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   1424篇
  免费   57篇
  国内免费   4篇
耳鼻咽喉   20篇
儿科学   23篇
妇产科学   20篇
基础医学   149篇
口腔科学   29篇
临床医学   75篇
内科学   483篇
皮肤病学   78篇
神经病学   142篇
特种医学   18篇
外科学   178篇
综合类   8篇
一般理论   1篇
预防医学   85篇
眼科学   13篇
药学   76篇
肿瘤学   87篇
  2024年   1篇
  2023年   13篇
  2022年   4篇
  2021年   30篇
  2020年   12篇
  2019年   43篇
  2018年   49篇
  2017年   22篇
  2016年   23篇
  2015年   34篇
  2014年   35篇
  2013年   59篇
  2012年   137篇
  2011年   119篇
  2010年   77篇
  2009年   48篇
  2008年   108篇
  2007年   100篇
  2006年   98篇
  2005年   101篇
  2004年   94篇
  2003年   86篇
  2002年   78篇
  2001年   30篇
  2000年   20篇
  1999年   16篇
  1998年   6篇
  1997年   3篇
  1996年   3篇
  1995年   2篇
  1994年   2篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1990年   4篇
  1989年   6篇
  1988年   4篇
  1987年   3篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1983年   2篇
  1971年   1篇
  1969年   1篇
排序方式: 共有1485条查询结果,搜索用时 31 毫秒
91.
Background. Aberrations of the p53 gene and overexpression of its protein are widely recognized markers of malignancy including oral squamous cell carcinomas. This study was performed to evaluate the relationship of immunoexpression of p53 protein in series of 91 squamous cell carcinomas of the oral cavity with clinicopathologic parameters and to investigate whether p53 immunoexpression might influence the clinical outcome of the disease. Methods. From a group of 287 consecutive patients, 91 surgically treated ones were randomly selected. P53 protein expression was investigated by means of immunohistochemistry. Clinical and histopathologic data were gathered, and the patient survival was analyzed. Results. Of the oral carcinomas, 52.7% (n = 48) overexpressed p53, using a threshold of 10% stained cell nuclei. There was a negative correlation of p53 immunoexpression with a histologic grade of differentiation (r = ?0.236, p = .06) but not with clinical variables. Overall survival rate was 59% at 5 years. In univariate analysis, tumor size, node status, and advanced clinical stage were significantly associated with shortened overall survival. In patients without neck node metastases, p53 showed a strong correlation with survival (p = .01). In multivariate analysis performed only on N0 patients, tumor extension and p53 immunoexpression were found to be the only independent prognostic parameters with relative risks of 1.9 and 4.3, respectively. Conclusions. A strong relationship was observed between p53 immunoexpression and poor prognosis in patients with oral squamous cell carcinomas without neck node metastases. © 2004 Wiley Periodicals, Inc. Head Neck 26: 22–30, 2004  相似文献   
92.
93.
94.
95.
OBJECTIVES: Calorie restriction has been associated with anorexia in growing individuals, but the mechanisms involved are not known. Also, the effects of carbohydrates and lipid restriction in growing individuals were not studied. The aim of this study was to determine whether 66% calorie restriction (lipids and carbohydrates) differentially affects growing rats of the Wistar or Lewis strains. METHODS: Growing male Wistar and Lewis rats were subjected to 66% calorie restriction for 4 weeks. Plasma prolactin, growth hormone (GH), and adrenocorticotropic hormone (ACTH) levels were measured by specific radioimmunoassays. Likewise, lymphocytes from submaxillary lymph nodes were aseptically obtained to study absolute number of lymphocytes, cell surface markers (CD4+, CD8+, CD4+CD8+, B, and T cells), and proliferation. RESULTS: The body weight gain was lower in Lewis than in Wistar rats and was blunted in both strains by calorie restriction. Wistar and Lewis rats exhibited differential patterns of plasma prolactin, ACTH, and GH levels as well as proliferative capacities of T and B cells and their distribution in the submaxillary lymph nodes. Calorie restriction increased plasma prolactin and ACTH levels in Lewis as compared with Wistar rats. However, the plasma GH levels were diminished in both strains of rats by calorie restriction. All changes in plasma prolactin ACTH and GH levels seemed to correlate with the modifications observed in the distributions of T and B subsets in the submaxillary lymph nodes as well as in their proliferative capacity. CONCLUSIONS: Calorie restriction differentially modifies the secretory patterns of prolactin, GH, and ACTH in Lewis and in Wistar rats. These changes may explain, at least in part, the associated modifications in the proliferative capacity of submaxillary lymph node lymphocytes and in their distribution.  相似文献   
96.
97.
