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   1296篇
  免费   105篇
  国内免费   18篇
耳鼻咽喉   3篇
儿科学   84篇
妇产科学   8篇
基础医学   108篇
口腔科学   30篇
临床医学   94篇
内科学   231篇
皮肤病学   37篇
神经病学   48篇
特种医学   132篇
外科学   113篇
综合类   136篇
预防医学   224篇
眼科学   4篇
药学   65篇
中国医学   39篇
肿瘤学   63篇
  2023年   10篇
  2022年   20篇
  2021年   23篇
  2020年   22篇
  2019年   19篇
  2018年   29篇
  2017年   18篇
  2016年   40篇
  2015年   38篇
  2014年   57篇
  2013年   59篇
  2012年   67篇
  2011年   63篇
  2010年   78篇
  2009年   73篇
  2008年   34篇
  2007年   46篇
  2006年   61篇
  2005年   41篇
  2004年   22篇
  2003年   26篇
  2002年   18篇
  2001年   24篇
  2000年   16篇
  1999年   23篇
  1998年   47篇
  1997年   61篇
  1996年   52篇
  1995年   39篇
  1994年   33篇
  1993年   34篇
  1992年   12篇
  1991年   7篇
  1990年   11篇
  1989年   26篇
  1988年   25篇
  1987年   18篇
  1986年   19篇
  1985年   12篇
  1984年   16篇
  1983年   4篇
  1982年   12篇
  1981年   8篇
  1980年   11篇
  1979年   3篇
  1977年   6篇
  1976年   7篇
  1969年   3篇
  1958年   4篇
  1957年   3篇
排序方式: 共有1419条查询结果,搜索用时 15 毫秒
51.
尚千涵  高其媛  杨婷  梁健  王乐  洒威  王玛丽  申智清  李忠虎 《中草药》2021,52(18):5782-5788
羊肚菌Morchella esculenta是子囊菌亚门的一种大型药食两用真菌,具有重要的经济价值和药用价值。然而近年来全球气候变化,导致羊肚菌属物种的栖息地破碎和片段化,加上消费者对羊肚菌美食的喜爱,过渡采挖造成羊肚菌属野生资源急剧减少,因此,急需对羊肚菌属物种资源进行保护。遗传多样性的时空分布是保护生物学的重要内容,遗传多样性关系到一个物种或类群的进化潜力和未来命运。生物基因组和进化的研究能够辅助挖掘物种深层次的优异基因资源,有利于从本质上对物种进行科学保护。从羊肚菌属的遗传多样性、遗传结构和家系关系以及基因组进化等的研究进展进行综述,以期为羊肚菌属资源的科学保护提供重要依据。  相似文献   
52.
癌性疼痛是肿瘤最为常见的临床症状之一,如何有效地控制癌性疼痛,改善癌症病人的生活质量,延长生存期已成为全球关注的焦点。WHO调查认为:进展期癌症和终末期癌症病人约75%~90%以疼痛为主要临床症状,经过治疗90%的癌性疼痛可缓解。单纯运用西医的三阶梯镇痛疗法会导致病人药物成瘾性及较大的毒副作用;而单纯运用中医药疗法止痛效果不甚显著。因此,将中西医疗法结合运用到治疗癌性疼痛上,将成为今后癌症病人综合治疗的重要环节,尤其近年来中医学以其独特的理论体系,辨病辨证相结合,采用中药内服、外用、针灸等方法,对癌性疼痛的治疗研究取得了满意的进展。  相似文献   
53.
丁香水溶性化学成分的研究   总被引:2,自引:0,他引:2  
目的:研究丁香水溶性化学成分。方法:利用HP-20大孔吸附树脂、反相硅胶柱色谱、反相制备薄层色谱、制备型反相高效液相色谱进行分离,NMR和MS等方法进行结构鉴定。结果:从丁香干燥花蕾的水提物中分离鉴定了5个化合物,分别为槲皮素-3-O-葡萄糖醛酸苷(1),槲皮素-3-O-葡萄糖醛酸苷6″-甲酯(2),槲皮素-3-O-葡萄糖苷(3),丁香酚-β-芸香糖苷(4),杨梅酮(5)。结论:化合物1~4为首次从丁香属植物中分离得到。  相似文献   
54.
