全文获取类型
收费全文 | 2053篇 |
免费 | 122篇 |
国内免费 | 46篇 |
专业分类
耳鼻咽喉 | 12篇 |
儿科学 | 45篇 |
妇产科学 | 9篇 |
基础医学 | 292篇 |
口腔科学 | 50篇 |
临床医学 | 194篇 |
内科学 | 446篇 |
皮肤病学 | 30篇 |
神经病学 | 208篇 |
特种医学 | 236篇 |
外国民族医学 | 2篇 |
外科学 | 312篇 |
综合类 | 15篇 |
一般理论 | 9篇 |
预防医学 | 77篇 |
眼科学 | 15篇 |
药学 | 144篇 |
中国医学 | 2篇 |
肿瘤学 | 123篇 |
出版年
2021年 | 24篇 |
2020年 | 12篇 |
2019年 | 21篇 |
2018年 | 31篇 |
2017年 | 16篇 |
2016年 | 25篇 |
2015年 | 41篇 |
2014年 | 35篇 |
2013年 | 46篇 |
2012年 | 67篇 |
2011年 | 63篇 |
2010年 | 48篇 |
2009年 | 47篇 |
2008年 | 80篇 |
2007年 | 113篇 |
2006年 | 72篇 |
2005年 | 82篇 |
2004年 | 60篇 |
2003年 | 47篇 |
2002年 | 59篇 |
2001年 | 61篇 |
2000年 | 51篇 |
1999年 | 54篇 |
1998年 | 47篇 |
1997年 | 56篇 |
1996年 | 51篇 |
1995年 | 46篇 |
1994年 | 57篇 |
1993年 | 36篇 |
1992年 | 33篇 |
1991年 | 35篇 |
1990年 | 39篇 |
1989年 | 58篇 |
1988年 | 58篇 |
1987年 | 54篇 |
1986年 | 44篇 |
1985年 | 38篇 |
1984年 | 24篇 |
1983年 | 31篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1977年 | 17篇 |
1976年 | 19篇 |
1975年 | 21篇 |
1974年 | 15篇 |
1973年 | 18篇 |
1971年 | 18篇 |
1970年 | 21篇 |
排序方式: 共有2221条查询结果,搜索用时 15 毫秒
31.
Motor neurons with different susceptibility to degeneration have been identified in amyotrophic lateral sclerosis (ALS). Increase of intracellular calcium has been proposed as a mediator, amplifying the damage through a positive feedback of the known pathological processes. Accordingly, the potential of motor neurons to limit calcium increases during injury might be proportional to their viability. A basic mechanism of reducing calcium amplitudes depends on the calcium-buffering capacity, determined by the calcium-binding protein content. In this study, oculomotor and hypoglossal neurons, prototypes of resistant and vulnerable motor neurons in ALS were examined in axotomy experiments. Total calcium-, parvalbumin-, and calbindin-D28k levels of motor neurons of adult mice were characterized by electron microscopic histochemistry and light microscopic immunostaining. In hypoglossal neurons, compared with oculomotor neurons, larger and more enduring increases of calcium were detected. The perikarya of hypoglossal neurons remained immunonegative for both parvalbumin and calbindin-D28k. Qualitatively, no major cell loss was noted after axotomy, but a decreased neuronal marker staining at days 1-14 suggested a reversible injury of hypoglossal neurons. Oculomotor neurons were not stained for calbindin-D28k but stained for parvalbumin in control conditions, staining which increased at postoperative days 7-14 before returning to baseline. Neuronal marker staining did not change in these cells during the observed period. The higher level of parvalbumin in resistant motor neurons and their ability to up-regulate parvalbumin after injury, paralleled by a smaller increase of intracellular calcium suggest that parvalbumin may have a protective effect in these cells. 相似文献
32.
C. H. ChesnutIII M. Azria S. Silverman M. Engelhardt M. Olson L. Mindeholm 《Osteoporosis international》2008,19(4):479-491
Salmon calcitonin, available as a therapeutic agent for more than 30 years, demonstrates clinical utility in the treatment
of such metabolic bone diseases as osteoporosis and Paget's disease, and potentially in the treatment of osteoarthritis. This
review considers the physiology and pharmacology of salmon calcitonin, the evidence based research demonstrating efficacy
and safety of this medication in postmenopausal osteoporosis with potentially an effect on bone quality to explain its abilities
to reduce the risk of spine fracture, the development of an oral salmon calcitonin preparation, and the therapeutic rationale
for this preparation's chondroprotective effect in osteoarthritis. 相似文献
33.
Background: Central venous cannulation in young children is technically difficult and may lead to potentially serious complications especially when performed blindly or using anatomical landmarks only.
Aim: The aim of this study was to determine the anatomical relationship of the internal jugular vein (IJV) and the common carotid artery (CA) in preschool children using ultrasound.
Methods: Forty five children aged 60 months and under were included prospectively and divided into three groups: group 1: <6 months, group 2: 7–18 months and group 3: 19–60 months. With the head in neutral position the location of the left and right IJV was noted as anterior (A), anterolateral (AL), lateral (L) or medial (M) in relation to the CA at the level of the cricoid cartilage. Depths of IJV and CA as well as time taken to locate the vessels were recorded.
Results: The IJV was more commonly found in the AL position in all groups. The mean depth was 0.96 cm in group 1, 0.95 cm in group 2 and 3. Mean duration for localization of the vessels was 4.2 s in group 1, 4 s in group 2 and 4.3 s in group 3. The differences between the groups were not significant.
