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   684篇
  免费   38篇
  国内免费   46篇
耳鼻咽喉   2篇
儿科学   47篇
妇产科学   20篇
基础医学   65篇
口腔科学   37篇
临床医学   90篇
内科学   167篇
皮肤病学   13篇
神经病学   19篇
特种医学   115篇
外科学   34篇
综合类   10篇
预防医学   19篇
眼科学   3篇
药学   97篇
  1篇
肿瘤学   29篇
  2023年   6篇
  2022年   5篇
  2021年   10篇
  2019年   8篇
  2018年   11篇
  2017年   9篇
  2016年   11篇
  2015年   16篇
  2014年   19篇
  2013年   25篇
  2012年   9篇
  2011年   12篇
  2010年   19篇
  2009年   20篇
  2008年   6篇
  2007年   39篇
  2006年   15篇
  2005年   10篇
  2004年   3篇
  2003年   4篇
  2002年   10篇
  2001年   4篇
  2000年   7篇
  1999年   12篇
  1998年   44篇
  1997年   52篇
  1996年   54篇
  1995年   44篇
  1994年   30篇
  1993年   30篇
  1992年   4篇
  1991年   16篇
  1990年   9篇
  1989年   16篇
  1988年   25篇
  1987年   23篇
  1986年   18篇
  1985年   17篇
  1984年   8篇
  1983年   9篇
  1982年   9篇
  1981年   8篇
  1980年   11篇
  1978年   8篇
  1977年   9篇
  1975年   4篇
  1970年   4篇
  1969年   3篇
  1968年   4篇
  1967年   4篇
排序方式: 共有768条查询结果,搜索用时 24 毫秒
51.
A series of 5-[(7-chloro-4-quinolinyl)amino]-3-[(alkylamino)methyl] [1,1'-biphenyl]-2-ols and N omega-oxides was prepared from the substituted 1-phenyl-2-propanones proceeding through the 5-nitro[1,1'-biphenyl]-2-ols, the corresponding amino, and acetamido derivatives to the N-[5-[(alkylamino)methyl]-6-hydroxy[1,1'-biphenyl]-3-yl]acetamides and final condensation with 4,7-dichloroquinoline or the N-oxide. In a quantitative structure-activity relationship study first run on 28 and later expanded to 40 substituted phenyl analogues and their N omega-oxides, increasing antimalarial potency vs. Plasmodium berghei in mice was found to be correlated with decreasing size (sigma MR) and electron donation (sigma sigma) of the phenyl ring substituents. A significant correlation with N omega-oxidation could not be demonstrated. Initial high activity against P. berghei infections in mice led to expanded studies that demonstrated in addition excellent activity against resistant strains of parasite, activity in primate models, and pharmacokinetic properties apparently allowing protection against infection for extended periods of time even after oral administration. Such properties encourage the clinical trial of a member of this class in man.  相似文献   
52.
Two pyrazolotetrazine derivatives were synthesized as the analogous prodrugs of the light-sensitive antineoplastic agents dacarbazine and BIC. Both the pyrazole derivatives are stable under ordinary light illumination. Biological evaluation of these pyrazoles revealed that the compound containing a 2-chloroethyl function (6a) demonstrated good antineoplastic activity in experimental animals, but the one containing a methyl function (6b) was inactive. The inactivity of compound 6b may suggest that compound 6a and related imidazotetrazines may simply act as biological alkylating agents per se rather than as prodrugs. The information could also imply that the postulated dealkylation mechanism for the triazene derivatives should be reexamined.  相似文献   
53.
Immunoadsorption for coagulation factor inhibitors   总被引:1,自引:0,他引:1  
Inhibitors to coagulation factors are among the most difficult problems in the management of coagulation disorders. Most presently available therapy does not assure hemostasis. An extracorporeal immunoadsorption system, which selectively binds IgG, was used to lower inhibitor levels in eight patients on 10 occasions. In this system, separated plasma is delivered to two staphylococcal protein A-Sepharose columns, which are coupled to an elution monitor. Columns are eluted sequentially and regenerated to maximize IgG removal. Successful removal of the inhibitor was accomplished in all six hemophiliacs on seven occasions, as well as in a patient with acquired von Willebrand disease. All patients whose inhibitors were lowered to less than 10 Bethesda units achieved measurable factor levels when factor concentrate replacement was given. Immunoadsorption facilitates efficient removal of inhibitors, which allows factor replacement therapy.  相似文献   
54.
A double-blind provocative study chocolate as a trigger of headache   总被引:1,自引:0,他引:1  
A provocative double blind study of headache was performed using chocolate as the active agent and carob as the placebo. The chocolate and carob samples were formulated to duplicate products used in an earlier study (1) in which strong differential effects between the ability of chocolate and carob to trigger headache in migraine were shown. Sixty-three women with chronic headache (50% migraine, 37.5% tension-type, 12.5% combined migraine and tension-type) participated in the study. After 2 weeks of following a diet that restricted vasoactive amine-rich foods, each subject underwent double-blinded provocative trials with two samples of chocolate and two of carob presented in random order. Diaries were maintained by the subjects throughout the study, monitoring diet and headache. The results demonstrated that chocolate was not more likely to provoke headache than was carol in any of the headache diagnostic groups (2(2) 0.36, p =0.83). Interestingly, these results were independent of subjects' beliefs regarding the role of chocolate in the instigation of headache (2(1)=0.73, p =0.39). Headache diagnosis and the concomitant use of additional vasoactive amine-containing foods were also not associated with chocolate acting as a headache trigger. Thus, contrary to the commonly held belief of patients and physicians, chocolate does not appear to play a significant role in triggering headaches in typical migraine, tension-type, or combined headache sufferers.  相似文献   
55.
56.

Background  

Oligoryzomys longicaudatus (colilargo) is the rodent responsible for hantavirus pulmonary syndrome (HPS) in Argentine Patagonia. In past decades (1967–1998), trends of precipitation reduction and surface air temperature increase have been observed in western Patagonia. We explore how the potential distribution of the hantavirus reservoir would change under different climate change scenarios based on the observed trends.  相似文献   
57.
58.
59.
ObjectiveTo investigate disparities in full immunization coverage across and within 86 low- and middle-income countries.MethodsIn May 2015, using data from the most recent Demographic and Health Surveys and Multiple Indicator Cluster Surveys, we investigated inequalities in full immunization coverage – i.e. one dose of bacille Calmette-Guérin vaccine, one dose of measles vaccine, three doses of vaccine against diphtheria, pertussis and tetanus and three doses of polio vaccine – in 86 low- or middle-income countries. We then investigated temporal trends in the level and inequality of such coverage in eight of the countries.FindingsIn each of the World Health Organization’s regions, it appeared that about 56–69% of eligible children in the low- and middle-income countries had received full immunization. However, within each region, the mean recorded level of such coverage varied greatly. In the African Region, for example, it varied from 11.4% in Chad to 90.3% in Rwanda. We detected pro-rich inequality in such coverage in 45 of the 83 countries for which the relevant data were available and pro-urban inequality in 35 of the 86 study countries. Among the countries in which we investigated coverage trends, Madagascar and Mozambique appeared to have made the greatest progress in improving levels of full immunization coverage over the last two decades, particularly among the poorest quintiles of their populations.ConclusionMost low- and middle-income countries are affected by pro-rich and pro-urban inequalities in full immunization coverage that are not apparent when only national mean values of such coverage are reported.  相似文献   
60.
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