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   398320篇
  免费   37375篇
  国内免费   27585篇
耳鼻咽喉   3047篇
儿科学   5194篇
妇产科学   4394篇
基础医学   43157篇
口腔科学   6648篇
临床医学   56055篇
内科学   53139篇
皮肤病学   4421篇
神经病学   19029篇
特种医学   14719篇
外国民族医学   234篇
外科学   35185篇
综合类   74965篇
现状与发展   95篇
一般理论   33篇
预防医学   29820篇
眼科学   11251篇
药学   43682篇
  463篇
中国医学   26947篇
肿瘤学   30802篇
  2024年   1466篇
  2023年   5980篇
  2022年   15706篇
  2021年   19917篇
  2020年   15676篇
  2019年   12612篇
  2018年   12995篇
  2017年   12584篇
  2016年   11507篇
  2015年   17959篇
  2014年   22270篇
  2013年   20428篇
  2012年   30336篇
  2011年   33936篇
  2010年   22960篇
  2009年   18685篇
  2008年   22682篇
  2007年   22426篇
  2006年   21329篇
  2005年   20212篇
  2004年   13390篇
  2003年   13006篇
  2002年   10644篇
  2001年   9074篇
  2000年   8695篇
  1999年   8691篇
  1998年   5470篇
  1997年   5244篇
  1996年   4061篇
  1995年   3807篇
  1994年   3208篇
  1993年   2082篇
  1992年   2509篇
  1991年   2184篇
  1990年   1865篇
  1989年   1599篇
  1988年   1334篇
  1987年   1222篇
  1986年   982篇
  1985年   696篇
  1984年   386篇
  1983年   282篇
  1982年   148篇
  1981年   174篇
  1980年   118篇
  1979年   167篇
  1978年   79篇
  1977年   57篇
  1974年   47篇
  1972年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
目的:评价直肠癌根治术中用Foley尿管气囊压迫治疗骶前静脉丛大出血(MPVP)的临床价值。方法:分析1995~2005年用Foley尿管气囊压迫治疗骶前静脉丛大出血6例的临床资料。结果:6例骶前大出血中全部用Foley尿管气囊压迫控制出血,术中出血量为800~1700mL,Foley尿管于术后4d拔除3例,5d1例,6d2例,均无再出血,会阴切口均一期愈合。结论:Foley尿管气囊压迫治疗骶前静脉丛大出血是一种简单安全有效的治疗方法。  相似文献   
72.
73.
The impact of obesity on female reproductive function   总被引:1,自引:0,他引:1  
Obesity may be described as the new worldwide epidemic, and its serious impact on morbidity and mortality are well known. As more and more women become obese, the reproductive problems associated with obesity present an ever-growing challenge to physicians involved in their fertility care. The spectrum of reproductive problems associated with obesity encompasses a wide range of disorders including infertility problems, miscarriage and pregnancy complications. In this review, we aim to discuss the impact of obesity on the various aspects of female reproductive function with focus on the clinical aspects of fertility problems in obese women. We finally comment on the available therapeutic options available to this group of women.  相似文献   
74.
通过对中南地区1577例正常人的血清α_1-抗胰蛋白酶(α_1-AT)水平的测定,结果20~40岁组正常值为136.9mg%,41~60岁组正常值为129.3mg%,男女性别间的α_1-AT水平差异无显著意义。而两个年龄组间差异有显著意义。并对测定结果作了分型。  相似文献   
75.
目的 探讨显微外科治疗颅脑外伤后肢体痉挛状态的疗效.方法 回顾分析2006年7月至2008年7月实施的21例显微外科治疗颅脑外伤后肢体痉挛状态,根据不同病例采用相应的选择性周围神经部分切断术,包括:胫神经、肌皮神经、正中神经、尺神经和腰骶段脊神经后根,共计50个肢体.结果 术后随访2~24个月,全部患者术后立即感相应肢体痉挛状态缓解,随访期间缓解率为98%(49/50).随访期间运动功能改善率为86%(18/21),生活质量提高率为95%(20/21).术后发生肢体麻木、疼痛等感觉异常26个(52%),肌力下降18个(36%),随访期间均见好转.术后痉挛状态复发1个(2%).结论 选择性周围神经部分切断术是治疗颅脑外伤后肢体痉挛状态安全有效的方法.选择适应证及手术时机和术后坚持康复训练是保证疗效的关键.  相似文献   
76.
