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   817篇
  免费   56篇
  国内免费   17篇
耳鼻咽喉   6篇
儿科学   69篇
妇产科学   20篇
基础医学   130篇
口腔科学   58篇
临床医学   79篇
内科学   143篇
皮肤病学   30篇
神经病学   40篇
特种医学   53篇
外科学   87篇
综合类   9篇
预防医学   33篇
眼科学   7篇
药学   63篇
中国医学   1篇
肿瘤学   62篇
  2022年   5篇
  2021年   14篇
  2020年   16篇
  2019年   17篇
  2018年   15篇
  2017年   7篇
  2016年   10篇
  2015年   25篇
  2014年   26篇
  2013年   27篇
  2012年   26篇
  2011年   22篇
  2010年   29篇
  2009年   40篇
  2008年   25篇
  2007年   39篇
  2006年   31篇
  2005年   20篇
  2004年   23篇
  2003年   16篇
  2002年   24篇
  2001年   22篇
  2000年   33篇
  1999年   29篇
  1998年   31篇
  1997年   29篇
  1996年   22篇
  1995年   20篇
  1994年   23篇
  1993年   10篇
  1992年   8篇
  1991年   12篇
  1990年   13篇
  1989年   15篇
  1988年   19篇
  1987年   10篇
  1986年   14篇
  1985年   11篇
  1984年   13篇
  1983年   6篇
  1982年   11篇
  1981年   8篇
  1979年   8篇
  1977年   5篇
  1975年   9篇
  1974年   7篇
  1973年   4篇
  1972年   7篇
  1971年   5篇
  1968年   4篇
排序方式: 共有890条查询结果,搜索用时 31 毫秒
1.
BACKGROUND: On December 26, 2004, the biggest earthquake for 40 years, measuring 9.0 on the Richter scale, triggered a tsunami that pounded the coastal areas of South Asia and East Africa. The effects of the tsunami on skin conditions have not been evaluated. OBJECTIVE: To determine the influence of the tsunami on skin conditions by evaluating the skin problems of patients presenting at hospitals after the tsunami. METHODS: Between 5 and 25 January 2005, two dermatologists evaluated patients who complained of skin problems at an outpatient clinic and emergency room of a general hospital in Banda Aceh, Aceh Province, Indonesia. RESULTS: The total number of patients that presented during the study period was 235 (131 males and 104 females), and they had a total of 265 skin problems. In terms of age distribution, most subjects were in their fourth decade (23.0%), followed by the third (22.6%) and fifth decade (16.6%). The most prevalent skin problems were infections-infestations (32.5%), followed by eczemas (29.8%) and traumatic skin disorders (29.4%). In males, traumatic skin disorders were most common. The great majority of infection-infestation cases involved superficial fungal infections. Contact dermatitis accounted for three-quarters of eczema cases, and mainly involved the arms (40.0%) and legs (27.1%). The majority of traumatic skin disorders were lacerations, punctures and penetrations, and the feet (44.7%) and hands (18.8%) were most frequently affected. CONCLUSIONS: Unhygienic conditions, exposure to a hazardous environment and contact with various objects during and after the tsunami probably increased the prevalence of infections-infestations, traumatic skin disorders and contact dermatitis. To prevent these problems and associated secondary bacterial infections, health-related education and early medical management are required.  相似文献   
2.
3.
4.
The effect of the cellular immune response by total body irradiation was investigated. The transplant survival (skin grafts) was determined as immune parameter. Donors were colony-bred Wistar rats and recipients were colony-bred Sprague-Dawley rats. The investigations were carried out with irradiated rats and with rats irradiated after thymectomy and/or adrenalectomy as well as with animals without irradiation. A single total-body irradiation (1 and 2 Gy) was administered. The skin graft survival in irradiated rats was significant shorter (radiogenic immunostimulation) than in unirradiated rats; there were no significant differences between the operated (thymectomy and/or adrenalectomy) and not operated animals. Including precedent examinations this radiogenic immunostimulation is caused by a relatively selective inactivation of T-suppressor cells.  相似文献   
5.
