全文获取类型
收费全文 | 4802篇 |
免费 | 382篇 |
专业分类
5184篇 |
出版年
2023年 | 39篇 |
2022年 | 87篇 |
2021年 | 136篇 |
2020年 | 83篇 |
2019年 | 111篇 |
2018年 | 148篇 |
2017年 | 117篇 |
2016年 | 193篇 |
2015年 | 293篇 |
2014年 | 250篇 |
2013年 | 354篇 |
2012年 | 403篇 |
2011年 | 410篇 |
2010年 | 200篇 |
2009年 | 185篇 |
2008年 | 264篇 |
2007年 | 252篇 |
2006年 | 233篇 |
2005年 | 191篇 |
2004年 | 181篇 |
2003年 | 167篇 |
2002年 | 171篇 |
2001年 | 72篇 |
2000年 | 44篇 |
1999年 | 54篇 |
1998年 | 43篇 |
1997年 | 36篇 |
1996年 | 34篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 24篇 |
1991年 | 27篇 |
1990年 | 31篇 |
1989年 | 16篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1979年 | 15篇 |
1977年 | 9篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1973年 | 12篇 |
1971年 | 10篇 |
1968年 | 9篇 |
排序方式: 共有5184条查询结果,搜索用时 15 毫秒
121.
Francesca Giampieri Md Soriful Islam Stefania Greco Massimiliano Gasparrini Tamara Y. Forbes Hernandez Giovanni Delli Carpini Stefano Raffaele Giannubilo Andrea Ciavattini Bruno Mezzetti Luca Mazzoni Franco Capocasa Mario Castellucci Maurizio Battino Pasquapina Ciarmela 《Journal of cellular physiology》2019,234(5):7622-7633
Uterine leiom yomas are benign tumors highly prevalent in reproductive women. In thecurrent study, initially, we aimed to screen five different strawberry cultivars (Alba, Clery, Portola, Tecla, and Romina) to identify efficient cultivars in terms of phytochemical characterization and biological properties by measuring phenolic and anthocyanin content as well as antioxidant capacity, and by measuring apoptotic rate and reactive oxygen species (ROS) production in uterine leiomyoma cells. Next, we focused on the most efficient ones, cultivar Alba (A) and Romina (R) as well as Romina anthocyanin (RA) fraction for their ability to regulate oxidative phosphorylation (oxygen consumption rate [OCR]) glycolysis (extracellular acidification rate [ECAR]), and also fibrosis. Leiomyoma and myometrial cells were treated with a methanolic extract of A and R (250 μg/ml) or with RA (50 μg/ml) for 48 hr to measure OCR and ECAR, as well as gene expression associated with fibrosis. In the leiomyoma cells, RA was more effective in inducing apoptosis and increasing intracellular ROS levels, followed by R and A. In myometrial cells, all strawberry treatments increased the cellular viability and decreased ROS concentrations. Leiomyoma cells showed also a significant decrease in ECAR, especially after RA treatment, while OCR was slightly increased in both myometrial and leiomyoma cells. R and RA treatment significantly decreased collagen 1A1, fibronectin, versican, and activin A messenger RNA expression in leiomyoma cells. In conclusion, this study suggests that Romina, or its anthocyanin fraction, can be developed as a therapeutic and/or preventive agent for uterine leiomyomas, confirming the healthy effects exerted by these fruits and their bioactive compounds. 相似文献
122.
Rapid identification of lettuce seed germination mutants by bulked segregant analysis and whole genome sequencing 总被引:1,自引:0,他引:1 下载免费PDF全文
Heqiang Huo Isabelle M. Henry Eric R. Coppoolse Miriam Verhoef‐Post Johan W. Schut Han de Rooij Aat Vogelaar Ronny V.L. Joosen Leo Woudenberg Luca Comai Kent J. Bradford 《The Plant journal : for cell and molecular biology》2016,88(3):345-360
Lettuce (Lactuca sativa) seeds exhibit thermoinhibition, or failure to complete germination when imbibed at warm temperatures. Chemical mutagenesis was employed to develop lettuce lines that exhibit germination thermotolerance. Two independent thermotolerant lettuce seed mutant lines, TG01 and TG10, were generated through ethyl methanesulfonate mutagenesis. Genetic and physiological analyses indicated that these two mutations were allelic and recessive. To identify the causal gene(s), we applied bulked segregant analysis by whole genome sequencing. For each mutant, bulked DNA samples of segregating thermotolerant (mutant) seeds were sequenced and analyzed for homozygous single‐nucleotide polymorphisms. Two independent candidate mutations were identified at different physical positions in the zeaxanthin epoxidase gene (ABSCISIC ACID DEFICIENT 1/ZEAXANTHIN EPOXIDASE, or ABA1/ZEP) in TG01 and TG10. The mutation in TG01 caused an amino acid replacement, whereas the mutation in TG10 resulted in alternative mRNA splicing. Endogenous abscisic acid contents were reduced in both mutants, and expression of the ABA1 gene from wild‐type lettuce under its own promoter fully complemented the TG01 mutant. Conventional genetic mapping confirmed that the causal mutations were located near the ZEP/ABA1 gene, but the bulked segregant whole genome sequencing approach more efficiently identified the specific gene responsible for the phenotype. 相似文献
123.
