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901.
5-(4-Methylthio-2-phthalimidylbutanoylamino)isophthalic acid (5) as a novel diacid monomer containing phthalimide and flexible chiral groups was prepared by dehydration of l-methionine and phthalic anhydride followed by reacting with thionyl chloride and then treating with 5-aminoisophthalic acid
(5AIPA) in dry N,N-dimethylacetamide (DMAc). A series of novel polyesters (PEs) containing phthalimide group was prepared by the reaction of
diacid monomer 5 with several aromatic diols via direct polyesterification with tosyl chloride/pyridine/dimethylformamide (DMF) system as
condensing agent. The resulting new polymers were obtained in good yields and inherent viscosities ranging between 0.21 and
0.51 dLg−1 were characterized with FT-IR, 1H NMR, elemental and thermogravimetric analysis techniques. These polymers are readily soluble in polar organic solvents such
as DMAc, DMF, dimethyl sulfoxide and protic solvents such as sulfuric acid. Specific rotation experiments demonstrate the
optical activity induction due to successful insertion of l-methionine in the structure of pendent groups. Thermogravimetric analysis showed that the 10% weight loss temperature in
a nitrogen atmosphere were more than 315°C, which indicates that the resulting PEs have good thermal stability. 相似文献
902.
Effective selectable markers are needed for basic research and commercial applications that do not involve antibiotic or herbicide
resistance. A novel selection system based on a feedback-insensitive anthranilate synthase α-subunit of tobacco (ASA2) as
selectable marker using either 4-methylindole (4MI) or 7-methyl-DL-tryptophan (7MT) as the selection agent was developed. We found that these two components were able to discriminate better
between ASA2 expressing and untransformed lines than the most commonly used analog 5-methyltryptopan (5MT) in the seedling
growth inhibition test. We successfully integrated an expression cassette containing an ASA2 cDNA driven by a cauliflower
mosaic virus 35S promoter into tobacco leaf discs by A. tumefaciens and selected transgenic plants on medium supplemented with 300 μM of 7MT or 4MI. Due to the expression of the feedback-insensitive
ASA2, the transgenic lines produced showed higher free tryptophan (Trp) concentrations than the untransformed WT control.
These results demonstrate the feasibility of the selection system with the ASA2 gene in combination with the use of Trp or
indole analogs as selective agent. 相似文献
903.
Sebastián Sánchez Vicente Bravo Juan Francisco García Nicolás Cruz Manuel Cuevas 《World journal of microbiology & biotechnology》2008,24(5):709-716
The fermentation of d-glucose and d-xylose mixtures by the yeast Candida tropicalis NBRC 0618 has been studied under the most favourable operation conditions for the culture, determining the most adequate
initial proportion in these sugars for xylitol production. In all the experiments a synthetic culture medium was used, with
an initial total substrate concentration of 25 g L−1, a constant pH of 5.0 and a temperature of 30 °C. From the experimental results, it was deduced that the highest values of
specific rates of production and of overall yield in xylitol were achieved for the mixtures with the highest percentage of
d-xylose, specifically in the culture with the initial d-glucose and d-xylose concentrations of 1 and 24 g L−1, respectively, with an overall xylitol yield of 0.28 g g−1. In addition, the specific rates of xylitol production declined over the time course of the culture and the formation of
this bioproduct was favoured by the presence of small quantities of d-glucose. The sum of the overall yield values in xylitol and ethanol for all the experiments ranged from 0.26 to 0.56 g bioproduct/g
total substrate. 相似文献
904.