OBJECTIVE: To prospectively document the prevalence of otitis media with effusion (OME) in 86 African-American children between ages 2 and 5 years. STUDY DESIGN: Eighty-six children in center-based child care whose ear status had been followed from infancy continued to be observed. Middle ear status was assessed by pneumatic otoscopy and tympanometry biweekly. RESULTS: The prevalence of OME decreased as children became older. The mean proportion of examinations demonstrating bilateral OME (BOME) ranged from 12% between 24 to 30 months to 4% between 54 to 60 months of age. The mean proportion of exams revealing bilateral normal ears increased from 77% at 24 to 30 months to 88% at 54 to 60 months of age. Although 60 children had experienced BOME that lasted 4 months or longer in the 6- to 24-month age period, only 8 of these children experienced at least 4 months of continuous BOME between 24 to 60 months. CONCLUSIONS: The proportion of time with BOME decreased progressively with increasing age in this population. Only 8 of 60 children who had experienced more than 4 consecutive months of BOME before 2 years of age continued to manifest persistent effusion or experience recurrences of prolonged BOME after 2 years of age.  相似文献   
55.
目的 研究腹针治疗周围性面瘫的选穴规律。方法 通过计算机及手工检索,选取近15年有关腹针治疗周围性面瘫的相关文献,以临床研究、疗效观察、现代对比实验研究为依据,进行分析归纳,探讨腹针的选穴规律。结果 腹针治疗周围性面瘫主要取任脉、肾经、胃经及脾经上的穴位及腹部新穴,使用频率依次为55.70%、15.44%、14.09%、2.68%、12.08%;腹针治疗周围性面瘫选用的标志性穴位组合规律:主要有引气归元、腹四关、天地针、调脾气,其使用频率依次为48.48%、27.27%、12.12%、12.12%。结论 合理运用腹针,遵循其选穴规律,可有效治疗周围性面瘫。  相似文献   
56.
PurposeComparative efficacy of exenatide versus insulin glargine primarily on glucemic control, and secondarily on body mass index (BMI), lipid profile and blood pressure, in type 2 diabetes mellitus (T2DM) patients suboptimally treated with metformin monotherapy.Material/MethodsForty-seven inadequately treated T2DM patients on metformin assigned to exenatide (n=18) or insulin glargine (n=29) for 26 weeks. Glycosylated hemoglobin (HbA1c), serum lipids, BMI, systolic and diastolic blood pressure, and adverse events, including episodes of hypoglycemia and gastrointestinal symptoms, were recorded.ResultsEither treatment had a similar favorable mean reduction in HbA1c. However, more patients in exenatide group achieved HbA1c ≤ 7% at the 26th week compared with insulin glargine group (p=0.036). Insulin glargine group had significantly more episodes of hypoglycemia compared with exenatide group (p=0.039). Gastrointestinal adverse events were non-significantly higher in the exenatide group. A significantly greater BMI reduction was observed in exenatide group, whereas BMI was not altered in insulin glargine group. Total and LDL cholesterol (p=0.012), and triglycerides (p=0.016) significantly decreased, whereas HDL cholesterol increased (p=0.021) in the exenatide group, whereas only total cholesterol decreased in insulin glargine group. Changes in systolic and diastolic blood pressure were insignificant in both groups.ConclusionsExenatide provided similar reduction in HbA1c, but fewer episodes of hypoglycemia, compared with insulin glargine. Exenatide had also a favorable effect on weight loss, although more gastrointestinal adverse events. Exenatide may provide a justified alternative in second line treatment of T2DM, but more trials are required to elucidate its long-term safety and cost-effectiveness.  相似文献   
57.
