全文获取类型
收费全文 | 2127篇 |
免费 | 66篇 |
国内免费 | 96篇 |
出版年
2023年 | 9篇 |
2022年 | 42篇 |
2021年 | 43篇 |
2020年 | 29篇 |
2019年 | 98篇 |
2018年 | 65篇 |
2017年 | 62篇 |
2016年 | 34篇 |
2015年 | 70篇 |
2014年 | 124篇 |
2013年 | 105篇 |
2012年 | 105篇 |
2011年 | 89篇 |
2010年 | 56篇 |
2009年 | 76篇 |
2008年 | 64篇 |
2007年 | 84篇 |
2006年 | 78篇 |
2005年 | 72篇 |
2004年 | 56篇 |
2003年 | 38篇 |
2002年 | 35篇 |
2001年 | 47篇 |
2000年 | 30篇 |
1999年 | 37篇 |
1998年 | 36篇 |
1997年 | 33篇 |
1996年 | 29篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 65篇 |
1983年 | 57篇 |
1982年 | 54篇 |
1981年 | 54篇 |
1980年 | 50篇 |
1979年 | 44篇 |
1978年 | 35篇 |
1977年 | 36篇 |
1976年 | 34篇 |
1975年 | 26篇 |
1974年 | 24篇 |
1973年 | 19篇 |
排序方式: 共有2289条查询结果,搜索用时 31 毫秒
101.
Yvonne J. Rosenberg 《Cellular immunology》1981,61(2):416-424
In order to delineate the various roles of T cells in B-cell activation, mice were exposed to a variety of specific or nonspecific T-cell stimuli including mitogens, e.g., concanavalin A, adjuvants, e.g., complete Freund's adjuvant, and colchicine plus nonimmunogenic doses of antigen, anti-lymphocyte serum, and pathogens and their spleens analyzed for total class-specific immunoglobulin-secreting cells as indicators of helper cell generation. The results demonstrate that, depending on the mode of stimulation, markedly different Ig-secreting cell response patterns were induced, differing with respect to their kinetics and the isotype induced. In contrast to polyclonal T-cell stimuli such as concanavalin A and 17X lethal malaria which induced increases in all classes of Ig-recruiting cells, injection of many T-cell-activating agents resulted in the selective production of IgG clones in particular IgG 1. Such findings are discussed in terms of the different mechanisms of T-cell help and provide further evidence for functional heterogeneity in the T-helper-cell pool. 相似文献
102.
R.L. Merriman A. Swanson M.W. Anders N.E. Sladek 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1978,146(1):85-90
A micromethod for the quantitative analysis of caffeine present in small quantities (100 μl) of whole blood is described. It is based on the gas chromatographic—mass spectrometric analysis of chloroform extracts of biological samples. The method is relatively simple, rapid, specific and sensitive, as little as 20 ng of caffeine can be measured. 相似文献
103.
104.
Shi Zhibin Liu Chunguo Yang Huanliang Chen Yan Liu Hua Wei Lili Liu Zaisi Jiang Yongping He Xijun Wang Jingfei 《中国病毒学》2021,36(1):25-32
Fur seal feces-associated circular DNA virus(FSfa CV) is an unclassified circular replication-associated protein(Rep)-encoding single-stranded(CRESS) DNA virus that has been detected in mammals(fur seals and pigs). The biology and epidemiology of the virus remain largely unknown. To investigate the virus diversity among pigs in Anhui Province,China, we pooled 600 nasal samples in 2017 and detected viruses using viral metagenomic methods. From the assembled contigs, 12 showed notably high nucleotide acid sequence similarities to the genome sequences of FSfa CVs. Based on these sequences, a full-length genome sequence of the virus was then obtained using overlapping PCR and sequencing, and the virus was designated as FSfa CV-CHN(Gen Bank No. MK462122). This virus shared 91.3% and 90.9% genome-wide nucleotide sequence similarities with the New Zealand fur seal strain FSfa CV-as50 and the Japanese pig strain FSfa CVJPN1, respectively. It also clustered with the two previously identified FSfa CVs in a unique branch in the phylogenetic tree based on the open reading frame 2(ORF2), Rep-coding gene, and the genome of the reference CRESS DNA viruses.Further epidemiological investigation using samples collected in 2018 showed that the overall positive rate for the virus was 56.4%(111/197) in Anhui Province. This is the first report of FSfa CVs identified in pigs in China, and further epidemiological studies are warranted to evaluate the influence of the virus on pigs. 相似文献
105.
