全文获取类型
收费全文 | 13198篇 |
免费 | 1688篇 |
国内免费 | 295篇 |
专业分类
耳鼻咽喉 | 53篇 |
儿科学 | 145篇 |
妇产科学 | 159篇 |
基础医学 | 1109篇 |
口腔科学 | 199篇 |
临床医学 | 1154篇 |
内科学 | 1191篇 |
皮肤病学 | 86篇 |
神经病学 | 699篇 |
特种医学 | 468篇 |
外科学 | 971篇 |
综合类 | 2213篇 |
现状与发展 | 1篇 |
一般理论 | 8篇 |
预防医学 | 3820篇 |
眼科学 | 112篇 |
药学 | 1520篇 |
10篇 | |
中国医学 | 766篇 |
肿瘤学 | 497篇 |
出版年
2024年 | 100篇 |
2023年 | 423篇 |
2022年 | 725篇 |
2021年 | 1004篇 |
2020年 | 880篇 |
2019年 | 727篇 |
2018年 | 621篇 |
2017年 | 675篇 |
2016年 | 622篇 |
2015年 | 567篇 |
2014年 | 942篇 |
2013年 | 1058篇 |
2012年 | 627篇 |
2011年 | 731篇 |
2010年 | 542篇 |
2009年 | 520篇 |
2008年 | 547篇 |
2007年 | 540篇 |
2006年 | 512篇 |
2005年 | 431篇 |
2004年 | 386篇 |
2003年 | 318篇 |
2002年 | 267篇 |
2001年 | 178篇 |
2000年 | 133篇 |
1999年 | 102篇 |
1998年 | 109篇 |
1997年 | 103篇 |
1996年 | 79篇 |
1995年 | 57篇 |
1994年 | 73篇 |
1993年 | 61篇 |
1992年 | 51篇 |
1991年 | 51篇 |
1990年 | 46篇 |
1989年 | 52篇 |
1988年 | 36篇 |
1987年 | 47篇 |
1986年 | 35篇 |
1985年 | 30篇 |
1984年 | 30篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 12篇 |
1980年 | 25篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 12篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Hospital discharge data from New Jersey were used to identify cases of asbestosis for the 8 years 1979-1986. Multiple admissions were deleted so that each individual was counted once at the time of his/her first hospitalization with an asbestosis diagnosis. White males had the highest age-adjusted average annual discharge rate of 19.3 cases/100,000 population, followed by black males (12.3 cases/100,000) and white females (1.2 cases/100,000). The discharge rate was positively associated with age in each race/sex category. The relationship between rates for black males and white males depended on age: under 65 years, the rates were almost equal, and at 65 years and older, the white rates were nearly twice the black rates. There were two areas of the state where the rates were highest: the north-central and southwest regions. These two areas represent manufacturing and shipbuilding applications of asbestos, respectively. During the years 1979-1986, the annual percentage increase in asbestosis rates was 20% for white males, 17% for black males, and 8% for white females. Continued surveillance will reveal when the rates for asbestosis stop increasing. 相似文献
12.
Analysis of count data from clinical trials using mixed effect analysis has recently become widely used. However, algorithms
available for the parameter estimation, including LAPLACE and Gaussian quadrature (GQ), are associated with certain limitations,
including bias in parameter estimates and the long analysis runtime. The stochastic approximation expectation maximization
(SAEM) algorithm has proven to be a very efficient and powerful tool in the analysis of continuous data. The aim of this study
was to implement and investigate the performance of a new SAEM algorithm for application to count data. A new SAEM algorithm
was implemented in MATLAB for estimation of both, parameters and the Fisher information matrix. Stochastic Monte Carlo simulations
followed by re-estimation were performed according to scenarios used in previous studies (part I) to investigate properties
of alternative algorithms (Plan et al., 2008, Abstr 1372 []). A single scenario was used to explore six probability distribution models. For parameter estimation, the relative bias
was less than 0.92% and 4.13% for fixed and random effects, for all models studied including ones accounting for over- or
under-dispersion. Empirical and estimated relative standard errors were similar, with distance between them being <1.7% for
all explored scenarios. The longest CPU time was 95 s for parameter estimation and 56 s for SE estimation. The SAEM algorithm
was extended for analysis of count data. It provides accurate estimates of both, parameters and standard errors. The estimation
is significantly faster compared to LAPLACE and GQ. The algorithm is implemented in Monolix 3.1, (beta-version available in
July 2009). 相似文献
13.
14.
Richard A. Sternbach Artstotle A. Alexander David G. Rice Norman S. Greenfield 《Psychophysiology》1969,6(1):1-5
The treatment of artifactual responses in psychophysiology is rarely discussed or made explicit in research reports. The rationales and procedures of five approaches are presented: excluding the data; averaging other epochs; subjective estimation; straight-line connecting; and following the pen. Each approach is based on a somewhat different theoretical orientation, and the choice of each will depend on the researcher's theoretical preference and also the relative “costs” of losing data vs programming special instructions. Other considerations such as objectivity, consistency, and replicability are discussed. 相似文献
15.
A brief introduction to the Danish Cytogenetic Central Register (DCCR) is given, and possibilities, principles and problems concerning the establishment and maintenance of a national cytogenetic register are presented.
Various data carrier media for registers in general are discussed, of which the magnetic disc is considered most appropriate. General principles for programs capable of performing insertions, deletions and other modifications in the data base are outlined as well as the principles for the programs in the DCCR.
