首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   95674篇
  免费   8518篇
  国内免费   5463篇
耳鼻咽喉   961篇
儿科学   1313篇
妇产科学   1668篇
基础医学   12660篇
口腔科学   1641篇
临床医学   12677篇
内科学   14780篇
皮肤病学   1434篇
神经病学   5864篇
特种医学   3348篇
外国民族医学   53篇
外科学   9779篇
综合类   10866篇
现状与发展   21篇
一般理论   60篇
预防医学   6699篇
眼科学   3221篇
药学   9475篇
  67篇
中国医学   4186篇
肿瘤学   8882篇
  2024年   264篇
  2023年   1356篇
  2022年   3498篇
  2021年   4628篇
  2020年   3286篇
  2019年   3376篇
  2018年   3587篇
  2017年   2892篇
  2016年   3097篇
  2015年   4232篇
  2014年   5325篇
  2013年   4927篇
  2012年   7271篇
  2011年   7769篇
  2010年   4716篇
  2009年   3606篇
  2008年   5155篇
  2007年   5048篇
  2006年   5136篇
  2005年   4905篇
  2004年   3483篇
  2003年   3167篇
  2002年   2679篇
  2001年   1871篇
  2000年   1848篇
  1999年   2135篇
  1998年   1404篇
  1997年   1341篇
  1996年   1027篇
  1995年   964篇
  1994年   838篇
  1993年   532篇
  1992年   641篇
  1991年   547篇
  1990年   505篇
  1989年   451篇
  1988年   407篇
  1987年   320篇
  1986年   273篇
  1985年   244篇
  1984年   161篇
  1983年   115篇
  1982年   72篇
  1981年   87篇
  1980年   60篇
  1979年   80篇
  1978年   41篇
  1977年   35篇
  1976年   31篇
  1974年   43篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
本文对41例年龄7—12岁右利健康儿童,头部选取5对(10个)样点,对各样点的功率和相对功率Ⅰ,Ⅱ的四个经典频带(δ,θ,α,β)进行几种数学转换,用正态性D检验法观察各参量转换前后的分布状态。结果,转换前,功率分布状态较差;而相对功率的参量原值近正态分布的情况较好,其中相对功率Ⅰ较相对功率Ⅱ更佳。而相对功率Ⅰ的X、log(X)和log(X/1—X)转换为最佳。就功率而言,log(x)转换最好,但仍不能完全满足各频带统计学的要求。  相似文献   
992.
Summary Based upon findings from 60 cadavers (120 sides), the incidence of superior laryngeal nerve loop, connecting the cervical sympathetic chain and the superior laryngeal nerve and its branches, the external and internal laryngeal nerve, was 98.3% (118 out of 120 sides). In most cases the loop connected the sympathetic chain and the external laryngeal nerve. The external laryngeal nerve was looped, and not linear as traditionally thought. The loop could be divided into three categories, V-shaped, U-shaped and mixed, and subdivided into 5 types and 17 subtypes according to morphological variation. The loop without exception innervated not only the cricothyroid muscle, but also the thyroid gland. The loop is one of the origins of the thyroid nerve. It seems that for thyroid surgery the loop, when lower in position, should be carefully separated from the superior thyroid vessels before the latter are ligated, in order to preserve a normal nerve supply to the muscle as well as to the part of the gland that remains after surgery.
L'anse du nerf larynge supérieur, étude anatomique et applications chirurgicales
Résumé La fréquence d'une anse du nerf laryngé supérieur réalisant une anastomose entre la chaine sympathique cervicale et le nerf laryngé supérieur et/ou ses branches (rameau laryngé externe et ingerne), est de 98,3 % (118/120). Ce résultat s'appuie sur l'étude de 60 cadavres. Dans la plupart des cas, l'anastomose se fait entre la chaine sympathique cervicale et le rameau laryngé externe. Ce rameau laryngé externe a un trajet curviligne et non linéaire conformément aux données classiques. Il existe trois catégories d'anses : en "V", en "U" et mixte ; on peut également les subdiviser en 5 types et 17 sous-types en fonction des variations morphologiques. Cette anse innerve constamment non seulement le muscle cricothyroïdien mais aussi la glande thyroïde dont elle fournit une partie de l'innervation. Lors de la chirurgie thyroïdienne, si l'anse est en position basse, les nerfs doivent être soigneusement disséqués et séparés des vaisseaux thyroïdiens supérieurs avant ligature de ces derniers de façon à conserver l'innervation normale du muscle et de la partie restante de la glande.
  相似文献   
993.
人体寰椎横韧带拉伸性能的实验研究   总被引:4,自引:1,他引:4  
目的:研究人体寰椎横韧带的拉伸性能。方法:新鲜寰椎标本8例,制备成拉伸试件,进行定速率单向拉伸至横韧带断裂。结果:寰椎横韧带平均最大载荷为311.6N,最大变形量为6.0mm,刚度为72.9N/mm。结论:寰椎侧块间的分离超过6.0mm,就可存在横韧带断裂。  相似文献   
994.