《Journal of structural biology》2021,213(4):107782
Despite their simple body plan, stony corals (order Scleractinia, phylum Cnidaria) can produce massive and complex exoskeletal structures in shallow, tropical and subtropical regions of Earth’s oceans. The species-specific macromorphologies of their aragonite skeletons suggest a highly coordinated biomineralization process that is rooted in their genomes, and which has persisted across major climatic shifts over the past 400 + million years. The mechanisms by which stony corals produce their skeletons has been the subject of interest for at least the last 160 years, and the pace of understanding the process has increased dramatically in the past decade since the sequencing of the first coral genome in 2011. In this review, we detail what is known to date about the genetic basis of the stony coral biomineralization process, with a focus on advances in the last several years as well as ways that physical and chemical tools can be combined with genetics, and then propose next steps forward for the coming decade. 相似文献
106.
Enas A.A. Alabdali Hamed A. Ghramh Essam H. Ibrahim Zubair Ahmad Asma N. Asiri 《Saudi Journal of Biological Sciences》2021,28(4):2278-2284
Apis mellifera jemenitica incorporates a few perceived subspecies that vary in their natural properties and farming qualities. Mitochondrial COI gene sequence (mtCOI) has not been used before for bee identification in the southwestern region of Saudi Arabia. The aim of this work was to study the morphometry and analyzing the mtCOI of all collected bees. The nucleotide sequence of the mtCOI gene was analyzed. Similarity searches and distances between each obtained DNA and sequences available in GenBank were made. Morphometric analysis revealed close similarities among the studied bees, but these similarities are different from those previously indicated in earlier studies of the same region. Molecular studies revealed that the collected bees are similar to each other and some other sequences found in GenBank, but these bees are a new hybrid or subspecies that are different from those previously reported in the same region, indicating the emergence of a new hybrid. 相似文献
107.
Mark McCarthy 《Genes & nutrition》2013,8(5):435-437
Healthier eating is a global challenge for chronic disease control. Food and Health Research in Europe (FAHRE) surveyed research structures and programmes in 32 countries, and reviewed research needs and gaps across nine themes. Food processing and safety research, nutrition and molecular research, and disease-based clinical research are strong; but research is weak on determinants of disease and healthier eating through policies and changing behaviours. Biomedical and commercial research for patents contrast with social research for the public interest. More funding and capacity support should go to social research in the food and health sector. 相似文献
108.
109.
《Systematic and applied microbiology》2020,43(5):126123
The aim of the study was to characterise the diversity and niche-specific colonization of Vibrio spp. in a marine aquaria system by a cultivation-dependent approach. A total of 53 Vibrio spp. isolates were cultured from different ecological niches in a marine aquarium including microplastic (MP) and sandy sediment particles (12 weeks after added sterile to the system), detritus, and the surrounding aquarium water. Based on the 16S rRNA gene sequence phylogeny and multilocus sequence analysis (MLSA) the isolates were assigned to seven different phylotypes. Six phylotypes were identified by high probability to the species level. The highest phylotype diversity was cultured from detritus and water (six out of seven phylotypes), while only two phylotypes were cultured from MP and sediment particles. Genomic fingerprinting indicated an even higher genetic diversity of Vibrio spp. at the strain (genotype) level. Again, the highest diversity of genotypes was recovered from detritus and water while only few partially particle-type specific genotypes were cultured from MP and sediment particles. Phylotype V-2 formed an independent branch in the MLSA tree and could not be assigned to a described Vibrio species. Isolates of this phylotype showed highest 16S rRNA gene sequence similarity to type strains of Vibrio japonicus (98.5%) and Vibrio caribbeanicus (98.4%). A representative isolate, strain THAF100T, was characterised by a polyphasic taxonomic approach and Vibrio aquimaris sp. nov., with strain THAF100T (=DSM 109633T = LMG 31434T = CIP 111709T) as type strain, is proposed as novel species. 相似文献
110.
Yuanqing Hu Yuwei Shang Jinlin Huang Yan Wang Fangzhe Ren Yang Jiao Zhiming Pan Xin-an Jiao 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013