全文获取类型
收费全文 | 75359篇 |
免费 | 5183篇 |
国内免费 | 156篇 |
专业分类
耳鼻咽喉 | 527篇 |
儿科学 | 2875篇 |
妇产科学 | 2601篇 |
基础医学 | 8879篇 |
口腔科学 | 926篇 |
临床医学 | 12789篇 |
内科学 | 13830篇 |
皮肤病学 | 1195篇 |
神经病学 | 6981篇 |
特种医学 | 1264篇 |
外国民族医学 | 33篇 |
外科学 | 6510篇 |
综合类 | 943篇 |
一般理论 | 106篇 |
预防医学 | 10633篇 |
眼科学 | 910篇 |
药学 | 4400篇 |
1篇 | |
中国医学 | 154篇 |
肿瘤学 | 5141篇 |
出版年
2023年 | 476篇 |
2022年 | 670篇 |
2021年 | 1402篇 |
2020年 | 1003篇 |
2019年 | 1627篇 |
2018年 | 1853篇 |
2017年 | 1350篇 |
2016年 | 1502篇 |
2015年 | 1646篇 |
2014年 | 2271篇 |
2013年 | 3728篇 |
2012年 | 5345篇 |
2011年 | 5544篇 |
2010年 | 3006篇 |
2009年 | 2839篇 |
2008年 | 4855篇 |
2007年 | 5428篇 |
2006年 | 5187篇 |
2005年 | 5142篇 |
2004年 | 4925篇 |
2003年 | 4611篇 |
2002年 | 4396篇 |
2001年 | 639篇 |
2000年 | 477篇 |
1999年 | 606篇 |
1998年 | 936篇 |
1997年 | 731篇 |
1996年 | 641篇 |
1995年 | 571篇 |
1994年 | 548篇 |
1993年 | 519篇 |
1992年 | 391篇 |
1991年 | 353篇 |
1990年 | 358篇 |
1989年 | 292篇 |
1988年 | 269篇 |
1987年 | 269篇 |
1986年 | 247篇 |
1985年 | 287篇 |
1984年 | 313篇 |
1983年 | 289篇 |
1982年 | 357篇 |
1981年 | 324篇 |
1980年 | 264篇 |
1979年 | 187篇 |
1978年 | 166篇 |
1977年 | 175篇 |
1976年 | 134篇 |
1975年 | 135篇 |
1973年 | 116篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Immunization with amyloid-β (Aβ) peptide reduces amyloid load in animal studies and in humans; however clinical trials resulted in the development of a pro-inflammatory cellular response to Aβ. Apoptosis has been employed to stimulate humoral and Th2-biased cellular immune responses. Thus, we sought to investigate whether immunization using a DNA vaccine encoding Aβ in conjunction with an attenuated caspase generates therapeutically effective antibodies. Plasmids encoding Aβ and an attenuated caspase were less effective in reducing amyloid pathology than those encoding Aβ alone. Moreover, use of Aβ with an Arctic mutation (E22G) as an immunogen was less effective than wild-type Aβ in terms of improvements in pathology. Low levels of IgG and IgM were generated in response to immunization with a plasmid encoding wild-type Aβ. These antibodies decreased plaque load by as much as 36 ± 8% and insoluble Aβ42 levels by 56 ± 3%. Clearance of Aβ was most effective when antibodies were directed against N-terminal epitopes of Aβ. Moreover, immunization reduced CAA by as much as 69 ± 12% in TgCRND8 mice. Finally, high-molecular-weight oligomers and Aβ trimers were significantly reduced with immunization. Thus, immunization with a plasmid encoding Aβ alone drives an attenuated immune response that is sufficient to clear amyloid pathology in a mouse model of Alzheimer's disease. 相似文献
72.
Paula Vanessa Pedron Oltramari Ricardo de Lima Navarro José Fernando Castanha Henriques Rumio Taga Tania Mary Cestari Guilherme Janson José Mauro Granjeiro 《Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics》2007,104(5):e9-16
OBJECTIVE: The objective of this study was to radiographically quantify bone density and bone height preservation in tooth extraction alveolus filled with xenograft. STUDY DESIGN: The maxillary and mandibular fourth deciduous molars and fourth premolars of 6 minipigs were removed. Randomly, in 3 animals the right side was used as the test side and in the other 3 animals the left side was the test side. Intraoral radiographs were performed to compare the condition at the initial time and 3 months later. Measurements of bone height and bone density were performed using KS300 (Zeiss) software. RESULTS: After 3 months, there was a statistically significant smaller bone height loss for the test group. The test group presented a statistically greater bone density immediately after tooth extraction. However, after 3 months there was no statistically significant difference between the groups. CONCLUSIONS: The results suggest that treatment of postextraction alveolus with xenograft can preserve bone height initially but differences in bone density compared to when no xenograft is used are not sustained. 相似文献
73.
