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   13454篇
  免费   894篇
  国内免费   37篇
耳鼻咽喉   139篇
儿科学   494篇
妇产科学   366篇
基础医学   2024篇
口腔科学   200篇
临床医学   1620篇
内科学   2448篇
皮肤病学   324篇
神经病学   1629篇
特种医学   312篇
外科学   1319篇
综合类   67篇
一般理论   13篇
预防医学   1094篇
眼科学   234篇
药学   861篇
中国医学   17篇
肿瘤学   1224篇
  2023年   99篇
  2022年   182篇
  2021年   301篇
  2020年   247篇
  2019年   323篇
  2018年   365篇
  2017年   306篇
  2016年   372篇
  2015年   407篇
  2014年   502篇
  2013年   706篇
  2012年   1056篇
  2011年   1020篇
  2010年   624篇
  2009年   553篇
  2008年   858篇
  2007年   892篇
  2006年   876篇
  2005年   835篇
  2004年   761篇
  2003年   706篇
  2002年   672篇
  2001年   84篇
  2000年   50篇
  1999年   109篇
  1998年   161篇
  1997年   126篇
  1996年   98篇
  1995年   103篇
  1994年   62篇
  1993年   75篇
  1992年   46篇
  1991年   53篇
  1990年   44篇
  1989年   26篇
  1988年   34篇
  1987年   22篇
  1986年   27篇
  1985年   28篇
  1984年   29篇
  1983年   34篇
  1982年   42篇
  1981年   24篇
  1980年   33篇
  1979年   29篇
  1978年   15篇
  1977年   20篇
  1976年   27篇
  1974年   20篇
  1969年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Background: This paper is part of a prospective, epidemiologic study concerning postpartum depression (PPD). The women were first examined during pregnancy; after delivery they were seen with their infants at 3 and 18 months. The present study focuses on the 3-months-postpartum results. Methods: A sample of 570 women and their infants were examined 3 months after delivery. Using the EPDS (Edinburgh Postnatal Depression Scale; Cox et al., 1987. Br. J. Psychiatry 150:782–786), 10.2% of these new mothers presented PPD. The focus of the study concerned the effects of this neurotic disorder on the mother, the infant and on the mother–infant relationship. Results: The deleterious effects concerning the infant were functional disorders such as eating or sleeping difficulties. The ‘depressed’ dyads presented less vocal and visual communications, less corporal interactions and less smiling. Conditions surrounding delivery and tiredness at 3 months are linked to difficulties in mother–infant relationship for the non-depressed mothers. Logistic models showed that primiparous PPD mothers have difficulties bathing their infants, whereas multiparous PPD mothers are more tired. Limitation: This study did not take into account either protective factors or the effects of the infant himself. Clinical relevance: Knowledge of the mothers’ and infants’ difficulties may help caregivers to detect these at-risk dyads and initiate therapeutic measures.  相似文献   
72.
Ohne ZusammenfassungBenutzte Symbole und Abkürzungen NNR Nebennierenrinde - DOCA Desoxycorticosteronacetat - K i intracelluläres Kalium (sinngemäß für Natrium) - K a extracelluläres Kalium (sinngemäß für Natrium) - Q Ladung - E m Membranruhepotential - m Zeitkonstante der Membran - R m Membranwiderstand - C m Membrankapazität  相似文献   
73.
BACKGROUND: Enteroviruses (EV) and parechoviruses (HPeV) are the most common causes of aseptic meningitis, encephalitis and sepsis-like syndrome in neonates. Detection by nucleic acid amplification methods improves patient management. OBJECTIVE: Development of a real-time PCR assay on a LightCycler for simultaneous detection of EV, HPeV and an internal control to monitor inhibition. STUDY DESIGN: We investigated the value of the new assay, prospectively, in a variety of samples from patients suspected of having viral meningitis or sepsis-like syndrome. RESULTS: The assay detected 64 EV serotypes and HPeV types 1-4. Of 186 patients, 63 (33.9%) were EV positive and 18 (9.7%) HPeV positive in one or more samples. In 43 of 159 feces and 6 of 57 throat samples viral culture and PCR were positive. With real-time PCR 27 extra EV and 19 HPeV positives were found. Blood and CSF were present from 33 patients. In 19 patients blood and CSF were positive, one was only positive in CSF, two were only positive in blood, 11 were negative. From 96 patients CSF and/or blood samples were tested and compared to results in throat and/or feces samples. Forty patients were EV-PCR and 14 HPeV-PCR positive in blood and/or CSF. All of these were confirmed by a positive PCR for the respective virus in feces and/or throat. CONCLUSIONS: Simultaneous detection of EV and HPeV with this two-step real-time PCR is specific, faster and more sensitive than viral culture. All systemic infections (blood or CSF positive) were confirmed in feces. Culture is no longer necessary for clinical diagnosis and should only be performed on PCR-positive samples to obtain isolates for typing purposes. Application of this assay is an important improvement for patient management since the outcome of the analysis is available within the time frame of clinical decision-making.  相似文献   
74.
75.
76.
