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81.
Biologically active ingredients and excipients are the essentials of a drug formulation, such as a tablet, dragee, solution, etc. Quality control of such substances thus plays a pivotal role in the production process of pharmaceutical drugs. Since these agents often exhibit complex structures, consist of multiple components, or lack of a chromophore, traditional means of characterization are often not feasible. Furthermore, substances of small molecular weight or strong polar character generally exhibit poor chromatographic properties, thus, conventional procedures such as high-performance liquid chromatography are often not applicable. Instead, quantitative nuclear magnetic resonance (qNMR) spectroscopy has emerged as an alternative or orthogonal method in drug analysis. In this review, we elaborate on the application of qNMR to three important classes of biological substances, namely polysaccharides, amino acids, and lipids, and demonstrate the benefits of this modern tool in contrast to traditional techniques. 相似文献
82.
Carotenoids are converted by carotenoid cleavage dioxygenases that catalyze oxidative cleavage reactions leading to apocarotenoids.
However, apocarotenoids can also be further truncated by some members of this enzyme family. The plant carotenoid cleavage
dioxygenase 1 (CCD1) subfamily is known to degrade both carotenoids and apocarotenoids in vitro, leading to different volatile
compounds. In this study, we investigated the impact of the rice CCD1 (OsCCD1) on the pigmentation of Golden Rice 2 (GR2),
a genetically modified rice variety accumulating carotenoids in the endosperm. For this purpose, the corresponding cDNA was
introduced into the rice genome under the control of an endosperm-specific promoter in sense and anti-sense orientations.
Despite high expression levels of OsCCD1 in sense plants, pigment analysis revealed carotenoid levels and patterns comparable
to those of GR2, pleading against carotenoids as substrates in rice endosperm. In support, similar carotenoid contents were
determined in anti-sense plants. To check whether OsCCD1 overexpressed in GR2 endosperm is active, in vitro assays were performed
with apocarotenoid substrates. HPLC analysis confirmed the cleavage activity of introduced OsCCD1. Our data indicate that
apocarotenoids rather than carotenoids are the substrates of OsCCD1 in planta. 相似文献
83.
84.
Beyer EM 《Plant physiology》1975,56(2):273-278
The effects of various treatments on the recently reported system in pea (Pisum sativum cv. Alaska), which results in (a) the incorporation of 14C2H4 into the tissue and (b) the conversion of 14C2H4 to 14CO2, was investigated using 2-day-old etiolated seedlings which exhibit a maximum response. Heat treatment (80 C, 1 min) completely inhibited both a and b, whereas homogenization completely inhibited b but only partially inhibited a. Detaching the cotyledons from the root-shoot axis immediately before exposing the detached cotyledons together with the root-shoot axis to 14C2H4 markedly reduced both a and b. Increasing the 14C2H4 concentration from 0.14 to over 100 μl/l progressively increased the rate of a and b with tissue incorporation being greater than 14C2H4 to 14CO2 conversion only below 0.3 μl/l 14C2H4. Reduction of the O2 concentration reduced both a and b, with over 99% inhibition occurring under anaerobic conditions. The addition of CO2 (5%) severely inhibited 14C2H4 to 14CO2 conversion without significantly affecting tissue incorporation. Exposure of etiolated seedlings to fluorescent light during 14C2H4 treatment was without effect. Similarly, indoleacetic acid, gibberellic acid, benzyladenine, abscisic acid, and dibutyryl cyclic adenosine monophosphate had no significant effect on either a or b. 相似文献
85.
In our study of the biosynthesis of D-desosamine in Streptomyces venezuelae, we have cloned and sequenced the entire desosamine biosynthetic cluster. The deduced product of one of the genes, desR, in this cluster shows high sequence homology to beta-glucosidases, which catalyze the hydrolysis of the glycosidic linkages, a function not required for the biosynthesis of desosamine. Disruption of the desR gene led to the accumulation of glucosylated methymycin/neomethymycin products, all of which are biologically inactive. It is thus conceivable that methymycin/neomethymycin may be produced as inert diglycosides, and the DesR protein is responsible for transforming these antibiotics from their dormant to their active forms. This hypothesis is supported by the fact that the translated desR gene has a leader sequence characteristic of secretory proteins, allowing it to be transported through the cell membrane and hydrolyze the modified antibiotics extracellularly to activate them. Expression of desR and biochemical characterization of the purified protein confirmed the catalytic function of this enzyme as a beta-glycosidase capable of catalyzing the hydrolysis of glucosylated methymycin/neomethymycin produced by S. venezuelae. These results provide strong evidence substantiating glycosylation/deglycosylation as a likely self-resistance mechanism of S. venezuelae. However, further experiments have suggested that such a glycosylation/deglycosylation is only a secondary self-defense mechanism in S. venezuelae, whereas modification of 23S rRNA, which is the target site for methymycin and its derivatives, by PikR1 and PikR2 is a primary self-resistance mechanism. Considering that postsynthetic glycosylation is an effective means to control the biological activity of macrolide antibiotics, the availability of macrolide glycosidases, which can be used for the activation of newly formed antibiotics that have been deliberately deactivated by engineered glycosyltransferases, may be a valuable part of an overall strategy for the development of novel antibiotics using the combinatorial biosynthetic approach. 相似文献
86.
