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   1559篇
  免费   111篇
  国内免费   23篇
耳鼻咽喉   7篇
儿科学   93篇
妇产科学   39篇
基础医学   153篇
口腔科学   44篇
临床医学   135篇
内科学   274篇
皮肤病学   31篇
神经病学   56篇
特种医学   143篇
外科学   204篇
综合类   145篇
预防医学   103篇
眼科学   11篇
药学   104篇
中国医学   45篇
肿瘤学   106篇
  2023年   14篇
  2022年   25篇
  2021年   57篇
  2020年   52篇
  2019年   43篇
  2018年   47篇
  2017年   39篇
  2016年   38篇
  2015年   45篇
  2014年   68篇
  2013年   71篇
  2012年   99篇
  2011年   100篇
  2010年   100篇
  2009年   95篇
  2008年   57篇
  2007年   54篇
  2006年   59篇
  2005年   37篇
  2004年   28篇
  2003年   36篇
  2002年   20篇
  2001年   22篇
  2000年   14篇
  1999年   21篇
  1998年   49篇
  1997年   59篇
  1996年   51篇
  1995年   39篇
  1994年   32篇
  1993年   31篇
  1992年   10篇
  1991年   6篇
  1990年   10篇
  1989年   23篇
  1988年   19篇
  1987年   18篇
  1986年   16篇
  1985年   10篇
  1984年   10篇
  1982年   9篇
  1981年   9篇
  1980年   13篇
  1979年   3篇
  1978年   3篇
  1977年   7篇
  1976年   6篇
  1975年   2篇
  1958年   4篇
  1957年   2篇
排序方式: 共有1693条查询结果,搜索用时 15 毫秒
41.
Performing transcatheter tricuspid valve interventions requires a thorough knowledge of right-heart imaging. Integration of chamber views across the spectrum of imaging modalities (i.e., multislice computed tomography, fluoroscopy, and echocardiography) can facilitate transcatheter interventions on the right heart. Optimal fluoroscopic viewing angles for guiding interventional procedures can be obtained using pre-procedural multislice computed tomography scans. The present paper describes fluoroscopic viewing angles necessary to appreciate right-heart chamber anatomy and their relationship to echocardiography using multislice computed tomography.  相似文献   
42.
OBJECTIVE: To prospectively document the prevalence of otitis media with effusion (OME) in 86 African-American children between ages 2 and 5 years. STUDY DESIGN: Eighty-six children in center-based child care whose ear status had been followed from infancy continued to be observed. Middle ear status was assessed by pneumatic otoscopy and tympanometry biweekly. RESULTS: The prevalence of OME decreased as children became older. The mean proportion of examinations demonstrating bilateral OME (BOME) ranged from 12% between 24 to 30 months to 4% between 54 to 60 months of age. The mean proportion of exams revealing bilateral normal ears increased from 77% at 24 to 30 months to 88% at 54 to 60 months of age. Although 60 children had experienced BOME that lasted 4 months or longer in the 6- to 24-month age period, only 8 of these children experienced at least 4 months of continuous BOME between 24 to 60 months. CONCLUSIONS: The proportion of time with BOME decreased progressively with increasing age in this population. Only 8 of 60 children who had experienced more than 4 consecutive months of BOME before 2 years of age continued to manifest persistent effusion or experience recurrences of prolonged BOME after 2 years of age.  相似文献   
43.
Vaccine-associated paralytic poliomyelitis (VAPP) is a rare complication of oral polio vaccine. We describe a fatal case of VAPP in an 8-month-old boy with Major Histocompatibility Class II deficiency. The isolated poliovirus was a Sabin type 2-type 1 recombinant that showed 1.4% VP1 divergence from Sabin type 2.  相似文献   
44.