Effects of paracetamol have been studied in a hydroxyurea (HU)-resistant mouse mammary tumour cell line TA3H2, shown to overproduce the small subunit of ribonucleotide reductase. These TA3H2 cells were much more resistant than the TA3H (wild-type) cells towards the inhibitory effect of paracetamol on cell growth, IC50 0.55 mM paracetamol for the wild-type compared to 2.7 mM for the HU-resistant cells. The reduced cell growth was due to an inhibition of replicative DNA synthesis, judged from an increased percentage of cells in S-phase measured by flow cytometry. Furthermore, in the wild-type cells, the increase in the number of cells in S phase was already observed at 0.1 mM while in the HU-resistant cell line this effect was first seen at 3.0 mM paracetamol. HU inhibits ribonucleotide reductase by destroying a tyrosyl free radical located on the small subunit of the enzyme. By electron paramagnetic resonance we demonstrate that paracetamol added to crude cell extracts of HU-resistant cells also immediately destroys this radical. These results show that paracetamol reduces DNA synthesis by a specific inhibition of ribonucleotide reductase. A concentration-dependent induction of sister chromatid exchanges was found both with paracetamol (1.0-10 mM) and HU (0.3-3 mM) in wild-type cells whereas no such increase was observed in HU-resistant cells. Paracetamol (1 mM for 2 h) also increased the number of chromosomal aberrations CAs in wild-type cells (i.e. chromatid breaks and chromatid exchanges). The frequency of CAs was not increased in HU-resistant cells at paracetamol concentrations up to 10 mM.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
6.
Antineutrophil cytoplasmic antibodies (ANCA) of IgG class have been described at high prevalence in autoimmune hepatitis (AIH) and primary sclerosing cholangitis (PSC). Data on IgA class ANCA in these diseases are limited. The aim of this study was to determine the prevalence and fluorescence patterns of IgA class ANCA in AIH and PSC and to examine a relationship between the presence of IgA ANCA and clinical characteristics in these patients. Sera from 35 patients with PSC (21 with concomitant inflammatory bowel disease), 40 patients with AIH and 10 healthy controls were studied. ANCA were detected on ethanol-fixed neutrophils using an indirect immunofluorescence technique. ANCA of the IgA class were found in 20% of sera from patients with PSC and in 50% of AIH sera. The majority of AIH patients with IgA class ANCA showed a 'classical' perinuclear staining pattern, whereas the 'classical' and 'atypical' perinuclear fluorescence patterns were distributed equally in PSC. In sera containing IgG and IgA class ANCA simultaneously, IgG class ANCA showed an 'atypical' pANCA fluorescence pattern whereas IgA class ANCA produced a 'classical' perinuclear staining. The presence of IgA class ANCA was not associated with disease-specific clinical characteristics. IgA class ANCA are more frequently detected in sera of patients with AIH than PSC. The diversity of fluorescence patterns points to different target antigens of IgA class ANCA with distinct subcellular localizations.  相似文献   
7.
Human chromosome 11p15.5 and distal mouse chromosome 7 include a megabase-scale chromosomal domain with multiple genes subject to parental imprinting. Here we describe mouse and human versions of a novel imprinted gene, IMPT1 , which lies between IPL and p57 KIP2 and which encodes a predicted multi-membrane-spanning protein similar to bacterial and eukaryotic polyspecific metabolite transporter and multi- drug resistance pumps. Mouse Impt1 and human IMPT1 mRNAs are highly expressed in tissues with metabolite transport functions, including liver, kidney, intestine, extra-embryonic membranes and placenta, and there is strongly preferential expression of the maternal allele in various mouse tissues at fetal stages. In post-natal tissues there is persistent expression, but the allelic bias attenuates. An allelic expression bias is also observed in human fetal and post-natal tissues, but there is significant interindividual variation and rare somatic allele switching. The fact that Impt1 is relatively repressed on the paternal allele, together with data from other imprinted genes, allows a statistical conclusion that the primary effect of human chromosome 11p15.5/mouse distal chromosome 7 imprinting is domain-wide relative repression of genes on the paternal homolog. Dosage regulation of the metabolite transporter gene(s) by imprinting might regulate placental and fetal growth.   相似文献   
8.
