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   4041篇
  免费   328篇
  国内免费   24篇
耳鼻咽喉   35篇
儿科学   147篇
妇产科学   61篇
基础医学   732篇
口腔科学   32篇
临床医学   457篇
内科学   862篇
皮肤病学   68篇
神经病学   476篇
特种医学   75篇
外科学   445篇
综合类   14篇
一般理论   2篇
预防医学   363篇
眼科学   42篇
药学   276篇
中国医学   9篇
肿瘤学   297篇
  2023年   38篇
  2022年   44篇
  2021年   101篇
  2020年   60篇
  2019年   102篇
  2018年   111篇
  2017年   72篇
  2016年   81篇
  2015年   105篇
  2014年   154篇
  2013年   203篇
  2012年   311篇
  2011年   343篇
  2010年   171篇
  2009年   171篇
  2008年   292篇
  2007年   285篇
  2006年   283篇
  2005年   280篇
  2004年   259篇
  2003年   280篇
  2002年   220篇
  2001年   30篇
  2000年   18篇
  1999年   32篇
  1998年   40篇
  1997年   51篇
  1996年   32篇
  1995年   23篇
  1994年   31篇
  1993年   34篇
  1992年   9篇
  1991年   15篇
  1990年   12篇
  1989年   10篇
  1988年   5篇
  1987年   4篇
  1986年   12篇
  1985年   3篇
  1984年   10篇
  1983年   4篇
  1982年   7篇
  1981年   6篇
  1980年   7篇
  1979年   3篇
  1978年   4篇
  1977年   4篇
  1973年   2篇
  1972年   2篇
  1971年   6篇
排序方式: 共有4393条查询结果,搜索用时 46 毫秒
31.
The recombination events of the γ and β T-cell receptor (TCR) loci were analysed in a series of 39 peripheral T-cell lymphomas (PTCLs) in association with the expression of TCR chains. In TCR αβ PTCLs, 22/23 cases showed a γ-gene rearrangement while only 18/23 showed a concomitant β-gene rearrangement. The germline configuration of the β locus was found in angioimmunoblastic lymphadenopathy and lymphoepithelioid lymphomas. Three γδ PTCLs rearranged both γ and β genes. TCR silent PTCLs showed three different patterns of γ- and β-gene rearrangements. Three cases were in germline configuration for both loci; five cases had a rearranged γ and a germline β locus; and five cases had the two loci rearranged. Regarding the variable genes in the γ-rearranged alleles, members of the VγI subgroup were the most frequently presented (39/50), followed by VγII, VγIII, and VγIV (9/50, 1/50, and 1/50, respectively). Joining segment usage was as follows: J1 or J2 (32/50), JP1 or JP2 (17/50), and JP (1/50). Taken together, these data demonstrate that the γ locus is more frequently rearranged whatever the TCR expression. The γ-locus analysis provides a better diagnostic yield than the β locus in the study of PTCL clonality.  相似文献   
32.
We have tested the involvement of the invariant chains (Ii) p31 and p41 in the presentation of peptides derived from hen egg lysozyme (HEL) constructs targeted to different intracellular compartments within transfected fibroblasts. The endogenous HEL constructs were either present in the cytosol (HELc), secreted (HELs), or linked to the mammalian (KDEL C-terminal sequence that causes retention of HEL in the endoplasmic reticulum (ER)/pre-Golgi recycling compartment (HELr). Using Ii-negative antigen-presenting cells, the presentation of HELr to a HEL 46-61 specific T cell hybridoma was far less efficient than the presentation of the HELs. High levels of Ii expression enhanced drastically the presentation of the HEL 46-61 determinant derived from both HELr and HELs. HELr and HELs presentation was fully sensitive to lysosomotropic agents such as chloroquine, indicating that the formation of complexes between major histocompatibility complex (MHC) class II molecules and determinants derived from endogenous antigens entering the secretory pathway is taking place in an acidic compartment. The degradation and dissociation of Ii might be a prerequisite for the efficient presentation of endogenously derived determinants by MHC class II molecules, as for the presentation of most exogenous antigens. All our results are compatible with the notion that endogenous molecules being translocated into the lumen of the ER could be presented by class II molecules through a processing pathway involving an acidic compartment in which Ii chains dissociate from class II molecules.  相似文献   
33.
We detected 3 genotypes of highly pathogenic avian influenza A(H5N8) virus in France during winter 2016–17. Genotype A viruses caused dramatic economic losses in the domestic duck farm industry in southwestern France. Our phylogenetic analysis suggests that genotype A viruses formed 5 distinct geographic clusters in southwestern France. In some clusters, local secondary transmission might have been started by a single introduction. The intensity of the viral spread seems to correspond to the density of duck holdings in each production area. To avoid the introduction of disease into an unaffected area, it is crucial that authorities limit the movements of potentially infected birds.  相似文献   
34.
Bone geometry can be described in terms of periosteal and endocortical growth and is partly determined by sex steroids. Periosteal and endocortical apposition are thought to be regulated by testosterone and estrogen, respectively. Gender-affirming hormone (GAH) treatment with sex steroids in transgender people might affect bone geometry. However, in adult transgender people, no change in bone geometry during GAH was observed. In this study, we investigated changes in bone geometry among transgender adolescents using a gonadotropin-releasing hormone agonist (GnRHa) and GAH before achieving peak bone mass. Transgender adolescents treated with GnRHa and subsequent GAH before the age of 18 years were eligible for inclusion. Participants were grouped based on their Tanner stage at the start of GnRHa treatment and divided into early, mid, and late puberty groups. Hip structure analysis software calculating subperiosteal width (SPW) and endocortical diameter (ED) was applied to dual-energy X-ray absorptiometry scans performed at the start of GnRHa and GAH treatments, and after ≥2 years of GAH treatment. Mixed-model analyses were performed to study differences over time. Data were visually compared with reference values of the general population. A total of 322 participants were included, of whom 106 were trans women and 216 trans men. In both trans women and trans men, participants resembled the reference curve for SPW and ED of the experienced gender but only when GnRHa was started during early puberty. Those who started during mid and late puberty remained within the reference curve of the gender assigned at birth. A possible explanation might be sought in the phenomenon of programming, which conceptualizes that stimuli during critical windows of development can have major consequences throughout one's life span. Therefore, this study adds insights into sex-specific bone geometry development during puberty of transgender adolescents treated with GnRHa, as well as the general population. © 2021 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.  相似文献   
35.
