全文获取类型
收费全文 | 1696篇 |
免费 | 67篇 |
国内免费 | 3篇 |
出版年
2023年 | 21篇 |
2022年 | 40篇 |
2021年 | 77篇 |
2020年 | 56篇 |
2019年 | 50篇 |
2018年 | 73篇 |
2017年 | 58篇 |
2016年 | 92篇 |
2015年 | 89篇 |
2014年 | 109篇 |
2013年 | 133篇 |
2012年 | 166篇 |
2011年 | 143篇 |
2010年 | 90篇 |
2009年 | 69篇 |
2008年 | 65篇 |
2007年 | 50篇 |
2006年 | 40篇 |
2005年 | 47篇 |
2004年 | 34篇 |
2003年 | 37篇 |
2002年 | 26篇 |
2001年 | 24篇 |
2000年 | 21篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 14篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1973年 | 2篇 |
1972年 | 6篇 |
1971年 | 2篇 |
排序方式: 共有1766条查询结果,搜索用时 781 毫秒
121.
The present investigation was aimed at developing cytarabine-loaded poly(lactide-coglycolide) (PLGA)-based biodegradable nanoparticles
by a modified nanoprecipitation which would have sustained release of the drug. Nine batches were prepared as per 32 factorial design to optimize volume of the co-solvent (0.22–0.37 ml) and volume of non-solvent (1.7–3.0 ml). A second 32 factorial design was used for optimization of drug: polymer ratio (1:5) and stirring time (30 min) based on the two responses,
mean particle size (125 ± 2.5 nm), and percentage entrapment efficiency (21.8 ± 2.0%) of the Cyt-PLGA nanoparticles. Optimized
formulation showed a zeta potential of −29.7 mV indicating good stability; 50% w/w of sucrose in Cyt-PLGA NP was added successfully as cryoprotectant during lyophilization for freeze-dried NPs and showed
good dispersibility with minimum increase in their mean particle sizes. The DSC thermograms concluded that in the prepared
PLGA NP, the drug was present in the amorphous phase and may have been homogeneously dispersed in the PLGA matrix. In vitro drug release from the pure drug was complete within 2 h, but was sustained up to 24 h from PLGA nanoparticles with Fickian
diffusion. Stability studies showed that the developed PLGA NPs should be stored in the freeze-dried state at 2–8°C where
they would remain stable in terms of both mean particle size and drug content for 2 months. 相似文献
122.
A biochemical investigation of arabinogalactan proteins (AGPs) in Physcomitrella
patens was undertaken with particular emphasis on the glycan chains. Following homogenization and differential centrifugation of
moss gametophytes, AGPs were obtained by Yariv phenylglycoside-induced precipitation from the soluble, microsomal membrane,
and cell wall fractions. Crossed-electrophoresis indicated that each of these three AGP fractions was a mixture of several
AGPs. The soluble AGP fraction was selected for further separation by anion-exchange and gel-permeation chromatography. The
latter indicated molecular masses of ∼100 and 224 kDa for the two major soluble AGP subfractions. The AGPs in both of these
subfractions contained the abundant (1,3,6)-linked galactopyranosyl residues, terminal arabinofuranosyl residues, and (1,4)-linked
glucuronopyranosyl residues that are typical of many angiosperm AGPs. Unexpectedly, however, the moss AGP glycan chains contained
about 15 mol% terminal 3-O-methyl-l-rhamnosyl residues, which have not been found in angiosperm AGPs. This unusual and relatively nonpolar sugar, also called
l-acofriose, is likely to have considerable effects on the overall polarity of Physcomitrella AGPs. A review of the literature indicates that the capacity to synthesize polymers containing 3-O-methyl-l-rhamnosyl residues is present in a variety of bacteria, algae and lower land plants but became less common through evolution
to the extent that this sugar has been found in only a few species of angiosperms where it occurs as a single residue on steroidal
glycosides. 相似文献
123.
Phosphate solubilizing microorganisms are ubiquitous in soils and could play an important role in supplying P to plants where
plant unavailable P content in soil was more. A phosphatase and phytase producing fungus Emericella rugulosa was isolated and tested under field condition (Pearl millet as a test crop) in a loamy sand soil. In the experimental soil
68% organic phosphorous was present as phytin; less than 1% of phosphorous was present in a plant available form. The maximum
effect of inoculation on different enzyme activities (acid phosphatase, alkaline phosphatase, phytase, and dehydrogenase)
was observed between 5 and 8 weeks of plant age. The depletion of organic P was much higher than mineral and phytin P. The
microbial contribution was significantly higher than the plant contribution to the hydrolysis of the different P fractions.
A significant improvement in plant biomass, root length, seed and straw yield and P concentration of root and shoot resulted
from inoculation. The results suggest that Emericella rugulosa produces phosphatases and phytase, which mobilize P and enhance the production of pearl millet. 相似文献
124.
A pectin lyase (PNL, EC 4.2.2.10) produced extracellularly by the strain of Penicillium oxalicum in solid-state fermentation medium containing deoiled mandarin orange peel meal was purified to apparent homogeneity by a protocol that included ammonium sulfate precipitation, DEAE-Sephadex A-50 and Sephadex G-100 chromatography. The enzyme had molecular mass of 50 kD, as determined by SDS- PAGE and showed optimum pH and temperature at 8.0 and 50 degrees C respectively. It had an isoelectric point (pI) of 5.0 and showed a K(m) of 1.1 mg/ml of citrus pectin. The enzyme was strongly inhibited by Mo4+, Ag+ and Pb2+ and also by polyphenolic compounds, in particular tannic acid. 相似文献
125.