Raffaella Ponassi Barbara Biasotti Valeria Tomati Silvia Bruno Alessandro Poggi Davide Malacarne Guido Cimoli Annalisa Salis Sarah Pozzi Maurizio Miglino Gianluca Damonte Pietro Cozzini Francesca Spyrakis Barbara Campanini Luca Bagnasco Nicoletta Castagnino Lorenzo Tortolina Anna Mumot Francesco Frassoni Antonio Daga Michele Cilli Federica Piccardi Ilaria Monfardini Miriam Perugini Gabriele Zoppoli Cristina D’Arrigo Raffaele Pesenti Silvio Parodi 《Cell cycle (Georgetown, Tex.)》2012,11(19):3703
124.
Sébastien Besseau Franziska Kellner Arnaud Lanoue Antje M.K. Thamm Vonny Salim Bernd Schneider Fernando Geu-Flores René H?fer Grégory Guirimand Anthony Guihur Audrey Oudin Ga?lle Glevarec Emilien Foureau Nicolas Papon Marc Clastre Nathalie Giglioli-Guivarc’h Benoit St-Pierre Danièle Werck-Reichhart Vincent Burlat Vincenzo De Luca Sarah E. O’Connor Vincent Courdavault 《Plant physiology》2013,163(4):1792-1803
125.
126.
Florio M Leto K Muzio L Tinterri A Badaloni A Croci L Zordan P Barili V Albieri I Guillemot F Rossi F Consalez GG 《Development (Cambridge, England)》2012,139(13):2308-2320
By serving as the sole output of the cerebellar cortex, integrating a myriad of afferent stimuli, Purkinje cells (PCs) constitute the principal neuron in cerebellar circuits. Several neurodegenerative cerebellar ataxias feature a selective cell-autonomous loss of PCs, warranting the development of regenerative strategies. To date, very little is known as to the regulatory cascades controlling PC development. During central nervous system development, the proneural gene neurogenin 2 (Neurog2) contributes to many distinct neuronal types by specifying their fate and/or dictating development of their morphological features. By analyzing a mouse knock-in line expressing Cre recombinase under the control of Neurog2 cis-acting sequences we show that, in the cerebellar primordium, Neurog2 is expressed by cycling progenitors cell-autonomously fated to become PCs, even when transplanted heterochronically. During cerebellar development, Neurog2 is expressed in G1 phase by progenitors poised to exit the cell cycle. We demonstrate that, in the absence of Neurog2, both cell-cycle progression and neuronal output are significantly affected, leading to an overall reduction of the mature cerebellar volume. Although PC fate identity is correctly specified, the maturation of their dendritic arbor is severely affected in the absence of Neurog2, as null PCs develop stunted and poorly branched dendrites, a defect evident from the early stages of dendritogenesis. Thus, Neurog2 represents a key regulator of PC development and maturation. 相似文献
127.
A taxonomic survey of lactic acid bacteria isolated from wheat (Triticum durum) kernels and non-conventional flours 总被引:2,自引:0,他引:2
Corsetti A Settanni L Chaves López C Felis GE Mastrangelo M Suzzi G 《Systematic and applied microbiology》2007,30(7):561-571
In order to explore the correspondence between raw material- and mature sourdough-lactic acid bacterial (LAB) communities, 59 Italian wheat (Triticum durum) grain samples, one bran and six non-conventional flour samples were analyzed through a culture-dependent approach. The highest cell count by an agar medium specific for LAB was 2.16 log CFU/g. From about 2300 presumptive LAB (Gram-positive and catalase-negative) colonies collected, a total of 356 isolates were subjected to identification by a genetic polyphasic strategy consisting of RAPD-PCR analysis, partial 16S rRNA gene sequencing, species-specific and multiplex PCRs. The isolates were recognized as 137 strains belonging to Aerococcus, Enterococcus, Lactobacillus, Lactococcus and Pediococcus genera and a phylogram based on partial 16S rRNA genes was constructed. The species most frequently found were Enterococcus faecium, Enterococcus mundtii and Lactobacillus graminis, which are not generally reported to be typical in mature sourdoughs. 相似文献
128.
