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71.
72.
Exogenous nitric oxide enhances cadmium tolerance of rice by increasing pectin and hemicellulose contents in root cell wall 总被引:6,自引:0,他引:6
To study the mechanisms of exogenous NO contribution to alleviate the cadmium (Cd) toxicity in rice (Oryza sativa), rice plantlets subjected to 0.2-mM CdCl2 exposure were treated with different concentrations of sodium nitroprusside (SNP, a NO donor), and Cd toxicity was evaluated
by the decreases in plant length, biomass production and chlorophyll content. The results indicated that 0.1 mM SNP alleviated
Cd toxicity most obviously. Atomic absorption spectrometry and fluorescence localization showed that treatment with 0.1 mM
SNP decreased Cd accumulation in both cell walls and soluble fraction of leaves, although treatment with 0.1 mM SNP increased
Cd accumulation in the cell wall of rice roots obviously. Treatment with 0.1 mM SNP in nutrient solution had little effect
on the transpiration rate of rice leaves, but this treatment increased pectin and hemicellulose content and decreased cellulose
content significantly in the cell walls of rice roots. Based on these results, we conclude that decreased distribution of
Cd in the soluble fraction of leaves and roots and increased distribution of Cd in the cell walls of roots are responsible
for the NO-induced increase of Cd tolerance in rice. It seems that exogenous NO enhances Cd tolerance of rice by increasing
pectin and hemicellulose content in the cell wall of roots, increasing Cd accumulation in root cell wall and decreasing Cd
accumulation in soluble fraction of leaves. 相似文献
73.
Selenocysteine lyase activity was detected in crude extracts from a cysteine-requiring mutant ofEscherichia coli K-12. The level of activity was the same whether cells had been grown aerobically or anaerobically, with or without selenocysteine.
Selenocysteine lyase catalyzes the conversion of selenocysteine to alanine and elemental Se, a reaction that is followed by
a nonenzymatic reduction of the Se to hydrogen selenide. Both of these end products were identified in this study. With cysteine
as the substrate, alanine and H2S were formed, but only at levels 50% less than the products formed from selenocysteine. Selenocysteine lyase has been identified
in a number of mammals and bacteria; its presence in a cysK mutant ofE. coli K-12 suggests a common route whereby hydrogen selenide, derived from selenocysteine, can then be assimilated into selenoproteins. 相似文献
74.
Pechurskaya TA Harnastai IN Grabovec IP Gilep AA Usanov SA 《Biochemical and biophysical research communications》2007,353(3):598-604
The interaction of adrenodoxin (Adx) and NADPH cytochrome P450 reductase (CPR) with human microsomal steroidogenic cytochrome P450s was studied. It is found that Adx, mitochondrial electron transfer protein, is able to support reactions catalyzed by human microsomal P450s: full length CYP17, truncated CYP17, and truncated CYP21. CPR, but not Adx, supports activity of truncated CYP19. Truncated and the full length CYP17s show distinct preference for electron donor proteins. Truncated CYP17 has higher activity with Adx compared to CPR. The alteration in preference to electron donor does not change product profile for truncated enzymes. The electrostatic contacts play a major role in the interaction of truncated CYP17 with either CPR or Adx. Similarly electrostatic contacts are predominant in the interaction of full length CYP17 with Adx. We speculate that Adx might serve as an alternative electron donor for CYP17 at the conditions of CPR deficiency in human. 相似文献
75.
Pollen tube elongation in the pistil is a crucial step in the sexual reproduction of plants. Because the wall of the pollen tube tip is composed of a single layer of pectin and, unlike most other plant cell walls, does not contain cellulose or callose, pectin methylesterases (PMEs) likely play a central role in the pollen tube growth and determination of pollen tube morphology. Thus, the functional studies of pollen-specific PMEs, which are still in their infancy, are important for understanding the pollen development. We identified a new Arabidopsis pollen-specific PME, AtPPME1, characterized its native expression pattern, and used reverse genetics to demonstrate its involvement in determination of the shape of the pollen tube and the rate of its elongation. 相似文献
76.
