全文获取类型
收费全文 | 2294篇 |
免费 | 133篇 |
国内免费 | 35篇 |
出版年
2023年 | 5篇 |
2022年 | 27篇 |
2021年 | 57篇 |
2020年 | 11篇 |
2018年 | 33篇 |
2017年 | 24篇 |
2016年 | 91篇 |
2015年 | 201篇 |
2014年 | 221篇 |
2013年 | 241篇 |
2012年 | 270篇 |
2011年 | 189篇 |
2010年 | 108篇 |
2009年 | 91篇 |
2008年 | 104篇 |
2007年 | 70篇 |
2006年 | 52篇 |
2005年 | 83篇 |
2004年 | 77篇 |
2003年 | 62篇 |
2002年 | 60篇 |
2001年 | 43篇 |
2000年 | 29篇 |
1999年 | 13篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1994年 | 5篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1978年 | 5篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1968年 | 5篇 |
1962年 | 5篇 |
1961年 | 4篇 |
1960年 | 4篇 |
1957年 | 6篇 |
1951年 | 5篇 |
1947年 | 4篇 |
1926年 | 4篇 |
排序方式: 共有2462条查询结果,搜索用时 15 毫秒
161.
Hajo Grundmann David M. Aanensen Cees C. van den Wijngaard Brian G. Spratt Dag Harmsen Alexander W. Friedrich the European Staphylococcal Reference Laboratory Working Group? 《PLoS medicine》2010,7(1)
Background
Staphylococcus aureus is one of the most important human pathogens and methicillin-resistant variants (MRSAs) are a major cause of hospital and community-acquired infection. We aimed to map the geographic distribution of the dominant clones that cause invasive infections in Europe.Methods and Findings
In each country, staphylococcal reference laboratories secured the participation of a sufficient number of hospital laboratories to achieve national geo-demographic representation. Participating laboratories collected successive methicillin-susceptible (MSSA) and MRSA isolates from patients with invasive S. aureus infection using an agreed protocol. All isolates were sent to the respective national reference laboratories and characterised by quality-controlled sequence typing of the variable region of the staphylococcal spa gene (spa typing), and data were uploaded to a central database. Relevant genetic and phenotypic information was assembled for interactive interrogation by a purpose-built Web-based mapping application. Between September 2006 and February 2007, 357 laboratories serving 450 hospitals in 26 countries collected 2,890 MSSA and MRSA isolates from patients with invasive S. aureus infection. A wide geographical distribution of spa types was found with some prevalent in all European countries. MSSA were more diverse than MRSA. Genetic diversity of MRSA differed considerably between countries with dominant MRSA spa types forming distinctive geographical clusters. We provide evidence that a network approach consisting of decentralised typing and visualisation of aggregated data using an interactive mapping tool can provide important information on the dynamics of MRSA populations such as early signalling of emerging strains, cross border spread, and importation by travel.Conclusions
In contrast to MSSA, MRSA spa types have a predominantly regional distribution in Europe. This finding is indicative of the selection and spread of a limited number of clones within health care networks, suggesting that control efforts aimed at interrupting the spread within and between health care institutions may not only be feasible but ultimately successful and should therefore be strongly encouraged. Please see later in the article for the Editors'' Summary 相似文献162.
Jeffrey A. Anderson Li-Hua Ping Oliver Dibben Cassandra B. Jabara Leslie Arney Laura Kincer Yuyang Tang Marcia Hobbs Irving Hoffman Peter Kazembe Corbin D. Jones Persephone Borrow Susan Fiscus Myron S. Cohen Ronald Swanstrom and the Center for HIV/AIDS Vaccine Immunology 《PLoS pathogens》2010,6(8)
HIV-1 is present in anatomical compartments and bodily fluids. Most transmissions occur through sexual acts, making virus in semen the proximal source in male donors. We find three distinct relationships in comparing viral RNA populations between blood and semen in men with chronic HIV-1 infection, and we propose that the viral populations in semen arise by multiple mechanisms including: direct import of virus, oligoclonal amplification within the seminal tract, or compartmentalization. In addition, we find significant enrichment of six out of nineteen cytokines and chemokines in semen of both HIV-infected and uninfected men, and another seven further enriched in infected individuals. The enrichment of cytokines involved in innate immunity in the seminal tract, complemented with chemokines in infected men, creates an environment conducive to T cell activation and viral replication. These studies define different relationships between virus in blood and semen that can significantly alter the composition of the viral population at the source that is most proximal to the transmitted virus. 相似文献
163.
