全文获取类型
收费全文 | 2981篇 |
免费 | 198篇 |
国内免费 | 1篇 |
出版年
2023年 | 7篇 |
2022年 | 15篇 |
2021年 | 34篇 |
2020年 | 20篇 |
2019年 | 30篇 |
2018年 | 54篇 |
2017年 | 30篇 |
2016年 | 71篇 |
2015年 | 124篇 |
2014年 | 159篇 |
2013年 | 179篇 |
2012年 | 243篇 |
2011年 | 211篇 |
2010年 | 120篇 |
2009年 | 127篇 |
2008年 | 177篇 |
2007年 | 187篇 |
2006年 | 180篇 |
2005年 | 174篇 |
2004年 | 168篇 |
2003年 | 183篇 |
2002年 | 147篇 |
2001年 | 32篇 |
2000年 | 30篇 |
1999年 | 40篇 |
1998年 | 35篇 |
1997年 | 38篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 24篇 |
1993年 | 22篇 |
1992年 | 24篇 |
1991年 | 28篇 |
1990年 | 21篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1985年 | 13篇 |
1984年 | 16篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1974年 | 6篇 |
1970年 | 5篇 |
1968年 | 6篇 |
排序方式: 共有3180条查询结果,搜索用时 15 毫秒
991.
Aliou Guissé Gilles Boëtsch Axel Ducourneau Deborah Goffner Lamine Gueye 《Comptes rendus biologies》2013,336(5-6):273-277
In the Sahelian zone, the drought phenomenon, combined with anthropic factors (monoculture, bush fires, defect or deficit of manure, overgrazing, etc.), has seriously affected ecological great balances, involving a degradation of the natural resources as well as a fall in agricultural productions, pointing to a process of desertification. To face these challenges, in the course of the 8th ordinary session of the conference of the Heads of States of the African Union held in January 2007 in Addis Ababa (Ethiopia), 11 countries adopted the Panafrican project called the Green Great Wall (GGW). The total objective of the GGW is to contribute i) to the fight against the desert's advance, ii) to the development of the Saharan-Sahelian zones toward a durable management of the natural resources, and iii) to the fight against poverty. It deals with the construction of a set of zones of afforestation crossing the whole African continent in the long term (7000 km of which are in the west). Even if some decisions in the launching phase the GGW must be taken quickly, one cannot do without investment in interdisciplinary research. In particular, associating fundamental research and applied research will allow us to ensure the success in the medium and long term of such a large-scale reforestation project. Research segmented in compartmentalized knowledge fields needed to get adequate tools, among which OHMi Tessékéré, initiated by INNEE (Centre national de la recherche scientifique [CNRS]), in partnership with UCAD, constitutes an example. This suitable scientific tool, capable of action flexibility, of self-financing capacity, anchored in civil society, ready to implement a pragmatic and local interdisciplinarity founded currently on the concept of socio-ecological system (SES), is the one we chose to conduct our studies on the Ferlo arid ecosystems. 相似文献
992.
Roger A. Johnson Ilana Shoshani Carmen Dessauer Gilles Gosselin 《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):839-842
Abstract An enzymatic method was developed for the preparation of unlabeled and [β-32P]-labeled β-L-2′,3′-dd-5′ATP from the monophosphate with near quantitative yields. β-L-2′,3′-dd-5′ATP was a competitive and potent inhibitor of adenylyl cyclases (IC5 ~ 30 nM). Upon uvirradiation β-L-2′,3′-dd-[β-32P]-5′ATP directly crosslinked to a chimeric construct of this enzyme. Data suggest that this is a pre-transition state inhibitor and contrasts with the equipotent 2′,5′-dd-3′ATP, a post-transition state, noncompetitive inhibitor. 相似文献
993.