Yan Zhen Mei Bing Fang He Ping Kai Ouyang 《World journal of microbiology & biotechnology》2008,24(3):375-381
Bacillus fordii MH602 was newly screened from soil at 45 °C and exhibited high activities of hydantoinase and carbamoylase, efficiently yielding
l-amino acids including phenylalanine, phenylglycine and tryptophan with the bioconversion yield of 60–100% from the corresponding
dl-5-substituted hydantoins. Hydantoinase activity was found to be cell-associated and inducible. The optimal inducer was dl-5-methylhydantoin with concentration of 0.014 mol L−1 and added to the fermentation medium in the exponential phase of growth. In the production of optically pure amino acids
from dl-5-benylhydantoin, the optimal temperature and pH of this reaction were 45–50 °C and 7.5 respectively. The hydantoinase was
non-stereoselective, while carmbamoylase was l-selective. The hydantoinase activity was not subject to substrate inhibition, or product inhibition by ammonia. In addition,
The activities of both enzymes from crude extract of the strain were thermostable; the hydantoinase and carbamoylase retained
about 90% and 60% activity after 6 h at 50 °C, respectively. Since reaction at higher temperature is advantageous for enhancement
of solubility and for racemization of dl-5-substituted hydantoins, the relative paucity of l-selective hydantoinase systems, together with the high level of hydantoinase and carbamoylase activity and unusual substrate
selectivity of the strain MH602, suggest that it has significant potential applications. 相似文献
905.
Tianli Tian Qiling Sun Jing Shen Tao Zhang Pei Gao Qun Sun 《World journal of microbiology & biotechnology》2008,24(6):861-866
Rhizopus microsporus isolated by our laboratory was able to transform polydatin into resveratrol and emodin-8-β-d-glucoside into emodin, respectively, through the fermentation of Polygonum cuspidatum Sieb. et Zucc. The fermentation products were separated and purified by H1020 resin and silica gel column chromatography.
Thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) were used to identify the products and evaluate
the transformation efficiency. A variety of parameters of submerged state fermentation, including the growth characteristics,
the change of β-glucosidase activity and the amount of polydatin, resveratrol, emodin-8-β-d-glucoside, emodin, and the dissolved oxygen, were monitored simultaneously. The amount of resveratrol yielded increased dramatically
from 0.04 g/l at the beginning to the maximum value of 0.34 g/l at 36 h of fermentation, and emodin was from 0.4 g/l to 0.65 g/l
at 80 h. The transformation rate of glycosides reached 98% and the purity of both resveratrol and emodin was 95%. 相似文献
906.
Binod Babu Pageni Tae-Jin Oh Jin Cheol Yoo Jae Kyung Sohng 《Biotechnology and Bioprocess Engineering》2008,13(6):752-757
Two genes, orf6 and orf9 located in the L-oleandrose sugar biosynthetic gene cluster of Streptomyces antibioticus Tü99. NovU has been characterized as C-5 methyltrnaferase involved in noviose biosynthetic pathway. We have cloned and heterologously
expressed the orf6, orf9, and novU genes in S. venezuelae YJ003-OTBP1. This established the function of orf6 and orf9 as 4-ketoreductase and 3-epimerase, respectively. All of analytical data of the noviosylated 10-deoxymethynolide also is
in support of proving their functions. Furthermore biosynthetic pathway 5,5-gem-dimethyl-6-deoxyglucose (TDP-Lnoviose) has been proposed. 相似文献
907.
The present study investigated the effects of three constituent amino acids on glutathione production in flask culture of
Candida utilis. Although l-glutamic acid and glycine had little impact on cell growth and glutathione biosynthesis, l-cysteine positively influenced glutathione production, despite inhibiting cell growth when it was added prior to stationary
phase. Adding 8 mmol/L of l-cysteine to the culture broth at 16 h boosted glutathione production by 91%, increasing the intracellular glutathione content
by 106% compared to untreated controls. A temperature-shift strategy, in which we shifted batch and fed-batch cultures of
C. utilis from 30 to 26°C, also significantly enhanced glutathione production. Applying both strategies (i.e. adding 20 mmol/L l-cysteine and shifting the temperature from 30 to 26°C) at 33 h enhanced the glutathione concentration and the intracellular
glutathione content to 1,312 mg/L and 3.75%, respectively, during fed-batch cultivation (glucose feeding at a constant rate
of 18.3 g/h). The average specific glutathione production rate under this condition was 129% higher than that of the control
without strategy. 相似文献
908.
