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   3654篇
  免费   141篇
  国内免费   38篇
耳鼻咽喉   104篇
儿科学   193篇
妇产科学   127篇
基础医学   881篇
口腔科学   47篇
临床医学   238篇
内科学   749篇
皮肤病学   58篇
神经病学   85篇
特种医学   32篇
外科学   283篇
综合类   229篇
预防医学   282篇
眼科学   59篇
药学   257篇
  1篇
中国医学   118篇
肿瘤学   90篇
  2024年   9篇
  2023年   70篇
  2022年   137篇
  2021年   171篇
  2020年   112篇
  2019年   208篇
  2018年   219篇
  2017年   141篇
  2016年   104篇
  2015年   111篇
  2014年   279篇
  2013年   226篇
  2012年   166篇
  2011年   256篇
  2010年   133篇
  2009年   147篇
  2008年   127篇
  2007年   150篇
  2006年   93篇
  2005年   98篇
  2004年   86篇
  2003年   73篇
  2002年   70篇
  2001年   43篇
  2000年   30篇
  1999年   50篇
  1998年   32篇
  1997年   29篇
  1996年   26篇
  1995年   20篇
  1994年   23篇
  1993年   22篇
  1992年   12篇
  1991年   14篇
  1990年   13篇
  1989年   10篇
  1988年   9篇
  1987年   13篇
  1985年   25篇
  1984年   19篇
  1983年   26篇
  1982年   18篇
  1981年   35篇
  1980年   29篇
  1979年   25篇
  1978年   26篇
  1977年   24篇
  1976年   28篇
  1975年   13篇
  1974年   12篇
排序方式: 共有3833条查询结果,搜索用时 46 毫秒
991.
992.
Component-resolved diagnosis based on the use of well-defined, properly characterised and purified natural and recombinant allergens constitutes a new approach in the diagnosis of venom allergy. Prospective readers may benefit from an up-to-date review on the allergens. The best characterised venom is that of Apis mellifera, whose main allergens are phospholipase A2 (Api m1), hyaluronidase (Api m2) and melittin (Api m4). Additionally, in recent years, new allergens of Vespula vulgaris have been identified and include phospholipase A1 (Ves v1), hyaluronidase (Ves v2) and antigen 5 (Ves v5). Polistes species are becoming an increasing cause of allergy in Europe, although only few allergens have been identified in this venom.In this review, we evaluate the current knowledge about molecular diagnosis in hymenoptera venom allergy.  相似文献   
993.
ABSTRACT

Exposure to diesel exhaust particles (DEP) is an environmental and occupational health concern. This review examines the cellular actions of the organic and the particulate components of DEP in the development of various lung diseases. Both the organic and the particulate components cause oxidant lung injury. The particulate component is known to induce alveolar epithelial damage, alter thiol levels in alveolar macrophages (AM) and lymphocytes, and activate AM in the production of reactive oxygen species (ROS) and pro-inflammatory cytokines. The organic component, on the other hand, is shown to generate intracellular ROS, leading to a variety of cellular responses including apoptosis. There are a number of differences between the biological actions exerted by these two components. The organic component is responsible for DEP induction of cytochrome P450 family 1 enzymes that are critical to the polycyclic aromatic hydrocarbons (PAH) and nitro-PAH metabolism in the lung as well as in the liver. The particulate component, on the other hand, causes a sustained down-regulation of CYP2B1 in the rat lung. The significance of this effect on pulmonary metabolism of xenobiotics and endobiotics remains to be seen, but may prove to be an important factor governing the interplay of the pulmonary metabolic and inflammatory systems. Long-term exposures to various particles including DEP, carbon black (CB), TiO2, and washed DEP devoid of the organic content, have been shown to produce similar tumorigenic responses in rodents. There is a lack of correlation between tumor development and DEP chemical-derived DNA adduct formation. But the organic component has been shown to generate ROS that produce 8-hydroxydeoxyguanosine (8-OHdG) in cell culture. The organic, but not the particulate, component of DEP suppresses the production of pro-inflammatory cytokines by AM and the development of Th1 cell-mediated immunity. The mechanism for this effect is not yet clear, but may involve the induction of heme oxygenase-1 (HO-1), a cellular genetic response to oxidative stress. Both the organic and the particulate components of DEP enhance respiratory allergic sensitization. Part of the DEP effects may be due to a depletion of glutathione in lymphocytes. The organic component, which is shown to induce IL-4 and IL-10 productions, may skew the immunity toward Th2 response, whereas the particulate component may stimulate both the Th1 and Th2 responses. In conclusion, the literature shows that the particulate and organic components of DEP exhibit different biological actions but both involve the induction of cellular oxidative stress. Together, these effects inhibit cell-mediated immunity toward infectious agents, exacerbate respiratory allergy, cause DNA damage, and under long-term exposure, induce the development of lung tumors.  相似文献   
994.
