全文获取类型
收费全文 | 1096篇 |
免费 | 89篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 43篇 |
2020年 | 27篇 |
2019年 | 27篇 |
2018年 | 33篇 |
2017年 | 39篇 |
2016年 | 49篇 |
2015年 | 54篇 |
2014年 | 63篇 |
2013年 | 103篇 |
2012年 | 79篇 |
2011年 | 83篇 |
2010年 | 49篇 |
2009年 | 33篇 |
2008年 | 54篇 |
2007年 | 34篇 |
2006年 | 47篇 |
2005年 | 49篇 |
2004年 | 36篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1995年 | 5篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1969年 | 6篇 |
1966年 | 4篇 |
排序方式: 共有1187条查询结果,搜索用时 406 毫秒
271.
272.
Marimuthu Jeya Kyoung-Mi Lee Manish Kumar Tiwari Jung-Soo Kim Paramasamy Gunasekaran Sang-Yong Kim In-Won Kim Jung-Kul Lee 《Applied microbiology and biotechnology》2009,83(2):225-231
This study isolated a novel erythritol-producing yeast strain, which is capable of growth at high osmolarity. Characteristics
of the strain include asexual reproduction by multilateral budding, absence of extracellular starch-like compounds, and a
negative Diazonium blue B color reaction. Phylogenetic analysis based on the 26S rDNA sequence and physiological analysis
indicated that the strain belongs to the species Pseudozyma tsukubaensis and has been named P. tsukubaensis KN75. When P. tsukubaensis KN75 was cultured aerobically in a fed-batch culture with glucose as a carbon source, it produced 245 g/L of erythritol,
corresponding to 2.86 g/L/h productivity and 61% yield, the highest erythritol yield ever reported by an erythritol-producing
microorganism. Erythritol production was scaled up from a laboratory scale (7 L fermenter) to pilot (300 L) and plant (50,000 L)
scales using the dissolved oxygen as a scale-up parameter. Erythritol production at the pilot and plant scales was similar
to that at the laboratory scale, indicating that the production of erythritol by P. tsukubaensis KN75 holds commercial potential. 相似文献
273.
Siddharth Tiwari Devesh K. Mishra Sribash Roy Ankit Singh P. K. Singh Rakesh Tuli 《Plant cell reports》2009,28(12):1827-1836
A synthetic DNA construct containing cholera toxin B subunit, genetically fused to the surface glycoprotein of rabies virus
was expressed in tobacco plants from a seed specific (legumin) promoter. Seed specific expression was monitored by real-time PCR, GM1-ELISA and Western blot analyses. The fusion protein
accumulated in tobacco seeds at up to 1.22% of the total seed protein. It was functionally active in binding to the GM1-ganglioside
receptors, suggesting its assembly into pentamers in seeds of the transgenic plants. Immunoblot analysis confirmed that the
~80.6 kDa monomeric fusion polypeptide was expressed in tobacco seeds and accumulated as a ~403 kDa pentamer. Evaluation of
its immunoprotective ability against rabies and cholera is to be examined. 相似文献
274.
P. Prabhakar Reddy Ashok K. Tiwari R. Ranga Rao K. Madhusudhana V. Rama Subba Rao Amtul Z. Ali K. Suresh Babu J. Madhusudana Rao 《Bioorganic & medicinal chemistry letters》2009,19(9):2562-2565
Phytochemical investigation of antihyperglycemic extract of rhizomes of Hedychium spicatum led to the isolation of two new labdane type diterpenes 2, 3 along with seven known compounds (1, 4–9). Their structures were established on the basis of NMR (1D and 2D) and mass spectroscopic analysis. The new compound 2 displayed strong intestinal α-glucosidase inhibitory activity. Other compounds also displayed varying degree of intestinal α-glucosidase inhibitory potential. 相似文献
275.