The mechanisms underlying neurologic deficits and delayed neuronal death after ischemia are not fully understood. In the present study, we report that transient cerebral ischemia induces accumulation of ubiquitinated proteins (ubi-proteins) in postsynaptic densities (PSDs). By immunoelectron microscopy, we demonstrated that ubi-proteins were highly accumulated in PSD structures after ischemia. On Western blots, ubi-proteins were markedly increased in purified PSDs at 30 minutes of reperfusion, and the increase persisted until cell death in the CA1 region after ischemia. In the resistant DG area, however, the changes were transient and significantly less pronounced. Deposition of ubi-proteins in PSDs after ischemia correlates well with PSD structural damage in the CA1 region as viewed by electron microscopy. These results suggest that the ubiquitin-proteasome system fails to repair and remove damaged proteins in PSDs. The changes may demolish synaptic neurotransmission, contribute to neurologic deficits, and eventually lead to delayed neuronal death after transient cerebral ischemia.  相似文献   
77.
T lymphocytes play a fundamental role in the initiation and regulation of chronic inflammatory responses in patients with asthma. CD69 is an early marker of T‐cell activation. The levels of intercellular adhesion molecule‐1 (ICAM‐1, CD54) and L ‐selectin have been reported to increase in patients with allergic diseases and asthma. The present study was therefore undertaken to investigate the expression of CD69, CD54, and L ‐selectin by T lymphocytes of children with asthma, before and after immunotherapy. Eighteen children newly diagnosed with asthma, 11 good and nine poor responders to immunotherapy, and 16 normal subjects, were enrolled in this study. The percentages of CD69+, CD54+, and CD62L+ cells in T lymphocytes were measured by using flow cytometry. The levels of CD69, CD54, and CD62L in serum and culture supernatants were determined by using enzyme‐linked immunosorbent assay (ELISA). The expression of CD69 and CD54 on CD3+ T lymphocytes was significantly higher in children with asthma than in control patients. All the patient groups expressed (spontaneously and following stimulation with phorbol myristate acetate and ionomycin together with mite‐extract proteins) greater amounts of CD69 and CD54 than did control subjects. With long‐term immunotherapy, the percentages of CD69+ and CD54+ T lymphocytes were significantly lower in patients with a good response to immunotherapy. Our results also showed significantly lower serum L ‐selectin levels following immunotherapy. In conclusion, successful immunotherapy resulted in decreased expression and production of CD69 and CD54. These results may explain, in part, the clinical efficacy of immunotherapy.  相似文献   
78.
The feasibility and early results of a new technique of outpatient proctoscopic coagulation of haemorrhoids by means of an electronic probe (Ultroid®, Microvasive Inc., USA) were evaluated in comparison to conventional injection sclerotherapy. Age, symptom and sex-matched groups were analysed before and 6 weeks after outpatient treatment, using scoring systems (n=51). A mean of 6.2±0.4 ml of phenol in oil were injected over 2.4±0.2 min compared to a mean current of 15.8 ±0.2 mA over a period of 11.9±0.8 min (p<0.001, treatment time). Sclerotherapy was found significantly less tedious than coagulation. More patients complained of discomfort during coagulation, but the difference in tolerance scores between the 2 groups was not significant. Three patients in the coagulation group but none in the injection group refused to be treated by the same method again due to discomfort. Significant benefits were achieved by both modes of treatment after 6 weeks. The early cure rates for bleeding were 84% for sclerotherapy and 64% for coagulation (p=0.2) and for prolapse 56% and 44% respectively (p=0.72). Injection sclerotherapy is preferable to Ultroid® coagulation for the outpatient treatment of haemorrhoids because it is a quicker, less tedious and more comfortable procedure with equally effective early results.
