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   8107篇
  免费   457篇
  国内免费   22篇
耳鼻咽喉   112篇
儿科学   471篇
妇产科学   140篇
基础医学   902篇
口腔科学   208篇
临床医学   567篇
内科学   1820篇
皮肤病学   159篇
神经病学   475篇
特种医学   342篇
外国民族医学   1篇
外科学   1225篇
综合类   262篇
一般理论   7篇
预防医学   465篇
眼科学   191篇
药学   706篇
中国医学   36篇
肿瘤学   497篇
  2023年   65篇
  2022年   120篇
  2021年   250篇
  2020年   147篇
  2019年   168篇
  2018年   224篇
  2017年   173篇
  2016年   197篇
  2015年   211篇
  2014年   290篇
  2013年   394篇
  2012年   525篇
  2011年   570篇
  2010年   362篇
  2009年   276篇
  2008年   432篇
  2007年   446篇
  2006年   380篇
  2005年   354篇
  2004年   315篇
  2003年   260篇
  2002年   244篇
  2001年   190篇
  2000年   205篇
  1999年   176篇
  1998年   82篇
  1997年   50篇
  1996年   47篇
  1995年   48篇
  1994年   45篇
  1992年   90篇
  1991年   87篇
  1990年   81篇
  1989年   97篇
  1988年   79篇
  1987年   67篇
  1986年   59篇
  1985年   68篇
  1984年   63篇
  1983年   59篇
  1982年   35篇
  1979年   47篇
  1978年   30篇
  1977年   28篇
  1976年   31篇
  1974年   38篇
  1973年   38篇
  1972年   29篇
  1971年   28篇
  1969年   35篇
排序方式: 共有8586条查询结果,搜索用时 0 毫秒
41.
Adrenoleukodystrophy (ALD) is an X-linked disorder caused by a defect in the metabolism of long chain fatty acids leading to demyelination, neurodegeneration, and death. The disease typically presents in young boys and adolescent boys. Allogeneic bone marrow transplantation has been used to halt progression of the disease. However, many patients lack suitable HLA- matched related donors and must rely on unmatched donors for a source of stem cells. The purpose of this study was to evaluate outcomes of unrelated donor umbilical cord blood transplantation after chemotherapy-based myeloablative conditioning and retrospectively determine if baseline studies correlate and help predict outcome. Between November 22, 1996, and November 3, 2005, 12 boys with X-linked ALD who lacked HL- matched related donors were referred to Duke University Medical Center for transplantation. These children were conditioned with myeloablative therapy including busulfan, cyclophosphamide, and antithymocyte globulin before receiving umbilical cord-blood transplants from unrelated donors. Baseline studies of neurophysiologic, neuroimaging, and neurodevelopmental status were performed and patients were subsequently evaluated for survival, engraftment, graft-versus-host disease, and neurodevelopmental outcomes. A substudy evaluated whether baseline neuroimaging and neurophysiologic studies correlated with cognitive and motor function and if these studies were predictive of posttransplantation outcomes. The umbilical cord blood grafts had normal levels of very long chain fatty acids. They delivered a median of 6.98 x 10(7) nucleated cells per kilogram of recipient body weight and were discordant for up to 4 of 6 HLA markers. Neutrophil engraftment occurred at a median of 22.9 days after transplantation. Three patients had grade II-IV acute graft-versus-host disease; 2 had extensive chronic graft-versus-host disease. Cumulative incidence of overall survival of the group at 6 months is 66.7% (95% confidence interval 39.9-93.3%). Median follow-up was 3.3 years (range 12 days to 6.3 years). As previously reported with bone marrow transplantation, symptomatic patients faired poorly with lower survival and rapid deterioration of neurologic function. This study included 3 patients transplanted at a very young age (2.6-3.5 years) before the onset of clinical symptoms who continue to develop at a normal rate for 3-5 years posttransplant. Although baseline Loes scores correlated with cognitive and motor outcome, neurophysiologic studies failed to show statistically significant differences. Transplantation of boys with X-linked ALD using partial HLA-matched umbilical cord blood yields similar results to those previously reported after bone marrow transplantation. Superior outcomes were seen in neurologically asymptomatic boys less than 3.5 years of age at the time of transplantation. Baseline Loes scores were a strong predictor of cognitive and motor outcome.  相似文献   
42.
Gastrointestinal vascular anomalies are extremely uncommon. We describe a patient with Down syndrome who presented with acute abdominal pain due to a mixed capillary and venous vascular malformation involving the proximal jejunum.  相似文献   
43.
44.
