全文获取类型
收费全文 | 1541209篇 |
免费 | 119576篇 |
国内免费 | 3454篇 |
专业分类
耳鼻咽喉 | 20558篇 |
儿科学 | 51131篇 |
妇产科学 | 44160篇 |
基础医学 | 220625篇 |
口腔科学 | 42020篇 |
临床医学 | 136785篇 |
内科学 | 307358篇 |
皮肤病学 | 37025篇 |
神经病学 | 129962篇 |
特种医学 | 59490篇 |
外国民族医学 | 487篇 |
外科学 | 229922篇 |
综合类 | 33300篇 |
现状与发展 | 3篇 |
一般理论 | 525篇 |
预防医学 | 117543篇 |
眼科学 | 34353篇 |
药学 | 107873篇 |
1篇 | |
中国医学 | 3544篇 |
肿瘤学 | 87574篇 |
出版年
2021年 | 12021篇 |
2019年 | 12983篇 |
2018年 | 19281篇 |
2017年 | 14970篇 |
2016年 | 17231篇 |
2015年 | 18595篇 |
2014年 | 25385篇 |
2013年 | 38467篇 |
2012年 | 51978篇 |
2011年 | 55221篇 |
2010年 | 32243篇 |
2009年 | 29785篇 |
2008年 | 51664篇 |
2007年 | 54690篇 |
2006年 | 54949篇 |
2005年 | 53412篇 |
2004年 | 50815篇 |
2003年 | 48799篇 |
2002年 | 47232篇 |
2001年 | 77214篇 |
2000年 | 79842篇 |
1999年 | 64788篇 |
1998年 | 18322篇 |
1997年 | 16497篇 |
1996年 | 16436篇 |
1995年 | 15508篇 |
1994年 | 14084篇 |
1993年 | 13208篇 |
1992年 | 46680篇 |
1991年 | 44281篇 |
1990年 | 42243篇 |
1989年 | 40296篇 |
1988年 | 36834篇 |
1987年 | 36081篇 |
1986年 | 33472篇 |
1985年 | 32066篇 |
1984年 | 24549篇 |
1983年 | 20618篇 |
1982年 | 12828篇 |
1981年 | 11340篇 |
1979年 | 21282篇 |
1978年 | 15092篇 |
1977年 | 12622篇 |
1976年 | 11809篇 |
1975年 | 12128篇 |
1974年 | 14474篇 |
1973年 | 13956篇 |
1972年 | 13010篇 |
1971年 | 11865篇 |
1970年 | 11278篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
A 68-year-old man developed pandysautonomia with severe orthostatic dysfunction, fixed heart rate, low serum levels of norepinephrine and epinephrine, absent sympathetic skin responses, and pupillary abnormalities. CSF protein was 92 mg/dl. In spite of a good recovery following corticosteroid administration, a relapse occurred, with accompanying sensory symptoms confined to both arms. Fatal sudden cardiac arrest occurred after 4 months. Autopsy revealed numerous lymphocytic infiltrates, predominantly in autonomic and sensory ganglia and, to a lesser extent, in the nerve roots, spinal cord, and brainstem without evidence for an underlying tumor. This case provides histopathologic evidence for an inflammatory etiology of panautonomic neuropathy in some patients. 相似文献
902.
A C Da Rosa B Kemp T Paiva F H Lopes da Silva H A Kamphuisen 《Electroencephalography and clinical neurophysiology》1991,78(1):71-79
A model of sleep phasic events such as vertex waves, K complexes, delta waves and sleep spindles is proposed. It consists of feedback loops that are driven by white noise (simulating tonic delta and sigma activity) and by isolated random impulses, simulating vertex waves or K complexes, depending on the background tonic activity. A model-based method for the detection of sleep phasic events was implemented in a personal computer. Its performance was investigated using simulated and real whole-night EEG signals. The method was able to detect K complexes and vertex waves in a reliable way in spite of their variable shapes and in the presence of a variety of background activities. The detector appears to have superior performance to those so far reported in the literature. The performance of the detector was also compared to that of an electroencephalographer using normal sleep EEG records of 8 h duration from 6 subjects. The performance was satisfactory both in terms of accuracy and reliability. The problem of detecting K complexes in stages 3 and 4 of sleep is discussed. 相似文献
903.
904.
