全文获取类型
收费全文 | 1866篇 |
免费 | 135篇 |
国内免费 | 3篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 31篇 |
妇产科学 | 43篇 |
基础医学 | 304篇 |
口腔科学 | 67篇 |
临床医学 | 209篇 |
内科学 | 391篇 |
皮肤病学 | 60篇 |
神经病学 | 125篇 |
特种医学 | 18篇 |
外科学 | 156篇 |
综合类 | 24篇 |
一般理论 | 1篇 |
预防医学 | 310篇 |
眼科学 | 40篇 |
药学 | 117篇 |
中国医学 | 9篇 |
肿瘤学 | 86篇 |
出版年
2023年 | 14篇 |
2022年 | 31篇 |
2021年 | 54篇 |
2020年 | 31篇 |
2019年 | 44篇 |
2018年 | 64篇 |
2017年 | 53篇 |
2016年 | 46篇 |
2015年 | 54篇 |
2014年 | 67篇 |
2013年 | 69篇 |
2012年 | 105篇 |
2011年 | 117篇 |
2010年 | 65篇 |
2009年 | 49篇 |
2008年 | 123篇 |
2007年 | 132篇 |
2006年 | 108篇 |
2005年 | 87篇 |
2004年 | 122篇 |
2003年 | 88篇 |
2002年 | 92篇 |
2001年 | 17篇 |
2000年 | 28篇 |
1999年 | 24篇 |
1998年 | 24篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 17篇 |
1994年 | 6篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 7篇 |
1975年 | 5篇 |
1971年 | 4篇 |
1966年 | 4篇 |
1963年 | 4篇 |
1941年 | 4篇 |
1927年 | 5篇 |
排序方式: 共有2004条查询结果,搜索用时 15 毫秒
91.
The petrosal ganglion (PG) provides sensory innervation to the carotid sinus and carotid body through the carotid (sinus) nerve (CN). Application of either acetylcholine (ACh) or adenosine 5'-triphosphate (ATP) to the PG superfused in vitro activates CN fibers. Dopamine (DA) modulates the effects of ACh. We have previously shown that DA when applied to the PG modulates the effects of ACh on carotid sinus nerve fibers. We currently report the effects of DA on the ATP-induced responses in the isolated PG in vitro. While DA had no effect on the basal activity recorded from the CN, it reduced ATP-induced responses in a dose-dependent manner, when preceding ATP applications by 30 s. Our results suggest that DA-a transmitter present in a group of PG neurons and in carotid body cells-may act as an inhibitory modulator of ATP-evoked responses in PG neurons. 相似文献
92.
93.
Jensen C Holloway L Block G Spiller G Gildengorin G Gunderson E Butterfield G Marcus R 《The American journal of clinical nutrition》2002,75(6):1114-1120
BACKGROUND: Adequate intakes of calcium and vitamin D reduce bone loss and fracture risk in the elderly. Other nutrients also affect bone health, and adequate intakes may influence bone turnover and balance. OBJECTIVE: We compared the long-term effects on bone turnover markers and calciotropic hormones of a multinutrient supplement, a calcium and vitamin D supplement, and dietary instruction aimed at increasing calcium intake through foods. DESIGN: Ninety-nine healthy postmenopausal women participated in a 3-y, randomized trial, receiving either 1) supplemental calcium (1450 mg/d) and vitamin D [10 microg (400 IU)/d], 2) calcium, vitamin D, and other nutrients (multinutrient supplement), or 3) dietary instruction (dietary control group). Data are from 83 subjects who completed the trial. RESULTS: Increases over baseline in calcium intakes and serum 25-hydroxyvitamin D concentrations were sustained over 3 y in all treatment groups. Circulating parathyroid hormone concentrations were reduced at year 1 in all treatment groups but trended toward baseline thereafter. Bone turnover markers followed a similar pattern, and none of the changes in biochemical concentrations differed significantly between groups. CONCLUSIONS: All 3 interventions offer long-term feasibility for increasing calcium intake and serum 25-hydroxyvitamin D concentrations. The dietary addition of micronutrients implicated in skeletal physiology confers no obvious bone-sparing effect in healthy postmenopausal women beyond that of calcium and vitamin D alone. The attenuation over time in suppression of parathyroid hormone and bone turnover might help explain why nutrient intervention tends to have less of a bone-sparing effect than do skeletally active medications such as estrogen or bisphosphonates. 相似文献
94.
OBJECTIVES: To assess the association between maternal caffeine consumption during pregnancy and low birth weight, prematurity and intrauterine growth retardation. METHODS: A case-control was carried out and 354 newborns of single labor with birthweight <2,500 g (cases) and 354 with birthweight >3,000 g (controls) were analyzed. Caffeine consumption was calculated based on daily consumption of coffee, soft drinks and tea. Results were adjusted using multiple logistic regression for the following confounders: mother's age, schooling, income, marital status, skin color, parity, smoking, previous low birthweight children, mother's pre-pregnancy weight, employment status, interval between pregnancies, prenatal care and high blood pressure. RESULTS: For caffeine consumption <300 mg/day and >300 mg/day, the adjusted odds ratios for low birthweight were: 0.72 (95%IC=0.45-1.25) and 0.47 (95%IC=0.24-0.92); prematurity: 0.59 (95%IC=0.32-1.09) and 0.32 (95%IC=0.15-0.72); and intrauterine growth retardation: 1.16 (95%IC=0.45-3.01) and 0.64 (95%IC=0.20-1.98), respectively. CONCLUSION: There was no association between caffeine consumption during pregnancy and low birthweight, prematurity and intrauterine growth retardation. 相似文献
95.