By functional complementation of a PDR5 null mutant of Saccharomyces cervisiae, we have cloned and sequenced the multidrug-resistance gene CDR1 of Candida albicans. Transformation by CDR1 of a PDR5-disrupted host hypersensitive to cycloheximide and chloramphenicol resulted in resistance to cycloheximide, chloramphenicol and other drugs, such as the antifungal miconazole, with collateral hypersensitivity to oligomycin, nystatin and 2,4 dinitrophenol. Our results also demonstrate the presence of several PDR5 complementing genes in C. albicans, displaying multidrug-resistance patterns different from PDR5 and CDR1. The nucleotide sequence of CDR1 revealed that, like PDR5, it encodes a putative membrane pump belonging to the ABC (ATP-binding cassette) superfamily. CDR1 encodes a 1501-residue protein of 169.9 kDa whose predicted structural organization is characterized by two homologous halves, each comprising a hydrophobic region with a set of six transmembrane stretches, preceded by a hydrophilic nucleotide binding fold.  相似文献   
45.
To understand the mechanism(s) of appetite modulation by DHEA, we have undertaken a series of studies to examine the effects of DHEA on neurotransmitters and neuropeptides known to affect appetitive behavior. Here, we report the effect of DHEA on serum enterostatin-VPDPR or E, a pentapeptide known to cause selective diminution in fat intake. Four-week-old lean (fa/+) and obese (fa/fa) Zucker rats were divided into control and treatment groups. DHEA-treated groups received powdered chow containing 0.6% DHEA ad lib for 16 weeks. Another group of obese rats was pair fed to match the intake of the obese DHEA-treated rats. At the end of this period, trunk blood was collected from fasted rats for assay of E-like immunoreactivity (E-LI) by ELISA. DHEA treatment caused a significant diminution in circulating E-LI in both lean (control: 2030 +/- 226; treated: 752 +/- 145 ng/mL; n = 10, p < 0.0001) and obese (control: 2489 +/- 391, n = 6; treated: 1123 +/- 185 ng/mL, n = 7; p = 0.0003) rats. Because DHEA treatment decreases caloric intake and body weight, we examined the effect of caloric intake and body weight on E-LI levels. Serum ELI levels were lower in the obese DHEA-treated group compared to that of obese pair fed (pair fed: 1589 +/- 313, n = 6; DHEA: 1123 +/- 185 ng/mL, n = 7), but the differences were statistically insignificant (p = 0.185). Also, both weight-matched lean and obese control rats had significantly (p < 0.008) higher E-LI than their DHEA-treated counterparts. To examine whether the decrease in serum E-LI following DHEA treatment could be due to increased peptide metabolism, the rate of disappearance of endogenous E-LI from serum (obese control and DHEA-treated) at 37 degrees C was evaluated. The results show an attenuation of peptide metabolism in serum from DHEA-treated rats, a finding contrary to our expectations. In summary, DHEA treatment lowers serum E-LI levels both in lean and obese Zucker rats. This decrement in peptide level is not secondary to changes in body weight or caloric intake due to DHEA, or due to altered serum peptide metabolism. Although DHEA appears to be a potent modulator of E-LI levels, the relationship between DHEA and E-LI in relation to appetitive behavior remains to be clarified.  相似文献   
46.
47.
48.
49.
Immune regulation by novel costimulatory molecules   总被引:10,自引:0,他引:10  
CD4 helper T (Th)-cells and the cytokines that they produce play essential regulatory roles in immune and autoimmune responses. Th activation and differentiation is regulated by costimulatory receptors. CD28 and CTLA-4 are important in maintaining the threshold of T-cell activation. ICOS and PD-1 are novel costimulatory receptors expressed on activated T-cells. B7-H3 recognizes a putative costimulatory receptor on activated T-cells. Here we summarize the latest developments in the novel costimulatory molecules and their roles in regulating Th activation, differentiation, and function.  相似文献   
50.
The recent implication of Helicobacter pylori in the pathogenesis of gastritis-peptic ulcer syndrome and its relevance for the development of upper gastrointestinal malignancy warrant efficient methods for the detection and demonstration of the organism in biopsy specimens. We have compared 5 staining methods, namely, haematoxylin and eosin (H & E), immunohistochemistry (IHC), the silver staining HpSS, the alcian yellow-toluidine blue (Leung) method (A-Y) and Genta staining, for the demonstration of the organism in gastric biopsies taken from antrum, body and fundus of 118 patients who presented to our hospital with upper gastrointestinal symptoms. We found no significant differences in the efficacy of H & E, IHC, HpSS and A-Y in the demonstration of H. pylori in all 3 gastric sites. The least reproducible stain in our hands was the Genta stain. We conclude that H & E is adequate for the initial assessment of gastric biopsies in symptomatic upper gastrointestinal patients. This is because it is a well-tested, cheap and easy staining method, requiring a relatively short period of time to perform, with highly reproducible results. It has an added advantage of enabling simultaneous assessment of morphological changes accompanying H. pylori infection. When the density of the organism is expected to be low, we recommend addition of HpSS staining because of its high sensitivity and low cost. The disadvantages of the other staining methods (IHC, A-Y and Genta) are discussed.  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