全文获取类型
收费全文 | 6748篇 |
免费 | 352篇 |
国内免费 | 507篇 |
出版年
2024年 | 22篇 |
2023年 | 123篇 |
2022年 | 190篇 |
2021年 | 242篇 |
2020年 | 191篇 |
2019年 | 245篇 |
2018年 | 192篇 |
2017年 | 168篇 |
2016年 | 153篇 |
2015年 | 217篇 |
2014年 | 312篇 |
2013年 | 422篇 |
2012年 | 234篇 |
2011年 | 252篇 |
2010年 | 211篇 |
2009年 | 301篇 |
2008年 | 337篇 |
2007年 | 299篇 |
2006年 | 333篇 |
2005年 | 291篇 |
2004年 | 284篇 |
2003年 | 239篇 |
2002年 | 207篇 |
2001年 | 195篇 |
2000年 | 171篇 |
1999年 | 165篇 |
1998年 | 152篇 |
1997年 | 127篇 |
1996年 | 140篇 |
1995年 | 129篇 |
1994年 | 153篇 |
1993年 | 125篇 |
1992年 | 113篇 |
1991年 | 102篇 |
1990年 | 97篇 |
1989年 | 80篇 |
1988年 | 76篇 |
1987年 | 79篇 |
1986年 | 55篇 |
1985年 | 46篇 |
1984年 | 43篇 |
1983年 | 12篇 |
1982年 | 24篇 |
1981年 | 19篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有7607条查询结果,搜索用时 140 毫秒
991.
992.
N. D. Jambhale Y. S. Nerkar 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,71(1):122-125
Summary Genetic studies on radiation-induced chlorina and variegated mutants of okra (Abelmoschus esculentus (L.) Moench) revealed the existence of an unstable gene. The normal green color of the leaves is controlled by duplicate genes C1 and C2, either of which produces the green colour. The chlorina plants are C
1
C
1
C
2
C
2. The allele c
1
v
is dominant to both C
1 and C
2 but is unstable. The homozygote c
1
v
c
1
v
c
2
c
2 is a normal green while the heterozygote c
i
v
c
1
c
2
c
2 has a variegated phenotype as a result of the mutation of c
1
v
to c
1 during development. In green plants with a c
1
v
c{sh1/v}c
2
c
2 genotype, the autonomous mutation of one of the c
1
v
alleles to c
1 may take place at the pre-meiotic stage. In the variegated genotype (c
1
v
c
1
c
2
c
2), the mutation of c
1 to c
1
v
may take place in early ontogeny, thus producing green plants. The allele C
1, when associated with c
1
v
in a heterozygous condition, mutates to c
1 at the pre-meiotic stage even in the presence of the allele C
2. 相似文献
993.
Sexual colouration and sperm traits in guppies 总被引:4,自引:0,他引:4
The relationships among the area, hue, saturation and brightness of orange colouration and sperm traits in the guppy Poecilia reticulata were investigated. Males with greater areas of orange colouration had significantly larger sperm loads, more motile sperm and longer sperm relative to males with relatively little orange colouration. Males with greater areas of orange colouration did not possess more viable sperm than males with relatively little orange colouration. There was no evidence that any of the sperm traits were related to the hue, saturation or brightness of the orange colouration. These results are discussed in the context of the roles that direct and indirect selection might play in maintaining female preference for male guppies with large areas of orange colouration. 相似文献
994.
995.
996.
《Saudi Journal of Biological Sciences》2021,28(11):6289-6296
According Global Cancer Statistics 2020 GLOBOCAN estimates female breast cancer was found as the most commonly diagnosed cancer, with an estimated 2.3 million new cases (11.7%), and the fourth leading cause (6.9%) of cancer death among women worldwide. Identification of new diagnostic marker sharply characterize the tumor feature is intensive need. The present work was performed to investigate the involvement of the INF-γ + 874 T/A gene polymorphism in different breast cancer prognostic factors. Polymorphism detection analysis was performed on 163 subjects from breast cancer patients, 79 with inflamed cells of breast patients and 144 controls. The gene polymorphism was detected using the amplification refractory mutation system- polymerase chain reaction method (ARMS-PCR). The distribution of INF-γ T + 874A gene polymorphism shows strong significant association between INF-γ + 874 T/A genotypes TT in BC patients (ORTT: 6.41 [95% CI = 2.72–15.1] P < 0.0001) as well as strong significant association regarding T allele (ORT: 1.99 [95% CI = 1.43–2.76] P < 0.0001) when compared to the healthy control. In ICB group the strong association was noted with INF-γ + 874 T/A genotypes AT genotype (ORAT: 2.28 [95% CI = 1.22–4.29] P = 0.007). From the different histological BC hormonal markers the human epidermal growth factor receptor 2 (HER2) was showing significant association in INF-γ + 874 T/A genotypes TT (P = 0.03) and recessive model (TT versus AA + AT P = 0.03). Concerning different BC prognostic models, the poor prognostic one of luminal B, (ER+ve PR+ve Her2+ve) show significant association in the host INF-γ + 874 T/A genotype (TT, P = 0.03) and recessive model (TT versus AA + AT P = 0.02) when compared to the good prognostic hormonal status luminal A model, (ER+ve PR+ve Her2-ve). It seems that this is the first study that interested in correlate the INF-γ + 874 T/A gene polymorphisms in Egyptian BC patients. T allele, TT genotype and recessive model of the INF-γ + 874 T/A gene variants were documented as risk factors for BC pathogenesis. It may be used as practical biomarker to guide the BC carcinogenesis and risk process. 相似文献
997.
Sudip Kundu Dhananjay Bhattacharya Ashoke Ranjan Thakur Rabi Majumdar 《Journal of biomolecular structure & dynamics》2013,31(4):527-533
Abstract Based on worm like chain model, DNA structural parameters—tilt, roll and rise, derived from crystallographic database have been used to determine the flexibility of DNA that regulates the nucleosomal translational positioning. Theoretically derived data has been compared to the experimental values available in Ioshikhes and Trifonov's database. The methodology has been extended to determine the flexibility of 18S rRNA genome in eukarya, where yeast shows a distinct difference when compared with mammals like human, mouse and rabbit. 相似文献
998.
999.
1000.
Orthologs are genes from different genomes that originate from a common ancestor gene by speciation event. They are most similar by the structure of encoded proteins and therefore should have a similar function. Here I apply the principle used for detection of structural orthology for a genome-wide analysis of gene expression. For this purpose, I determine the mutual similarity rank in all-by-all comparison of among-tissues expression patterns. The expression of most part of human–mouse orthologs in homologous tissues is poorly correlated (average mutual coexpression rank is only 4835 out of 18,092). Genes from evolutionarily labile gene families, which experience rapid turnover of family composition, are among those with the strongest expression change. However, the revealed phenomenon is not limited to them. There is no or very weak relationship between protein sequence divergence and mutual coexpression rank. Also, generally there is no relationship between the ratio of nonsynonymous to synonymous nucleotide substitutions and coexpression rank. This relationship is tangible only within evolutionarily labile gene families. These results indicate that despite of a similar biochemical function of orthologs reflected in the conserved protein sequence, the physiological (systemic) context of this function can be changed. Also, these results suggest that gene biochemical function and its physiological role in the organism can evolve independently. 相似文献