全文获取类型
收费全文 | 977篇 |
免费 | 85篇 |
国内免费 | 73篇 |
出版年
2024年 | 6篇 |
2023年 | 35篇 |
2022年 | 25篇 |
2021年 | 40篇 |
2020年 | 40篇 |
2019年 | 70篇 |
2018年 | 40篇 |
2017年 | 47篇 |
2016年 | 34篇 |
2015年 | 41篇 |
2014年 | 45篇 |
2013年 | 88篇 |
2012年 | 55篇 |
2011年 | 39篇 |
2010年 | 25篇 |
2009年 | 35篇 |
2008年 | 37篇 |
2007年 | 42篇 |
2006年 | 34篇 |
2005年 | 30篇 |
2004年 | 33篇 |
2003年 | 34篇 |
2002年 | 33篇 |
2001年 | 26篇 |
2000年 | 26篇 |
1999年 | 14篇 |
1998年 | 16篇 |
1997年 | 23篇 |
1996年 | 11篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 2篇 |
排序方式: 共有1135条查询结果,搜索用时 31 毫秒
41.
新型猪瘟疫苗研究进展 总被引:5,自引:0,他引:5
猪瘟是由猪瘟病毒引起猪的一种急性、热性和高度接触性传染病.该病呈世界性分布,给世界养猪业造成了巨大的经济损失.目前,疫苗接种仍然是防控猪瘟的主要手段.虽然传统的猪瘟弱毒疫苗(如C株)安全有效,但猪瘟的临床表现发生了很大变化,呈现典型猪瘟和非典型猪瘟共存、隐性感染和持续感染并现,免疫失败的现象时有报道,且不能区分野毒感染和免疫接种.因此,研制安全、高效、能区分野毒感染和疫苗免疫动物(DIVA)的新型猪瘟疫苗极为必要.文中就近年来开发的核酸疫苗、病毒活载体疫苗、基于蛋白/肽的疫苗、基因缺失疫苗、嵌合瘟病毒疫苗等新型DIVA猪瘟疫苗作一综述. 相似文献
42.
An audit of the screening history of all new cervical cancer cases has been a requirement since April 2007. While NHS cervical screening programmes (NHSCSP) guidance requires that women diagnosed with cervical cancer are offered the findings of the audit, as yet there has been no research to investigate the psychological impact that meeting to discuss the findings might have on patients. This is in spite of the fact that cytological under‐call may play a role in as many as 20% of cervical cancer cases. This review draws on the literature concerning breaking bad news, discussing cancer and disclosing medical errors, in order to gain insight into both the negative and positive consequences that may accompany a cervical screening review meeting. We conclude that while patients are likely to experience some distress at disclosure, there are also likely to be positive aspects, such as greater trust and improved perception of care. 相似文献
43.
Mitchell E. Nuhn Manfred Binder Andy F.S. Taylor Roy E. Halling David S. Hibbett 《Fungal biology》2013,117(7-8):479-511
The generic and sub-generic relationships in the Boletineae (Boletales) were studied using nuclear large subunit (nuc-lsu), translation elongation factor 1-alpha (tef1), and DNA directed RNA polymerase largest subunit (RPB1). The Boletineae, with the exclusion of Hydnomerulius pinastri, was strongly supported and the status of the families Boletaceae and Paxillaceae is discussed. Members of the genus Boletus are found throughout the phylogeny, with the majority not closely related to the type species, Boletus edulis. Many of the traditional, morphologically defined genera are not supported as monophyletic and additional sampling and taxonomic revisions are needed. The majority of the Boletineae are confirmed or putatively ectomycorrhizal (ECM), but two putatively mycoparasitic lineages (one lineage of Buchwaldoboletus lignicola and Chalciporus piperatus and the second Pseudoboletus parasiticus) are strongly supported. 相似文献
44.