The natural antibiotic molecules, beta-defensins 1 and 2 (HBD1/2) and secretory leukocyte protease inhibitor (SLPI), have an important role in mucosal defence and are present in the uterus. This study details their regulation in primary endometrial epithelial cells and in two endometrial cell lines (MFE/HES). Cells were treated with proinflammatory molecules and mimics of infection [lipopolysaccharide (LPS) and lipoteichoic acid (LTA)]. mRNA for HBD1, HBD2 and SLPI was detected in primary endometrial epithelial cells using real-time quantitative PCR. HBD1 mRNA was present at very low levels preventing conclusive study of its regulation. However, HBD2 mRNA expression was increased by interferon-gamma, interleukin (IL)-1beta alone and IL-1beta+tumour necrosis factor (TNF)-alpha. SLPI mRNA was not affected by proinflammatory mediators, although protein levels fell in the presence of IL-1beta+TNFalpha. LPS had little effect on antimicrobial expression. However, there was a trend towards increased expression with LTA treatment for 4-8 h. Antimicrobial expression in endometrial cell lines was similar to that in primary cells, although SLPI was increased by IL-1beta+TNFalpha treatment. These results suggest that in endometrium some natural antibiotics (e.g. SLPI) may be constitutively expressed providing a basal level of protection, while others (e.g. HBD2) are inducible allowing maximal antimicrobial activity during infection. Natural antimicrobials will have an important role in endometrium in protecting against infection.  相似文献   
995.
996.
目的分析改良股骨近端锁定钢板治疗老年A2型股骨转子间骨折的疗效。方法 2012年2月~2013年7月间收治76例股骨转子间骨折患者,符合研究入选标准40例,随机分成两组,研究组和对照组,研究组给予改良股骨近端锁定钢板内固定治疗,对照组给予普通股骨近端锁定钢板内固定治疗。以Harris髋关节评分标准评价疗效及对疗效进行统计学分析。结果 40例患者均获随访,平均10.5月(5~18月),研究组Haris评分(89±7.24)分,对照组Haris评分(76±6.84)分,=5.837,0.01。结论对于老年A2型股骨转子间骨折,改良股骨近端锁定钢板与普通股骨近端锁定钢板相比,能够有效增加固定的可靠性,降低并发症的发生率,疗效满意。  相似文献   
997.
微波体模   总被引:9,自引:1,他引:9  
用水、盐,聚氯乙烯粉和羧甲基纤维钠四种材料配制成一种适用的微波体模(模拟肌肉组织)。该体模的复介电系数在300~2500MHz范围内与实际人体肌肉组织的误差≤5%。这种体模的优点是材料立足国内,价廉,室温下配制,使用方便。本文也给出这种体模的温度特性,稳定性和热学特性,供电磁场生物效应和微波热疗等研究使用。  相似文献   
998.
BACKGROUD: Transferring a germinal vesicle (GV) from an aged woman's oocyte into ooplasm from a younger woman has been proposed as a possible way to overcome the problem of age-related decline in female fertility. Here we assessed this possibility by determining whether ooplasts derived from young mice could rescue ageing-associated chromosome misalignment in meiosis of oocytes from aged mice. METHODS: Three groups of reconstructed oocytes, young GV-young cytoplast (group YY), aged GV-young cytoplast (group AY), and young GV-aged cytoplast (group YA), were created by micromanipulation and electrofusion. RESULTS: Nuclear transplantation was successful in 89.8-94.4% of GV-ooplast complexes, and maturation rate of the reconstructed oocytes was 93.5-97.9%. Confocal microscopy analysis showed a significantly higher rate (49.2%) of chromosome misalignment in ageing mice than in young mice (16.9%), and 57.1% of oocytes in group AY exhibited chromosome misalignment, while the abnormality rate in groups YY and YA was 16.3 and 16.7% respectively. Calcium imaging showed that the three groups of reconstructed oocytes exhibited a similar pattern of calcium oscillations upon stimulation with bovine sperm extracts. Fertilization rate and developmental capacity to 2-cell embryos were also similar among the three groups of oocytes. CONCLUSIONS: Our findings suggest that: (i) the ooplasm from young mice could not rescue ageing-associated chromosome misalignment in meiosis of GV from aged mice; and (ii) behaviour of chromosome alignment over metaphase spindle is predominantly determined by GV material.  相似文献   
999.
采用小鼠神经母细胞瘤细胞无血清培养,建立神经细胞老化实验研究模型。以流式细胞光度术观察精氨酸加压素(AVP)对老化过程中实验性神经细胞的细胞周期和细胞总蛋白的影响。结果发现AVP可产生延缓细胞老化的细胞周期和细胞总蛋白的变化。提示AVP通过使细胞周期、DNA和细胞总蛋白等发生变化来发挥其延缓实验性神经细胞老化的作用。  相似文献   
1000.
Summary Gibson (1966, 1979) and Lee (1976) have described the potential usefulness of optic-flow information for the control of locomotion. One variable that might be particularly important for an animal approaching a target is time-to-collision, which Lee argues is most efficiently specified by the tau margin (the inverse of the relative rate of expansion of the target image on the retina). In humans, most empirical studies of optic flow have required perceptual judgements or have examined catching/intercepting behaviours. In animals, most studies have been strictly observational. This is particularly true for mammals, where there has been no experimental work of any kind looking at the control of locomotion. The present experiment demonstrates that the Mongolian gerbil (Meriones unguiculatus) uses time-to-collision information to control deceleration as it runs towards a target. The development of this animal model will aid investigation of the neural circuitry underlying optic flow utilization in motor control.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号