An ultrasensitive colorimetric assay for manganese is described. It is based upon the catalysis, by Mn(II), of the photochemical oxidation of o-dianisidine, sensitized by riboflavin. Catalase increases the Mn(II)-catalyzed rate of photosensitized oxidation of dianisidine to the bisazobiphenyl, while superoxide dismutase inhibits the rate. The mechanism appears to involve oxidation of Mn(II) by O2-, followed by oxidation of dianisidine by MnO2+ in equilibrium Mn(III). Cu(II) interferes, but Zn(II), Fe(II), Fe(III), Co(II), and Ni(II) do not. Chelating agents and thiol reductants also interfere. Interference by Cu(II) can be overcome by the addition of cyanide, while interference by organic compounds can be surmounted by wet ashing. This assay provides a linear response to Mn(II) over the range 10-2500 nM. The limit of detection was 5 nM Mn(II). 相似文献
87.
Z H Zhao B Watschinger C D Brown M M Beyer E A Friedman 《Hormones et métabolisme》1987,19(11):534-537
The variations of susceptibility to alloxan induced Diabetes in a total of seventeen rabbits was described. Our study was designed to explore dosage schedules which might improve rabbit responsiveness to and survival after alloxan treatment. A wide range of response to intravenously administered alloxan was observed. Permanent diabetes (blood glucose 350 mg/dl) was found in three rabbits after a single injection (60 mg/kg in one, 100 mg/kg in two). This effect has persisted for eight months. By contrast, two other rabbits injected with a single dose of alloxan (60 mg/kg) developed only transient hyperglycemia. Similarly, four other rabbits either did not respond or had an incomplete response after receiving a total dose of 120 mg/kg. These data suggest that there is extreme variability in individual rabbits susceptibility to the diabetogenic affects of alloxan. 相似文献
88.
89.
Matias Pasquali Marco Beyer Torsten Bohn Lucien Hoffmann 《Journal of Phytopathology》2011,159(10):700-704
Genetic chemotyping is an essential tool for characterizing Fusarium populations causing head blight on wheat and other cereals. Three PCR methods, based on tri cluster polymorphism, were optimized and compared on 94 single‐spore isolates obtained from three continents belonging to F. gramineaurm, F. culmorum, F. poae, F. avenaceum and Microdochium nivale. While the methods based on the tri3, tri7 and tri12 polymorphism correctly identified all the tested strains, the method based on tri13 polymorphism was unable to discriminate between the 3‐ and 15‐acetylated DON forms in F. graminearum. It is advised to avoid the use of tri13 polymorphism for genetic chemotyping of the two acetylated chemotypes. 相似文献
90.
Robert E. Beyer 《Free radical biology & medicine》1988,5(5-6):297-303
The ability of coenzyme Q to inhibit lipid peroxidation in intact animals as well as in mitochondrial, submitochondrial, and microsomal systems has been tested. Rats fed coenzyme Q prior to being treated with carbon tetrachloride or while being treated with ethanol excrete less thiobarbituric acid-reacting material in the urine than such rats not fed coenzyme Q. Liver homogenates, mitochondria, and microsomes isolated from rats treated with carbon tetrachloride and ethanol catalyze lipid peroxidation at rates which exceed those from animals also fed coenzyme Q. The rate of lipid peroxidation catalyzed by submitochondrial particles isolated from hearts of young, old, and endurance trained elderly rats was inversely proportional to the coenzyme Q content of the submitochondrial preparation in assays in which succinate was employed to reduce the endogenous coenzyme Q. Reduced, but not oxidized, coenzyme Q inhibited lipid peroxidation catalyzed by rat liver microsomal preparations. These results provide additional evidence in support of an antioxidant role for coenzyme Q. 相似文献