全文获取类型
收费全文 | 603篇 |
免费 | 22篇 |
国内免费 | 4篇 |
专业分类
629篇 |
出版年
2023年 | 8篇 |
2022年 | 23篇 |
2021年 | 38篇 |
2020年 | 16篇 |
2019年 | 30篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 18篇 |
2015年 | 38篇 |
2014年 | 38篇 |
2013年 | 51篇 |
2012年 | 35篇 |
2011年 | 41篇 |
2010年 | 17篇 |
2009年 | 26篇 |
2008年 | 33篇 |
2007年 | 27篇 |
2006年 | 21篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 13篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有629条查询结果,搜索用时 15 毫秒
21.
22.
Razia Sultana Rizwan Arif Manish Rana Saiema Ahmedi Rabiya Mehandi Akrema Nikhat Manzoor Rahisuddin 《Luminescence》2022,37(3):408-421
An oxadiazole derivative 2 was prepared by condensation reaction through cyclization of semicarbazone in the presence of bromine; the structural confirmation was supported by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, Fourier transform-infrared spectroscopy, and liquid chromatography-mass spectrometry. Its sensing ability towards Ni2+ ion was examined showing a binding constant of 1.04 × 105 compared with other suitable metal cations (Ca2+, Co2+, Cr3+, Ag+, Pb2+, Fe3+, Mg2+, and K+) using ultraviolet–visible (UV–vis) and fluorescence spectroscopic studies. The minimum concentration of Ni2+ ions and limit of detection was found to be 9.4 μM. A job's plot gave the binding stoichiometry ratio of oxadiazole derivative 2 vs Ni2+ ions as 2:1. Furthermore, the intercalative binding mode of oxadiazole derivative 2 with calf thymus DNA was supported by ultraviolet–visible (UV–vis) and fluorescent light, viscosity, cyclic voltammetry, time-resolved fluorescence, and circular dichroism measurements. The molecular docking result gave the binding score for oxadiazole derivative 2 as −6.5 kcal/mol, which further confirmed the intercalative interaction. In addition, the antifungal activity of oxadiazole derivative 2 was also screened against several fungal strains (C. albicans, C. glabrata, and C. tropicalis) by broth dilution and disc diffusion methods. In antioxidant studies, the oxadiazole derivative 2 showed potential scavenging activity against 2,2-diphenyl-1-picrylhydrazyl and H2O2 free radicals. 相似文献
23.
24.
Arup Kr. Malakar Debashree Choudhury Binata Halder Prosenjit Paul Arif Uddin Supriyo Chakraborty 《Journal of cellular physiology》2019,234(10):16812-16823
Coronary artery disease (CAD) is one of the major cardiovascular diseases affecting the global human population. This disease has been proved to be the major cause of death in both the developed and developing countries. Lifestyle, environmental factors, and genetic factors pose as risk factors for the development of cardiovascular disease. The prevalence of risk factors among healthy individuals elucidates the probable occurrence of CAD in near future. Genome-wide association studies have suggested the association of chromosome 9p21.3 in the premature onset of CAD. The risk factors of CAD include diabetes mellitus, hypertension, smoking, hyperlipidemia, obesity, homocystinuria, and psychosocial stress. The eradication and management of CAD has been established through extensive studies and trials. Antiplatelet agents, nitrates, β-blockers, calcium antagonists, and ranolazine are some of the few therapeutic agents used for the relief of symptomatic angina associated with CAD. 相似文献
25.
The BRCA1 gene is located on the human chromosome 17q21.31 and plays important role in biological processes. The aminoacyl-tRNA synthetases (AARS) are a family of heterogenous enzymes responsible protein synthesis and whose secondary functions include a role in autoimmune myositis. Our findings reveal that the compositional constraint and the preference of more A/T –ending codons determine the codon usage patterns in BRCA1 gene while more G/C-ending codons influence the codon usage pattern of AARS gene among mammals. The codon usage bias in BRCA1 and AARS genes is low. The codon CGC encoding arginine amino acid and the codon TTA encoding leucine were uniformly distributed in BRCA1 and AARS genes, respectively in mammals including human. Natural selection might have played a major role while mutation pressure might have played a minor role in shaping the codon usage pattern of BRCA1 and AARS genes. 相似文献
26.
Arif Muhammad Rashid Naeem Perveen Sumera Bashir Qamar Akhtar Muhammad 《Extremophiles : life under extreme conditions》2019,23(1):69-77
Extremophiles - The gene-encoding Indole-3-glycerol phosphate synthase, a key enzyme involved in the cyclization of 1-(o-carboxyphenylamino)-1-deoxyribulose 5-phosphate, from Pyrococcus furiosus... 相似文献
27.
28.