N A Zakhari M I Walash M S Rizk S S Toubar C J Brooks W J Cole 《Journal of pharmaceutical and biomedical analysis》1991,9(9):705-709
A simple gas chromatographic procedure has been developed for the determination of methyltestosterone in bulk powders and in tablets. Two new silyl ether derivatives of methyltestosterone have been prepared using dimethylethylsilylimidazole (DMESI) and dimethylisopropylsilylimidazole (DMiPSI). The method is accurate and selective for methyltestosterone within the concentration range 0.1-1.5 micrograms microliters-1. 相似文献
905.
C. Dezutter-Dambuyant 《Toxicology in vitro》1991,5(5-6):585-589
Langerhans cells are an essential component of cutaneous immunological defence mechanisms. They are mononuclear dendritic cells derived from bone marrow, which are present in the squamous epithelia, particularly skin. Langerhans cells show marked changes in phenotype and function when epidermal cell suspensions are prepared according to a trypsinization protocol and placed in culture for 1–3 days. They seem to mature and acquire most of the features of lymphoid dendritic cells, especially the interdigitating dendritic cells present in lymph nodes. This observation supports the assertion that resident Langerhans cells take up foreign antigens and then migrate through dermal lymphatics to local lymph nodes where they function as antigen-presenting cells. Thus, Langerhans cells play a pivotal role in the primary immune response and in the pathogenesis of skin diseases. In the past, most therapeutic treatment of skin diseases was achieved by administration of pharmacological agents by epicutaneous application. More recently, the determination of the toxicity of drugs and their pharmacological mechanisms has required the development of in vitro models to explore their potential effects at the cellular level. The effects of different agents (physical and chemical) on the density and function of fresh or cultured Langerhans cells are reviewed. 相似文献
906.
Patients with early ovarian carcinoma have a much better survival outcome than patients with more advanced disease. Comprehensive surgical staging is crucial for the determination of prognosis and treatment planning. During 2003, the first randomized trials were published demonstrating that adjuvant platinum based chemotherapy improves recurrence free and overall survival. Current treatment recommendations are largely based on the results of these studies. Accordingly, systemic adjuvant therapy should be offered to patients with disease stage Ib or higher and to patients with moderately differentiated or undifferentiated tumors. Due to incomplete surgical staging, the stage of disease in the patients included in these studies is probably underestimated, and only a fraction of the actual advanced stage patients is included. 相似文献
907.
908.
909.
910.
Thomas J Beck Anne C Looker Firas Mourtada Maithili M Daphtary Christopher B Ruff 《Journal of bone and mineral research》2006,21(9):1425-1432
Age trends in proximal femur stresses were evaluated by simulating a fall on the greater trochanter using femur geometry from hip DXA scans of 5334 white men and women in the NHANES III survey. Expansion of femur outer diameter seems to counter net bone loss so that stresses remain similar across age groups, but stresses are higher in older women than in older men. INTRODUCTION: The age decline in hip BMD is caused by both bone loss and expansion of outer diameter that increases the region size over which mass is measured in a DXA scan. Because expansion has an opposing effect on structural strength, it may be a homeostatic adaptation to net bone loss to ensure that load stresses are kept within a narrow range. MATERIALS AND METHODS: Age trends in femur stresses were evaluated with an engineering beam simulation of a fall on the greater trochanter. Hip geometry was extracted from hip DXA scans using the Hip Structure Analysis (HSA) software on 2613 non-Hispanic white men and 2721 women from the third National Health and Nutrition Examination Survey (NHANES III). Using body weight as load, stresses were computed on the inferior-medial and superior-lateral femur neck at its narrowest point and the medial and lateral shaft 2 cm distal to the midpoint of the lesser trochanter. Stresses and the underlying geometries in men and women >50 years oaf age were compared with those 20-49 years of age. RESULTS: Compared with men <50 years of age, stresses in older men were 6% lower on both surfaces of the shaft, 4% lower on the inferior-medial neck, and not different on the superior-lateral neck. In women >50 years of age, stresses on the proximal shaft and inferior-medial neck remained within 3% of young values but were 13% greater on the superior-lateral neck. Neck stresses in young women were lower on the superior-lateral than the inferior-medial neck, but lateral stress increased to the level on the medial surface in older women. Stresses were higher in women than in men, with a greater gender difference in those >50 years of age. CONCLUSIONS: We conclude that femur expansion has a homeostatic effect in men and women that opposes bone loss so that stresses change little with age. Because expansion preserves stresses with progressively less bone mass, the process may reduce structural stability in the femoral neck under fall conditions, especially in the elderly female. 相似文献