Improving the yellow pigment content of bread wheat flour by selecting the three homoeologous copies of Psy1 总被引:1,自引:0,他引:1
Catherine Ravel Mireille Dardevet Fanny Leenhardt Jacques Bordes Jean Louis Joseph Marie Reine Perretant Florence Exbrayat Charles Poncet François Balfourier Elisabeth Chanliaud Gilles Charmet 《Molecular breeding : new strategies in plant improvement》2013,31(1):87-99
The yellow pigment content (YPC) of endosperm affects the quality and nutritional value of wheat grain products. Major quantitative trait loci (QTL) for endosperm YPC have been repeatedly mapped on chromosomes 7A and 7B in durum and bread wheats. The genes coding for phytoene synthase (PSY1), which is involved in the biosynthesis of carotenoids, generally co-segregate with these QTL, indicating their role in determining YPC. Here, to study the genetic factors underlying endosperm YPC in bread wheat, the sequence polymorphism of the homoeologous A, B and D copies of genes coding for PSY1, Psy-A1, Psy-B1, and Psy-D1, was studied in a worldwide core collection, which was also phenotyped for flour YPC. Seven novel alleles of Psy-A1 and two novel alleles of Psy-B1 were detected, which confirms the high level of polymorphism of these genes. Two major QTL with respective candidate genes Psy-A1 and Psy-B1 were identified in the distal region of chromosomes 7A and 7B using progeny of a cross between Apache and Ornicar, high and low YPC cultivars, respectively. Association mapping confirms the role of these genes in YPC and shows that the D copy also significantly influences this trait. These results indicate that breeders need to consider all three Psy1 copies when seeking to improve the YPC of wheat endosperm. 相似文献
994.
Bitja-Nyom Arnold Roger Agnèse Jean-François Pariselle Antoine Bilong-Bilong Charles Félix Gilles André Snoeks Jos 《Hydrobiologia》2021,848(16):3779-3803
Hydrobiologia - The group of large five-spotted Hemichromis species from West Africa and Lower Guinea was revised using an integrative approach combining morphometry (measurements,... 相似文献
995.
996.
Messaoudi S Kergourlay G Rossero A Ferchichi M Prévost H Drider D Manai M Dousset X 《International microbiology》2011,14(2):103-110
Bacteriocins produced by Lactobacillus salivarius have been recently recognized as a natural means to control Campylobacter and Salmonella in live poultry. This finding is of relevance since Campylobacter jejuni and Campylobacter coli are the predominant species isolated from poultry that are associated with human campylobacteriosis. In the present work, lactic acid bacteria (LAB) isolated from the cecum of twenty Tunisian chickens were identified and those isolates with antagonism against Campylobacter were further characterized. Following their preliminary confirmation as LAB, 150 strains were identified by combining morphological criteria, biochemical tests, and molecular methods, the latter inluding intergenic 16S- 23S PCR, specific lactobacilli PCR, and a biphasic approach. Most of the LAB isolated belonged to the genus Lactobacillus, among them Lb. sakei (33.3%), Lb. salivarius (19.4%), Lb. reuteri (8.6%), and Lb. curvatus (8.6%). The other LAB strains included those of the genus Weissella (16.7%), Enterococcus faecalis (5.3%), Leuconostoc mesenteroides (2.7%), Lactococcus graviae (2.7%), and Streptococcus sp. (2.7%). The Lactobacilli strains were tested for their antagonism against C. jejuni and C. coli. The activity of three of them, Lb. salivarius SMXD51, Lb. salivarius MMS122, and Lb. salivarius MMS151, against the aforementioned target strains could be ascribed to the production of bacteriocins. 相似文献
997.
Goux A Feillet-Coudray C Jover B Fouret G Bargnoux AS Cassan C Richard S Badiou S Cristol JP 《Free radical research》2011,45(4):454-460
Abstract Cardiovascular disease is a frequent complication inducing mortality in chronic kidney disease (CKD) patients, which can be determined by both traditional risk factors and non-traditional risk factors such as malnutrition and oxidative stress. This study aimed to investigate the role of oxidative stress in uremia-induced cardiopathy in an experimental CKD model. CKD was induced in Sprague-Dawley rats by a 4-week diet supplemented in adenine, calcium and phosphorous and depleted in proteins. CKD was associated with a 3-fold increase in superoxide anion production from the NADPH oxidase in the left ventricle, but the maximal activity of mitochondrial respiratory chain complexes was not different. Although manganese mitochondrial SOD activity decreased, total SOD activity was not affected and catalase or GPx activities were increased, strengthening the major role of NADPH oxidase in superoxide anion output. Superoxide anion output was associated with enhanced expression of osteopontin (×7.7) and accumulation of pro-collagen type I (×3.7). To conclude, the increased activity of NADPH oxidase during CKD is associated with protein modifications which could activate a pathway leading to cardiac remodelling. 相似文献
998.
