首页 | 官方网站   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   2940篇
  免费   229篇
  国内免费   24篇
医药卫生   3193篇
  2024年   1篇
  2023年   53篇
  2022年   41篇
  2021年   130篇
  2020年   95篇
  2019年   136篇
  2018年   153篇
  2017年   103篇
  2016年   117篇
  2015年   161篇
  2014年   191篇
  2013年   202篇
  2012年   295篇
  2011年   320篇
  2010年   167篇
  2009年   124篇
  2008年   165篇
  2007年   160篇
  2006年   142篇
  2005年   99篇
  2004年   83篇
  2003年   86篇
  2002年   77篇
  2001年   10篇
  2000年   3篇
  1999年   7篇
  1998年   7篇
  1997年   7篇
  1996年   7篇
  1995年   4篇
  1994年   5篇
  1993年   6篇
  1991年   1篇
  1990年   2篇
  1989年   3篇
  1988年   5篇
  1987年   4篇
  1986年   2篇
  1985年   3篇
  1983年   4篇
  1982年   1篇
  1980年   1篇
  1975年   1篇
  1973年   3篇
  1969年   1篇
  1968年   1篇
  1964年   1篇
  1957年   1篇
  1955年   1篇
  1924年   1篇
排序方式: 共有3193条查询结果,搜索用时 15 毫秒
1.
2.
The prevalence of bad self-rated health (SRH) varies considerably across countries. Here we present the results of a cross-national comparative study based on the data of National Health Surveys conducted in France and Italy. According to these data, 11% of the Italian and 6% of the French adult population aged between 45 and 74 rate their health as bad or very bad. This gap may result from differences in population structure regarding the individual characteristics (sociodemographic characteristics, diseases and disabilities, lifestyle, and others) that impact on SRH i.e., a structural effect. It may also be that the link between these characteristics and SRH is “country-specific” i.e., a contextual effect. We use logistic regression models to assess the contribution of both explanations. We find that the structural effect plays a prominent role in the higher prevalence of bad SRH in Italy compared to France.  相似文献   
3.
4.
A total of 15 mixtures involving 9 different stocks attributed to the 19/20, 32 and 39 major clonal genotypes of Trypanosoma cruzi were used to infect third-instar nymphs of Triatoma infestans via an artificial feeding device. Three biological parameters were considered: (1) the percentage of infected insects (%II), (2) the number of flagellates per insect (NFI), and (3) the percentage of trypomastigotes per insect (%DIF). Genetic characterization by both multilocus enzyme electrophoresis (MLEE) and random amplification of polymorphic DNA (RAPD) indicated that in almost all cases (87%), mixtures remained present after completion of the whole cycle in the insect vector. Two lines of comparison were performed: (1) pure clonal genotypes versus corresponding mixed clonal genotypes and (2) the␣actual behavior of mixed clonal genotypes versus the expected behavior of the theoretical mixture (i.e. the␣arithmetic mean of the results observed for each of the two clonal genotypes taken separately). Statistical analyses of the variables were made difficult because of the presence of large standard deviations. Nevertheless, in several cases, mixtures differed significantly from pure clonal genotypes, and in one case the actual mixture differed significantly from the theoretical mixture. In some cases, interaction (either potentialization or reciprocal inhibition) could be suspected. Received: 10 March 1997 / Accepted: 21 September 1997  相似文献   
5.
A number of cytolytic T lymphocyte (CTL) clones derived from several melanoma patients have been found to recognize a majority of melanomas from HLA-A2 patients. We have reported previously that two such CTL clones recognize a product of the tyrosinase gene that is presented by HLA-A2. Here we show that one of these CTL clones recognizes a peptide encoded by the first nine amino acids of the putative signal sequence of tyrosinase. The other CTL clone recognizes a different tyrosinase peptide corresponding to amino acids 368–376. Both peptides contain consensus motifs of HLA-A2 binding peptides.  相似文献   
6.
Summary We have previously shown that a non-classical 5-hydroxytryptamine (5-HT4) receptor mediates the stimulation of adenylate cyclase activity in mouse embryo colliculi neurons in primary culture. The pharmacological characteristics of this receptor exclude the possibility that it belongs to the known 5-HT1, 5-HT2 or 5-HT3 receptor types. Here we report that this 5-HT receptor can be stimulated by 4-amino-5-chloro-2-methoxy substituted benzamide derivatives. All these compounds have been reported to be potent stimulants of gastrointestinal motility and some of them are 5-HT3 receptor antagonists. The rank order of potency of these substituted benzamide derivatives in stimulating cAMP formation was: cisapride > BRL 24924 > 5-HT > zacopride > BRL 20627 > metoclopramide. The non-additivity of benzamide and 5-HT activities suggests that 5-HT and the substituted benzamide derivatives act on the same receptor. Only ICS 205930, a recognized 5-HT3 receptor antagonist, competitively antagonized the stimulatory effect of cisapride, zacopride and BRL 24924. However, its pK i (6–6.3) for this new receptor was very different from its pK i for 5-HT3 receptors (pK i = 8 –10). Other selective 5-HT3 receptor antagonists with an indole group (BRL 43694 and GR 38032F), with a benzoate group (cocaïne, MDL 72222) or with a piperazine group (quipazine) were ineffective in reversing the stimulatory effect of benzamide derivatives. Exposure of neuronal cells to potent agonists at this receptor such as BRL 24924 rapidly reduces its capacity to stimulate cAMP production. For example, a preincubation of 10 min with BRL 24924 (100 mol/l) reduced by 42% the ability of 5-HT to stimulate cAMP production. Cross-desensitization occurs between the effects of 5-HT and benzamides. The unique pharmacology of these nonclassical 5-HT receptors that we propose to call 5-HT4 is very close and even identical to the pharmacology of the high affinity 5-HT receptors involved in the indirect stimulation of smooth muscle in the guinea pig ileum. These receptors are different from the 5-HT3 receptors also present in guinea pig ileum.Send offprint requests to A. Dumuis at the above address  相似文献   
7.
An allergic agranulocytosis induced by amidopyrine and triggered by noramidopyrine was studied. Leucoagglutinating and leucocytotoxic antibody, active only in the presence of the drug, was demonstrated. The antibody was stable, giving a titre from 1·34 to 1·62 and was present in the IgM (19S globulin) and in the IgG (7S globulin) serum fractions. The site of drug fixation was studied by use of iodoantipyrine labelled with 131I; a stable fixation was demonstrated on to the IgM and IgG globulins. Special emphasis is given to cross-reaction with compounds related to amidopyrine.  相似文献   
8.
Fifty-three families with at least one IDD patient were genotyped for 5 markers of the HLA complex including Bf and DR. In 8 families one of the parents was also affected and in 12 families more than two children were diseased. In total, 76 patients were genotyped. Their haplotypes were compared with those of 106 unrelated controls (the parents of 53 genotyped families).
  • 1) 

