全文获取类型
收费全文 | 105917篇 |
免费 | 10360篇 |
国内免费 | 3430篇 |
专业分类
耳鼻咽喉 | 845篇 |
儿科学 | 1195篇 |
妇产科学 | 989篇 |
基础医学 | 12106篇 |
口腔科学 | 3707篇 |
临床医学 | 11338篇 |
内科学 | 10925篇 |
皮肤病学 | 1311篇 |
神经病学 | 6675篇 |
特种医学 | 3222篇 |
外国民族医学 | 11篇 |
外科学 | 7531篇 |
综合类 | 15793篇 |
现状与发展 | 8篇 |
一般理论 | 4篇 |
预防医学 | 17350篇 |
眼科学 | 1237篇 |
药学 | 13999篇 |
129篇 | |
中国医学 | 6283篇 |
肿瘤学 | 5049篇 |
出版年
2024年 | 478篇 |
2023年 | 2041篇 |
2022年 | 4151篇 |
2021年 | 5191篇 |
2020年 | 4989篇 |
2019年 | 4342篇 |
2018年 | 3946篇 |
2017年 | 4224篇 |
2016年 | 4272篇 |
2015年 | 4178篇 |
2014年 | 7292篇 |
2013年 | 7843篇 |
2012年 | 7039篇 |
2011年 | 7384篇 |
2010年 | 5524篇 |
2009年 | 5106篇 |
2008年 | 4914篇 |
2007年 | 4911篇 |
2006年 | 4174篇 |
2005年 | 3688篇 |
2004年 | 3029篇 |
2003年 | 2819篇 |
2002年 | 2143篇 |
2001年 | 2036篇 |
2000年 | 1582篇 |
1999年 | 1368篇 |
1998年 | 1306篇 |
1997年 | 1187篇 |
1996年 | 1024篇 |
1995年 | 929篇 |
1994年 | 893篇 |
1993年 | 684篇 |
1992年 | 645篇 |
1991年 | 548篇 |
1990年 | 473篇 |
1989年 | 484篇 |
1988年 | 419篇 |
1987年 | 365篇 |
1986年 | 286篇 |
1985年 | 378篇 |
1984年 | 289篇 |
1983年 | 178篇 |
1982年 | 200篇 |
1981年 | 156篇 |
1980年 | 154篇 |
1979年 | 115篇 |
1978年 | 78篇 |
1977年 | 52篇 |
1976年 | 72篇 |
1974年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
In clinical diagnosis, a patient's symptoms are observed and the probabilities of various diseases are assessed. A widely used method of formalizing this approach is independent Bayes in which symptoms are assumed to be independent conditional on the disease category. Correspondence analysis provides a method for examining the dependence between symptoms and assists in the selection of a reduced set of symptoms for the application of the independent Bayes method. This approach is illustrated on two data sets concerned with patients attending Accident and Emergency departments with chest pain and acute abdominal pain, respectively. 相似文献
22.
S. Vemuri 《Chemical biology & drug design》2005,65(4):433-439
Abstract: Precise determination of the peptide content in drug substance samples depends highly upon the particular peptide compound and methodology used. Four independent methods were evaluated and compared to determine which would produce the best experimental precision for analysis of thymalfasin (thymosin α‐1). Four different methods were evaluated including elemental analysis (CHN), quantitative amino acid analysis (AAA), high‐performance liquid chromatography (HPLC), and Kjeldahl. This study demonstrates that the AAA method is highly variable in one laboratory while quite precise in another laboratory. Similarly, HPLC results depended on the laboratory conducting the study with more precise values obtained under cGMP. On the contrary, the CHN method yielded highly precise [i.e. <2% coefficient of variation (CV)] values. As precise knowledge of protein content is fundamental for the compounding of final pharmaceutical product of a specific potency, the CHN analysis is recommended for peptide content determination of the drug substance thymalfasin. 相似文献
23.
W. Ziegler D. von Cramon 《European archives of psychiatry and clinical neuroscience》1986,236(1):44-49
Summary This paper deals with a particular aspect of speech motor control in patients suffering from apraxia of speech. Three experiments are reported concerning the phase relations between individual speech gestures. These include the timing of laryngeal, velar and labial movements relative to lingual gestures.A total of 8 patients and 12 normal controls were examined using speech material which was designed according to appropriate phonetic paradigms. Evaluation was performed on the basis of speech signal parameters referring to the kinematics of inter-articulatory phasing. Deviations of the patient group were found in all three experiments. This suggests that disturbed phase relations of individual speech movements are a general feature of apraxic speech. It is further hypothesized that the described motor symptoms are the origin of a variety of phonemic errors. Support for this view is provided by appropriate examples which refer to the examined paradigms. By this argument, much of the disturbed phonemic structure of apraxic speech may be accounted for by timing deficits. 相似文献
24.