Sanjana Iyengar Paula R. Williamson Jochen Schmitt Lena Johannsen Ian A. Maher Joseph F. Sobanko Todd V. Cartee Daniel Schlessinger Emily Poon Murad Alam 《Trials》2016,17(1)
BackgroundRosacea is a chronic inflammatory disorder affecting millions of individuals worldwide. Diagnosis is based on signs and symptoms with management and treatment aimed to suppress inflammatory lesions, erythema, and telangiectasia. While many clinical trials of rosacea exist, the lack of consensus in outcome reporting across all trials poses a concern. Proper evaluation and comparison of treatment modalities is challenging. In order to address the inconsistencies present, this project aims to determine a core set of outcomes which should be evaluated in all clinical trials of rosacea.Methods/designThis project will utilize a methodology similar to previous core outcome set research. A long list of outcomes will be extracted over four phases: (1) systematic literature review, (2) patient interviews, (3) other published sources, and (4) stakeholder involvement. Potential outcomes will be examined by the Steering Committee to provide further insight. The Delphi process will then be performed to prioritize and condense the list of outcomes generated. Two homogenous groups of physicians and patients will participate in two consecutive rounds of Delphi surveys. A consensus meeting, composed of physicians, patients, and stakeholders, will be conducted after the Delphi exercise to further select outcomes, taking into account participant scores. By the end of the meeting, members will vote and decide on a final recommended set of core outcomes. For the duration of the study, we will be in collaboration with both the Core Outcome Measures in Effectiveness Trials (COMET) and Cochrane Skin Group - Core Outcome Set Initiative (CSG-COUSIN).DiscussionThis study aims to develop a core outcome set to guide assessment in clinical trials of rosacea. The end-goal is to improve the reliability and consistency of outcome reporting, thereby allowing sufficient evaluation of treatment effectiveness and patient satisfaction.
Electronic supplementary material
The online version of this article (doi:10.1186/s13063-016-1554-3) contains supplementary material, which is available to authorized users. 相似文献45.
46.
47.
Brandon Kuczenski 《Journal of Industrial Ecology》2019,23(3):574-586
Many of the challenges facing knowledge synthesis from life cycle assessment (LCA) studies stem from the inability of study authors and readers to formally agree on the structure and content of the product system models used to perform LCA computations. This article presents a framework for formally disclosing the foreground of an LCA study in a way that permits the computations to be inspected, verified, and reproduced by a reader, provided that the reader has access to the same life cycle inventory and impact characterization resources as the author. The framework can also be used to partition a study into public and private portions, allowing both portions to be critically reviewed but omitting the private information from the disclosure. A disclosure is made up of six components, including three lists of entities in the model and three sparse matrices describing their interconnections. The entity lists make reference to previously‐published resources, including background inventory databases and characterized elementary flows, and the disclosure framework requires both author and reader to agree on the meaning of each of these references. The framework contributes to ongoing efforts within and beyond industrial ecology to improve the reproducibility and verifiability of scholarly works, and if implemented, plots a course toward distributed, platform‐independent computation and validation of LCA results. 相似文献
48.
濒危物种保护是生物多样性保护工作的重要组成部分, 而物种受威胁等级评估则是濒危物种保护的方向指引。经过多年的发展, 物种受威胁等级的评估由定性评估逐渐向定量评估为主、定性评估为辅的方向发展。本文综述了国内植物受威胁等级定量评估系统的研究进展, 同时介绍了国外较为成熟的IUCN红色名录评估系统、CITES评估系统、美国自然保育协会评估系统, 提出未来制定受威胁物种定量评估标准时要兼顾以下方面: (1)等级设置定义要明确、统一且合理; (2)评估标准应该定量化、客观且不冗余; (3)评估系统应该适应不同地理范围, 最好能同时表达出各范围的受威胁等级; (4)评估指标要包含物种动态信息, 能定量分析物种在过去或者未来的变化。此外, 本文认为国内的物种受威胁等级定量评估系统应该形成规范化的大纲, 加大宣传力度, 尽量将理论研究与具体的保护行动结合起来; 同时, 我国还应该采用全球广泛应用的受威胁等级评估系统获取物种受威胁等级, 将国内生物多样性保护工作纳入到全球范围中去。 相似文献
49.
J. Beernaerts B. Nguyen P. Vansteenkiste B. De Baets F.J.A. Deconinck 《Computer methods in biomechanics and biomedical engineering》2019,22(1):64-70
The Qualitative Trajectory Calculus (QTC) is a qualitative spatio-temporal calculus for describing interactions between moving point objects. So far, it remained unclear whether QTC is useful for describing subtle differences, such as between the movements of different parts of a human body. We tested the applicability of QTC to detect differences in the gait patterns of children with or without Developmental Coordination Disorder (DCD). We found that using a combination of three markers (i.e. ankle, toe and trochanter), QTC can achieve a high classification accuracy (i.e. 83.3%) of classifying subjects correctly to either the DCD group or the control group. 相似文献
50.
奶子藤属植物为傣族传统常用药材,含有大量结构复杂,生物活性良好的生物碱类成分。本文针对奶子藤属植物中已分离鉴定的95个生物碱及其体外抗肿瘤和抗HIV活性研究进行了系统综述,为更加合理地开发利用奶子藤属植物资源提供参考依据。 相似文献