全文获取类型
收费全文 | 2138篇 |
免费 | 223篇 |
专业分类
2361篇 |
出版年
2023年 | 6篇 |
2022年 | 20篇 |
2021年 | 34篇 |
2020年 | 38篇 |
2019年 | 41篇 |
2018年 | 51篇 |
2017年 | 34篇 |
2016年 | 78篇 |
2015年 | 111篇 |
2014年 | 120篇 |
2013年 | 130篇 |
2012年 | 178篇 |
2011年 | 147篇 |
2010年 | 120篇 |
2009年 | 114篇 |
2008年 | 108篇 |
2007年 | 121篇 |
2006年 | 115篇 |
2005年 | 77篇 |
2004年 | 86篇 |
2003年 | 71篇 |
2002年 | 83篇 |
2001年 | 61篇 |
2000年 | 48篇 |
1999年 | 51篇 |
1998年 | 16篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 12篇 |
1992年 | 28篇 |
1991年 | 20篇 |
1990年 | 27篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有2361条查询结果,搜索用时 15 毫秒
101.
102.
Nobre V Serufo JC Carvalho Odos S Mendonça CL Santos SG Mota EM Gomes D Braga E Antunes CM Lenzi HL Lambertucci JR 《Memórias do Instituto Oswaldo Cruz》2004,99(7):717-720
The association between worm infections and bacterial diseases has only recently been emphasized. This study examined the effect of experimental Angiostrongylus costaricensis infection on endogenous intestinal flora of Swiss Webster mice. Eight mice aging six weeks were selected for this experiment. Four were infected with A. costaricensis and the other four were used as controls. Twenty eight days after the worm infection, all mice in both groups were sacrificed and samples of the contents of the ileum and colon were obtained and cultured for aerobic and anaerobic bacteria. In the mice infected with A. costaricensis there was a significant increase in the number of bacteria of the endogenous intestinal flora, accompanied by a decrease in the number of Peptostreptococcus spp. This alteration in the intestinal flora of mice infected by the nematode may help to understand some bacterial infections described in humans. 相似文献
103.
Allam MF Serrano Del Castillo A Díaz-Molina C Fernández-Crehuet Navaja R 《Revista iberoamericana de micología》2004,21(1):35-38
Invasive pulmonary aspergillosis is a severe infection, with a sharp increase during the last decades. Our study aimed at identification of the epidemiological characteristics of invasive pulmonary aspergillosis during a period of four years. All clinical records with pulmonary isolation of Aspergillus species were reviewed, as a part of surveillance program at Reina Sofia University Hospital, from January 1995 to December 1998. Diagnosis of invasive pulmonary aspergillosis was based on criteria of Centers for Disease Control and Prevention. Of the 50 patients identified 78% were males and 44% were current or ex-smokers. Chronic respiratory diseases were identified in 64% of them, and 60% were receiving immunosuppressives. Twenty percent of our patients had been subjected to lung transplantation and 28% to organ transplantation in general. Only 78% had received specific antifungal treatment and 56% had fatal prognosis. Our findings match with previous studies, apart from the high frequency of lung transplantation in our series. We recommend further studies on large prospective cohorts. 相似文献
104.
105.
The eel and human pathogen Vibrio vulnificus serovar E (biotype 2) is seldom isolated from natural waters, although it can survive in sterilized artificial seawater microcosms for years. The main objective of the present study was to investigate whether aquatic microbiota can limit its survival and recovery from water samples. A set of preliminary experiments of survival in microcosms containing natural seawater and water from eel farms showed that the persistence of this pathogen was mainly controlled by grazing, and secondarily by bacterial competition. The bacterial competition was further analysed in artificial seawater microcosms co-inoculated with selected virulent serovar E (VSE) strains and potential competitors. Competitors included V. vulnificus biotype 1 isolates and strains of selected species that can grow on the selective media designed for V. vulnificus isolation from water samples. Evidences of bacterial competition that was detrimental for VSE recovery were recorded. Thus, some species produced a deleterious effect on VSE strains under starvation, and others were able to use the resources more efficiently under nutrient input. These results suggest that an overgrowth of more efficient competitor bacteria in conventional media used for isolation of V. vulnificus could mask the recovery of VSE strains and explain the scarcity of reports on the isolation of this human and eel pathogen from natural waters. 相似文献
106.
