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1.
Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
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2.
Evolutionary origin of human and primate malarias: evidence from the circumsporozoite protein gene 总被引:8,自引:1,他引:7
We have analyzed the conserved regions of the gene coding for the
circumsporozoite protein (CSP) in 12 species of Plasmodium, the malaria
parasite. The closest evolutionary relative of P. falciparum, the agent of
malignant human malaria, is P. reichenowi, a chimpanzee parasite. This is
consistent with the hypothesis that P. falciparum is an ancient human
parasite, associated with humans since the divergence of the hominids from
their closest hominoid relatives. Three other human Plasmodium species are
each genetically indistinguishable from species parasitic to nonhuman
primates; that is, for the DNA sequences included in our analysis, the
differences between species are not greater than the differences between
strains of the human species. The human P. malariae is indistinguishable
from P. brasilianum, and P. vivax is indistinguishable from P. simium; P.
brasilianum and P. simium are parasitic to New World monkeys. The human P.
vivax-like is indistinguishable from P. simiovale, a parasite of Old World
macaques. We conjecture that P. malariae, P. vivax, and P. vivax-like are
evolutionarily recent human parasites, the first two at least acquired only
within the last several thousand years, and perhaps within the last few
hundred years, after the expansion of human populations in South America
following the European colonizations. We estimate the rate of evolution of
the conserved regions of the CSP gene as 2.46 x 10(-9) per site per year.
The divergence between the P. falciparum and P. reichenowi lineages is
accordingly dated 8.9 Myr ago. The divergence between the three lineages
leading to the human parasites is very ancient, about 100 Myr old between
P. malariae and P. vivax (and P. vivax-like) and about 165 Myr old between
P. falciparum and the other two.
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3.
A Taddeo A Renieri A Fioravanti G Morozzi E Parrini M S D'Amato M G Ricci 《Bollettino della Società italiana di biologia sperimentale》1984,60(9):1709-1714
Modifications on the binding of uric acid to human plasma proteins have been studied in regularly menstruating females aged 25-30 years with a normal cycle, in comparison with a group of healthy age-matched males and with a group of post-menopausal females. The binding of uric acid to plasma proteins was estimated using micropartition system Amicon. The results obtained demonstrate a significant increase of uric acid binding during ovulatory and mid-luteal phase of menstrual cycle. No modifications are shown in post-menopausal females and in healthy males. No modifications have been shown with the same experiments performed in vitro. 相似文献
4.
Photosynthetic enhancement studies performed at 619 nm (excitation of Systems I and II) and at 446 nm (mainly excitation of System I) revealed an 18% photosynthetic enhancement simultaneously with a 31% reduction in glycolate excretion. This observation supports the hypothesis that some glycolate may be consumed in an oxidation process associated with System I when System II is poorly excited and the supply of electrons from the water splitting process of photosynthesis is low. 相似文献
5.
Concentrations of calcium and magnesium were determined for 39 lots of media, including broth and agar media used for susceptibility
tests and plain agar. In addition, the effect that media with and without physiological levels of these divalent cations would
have on the disk diffusion susceptibility of 21 strains ofPseudomonas aeruginosa to four antimicrobics was also ascertained. Mueller-Hinton agar showed a wide variation in calcium and magnesium content.
Mueller-Hinton broth contained lower concentrations of calcium and magnesium, and there was little lot-to-lot variation. Lots
of Mueller-Hinton agar with higher concentrations of calcium and magnesium yielded smaller zone diamaters than those with
lower concentrations. Even at equal cation concentration, zones of inhibition varied from lot to lot. Since the addition of
calcium and magnesium to Mueller-Hinton agar to obtain a predetermined level did not result in equivalent zone diameters,
performance testing of susceptibility media is recommended. 相似文献
6.
Summary Intact embryos (with suspensor) ofPhaseolus coccineus (2 n=2 x=22) in different stages of development were grownin vitro on hormone-free medium under conditions favoring callus formation from the portion of the suspensor proximal to the embryo (handle portion). It was shown that callus formation was dependent upon the developmental stage of the embryo and the integrity of the embryo-suspensor system.Callus formation from the handle portion of the suspensor, whose cells have nuclei with DNA values from 4 C to 128 C, was initiated by amitosis (nuclear fragmentation) which led to binucleate and multinucleate cells. Amitosis was followed by mitosis of both nuclei resulting from a previous amitosis and nuclei of euploid cells (mostly diploid) pre-existing in the suspensor. The majority of mitoses (88%) had either a reduced chromosome number (hypodiploid, haploid, and hypohaploid) or the diploid number (22 chromosomes).The very high incidence of cells with reduced chromosome number in the suspensor callus is discussed in relation to its mechanism of origin and to its possible exploitation in plant regeneration experiments. 相似文献
7.