Poly(ε-l-lysine) (ε-PL) is a naturally occurring poly(amino acid) characterized by a unique structure linking ε-amino and carboxyl
groups of l-lysine. Due to its various functions and its biodegradability and non-toxicity, the ε-PL polymer has attracted increasing
attention in recent years. ε-PL is frequently found in various strains of Streptomyces sp. This review gives an up-to-date overview regarding the biosynthesis of ε-PL focussing mainly on results obtained from
ten newly isolated producer strains, using the two-stage culture method of cell growth and ε-PL production cultures. The production
of nearly monodispersed ε-PL is covered together with the development of ε-PL specific hydrolases and the release of synthesized
ε-PL into the culture broth. From these results, coupled with the termination of polymerization through nucleophilic chain
transfer, the biosynthetic mechanism of the polymer is discussed. 相似文献
909.
d-Galactosamine (d-GaIN) is a highly selective hepatotoxin that causes liver injury similar to human viral hepatitis via depletion of uridine
nucleotides, which subsequently diminishes synthesis of RNA and proteins. The aim of this study was to investigate the role
of selenium, ascorbic acid, beta-carotene, and alpha-tocopherol on d-GaIN-induced liver injury of rats by morphological and immunohistochemical means. In this study, Sprague–Dawley female rats
were divided into four groups. Group I consists of rats injected physiologic saline solution intraperitoneally. Group II consists
of rats given selenium (0.2 mg/kg per day), ascorbic acid (100 mg/kg per day), beta-carotene (15 mg/kg per day), and alpha-tocopherol
(100 mg/kg per day) for 3 days via gavage method. Group III consists of the single dose of d-GaIN (500 mg/kg)-injected animals. Group IV are the d-GaIN-injected animals given the same antioxidant combination. In situ terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine
5′-triphosphate nick-end labeling (TUNEL) assay was applied to determine apoptosis for paraffin sections of the liver samples.
Moreover, caspase-3 and proliferating cell nuclear antigen antibody were applied for paraffin sections. In the group given
d-GaIN, apoptotic cells with TUNEL assays and caspase-3 activity, which are liver injury markers induced by d-GaIN, the hepatocyte proliferation with cell proliferation assay increased. However, selenium and other three antioxidants
combination clearly suppressed an increase in apoptotic cells with TUNEL assay and caspase-3 activity. In addition, it suppressed
d-GaIN-induced cell proliferation in the liver. As a result, these results indicate that selenium and three naturally occurring
antioxidants shows a protective effect against liver injury induced by d-GaIN. These results suggest that supplementation with the combination of selenium, ascorbic acid, beta-carotene, and alpha-tocopherol
may help prevent the development of liver injury. 相似文献
910.
Researchers have suggested that several types of agonistic and affiliative behavior covary as a set of species-specific traits,
and have used the term dominance style to describe the covariation. We compared measures of dominance style between a group
of Assamese macaques (Macaca assamensis) and a group of rhesus macaques (M. mulatta), though kinship information was unknown. Assamese and rhesus female-female dyads each showed a low proportion of counter
aggression and a low conciliatory tendency, suggesting that they have despotic social relationships. They also showed a despotic
pattern on several other types of agonistic and affiliative behavior, such as approach outcomes and grooming distributions,
which is consistent with the covariation of dominance style traits. Assamese male-male dyads showed relatively high levels
of reconciliation and counter aggression versus other macaque males portrayed in the literature, suggesting that Assamese
males have a tolerant dominance style. Insofar as macaque dominance style depends on the behavior of females, we suggest that
Assamese macaques, like rhesus macaques, have despotic social relationships, which contrasts with evidence of a strong correlation
between phylogeny and dominance style in macaques. Further, our results indicate that strong male bonding and tolerant dominance
relationships among males are independent of female dominance style. Lastly, some measures of agonistic behavior, such as
rate of aggression or proportion of bites, are likely altered in competitive environments and thus are not useful indicators
of dominance style. 相似文献