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   88950篇
  免费   6211篇
  国内免费   3336篇
耳鼻咽喉   406篇
儿科学   1161篇
妇产科学   1285篇
基础医学   16111篇
口腔科学   1220篇
临床医学   5708篇
内科学   14442篇
皮肤病学   1442篇
神经病学   10650篇
特种医学   1207篇
外国民族医学   28篇
外科学   6533篇
综合类   10673篇
现状与发展   12篇
预防医学   2750篇
眼科学   758篇
药学   13859篇
  7篇
中国医学   1614篇
肿瘤学   8631篇
  2024年   130篇
  2023年   1046篇
  2022年   1845篇
  2021年   2622篇
  2020年   2225篇
  2019年   2227篇
  2018年   2351篇
  2017年   2360篇
  2016年   2459篇
  2015年   2870篇
  2014年   4670篇
  2013年   5991篇
  2012年   4604篇
  2011年   5441篇
  2010年   4492篇
  2009年   4604篇
  2008年   4974篇
  2007年   4732篇
  2006年   4157篇
  2005年   3692篇
  2004年   3399篇
  2003年   3082篇
  2002年   2669篇
  2001年   2336篇
  2000年   2085篇
  1999年   1856篇
  1998年   1987篇
  1997年   1855篇
  1996年   1667篇
  1995年   1303篇
  1994年   1261篇
  1993年   1124篇
  1992年   850篇
  1991年   769篇
  1990年   664篇
  1989年   510篇
  1988年   456篇
  1987年   387篇
  1986年   393篇
  1985年   515篇
  1984年   404篇
  1983年   259篇
  1982年   313篇
  1981年   259篇
  1980年   188篇
  1979年   127篇
  1978年   89篇
  1977年   64篇
  1976年   55篇
  1975年   31篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Summary Buspirone, a putative serotonin (5-HT)1A partial agonist, did not produce hypothermia in 17 normal volunteers in a placebo controlled, single blind study. Thus, buspirone may be a weaker agonist at those 5-HT1A receptors which mediate hypothermia compared to ipsapirone or gepirone, two other 5-HT1A partial agonists which have been reported to produce hypothermia by a 5-HT1A-mediated mechanism.  相似文献   
142.
Retinol-binding protein (RBP) is the transport protein that carries retinol in the circulation from the liver to its target tissues. The existence of a cell-surface receptor on the target cells, which mediates the uptake of retinol from RBP, has been known since 1975. Recently, it was identified as an integral transmem-brane protein named STRA6 that is inducible by retinoic acid in certain cancer cells. The receptor was found to be highly specific for RBP, with high affinity, and to be localized in all tissues known to require retinol for their function, particularly the pigment epithelium of the eye.  相似文献   
143.
为探讨临床中使用钙制剂抢救链霉素过敏休克病人有良好效果的原因,由被动血凝试验、被动皮肤过敏试验和ELISA法证实,Ca~( )可以抑制链霉素抗原-抗体的反应。这种抑制作用是通过Ca~( )链霉素抗原结合,封闭链霉素抗原决定簇来加以实现的。  相似文献   
144.
Chronic treatment with the beta-carboline derivative FG 7142 (15 mg/kg i.p. twice a day for 10 consecutive days) produced a long-lasting enhancement of shock-induced suppression of drinking in rats, without affecting unpunished behaviour. This proconflict effect was observed up to 15 days after withdrawal from FG 7142. A significant sensitization to seizures induced by isoniazid, a drug known to inhibit GABAergic transmission, was also found to occur after long-term (25 days) withdrawal. Moreover, the density of low-affinity GABA receptors was decreased by 30% in the cerebral cortex of rats repeatedly injected with FG 7142 at 5 and 15 days after withdrawal. The capacity of high-affinity GABA receptors, as well as the apparent dissociation constants for both high- and low-affinity GABA receptors were unchanged. Similar modifications in [3H]GABA binding were also observed in the cerebellum. The enhancement of punishment suppressed behaviour, the sensitization to isoniazid-induced convulsions and the decrease in the density of low-affinity GABA receptors suggest that chronic administration of FG 7142 induces a persistent down-regulation of GABAergic transmission in the central nervous system.  相似文献   
145.
The spectral response curve (amplitude versus wavelength) of the R2 of the early receptor potential (ERP) was studied in normal, protan, and deutan subjects. The R2 amplitude peaked at 520nm in most normal subjects. The R2 at long wavelengths was smaller than normal in protans and larger than normal in deutans when the maximum amplitudes were normalized to 100% at the peak. The ratio of the R2 amplitude at 460 nm to that at 600 nm clearly differed between protans and deutans. The ERP and the rapid off-response, which is mainly due to the cessation of the late receptor potential, were recorded in the same subjects. The ratio of the sensitivity of the rapid off-response at 500 nm to that at 600 nm was correlated with the ratio of the R2 amplitude at 460 nm to that at 600nm (correlation coefficient, 0.823, p < 0.001). This study, in conjunction with our previous study, indicates that the abnormality is in the outer segments of the cones in protans and deutans.  相似文献   
146.
