全文获取类型
收费全文 | 618篇 |
免费 | 35篇 |
国内免费 | 2篇 |
出版年
2024年 | 1篇 |
2023年 | 10篇 |
2022年 | 23篇 |
2021年 | 46篇 |
2020年 | 20篇 |
2019年 | 21篇 |
2018年 | 36篇 |
2017年 | 36篇 |
2016年 | 34篇 |
2015年 | 40篇 |
2014年 | 52篇 |
2013年 | 45篇 |
2012年 | 53篇 |
2011年 | 76篇 |
2010年 | 21篇 |
2009年 | 17篇 |
2008年 | 24篇 |
2007年 | 12篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有655条查询结果,搜索用时 344 毫秒
81.
RNA interference (RNAi) is a homology-dependent gene silencing technology that involves double-stranded RNA directed against a target gene or its promoter region. Using hairpin constructs, double-stranded RNA can be expressed in plants relatively easily, enabling this technology to be applied to a wide range of species to silence the expression of both specific endogenous genes and genes of invading pathogens. RNAi has also been used to engineer metabolic pathways to overproduce secondary products with health, yield or environmental benefits. The application of tissue-specific or inducible gene silencing, with the use of appropriate promoters, and the ability to silence several genes simultaneously should enhance our ability to create novel traits in plants. 相似文献
82.
In this review, the evidence for a role of fibroblast growth factor receptor (FGFR) mediated signalling in carcinogenesis are considered and relevant underlying mechanisms highlighted. FGF signalling mediated by FGFR follows a classic receptor tyrosine kinase signalling pathway and its deregulation at various points of its cascade could result in malignancy. Here we review the accumulating reports that revealed the association of FGF/FGFRs to various types of cancer at a genetic level, along with in vitro and in vivo evidences available so far, which indicates the functional involvement of FGF signalling in tumour formation and progression. An increasing number of drugs against the FGF pathways is currently in clinical testing. We will discuss the strategies for future FGF research in cancer and translational approaches. 相似文献
83.
E Koudouna G Veronesi II Patel M Cotte C Knupp FL Martin AJ Quantock 《Biophysical journal》2012,103(2):357-364
The chemical composition and sulfur (S) speciation of developing chick corneas at embryonic days 12, 14, and 16 were investigated using synchrotron scanning x-ray fluorescence microscopy and x-ray absorption near-edge structure spectroscopy. The aim was to develop techniques for the analysis of bulk tissue and identify critical physicochemical variations that correlate with changes in corneal structure-function relationships. Derived data were subjected to principal component analysis and linear discriminant analysis, which highlighted differences in the elemental and S species composition at different stages of embryonic growth. Notably, distinct elemental compositions of chlorine, potassium, calcium, phosphorus, and S altered with development during the transition of the immature opaque cornea to a mature transparent tissue. S structure spectroscopy revealed developmentally regulated alterations in thiols, organic monosulfides, ester sulfate, and inorganic sulfate species. The transient molecular structures and compositional changes reported here provide a deeper understanding of the underlying basis of corneal development during the acquisition of transparency. The experimental and analytical approach is new, to our knowledge, and has wide potential applicability in the life sciences. 相似文献
84.
85.
86.
The Indian subcontinent is considered to be the likely centre of river buffalo domestication, based on population dynamics, archaeological evidence and genetic diversity. Recent studies on mitochondrial DNA diversity have drawn useful conclusions about the domestication history of Bubalus bubalis. The conclusions of these studies are, however, incomplete, unless samples can also be analysed from Pakistan, which contains the second largest buffalo population of the world. Here, we report the results of the first study on mitochondrial D-loop sequence diversity in five breeds of Pakistani buffalo. Analysis of sequence variations in 503-bp of the D-loop region of 123 animals revealed 52 haplotypes, including 40 singletons. Multidimensional display of breed pairwise F(ST) values revealed no strong clustering of breeds. Bayesian, maximum parsimony, neighbour joining and UPGMA trees revealed a topology consistent with domestication as well as subsequent introgression of multiple maternal lineages from the wild stocks. Reduced median network analysis provided evidence of population expansion from more than one set of haplotypes. The study also confirmed that Pakistani buffalo are of the river type. The observed mitochondrial D-loop sequence diversity suggests that Pakistani areas bordering India might have contributed to the initiation of domestication of the present-day river buffalo. 相似文献
87.