急诊抗菌药物的使用调查与分析 总被引:1,自引:0,他引:1
目的考察了解急诊抗菌药物的使用情况。方法随机抽取2008年7—12月的急诊处方2700张,对其中抗菌药物的应用情况进行统计分析。结果急诊抗菌药物使用率49.1%,药物应用形式以单用为主(占66.3%);给药途径以口服和静脉注射为主。不合理用药处方占抗菌药物处方的10.8%,分别在选药方案、给药方案、溶媒使用、联合应用等方面存在问题。结论我院急诊抗菌药物的应用基本合理,但仍存在一定问题,需进一步加强管理。 相似文献
25.
Questionnaire data may contain missing values because certain questions do not apply to all respondents. For instance, questions addressing particular attributes of a symptom, such as frequency, triggers or seasonality, are only applicable to those who have experienced the symptom, while for those who have not, responses to these items will be missing. This missing information does not fall into the category ‘missing by design’, rather the features of interest do not exist and cannot be measured regardless of survey design. Analysis of responses to such conditional items is therefore typically restricted to the subpopulation in which they apply. This article is concerned with joint multivariate modelling of responses to both unconditional and conditional items without restricting the analysis to this subpopulation. Such an approach is of interest when the distributions of both types of responses are thought to be determined by common parameters affecting the whole population. By integrating the conditional item structure into the model, inference can be based both on unconditional data from the entire population and on conditional data from subjects for whom they exist. This approach opens new possibilities for multivariate analysis of such data. We apply this approach to latent class modelling and provide an example using data on respiratory symptoms (wheeze and cough) in children. Conditional data structures such as that considered here are common in medical research settings and, although our focus is on latent class models, the approach can be applied to other multivariate models. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
26.
Phase II clinical trials are performed to investigate whether a novel treatment shows sufficient promise of efficacy to justify its evaluation in a subsequent definitive phase III trial, and they are often also used to select the dose to take forward. In this paper we discuss different design proposals for a phase II trial in which three active treatment doses and a placebo control are to be compared in terms of a single‐ordered categorical endpoint. The sample size requirements for one‐stage and two‐stage designs are derived, based on an approach similar to that of Dunnett. Detailed computations are prepared for an illustrative example concerning a study in stroke. Allowance for early stopping for futility is made. Simulations are used to verify that the specified type I error and power requirements are valid, despite certain approximations used in the derivation of sample size. The advantages and disadvantages of the different designs are discussed, and the scope for extending the approach to different forms of endpoint is considered. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
27.
Biostatisticians have frequently uncritically accepted the measurements provided by their medical colleagues engaged in clinical research. Such measures often involve considerable loss of information. Particularly, unfortunate is the widespread use of the so‐called ‘responder analysis’, which may involve not only a loss of information through dichotomization, but also extravagant and unjustified causal inference regarding individual treatment effects at the patient level, and, increasingly, the use of the so‐called number needed to treat scale of measurement. Other problems involve inefficient use of baseline measurements, the use of covariates measured after the start of treatment, the interpretation of titrations and composite response measures. Many of these bad practices are becoming enshrined in the regulatory guidance to the pharmaceutical industry. We consider the losses involved in inappropriate measures and suggest that statisticians should pay more attention to this aspect of their work. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
28.
We analyze whether the political system and its stability are related to cross-country differences in health. We apply factor analysis on various national health indicators for a large sample of countries over the period 2000–2005 and use the outcomes of the factor analysis to construct two new health measures, i.e., the health of individuals and the quality of the health care sector. Using a cross-country structural equation model with various economic and demographic control variables, we examine the relationship between the type of regime and political stability on the one hand and health on the other. The political variables and the control variables are measured as averages over the period 1980–1999. Our results suggest that democracy has a positive relationship with the health of individuals, while regime instability has a negative relationship with the health of individuals. Government instability is negatively related to individual health via its link with the quality of the health care sector, while democracy is positively related with individual health through its link with income. Our main findings are confirmed by the results of a panel model and various sensitivity tests. 相似文献
29.
30.
Kun Hwang MD PhD Ei Tae Kim MD Se Il Lee MD DMSc 《The Journal of foot and ankle surgery》2005,44(6):473-477
The purpose of this study was to determine the genetic characteristics of foot polydactyly and identify its inheritance pattern by analyzing familial pedigree. Five cases from 2 Korean families were studied: 1 is a family whose members have been affected for 4 generations and the other for 2 generations. Using peripheral blood samples, we performed chromosomal analysis using the banding technique with Giemsa stain and karyotyping. We investigated the shape and structure of 46 chromosomes, looking for translation, deletion, inversion, ring chromosome, and isochromosome abnormalities. All peripheral blood samples demonstrated no chromosomal abnormalities, though the genetic nature of foot polydactyly and a new genetic locus was identified recently by other studies. Familial pedigree analysis suggested that polydactyly was inherited as an autosomal dominant trait in the first family. The mode of inheritance for the second family could not be determined due to an insufficient number of family members. The result of this study brought us to the conclusion that, while genetic factors play a major role in polydactyly, other factors may contribute to its occurrence. 相似文献