Vaibhav Tiwari Nissar A. Darmani Deepak Shukla 《Biochemical and biophysical research communications》2009,390(3):382-25415
Human herpesvirus-8 (HHV-8) is known to interact with cell surface heparan sulfate (HS) for entry into a target cell. Here we investigated the role of HS during HHV-8 glycoproteins-induced cell fusion. Interestingly, the observed fusion demonstrated an unusual dependence on HS as evident from following lines of evidence: (1) a significant reduction in cell-to-cell fusion occurred when target cells were treated with heparinase; (2) in a competition assay, when the effector cells expressing HHV-8 glycoproteins were challenged with soluble HS, cell-to-cell fusion was reduced; and, (3) co-expression of HHV-8 glycoproteins gH-gL on target cells resulted in inhibition of cell surface HS expression. Taken together, our results indicate that cell surface HS can play an additional role during HHV-8 pathogenesis. 相似文献
276.
Three-dimensional quantitative structure-activity relationship (3D-QSAR) using CoMFA and CoMSIA techniques was applied to evaluate 56 pyrimidine nucleosides as substrates of human thymidine kinase 1 (hTK1), 27 of them containing a carborane substituent either at the 3-, 5-, or 3'-position of the 2'-deoxyuridine scaffold. This is the first report describing 3D-QSAR studies of compounds containing boron atoms. Both CoMFA and CoMSIA models were derived from a training set of 47 molecules and the predictive capacity of the CoMSIA model was successfully validated by accurately calculating known phosphorylation rates of both boronated and non-boron hTK1 substrates that were not included in the training set. The optimal CoMSIA model provided the following values: q(2) 0.622, r(2) 0.983, s 0.165, and F 187.5. Contour maps obtained from the CoMSIA model were in agreement with the experimentally determined biological data. 相似文献
277.
Dipanwita Mitra Mohammad H. Hasan John T. Bates Michael A. Bierdeman Dallas R. Ederer Rinkuben C. Parmar Lauren A. Fassero Quntao Liang Hong Qiu Vaibhav Tiwari Fuming Zhang Robert J. Linhardt Joshua S. Sharp Lianchun Wang Ritesh Tandon 《PLoS pathogens》2021,17(8)
Several enveloped viruses, including herpesviruses attach to host cells by initially interacting with cell surface heparan sulfate (HS) proteoglycans followed by specific coreceptor engagement which culminates in virus-host membrane fusion and virus entry. Interfering with HS-herpesvirus interactions has long been known to result in significant reduction in virus infectivity indicating that HS play important roles in initiating virus entry. In this study, we provide a series of evidence to prove that specific sulfations as well as the degree of polymerization (dp) of HS govern human cytomegalovirus (CMV) binding and infection. First, purified CMV extracellular virions preferentially bind to sulfated longer chain HS on a glycoarray compared to a variety of unsulfated glycosaminoglycans including unsulfated shorter chain HS. Second, the fraction of glycosaminoglycans (GAG) displaying higher dp and sulfation has a larger impact on CMV titers compared to other fractions. Third, cell lines deficient in specific glucosaminyl sulfotransferases produce significantly reduced CMV titers compared to wild-type cells and virus entry is compromised in these mutant cells. Finally, purified glycoprotein B shows strong binding to heparin, and desulfated heparin analogs compete poorly with heparin for gB binding. Taken together, these results highlight the significance of HS chain length and sulfation patterns in CMV attachment and infectivity. 相似文献
278.
Vijay K. Tiwari Nidhi Rawat Kumari Neelam Sundip Kumar Gursharn S. Randhawa Harcharan S. Dhaliwal 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,121(2):259-269
Biofortification through genetic manipulation is the best approach for improving micronutrient content of the staple food crops to alleviate hidden hunger, namely, the deficiency of Fe and Zn affecting more than two billion people worldwide. An interspecific hybridization was made between T. aestivum line Chinese Spring (CS) and Aegilops kotschyi accession 3790 selected for high grain iron and zinc concentration. The CS × Ae. kotschyi F1 hybrid with low chromosome pairing was highly male and female sterile. This was backcrossed with wheat cultivars to get seed set. The selfed BC1F1 and BC2F1 plants with high grain iron and zinc concentration were selected in subsequent generations. The selected derivatives showed 60–136% enhanced grain iron and zinc concentration and 50–120% increased iron and zinc content per seed as compared to the recipient wheat cultivars. Thirteen cytologically stable, fertile and agronomically superior plants with high grain iron and zinc concentrations were selected for molecular characterization. The application of anchored wheat SSR markers, transferable to Ae. kotschyi, to the high grain iron and zinc containing derivatives indicated introgression of group 2 and group 7 chromosomes of Ae. kotschyi. GISH and FISH analysis of some derivatives confirmed the substitution of chromosomes 2S and 7U for their homoeologues of the A genome, suggesting that some of the genes controlling high grain micronutrient content in the Ae. kotschyi accession are on these chromosomes. 相似文献
279.