The individual records should preferably be identified by aid of a central person registration number (CPR) rather than by name. The data should be stored and sorted by this identification in order to facilitate retrieval of a desired record. The structure of the records is discussed with regard to prevention of the occurrence of certain errors as well as the optimization of processing.
Flexibility and economy of space are achieved by using programs able to handle records of unequal length, and problems occurring in connection with this are discussed. The question of how to protect sensitive data is dealt with, and two different methods used in the DCCR are outlined. Programs capable of analyzing karyotypes with the purpose of recognizing various cytogenetic syndromes have been developed for use in the DCCR. Various examples of computing times of typical program runs are presented. 相似文献
Various data carrier media for registers in general are discussed, of which the magnetic disc is considered most appropriate. General principles for programs capable of performing insertions, deletions and other modifications in the data base are outlined as well as the principles for the programs in the DCCR.
The individual records should preferably be identified by aid of a central person registration number (CPR) rather than by name. The data should be stored and sorted by this identification in order to facilitate retrieval of a desired record. The structure of the records is discussed with regard to prevention of the occurrence of certain errors as well as the optimization of processing.
Flexibility and economy of space are achieved by using programs able to handle records of unequal length, and problems occurring in connection with this are discussed. The question of how to protect sensitive data is dealt with, and two different methods used in the DCCR are outlined. Programs capable of analyzing karyotypes with the purpose of recognizing various cytogenetic syndromes have been developed for use in the DCCR. Various examples of computing times of typical program runs are presented. 相似文献
16.
苯丙胺类兴奋剂(ATS)娱乐性使用情况及其人群特征 总被引:7,自引:0,他引:7
目的 :了解娱乐性ATS使用者的人口学特征 ,使用方式及其他有关问题。方法 :采用病例发现法和易接近对象晤谈法 ,并结合滚雪球的方法 ,以问卷方式收集娱乐性ATS使用者的有关资料。结果 :娱乐性ATS使用者平均年龄 2 3 97± 4 95岁。未婚占 6 4 4 % ,同居占 1 5 3% ,离婚占 8 5%。高中及以上文化者占 84 7%。职业以服务员、个体商人和性工作者居多。摇头丸是最主要的滥用药物。约 90 %的人使用次数少于 50次。口服是最主要的服用途径。平均每次服用剂量约为 2 50mg ,多在周末服用 ( 72 9% )。获得ATS的主要来源是从朋友和熟人处购买 ( 72 9% )。使用ATS的主要目的包括 :提高情绪使自己快乐 ,使自己压抑时感到舒服些 ,帮助放松 ,帮助解除抑制 (情绪、行为、思维 )等。娱乐性ATS使用者合并使用酒精 ,海洛因 ,苯二氮 艹卓 类 ,大麻 ,致幻剂的比例分别为 81 3% ,2 2 0 % ,1 1 9% ,1 0 2 % ,1 7%。 96 %的ATS使用者的主要社交人群中有人使用ATS。 4 5 8%和 33 8%的使用者有临时性伴侣和性交易史。结论 :娱乐性ATS使用者为一特殊人群 ,应针对其特殊性制定相应的干预措施。 相似文献
17.
M B Holmberg 《Acta psychiatrica Scandinavica》1985,71(3):207-210
In an attempt to identify prognostic factors, non-drug users and abusers in the Gothenburg year cohort of 1953 were compared with reference to background data. Individuals with chronic abuse differed most from the "normal" group. Prognostic factors for drug abuse were: member of a multiproblem family, child psychiatric care, contact with the Social Welfare Administration at an early age, truancy, placement in special class, premature drop-out from school, admitted high-frequency drug use in a school questionnaire, for boys early registration for crimes and for girls nervous complaints. The results indicate the necessity of earlier and more effective prevention. 相似文献
18.
Kirstin Vach Ali Al-Ahmad Annette Anderson Johan Peter Woelber Lamprini Karygianni Annette Wittmer Elmar Hellwig 《Nutrients》2021,13(3)
Background: Investigating the influence of nutrition on oral health has a long scientific history. Due to recent technical advances like sequencing techniques for the oral microbiota, this topic has gained scientific interest again. A basic challenge is to understand the influence of nutrition on the oral microbiota and on the interaction between the oral bacteria, which is also statistically challenging. Methods: Log-transformed ratios of two bacteria concentrations are introduced as the basic analytic tool. The framework is illustrated by application in an experimental study exposing eleven participants to different nutrition schemes in five consecutive phases. Results: The method could be sufficiently used to analyse the interrelation between the bacteria and to identify some bacterial groups with the same as well as different reactions to additional dietary components. It was found that the strongest changes in bacterial concentrations were achieved by the additional consumption of dairy products. Conclusion: A log ratio-based analysis offers insights into the relation of different bacteria while taking specific features of compositional data into account. The presented methods allow becoming independent of the behaviour of other bacteria, which is a disadvantage of common analysis methods of compositions. The results indicate that modulations of the oral biofilm microbiota due to nutrition change can be attained. 相似文献
19.
20.
粗糙集在构建骨肿瘤辅助诊断知识库的应用研究 总被引:4,自引:0,他引:4
在骨肿瘤辅助诊断专家系统研究中,知识库的建立是一直困扰系统建立的瓶颈问题,知识库的好坏不仅影响到后续推理过程,而且还对诊断的精度有着很大的影响。本文使用基于粗糙集理论的数据挖掘技术,对已确诊病例资料数据库进行数据分析,建立骨肿瘤与患者临床表现之间的推理关系,并结合医生的临床实践,最终形成一个比较完备的辅助诊断知识数据库,为后续的推理、解释程序打下良好的基础。 相似文献