Parvaneh Nikpour Modjtaba Emadi Baygi Christine Steinhoff Christiane Hader Anna C. Luca Seyed J. Mowla Wolfgang A. Schulz 《Journal of cellular and molecular medicine》2011,15(5):1210-1224
The RNA‐binding protein Musashi1 (MSI1) is a marker of progenitor cells in the nervous system functioning as a translational repressor. We detected MSI1 mRNA in several bladder carcinoma cell lines, but not in cultured normal uroepithelial cells, whereas the paralogous MSI2 gene was broadly expressed. Knockdown of MSI1 expression by siRNA induced apoptosis and a severe decline in cell numbers in 5637 bladder carcinoma cells. Microarray analysis of gene expression changes after MSI1 knockdown significantly up‐regulated 735 genes, but down‐regulated only 31. Up‐regulated mRNAs contained a highly significantly greater number and density of Musashi binding sites. Therefore, a much larger set of mRNAs may be regulated by Musashi1, which may affect not only their translation, but also their turnover. The study confirmed p21CIP1 and Numb proteins as targets of Musashi1, suggesting additionally p27KIP1 in cell‐cycle regulation and Jagged‐1 in Notch signalling. A significant number of up‐regulated genes encoded components of stress granules (SGs), an organelle involved in translational regulation and mRNA turnover, and impacting on apoptosis. Accordingly, heat shock induced SG formation was augmented by Musashi1 down‐regulation. Our data show that ectopic MSI1 expression may contribute to tumorigenesis in selected bladder cancers through multiple mechanisms and reveal a previously unrecognized function of Musashi1 in the regulation of SG formation. 相似文献
129.
Emiliano Ukmar Corrado Battisti Luca Luiselli Marco A. Bologna 《Biodiversity and Conservation》2007,16(12):3287-3300
Breeding bird communities in burnt and unburnt residual pinewoods were studied over 3 years by line-transect method, following
a catastrophic fire event in Castelfusano (Rome, Central Italy; July 2000). We applied bootstrap procedures to evaluate whether
the observed data were true or just produced by chance, and then examined the emerging patterns at three levels: community,
guild and species levels. At the community level, fire acted on breeding bird communities by altering especially the total
abundance patterns: the species abundance decreased in the burnt pinewood compared to the residual one, but other parameters
were not significantly affected by fire. As a consequence of fire, the destruction and structural simplification of the canopy
and shrubby component, as well as the increase of edge habitat and patchiness at landscape scale, induced a turnover in species
between pinewoods. Species turnover was higher at the burnt than at the residual pinewoods, during all the 3 years of study.
At the guild level, the forest species decreased strongly in terms of richness and abundance in the burnt pinewoods, contrary
to the edge and open habitat species which increased in terms of richness, abundance and evenness. Edge species showed the
highest turnover in burnt pinewood during the whole period of study. At species level, after an a priori subdivision (based
on bibliographic search) of the various species in two ecological guilds (forest versus edge species), it was found that an
a posteriori statistical analysis confirmed the expected trend, i.e. that the species which decreased significantly in burnt
pinewood were essentially the forest species, whereas the species which increased were essentially the edge/open habitat ones.
Overall, in order to investigate the effects of fire catastrophes on birds, the guild approach seems more exhaustive than
the taxonomic community approach, where intrinsic confounding trends are present. 相似文献
130.
Fabbri E Miquel C Lucchini V Santini A Caniglia R Duchamp C Weber JM Lequette B Marucco F Boitani L Fumagalli L Taberlet P Randi E 《Molecular ecology》2007,16(8):1661-1671
Wolves in Italy strongly declined in the past and were confined south of the Alps since the turn of the last century, reduced in the 1970s to approximately 100 individuals surviving in two fragmented subpopulations in the central-southern Apennines. The Italian wolves are presently expanding in the Apennines, and started to recolonize the western Alps in Italy, France and Switzerland about 16 years ago. In this study, we used a population genetic approach to elucidate some aspects of the wolf recolonization process. DNA extracted from 3068 tissue and scat samples collected in the Apennines (the source populations) and in the Alps (the colony), were genotyped at 12 microsatellite loci aiming to assess (i) the strength of the bottleneck and founder effects during the onset of colonization; (ii) the rates of gene flow between source and colony; and (iii) the minimum number of colonizers that are needed to explain the genetic variability observed in the colony. We identified a total of 435 distinct wolf genotypes, which showed that wolves in the Alps: (i) have significantly lower genetic diversity (heterozygosity, allelic richness, number of private alleles) than wolves in the Apennines; (ii) are genetically distinct using pairwise F(ST) values, population assignment test and Bayesian clustering; (iii) are not in genetic equilibrium (significant bottleneck test). Spatial autocorrelations are significant among samples separated up to c. 230 km, roughly correspondent to the apparent gap in permanent wolf presence between the Alps and north Apennines. The estimated number of first-generation migrants indicates that migration has been unidirectional and male-biased, from the Apennines to the Alps, and that wolves in southern Italy did not contribute to the Alpine population. These results suggest that: (i) the Alps were colonized by a few long-range migrating wolves originating in the north Apennine subpopulation; (ii) during the colonization process there has been a moderate bottleneck; and (iii) gene flow between sources and colonies was moderate (corresponding to 1.25-2.50 wolves per generation), despite high potential for dispersal. Bottleneck simulations showed that a total of c. 8-16 effective founders are needed to explain the genetic diversity observed in the Alps. Levels of genetic diversity in the expanding Alpine wolf population, and the permanence of genetic structuring, will depend on the future rates of gene flow among distinct wolf subpopulation fragments. 相似文献