Conclusion: This study demonstrates that the IJV cover the CA in the majority of young children. Depth of the IJV is rarely more than 1 cm deep to the skin. Ultrasound location of the IJV and CA is easy and does not necessarily delay the procedure. The findings of this study support the use of ultrasound guidance for CVC in children. 相似文献
Aim: The aim of this study was to determine the anatomical relationship of the internal jugular vein (IJV) and the common carotid artery (CA) in preschool children using ultrasound.
Methods: Forty five children aged 60 months and under were included prospectively and divided into three groups: group 1: <6 months, group 2: 7–18 months and group 3: 19–60 months. With the head in neutral position the location of the left and right IJV was noted as anterior (A), anterolateral (AL), lateral (L) or medial (M) in relation to the CA at the level of the cricoid cartilage. Depths of IJV and CA as well as time taken to locate the vessels were recorded.
Results: The IJV was more commonly found in the AL position in all groups. The mean depth was 0.96 cm in group 1, 0.95 cm in group 2 and 3. Mean duration for localization of the vessels was 4.2 s in group 1, 4 s in group 2 and 4.3 s in group 3. The differences between the groups were not significant.
Conclusion: This study demonstrates that the IJV cover the CA in the majority of young children. Depth of the IJV is rarely more than 1 cm deep to the skin. Ultrasound location of the IJV and CA is easy and does not necessarily delay the procedure. The findings of this study support the use of ultrasound guidance for CVC in children. 相似文献
34.
35.
36.
0 引言 我科 1996 / 1998分别应用消痔灵与强的松龙混合液、消痔灵液、强的松龙液行鼻息肉内 ,鼻息肉蒂部注射治疗鼻息肉各 5 0例 ,并设对照组为鼻腔滴入及口服类固醇激素 5 0例 ,合计 2 0 0例 ,观察并对比其疗效 .1 对象和方法1.1 对象 男 12 8例 ,女 72例 ,年龄 8~ 78(平均 38)岁 ,病程 32 a~ 45 (平均 4.5 ) a.其中在本次治疗前做过一次鼻息肉摘除术后复发的 2 7例 ,做过 2次或 2次以上手术的 12例 .主要症状为鼻塞、流脓涕、头痛及嗅觉减退 .全部病例治疗前均行鼻窦 X线拍片 ,其中上颌窦炎 12 5例、筛窦炎 5 8例、蝶窦炎 2例、… 相似文献
37.
Daniels DL; Czervionke LF; Millen SJ; Haberkamp TJ; Meyer GA; Hendrix LE; Mark LP; Williams AL; Haughton VM 《Radiology》1989,171(3):807-809
The authors evaluated magnetic resonance (MR) images obtained with intravenously administered gadolinium in ten patients who had facial paralysis and no facial nerve tumor. In patients with either Bell palsy (four patients) or facial paralysis after temporal bone surgery (six patients), intratemporal facial nerve enhancement was seen. Facial nerve enhancement on MR images proved to be a nonspecific finding. 相似文献
38.
Computed tomographic study of hormone-secreting microadenomas 总被引:1,自引:0,他引:1
Hemminghytt S; Kalkhoff RK; Daniels DL; Williams AL; Grogan JP; Haughton VM 《Radiology》1983,146(1):65
39.
Julia Welzel MD Eva Lankenau MSc Reginald Birngruber PhD Ralf Engelhardt MSc 《Journal of the American Academy of Dermatology》1997,37(6):958-963
Background: Optical coherence tomography (OCT) is a new diagnostic method for tissue characterization.Objective: We investigated normal and pathologic structures in human skin in several locations to evaluate the potential application of this technique to dermatology.Methods: Based on the principle of low-coherence interferometry, cross-sectional images of the human skin can be obtained in vivo with a high spatial resolution of about 15 μm. Within a penetration depth of 0.5 to 1.5 mm, structures of the stratum corneum, the living epidermis, and the papillary dermis can be distinguished.Results: Different layers could be detected that were differentiated by induction of experimental blisters and by comparison with corresponding histologic sections. Furthermore, OCT images of several skin diseases and tumors were obtained.Conclusion: OCT is a promising new imaging method for visualization of morphologic changes of superficial layers of the human skin. It may be useful for noninvasive diagnosis of bullous skin diseases, skin tumors, and in vivo investigation of pharmacologic effects. (J Am Acad Dermatol 1997;37:958-63.) 相似文献
40.
石杉碱甲类似物的研究II.N-甲基吡啶酮石杉碱甲类似物的合成 总被引:3,自引:1,他引:3
石杉碱甲(1)是从中草药石杉属植物千层塔(Lycopodium serratum Thunb.)中分得的一种高效可逆的乙酰胆碱酯酶抑制剂,临床试验证实它对早老性痴呆症有显著疗效。本文报道N-甲基吡啶酮石杉碱甲类似物2和3的合成。2-甲氧基-5-甲氧羰基-11-亚甲基-5,9-甲撑环辛-7-烯并吡啶(9)在乙腈中用三甲基氯硅烷和碘化钠选择性脱保护以定量的产率得吡啶酮10,再用甲醇钠和碘甲烷甲基化得N-甲基吡啶酮11,11经碱性水解,Curtius重排和氨基的脱保护得N-甲基吡啶酮石杉碱甲类似物2。通过类似的途径从中间体2-甲氧基-5-甲氧羰基-7-甲基-11-酮-5,9-甲撑环辛-7-烯并吡啶(14)合成了类似物3。类似物2和3的乙酰胆碱酯酶抑制活性均低于天然石杉碱甲。 相似文献