全文获取类型
收费全文 | 31638篇 |
免费 | 1808篇 |
国内免费 | 151篇 |
专业分类
耳鼻咽喉 | 292篇 |
儿科学 | 422篇 |
妇产科学 | 343篇 |
基础医学 | 4228篇 |
口腔科学 | 979篇 |
临床医学 | 2071篇 |
内科学 | 7577篇 |
皮肤病学 | 845篇 |
神经病学 | 2192篇 |
特种医学 | 1256篇 |
外科学 | 5544篇 |
综合类 | 157篇 |
一般理论 | 1篇 |
预防医学 | 999篇 |
眼科学 | 642篇 |
药学 | 2439篇 |
中国医学 | 44篇 |
肿瘤学 | 3566篇 |
出版年
2023年 | 140篇 |
2022年 | 309篇 |
2021年 | 539篇 |
2020年 | 324篇 |
2019年 | 397篇 |
2018年 | 515篇 |
2017年 | 474篇 |
2016年 | 504篇 |
2015年 | 545篇 |
2014年 | 711篇 |
2013年 | 902篇 |
2012年 | 1335篇 |
2011年 | 1469篇 |
2010年 | 854篇 |
2009年 | 780篇 |
2008年 | 1307篇 |
2007年 | 1305篇 |
2006年 | 1338篇 |
2005年 | 1423篇 |
2004年 | 1322篇 |
2003年 | 1338篇 |
2002年 | 1260篇 |
2001年 | 1289篇 |
2000年 | 1325篇 |
1999年 | 1195篇 |
1998年 | 393篇 |
1997年 | 334篇 |
1996年 | 300篇 |
1995年 | 279篇 |
1994年 | 244篇 |
1993年 | 237篇 |
1992年 | 819篇 |
1991年 | 723篇 |
1990年 | 732篇 |
1989年 | 698篇 |
1988年 | 711篇 |
1987年 | 622篇 |
1986年 | 614篇 |
1985年 | 597篇 |
1984年 | 391篇 |
1983年 | 323篇 |
1982年 | 148篇 |
1979年 | 319篇 |
1978年 | 204篇 |
1977年 | 151篇 |
1975年 | 149篇 |
1974年 | 213篇 |
1973年 | 151篇 |
1972年 | 165篇 |
1971年 | 147篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
In 6 cases, we have performed polytetrafluoroethylene (PTFE) graft replacement in the descending thoracic aorta, with all patients alive and showing good results. Fifty months have passed since the first graft replacement, but no complications due to the PTFE graft have occurred. 相似文献
102.
Three-dimensional architecture of elastic tissue in athero-arteriosclerotic lesions of the rat aorta
The overall three-dimensional architecture of elastic tissue in athero-arteriosclerotic lesions of the ascending aorta of the rat was studied, using scanning electron microscopy (SEM), after hot-formic acid extraction followed by a freeze-drying method. The lesions were induced by feeding the rats a diet containing 2% cholesterol for 6 weeks and administering massive doses of vitamin D2 for the first 4 days. SEM revealed the synthesis of elastins mainly in the intima and the degradation in the internal elastic lamina (IEL) and medial concentric elastic lamellae. Intimal elastic elements involved in atherosclerotic lesions were composed of an intricately tangled network of fibrous elastins or a row of elastic laminae that surrounded many rectangular compartments, which were separated by fenestrated septum-like elastins and were assumed to be the sites of smooth-muscle-cell proliferation. These observations indicated remodelling of the elastic laminae in the intima. Degradation in the IEL and media was attributed to either vitamin D2 intoxication, which was characterized by the formation of a large degraded portion, or an enhanced elastolytic process. These alterations of elastic elements probably reflect the exact frame of the modes of migration of aortic smooth muscle cells in the development of athero-arteriosclerotic lesions, thereby indicating the role of smooth muscle cells in the progress of atherosclerosis. 相似文献
103.
