首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1698篇
  免费   79篇
  国内免费   1篇
  2024年   3篇
  2023年   18篇
  2022年   45篇
  2021年   89篇
  2020年   51篇
  2019年   68篇
  2018年   70篇
  2017年   80篇
  2016年   113篇
  2015年   132篇
  2014年   133篇
  2013年   188篇
  2012年   170篇
  2011年   152篇
  2010年   87篇
  2009年   55篇
  2008年   43篇
  2007年   42篇
  2006年   35篇
  2005年   39篇
  2004年   24篇
  2003年   15篇
  2002年   18篇
  2001年   5篇
  2000年   8篇
  1999年   11篇
  1998年   2篇
  1997年   2篇
  1996年   7篇
  1995年   2篇
  1994年   5篇
  1993年   4篇
  1992年   7篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   5篇
  1985年   5篇
  1984年   6篇
  1983年   3篇
  1982年   5篇
  1981年   3篇
  1980年   1篇
  1979年   2篇
  1978年   3篇
  1977年   1篇
  1974年   4篇
  1973年   5篇
  1972年   1篇
  1971年   1篇
排序方式: 共有1778条查询结果,搜索用时 15 毫秒
81.
Reproductive hormones play a significant role in the gonadal development and gametogenesis process of animals. In the present study luteinizing hormone beta, (lhb) subunit gene was cloned and characterized from the brain of Catla catla. The lhb full-length of cDNA sequence is 629 bp which consists of 43bp 5'-UTR (untranslated region) 447bp, ORF(open reading frame) and 139 bp of 3'-UTR respectively. The coding region of lhb gene encoded a peptide of 148 amino acids. The coding sequence of lhb gene consist of a single N-linked glycosylation site (NET) and 12 cysteine knot residues. Phylogenetic analysis of C. catla Lhβ deduced amino acid sequence showed high similarity with Carassius auratus followed by Gobiocypris rarus. 3D structure Lhβ protein comprises of five β-sheets and six coils/loops. The qPCR results revealed lhb mRNA is mainly expressed in the pituitary, ovary while moderate expression was observed in brain and testis. To best our knowledge, this is the first report on the identification, molecular characterization and structural information regarding luteinizing hormone in Indian major carp.  相似文献   
82.
Copper oxide nanomaterials were synthesized by a facile sustainable biological method using two plant species (Zanthoxylum armatum DC. and Berberis lycium Royle ). The formation of materials was confirmed by FT‐IR, ATR, UV‐visible, XRD, TEM, SEM, EDX, TGA and PL. The antibacterial activity was evaluated by agar well diffusion method to ascertain the efficacy of plant species extract and extract derived copper oxide nanomaterials against six Gram‐positive bacteria namely Staphylococcus aureus, Streptococcus mutans, Streptococcus pyogenes, Corynebacterium diphtheriae, Corynebacterium xerosis, Bacillus cereus and four Gram‐negative bacteria such as Klebsiella pneumonia, Escherichia coli, Pseudomonas aeruginosa and Proteus vulgaris against the standard drug, Ciprofloxacin for Gram‐positive and Gentamicin for Gram‐negative bacteria, respectively. In both cases, copper oxide nanomaterials were found to be sensitive in all the bacterial species. Sensitivity of copper oxide nanomaterials shows an be higher as compared to plant species extract against different bacteria. Scavenging activity of plant extracts along with nanomaterials have been accessed using previously reported protocols employing ascorbic acid as standard. Scavenging activity of copper oxide nanomaterials shows an increase with increase in concentration. The biological activity (bactericidal and scavenging efficiency) of plant derived copper oxide nanomaterials revealed that these materials can be used as potent antimicrobial agent and DPPH scavengers in industrial as well as pharmacological fields.  相似文献   
83.
Journal of Physiology and Biochemistry - Gamma-tocotrienol (GTT) and hydroxychavicol (HC) exhibit anticancer activity in glioma cancer cells, where the combination of GTT + HC was shown to be more...  相似文献   
84.
The International Journal of Life Cycle Assessment - Palm oil is considered as the primary source of income for many farmers in Southeast Asia and become a very important agricultural commodity for...  相似文献   
85.
86.