IntroductionThere are rather few publications about hypersensitivity reactions to non-steroidal anti-inflammatory drugs (NSAID) in the paediatric age. In this study, we aimed to assess the frequency of confirmed NSAID hypersensitivity in children with a previous reported reaction to NSAID in order to investigate the role of the drug provocation test (DPT) in the diagnostic workup and to explore the factors associated with confirmed NSAID hypersensitivity.MethodsWe conducted a retrospective analysis of the clinical files from every patient under 18 years old who attended two Portuguese paediatric allergy outpatient clinics, from January 2009 to August 2014, due to a suspected NSAID hypersensitivity.ResultsWe included 119 patients, with a median age of nine years (P25–P75: 5–14). Ibuprofen was the commonest implicated NSAID in the patients’ reports (n = 94–79%). After DPT, NSAID hypersensitivity was confirmed in nine (7.6%) patients, excluded in 93 (78.2%) and was inconclusive in 17 (14.3%). In the majority (n = 95–79.8%), the reaction occurred in the first 24 h after intake. Eighty-four patients (70.6%) reported only cutaneous manifestations and 18 (15.1%) had systemic symptoms. Anaphylaxis represented a relative risk to NSAID hypersensitivity confirmation. No association was found for atopy and the number of previous reactions.ConclusionIn our study, NSAID hypersensitivity was confirmed in a small proportion of the patients with a previous reported reaction. Ibuprofen was the most implicated drug with urticaria/angio-oedema as the commonest manifestation. Anaphylaxis was associated with confirmed drug hypersensitivity. The drug provocation test was essential to establish the diagnosis.  相似文献   
995.
996.
目的了解鸡减蛋综合征病毒(EDSV)的基因结构特征。方法从中国发病鸡群中分离的鸡减蛋综合征病毒弱毒株AA2,经常规法提取病毒核酸后,构建了用内切酶HindⅢ水解的完整基因文库,对其中A片段编码55K蛋白基因的核苷酸序列进行测定和分析。结果该读码框共1011个核苷酸,编码产物由337氨基酸组成,分子量为38200。氨基酸同源性分析表明,EDSV55K蛋白与人腺病毒(Ad2,Ad12,Ad40)、犬腺病毒(cav)、Ⅰ群禽腺病毒(celo)同源性在255%~324%之间,而与羊腺病毒(oav)的同源性达到464%。结论EDSV55K蛋白基因具有与腺病毒55K蛋白基因相似的结构,但变异较大。  相似文献   
997.
Objective: To investigate if the development of allergic diseases during the child’s first 18 months of life is influenced by the time at which different food items were introduced into the child’s diet. Method: A birth cohort of 184 children was followed to 18 months of age. Diaries were used to document feeding practices, and parental interviews were performed at 6 and 12 months of age, probing for symptoms suggesting allergic disease, general health‐related issues and food introduction regimes. Symptoms promoted prompt clinical examination, and all children were examined clinically, and tested for sensitization to common airborne and food allergens at 18 months of age. Results: The earlier the fish was introduced into the child’s diet the lower was the frequency of eczema. This association remained after control for confounding factors. The timing of fish introduction and asthma development showed a similar pattern, but did not reach statistical significance. Sensitization was not influenced by the timing of fish introduction. Other food items or feeding practices did not seem to influence allergy development. Conclusion: Early introduction of fish into the child’s diet was associated with less eczema development, and a tendency to less asthma. Sensitization was not associated with the timing of fish introduction.  相似文献   
998.