Gupta S Singh A Yadav M Singh K Rathaur S 《Biochemical and biophysical research communications》2007,356(2):381-385
Glutathione-S-transferase has been detected in the somatic extract and excretory-secretory products of different life stages of Setaria cervi, a bovine filarial parasite. The enzyme was subjected to MALDI-TOF followed by mass spectrometry and the nearest match found was Pleuronectes platessa GST. Molecular mass of the purified enzyme was approximately 26 kDa as determined by SDS-PAGE and MALDI-TOF. Setaria cervi GST exhibited high activity towards 1-chloro-2,4-dinitrobenzene and ethacrynic acid. Kinetic analysis with respect to 1-chloro-2,4-dinitrobenzene and glutathione as substrate revealed a K(m) of 2.22 mM and 0.61 mM, respectively. The activity was inhibited significantly by Cibacron blue and alpha-tocopherol. 相似文献
126.
Ramajayam R Giridhar R Yadav MR Djaballah H Shum D Radu C 《Journal of enzyme inhibition and medicinal chemistry》2007,22(6):716-721
Novel substituted 5,7-diaryl-2,3-dihydro-1,4-diazepines and 4,6-diaryl-2-aminopyrimidines were synthesized and tested for their antiproliferative activity. Title compounds were obtained by cyclocondensation of a substituted flavone with ethylenediamine and guanidine respectively. The cytotoxicity in vitro against various human leukemic cancer cell lines viz., Jurkat, HL60, MOLT3, NCEB-1, K562 was determined. 相似文献
127.
AFD-Net: Apple Foliar Disease multi classification using deep learning on plant pathology dataset 总被引:2,自引:0,他引:2
Yadav Anju Thakur Udit Saxena Rahul Pal Vipin Bhateja Vikrant Lin Jerry Chun-Wei 《Plant and Soil》2022,477(1-2):595-611
Plant and Soil - Plant diseases significantly affect the crop, so their identification is very important. Correct identification of these diseases is crucial for establishing a good disease control... 相似文献
128.
Singh Awtar Bali Aradhana Kumar Ashwani Yadav Rajender Kumar Minhas Paramjit Singh 《Journal of Plant Growth Regulation》2022,41(5):1989-1998
Journal of Plant Growth Regulation - Exogenous applications of plant growth regulators (PGRs) were evaluated for their effects on growth, physiological attributes, and yield of sodicity stressed... 相似文献
129.
Bego?a Carrasco Tribhuwan Yadav Ester Serrano Juan C. Alonso 《Nucleic acids research》2015,43(12):5984-5997
Genetic data have revealed that the absence of Bacillus subtilis RecO and one of the end-processing avenues (AddAB or RecJ) renders cells as sensitive to DNA damaging agents as the null recA, suggesting that both end-resection pathways require RecO for recombination. RecA, in the rATP·Mg2+ bound form (RecA·ATP), is inactive to catalyze DNA recombination between linear double-stranded (ds) DNA and naked complementary circular single-stranded (ss) DNA. We showed that RecA·ATP could not nucleate and/or polymerize on SsbA·ssDNA or SsbB·ssDNA complexes. RecA·ATP nucleates and polymerizes on RecO·ssDNA·SsbA complexes more efficiently than on RecO·ssDNA·SsbB complexes. Limiting SsbA concentrations were sufficient to stimulate RecA·ATP assembly on the RecO·ssDNA·SsbB complexes. RecO and SsbA are necessary and sufficient to ‘activate’ RecA·ATP to catalyze DNA strand exchange, whereas the AddAB complex, RecO alone or in concert with SsbB was not sufficient. In presence of AddAB, RecO and SsbA are still necessary for efficient RecA·ATP-mediated three-strand exchange recombination. Based on genetic and biochemical data, we proposed that SsbA and RecO (or SsbA, RecO and RecR in vivo) are crucial for RecA activation for both, AddAB and RecJ–RecQ (RecS) recombinational repair pathways. 相似文献
130.
Pravin Patil Surendra Kumar Malik Shrikant Sutar Shrirang Yadav Joseph John Kangila Venkataraman Bhat 《Nordic Journal of Botany》2015,33(6):696-707
Seed morphology of Abelmoschus is known to be variable, but patterns of variation have never been critically studied. We studied seed macro‐ and micro‐morphological characters, including seed shape/size, seed coat pattern and trichome density/structure in multiple samples to evaluate the taxonomic significance of seed characters. Among the studied characters, seed shape and trichome structure were found to have major taxonomic importance and proved to be valuable characters for separating taxa. Two main seed types were present: seeds with deciduous trichomes and seeds with persistent trichomes. These characters offer significant evidence to the distinctness of certain species (A. esculentus, A. moschatus subsp. moschatus, A. moschatus subsp. tuberosus, A. crinitus and A. angulosus). Further, our results indicate that A. moschatus subsp. tuberosus should be maintained as a separate subspecies while A. manihot subsp. tetraphyllus var. pungens may be merged in A. angulosus. No significant intraspecific variation was observed, except in A. esculentus. We conclude that seed coat sculpturing and seed trichomes do indeed provide stable and diagnostic characters for many morphologically closely related taxa of Abelmoschus and that LM/SEM techniques can be useful in solving systematic problems and management of Abelmoschus genetic resources. 相似文献