Lip cancer is the most frequent malignant neoplasm of the oral cavity; however, there is no information available on the incidence of this type of cancer in Mexico. This study provides information about the clinico-pathological features of lip cancer patients admitted at a cancer hospital in Mexico City during an 11-year period and describes the treatment modalities performed and their results. A total of 113 patients were studied. There were 74 men (65.5%) and 39 women (34.5%), ranging in age from 14 to 106 years (mean 70 years). In 53 cases (46.9%) an association was found between the disease and chronic sun exposure. Additionally, positive smoking antecedents were recorded in 58 cases (51.3%). As 15 patients were followed for less than 1 month, they were excluded for further analysis. There were 82 cases (83.7%) of squamous cell carcinoma, 10 (10.2%) basal cell carcinomas, and one case (1%) each of adenocarcinoma NOS, melanoma, adenoid cystic carcinoma, Merkel cell carcinoma, lymphoepithelioma and angiosarcoma. We observed an incidence of malignant neoplasms in the upper lip of 33.7%, which is higher than most of the published series and may be due to the fact that in this series we included all histological types of lip cancers. Fifty percent of the cases were found in stages III and IV. Cervical lymph node metastases were found in 21% of patients with no previous treatment, and they developed in 5.3% after treatment. Our data suggest that tumoral size is directly related to the possibility of developing node metastases, as none of them occurred in patients T1, whereas 10 (62.5%) of the patients in T4 presented them. Seven deaths were documented (7.1%), five of which corresponded to squamous cell carcinoma, one to Merkel cell carcinoma, and one to adenocarcinoma. Deaths were directly related to the disease in six cases, and one patient died due to surgical complications. Distant metastases were found in only two patients, one of which coursed with an adenocarcinoma and the other with a Merkel cell carcinoma. Based on the present results, we suggest that the differences encountered with respect to other series, particularly the higher incidence found in women, the frequent presentation of this type of neoplasms in the upper lip, the wide variety of histopathological diagnoses and the high frequency of cases with cervical lymph node affection, should lead us to search for multi-modal treatment alternatives in this population.  相似文献   
98.
OBJECTIVE: To assess the potential value of ductus venosus Doppler studies in the detection of fetal aneuploidy on measurement of nuchal translucency. METHODS: The pulsatility index for veins (PIV) and the lowest velocity during atrial contraction (A-wave) were determined in the fetal ductus venosus in 3382 consecutive pregnancies at 10 to 14 weeks and studied from December 1996 to December 2001. Nuchal translucency was also measured. The population studied included 1664 pregnancies at high risk and 1718 at low risk for fetal aneuploidy. RESULTS: In relation to the prenatal detection of trisomy 21, the ductus venosus PIV was increased in 75% (36/48), the A-wave was decreased in 58% (28/48), and nuchal translucency was enlarged in 81% (39/48) of the trisomy 21 fetuses [71% (22/31) when nuchal translucency referrals were excluded]. The corresponding figures for trisomies 18 and 13 were 71, 58 and 83%, respectively, being 33, 33 and 33% for other unbalanced anomalies. CONCLUSION: There is a high proportion of fetuses with trisomies 21, 18 and 13 (around 75%) in which the ductus venosus PIV is increased (above the 95th percentile) at 10 to 14 weeks, this proportion being similar to that observed for increased nuchal translucency measurement.  相似文献   
99.
OBJECTIVE: To evaluate the association between FSH efficacy and FSHR alleles. DESIGN: Retrospective study. SETTING: University-based fertility unit and a private center for biomedical research. PATIENT(S): One hundred two women with ovarian function who were undergoing controlled ovarian stimulation (COS). Women were categorized as poor responders (< or =3 ovarian follicles at the end of the cycle) or normal responders (>3 follicles). INTERVENTION(S): Daily administration of exogenous FSH. MAIN OUTCOME MEASURE(S): Number of good or poor responders. RESULT(S): The allele frequency and genotype distribution of the Ser680Asn marker differed significantly between groups. Cycle cancellations were increased (21%) among women who were homozygous for Ser680 compared with Ser/Asn and Asn/Asn patients, and 36% of poor-responders were homozygous for Ser680. CONCLUSION(S): The results support a role for FSHR gene in COS outcome. However, the weight of this factor is probably low. The Ser680 allele may act in concert with other environmental and genetic factors that contribute to FSH efficacy.  相似文献   
100.
OBJECTIVE: To compare the utilization of total hip replacement (THR) between Hispanic persons and non-Hispanic persons in a sample with health insurance. RESEARCH DESIGN: Case-control study using Medicare claims data. PATIENTS: The cases were Medicare beneficiaries from Arizona, Illinois, New Mexico, or Texas who underwent a primary THR. The controls were Medicare beneficiaries who did not receive a THR, matched by age, sex, and county of residence. MEASURES: Beneficiary surnames and the race indicator in Medicare records were used to classify beneficiaries' probability of being Hispanic. Conditional logistic regression was used to estimate the odds of receiving of THR, adjusting for Medicaid eligibility. RESULTS: Six thousand four hundred thirty-seven recipients of a primary THR were matched to 12,874 controls. According to the Medicare race indicator, 1% of recipients of THR and 3.3% of controls were Hispanic (P < or =0.001). The odds of THR decreased as the probability of Hispanic ethnicity increased, from an odds ratio (OR) of 1.00 among beneficiaries with non-Hispanic surnames, to an OR of 0.36 among those with heavily Hispanic surnames (95% CI, 0.31, 0.43). Poverty, as reflected by eligibility for Medicaid, did not modify the low odds of THR among Hispanic persons (OR, 0.25 among Medicaid-eligible Hispanic persons; 95% CI, 0.19, 0.33; and OR, 0.30 among Hispanic persons not Medicaid eligible; 95% CI, 0.24, 0.38). CONCLUSION: Hispanic persons with Medicare receive THR at lower rates than do non-Hispanic persons. Because Medicare covers THR, our findings suggest that under utilization of THR by Hispanic persons cannot be attributed to lack of health insurance alone.  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