In this work, we consider the parametric estimation of quality adjusted lifetime (QAL) distribution in progressive illness–death models. The main idea of this paper is to derive the theoretical distribution of QAL for the progressive illness–death models, under parametric models for the sojourn time distributions in different states, and then replace the model parameters by their estimates obtained by standard techniques of survival analysis. The method of estimation of the model parameters is also described. A data set of IBCSG Trial V has been analyzed for illustration. Extension to more general illness–death models is also discussed. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
999.
AIM OF THE STUDY: Initially, we performed a questionnaire study on 622 school children aged 7 to 13 y. The study was supplemented with a clinical study including skin prick tests to 13 molds in 212 (34%) children with doctor-diagnosed asthma or parental-reported wheezing or prolonged cough. These children were attending one of two elementary schools, one with moisture problems (index) school, the other being the control school. The objective of the study was to evaluate whether exposure to moisture and sensitization to molds are associated with respiratory manifestations in school children. RESULTS: The prevalence of asthma was 4.8%, which was similar in the children from both schools. The children from the index school more often had wheezing (16% vs 6%; p <0.001) and cough (21% vs 9%: p < 0.001) symptoms than control children. Positive skin reactions to molds were rare (2.4%), being present in 7% of asthmatic and in 1-2% of non-asthmatic children (NS). Lower respiratory tract infections were more common in the spring than in the fall in children from the index school, but not in control children, and the difference between the schools was significant in emergency visits (OR =2.0, p <0.01) and antibiotic courses (OR = 2.1, p < 0.01). CONCLUSIONS: We found evidence of an association between moisture or mold problems in the school building and the occurrence of respiratory infections, repeated wheezing and prolonged cough in school children.  相似文献   
1000.
Stiripentol: efficacy and tolerability in children with epilepsy   总被引:4,自引:2,他引:2  
Perez J  Chiron C  Musial C  Rey E  Blehaut H  d'Athis P  Vincent J  Dulac O 《Epilepsia》1999,40(11):1618-1626
PURPOSE: Stiripentol (STP) is a new antiepileptic drug (AED) that inhibits cytochrome P450, resulting in increased plasma concentrations of concomitant AEDs. The efficacy and tolerability of STP as an add-on therapy in children were assessed. METHODS: Two hundred twelve patients with refractory epilepsy, aged from 1 month to 20.5 years, received STP either in a single-blind, placebo-controlled trial (108 patients) or in a further open trial (104 other patients selected by epilepsy syndrome for possible efficacy based on the results of the previous trial). RESULTS: Among the 97 patients who could be analyzed for efficacy in the placebo-controlled study, the median seizure frequency was lower at 3 months with STP than with the placebo (p<0.0001); 49% responded to the drug, including 10% who became seizure free. Patients with partial epilepsy had the highest response rate (57%). Results were confirmed in the open study where 68% of the 91 patients receiving STP responded at 3 months. These patients were mainly those with partial epilepsy (73%) who were receiving carbamazepine (CBZ) (75%) as comedication (p<0.001). Ten of the 20 children with severe myoclonic epilepsy in infancy also responded with clobazam (CLB) as comedication. Efficacy was sustained long term in 74% of the 94 patients still receiving STP at a mean 30-month follow-up. Adverse events were reported in 48% of the 212 patients, mainly anorexia and loss of weight, but these events required STP discontinuation in only nine cases. Side effects were minimized in the open trial by optimizing the dose of comedication. CONCLUSIONS: STP seems to be a promising add-on drug, particularly when combined with CBZ in patients with partial childhood epilepsy refractory to vigabatrin (VGB) and with CLB in patients with severe myoclonic epilepsy in infancy.  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