    Three haplotypes or segments of them (A2, Cw3, B15, BfS, DR4; Aw30, Cw5, B18, BfF I, DR3; and Al, Cw7, B8, BfS, DR3) were found more frequently in IDD patients.

  • 2) 

    Measured by the 6 formula, the association of the postulated IDD susceptibility gene was very strong with the D-end of two of these haplotypes: BfF1, DR3 and BfS, DR4. However, the association was weak with the DR3 of the haplotype Al, Cw7, B8, BfS, DR3.

  • 3) 

    An excess of HLA-identical affected siblings was found.

  • 4) 

    An excess of DR3/DR4 heterozygotes was observed. By contrast, the observed frequency of patients homozygous for DR3 or DR4 was not increased, but even slightly decreased.


The data support a model of inheritance comprising at least two closely linked specifically "diabetic" loci (most of the time marked by B18, BfFl, DR3 and B15, BfS, DR4) and a non-specifically "diabetic" haplotype favouring auto-immunisation (most of the time marked by B8, BfS, DR3). This model is discussed in the light of the presented data and of those of the literature.  相似文献   
9.
10.
In a previous study we demonstrated that MG-63 cells cultured on Ti-6Al-4V discs covered by alumina ceramic and submitted to intermittent mechanical strain (IMS) presented morphological alteration associated with enhanced differentiation. Here we examine how the mechanical response of osteoblasts can be modulated by the nature of the substrate. MG-63 cells were cultured on four materials: polystyrene and Ti-6Al-4V (average roughness = 0.48 microm) as smooth substrates; Ti-6Al-4V (average roughness = 5.76 microm) and Ti-6Al-4V covered with alumina (average roughness = 5.21 microm) as rough substrates. Mechanical strains were applied for 15 min, three times a day for 1-5 days with a 600 microstrains magnitude and a 0.25 Hz frequency. IMS stimulated alkaline phosphatase activity by 25-35% on all substrates and had no effect on cell growth on either substrate. Fibronectin (FN) was chosen as representative of cell-matrix interaction. FN production was increased by 60% after 1 day of stretching only on alumina-coated discs. FN organization examined on smooth substrates was affected by 5 days of IMS, showing a thickening of the fibres. The same modifications induced by IMS were previously observed on alumina-covered discs. Vinculin expression was not affected by IMS whatever the substrate. Cell-cell interactions were determined by N-cadherin immunoblotting. N-cadherin expression was increased by IMS specifically on rough substrates. Our results suggest that the nature of the surface did not influence the up-regulation of alkaline phosphatase activity induced by IMS, but modulates specifically cell-substrate as well as cell-cell interactions in response to IMS.  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-23

京公网安备 11010802026262号