Rapid population decline in red knots: fitness consequences of decreased refuelling rates and late arrival in Delaware Bay 总被引:1,自引:0,他引:1
Baker AJ González PM Piersma T Niles LJ do Nascimento Ide L Atkinson PW Clark NA Minton CD Peck MK Aarts G 《Proceedings. Biological sciences / The Royal Society》2004,271(1541):875-882
Most populations of migrant shorebirds around the world are in serious decline, suggesting that vital condition-dependent rates such as fecundity and annual survival are being affected globally. A striking example is the red knot (Calidris canutus rufa) population wintering in Tierra del Fuego, which undertakes marathon 30,000 km hemispheric migrations annually. In spring, migrant birds forage voraciously on horseshoe crab eggs in Delaware Bay in the eastern USA before departing to breed in Arctic polar deserts. From 1997 to 2002 an increasing proportion of knots failed to reach threshold departure masses of 180-200 g, possibly because of later arrival in the Bay and food shortage from concurrent over-harvesting of crabs. Reduced nutrient storage, especially in late-arriving birds, possibly combined with reduced sizes of intestine and liver during refuelling, had severe fitness consequences for adult survival and recruitment of young in 2000-2002. From 1997 to 2002 known survivors in Delaware Bay were heavier at initial capture than birds never seen again, annual survival of adults decreased by 37% between May 2000 and May 2001, and the number of second-year birds in wintering flocks declined by 47%. Population size in Tierra del Fuego declined alarmingly from 51,000 to 27,000 in 2000-2002, seriously threatening the viability of this subspecies. Demographic modelling predicts imminent endangerment and an increased risk of extinction of the subspecies without urgent risk-averse management. 相似文献
107.
108.
The DNA sequence of chromosome I of an African trypanosome: gene content,chromosome organisation,recombination and polymorphism 总被引:10,自引:1,他引:9
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hall N Berriman M Lennard NJ Harris BR Hertz-Fowler C Bart-Delabesse EN Gerrard CS Atkin RJ Barron AJ Bowman S Bray-Allen SP Bringaud F Clark LN Corton CH Cronin A Davies R Doggett J Fraser A Grüter E Hall S Harper AD Kay MP Leech V Mayes R Price C Quail MA Rabbinowitsch E Reitter C Rutherford K Sasse J Sharp S Shownkeen R MacLeod A Taylor S Tweedie A Turner CM Tait A Gull K Barrell B Melville SE 《Nucleic acids research》2003,31(16):4864-4873
The African trypanosome, Trypanosoma brucei, causes sleeping sickness in humans in sub-Saharan Africa. Here we report the sequence and analysis of the 1.1 Mb chromosome I, which encodes approximately 400 predicted genes organised into directional clusters, of which more than 100 are located in the largest cluster of 250 kb. A 160-kb region consists primarily of three gene families of unknown function, one of which contains a hotspot for retroelement insertion. We also identify five novel gene families. Indeed, almost 20% of predicted genes are members of families. In some cases, tandemly arrayed genes are 99–100% identical, suggesting an active process of amplification and gene conversion. One end of the chromosome consists of a putative bloodstream-form variant surface glycoprotein (VSG) gene expression site that appears truncated and degenerate. The other chromosome end carries VSG and expression site-associated genes and pseudogenes over 50 kb of subtelomeric sequence where, unusually, the telomere-proximal VSG gene is oriented away from the telomere. Our analysis includes the cataloguing of minor genetic variations between the chromosome I homologues and an estimate of crossing-over frequency during genetic exchange. Genetic polymorphisms are exceptionally rare in sequences located within and around the strand-switches between several gene clusters. 相似文献
109.
Villanueva J Fernández-Ballester G Querol E Aviles FX Serrano L 《Journal of molecular biology》2003,330(5):1039-1048
Here, we present a new approach for protein ligand screening based on the use of limited exoproteolysis coupled to MALDI-TOF mass spectrometry, combined with computational modelling and prediction of binding energies. As a test for this combined approach, we have screened a combinatorial library containing 8000 peptides (organized in 60 peptide samples) based on positional scanning format. This library is attached to a poly-Pro framework, and screened against the Abl-SH3 domain. The results obtained demonstrated the validity of the experimental and theoretical approaches in identifying better ligands and in rationalizing the changes in affinity. Exoproteolysis coupled to MALDI-TOF mass spectrometry could be used to screen complex libraries in a fast and efficient way. 相似文献
110.