Umair Mahmood Muhammad Imran Salma Iqbal Naik Huma Arshad Cheema Anjum Saeed Muhammad Arshad Saqib Mahmood 《Gene》2012
Type I galactosemia is an inborn error resulting from mutations on both alleles of the GALT gene, which leads to the absence or deficiency of galactose-1-phosphate uridyltranseferase (GALT), the second of three enzymes catalyzing the conversion of galactose into glucose. On the basis of residual GALT activity, Type I galactosemia is classified into severe “Classical” and mild “Duarte” phenotypes. Classical galactosemia is frequently associated with S135L, Q188R and K285N mutations in the GALT gene. The functionally neutral N314D variation in the GALT gene is associated with Duarte galactosemia and is widespread among various worldwide populations. The present study aimed at detecting S135L, Q188R and K285N mutations and the N314D variant in the GALT gene by PCR using amplification refractory mutation system (ARMS). ARMS assays were established using standard DNA samples and were used for 8 galactosemia patients and 190 unrelated normal subjects all of Pakistani origin. S135L and K285N mutations were present neither in galactosemia patients nor in normal subjects. Only one galactosemia patient carried Q188R mutation that was in homozygous state. However, the N314D variant was frequently found both in affected (7 out of 16 alleles) and normal subjects (55 out of 380 alleles). This finding indicates that Duarte allele D314 might be far more common in Pakistani population than in European and North American ones. 相似文献
88.
M Shahid S Hameed A Imran S Ali JD van Elsas 《World journal of microbiology & biotechnology》2012,28(8):2749-2758
An Enterobacter sp. Fs-11 was isolated from sunflower rhizosphere, identified on the basis of 16S rRNA gene sequence analysis (GeneBank accession no. GQ179978) and studied for its root colonization and growth promotion ability in sunflower. Morphologically, it was rod shaped Gram-negative, motile bacterium, producing 4.5 μg mL(-1) indole acetic acid in tryptophan-supplemented medium. It utilized 27 out of 95 substrates in BIOLOG GN2 micro plate system. It was able to convert insoluble tri-calcium phosphate to soluble phosphorus up to 43.5 μg mL(-1) with decrease in pH of the medium up to 4.5 after 10 days incubation at 28 ± 2 °C in the Pikovskaya's broth. High performance liquid chromatography of cell free supernatant showed that Fs-11 produced malic acid and gluconic acid (2.43 and 16.64 μg mL(-1), respectively) in Pikovskaya's broth. Analysis of 900 bp fragment of pyrroloquinoline quinine pqqE gene sequence showed 98 % homology with that of E. cloacae pqqE gene. Confocal laser scanning microscope revealed strong colonization of fluorescently labeled Fs-11 with sunflower roots. Sunflower inoculation with Fs-11 and its rifampicin resistant derivative in sterile sand and natural soil showed that Fs-11 colonized sunflower roots up to 30 days after transplanting in both sterile sand as well as natural soil. Moreover, Fs-11 inoculation resulted in increased plant height, fresh weight, dry weight and total phosphorus contents as compared to un-inoculated plants. The data showed that Enterobacter sp. Fs-11 is an efficient phosphate solubilizing and plant growth promoting rhizobacterium and has great potential to be used as bio-inoculant for sunflower under phosphorus deficient conditions. 相似文献
89.
Priyanka Shah Sumit Kumar Sunita Tiwari Mohammad Imran Siddiqi 《Journal of chemical biology》2012,5(3):91-103
A series of 35 triazolopyrimidine analogues reported as Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) inhibitors were optimized using quantum mechanics methods, and their binding conformations were studied by docking
and 3D quantitative structure–activity relationship studies. Genetic algorithm-based criteria was adopted for selection of
training and test sets while maintaining structural diversity of training and test sets, which is also very crucial for model
development and validation. Both the comparative molecular field analyses (
q\textLOO2 = 0.841 q_{\text{LOO}}^2 = 0.{841} ,
r\textncv2 = 0.99 r_{\text{ncv}}^2 = 0.{99} ) and comparative molecular similarity indices analyses (
q\textLOO2 = 0.757 q_{\text{LOO}}^2 = 0.{757} ,
r\textncv2 = 0.943 r_{\text{ncv}}^2 = 0.{943} ) show excellent correlation and high predictive power. Furthermore, molecular dynamics simulations were performed to explore
the binding mode of the two of the most active compounds of the series, 10 and 14. Harmonization in the two simulation results validate the analysis and therefore applicability of docking parameters based
on crystallographic conformation of compound 14 bound to receptor molecule. This work provides useful information about the inhibition mechanism of this class of molecules
and will assist in the design of more potent inhibitors of PfDHODH. 相似文献
90.
Computer-aided 3-D reconstruction of fossils, or virtual paleontology, is an increasingly common and powerful technique. It is now regularly used for research in paleontology, yet to date has impacted little on public outreach and science communication; however, it is ideally suited for these purposes, being increasingly cheap and available, dynamic and exciting, and applicable to a range of topics. Here, we provide an introduction to the field, and a case study of its use for a public engagement event. The steps involved in creating such an educational resource are outlined, and include computed tomography scanning, digital visualization, and 3-D printing of fossils. We emphasize the value of virtual fossils for science communication; they allow for diverse learning styles in a variety of topics. In the future, we hope that virtual paleontology will become a mainstay of communicating the history of life, thereby promoting accurate understanding of evolution. 相似文献