Parasitic helminth infection has been shown to modulate pathological inflammatory responses in allergy and autoimmune disease. The aim of this study was to examine the effects of infection with a helminth parasite, Heligmosomoides polygyrus, on type 1 diabetes (T1D) in nonobese diabetic (NOD) mice and to elucidate the mechanisms involved in this protection. H. polygyrus inoculation at 5 weeks of age protected NOD mice from T1D until 40 weeks of age and also inhibited the more aggressive cyclophosphamide-induced T1D. Moreover, H. polygyrus inoculation as late as 12 weeks of age reduced the onset of T1D in NOD mice. Following H. polygyrus inoculation of NOD mice, pancreatic insulitis was markedly inhibited. Interleukin-4 (IL-4), IL-10, and IL-13 expression and the frequency of CD4+ CD25+ FoxP3+ regulatory T cells were elevated in mesenteric and pancreatic lymph nodes. Depletion of CD4+ CD25+ T cells in vivo did not abrogate H. polygyrus-induced T1D protection, nor did anti-IL-10 receptor blocking antibody. These findings suggest that infection with H. polygyrus significantly inhibits T1D in NOD mice through CD25- and IL-10-independent mechanisms and also reduces the severity of T1D when administered late after the onset of insulitis.Helminth parasites infect about 1.5 billion people worldwide, especially in developing countries, and cause chronic infection that leads to malnutrition, anemia, impaired growth, and significant mortality. Intestinal nematode parasites can produce strong polarized Th2-type responses in mice. This immune response is characterized by eosinophilia, mucosal mast cell hyperplasia, elevated immunoglobulin E (IgE) secretion, and increased production of Th2 cytokines, such as interleukin-4 (IL-4) and IL-13. Recent studies have suggested that helminth infection can regulate infectious, allergic, or autoimmune inflammatory diseases. Helminth infection enhances susceptibility to certain infectious diseases, like tuberculosis (11, 35) and viral hepatitis (10, 17). Conversely, helminth infection is protective in murine models of asthma (19), multiple sclerosis (40), and inflammatory bowel disease (42).Type 1 diabetes (T1D) is a life-threatening disease that affects approximately 1 out of 400 children in westernized societies (18). Over the past 3 decades, the rate of T1D has increased by approximately 4% per year in both Europe and the United States (8, 12, 39). This increase in disease incidence may result in part from a dysregulated immune system due to lack of exposure to certain environmental pathogens, such as helminth parasites (5, 7, 32). Studies with nonobese diabetic (NOD) mice showed that inoculation with Trichinella spiralis, Heligmosomoides polygyrus, or Schistosoma mansoni markedly reduced the rate of T1D and suppressed lymphoid infiltration in the islets (9, 37). T1D was also prevented in NOD mice by injection of whole eggs or soluble antigens from the schistosome egg antigen or the schistosome worm antigen, but only if treatment was started at 4 weeks of age (49). Moreover, the addition of oral insulin B chain to schistosome egg antigen-treated mice augmented the induction of regulatory T cells (Tregs) that secreted IL-4, IL-10, and transforming growth factor beta (TGF-β) (27).We were interested in further examining potential mechanisms contributing to the control of T1D during infection with the intestinal nematode parasite H. polygyrus. This strictly enteric parasite triggers a potent Th2-type response without eliciting an associated Th1-type response (4). We found that H. polygyrus infection exerted significant protection against T1D in NOD mice when administered at 5 and 7 weeks of age and even when given as late as 12 weeks of age (30% protection). This was associated with reduced lymphoid infiltration in the islets and an increased frequency of CD25+ Tregs with augmented Th2-type responses, including induction of alternatively activated macrophages (AAMΦs) and IL-10 mRNA in pancreatic lymph nodes (PLN). When H. polygyrus-inoculated NOD mice were treated with cyclophosphamide (Cyp), an agent known to accelerate T1D, T1D prevention was sustained. Similarly, when H. polygyrus-inoculated NOD mice were treated with anti-CD25 monoclonal antibody (MAb) in vivo, we observed no change in insulitis between this group and those receiving a control monoclonal Ig. Furthermore, in Cyp-treated NOD mice, administration of an anti-IL-10 receptor (IL-10R) blocking MAb did not abrogate H. polygyrus-induced protection from T1D. These findings suggest that H. polygyrus inoculation suppressed T1D even after the development of insulitis and that suppression of T1D in H. polygyrus-treated NOD mice is accomplished through CD25- and IL-10-independent mechanisms.  相似文献   
45.