Summary. This study aims to clarify the short- and long-term effects of the iron concentration in the medium on androgenesis induced
in barley by isolated microspore culture. The ultrastructural features and pectin composition of the intine wall were studied
in the initial stages of androgenesis. The evolution of electron-dense iron deposits on the intine was analysed in multicellular
pollen grains obtained by isolated microspore culture performed for 3, 6, and 9 days using various concentrations of FeNa2 EDTA. Finally, the number of embryo-like structures and green plants obtained by microspore culture using different Fe concentrations
was evaluated in order to estimate the optimum concentration for isolated microspore culture.
Correspondence and reprints: Departamento de Bioquimica, Biologia Celular y Molecular de Plantas, Estación Experimental del
Zaidin, Consejo Superior de Investigaciones Cientificas, Profesor Albareda 1, 18008 Granada, Spain. 相似文献
77.
Krichevsky A Kozlovsky SV Tian GW Chen MH Zaltsman A Citovsky V 《Developmental biology》2007,303(2):405-420
Sexual reproduction of flowering plants depends on delivery of the sperm to the egg, which occurs through a long, polarized projection of a pollen cell, called the pollen tube. The pollen tube grows exclusively at its tip, and this growth is distinguished by very fast rates and reaches extended lengths. Thus, one of the most fascinating aspects of pollen biology is the question of how enough cell wall material is produced to accommodate such rapid extension of pollen tube, and how the cell wall deposition and structure are regulated to allow for rapid changes in the direction of growth. This review discusses recent advances in our understanding of the mechanism of pollen tube growth, focusing on such basic cellular processes as control of cell shape and growth by a network of cell wall-modifying enzymes, molecular motor-mediated vesicular transport, and intracellular signaling by localized gradients of second messengers. 相似文献
78.
In the presence of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) damage, many DNA polymerases exhibit a dual coding potential which facilitates efficient incorporation of matched dCTP or mismatched dATP. This also holds true for the insertion of 8-oxodGTP opposite template bases dC and dA. Employing single-turnover kinetic methods, we examined human DNA polymerase beta and its novel X-family homolog, human DNA polymerase lambda, to determine which nucleotide and template base was preferred when encountering 8-oxodG and 8-oxodGTP, respectively. While DNA polymerase beta preferentially incorporated dCTP over dATP, DNA polymerase lambda did not modulate a preference for either dCTP or dATP when opposite 8-oxodG in single-nucleotide gapped DNA, as incorporation proceeded with essentially equal efficiency and probability. Moreover, DNA polymerase lambda is more efficient than DNA polymerase beta to fill this oxidized single-nucleotide gap. Insertion of 8-oxodGTP by both DNA polymerases lambda and beta occurred predominantly against template dA, thereby reiterating how the asymmetrical design of the polymerase active site differentially accommodated the anti and syn conformations of 8-oxodG and 8-oxodGTP. Although the electronegative oxygen at the C8 position of 8-oxodG may induce DNA structural perturbations, human DNA ligase I was found to effectively ligate the incorporated 8-oxodGMP to a downstream strand, which sealed the nicked DNA. Consequently, the erroneous nucleotide incorporations catalyzed by DNA polymerases lambda and beta as well as the subsequent ligation catalyzed by a DNA ligase during base excision repair are a threat to genomic integrity. 相似文献
79.
为探讨木薯MePMEI1的分子结构特征。通过PCR扩增和测序技术及生物信息学分析工具对木薯MePMEI1基因进行克隆、测序及相关生物信息学分析。结果表明木薯MePMEI1基因编码区全长609 bp,编码202个氨基酸残基;MePMEI1基因编码蛋白分子量21.78 k D,理论等电点(pI)约为5.51;生物信息学预测发现,木薯MePMEI1蛋白是稳定的亲水蛋白;具有跨膜区为分泌蛋白;含有1个PMEI结构域,1个糖基化位点,31个磷酸化位点;二、三级结构以α螺旋和无规则卷曲为主。该蛋白的生物功能可能与细胞被膜、酶和生长因子等相关。木薯MePMEI1基因的生物信息学分析为进一步研究其遗传特性和生理生化机制提供了理论依据。 相似文献
80.
Alginate lyase which was purified from the fermentation solution of marine bacteria Pseudomonas sp. HJZ216 was applied to hydrolyze algae alginate. Six oligosaccharides, including di- and trisaccharides, were isolated and purified through anion exchange chromatography. The oligosaccharide structures were elucidated based on electrospray ionization-mass spectrometry (ESI-MS) and 2D NMR spectra analysis. 相似文献