全文获取类型
收费全文 | 110770篇 |
免费 | 7885篇 |
国内免费 | 4671篇 |
专业分类
耳鼻咽喉 | 346篇 |
儿科学 | 2325篇 |
妇产科学 | 1141篇 |
基础医学 | 11302篇 |
口腔科学 | 1694篇 |
临床医学 | 7359篇 |
内科学 | 16930篇 |
皮肤病学 | 2100篇 |
神经病学 | 9390篇 |
特种医学 | 2050篇 |
外国民族医学 | 9篇 |
外科学 | 6695篇 |
综合类 | 15391篇 |
现状与发展 | 13篇 |
预防医学 | 8479篇 |
眼科学 | 760篇 |
药学 | 24224篇 |
23篇 | |
中国医学 | 9207篇 |
肿瘤学 | 3888篇 |
出版年
2024年 | 318篇 |
2023年 | 1684篇 |
2022年 | 2968篇 |
2021年 | 3958篇 |
2020年 | 3544篇 |
2019年 | 3014篇 |
2018年 | 2906篇 |
2017年 | 3256篇 |
2016年 | 3622篇 |
2015年 | 3748篇 |
2014年 | 6558篇 |
2013年 | 7679篇 |
2012年 | 6255篇 |
2011年 | 6994篇 |
2010年 | 5265篇 |
2009年 | 4933篇 |
2008年 | 5077篇 |
2007年 | 5113篇 |
2006年 | 4572篇 |
2005年 | 4017篇 |
2004年 | 3546篇 |
2003年 | 3144篇 |
2002年 | 2548篇 |
2001年 | 2247篇 |
2000年 | 1991篇 |
1999年 | 1738篇 |
1998年 | 1676篇 |
1997年 | 1618篇 |
1996年 | 1507篇 |
1995年 | 1458篇 |
1994年 | 1326篇 |
1993年 | 1148篇 |
1992年 | 1116篇 |
1991年 | 984篇 |
1990年 | 1009篇 |
1989年 | 960篇 |
1988年 | 888篇 |
1987年 | 800篇 |
1986年 | 810篇 |
1985年 | 1157篇 |
1984年 | 1082篇 |
1983年 | 778篇 |
1982年 | 849篇 |
1981年 | 743篇 |
1980年 | 635篇 |
1979年 | 461篇 |
1978年 | 369篇 |
1977年 | 295篇 |
1976年 | 242篇 |
1975年 | 189篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
181.
R. Alan Aitken Michael C. Bibby John A. Double Andrea L. Laws Robert B. Ritchie David W. J. Wilson 《Archiv der Pharmazie》1997,330(7):215-224
A range of 18 derivatives of flavone-8-acetic acid (FAA) with substituents on the 2-phenyl group have been prepared and their anti-tumour activity evaluated in vitro against a panel of human and murine tumour cell lines and in vivo against MAC 15A. There was no clear-cut relationship between in vitro and in vivo activity but the activity in each situation was found to be very sensitive to the precise substitution pattern with closely related isomers giving widely different activities. Some of the compounds, notably 10b,cj , and r , were active in vivo and these require further studies in order to evaluate their potential for development. 相似文献
182.
Stanislw Ryng Zdzislw Machn Zbigniew Wieczorek Michal Zimecki Tadeusz Glowiak 《Archiv der Pharmazie》1997,330(11):319-326
A series of 5-aminomethinimino-3-methyl-4-isoxazolecarboxylic acid phenylamides 4 has been prepared by condensation of 5-amino-3-methyl-4-isoxazolecarboxylic acid phenylamides 1 with trichloroacetic aldehyde. Alcoholysis of trichloro derivatives 2 gave 5-alkoxymethine derivatives 3 which, on reaction with an appropriate amine, formed the corresponding compounds 4 . The compounds obtained were evaluated for their immunological activity. The properties of three compounds, described in this report, permitted inhibition of the immune response in all possible ways: diminishing both types of immune response ( 4d ), humoral immune response ( 4a ), or cellular immune response ( 4c ). Preparation 4d is comparable in its effectiveness to CsA, so it may be potentially used as an agent for prolongation of the function of transplanted organs. Two other compounds may potentially be used in cases where only one type the immune response is required for combating pathogen invasion. 相似文献
183.
Jaafar Mouhyi Lars Sennerby Jeanjacques Pireaux Nicolas Dourov Samir Nammour Jack Van Reck 《Clinical oral implants research》1998,9(3):185-194
The purpose of the present study was to analyse clinically failed and retrieved implants prior to and after cleaning by means of scanning electron microscopy (SEM) and X-ray induced photoelectron spectroscopy (XPS) as compared to unused controls. Six different chemical and physical techniques for cleaning of contaminated titanium implants were evaluated: 1) rinsing in absolute ethanol for 10 min, 2) cleaning in ultrasonic baths containing trichloroethylene (TRI) and absolute ethanol, 10 min in each solution, 3) abrasive cleaning for 30 s, 4) cleaning in supersaturated citric acid for 30 s, 5) cleaning with continuous CO2-laser in dry conditions at 5 W for 10 s, 6) cleaning with continuous CO2-laser in wet conditions (saline) at 5 W for 10 s. SEM of failed implants showed the presence of contaminants of varying sizes and XPS showed almost no titanium but high carbon signals. XPS of unused titanium implants showed lower levels of titanium as previously reported, probably due to contamination of carbon which increased with time in room air. Cleaning of used implants in citric acid followed by rinsing with deionized water for 5 min followed by cleaning in ultrasonic baths with TRI and absolute ethanol gave the best results with regard to macroscopical appearance and surface composition. However, as compared to the unused implants the results from an element composition point of view were still unsatisfactory. It is concluded that further development and testing of techniques for cleaning of organically contaminated titanium is needed. 相似文献
184.