Tropical soils degraded by slash‐and‐burn cultivation can be recultivated when amended with ashes and compost 下载免费PDF全文
Justine Marie Gay‐des‐Combes Clara Sanz Carrillo Bjorn Jozef Maria Robroek Vincent Eric Jules Jassey Robert Thomas Edmund Mills Muhammad Saleem Arif Leia Falquet Emmanuel Frossard Alexandre Buttler 《Ecology and evolution》2017,7(14):5378-5388
In many tropical regions, slash‐and‐burn agriculture is considered as a driver of deforestation; the forest is converted into agricultural land by cutting and burning the trees. However, the fields are abandoned after few years because of yield decrease and weed invasion. Consequently, new surfaces are regularly cleared from the primary forest. We propose a reclamation strategy for abandoned fields allowing and sustaining re‐cultivation. In the dry region of south‐western Madagascar, we tested, according to a split‐plot design, an alternative selective slash‐and‐burn cultivation technique coupled with compost amendment on 30–year‐old abandoned fields. Corn plants (Zea mays L.) were grown on four different types of soil amendments: no amendment (control), compost, ashes (as in traditional slash‐and‐burn cultivation), and compost + ashes additions. Furthermore, two tree cover treatments were applied: 0% tree cover (as in traditional slash‐and‐burn cultivation) and 50% tree cover (selective slash‐and‐burn). Both corn growth and soil fertility parameters were monitored during the growing season 2015 up to final harvest. The amendment compost + ashes strongly increased corn yield, which was multiplied by 4–5 in comparison with ashes or compost alone, reaching 1.5 t/ha compared to 0.25 and 0.35 t/ha for ashes and compost, respectively. On control plots, yield was negligible as expected on these degraded soils. Structural equation modeling evidenced that compost and ashes were complementary fertilizing pathways promoting soil fertility through positive effects on soil moisture, pH, organic matter, and microbial activity. Concerning the tree cover treatment, yield was reduced on shaded plots (50% tree cover) compared to sunny plots (0% tree cover) for all soil amendments, except ashes. To conclude, our results provide empirical evidence on the potential of recultivating tropical degraded soils with compost and ashes. This would help mitigating deforestation of the primary forest by increasing lifespan of agricultural lands. 相似文献
29.
Ashokraj Shanmugam Arif Hasan Khan Robin Senthil Kumar Thamilarasan Harshavardhanan Vijayakumar Sathishkumar Natarajan Hoy-Taek Kim Jong-In Park Ill-Sup Nou 《Journal of Plant Biology》2017,60(5):472-484
The Minichromosome maintenance protein [MCM (2-7)] complex is associated with helicase activity for replication fork formation during DNA replication. We identified and characterized each 12 putative MCM genes from Brassica oleracea and Brassica rapa. MCM genes were classified into nine groups according to their evolutionary relationships. A high number of syntenic regions were present on chromosomes C03 and A03 in B. oleracea and B. rapa, respectively, compared to the other chromosomes. Expression analysis showed that most of the MCM(2-7) helicase-subunit genes and their coregulating MCM genes were upregulated during hydroxyurea (HU) induced stress in B. oleracea. In B. rapa, MCM(2-7) helicase genes BrMCM2_2, BrMCM7_1, BrMCM7_2 and their co-regulating genes were upregulated during replication stress. During cold stress, BoMCM6 in B. oleracea and BrMCM5 in B. rapa were remarkably upregulated. During salt stress, BoMCM6_2, BoMCM7_1, BoMCM8, BoMCM9, and BoMCM10 were markedly upregulated in B. oleracea. Hence, our study identified the candidate MCM family genes those possess abiotic stress-responsive behavior and DNA replication stress tolerance. As the first genome-wide analysis of MCM genes in B. oleracea and B. rapa, this work provides a foundation to develop stress responsive plants. Further functional and molecular studies on MCM genes will be helpful to enhance stress tolerance in plants. 相似文献
30.
Mohammad Badrul Anam Shah Adil Ishtiyaq Ahmad Mikiko Kudo Arif Istiaq Athary Abdulhaleem M. Felemban Naofumi Ito Kunimasa Ohta 《Development, growth & differentiation》2020,62(2):97-107
Specialized microenvironment, or neurogenic niche, in embryonic and postnatal mouse brain plays critical roles during neurogenesis throughout adulthood. The subventricular zone (SVZ) and the dentate gyrus (DG) of hippocampus in the mouse brain are two major neurogenic niches where neurogenesis is directed by numerous regulatory factors. Now, we report Akhirin (AKH), a stem cell maintenance factor in mouse spinal cord, plays a pivotal regulatory role in the SVZ and in the DG. AKH showed specific distribution during development in embryonic and postnatal neurogenic niches. Loss of AKH led to abnormal development of the ventricular zone and the DG along with reduction of cellular proliferation in both regions. In AKH knockout mice (AKH−/−), quiescent neural stem cells (NSCs) increased, while proliferative NSCs or neural progenitor cells decreased at both neurogenic niches. In vitro NSC culture assay showed increased number of neurospheres and reduced neurogenesis in AKH−/−. These results indicate that AKH, at the neurogenic niche, exerts dynamic regulatory role on NSC self-renewal, proliferation and differentiation during SVZ and hippocampal neurogenesis. 相似文献