全文获取类型
收费全文 | 2418篇 |
免费 | 151篇 |
国内免费 | 12篇 |
专业分类
2581篇 |
出版年
2023年 | 16篇 |
2022年 | 50篇 |
2021年 | 129篇 |
2020年 | 60篇 |
2019年 | 60篇 |
2018年 | 68篇 |
2017年 | 65篇 |
2016年 | 85篇 |
2015年 | 133篇 |
2014年 | 161篇 |
2013年 | 182篇 |
2012年 | 164篇 |
2011年 | 158篇 |
2010年 | 118篇 |
2009年 | 91篇 |
2008年 | 104篇 |
2007年 | 118篇 |
2006年 | 97篇 |
2005年 | 80篇 |
2004年 | 66篇 |
2003年 | 65篇 |
2002年 | 63篇 |
2001年 | 48篇 |
2000年 | 43篇 |
1999年 | 43篇 |
1998年 | 10篇 |
1997年 | 18篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 25篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 17篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1980年 | 8篇 |
1978年 | 11篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1971年 | 6篇 |
1967年 | 9篇 |
排序方式: 共有2581条查询结果,搜索用时 0 毫秒
991.
992.
S Isomura T Morishima K Nishikawa N Hanada M Rahman M Terashima S Kido S Ueda M Takahashi 《Biken journal》1986,29(1):19-26
Antibody persistence was measured in 39 children in an open community 12-13 years after immunization against measles with further attenuated live vaccine, Biken CAM. Serum samples of the children taken every two or three years after vaccination had higher, lower, or the same HI antibody titers as those in samples taken 6 weeks after vaccination. These differences reflected a decrease in the titer in some children and subclinical natural reinfection in others. However, all the children still retained detectable antibody in 12 or 13 years after vaccination, indicating long-term persistence of immunity after immunization with Biken CAM vaccine. For evaluation of the protective efficacy of the vaccine, matched controls were studied during the same period. Serological examination revealed that 97.5% of the controls were infected with measles and contracted the disease. In contrast, none of the vaccinees developed clinical infection after close contact with measles patients. 相似文献
993.
Alam MS Igawa T Khan MM Islam MM Kuramoto M Matsui M Kurabayashi A Sumida M 《Molecular phylogenetics and evolution》2008,48(2):515-527
To elucidate the species composition, genetic divergence, evolutionary relationships, and divergence time of Hoplobatrachus and Euphlyctis frogs (subfamily Dicroglossinae, family Ranidae) in Bangladesh and other Asian countries, we analyzed the mitochondrial Cyt b, 12S, and 16S rRNA genes of 252 specimens. Our phylogenetic analyses showed 13 major clades corresponding to several cryptic species as well as to nominal species in the two genera. The results suggested monophyly of Asian Hoplobatrachus species, but the position of African Hoplobatrachus occipitalis was not clarified. Nucleotide divergence and phylogenetic data suggested the presence of allopatric cryptic species allied to Euphlyctis hexadactylus in Sundarban, Bangladesh and several parapatric cryptic species in the Western Ghats, India. The presence of at least two allopatric cryptic species among diverged Euphlyctis cyanophlyctis in Bangladesh, India, and Sri Lanka was also suggested. In some cases, our estimated divergence times matched the paleogeological events of South and Southeast Asian regions that may have led to the divergence of Hoplobatrachus and Euphlyctis taxa. Especially, land formation at Bangladesh (15–10 Ma) may have allowed the spread of these frog taxa to Southeast Asian areas, and the aridification of central India (5.1–1.6 Ma) might have affected the gene flow of widely distributed species. The present study revealed prior underestimation of the richness of the amphibian fauna in this region, indicating the possible occurrence of many cryptic species among these groups. 相似文献
994.
In the loach Misgurnus anguillicaudatue, the asexual lineage, which produces unreduced clonal diploid eggs, has been identified. Among 833 specimens collected from
54 localities in Japan and two localities in China, 82 candidates of other lineage(s) of cryptic clones were screened by examining
RFLP (restriction fragment length polymorphism)-PCR haplotypes in the control region of mtDNA. This analysis was performed
because triploid loaches arise from the accidental incorporation of the sperm nucleus into unreduced diploid eggs of a clone.