铜绿假单胞菌全细胞脂肪酸气相色谱分析及应用 总被引:5,自引:0,他引:5
本研究用计算机控制,可程序升温的毛细管柱气相色谱(GC)仪分析48株铜绿假单胞菌标准株和临床株、部分常见假单胞菌、肠杆菌的细胞脂肪酸。结果表明:月桂烯酸(C12:1),月桂酸(C12:0)、十三碳烯酸(C13:1)、十三碳酸(C13:0)、肉豆劳动脑酸(C14:1)、十七碳稀酸(C17:1)、十七碳酸(C17:0)、硬脂酸(C18:0)和花生四烯酸(C20:4)是铜绿包菌有鉴别意义的脂肪酸,组成与 相似文献
185.
中和法制备水杨酸微晶 总被引:1,自引:0,他引:1
为增加水杨酸在各类制剂中的分散度,便于制备,提高疗效,采用酸碱中和法将其制成微晶。先将水杨酸与1mol/L氢氧化钠反应成盐溶解,然后用1mol/L盐酸中和析出微晶。所得微晶呈针状,色白,膨松,在电镜下测得平均粒径为16μm。各项理化标准符合中国药典1995年版规定。本法微晶得率为98%。 相似文献
186.
原发性小肠恶性肿瘤的CT诊断 总被引:15,自引:0,他引:15
本文回顾性分析34例经病理证实的原发性小肠恶性肿瘤的CT表现。病变包括腺癌16例,平滑肌肉瘤12例,淋巴瘤6例。CT扫描能明确肿瘤向腔内和腔外侵犯的程度,清晰显示肿瘤与邻近结构的关系,有无局部及远处转移等,为临床治疗提供帮助。鉴别诊断应包括小肠良性肿瘤、炎性病变和转移性肿瘤等。 相似文献
187.
本文用同时记录两相邻空肠段的收缩活动来观察经10Gyγ线照射后小肠运动的变化,以了解照射后是否出现逆蠕动,以便进一步分析肠套叠形成的原因.结果表明,照射后两相邻肠段出现强度不一的收缩活动,并且可以产生逆蠕动;但是这种逆蠕动发生的机率是不大的.本实验未观察到逆蠕动发生的规律性.因此,逆蠕动的产生可能是照射后发生肠套叠的部分原因. 相似文献
188.
Z. Lackovi M. Jakup
evi A. Bunarevi I. Damjanov M. Relja I. Kostovi 《Brain research》1988,443(1-2):199-203
The content of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and norepinephrine (NE) was analysed in 71 human spinal cords obtained post-mortem. The highest content of 5-HT, 5-HIAA and NE was found in the lumbar enlargement of the spinal cord. 5-HT and 5-HIAA content increased from fetal to adult spinal cord whereas the content of NE decreased. Characteristic segmental distribution of measured monoamines was present in adult spinal cord only. In two patients spinal cord lesion led to the reduction in spinal cord content of 5-HT, 5-HIAA and NE and loss of characteristic segmental distribution of these substances. These results are in general agreement with observations on spinal cord of different animal species. 相似文献
189.
190.
花生四烯酸和二十二碳六烯酸对海马神经细胞生长发育的影响 总被引:2,自引:0,他引:2
【目的】观察不同浓度花生四烯酸 (AA)和 (或 )二十二碳六烯酸 (DHA)对体外培养海马神经细胞生长发育的影响。【方法】无血清培养液中分别加入不同剂量的AA和 (或 )DHA ,采用噻唑蓝比色试验 (MTT法 )反映各组海马神经细胞存活状况 ,神经元特异性烯醇化酶 (NSE)染色鉴定神经细胞 ,图像分析技术测量神经细胞的胞体大小和突起长度。【结果】培养液中分别添加AA为 4~ 8μmol/L、DHA为 2~ 8μmol/L时 ,神经细胞活力高于对照组 ;当培养液中AA和DHA总浓度为 4μmol/L、比例为 2∶1或 4∶1时 ,神经细胞的活力、胞体面积、最大长径、最大短径和平均突起长度均显著高于单一添加 4μmol/LAA、4μmol/LDHA和对照组。【结论】AA、DHA均具有促进体外培养海马神经细胞生长发育的作用 ;与单独添加AA、DHA相比 ,AA和DHA共同作用的促海马神经细胞生长发育作用更好。 相似文献