Roux AL Ray A Pawlik A Medjahed H Etienne G Rottman M Catherinot E Coppée JY Chaoui K Monsarrat B Toubert A Daffé M Puzo G Gaillard JL Brosch R Dulphy N Nigou J Herrmann JL 《Cellular microbiology》2011,13(5):692-704
Changes in the cell envelope composition of mycobacteria cause major changes in cytokine profiles of infected antigen presenting cells. We describe here the modulation of inflammatory responses by Mycobacterium abscessus, an emerging pathogen in cystic fibrosis. M. abscessus is able to switch from a smooth (S) to a rough (R) morphotype by the loss of a surface glycopeptidolipid. R variants are associated with severe clinical forms and a 'hyper-proinflammatory' response in ex vivo and in vivo models. Using partitioning of cell surface components we found that a complex fraction, more abundant in R variants than in S variants, made a major contribution to the TLR-2-dependent hyper-proinflammatory response induced by R variants. Lipoproteins were the main TLR-2 agonists in this fraction, consistent with the larger amounts of 16 lipoproteins in cell surface extracts from R variants; 15 out of 16 being more strongly induced in R variant than in S variant. Genetic interruption of glycopeptidolipid pathway in wild-type S variant resulted in R phenotype with similar induction of lipoprotein genes. In conclusion, R morphotype in M. abscessus is associated with increased synthesis/exposure at the cell surface of lipoproteins, these changes profoundly modifying the innate immune response through TLR-2-dependent mechanisms. 相似文献
999.
Amathieu R Nahon P Triba M Bouchemal N Trinchet JC Beaugrand M Dhonneur G Le Moyec L 《Journal of proteome research》2011,10(7):3239-3245
Assessment of chronic liver failure (CLF) in cirrhotic patients is needed to make therapeutic decisions. A biological score is usually performed, using the Model for End-Stage Liver Disease (MELD), to evaluate CLF. Nevertheless, MELD does not take into account metabolic perturbations produced by liver-function impairment. In contrast, metabolomics can investigate many metabolic perturbations within biological systems. The purpose of this study was to assess whether metabolomic profiles of serum, obtained by proton NMR spectroscopy from cirrhotic patients, are affected by the severity of CLF. An orthogonal projection to latent-structure analysis was performed to compare MELD scores and NMR spectra of 124 patients with cirrhosis. The statistical model obtained showed a good explained variance (R(2)X = 0.87 and R(2)Y = 0.86) and a good predictability (Q(2)Y = 0.64). Metabolomic profiles showed significant differences regarding various metabolites depending of severity of CLF: levels of high-density lipoprotein and phosphocholine resonances were significantly higher in patients with mild CLF compared to severe CLF. Other metabolites such as lactate, pyruvate, glucose, amino acids, and creatinine were significantly higher in patients with severe CLF than mild CLF. Our conclusion is that metabolomic NMR analysis provides new insights into metabolic processes related to the severity of hepatic function impairment in cirrhosis. 相似文献
1000.
Numerous matrices for the growth of human embryonic stem cells (hESC) in vitro have been described. However, their exact composition is typically unknown. Information on the components of these matrices will aid in the development of a fully defined growth surface for hESCs. These matrices typically consist of mixture of proteins present in a wide range of abundance making their characterization challenging. In this study, we performed the proteomic analysis of five previously uncharacterized matrices: CellStart, Human Basement Membrane Extract (Human BME), StemXVivo, Bridge Human Extracellular Matrix (BridgeECM), and mouse embryonic fibroblast conditioned matrix (MEF-CMTX). Based on a proteomics protocol optimized using lysates from HeLa cells, we undertook the analysis of the five complex extracellular matrix (ECM) samples using a combination of strong anion and cation exchange chromatography and SDS-PAGE. For each of these matrices, we identify numerous proteins, indicating their complex nature. We also compared these results with a similar proteomics analysis of the growth matrix, Matrigel?. From these analyses, we observed that fibronectin is a primary component of nearly all hESC supportive matrices. This observation led to the investigation of the suitability of fibronectin as a defined ECM for the growth of hESCs. We found that fibronectin promotes the maintenance of pluripotent H9 and CA1 hESCs in an undifferentiated state using mTeSR1 medium. This finding validates the utility of characterizing matrices used for hESC growth in revealing ECM components required for culturing hESCs in a universally applicable defined system. 相似文献