全文获取类型
收费全文 | 2199篇 |
免费 | 161篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 4篇 |
儿科学 | 49篇 |
妇产科学 | 27篇 |
基础医学 | 248篇 |
口腔科学 | 50篇 |
临床医学 | 309篇 |
内科学 | 467篇 |
皮肤病学 | 22篇 |
神经病学 | 145篇 |
特种医学 | 372篇 |
外科学 | 235篇 |
综合类 | 46篇 |
预防医学 | 171篇 |
眼科学 | 20篇 |
药学 | 104篇 |
中国医学 | 1篇 |
肿瘤学 | 110篇 |
出版年
2021年 | 33篇 |
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 29篇 |
2017年 | 27篇 |
2016年 | 27篇 |
2015年 | 30篇 |
2014年 | 56篇 |
2013年 | 64篇 |
2012年 | 88篇 |
2011年 | 88篇 |
2010年 | 48篇 |
2009年 | 84篇 |
2008年 | 73篇 |
2007年 | 75篇 |
2006年 | 56篇 |
2005年 | 70篇 |
2004年 | 53篇 |
2003年 | 71篇 |
2002年 | 59篇 |
2001年 | 56篇 |
2000年 | 54篇 |
1999年 | 52篇 |
1998年 | 54篇 |
1997年 | 52篇 |
1996年 | 45篇 |
1995年 | 46篇 |
1994年 | 36篇 |
1993年 | 38篇 |
1992年 | 49篇 |
1991年 | 49篇 |
1990年 | 49篇 |
1989年 | 70篇 |
1988年 | 60篇 |
1987年 | 60篇 |
1986年 | 50篇 |
1985年 | 52篇 |
1984年 | 30篇 |
1983年 | 28篇 |
1982年 | 35篇 |
1981年 | 22篇 |
1980年 | 31篇 |
1979年 | 19篇 |
1978年 | 25篇 |
1977年 | 29篇 |
1976年 | 24篇 |
1975年 | 17篇 |
1974年 | 16篇 |
1970年 | 14篇 |
1969年 | 19篇 |
排序方式: 共有2380条查询结果,搜索用时 46 毫秒
1.
2.
Coronary artery bypass grafts: visualization with MR imaging 总被引:1,自引:0,他引:1
3.
Hysterosalpingography was performed in 31 patients by means of a low-dose scanning-beam digital radiographic system. The technique permits adequate evaluation of gynecologic abnormalities while allowing significant reduction in radiation: 2.4-mR (6.1 X 10(-7) C/kg) exposure to the skin and 0.7-mrad (7 X 10(-6) Gy) mean dose to the ovaries per image obtained. Sixteen patients demonstrated readily recognizable and documented abnormalities, corroborated by laparoscopy, laparotomy, or other supportive evidence. 相似文献
4.
Huang Guo-Shu MD Chang Wei-Chou MD Lee Herng-Sheng MD † Taylor John A. M. DC DACBR ‡ Cheng Tiang-Yeu MD § Chen Cheng-Yu MD 《Dermatologic surgery》2005,31(6):717-719
BACKGROUND: Merkel cell carcinoma is a rare malignant neuroendocrine neoplasm characteristically arising from the dermis of sunlight-exposed skin. It rarely arises outside the skin. OBJECTIVE: We present a patient with primary Merkel cell carcinoma arising from subcutaneous fat, with no involvement of the overlying skin. We describe the clinical manifestations and magnetic resonance imaging (MRI) findings. METHODS: We report a 63-year-old woman with a primary lesion of Merkel cell carcinoma that arose from the subcutaneous fat layer of the left arm. The lesion presented as a subcutaneous nodule with intact overlying skin. MRI showed that the nodular lesion was located entirely in the subcutaneous fat layer, with no involvement of the dermis. Peritumoral infiltration around the lesion and enlarged lymph nodes deep to the lesion were noted. The patient received wide excision of the lesion with dissection of the regional lymph nodes and adjuvant radiotherapy and chemotherapy. RESULTS: Histopathologic examination confirmed the diagnosis of Merkel cell carcinoma with local lymphatic metastasis, and the lesion was completely located in the subcutaneous fat, with no involvement of the dermis. These findings were well correlated with MRI findings. CONCLUSION: Primary Merkel cell carcinoma may arise from the subcutaneous fat and present as an entirely subcutaneous lesion with intact skin. MRI is helpful to evaluate the local extension of the lesion and regional lymphatic metastasis. 相似文献
5.