Recently, in-vitro maturation (IVM) of immature human oocytes recovered from non-stimulated follicles has been applied in the treatment of infertility. However, in previous reports, very few embryos cultured in conventional medium have reached the expanded blastocyst stage following in-vitro maturation and fertilization (IVM/IVF). The objective of this study was to investigate whether the developmental competence of human embryos following IVM/IVF could be enhanced by the use of a human ampullary cell co-culture system. Immature human oocytes were aspirated from small follicles at Caesarean section and then cultured in medium containing human menopausal gonadotrophin for 36 to 48 h, followed by insemination. Zygotes were randomly cultured either in conventional culture medium alone or in the co-culture system. Of 48 embryos cultured in conventional medium alone, all arrested at the 2-16- cell stage on day 3 after insemination. Of 46 embryos cultured in the co-culture system, 26 embryos (56.5%) arrested at the 2-16-cell stage. Six embryos (13%) developed to the morula stage. Fourteen embryos (30.4%) developed to expanded blastocysts and two blastocysts were hatching on day 7 after insemination. We conclude that co-culture significantly enhances the development of blastocysts in embryos resulting from IVM/IVF.   相似文献   
9.
Mutations in the gene encoding the Survival Motor Neuron (SMN) protein are responsible for autosomal recessive proximal spinal muscular atrophy (SMA). SMN orthologues have been identified in the nematode worm Caenorhabditis elegans and the yeast Schizosaccharomyces pombe but, to date, no human paralogues have been described. Here we describe identification and characterization of an SMN-related protein (SMNrp) gene that encodes a novel protein of 239 amino acids, which has recently been identified as a constituent of the spliceosome complex and designated SPF30. Significant similarity to the SMN protein is apparent only within a central region of SMNrp that represents a tudor domain. The SMNrp/SPF30 gene has been mapped to chromosome 10q23. It is differentially expressed, with abundant levels in skeletal muscle. An exclusively nuclear localization for SMNrp in cultured cells and muscle sections was revealed using GFP fusion constructs and thereafter confirmed with a polyclonal antibody raised against SMNrp. Overexpression of SMNrp as a fusion protein in HeLa cells in culture induced dose-dependent apoptosis with positive TUNEL staining. In addition to a possible role for this protein as a pro-apoptotic factor, SMN and its related protein share significant similarities in sequence and cellular function.   相似文献   
10.
Background:  Control of mRNA stability is an essential regulatory process in eukaryotic gene expression. HuR, a 3'UTR mRNA binding protein, can protect AU-rich mRNA from degradation in response to stresses. PlGF, an angiogenic growth factor, contains two consensus AU-rich sites suggesting that under normal conditions HuR may protect PlGF mRNA from degradation. Trophoblast expression of PlGF is significantly decreased in preeclampsia and by hypoxia in vitro . We hypothesize that decreased levels of cytoplasmic HuR may contribute to decreased PlGF expression in hypoxic and preeclamptic trophoblast.
Methods:  Western blots were used to determine relative effects of in vitro hypoxia on HuR protein expression and subcellular localization in trophoblast. Immunohistochemistry was used to compare HuR expression patterns in trophoblast of preeclamptic and normal placentae.
Results:  Cytoplasmic expression of HuR was decreased 1.4 fold in the cytoplasm and 1.2 fold in the nucleus of JEG3 cells. A shift in HuR was more apparent in primary trophoblast with a greater than 2-fold decrease in the cytoplasm and a 1.4 fold decrease in the nucleus following 24 hr of hypoxia. Immunohistochemical analyses detected HuR expression in near term trophoblast in situ . However, this technical approach did not detect a significant change in HuR expression between normal and preeclamptic trophoblast.
Conclusions:  HuR expression is decreased in hypoxic trophoblast, at least in vitro , which may provide a causal link to decreased PlGF mRNA expression. Down regulation of trophoblast PlGF expression is thought to contribute to the pathophysiology associated with preeclampsia including the relative lack of perfusion of the placenta and systemic renal effects.  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