The aims of this work were to determine the key parameters governing mouth-throat retention and whether retention was dependent on the delivery system used. Characterizing the throat models by measuring 51 different dimensional variables enabled determination of the most influential variables for dose retention for each inhalation delivery system. Throat model retention was found to be dependent on the delivery system (pMDI approximately DPI(A) > DPI(B) > Neb.). The most influential variable was the total throat model volume. Throat models representing high, median, and low oropharyngeal filtration in healthy adults have been identified. 相似文献
3.
Fix Joseph A. Alexander Jose Cortese Margot Engle Karen Leppert Paula Repta A. J. 《Pharmaceutical research》1990,7(4):384-387
Short-chain alkyl esters of L-dopa were administered to rats and mice via oral and rectal routes. Plasma L-dopa esters and L-dopa were determined in the systemic and portal circulation by HPLC. A comparison of isopropyl, butyl, and 4-hydroxybutyl esters of L-dopa demonstrated significantly higher levels of the esters in both systemic and portal blood samples following rectal administration than following oral administration. In most cases, oral administration resulted in nondetectable (<0.01 µg/ml) levels of the esters in plasma. Correspondingly, the plasma levels of L-dopa itself were consistently higher following rectal administration. At very high oral doses (500 mg L-dopa equivalents/kg body weight), systemic plasma levels of the butyl ester could be detected (1.25 µg/ml at 10 min), which might indicate saturation of the esterase activity of the small intestine. These studies indicate that the systemic availability of L-dopa from short-chain alkyl esters of L-dopa may be best optimized by rectal administration, which avoids the relatively high esterase activity characteristic of the small intestine. 相似文献
4.
5.
Image fusion of bone SPECT and CT - a specific diagnostic method in oral and maxillofacial surgery] 总被引:1,自引:0,他引:1
Denys John Loeffelbein Marco Rainer Kesting Eckhart Mielke Margot Jonas Frank H?lzle Klaus-Dietrich Wolff 《Mund-, Kiefer- und Gesichtschirurgie》2007,11(1):33-41
OBJECTIVE: The aim of this study was to evaluate the benefit of image fusion of CT (computertomography) and bone SPECT (single photon emission computed tomography) in diagnosis of head and neck cancer. METHODS AND PATIENTS: Computer based image fusion has been applied in 39 patients with suspected cancer in the oromaxillofacial region following CT and SPECT without any further hazard for the patients. Afterwards image fusion was set in comparision to simultaneously evaluation of CT and SPECT and histological findings. RESULTS: In 5 out of 39 patients SPECT/CT image fusion obtained more precise anatomical findings in tumour expansion than simultaneously evaluation of CT and SPECT. CONCLUSION: For planning of surgical and radiation therapy of oral and maxillofacial cancer, image fusion of CT/SPECT provides efficient and plastical diagnostic imaging. Particularly in complex anatomical regions like maxilla or base of the skull image fusion could be an additional device, if simultaneous evaluation of CT and SPECT is not clear. 相似文献
6.
Chronic food restriction has been shown to enhance glucose metabolism in adipocytes from lean Zucker rats at 10, 26, and 52 weeks of age compared to ad libitum-fed lean rats. Only adipocytes from food restricted 10-week-old obese rats demonstrated this response. In this study, lean and obese rats were food restricted from 5 until 14 weeks of age to determine the age at which adipocytes from obese rats were no longer affected by this intervention. Effects of 1 week of refeeding were also determined. When the rats were killed, body weights were highest in control rats followed by restricted/refed and then restricted rats within each genotype. Epididymal pad weights of lean rats were resistant to dietary intervention, while those of obese-restricted and obese-restricted/refed rats weighed less than pads of obese-control rats. Retroperitoneal pad weight was lowered by food restriction in both genotypes; but only that of lean-restricted/refed rats totally recovered with refeeding. Adipocytes of lean-restricted rats had the highest conversion of glucose to CO2. Glyceride-glycerol production was higher in obese compared to lean rats, but restricted rats had elevated conversion of glucose to fatty acids. In general, these results indicate that by 14 weeks of age obese Zucker rats no longer respond to food restriction with an elevated rate of glucose metabolism in adipocytes. 相似文献
7.