Résumé La réalisation et les premiers résultats d'une nouvelle technique de coagulation ambulatoire des hémorroïdes au moyen d'une sonde électronique (Ultroïd, Microvasive inc. USA) on été évalués par comparaison avec la sclérothérapie conventionnelle. Deux groupes appariés selon l'âge, les signes et le sexe ont été analysés avant et six semaines après un traitement ambulatoire en utilisant un score (n=51). Une moyenne de 6,2±0,4 ml d'huile phéniquée a été injectée en 2,4±0,2 mn comparée à une application de courant moyen de 15,8±0,2 mA dans une période de 11,9±0,8 mn (p<0,001, temps de traitement). La sclérothérapie a été trouvée moins pénible que la coagulation. Plus de malades se plaignaient d'inconfort durant la coagulation mais la différence de tolérance n'était pas significative entre les deux groupes. Trois malades dans le groupe de coagulation ont refusé de poursuivre le traitement en raison du disconfort contre aucun malade dans le groupe d'injection. Les résultats furent bons dans les deux groupes après six semaines. Les résultats immédiats pour les saignements étaient de 84% et de 64% pour la coagulation (p=0,2) et pour les procidences de 56% pour la scléro-thérapie contre 44% pour la coagulation (p=0,72). Les injections sclérosantes sont préférables à la coagulation Ultroid comme traitement ambulatoire des hémorroïdes car il s'agit d'un procédé plus rapide, moins pénible et plus confortable avec des résultats immédiats aussi bons.


Paper presented at the Spring Meeting of the British Society of Gastroenterology, University of Warwick, UK, March 1990  相似文献   
79.
The ability of nicotine to induce a cytoprotective or neuroprotective action occurs through several down-stream mechanisms. One possibility is that the drug increases the expression of tyrosine kinase A (TrkA) nerve growth factor (NGF) receptors. Certain β-amyloid peptides (e.g., Aβ1–42) have been shown to bind with high affinity to α7 nicotinic receptors and thus interfere with a potentially neurotrophic influence. Treatment of differentiated PC-12 cells with nicotine produced a concentration-dependent increase in cell-surface TrkA receptors that occurred concomitantly with cytoprotection. The effect of nicotine was blocked by either of the α7 receptor antagonists α-bungarotoxin (α-BTX) or methyllycaconatine. The cytoprotective action of nicotine also was inhibited by pretreatment with 10–100 nM Aβ1–42. Nicotine also was administered (four injections of 30 μg, spaced evenly over 24 h) to rats by direct injection into a lateral cerebral ventricle. Brain TrkA expression was increased significantly in hippocampus and entorhinal cortex (up to 32% above control), with no changes found in cerebral cortex or hypothalamus. The nicotine-induced increases in TrKA expression in hippocampus and entorhinal cortex were significantly inhibited by 10 μg α-BTX or by 10 nmol Aβ1–42. Therefore, physiologically relevant concentrations of Aβ1–42 can prevent nicotine-induced TrkA receptor expression in brain regions containing cholinergic neurons susceptible to the neurotoxicity associated with Alzheimer’s disease.  相似文献   
80.
目的 解决南方红豆杉细胞生长缓慢及代谢水平低下的问题。方法 对对数期(20d)和静止期(30d)的红豆杉细胞分别进行继代,在整个生长周期中测定了培养基中的碳源、氮源、磷酸盐的变化并分析了红豆杉细胞生长及紫杉醇的合成情况。结果 对数期继代细胞吸收碳源和硝态氮早于静止期继代的细胞,且前者的比生长速度是后者的1.5倍,紫杉醇含量提高了近4倍。结论 对数期继代有利于生物量的积累及紫杉醇的合成。  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