Solar radiation regulates most biological activities on Earth. Prolonged exposure to solar UV radiation can cause deleterious effects by inducing two major types of DNA damage, namely, cyclobutane pyrimidine dimers (CPDs) and pyrimidine 6-4 pyrimidone photoproducts. These lesions may be repaired by the photoreactivation (Phr) and nucleotide excision repair (NER) pathways; however, the principal UV-induced DNA repair pathway is not known in the fungal genus Pseudogymnoascus. In this study, we demonstrated that an unweighted UV-B dosage of 1.6 kJ m−2 d−1 significantly reduced fungal growth rates (by between 22% and 35%) and inhibited conidia production in a 10 d exposure. The comparison of two DNA repair conditions, light or dark, which respectively induced photoreactivation (Phr) and NER, showed that the UV-B-induced CPDs were repaired significantly more rapidly in light than in dark conditions. The expression levels of two DNA repair genes, RAD2 and PHR1 (encoding a protein in NER and Phr respectively), demonstrated that NER rather than Phr was primarily activated for repairing UV-B-induced DNA damage in these Pseudogymnoascus strains. In contrast, Phr was inhibited after exposure to UV-B radiation, suggesting that PHR1 may have other functional roles. We present the first study to examine the capability of the Arctic and Antarctic Pseudogymnoascus sp. to perform photoreactivation and/or NER via RT-qPCR approaches, and also clarify the effects of light on UV-B-induced DNA damage repair in vivo by quantifying cyclobutene pyrimidine dimers and pyrimidine 6-4 pyrimidone photoproducts. Physiological response data, including relative growth rate, pigmentation and conidia production in these Pseudogymnoascus isolates exposed to UV-B radiation are also presented.  相似文献   
87.

The complex climatic and geological history of Southeast Asia has been hypothesised to determine the most important aspects of the current phylogeographical structure and distribution of living organisms throughout the region. To test existing hypotheses, the genetic structure of the tire track eel, Mastacembelus favus, was investigated using 823 bp of mitochondrial DNA cytochrome b from 469 individuals from 51 localities encompassing its native range. The results classified all haplotypes into two major lineages, Lineage 1, which was further divided into Lineages 1a (lower Mekong, eastern Gulf of Thailand and Malay—Thai Peninsula), 1b (Banpakong River), 1c (Chao Phraya, Gulf of Thailand and Malay—Thai Peninsula) and 1d (Khlang Yai River), and Lineage 2, the upper reaches of the lower Mekong and the middle Mekong. Strong genetic discontinuities dated approximately 5 MYA were discovered in the Mekong with limited geographical overlap, suggesting a historically dissected drainage between two sections and species colonisation via different routes. The widespread Lineage 1 showed a strong signature of population expansion during the Pleistocene climate oscillation. Haplotype characteristics in the Malay—Thai Peninsula are hypothesised to result from postglacial dispersal from the Mekong and Chao Phraya through an extended Pleistocene drainage network.

  相似文献   
88.
89.
Carbendazim is a benzimidazole fungicide used to control the fungal invasion. However, its exposure might lead to potential health problems. The present study evaluates the interaction of carbendazim (CAR) with human serum albumin (HSA) which is an important drug carrier protein and plays a very crucial role in the transportation of small molecules. A number of biophysical techniques were employed to investigate the binding of CAR with HSA. The increased UV-absorption of HSA on titrating with CAR suggests the formation of HSA–CAR complex and it could be due to the exposure of aromatic residues. The fluorescence study confirmed that CAR quenches the fluorescence of HSA and showed the static mode of quenching. CAR (50 µM) quenches around 56.14% of the HSA fluorescence. The quenching constant, binding constant, number of binding site and free energy change was calculated by fluorescence quenching experiment. Competitive displacement assay showed Sudlow’s site I as the primary binding site of CAR on HSA. The synchronous fluorescence study revealed the perturbation in the microenvironment around tyrosine and tryptophan residues upon binding of CAR to HSA. The circular dichroism results suggested that the binding of CAR to HSA altered its secondary structure. Molecular docking experiment demonstrated the binding of CAR to Sudlow’s site I of HSA. Docking studies suggested that the hydrogen bonding, van der Waals and pi-alkyl are playing role in the interaction of CAR with HSA. The study confirmed the conformational changes within HSA upon binding of CAR.  相似文献   
90.
Due to the critical role of cellular enzymes necessary for cell proliferation by deciphering topological hurdles in the process of DNA replication, topoisomerases have been one of the major targets in the anticancer drug development area. A need, therefore, arises for new metallodrugs that specifically recognizes DNA and inhibits the activity of topoisomerase enzymes, herein, we report the synthesis and characterization of new metal-based glycoconjugate entities containing heterobimetallic core CuII–SnIV (1) and NiII–SnIV (2) derived from N-glycoside ligand (L). The optimized structure of complex 1 and other significant vibrational modes have been explained using dispersion corrected B3LYP/DFT calculations. In vitro DNA binding profile of the L and both the complexes 1 and 2 were done by various biophysical studies. Complex 1 breaks pBR322 DNA via a hydrolytic means which was validated by T4 DNA enzymatic assay. To get a mechanistic insight of mode of action topoisomerase I (Topo I) inhibition assay was carried out. Also, we have taken the help of molecular modeling studies in accordance with experimental findings. In vitro cytotoxicity of the complex 1 was evaluated against a panel of cancer cells which exhibited remarkably good anticancer activity (GI50 values <10 μg/ml). Moreover, intracellular localization of the complex 1 was visualized by confocal microscopy against HeLa cells.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号