Africa is the continent most severely affected by the global HIV-1 epidemic, with east and southern Africa in general more severely affected than west and central Africa. Differences in the spread of the epidemic can be accounted for by a complex interplay of sexual behaviour and biological factors that affect the probability of HIV-1 transmission per sex act. Sexual behaviour patterns are determined by cultural and socioeconomic contexts. In sub-Saharan Africa, some traditions and socioeconomic developments have contributed to the extensive spread of HIV-1 infection, including the subordinate position of women, impoverishment and decline of social services, rapid urbanisation and modernisation, and wars and conflicts. Populations in many parts of Africa are becoming trapped in a vicious circle as the HIV-1 epidemic leads to high mortality rates in young and economically productive age groups, and thus leads to further impoverishment. Interventions to control HIV-1 should not only target individuals, but also aim to change those aspects of cultural and socioeconomic context that increase the vulnerability to HIV-1 of people and communities. 相似文献
96.
Neuroendocrine tumors of the pancreas in von Hippel-Lindau disease: spectrum of appearances at CT and MR imaging with histopathologic comparison 总被引:7,自引:0,他引:7
Marcos HB Libutti SK Alexander HR Lubensky IA Bartlett DL Walther MM Linehan WM Glenn GM Choyke PL 《Radiology》2002,225(3):751-758
PURPOSE: To demonstrate the imaging characteristics of neuroendocrine tumors (NETs) of the pancreas in patients with von Hippel-Lindau (VHL) disease to establish diagnostic criteria. MATERIALS AND METHODS: Twenty-five patients with VHL disease and 29 surgically confirmed pancreatic NETs were included. Screening computed tomographic (CT) and/or magnetic resonance (MR) imaging findings were reviewed, and tumor number, diameter, growth rates (doubling time), location, presence of metastatic disease, and attenuation or enhancement properties were determined. RESULTS: Eighteen of 29 (62%) pancreatic NETs were smaller than 3.0 cm in diameter and enhanced homogeneously on contrast material-enhanced CT and MR images. No tumor smaller than 3.0 cm metastasized. Tumors 3.0 cm or larger (11 [38%] of 29) more often enhanced heterogeneously, and two of 11 were associated with hepatic metastases. Smaller (<3.0 cm) tumors displayed longer mean doubling times (mean, 927 vs 351 days) than did larger (> or =3.0 cm) tumors; however, there was considerable overlap. Fifteen (52%) tumors were located in the pancreatic head; eight (28%), in the tail; and six (21%), in the body. Ten (40%) patients with pancreatic NETs had associated pheochromocytomas, and 22 (88%) had no or mild pancreatic cystic disease, which is substantially more than the general population of patients with VHL disease. CONCLUSION: Pancreatic NETs in VHL have characteristic features at CT and MR imaging: Most are small, located in the pancreatic head, and enhance homogeneously. Tumors larger than 3.0 cm are prone to metastasize and enhance heterogeneously. 相似文献
97.
98.
Jorge L Alio M. Emilia Mulet Luis F. Zapata M. Teresa Vidal Victoria De Rojas Jaime Javaloy 刘敬 《美国医学会眼科杂志(中文版)》2005,17(3):182-183
目的:报告应用角膜内植入物矫正远视眼后发生角膜周边部上皮性混浊的新的并发症。设计:前瞻性观察研究。参加者:7例患者的11只眼行角膜内植入矫正远视。方法:应用显微角膜板层刀制作一个蒂在下方的角膜瓣,将角膜内移植物植入角膜基质床中。 相似文献
99.
Antioxidant supplementation decreases lipid peroxidation biomarker F(2)-isoprostanes in plasma of smokers. 总被引:5,自引:0,他引:5
Marion Dietrich Gladys Block Mark Hudes Jason D Morrow Edward P Norkus Maret G Traber Carroll E Cross Lester Packer 《Cancer epidemiology, biomarkers & prevention》2002,11(1):7-13
Free radicals in cigarette smoke (CS) cause oxidative damage to proteins, DNA, and lipids, contributing to the pathobiology of atherosclerosis, heart disease, and cancer. In vitro studies have shown that antioxidants quench free radicals and ameliorate certain aspects of biomolecular damage caused by CS. It is hypothesized that a combination of antioxidants is more effective than a single antioxidant, due to their interactions. To investigate whether supplemental antioxidants reduce CS-related lipid peroxidation in vivo and whether they are more effective in combination, we conducted an intervention study in smokers. In a randomized double-blind placebo-controlled trial, we investigated whether vitamin C or an antioxidant mixture containing vitamin C, alpha-lipoic acid, and vitamin E decreases plasma F(2)-isoprostane levels, an index of oxidant stress, in smokers. Plasma of 126 smokers (mean age, 46 years; age range, 20-78 years) was analyzed for F(2)-isoprostanes at baseline and after intervention with antioxidants and placebo. In smokers with a body mass index (BMI) above the median, 2 months of daily supplementation with 500 mg of vitamin C decreased plasma F(2)-isoprostane levels by 28.8 pmol/liter when compared with the placebo group (P = 0.001); levels in the mixture group were 7.45 pmol/liter lower after treatment, but this difference was not statistically significant (P = 0.14). There was no treatment effect in smokers with a low BMI. BMI was significantly positively associated with plasma F(2)-isoprostane levels (trend P = 0.001). Antioxidants decrease smoking-related lipid peroxidation markers of oxidative stress in humans with high BMI. Our results do not indicate that an antioxidant combination is more effective than vitamin C alone. The intake of antioxidants may help prevent smoking-related diseases. Smoking cessation should still be considered the most effective way to prevent smoking-related diseases. 相似文献