Tweats DJ Blakey D Heflich RH Jacobs A Jacobsen SD Morita T Nohmi T O'Donovan MR Sasaki YF Sofuni T Tice R;IWGT Working Group 《Mutation research》2007,627(1):78-91
In vivo genotoxicity tests play a pivotal role in genotoxicity testing batteries. They are used both to determine if potential genotoxicity observed in vitro is realised in vivo and to detect any genotoxic carcinogens that are poorly detected in vitro. It is recognised that individual in vivo genotoxicity tests have limited sensitivity but good specificity. Thus, a positive result from the established in vivo assays is taken as strong evidence for genotoxic carcinogenicity of the compound tested. However, there is a growing body of evidence that compound-related disturbances in the physiology of the rodents used in these assays can result in increases in micronucleated cells in the bone marrow that are not related to the intrinsic genotoxicity of the compound under test. For rodent bone marrow or peripheral blood micronucleus tests, these disturbances include changes in core body temperature (hypothermia and hyperthermia) and increases in erythropoiesis following prior toxicity to erythroblasts or by direct stimulation of cell division in these cells. This paper reviews relevant data from the literature and also previously unpublished data obtained from a questionnaire devised by the IWGT working group. Regulatory implications of these findings are discussed and flow diagrams have been provided to aid in interpretation and decision-making when such changes in physiology are suspected. 相似文献
164.
165.
Smith JA van den Broek FA Martorell JC Hackbarth H Ruksenas O Zeller W;FELASA Working Group on Ethical Evaluation of Animal Experiments 《Laboratory animals》2007,41(2):143-160
This paper summarizes a more detailed report produced by the Federation of European Laboratory Animal Science Associations (FELASA 2005), which describes and explores a set of principles for the conduct of ethical review of laboratory animal use. It presents a synopsis of results from a questionnaire that elicited information on how each of 20 countries represented in FELASA currently approaches such ethical review. This information suggests that, although local practices differ, there is an emerging consensus on the key elements that any ethical review process should involve. Drawing on the questionnaire findings, this summary also includes a brief discussion to support and amplify a series of recommendations, covering the objectives of ethical review; legal requirements; the scope of work reviewed and the 'level' at which review is approached; general principles for the organization of ethical review processes; the factors considered in the review; needs for ongoing review after initial authorization; participants in the review process; wider impacts of the review process; and strategies that can help to ensure quality and consistency of review outcomes. For further information and examples of current practice, as well as more detailed discussion to support the recommendations, readers are urged to refer to the complete report, available at http://www.lal.org.uk/pdffiles/FELASA_ethics_FULL_Report. pdf or via: http://www.felasa.eu/recommendations.htm. 相似文献
166.
167.
168.