ObjectivesTo examine the relationship between job strain and incident myocardial infarction and congestive heart failure in a representative population of men and women in Ontario, Canada, over a 15-year period.MethodsA total of 14,508 respondents having provided responses to either the 2000/2001, 2002, or 2003 cycles of the Canadian Community Health Survey (CCHS) were aged 35 and older at the time and working. After removing respondents with pre-existing heart disease and missing data, our sample totaled 13,291 respondents. Responses were linked to administrative health care and hospitalization data to capture incident cases of myocardial infarction and congestive heart failure up to March 31, 2017. Job control and psychological demands were assessed using 5 items and 2 items respectively. A series of time-to-event regression models were run, adjusting sequentially for socio-demographic variables and health, other psychosocial work exposures, and health behaviours and body mass index.ResultsOver the study period, there were 199,583 person-years of follow-up (median follow-up: 15 years, 233 days). Higher incidence rates were observed for men (6.69 per 100 persons) than for women (2.77 per 100 persons). No clear relationship was observed for demand-control exposures and incidence of myocardial infarction and congestive heart failure in either men or women. After adjustment for socio-demographic factors, pre-existing health conditions, and other psychosocial exposures, the hazard ratio for high strain exposure (compared with low strain exposure) was 0.92 (0.46–1.84) for women and 0.75 (0.44–1.27) for men.ConclusionIn this large prospective cohort in Canada, we observed no relationship between components of the demand-control model and incident myocardial infarction and congestive heart failure over a 15-year period.  相似文献   
36.
Clémence Jacquin  Emilie Landais  Céline Poirsier  Alexandra Afenjar  Ahmad Akhavi  Nathalie Bednarek  Caroline Bénech  Adeline Bonnard  Damien Bosquet  Lydie Burglen  Patrick Callier  Sandra Chantot-Bastaraud  Christine Coubes  Charles Coutton  Bruno Delobel  Margaux Descharmes  Jean-Michel Dupont  Vincent Gatinois  Nicolas Gruchy  Sarah Guterman  Abdelkader Heddar  Lucas Herissant  Delphine Heron  Bertrand Isidor  Pauline Jaeger  Guillaume Jouret  Boris Keren  Paul Kuentz  Cedric Le Caignec  Jonathan Levy  Nathalie Lopez  Zoe Manssens  Dominique Martin-Coignard  Isabelle Marey  Cyril Mignot  Chantal Missirian  Céline Pebrel-Richard  Lucile Pinson  Jacques Puechberty  Sylvia Redon  Damien Sanlaville  Marta Spodenkiewicz  Anne-Claude Tabet  Alain Verloes  Gaelle Vieville  Catherine Yardin  François Vialard  Martine Doco-Fenzy 《American journal of medical genetics. Part A》2023,191(2):445-458
Chromosome 1p36 deletion syndrome (1p36DS) is one of the most common terminal deletion syndromes (incidence between 1/5000 and 1/10,000 live births in the American population), due to a heterozygous deletion of part of the short arm of chromosome 1. The 1p36DS is characterized by typical craniofacial features, developmental delay/intellectual disability, hypotonia, epilepsy, cardiomyopathy/congenital heart defect, brain abnormalities, hearing loss, eyes/vision problem, and short stature. The aim of our study was to (1) evaluate the incidence of the 1p36DS in the French population compared to 22q11.2 deletion syndrome and trisomy 21; (2) review the postnatal phenotype related to microarray data, compared to previously publish prenatal data. Thanks to a collaboration with the ACLF (Association des Cytogénéticiens de Langue Française), we have collected data of 86 patients constituting, to the best of our knowledge, the second-largest cohort of 1p36DS patients in the literature. We estimated an average of at least 10 cases per year in France. 1p36DS seems to be much less frequent than 22q11.2 deletion syndrome and trisomy 21. Patients presented mainly dysmorphism, microcephaly, developmental delay/intellectual disability, hypotonia, epilepsy, brain malformations, behavioral disorders, cardiomyopathy, or cardiovascular malformations and, pre and/or postnatal growth retardation. Cardiac abnormalities, brain malformations, and epilepsy were more frequent in distal deletions, whereas microcephaly was more common in proximal deletions. Mapping and genotype–phenotype correlation allowed us to identify four critical regions responsible for intellectual disability. This study highlights some phenotypic variability, according to the deletion position, and helps to refine the phenotype of 1p36DS, allowing improved management and follow-up of patients.  相似文献   
37.
Sixteen prepubertal patients with chronic renal failure (CRF) were given daily recombinant human growth hormone (rhGH) treatment (1.2 IU/kg per week) for 2.6±1.6 years until kidney transplant. Therapy was then discontinued and the patients followed for a further 3.5±1.4 years. During treatment, mean height increased from –3.0±0.9 standard deviation score (SDS) to –1.9±1.4 SDS (P<0.001) at the time of transplantation, corresponding to a mean height gain of +1.2±0.9 SDS. After discontinuation of rhGH therapy, prepubertal children continued a partial catch-up growth with a height gain of +0.5±0.8 SDS for the follow-up period. Conversely, negative changes of height were observed in pubertal transplanted children: –0.5±0.4 SDS in patients grafted at early stages of puberty (P2–P3) and –0.15±0.9 SDS in patients grafted at late stages of puberty (P4–P5). These data confirmed the benefit of rhGH therapy in CRF patients. Nevertheless, only early initiation of rhGH treatment led some of these patients to their target height at transplantation, thus preserving their potential growth. Reinitiation of rhGH therapy after transplantation should be considered in order to complete catch-up growth to target height in prepubertal children. Received: 23 July 1998 / Revised: 8 December 1998 / Accepted: 13 December 1998  相似文献   
38.
Vinflunine (VFL) is a novel derivative of vinorelbine (NVB, Navelbine®), which has shown markedly superior antitumor activity to NVB, in various experimental animal models. To establish whether this new Vinca alkaloid participates in P-glycoprotein (Pgp)-mediated multidrug resistance (MDR), VFL-resistant murine P388 cells (P388/VFL) were established in vivo and used in conjunction with the well established MDR P388/ADR subline, to define the in vivo resistance profile for VFL. P388/VFL cells proved cross-resistant to drugs implicated in MDR (other Vinca alkaloids, doxorubicin, etoposide), but not to campothecin or cisplatin and showed an increased expression of Pgp, without any detectable alterations in topoisomerase II or in glutathione metabolism. The P388/ADR cells proved cross-resistant to VFL both in vivo and in vitro, and this VFL resistance was efficiently modulated by verapamil in vitro. Cellular transport experiments with tritiated-VFL revealed differential uptake by P388 sensitive and P388/ADR resistant cells, comparable with data obtained using tritiated-NVB. In various in vitro models of human MDR tumor cells, whilst full sensitivity was retained in cells expressing alternative non-Pgp-mediated MDR mechanisms, cross resistance was identified in Pgp-overexpressing cells. Differences were, however, noted in terms of the drug resistance profiles relative to the other Vincas, with tumor cell lines proving generally least cross-resistant to VFL. Overall, these results suggest that VFL, like other Vinca alkaloids, participates in Pgp-mediated MDR, with tumor cells selected for resistance to VFL overexpressing Pgp, yet MDR tumor cell lines proved generally less cross resistant to VFL relative to the other Vinca alkaloids.  相似文献   
39.