Effect of 2 ppm ozone exposure on rat lung lipid fatty acids 总被引:1,自引:0,他引:1
Based on in vitro studies, the initial damage to lung cells by ozone exposure is believed to result in part from the breakdown of lipid polyunsaturated fatty acids to aldehydes, ozonides, and peroxides. The present study measured lipid breakdown products in lungs isolated from rats pretreated with [1-14C]acetate 12 h before exposure for 4 h to either air or 2 ppm ozone. Lipid fatty acid breakdown was indicated by a 112% increase in thiobarbituric acid-reactive substances on ozone exposure and by changes in chemical and radioactive measurements of mono- and dicarboxylic acids formed by treatment of lipid fractions with hydrogen peroxide. Ozone exposure resulted in a 63% increase in recovery of short-chain fatty acids accounted for by increased recoveries of malonic acid by 37%, hexanoic acid by 47%, nonanoic acid by 118%, and azelaic acid by 107%. Recovery of glutaric acid was enhanced 15-fold by ozone exposure. Although decreases in tissue arachidonic acid could not be detected, oleic acid was significantly decreased by 36%. Recovery of radiolabel as short-chain fatty acids was increased by 65% on ozone exposure and was mainly accounted for by enhanced labeling of nonanoic and glutaric acid fractions. The failure to observe significant increases in 14C recovery in the other fractions suggested ozone-induced breakdown of unlabeled fatty acids. These results demonstrate the cleavage of unsaturated fatty acid double bonds following in vivo exposure of lungs to ozone. Breakdown of arachidonic and oleic acids was specifically identified by increased recoveries of glutaric and nonanoic acids, respectively. 相似文献
6.
表小檗碱对α受体的作用 总被引:2,自引:0,他引:2
表小檗碱(epiberberine,EB)是从湖北产黄连(Coptis chinensis Franch)中提取的一种生物碱,属苯喹嗪类原小檗碱,对其药理作用的研究资料甚少,未见其对α肾上腺素体作用的报道。资料表明,许多原小檗碱类化合物有α受体阻滞作用,为从该类化合物中选择 相似文献
7.
8.
The purpose of this pilot study was to observe both relaxed and deep breathing patterns in a convenience sample to determine the incidence of normal versus faulty patterns of respiration. These observations were then combined with respondent answers to a survey on pain history to determine if there is any correlation between faulty breathing and musculo-skeletal pain patterns. If such a correlation can be made, then we propose that clinicians working with chronic pain patients may have improved outcomes if they address and correct faulty breathing patterns. Based on this study, it is suggested to include the evaluation and treatment of faulty respiration in the rehabilitation of chronic musculo-skeletal conditions, most notably cervical pain. 相似文献
9.
10.
Glucose catabolism of a vascular perfused rat hemidiaphragm was determined at rest and during stimulation of the phrenic nerve with trains of either 5 (T5) or 15 (T15) pulses (20 msec intervals) per second. Tissues were perfused and bathed in HEPES-buffered medium containing 11 mM D-[U-14C, 5-3H]glucose, equilibrated with 100% O2. Resting glucose catabolism via the Emden-Meyerhof pathway was indicated by a 3H2O production rate per hemidiaphragm of 1.45 +/- 0.07 mumol/h, of which 47% was recovered as [14C]lactate with the remainder assumed to be metabolised by mitochondria. During the first 30 min of T5 and T15 stimulation, peak isometric tension declined from an initial value of 105 +/- 8 g by 54% and 79%, respectively. The resulting peak tensions of 48 and 22 g remained constant for the next 60 min. These tensions were associated with linear rates of 3H2O production of 2.93 +/- 0.41 and 2.84 +/- 0.25 mumol/h. Stimulation by T5 and T15 increased mitochondrial metabolism of glucose by 64% and 95%, respectively, with no significant alterations in lactate formation from either exogenous or endogenous sources. The results suggest that the initial decline in tension is due to fatigue of the fast anaerobic myofibers; whereas, the sustained force beyond 30 min is attributable to the mitochondrial-rich slow myofibers. 相似文献