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   3503篇
  免费   194篇
  国内免费   123篇
耳鼻咽喉   11篇
儿科学   134篇
妇产科学   64篇
基础医学   503篇
口腔科学   60篇
临床医学   305篇
内科学   811篇
皮肤病学   103篇
神经病学   145篇
特种医学   427篇
外国民族医学   1篇
外科学   322篇
综合类   46篇
预防医学   342篇
眼科学   47篇
药学   300篇
中国医学   10篇
肿瘤学   189篇
  2021年   42篇
  2019年   48篇
  2018年   72篇
  2017年   31篇
  2016年   61篇
  2015年   64篇
  2014年   58篇
  2013年   104篇
  2012年   104篇
  2011年   119篇
  2010年   112篇
  2009年   99篇
  2008年   125篇
  2007年   156篇
  2006年   127篇
  2005年   160篇
  2004年   113篇
  2003年   97篇
  2002年   100篇
  2001年   91篇
  2000年   98篇
  1999年   73篇
  1998年   109篇
  1997年   113篇
  1996年   121篇
  1995年   82篇
  1994年   70篇
  1993年   74篇
  1992年   57篇
  1991年   72篇
  1990年   77篇
  1989年   82篇
  1988年   76篇
  1987年   82篇
  1986年   64篇
  1985年   75篇
  1984年   37篇
  1983年   38篇
  1982年   31篇
  1981年   27篇
  1980年   42篇
  1979年   29篇
  1978年   24篇
  1977年   26篇
  1976年   34篇
  1975年   35篇
  1974年   31篇
  1972年   24篇
  1968年   25篇
  1967年   26篇
排序方式: 共有3820条查询结果,搜索用时 31 毫秒
1.
2.
The results of parenteral treatment with Etaretin in 40 patients (79 eyes) suffering from senile maculopathy are reported. In 84% of the cases there was a degeneration of the dry type and in 16% a disciform exudative maculopathy. The cases of dry maculopathy responded well within a floow-up period of 8 to 18 months.  相似文献   
3.
Summary— To investigate if the functional alterations observed in resistance arteries of spontaneously hypertensive rats (SHRs) were also present at the coronary level, in vitro experiments were performed in mesenteric resistance arteries (MRA) and in right (RIC) and left interventricular coronary (LIC) arteries taken from 15–25-week-old SHR and age-matched Wistar Kyoto rats WKYs. Using a passive extension protocol, internal diameters corresponding to 100 mmHg intraluminal pressure (D100) were determined and vessels were set up to a normalized internal diameter (0.9 D100). SHR mesenteric resistance arteries had a significantly smaller diameter compared to WKY arteries, whereas both types of SHR coronary arteries had a greater diameter compared to those of WKY rats. In arteries in the absence of contracting agonist, nitro-L-arginine (NOLA, 100 μM) induced a progressive rise in basal tone, which could be reversed by subsequent addition of L-arginine (100 μM) but not D-arginine (100 μM). When expressed as percent of maximal contractions induced by agonists (noradrenaline, NA [10 μM] in MRA; serotonin, 5-HT [10 μM], in RIC and LIC), these contractions were significantly stronger in WKY compared to SHR coronary and mesenteric resistance arteries. In NA-precontracted MRA and 5HT-precontracted coronary arteries in the presence of indomethacin (10 μM), the magnitude of acetylcholine-induced maximal relaxations (expressed as percent of maximal contractions induced by agonists) was greater in WKY compared to SHR arteries. After a 30-min incubation period, NOLA (100 μM) completely inhibited relaxations induced by acetylcholine (0.01–10 μM) in all types of precontracted arteries. Subsequent additions of sodium nitroprusside, (SNP, 10 μM) induced complete relaxations in all preparations. These results show that a basal release of NO or NO-like compound by endothelial cells is present in isolated mesenteric resistance and coronary arteries of WKY rats and SHRs. The contribution of endothelium-derived relaxing factor-nitric oxide (EDRF-NO) to arterial tone was lower in MRA compared to coronary arteries in both strains and in SHR compared to WKY arteries. In the SHR preparations, the impaired relaxation induced by acetylcholine appeared to be due to a functional alteration of the endothelium in the presence of normal reactivity of the smooth muscle cells.  相似文献   
4.
麦冬类中药组织切片计算机三维重建图鉴   总被引:9,自引:0,他引:9  
利用计算机技术实现麦冬类中药组织连续切片三维重建与动态显示,为计算机辅助生药学鉴定和教学提供了新的三维图像技术和研究资料。  相似文献   
5.
6.
A series of 73 dibenzo[a,d]cycloalkenimines were synthesized and evaluated for their ability to displace (+)-10,11-dihydro-5-methyl-5H-dibenzo[a,d]cyclohepten-5,10-imine ([3H]-(+)-10) from its specific binding site on rat cortical membranes. A number of the more active compounds (Ki ranging from 0.006 to 0.21 microM) were evaluated for N-methyl-D-aspartate (NMDA) antagonist activity in the rat cortical slice (Kb ranging from 0.08 to 0.9 microM) and anticonvulsant activity in the mouse against NMDA induced convulsions. The ED50 values ranged from 0.22 to 7.76 mg/kg and correlated reasonably well with the Kb determination. In the dibenzo[a,d]cyclohepten-5,10-imine series, the (+)-5S,10R enantiomer displayed consistently higher levels of biological activity. While substitution at the 3-position of (+)-10 with electronegative atoms generally increased in vitro activity, a loss of potency relative to (+)-10 (MK-801) was observed in vivo for all of the compounds tested.  相似文献   
7.
表小檗碱对α受体的作用   总被引:2,自引:0,他引:2  
王嘉陵  方达超 《药学学报》1990,25(4):289-292
表小檗碱(epiberberine,EB)是从湖北产黄连(Coptis chinensis Franch)中提取的一种生物碱,属苯喹嗪类原小檗碱,对其药理作用的研究资料甚少,未见其对α肾上腺素体作用的报道。资料表明,许多原小檗碱类化合物有α受体阻滞作用,为从该类化合物中选择  相似文献   
8.
PURPOSE: This paper briefly summarizes the research on increased radiosensitivity in breast cancer patients measured by the micronucleus test (MNT) and its association to genetic variants in DNA repair genes. More preliminary data are presented on the distribution of chromosomes and chromosome fragments in micronuclei (MN) in order to gain more information on clastogenic and aneugenic effects and better understand the phenotype of increased radiosensitivity. MATERIAL AND METHODS: Reports of relevant studies obtained from a search of PubMed and studies referenced in those reports were reviewed. In four patients with high MN frequency (three cancer patients, one control) and four probands with low MN frequency, the presence of chromosome fragments or whole chromosomes in MN was determined by fluorescence in situ hybridization analysis for chromosomes 1, 7, and 17. RESULTS: An increased MN frequency in breast cancer patients compared to controls has consistently been reported with high significance. Higher MN frequencies were observed in 20-50% of breast cancer patients. Chromosomal fragments of chromosome 17, but not of chromosomes 1 and 7 were more frequent in the probands with high MN frequency than in those with low frequency (p = 0.045). CONCLUSION: The MNT detects a cellular phenotype common to a portion of sporadic breast cancer patients. This phenotype is very likely to be genetically determined. For the genetic dissection of breast cancer susceptibility this phenotype may turn out to be more efficient than breast cancer itself. Additional parameters which can be measured simultaneously with the MN frequency may be able to further enhance its usefulness.  相似文献   
9.
10.
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