Purpose

The usefulness of the expression of HER2/neu oncoprotein and of p53 and Rb suppressor gene product as predictors of tumor recurrence was evaluated by using a bank of prospectively collected primary papillary bladder tumors treated initially only by transurethral resection.

Materials and Methods

The expression of HER-2/neu oncoprotein and of p53 and Rb suppressor genes was evaluated by immunohistochemistry in 256, 265 and 74 specimens of primary Ta/T1 superficial bladder tumors obtained from patients enrolled in a prospective study from 1990 to 1992. Survival analysis was used to evaluate the association between time to first recurrence and expression of each marker, the follow-up period extending to March 1994. Immunostaining for p53 and HER-2/neu was performed on paraffin-embedded tissue and, for Rb, on frozen tissue only.

Results

Her-2/neu was expressed in 21 (8.2 percent) cases and p53 in 39 cases (14.7 percent); Rb expression was altered in 12 (16.2 percent). In this study, p53 expression was only related to earlier recurrence in a univariate analysis. Multivariate analysis, however, failed to recognize p53 expression as an independent predictor of recurrence.

Conclusions

Our study demonstrate the low prevalence of HER2/neu, p53 and altered Rb expression in superficial TCC at initial resection. Only p53 expression was significantly associated with an earlier first tumor recurrence, but this association was not independent of other prognostic factors.  相似文献   
40.
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