K. Nakamura T. Saito T. Nishiwaki K. Ueno M. Nashimoto Y. Okuda Y. Tsuchiya R. Oshiki K. Muto M. Yamamoto 《Osteoporosis international》2006,17(8):1202-1207
Introduction A few epidemiologic studies have comprehensively attempted to identify risk factors for low bone mineral density (BMD) in elderly Asian women. The purpose of this study was to identify demographic, lifestyle, and biochemical factors correlated with BMD in elderly Japanese women 69 years of age and over.Methods The study design was cross-sectional. The subjects were 583 ambulatory women aged 69 years and over, and their average age was 74.3 (SD 4.4) years. Predictor variables were age, reproductive history, anthropometric indices, grip strength, calcium intake, lifestyle information, and serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D (1,25(OH)2D), osteocalcin (OC), and undercarboxylated osteocalcin (ucOC) values. The outcome variable was forearm BMD measured with a DTX-200 osteometer.Results Simple linear regression analyses showed that BMD was significantly positively associated with body height, weight, body mass index, grip strength, serum albumin concentration, and “housework,” and negatively associated with age, years since menopause, age at menarche, number of children, serum 1,25(OH)2D concentration, serum OC concentration, and ucOC concentration. The stepwise multiple regression analysis showed that weight (β=0.00316, SE=0.00028, R2=0.180), age (β=−0.00321, SE=0.00050, R2=0.108), log-transformed serum OC (β=−0.0445, SE=0.0064, R2=0.053), log-transformed serum 1,25(OH)2D (β=−0.0401, SE=0.0074, R2=0.050), “farmwork” (β=0.00904, SE=0.00426, R2=0.005), and serum 25(OH)D concentration (β=0.000281, SE=0.000120, R2=0.003) were significantly associated with BMD.Conclusion It was concluded that body weight is a major predictor of forearm BMD among the factors measured in this study in independent Japanese women 69 years of age and over and that serum 1,25(OH)2D concentration may be associated with cortical BMD. Maintenance of body weight is very important for maintaining BMD in this population, unless a large weight aggravates obesity-related diseases. A follow-up study is needed to confirm these findings. 相似文献
104.
Shigeyuki Takatsuka Kan Yoshida Koichiro Ueki Kohei Marukawa Kiyomasa Nakagawa Etsuhide Yamamoto 《Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics》2005,99(5):614-621
OBJECTIVE: The purpose of this study was to elucidate causal relationship between disc and condyle range of movement and clinical signs and symptoms in patients with temporomandibular disorders (TMD), using magnetic resonance imaging (MRI). STUDY DESIGN: The subjects comprised of a study group of 191 patients with TMD and a control group of 43 asymptomatic patients. The clinical assessment consisted of range of maximum mouth opening (MMO) and preauricular pain during mandibular function. After clinical and radiographic findings assessment, disc and condyle condition were examined by MRI and the range of movement was accordingly classified. RESULTS: Disc displacement was observed in 156/191 (81.7%) of the study group and 9/43 (20.9%) of the control group. When disc and condyle mobility was presented around the eminence, wider MMO range was maintained, P < .05. Presence of osteoarthrosis (OA) was not correlated with preauricular pain, because OA variables were mild in the study group. CONCLUSION: Maintenance of disc/condyle translation is an important factor in TMJ function, irrespective of disc displacement or arthritis. 相似文献
105.
We studied the effect of systemic hypoxia on intraretinal pH in the intact cat eye using double-barreled H(+)-sensitive microelectrodes. Hypoxia in the dark further acidified the extracellular space surrounding rods in the distal retina and this effect was maximal in the outer nuclear layer (ONL). An acidification occurred in response to essentially any decrease in PaO2 below the normoxic level. Light-evoked alkalinizations in the ONL were larger in amplitude during hypoxia than in normoxia and this difference increased with the severity of hypoxia. Background illumination suppressed the hypoxic acidification of the ONL, completely inhibiting it at rod saturating intensities, at levels of hypoxia down to PaO2s of 40 mmHg. Systemic hyperoxia produced a small alkalinization in the ONL, and a reduction in the amplitude of the light-evoked alkalinizations. This suggests that systemic hyperoxia can partially suppress the ongoing glycolysis of dark-adapted rods. Changes in blood flow during hypoxia also altered intraretinal pH. Hypoxia led to an alkalinization in the choroid in both dark and light adaptation that spread into the distal retina. This alkalinization is most likely caused by the increase in CO2 removal that occurs as systemic blood pressure, and as a consequence, choriocapillaris blood flow increase during hypoxia. The alkalinization attenuated the acidification that was observed outside rods during hypoxia. There was also an alkalinization of the proximal portion of the retina, which spread into the vitreous. This alkalinization was attributed to the autoregulatory increase in blood flow that occurs in the retinal vessels during hypoxia. These findings provide further evidence for the hypothesis that the energy metabolism of dark-adapted rods is exquisitely sensitive to systemic hypoxia so that any small decrease in PaO2 increases rod glycolysis. Rod-saturating illumination can completely suppress this increase in glycolysis for all but severe hypoxia. An increase in blood flow in the choriocapillaris during hypoxia appears to mitigate the effects of hypoxia on the distal retina. 相似文献
106.