The categorization of members belonging to three newly identified lineages (clones 2–4) and the previously identified clonal
lineage (clone 1) was verified by evaluating the genetic identity between two or more individuals from each clonal lineage
based on RAPD (random amplified polymorphic DNA)-PCR and multilocus DNA fingerprints. We detected 75 haplotypes by observing
the nucleotide status at variable sites from the control region of mtDNA. Phylogenic trees constructed from such sequences
showed two highly diversified clades, A and B, that were beyond the level common for interspecific genetic differentiation.
That result suggests that M. anguillicaudatus in Japan is not a single species entity. Two clone-specific mtDNA sequences were included in clade A, and the loaches with
such sequences may be the maternal origin of the clones.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
995.
Erfan Aref-Eshghi Yuhua Zhang Deborah Hart Ana M. Valdes Andrew Furey Glynn Martin Guang Sun Proton Rahman Nigel Arden Tim D. Spector Guangju Zhai 《PloS one》2014,9(5)
Background
A newly-described syndrome called Aneurysm-Osteoarthritis Syndrome (AOS) was recently reported. AOS presents with early onset osteoarthritis (OA) in multiple joints, together with aneurysms in major arteries, and is caused by rare mutations in SMAD3. Because of the similarity of AOS to idiopathic generalized OA (GOA), we hypothesized that SMAD3 is also associated with GOA and tested the hypothesis in a population-based cohort.Methods
Study participants were derived from the Chingford study. Kellgren-Lawrence (KL) grades and the individual features of osteophytes and joint space narrowing (JSN) were scored from radiographs of hands, knees, hips, and lumbar spines. The total KL score, osteophyte score, and JSN score were calculated and used as indicators of the total burden of radiographic OA. Forty-one common SNPs within SMAD3 were genotyped using the Illumina HumanHap610Q array. Linear regression modelling was used to test the association between the total KL score, osteophyte score, and JSN score and each of the 41 SNPs, with adjustment for patient age and BMI. Permutation testing was used to control the false positive rate.Results
A total of 609 individuals were included in the analysis. All were Caucasian females with a mean age of 60.9±5.8. We found that rs3825977, with a minor allele (T) frequency of 20%, in the last intron of SMAD3, was significantly associated with total KL score (β = 0.14, Ppermutation = 0.002). This association was stronger for the total JSN score (β = 0.19, Ppermutation = 0.002) than for total osteophyte score (β = 0.11, Ppermutation = 0.02). The T allele is associated with a 1.47-fold increased odds for people with 5 or more joints to be affected by radiographic OA (Ppermutation = 0.046).Conclusion
We found that SMAD3 is significantly associated with the total burden of radiographic OA. Further studies are required to reveal the mechanism of the association. 相似文献996.
Archita Barua Somnath Roy Gautam Handique Foridur Rahman Bora Azizur Rahman Dwiban Pujari Narayanannair Muraleedharan 《Proceedings of the Zoological Society》2017,70(1):92-96
The tea red spider mite, Oligonychus coffeae Nietner (Tetranychidae), is an economically important pest of agricultural and ornamental crops and considered one of the major pests of tea plants in North-east India. In view of increasing resistance recorded in insect and mite pests against pesticides, a study was conducted to determine the acaricidal, antiovipositional, repellent and ovicidal activities of clove oil (an essential oil from the clove plant, Syzygium aromaticum L. Merr. & Perry: Myrtaceae) against tea-red-spider-mite. Mortality of O. coffeae varied with the concentrations and the duration of exposure time of the mites after application of oil. Rate of deposition of eggs by mites on treated leaf surfaces as well as the viability rate of eggs decreased significantly. In addition, certain concentrations of clove oil have been proved effective against adult mites. 相似文献
997.