PurposeComparative efficacy of exenatide versus insulin glargine primarily on glucemic control, and secondarily on body mass index (BMI), lipid profile and blood pressure, in type 2 diabetes mellitus (T2DM) patients suboptimally treated with metformin monotherapy.Material/MethodsForty-seven inadequately treated T2DM patients on metformin assigned to exenatide (n=18) or insulin glargine (n=29) for 26 weeks. Glycosylated hemoglobin (HbA1c), serum lipids, BMI, systolic and diastolic blood pressure, and adverse events, including episodes of hypoglycemia and gastrointestinal symptoms, were recorded.ResultsEither treatment had a similar favorable mean reduction in HbA1c. However, more patients in exenatide group achieved HbA1c ≤ 7% at the 26th week compared with insulin glargine group (p=0.036). Insulin glargine group had significantly more episodes of hypoglycemia compared with exenatide group (p=0.039). Gastrointestinal adverse events were non-significantly higher in the exenatide group. A significantly greater BMI reduction was observed in exenatide group, whereas BMI was not altered in insulin glargine group. Total and LDL cholesterol (p=0.012), and triglycerides (p=0.016) significantly decreased, whereas HDL cholesterol increased (p=0.021) in the exenatide group, whereas only total cholesterol decreased in insulin glargine group. Changes in systolic and diastolic blood pressure were insignificant in both groups.ConclusionsExenatide provided similar reduction in HbA1c, but fewer episodes of hypoglycemia, compared with insulin glargine. Exenatide had also a favorable effect on weight loss, although more gastrointestinal adverse events. Exenatide may provide a justified alternative in second line treatment of T2DM, but more trials are required to elucidate its long-term safety and cost-effectiveness.  相似文献   
46.
Hereditary hemochromatosis (HH) is a common preventable disorder of iron overload that can result in liver cirrhosis and reduced lifespan. Most HH is due to homozygosity for the HFE p.C282Y substitution. We conducted a study of screening for p.C282Y in high schools where p.C282Y heterozygotes (CY) individuals were informed of their genotype by letter. We studied whether these individuals understood the implications of their genotype, whether this resulted in anxiety or reduced health perception and whether cascade testing was higher in families of CY than wild‐type homozygous (CC) individuals. We found 586 of 5757 (1 in 10) screened individuals were CY. One month after receiving their result, 83% correctly answered that they have one copy of p.C282Y. There was no adverse change in anxiety or health perception from prior to screening to 1 month after receiving results. Significantly more family members of CY individuals than CC individuals were informed about HH and had testing for HH. In conclusion, we found that informing CY individuals of their genotype does not increase anxiety and the implications are generally well understood. This leads to cascade testing in a minority of families. CY individuals should be informed of their genetic status when identified by population screening.  相似文献   
47.
48.
Factors involved in the stability of trinucleotide repeats during transmission were studied in 139 families in which a full mutation, premutation or intermediate allele at either FRAXA or FRAXE was segregating. The transmission of alleles at FRAXA, FRAXE and four microsatellite loci were recorded for all individuals. Instability within the minimal and common ranges (0-40 repeats for FRAXA, 0-30 repeats for FRAXE) was extremely rare; only one example was observed, an increased in size at FRAXA from 29 to 39 repeats. Four FRAXA and three FRAXE alleles in the intermediate range (41-60) repeats for FRAXA, 31-60 for FRAXE) were unstably transmitted. Instability was more frequent for FRAXA intermediate alleles that had a tract of pure CGG greater than 37 although instability only occurred in two of 13 such transmissions: the changes observed were limited to only one or two repeats. Premutation FRAXA alleles over 100 repeats expanded to a full mutation during female transmission in 100% of cases, in agreement with other published series. There was no clear correlation between haplotype and probability of expansion of FRAXA premutations. Instability at FRAXA or FRAXE was more often observed in conjunction with a second instability at an independent locus suggesting genomic instability as a possible mechanism by which at least some FRAXA and FRAXE mutations arise.   相似文献   
49.
50.
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