PROBLEM: Recent developments in providing care to children with emotional and behavioral disorders, especially those with serious emotional disturbance, have included the establishment of systems of care. Guided by a set of principles and values, these systems of care have organized and delivered services to children and families with complex needs. To date, nurses have not had a salient role in systems of care. RESULTS: It is estimated that 20% of American children and adolescents have an emotional or mental disorder. As many as two thirds of these children are not receiving services. Systems of care have been funded to provide services for these children, particularly for the most severely affected. To date, nursing has not had a prominent role in these systems of care. CONCLUSIONS: Based on their knowledge, skills, and holistic approach to care, nurses could better integrate nursing care into systems of care. Possible roles as case managers, primary therapists, in-home interventionists, and in educational programs are suggested. 相似文献
74.
Sandra Urdaneta Hartmann Brian Wigdahl Elizabeth B Neely Cheston M Berlin Cara-Lynne Schengrund Hung-Mo Lin Mary K Howett 《Journal of human lactation》2006,22(1):61-74
Reduction of transmission of human immunodeficiency virus type 1 (HIV-1) through human milk is needed. Alkyl sulfates such as sodium dodecyl sulfate (SDS) are microbicidal against HIV-1 at low concentrations, have little to no toxicity, and are inexpensive. The authors have reported that treatment of HIV-1-infected human milk with < or = 1% (10 mg/mL) SDS for 10 minutes inactivates cell-free and cell-associated virus. The SDS can be removed with a commercially available resin after treatment without recovery of viral infectivity. In this article, the authors report results of selective biochemical analyses (ie, protein, immunoglobulins, lipids, cells, and electrolytes) of human milk subjected to SDS treatment and removal. The SDS treatment or removal had no significant effects on the milk components studied. Therefore, the use of alkyl sulfate microbicides to treat milk from HIV-1-positive women may be a simple, practical, and nutritionally sound way to prevent or reduce transmission of HIV-1 while still feeding with mother's own milk. 相似文献
75.
BackgroundStatistical analysis of a data set with missing data is a frequent problem to deal with in epidemiology. Methods are available to manage incomplete observations, avoiding biased estimates and improving their precision, compared to more traditional methods, such as the analysis of the sub-sample of complete observations.MethodsOne of these approaches is multiple imputation, which consists in imputing successively several values for each missing data item. Several completed data sets having the same distribution characteristics as the observed data (variability and correlations) are thus generated. Standard analyses are done separately on each completed dataset then combined to obtain a global result. In this paper, we discuss the various assumptions made on the origin of missing data (at random or not), and we present in a pragmatic way the process of multiple imputation. A recent method, Multiple Imputation by Chained Equations (MICE), based on a Monte-Carlo Markov Chain algorithm under missing at random data (MAR) hypothesis, is described. An illustrative example of the MICE method is detailed for the analysis of the relation between a dichotomous variable and two covariates presenting MAR data with no particular structure, through multivariate logistic regression.ResultsCompared with the original dataset without missing data, the results show a substantial improvement of the regression coefficient estimates with the MICE method, relatively to those obtained on the dataset with complete observations.ConclusionThis method does not require any direct assumption on joint distribution of the variables and it is presently implemented in standard statistical software (Splus, Stata). It can be used for multiple imputation of missing data of several variables with no particular structure. 相似文献
76.
77.
78.
79.
80.
David G Hicks Brian J Yoder Sarah Short Shannon Tarr Nichole Prescott Joseph P Crowe Andrea E Dawson G Thomas Budd Steven Sizemore Muzaffer Cicek Toni K Choueiri Raymond R Tubbs Daniel Gaile Norma Nowak Mary Ann Accavitti-Loper Andra R Frost Danny R Welch Graham Casey 《Clinical cancer research》2006,12(22):6702-6708
PURPOSE: This study aims to determine the effect of loss of breast cancer metastasis suppressor 1 (BRMS1) protein expression on disease-free survival in breast cancer patients stratified by estrogen receptor (ER), progesterone receptor (PR), or HER2 status, and to determine whether loss of BRMS1 protein expression correlated with genomic copy number changes. EXPERIMENTAL DESIGN: A tissue microarray immunohistochemical analysis was done on tumors of 238 newly diagnosed breast cancer patients who underwent surgery at the Cleveland Clinic between January 1, 1995 and December 31, 1996, and a comparison was made with 5-year clinical follow-up data. Genomic copy number changes were determined by array-based comparative genomic hybridization in 47 breast cancer cases from this population and compared with BRMS1 staining. RESULTS: BRMS1 protein expression was lost in nearly 25% of cases. Patients with tumors that were PR negative (P=0.006) or HER2 positive (P=0.039) and <50 years old at diagnosis (P=0.02) were more likely to be BRMS1 negative. No overall correlation between BRMS1 staining and disease-free survival was observed. A significant correlation, however, was seen between loss of BRMS1 protein expression and reduced disease-free survival when stratified by either loss of ER (P=0.008) or PR (P=0.029) or HER2 overexpression (P=0.026). Overall, there was poor correlation between BRMS1 protein staining and copy number status. CONCLUSIONS: These data suggest a mechanistic relationship between BRMS1 expression, hormone receptor status, and HER2 growth factor. BRMS1 staining could potentially be used in patient stratification in conjunction with other prognostic markers. Further, mechanisms other than genomic deletion account for loss of BRMS1 gene expression in breast tumors. 相似文献