The value profiles of 5 intracellular enzymes, 15 metabolites (with 2 associated ratios), and 3 electrolytes were monitored over time in 9 captive-reared African black-footed penguins (Spheniscus demersus) with different avian malaria clinical status: uninfected, subclinically infected, and clinically infected with fatal outcome. Fatal infections were caused byPlasmodium relictum. Numerous schizonts were visible in the lungs, liver, spleen, and interstitial tissue of the kidneys. The feference ranges of 23 serum clinical chemistry parameters and 2 ratios were established forS. demersus. The mean values obtained for 8 of 23 parameters of the infected penguins were signficantly different from those recorded for the uninfected birds, indicating impaired renal function, hepatic dysfunction, and nonspecific tissue damage related to the infestation with exoerythrocytic schizonts. Analysis of sensitivity, specificity, and negative and positive predictive values (PPVs) showed that gamma-glutamyltranspeptidase (GGTP), alanine aminotransferase (ALT), and creatinine reached PPVs and a specificity over 57% for avian malaria infections in penguins. Creatinine, ALT, and GGTP values should be consulted in evaluation of the clinical malaria status ofS. demersus.  相似文献   
77.
Prenatal trisomy 7 is usually a cell culture artifact in amniocytes with normal diploid karyotype at birth and normal fetal outcome. In the same way, true prenatal trisomy 7 mosaicism usually results in a normal child except when trisomic cells persist after birth or when trisomy rescue leads to maternal uniparental disomy, which is responsible for 5.5-7% of patients with Silver-Russell syndrome (SRS). We report here on the unusual association of SRS and Hirschsprung's disease (HSCR) in a patient with maternal uniparental heterodisomy 7 and trisomy 7 mosaicism in intestine and skin fibroblasts. HSCR may be fortuitous given its frequency, multifactorial inheritance and genetic heterogeneity. However, the presence of the trisomy 7 mosaicism in intestine as well as in skin fibroblasts suggests that SRS and HSCR might possibly be related. Such an association might result from either an increased dosage of a nonimprinted gene due to trisomy 7 mosaicism in skin fibroblasts (leading to SRS) and in intestine (leading to HSCR), or from an overexpression, through genomic imprinting, of maternally expressed imprinted allele(s) in skin fibroblasts and intestine or from a combination of trisomy 7 mosaicism and genomic imprinting. This report suggests that the SRS phenotype observed in maternal uniparental disomy 7 (mUPD(7)) patients might also result from an undetected low level of trisomy 7 mosaicism. In order to validate this hypothesis, we propose to perform a conventional and molecular cytogenetic analysis in different tissues every time mUPD7 is displayed.  相似文献   
78.
The bone marrow karyotypes of three patients with acute myelocytic leukemia (AML) or myelodysplastic syndrome (MDS) were studied at diagnosis and revealed, multiple copies of the same chromosomal anomaly, considered as psu idic(21)(q22) associated with other rearrangement(s). The karyotype of a fourth patient with MDS in transformation showed one copy of a dicentric marker presumably derived from a similar psu idic(21) by (tandem?) interstitial amplification of part of its structure, resembling a "homogeneous staining region", and described as der(21)psu idic(21)(q22)hsr(21)(q22). This rearrangement, previously described in isolated cases only, might be considered as recurrent in AML/MDS and associated with an unfavorable prognosis. It is most probably a secondary change, because it was never observed as sole abnormality and the main association, as for trisomy 21, was with del(5q). In the four cases, the number of partial supernumerary segmental 21pter-->21q22 copies, ranged from 2 to 10. The AML1 gene did not appear to be the common target of this amplification because this locus had been lost by the psu idic(21) in one patient  相似文献   
79.
The T cell response against myelin basic protein (MBP) has been extensively studied in humans because of its putative role in the pathophysiology of multiple sclerosis (MS). Higher concordance rates in monozygous twins as well as an increased risk in relatives suggest the role of genetic factors in MS susceptibility. Very little is known about the shaping of T cell repertoire towards self antigens in humans and their contribution to disease susceptibility in autoimmune disorders. Here we report the comparative T cell epitope recognition patterns towards the MBP auto-antigen in healthy identical twins. We have established MBP-specific T cell lines from eight sets of twins and characterized their fine epitope specificity. Intra-pair comparison showed the co-existence of shared as well as distinct epitopes in six of eight pairs and a complete absence of concordant epitope recognition within two other pairs. These findings indicate that important differences in T cell repertoires against a self antigen may be observed between genetically identical healthy individuals, rendering difficult the interpretation of the differences which may be observed between identical twins discordant for an autoimmune disease.  相似文献   
80.
Summary The immunological phenotypes of the lymphoid cells in 39 cutaneous malignant melanomas have been investigated by staining cryostat sections with a panel of 20 monoclonal antibodies against lymphoid cells and their subsets. Staining was performed by the alkaline phosphatase: anti-alkaline phosphatase (APAAP) method in which the substrate label (red) is easily distinguishable from melanin. The lymphoid infiltrates had an essentially identical composition in all cases, consisting of T-lymphocytes associated with both Langerhans cells and HLA-DR-positive tissue macrophages. B-lymphocytes and natural killer cells were either absent or only present in low numbers. The ratio between T8 (suppressor/cytotoxic) and T4 (helper/inducer) lymphocytes varied and showed no correlation with melanoma subtype, level of invasion or magnitude of lymphocytic response. Examination for markers associated with T-cell activation and/or with cell proliferation revealed that all lesions contained HLA-DR-positive T-lymphocytes, whereas expression of the transferrin receptor and the interleukin-2 receptor (Tac-antigen) occurred mainly in melanomas with a significant inflammatory infiltrate. These data support the concept that malignant melanomas are capable of evoking autologous T-cell immune reactions.  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