全文获取类型
收费全文 | 4173篇 |
免费 | 388篇 |
国内免费 | 260篇 |
专业分类
4821篇 |
出版年
2024年 | 6篇 |
2023年 | 48篇 |
2022年 | 128篇 |
2021年 | 210篇 |
2020年 | 123篇 |
2019年 | 162篇 |
2018年 | 178篇 |
2017年 | 131篇 |
2016年 | 173篇 |
2015年 | 289篇 |
2014年 | 288篇 |
2013年 | 343篇 |
2012年 | 359篇 |
2011年 | 348篇 |
2010年 | 208篇 |
2009年 | 178篇 |
2008年 | 237篇 |
2007年 | 195篇 |
2006年 | 153篇 |
2005年 | 162篇 |
2004年 | 115篇 |
2003年 | 120篇 |
2002年 | 95篇 |
2001年 | 84篇 |
2000年 | 71篇 |
1999年 | 76篇 |
1998年 | 45篇 |
1997年 | 42篇 |
1996年 | 38篇 |
1995年 | 40篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 18篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有4821条查询结果,搜索用时 0 毫秒
121.
Objective
To develop person-centered episodes of care (PCE) for community-dwelling individuals in the top fifth percentile of Ontario health care expenditures in order to: (1) describe the main clinical groupings for spending; and (2) identify patterns of spending by health sector (e.g. acute care, home care, physician billings) within and across PCE.Data sources
Data were drawn from population-based administrative databases for all publicly funded health care in Ontario, Canada in 2010/11.Study design
This study is a retrospective cohort study.Data collection/extraction methods
A total of 587,982 community-dwelling individuals were identified among those accounting for the top 5% of provincial health care expenditures between April 1, 2010 and March 31, 2011. PCE were defined as starting with an acute care admission and persisting through subsequent care settings and providers until individuals were without health system contact for 30 days. PCE were classified according to the clinical grouping for the initial admission. PCE and non-PCE costs were calculated and compared to provide a comprehensive measurement of total health system costs for the year.Principal findings
Among this community cohort, 697,059 PCE accounted for nearly 70% ($11,815.3 million (CAD)) of total annual publicly-funded expenditures on high-cost community-dwelling individuals. The most common clinical groupings to start a PCE were Acute Planned Surgical (35.2%), Acute Unplanned Medical (21.0%) and Post-Admission Events (10.8%). Median PCE costs ranged from $3,865 (IQR = $1,712-$10,919) for Acute Planned Surgical to $20,687 ($12,207-$39,579) for Post-Admission Events. Inpatient acute ($8,194.5 million) and inpatient rehabilitation ($434.6 million) health sectors accounted for the largest proportions of allocated PCE spending over the year.Conclusions
Our study provides a novel methodological approach to categorize high-cost health system users into meaningful person-centered episodes. This approach helps to explain how costs are attributable within individuals across sectors and has applications in episode-based payment formulas and quality monitoring. 相似文献122.
锦橙汁囊的超微结构 总被引:1,自引:0,他引:1
用常规电镜方法观察了锦橙[Citrussinensis (L.) Osb.]汁囊从原始细胞到发育为一个具柄的成熟汁囊的过程中,汁囊构成细胞超微结构的变化。锦橙汁囊原始细胞及发育为球状体时的构成细胞以及柱状结构顶端的细胞都是一种典型的分生组织细胞。在细胞质中有包括线粒体、质体、内质网、核糖体等丰富的细胞器,但没有观察到高尔基体。这些分生细胞分裂一段时期后就停止活动,逐渐分化为适应贮藏功能的液泡化薄壁细胞。分生细胞开始分化时,在细胞中出现许多小液泡和高尔基体。这些小液泡逐渐地融合,同时细胞质变少,最后形成一个有中央大液泡的薄壁细胞,在紧贴细胞膜的薄薄的一层细胞质中有线粒体、质体、高尔基体以及含有许多脂滴的杂色体。但成熟果实中汁囊的薄壁细胞中几乎没有任何细胞器。 相似文献
123.
Nonparametric and parametric approaches have been proposed to estimate false discovery rate under the independent hypothesis testing assumption. The parametric approach has been shown to have better performance than the nonparametric approaches. In this article, we study the nonparametric approaches and quantify the underlying relations between parametric and nonparametric approaches. Our study reveals the conservative nature of the nonparametric approaches, and establishes the connections between the empirical Bayes method and p-value-based nonparametric methods. Based on our results, we advocate using the parametric approach, or directly modeling the test statistics using the empirical Bayes method. 相似文献
124.