8.
We present the findings of a pilot study to assess the perception of risk in 155 women with a family history of breast cancer by questionnaire. Only 11% of women were able to identify the correct population risk and more than half were unable to assess their own lifetime risk within 50% of the clinicians'' estimate. Although it is probable that women are helped by genetic counselling and if at substantial risk, annual mammography, the psychological impact of assigning true risk and the value of mammography need to be evaluated. 相似文献
9.
Anionic oligomerization of methacrylic esters (methyl (MMA), ethyl (EMA), butyl (n-BMA), tert-butyl (t-BMA) methacrylates) was conducted in a one-step process by mixing, in tetrahydrofuran, the monomer, an alkali metal (sodium) and a deactivating agent (sulfur or tert-butyl alcohol). The formation of alcohol due to a nucleophilic attack of the ester group by the methacrylic carbanion was quantified and related to the monomer structure, temperature and nature of the living ends. It was shown that this side reaction is not limited to the propagation step but can occur during the initiation step. From mass spectra and nuclear magnetic resonance (NMR) spectroscopy of the protonated oligomers (tert-butyl alcohol as deactivating agent), it was concluded that this side reaction led to five-membered cyclic β-keto esters during the initiation step of MMA, EMA and n-BMA monomers only. This implies an intramolecular reaction between one carbanion of the dianionic dimer and the penultimate ester group. It was found that this reaction involves primarily dianionic tail-to-tail dimer, even though head-to-tail dimer was also formed. 相似文献
10.
Mark Hazekamp Francisco Portela Margot Bartelings 《European journal of cardio-thoracic surgery》2007,31(5):879-887
OBJECTIVE: To describe the optimal surgical strategy in heart specimens with transposition of the great arteries (TGA) and left ventricular outflow tract obstruction (LVOTO). METHODS: Thirty-three specimens with LVOTO were selected: TGA with intact ventricular septum (TGA/IVS) (10), TGA/VSD (21), and Taussig-Bing (2). RESULTS: LVOTO in TGA/IVS consisted of combinations of bicuspid pulmonary valve (four), subpulmonary fibrous ridge (four), obstructive muscular conus (two) and bulging muscular septum (four). Arterial switch operation (ASO) with LVOTO resection/valvotomy was feasible in nine hearts. Obstructive anterior papillary muscle prohibited LVOTO relief in one specimen. In TGA/VSD and Taussig-Bing LVOTO consisted of combinations of bicuspid (nine) or unicommissural (one) pulmonary valve, fibrous ridge (three), obstructive muscular conus (five), malaligned outlet septum (six), accessory mitral valve tissue (two), straddling mitral valve (two) and anterior mitral valve rotation (four). VSDs were subpulmonary in 13 (9 perimembranous, 4 muscular), subaortic in 3 (2 perimembranous, 1 anterior muscular), doubly committed in 2, inlet in 3 (2 perimembranous, 1 muscular), non-committed and anterior in 1, and finally 1 VSD extended both into inlet and subpulmonary outlet septum. LVOTO resection and ASO with VSD closure was possible in 10. In six specimens, both a Rastelli and a Nikaidoh operation were feasible. For two hearts, a Nikaidoh procedure was the only option, while Rastelli was considered optimal in another specimen. Mitral valve anomalies prevented LVOTO relief in four, only permitting for Senning/VSD closure (one) or univentricular palliation (three). CONCLUSIONS: LVOTO resection and pulmonary valvotomy frequently permits an ASO. Inlet VSD, impossibility of VSD enlargement, straddling mitral valve, distant aorta and small right ventricle make the Nikaidoh procedure the best option. Mitral anomalies preventing LVOTO relief can make biventricular repair impossible. 相似文献