Subash Chandra Mohapatra Hemandra Kumar Tiwari Manisha Singla Brijesh Rathi Arun Sharma Kuldeep Mahiya Mukesh Kumar Saket Sinha Shyam Singh Chauhan 《Journal of biological inorganic chemistry》2010,15(3):373-385
A new class of copper(II) nanohybrid solids, LCu(CH3COO)2 and LCuCl2, have been synthesized and characterized by transmission electron microscopy, dynamic light scattering, and IR spectroscopy,
and have been found to be capped by a bis(benzimidazole) diamide ligand (L). The particle sizes of these nanohybrid solids
were found to be in the ranges 5–10 and 60–70 nm, respectively. These nanohybrid solids were evaluated for their in vitro
antimalarial activity against a chloroquine-sensitive isolate of Plasmodium falciparum (MRC 2). The interactions between these nanohybrid solids and plasmepsin II (an aspartic protease and a plausible novel target
for antimalarial drug development), which is believed to be essential for hemoglobin degradation by the parasite, have been
assayed by UV–vis spectroscopy and inhibition kinetics using Lineweaver–Burk plots. Our results suggest that these two compounds
have antimalarial activities, and the IC50 values (0.025–0.032 μg/ml) are similar to the IC50 value of the standard drug chloroquine used in the bioassay. Lineweaver–Burk plots for inhibition of plasmepsin II by LCu(CH3COO)2 and LCuCl2 show that the inhibition is competitive with respect to the substrate. The inhibition constants of LCu(CH3COO)2 and LCuCl2 were found to be 10 and 13 μM, respectively. The IC50 values for inhibition of plasmepsin II by LCu(CH3COO)2 and LCuCl2 were found to be 14 and 17 μM, respectively. Copper(II) metal capped by a benzimidazole group, which resembles the histidine
group of copper proteins (galactose oxidase, β-hydroxylase), could provide a suitable anchoring site on the nanosurface and
thus could be useful for inhibition of target enzymes via binding to the S1/S3 pocket of the enzyme hydrophobically. Both
copper(II) nanohybrid solids were found to be nontoxic against human hepatocellular carcinoma cells and were highly selective
for plasmepsin II versus human cathepsin D. The pivotal mechanism of antimalarial activity of these compounds via plasmepsin
II inhibition in the P. falciparum malaria parasite is demonstrated. 相似文献
280.
Jagesh K. Tiwari Anilabh D. Munshi Ravinder Kumar Raghu N. Pandey Ajay Arora Jayant S. Bhat Amish Kumar Sureja 《Acta Physiologiae Plantarum》2010,32(1):103-114
A pot experiment with 17 diverse genotypes of cucumber with four levels of salt stress viz., 0, 2, 4 and 6 dS m?1 was carried out during 2006. ANOVA revealed significant differences amongst genotypes and genotype × salt stress interaction indicating the genetic variability and differential response of the genotypes to different salt stress levels. The salt stress adversely affected the biochemical parameters; effects were severe under 4 dS m?1. No genotype could survive at 6 dS m?1. Sodium content, Na+–K+ ratio, proline, reducing sugars, phenol and yield reduction (%) increased significantly as the salt stress increased. Potassium, chlorophyll, membrane stability index and fruit yield decreased significantly under salt stress in all genotypes. However, the genotypes CRC-8, CHC-2 and G-338 showed lower accumulation of sodium, lesser depletion of potassium, lower Na+–K+ ratio and higher accumulation of proline, reducing sugars, phenols, better membrane stability and lower yield reduction (%) under salt stress, while CH-20 and DC-1 were sensitive to salt stress. Thus, a combination of traits such as higher membrane stability, lower Na+–K+ ratio, higher osmotic concentration and selective uptake of useful ions and prevention of over accumulation of toxic ions contribute to salt stress tolerance in cucumber. These traits would be useful selection criteria during salt stress breeding in cucumber. 相似文献