An enzyme-linked immunosorbent assay (ELISA) was used to measured IgG antiboody titers againt a synthetic peptide whose sequence was derived from the glycine-alanine repeating region of Epstein-Barr virus nuclear associated antigen 1 (EBNA-1). Antibody titers were determined in sera from 15 normal subjects, sera from 21 normal male siblings of X-linked lymphoproliferative syndrome (XLP) patients, from 20 XLP patients comprising a total of 42 samples, and ten samples before and ten samples after gamma-globulin therapy in ten patients with XLP. Data analysis demonstrated that while there are differences between the ELISA and ACIF, they appear to measure a similar response as demonstrated by their correlation coefficient (0.77) and the GMT to EBNA observed by both methods. No cross-reactivity of cytomegalovirus antibodies to the EBNA-1 peptide was observed by immunobv using adsorption against AD-169 infected MRC-5 cells.. However, non-specific binding was observed if samples were not pre-incubated in a 10% goat serum PBS-Tween 20 solution. This pre-treatment removed the non-specific binding that falsely elevated GMT in approximately 15% of both normal and XLP samples in ELISA. The ELISA system appears to be a sensitive, reproducible and objective test that may be useful for assessing the antibody responses of patients to the EBNA-1 protein.  相似文献   
147.
本文将聚乙二醇(PEG)比浊法和固相酶联免疫法(ELISA)结合,建立了—较灵敏的免疫复合物(IC)直接固相吸附抗原特异性检测法。利用牛清蛋白(BSA)为已知抗原组份的IC模型,分别对IC直接固相吸附的条件和影响因素、方法的灵敏度、重复性等进行了研究。结果发现IC在解离状态下直接固相吸附后的抗原特异性检测灵敏度明显高于未解离者。该法具有简单易行,灵敏度较高、适于临床测定大量血清样品等优点。  相似文献   
148.
149.
目的检测以质粒pIRES为载体构建的带有全序列癌胚抗原(CEA)基因的核苷酸疫苗对机体特异性抗肿瘤免疫反应的激活效果。方法将CEA基因片段连接于真核表达质粒pIRES中,用肌肉注射方法接种核酸疫苗;检测CEA在小鼠肌肉组织中的表达情况及其对小鼠脾细胞CEA特异性细胞免疫反应的激活效果。结果小鼠经肌肉注射质粒后,免疫组化证实该核酸疫苗可在体内有效表达CEA;分子免疫检测显示注射后小鼠特异性淋巴细胞增值反应明显并且伴有自然杀伤细胞NK活性显著增高。结论实验所构建的核酸疫苗pIRESCEA可在体外及小鼠体内高效表达并表现出良好的细胞免疫原性。  相似文献   
150.
三种实验性IgA肾病模型的比较   总被引:4,自引:0,他引:4  
目的探讨建立一种理想的IgA肾病(IgAN)动物模型方法。方法分别采用葡聚糖G200、大肠杆菌外膜蛋白和金葡菌的细胞膜20肽抗原决定簇诱导小鼠IgA肾病模型。用分子生物学和病理学方法对3组IgAN模型小鼠进行鉴定和比较。结果(1)葡聚糖组尿蛋白增高,伴有血尿;免疫荧光显示部分肾小球大量IgA沉积;光镜下肾小球系膜细胞增多,肝和脾可见弥漫性的粉染物质沉积;电镜下肾小球系膜区少量低电子密度的致密沉积物,肝和脾可见淀粉丝样物质沉积。(2)大肠杆菌外膜蛋白组尿蛋白增高,伴有血尿;免疫荧光显示肾小球有少量IgA沉积;光镜下肾小球系膜细胞轻度增多,间质炎细胞浸润明显;电镜下肾小球系膜区无电子致密沉积物。(3)金葡菌细胞膜20肽抗原决定簇组尿蛋白增高,伴有血尿;免疫荧光显示多数肾小球均可见大量IgA沉积;光镜下肾小球系膜细胞增多,伴系膜基质轻度增生;电镜下肾小球系膜区和基底膜的内皮细胞下可见高电子密度的致密沉积物。结论金葡菌细胞膜20肽抗原决定簇组诱导的IgAN模型从临床表现和病理学变化与人IgAN极其相似,是3种IgAN模型中最理想的IgAN模型。  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