Islam MS Jahid MI Rahman MM Rahman MZ Islam MS Kabir MS Sack DA Schoolnik GK 《Microbiology and immunology》2007,51(4):369-379
The role of biofilm as a microenvironment of plankton-associated Vibrio cholerae was investigated using plexiglass as a bait. A total of 72 biofilm samples were tested using culture, direct fluorescent antibody (DFA) and molecular techniques following standard procedures. Culturable V. cholerae (smooth and rugose variants) were isolated from 33% of the samples. V. cholerae O1 were detected by FA technique throughout the year except April and June. All V. cholerae O1 isolates were positive for tcpA, ctxA and ace genes while V. cholerae non-O1, non-O139 isolates lacked these genes. V. cholerae O1 (both Inaba and Ogawa) strains had identical ribotype pattern (R1), but V. cholerae non-O1, non-O139 had different ribotype patterns. All V. cholerae O1 strains were resistant to vibrio-static compound (O/129). All V. cholerae O1 except one were resistant to trimethoprime-sulphamethoxazole, streptomycin, nalidixic acid and furazolidone but sensitive to ciprofloxacin, and tetracycline. This study indicates that plexiglass can act as a bait to form biofilm, a microenvironment that provides shelter for plankton containing V. cholerae in the aquatic environment of Bangladesh. 相似文献
998.
Md. Anowar Khasru Parvez Rabeya Nahar Ferdous Md. Shahedur Rahman Sohidul Islam 《Journal of Genetic Engineering and Biotechnology》2018,16(2):473-478
Methicillin-resistant Staphylococcus aureus (MRSA) has long been a common pathogen in healthcare facilities, but now, it has emerged as a problematic pathogen in the community setting as well. This study reported source, diagnosis and treatment of HA-MRSA and CA-MRSA.A total of sixty-five clinical samples (urine, pus, wound swab) were collected from clinical origin of Dhaka city, Bangladesh. All the isolates were tested phenotypically by conventional methods and genotypically by PCR targeting nuc, pvl and mecA genes. Finally sequencing was carried out for pvl gene to know the mutagenic variation or any amino acid changes in pvl gene. Chi square test was employed for statistical analysis. Patients of age group 51–60?years are more susceptible (46.15%) to MRSA, CA-MRSA or HA-MRSA infection. Female are (32.30%) more susceptible to MRSA infection. Among 65 isolates 53 isolates identified phenotypically as S. aureus. These were positive for amplification of nuc (270?bp) gene of S. aureus. Moreover, among 53 isolates 33 phenotypically considered as MRSA and 38 (72%) showed positive amplification for mecA (162?bp) gene. Among 38 MRSA isolates 22 (57.89%) confirmed as CA-MRSA and 16 (42.10%) as HA-MRSA. Finally, sequence analysis for lukS/F-PV genes from 4 representative isolates detected a new single nucleotide polymorphism in comparison with the control sequence. However, no amino acid changes were found. Statistical analysis showed HA-MRSA isolates were more commonly found in urine sample and CA-MRSA in pus and wound swab. CA-MRSA isolates were more resistant to tested antibiotics than HA-MRSA. 相似文献
999.
1000.
Chean Yeah Yong Swee Keong Yeap Zee Hong Goh Kok Lian Ho Abdul Rahman Omar Wen Siang Tan 《Applied and environmental microbiology》2015,81(3):882-889
Hepatitis B virus (HBV) is a deadly pathogen that has killed countless people worldwide. Saccharomyces cerevisiae-derived HBV vaccines based upon hepatitis B surface antigen (HBsAg) is highly effective. However, the emergence of vaccine escape mutants due to mutations on the HBsAg and polymerase genes has produced a continuous need for the development of new HBV vaccines. In this study, the “a” determinant within HBsAg was displayed on the recombinant capsid protein of Macrobrachium rosenbergii nodavirus (MrNV), which can be purified easily in a single step through immobilized metal affinity chromatography (IMAC). The purified protein self-assembled into virus-like particles (VLPs) when observed under a transmission electron microscope (TEM). Immunization of BALB/c mice with this chimeric protein induced specific antibodies against the “a” determinant. In addition, it induced significantly more natural killer and cytotoxic T cells, as well as an increase in interferon gamma (IFN-γ) secretion, which are vital for virus clearance. Collectively, these findings demonstrated that the MrNV capsid protein is a potential carrier for the HBV “a” determinant, which can be further extended to display other foreign epitopes. This paper is the first to report the application of MrNV VLPs as a novel platform to display foreign epitopes. 相似文献