Hawkey CJ Talley NJ Scheiman JM Jones RH Långström G Naesdal J Yeomans ND;NASA/SPACE author group 《Arthritis research & therapy》2007,9(1):R17
Non-steroidal anti-inflammatory drugs (NSAIDs), including selective cyclo-oxygenase-2 (COX-2) inhibitors, cause upper gastrointestinal
(GI) symptoms that are relieved by treatment with esomeprazole. We assessed esomeprazole for maintaining long-term relief
of such symptoms. Six hundred and ten patients with a chronic condition requiring anti-inflammatory therapy who achieved relief
of NSAID-associated symptoms of pain, discomfort, or burning in the upper abdomen during two previous studies were enrolled
and randomly assigned into two identical, multicentre, parallel-group, placebo-controlled studies of esomeprazole 20 mg or
40 mg treatment (NASA2 [Nexium Anti-inflammatory Symptom Amelioration] and SPACE2 [Symptom Prevention by Acid Control with
Esomeprazole] studies; ClinicalTrials.gov identifiers NCT00241514 and NCT00241553, respectively) performed at various rheumatology,
gastroenterology, and primary care clinics. Four hundred and twenty-six patients completed the 6-month treatment period. The
primary measure was the proportion of patients with relapse of upper GI symptoms, recorded in daily diary cards, after 6 months.
Relapse was defined as moderate-to-severe upper GI symptoms (a score of more than or equal to 3 on a 7-grade scale) for 3
days or more in any 7-day period. Esomeprazole was significantly more effective than placebo in maintaining relief of upper
GI symptoms throughout 6 months of treatment. Life-table estimates (95% confidence intervals) of the proportion of patients
with relapse at 6 months (pooled population) were placebo, 39.1% (32.2% to 46.0%); esomeprazole 20 mg, 29.3% (22.3% to 36.2%)
(p = 0.006 versus placebo); and esomeprazole 40 mg, 26.1% (19.4% to 32.9%) (p = 0.001 versus placebo). Patients on either non-selective NSAIDs or selective COX-2 inhibitors appeared to benefit. The frequency
of adverse events was similar in the three groups. Esomeprazole maintains relief of NSAID-associated upper GI symptoms in
patients taking continuous NSAIDs, including selective COX-2 inhibitors. 相似文献
169.
Brain bank of the Brazilian aging brain study group—a milestone reached and more than 1,600 collected brains 总被引:2,自引:0,他引:2
Grinberg LT Ferretti RE Farfel JM Leite R Pasqualucci CA Rosemberg S Nitrini R Saldiva PH Filho WJ;Brazilian Aging Brain Study Group 《Cell and tissue banking》2007,8(2):151-162
INTRODUCTION: Brain banking remains a necessity for the study of aging brain processes and related neurodegenerative diseases. In the present paper, we report the methods applied at and the first results of the Brain Bank of the Brazilian Aging Brain Study Group (BBBABSG) which has two main aims: (1) To collect a large number of brains of elderly comprising non-demented subjects and a large spectrum of pathologies related to aging brain processes, (2) To provide quality material to a multidisciplinar research network unraveling multiple aspects of aging brain processes and related neurodegenerative diseases. METHODS: The subjects are selected from the Sao Paulo Autopsy Service. Brain parts are frozen and fixated. CSF, carotids, kidney, heart and blood are also collected and DNA is extracted. The neuropathological examinations are carried out based on accepted criteria, using immunohistochemistry. Functional status are assessed through a collateral source based on a clinical protocol. Protocols are approved by the local ethics committee and a written informed consent form is obtained. RESULTS: During the first 21 months, 1,602 samples were collected and were classified by Clinical Dementia Rating as CDR0: 65.7%; CDR0.5:12.6%, CDR1:8.2%, CDR2:5.4%, and CDR3:8.1%. On average, the cost for the processing each case stood at 400 US dollars. To date, 14 laboratories have been benefited by the BBBABSG. CONCLUSION: The high percentage of non- demented subjects and the ethnic diversity of this series may be significantly contributive toward aging brain processes and related neurodegenerative diseases understanding since BBBABSG outcomes may provide investigators the answers to some additional questions. 相似文献
170.
Elena Ciani Emiliano Lasagna Mariasilvia D’Andrea Ingrid Alloggio Fabio Marroni Simone Ceccobelli Juan V. Delgado Bermejo Francesca M. Sarti James Kijas Johannes A. Lenstra Fabio Pilla the International Sheep Genomics Consortium 《遗传、选种与进化》2015,47(1)