Sun M Ren Q Liu Z Guan G Gou H Ma M Li Y Liu A Yang J Yin H Luo J 《Experimental parasitology》2011,(3):192-195
Owing to the need to combat the spread of chemical acaricide resistance in ticks, we evaluated the efficacy of a mixture of the entomopathogenic fungus Beauveria bassiana AT17 and acaricides for the control of Hyalomma anatolicum anatolicum in China. A mixture of B. bassiana AT17 at the concentration of 108 conidia/mL and the synthetic pyrethroid deltamethrin at concentrations of 2500, 250, 25, 5, 2.5, 0.5 and 0.25 ppm was tested in vitro. The germination capability, vegetative growth, conidia production, and viability of B. bassiana AT17 were assessed and the efficacy of the mixture in killing engorged H. anatolicum anatolicum females was measured. High mortality rates were achieved when the entomopathogen was combined with different concentrations of deltamethrin. Neither B. bassiana AT17 nor deltamethrin alone at the same concentrations could cause the higher mortality rates seen with the combination. In addition the combination killed the ticks more rapidly than did either agent alone (3–5 days more rapidly). Our results indicate that the mixture of B. bassiana AT17 and deltamethrin has potential as a new type of reagent for integrated control of H. anatolicum anatolicum. 相似文献
125.
Jasmonates are a new class of plant hormones that play important roles in plant development and plant defense. TheCOI1 gene was previously shown to be required for jasmonate-regulated plant fertility and defense. We demonstrated for the first
time that COI1 interacts with theArabidopsis SKP1-LIKE1 (ASK1) to form a complex that is required for jasmonate action inplanta. Functional analysis by antisense strategy showed thatASK1 is involved in male fertility. 相似文献
126.
127.
皂苷类药物普遍分子量比较大,水溶性好,但不易透过细胞膜难以被人体吸收,因此口服制剂体内生物利用度较低.近年来对单体皂苷及总皂苷类药物制剂方面的研究越来越多,随着新型的给药系统和新辅料的出现,皂苷类药物在体内的生物利用度大大提高.本文主要介绍以单体皂苷或总皂苷活性部位为主药的制剂研究进展,以期为该类成分的进一步研究提供思路. 相似文献
128.
目的为了为揭示肌萎缩脊髓侧索硬化症(amyotrophic lateral sclerosis,ALS)认知功能障碍的机制提供依据,观察不同年龄ALS转基因小鼠海马中突触囊泡蛋白(synaptophysin,Syp)的表达情况。方法取95d、108d和122dALS转基因鼠海马,应用免疫荧光、Westernblot、RT-PCR技术检测Syp在海马中的表达变化。结果与同窝野生型鼠比较,Syp蛋白和mRNA表达水平在95d龄ALS转基因鼠海马中无明显变化,在108d与122d龄ALS转基因鼠海马中明显降低。结论Syp在ALS转基因鼠海马中表达减少表明,突触可塑性降低是ALS学习记忆能力下降的重要病理学基础。 相似文献
129.
Xiaofei Ji Xinfeng Bai Zhe Li Sen Wang Zhiwei Guan Xuemei Lu 《Applied microbiology and biotechnology》2013,97(16):7317-7324
Cytophaga hutchinsonii is an aerobic cellulolytic gliding bacterium. The mechanism of its cell motility over surfaces without flagella and type IV pili is not known. In this study, mariner-based transposon mutagenesis was used to identify a new locus CHU_1797 essential for colony spreading on both hard and soft agar surfaces through gliding. CHU_1797 encodes a putative outer membrane protein of 348 amino acids with unknown function, and proteins which have high sequence similarity to CHU_1797 were widespread in the members of the phylum Bacteroidetes. The disruption of CHU_1797 suppressed spreading toward glucose on an agar surface, but had no significant effect on cellulose degradation for cells already in contact with cellulose. SEM observation showed that the mutant cells also regularly arranged on the surface of cellulose fiber similar with that of the wild type strain. These results indicated that the colony spreading ability on agar surfaces was not required for cellulose degradation by C. hutchinsonii. This was the first study focused on the relationship between cell motility and cellulose degradation of C. hutchinsonii. 相似文献
130.