全文获取类型
收费全文 | 435篇 |
免费 | 29篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 37篇 |
2020年 | 6篇 |
2019年 | 14篇 |
2018年 | 24篇 |
2017年 | 18篇 |
2016年 | 18篇 |
2015年 | 22篇 |
2014年 | 33篇 |
2013年 | 28篇 |
2012年 | 36篇 |
2011年 | 22篇 |
2010年 | 13篇 |
2009年 | 11篇 |
2008年 | 16篇 |
2007年 | 14篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有464条查询结果,搜索用时 296 毫秒
51.
Kuvalekar Aniket Pawar Pankaj Khare Ankita Gandhe Kanchanganga Harsulkar Abhay 《Plant Cell, Tissue and Organ Culture》2008,94(1):101-104
Ravenelia esculenta Naras. and Thirum. is a rust, pathogenic to Acacia eburnea Willd. The infection leads to hypertrophy changing the morphology with bizarre shapes of plant organs. Healthy and infected
tissues were subjected to extraction of IAA and indole derivatives and were estimated by spectrophotometric methods. The hypertrophy
produced was presumed to be due to increase in the indole-3-acetic acid (IAA) content in the infected tissue, however, the
amount of IAA in infected tissues decreased with the progression of disease. Concomitantly, the infected tissue showed the
presence of a novel, slow migrating, indole derivative on TLC. Cultured shoot tips of Withania somnifera were dosed with the methanolic extract of the infected hypertrophied tissue (MEHT) (0.25, 0.5, 0.75, 1.00 and 1.25 mg/l).
The stimulation in shoot growth along with profuse rooting was observed in a dose dependent manner with maximum at 1.00 and
1.25 mg/l concentration. 相似文献
52.
Putative virulence characteristics of <Emphasis Type="Italic">Stenotrophomonas maltophilia</Emphasis>: a study on clinical isolates 总被引:1,自引:1,他引:0
Sanjay Chhibber Ankita Gupta Riti Sharan Vikas Gautam Pallab Ray 《World journal of microbiology & biotechnology》2008,24(12):2819-2825
Stenotrophomonas maltophilia is an important evolving pathogen, especially in patients with cystic fibrosis (CF), but its mechanism of pathogenesis is
poorly understood. The purpose of this study was to investigate the presence of potential virulence determinants in five septicemic
clinical isolates of S. maltophilia. When screened for EPS biosynthesis, all five strains produced colonies on two different growth media both at 30 and 37 °C.
LPS could be extracted from all strains successfully and all were positive for both cell-free and cell-bound hemolysin production
but failed to agglutinate 3% human RBCs. Variation in the ability to produce protease and phospholipase C was observed. In
addition, all strains were unable to produce pyochelin but were able to produce ornibactin in the form of hydroxamate derivatives.
It was also observed that all strains showed adherence to mouse tracheal epithelium. 相似文献
53.
The mechanisms that mediate biomembrane shape transformations are of considerable interest in cell biology. Recent in vitro experiments show that the chemical transformation of minor membrane lipids can induce dramatic shape changes in biomembranes. Specifically, it was observed that the addition of DOPA to DOPE has no effect on the stability of the bilayer structure of the membrane. In contrast, the addition of LPA to DOPE stabilizes the bilayer phase of DOPE, increasing the temperature of a phase transition from the bilayer to the inverted hexagonal phase. This result suggests that the chemical conversion of DOPA to LPA is sufficient for triggering a dramatic change in the shape of biomembranes. The LPA/DOPA/DOPE mixture of lipids provides a simple model system for understanding the molecular events driving the shape change. In this work, we used coarse-grained molecular dynamics simulations to study the phase transitions of this lipid mixture. We show that despite the simplicity of the coarse-grained model, it reproduces the experimentally observed phase changes of: 1), pure LPA and DOPA with respect to changes in the concentration of cations; and 2), LPA/DOPE and DOPA/DOPE mixtures with respect to temperature. The good agreement between the model and experiments suggests that the computationally inexpensive coarse-grained approach can be used to infer macroscopic membrane properties. Furthermore, analysis of the shape of the lipid molecules demonstrates that the phase behavior of single-lipid systems is consistent with molecular packing theory. However, the phase stability of mixed lipid systems exhibits significant deviations from this theory, which suggests that the elastic energy of the lipids, neglected in the packing theory, plays an important role. 相似文献
54.