Hereditary hemochromatosis (HH) is a common preventable disorder of iron overload that can result in liver cirrhosis and reduced lifespan. Most HH is due to homozygosity for the HFE p.C282Y substitution. We conducted a study of screening for p.C282Y in high schools where p.C282Y heterozygotes (CY) individuals were informed of their genotype by letter. We studied whether these individuals understood the implications of their genotype, whether this resulted in anxiety or reduced health perception and whether cascade testing was higher in families of CY than wild‐type homozygous (CC) individuals. We found 586 of 5757 (1 in 10) screened individuals were CY. One month after receiving their result, 83% correctly answered that they have one copy of p.C282Y. There was no adverse change in anxiety or health perception from prior to screening to 1 month after receiving results. Significantly more family members of CY individuals than CC individuals were informed about HH and had testing for HH. In conclusion, we found that informing CY individuals of their genotype does not increase anxiety and the implications are generally well understood. This leads to cascade testing in a minority of families. CY individuals should be informed of their genetic status when identified by population screening.  相似文献   
58.
Factors involved in the stability of trinucleotide repeats during transmission were studied in 139 families in which a full mutation, premutation or intermediate allele at either FRAXA or FRAXE was segregating. The transmission of alleles at FRAXA, FRAXE and four microsatellite loci were recorded for all individuals. Instability within the minimal and common ranges (0-40 repeats for FRAXA, 0-30 repeats for FRAXE) was extremely rare; only one example was observed, an increased in size at FRAXA from 29 to 39 repeats. Four FRAXA and three FRAXE alleles in the intermediate range (41-60) repeats for FRAXA, 31-60 for FRAXE) were unstably transmitted. Instability was more frequent for FRAXA intermediate alleles that had a tract of pure CGG greater than 37 although instability only occurred in two of 13 such transmissions: the changes observed were limited to only one or two repeats. Premutation FRAXA alleles over 100 repeats expanded to a full mutation during female transmission in 100% of cases, in agreement with other published series. There was no clear correlation between haplotype and probability of expansion of FRAXA premutations. Instability at FRAXA or FRAXE was more often observed in conjunction with a second instability at an independent locus suggesting genomic instability as a possible mechanism by which at least some FRAXA and FRAXE mutations arise.   相似文献   
59.
60.
川芎嗪诱导大鼠骨髓间质干细胞分化为神经元样细胞的研究   总被引:26,自引:0,他引:26  
撒亚莲  李海标 《解剖学报》2003,34(5):514-517
目的用川芎嗪(ligustrazin hydrochloride)在体外定向诱导SD青年鼠骨髓间质干细胞(mesenchymal stem cells,rMSCs)分化为神经元样细胞。方法用低糖DMEM冲洗骨髓腔,收集骨髓细胞悬液,接种在塑料培养瓶中。经体外扩增、纯化,选用第5代后的骨髓间质干细胞进行诱导分化。用10μg/LbFcF预诱导24h,更换成含川芎嗪的无血清培养基DMEM诱导间质干细胞分化为神经元样细胞。用免疫组织化学SABC法鉴定神经丝蛋白(NF—M)、神经元特异性烯醇化酶(NSE)、巢蛋白(nestin)、微管联合蛋白-2(MAP-2)、生长相关蛋白-43(GAP-43)、胶质纤维酸性蛋白(GFAP)的表达。结果第5代间质干细胞形态达到均一,呈梭形。用川芎嗪诱导15min到3h,间质干细胞胞体逐渐增大,并伸出细长突起形似神经元样细胞。免疫组织化学显示NF-M、NSE、nestin、MAP-2和GAP-43表达阳性,而GFAP阴性。对照组上述染色均为阴性。结论川芎嗪可诱导骨髓间质干细胞分化为神经元样细胞。  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