107.
A case-control study of breast cancer among Japanese women: with special reference to family history and reproductive and dietary factors 总被引:8,自引:0,他引:8
Dr. Ikuko Kato Dr. Shigeto Miura Fijio Kasumi Takuji Iwase Hideya Tashiro Yoshihiro Fujita Hiroki Koyama Tadashi Ikeda Kiyoshi Fujiwara Keiichi Saotome Kazuaki Asaishi Rikiya Abe Mitsuhiro Nihei Tsunehiro Ishida Takao Yokoe Hiroshi Yamamoto Motoi Murata 《Breast cancer research and treatment》1992,24(1):51-59
Summary To study the effects of family history and reproductive, anthropometric, and dietary factors on the risk of breast cancer among low risk populations, we conducted a hospital-based case-control study involving 908 patients with breast cancer and their matched controls, in Japan. A positive family history of breast cancer significantly increased the risk of breast cancer (odds ratio = 1.52, 95% confidence interval: 1.14–2.03). The risk further increased with increasing number of family members affected. Obesity, single marital status, fewer births, a late childbirth, and less consumption of green-yellow vegetables and dairy products were also associated with an increased risk of breast cancer. These associations were independent in multivariate analyses. There was no increase in risk associated with consumption of high fat foods. When analyzed by menopausal status, the association with family history of breast cancer, especially in the first degree of relatives, was more evident for premenopausal breast cancer. The associations with obesity and lower consumption of dairy products were more pronounced for postmenopausal breast cancer, while those with lower parity and single marital status were stronger for premenopausal breast cancer. 相似文献
108.
The cutaneous thermal-cooling and -warming detection thresholds were evaluated on the dorsal side of the right distal forearm and on the dorsum of the right foot in 134 normal subjects (66 men and 68 women) without sensory symptoms and signs, aged from 11 to 87 years by using a Thermal Threshold Tester (Vickers Medical International, England). The normative data for the clinical evaluation of the severity and the pathologic process of the sensory disturbance of the patients were obtained. The data obtained included 1) the mean of each threshold and 2) its upper limit value of 95% confidence interval for each decade. The mean of each threshold was significantly increased with aging (P less than 0.0001). Therefore, the cutaneous thermal-cooling and -warming detection thresholds of the patients with sensory disturbances should be compared with the normative data adjusted for the age of each subject obtained in this study. Based on the evaluation, repeated six times for three weeks, of each threshold of six volunteers (ages from 21 to 66), high reliability of each threshold (intraclass correlation coefficient from 0.78 to 0.96) was observed. 相似文献
109.
S Kasai M Sawa S Hirai Y Nishida K Onodera T Yamamoto M Mito 《Transplantation proceedings》1992,24(6):2990-2992
110.
During a 12-month period ending on November 30, 1988, data on 133 pediatric patients visiting a pediatric emergency department with water-related injuries were collected. Of these patients, 70% were male. There were 13 submersions, seven cases of head trauma, three cases of neck trauma, 88 cases of external injury, and 34 other injuries. Incidents took place at beaches (75%) in public pools (12%), in friends' pools (4%), and in home pools (4%). Eighty-six percent of the cohort knew how to swim. Swimming, playing, and surfing activity accounted for most of the injuries. Measures for prevention are described. 相似文献