The isocitrate dehydrogenase-2 (Idh-2) locus of Anopheles quadrimaculatus was analyzed genetically and the enzyme was characterized physiochemically. Three-point testcrosses involving chromosome 3 markers showed that in female hybrids the gene sequence and the map distances are: nonstripe (st)--6.8--Idh-2--43.5--short antenna (Sa). Reduced recombination frequencies were observed in male hybrids (st--3.4--Idh-2--25.5--Sa). Idh-2 activity gradually increases during development and reaches a peak intensity in adults. Maximum enzyme activity of Idh-2 was obtained at pH 7.5. One-minute heat treatment at 50 degrees C caused about 50 percent reduction of IDH-2. Ethylene diamine tetraacetic acid (EDTA 5 mM) and p-chloromercuribenzoate (pCMB 10(-5)M) caused complete loss of activity of IDH-2, but pretreatment of the enzyme in situ with mercaptoethanol protected the activity of allozymes from inhibition by pCMB treatment. 相似文献
55.
William J. Trickler Jatin Khurana Ankita A. Nagvekar Alekha K. Dash 《AAPS PharmSciTech》2010,11(1):392-401
The objectives of this study are to enhance cellular accumulation of gemcitabine with chitosan/glyceryl monooleate (GMO) nanostructures,
and to provide significant increase in cell death of human pancreatic cancer cells in vitro. The delivery system was prepared by a multiple emulsion solvent evaporation method. The nanostructure topography, size,
and surface charge were determined by atomic force microscopy (AFM), and a zetameter. The cellular accumulation, cellular
internalization and cytotoxicity of the nanostructures were evaluated by HPLC, confocal microscopy, or MTT assay in Mia PaCa-2
and BxPC-3 cells. The average particle diameter for 2% and 4% (w/w) drug loaded delivery system were 382.3 ± 28.6 nm, and 385.2 ± 16.1 nm, respectively with a surface charge of +21.94 ± 4.37
and +21.23 ± 1.46 mV. The MTT cytotoxicity dose-response studies revealed the placebo at/or below 1 mg/ml has no effect on
MIA PaCa-2 or BxPC-3 cells. The delivery system demonstrated a significant decrease in the IC50 (3 to 4 log unit shift) in
cell survival for gemcitabine nanostructures at 72 and 96 h post-treatment when compared with a solution of gemcitabine alone.
The nanostructure reported here can be resuspended in an aqueous medium that demonstrate increased effective treatment compared
with gemcitabine treatment alone in an in vitro model of human pancreatic cancer. The drug delivery system demonstrates capability to entrap both hydrophilic and hydrophobic
compounds to potentially provide an effective treatment option in human pancreatic cancer. 相似文献
56.
57.
58.
Piperonyl butoxide has been found to act as potent inhibitor for potato spindle tuber viroid in Scopolia sinensis Hemsl plant. 相似文献
59.
N N Anand G Dubuc S Mandal J Phipps M A Gidney B Sinnott N M Young C R MacKenzie D R Bundle S A Narang 《Protein engineering》1990,3(6):541-546
A 658 bp DNA sequence corresponding to the murine lambda 1 chain of a monoclonal antibody, Se155-4, specific for the Salmonella serotype B O-antigen, was designed using Escherichia coli preferred codons and chemically synthesized by ligation of synthetic fragments into a linearized plasmid followed by transformation into E. coli. A synthetic signal peptide (ompA) was fused to express the L chain as a free polypeptide into the periplasm of E. coli cells. After isolation and purification, heterologous recombination of the E. coli L chain with mouse H chain gave an active antigen-binding protein. The activity was 15-20% when compared to protein created by an equivalent association of isolated natural mouse L and H chains as measured by a direct EIA assay. In inhibition experiments with the polysaccharide antigen, the two proteins showed identical titration curves and 50% inhibition points, indicating comparable KA values. 相似文献
60.