Abstract— Plasmalogenase was assayed by measuring the disappearance of the plasmalogen by two-dimensional thin-layer chromatography. The enzyme was present in a glycerol-bicarbonate extract of an acetone-dried powder from bovine brain. With ethanolamine plasmalogens as the substrate, the Km was 180 μM. Diacyl glycerophosphorylcholines, diacyl glycerophosphorylethanolamines and choline plasmalogens were competitive inhibitors. With choline plasmalogens as the substrate, the Km was 208 μM and competitive inhibition was observed with diacyl glycerophosphorylcholines and ethanolamine plasmalogens. The same enzyme may be responsible for the hydrolysis of the alk-1-enyl moiety from both plasmalogens. Plasmalogenase activity was 5.1 μmol/h/g of dog brain, 3.9 μmol/h/g of rat brain and 3.4 μmol/h/g of gerbil brain. A lysophospholipase was also found in the glycerol-bicarbonate extract from the acetone-dried powder. The lysophospholipase was more active in hydrolysing acyl groups from 2-acyl-sn-glycero-3-phosphorylethanolamines than the plasmalogenase was active in hydrolyzing alk-1-enyl groups from 1-alk-1′-enyl-2-acyl-sn-glycero-3-phosphorylethanolamines. 相似文献
8.
Dott. Francesco D'Amato 《Plant biosystems》2013,147(2):349-382
Riassunto L'A. stabilisce che in Plumbago capensis Thunb., accanto allo sviluppo secondo lo schema del tipo Plumbago, si riscontra, con bassissima frequenza, un nuovo tipo di sviluppo di gametofiti 7-nucleati bipolarizzati con oosfera di natura sporiale. Stabilisce inoltre che in Statice Limonium L. lo sviluppo del gametofito femminile avviene esclusivamente secondo il tipo Euphorbia dulcis, mentre in Armeria vulgaris W. var. maritima (Miller) Willd. esiste associazione dei due tipi di sviluppo Adoxa ed Euphorbia dulcis nel rapporto approssimativo del 3%. Mette in evidenza che la triploidia dei nuclei calazali, caratteristica dei gametofiti di tipo Euphorbia dulcis, può determinarsi secondo due distinte modalità : o per coalescenza dei tre fusi calazali durante la terza divisione dello sviluppo (Statice Limonium), o per un processo di vera e propria cariogamia dei tre nuclei sporiali quiescenti durante lo stadio di polarizzazione 1+3 con conscguente formazione durante la storia dello sviluppo di uno stadio binucleato secondario (Armeria vulgaris var. maritima). Riconferma infine per questa ultima pianta il numero aploide dei cromosomi n = 9. 相似文献
9.
The anabolic action of intermittent parathyroid hormone on cortical bone depends partly on its ability to induce nitric oxide‐mediated vasorelaxation in BALB/c mice
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S Gohin A Carriero C Chenu AA Pitsillides TR Arnett M Marenzana 《Cell biochemistry and function》2016,34(2):52-62
There is strong evidence that vasodilatory nitric oxide (NO) donors have anabolic effects on bone in humans. Parathyroid hormone (PTH), the only osteoanabolic drug currently approved, is also a vasodilator. We investigated whether the NO synthase inhibitor L‐NAME might alter the effect of PTH on bone by blocking its vasodilatory effect. BALB/c mice received 28 daily injections of PTH[1–34] (80 µg/kg/day) or L‐NAME (30 mg/kg/day), alone or in combination. Hindlimb blood perfusion was measured by laser Doppler imaging. Bone architecture, turnover and mechanical properties in the femur were analysed respectively by micro‐CT, histomorphometry and three‐point bending. PTH increased hindlimb blood flow by >30% within 10 min of injection (P < 0.001). Co‐treatment with L‐NAME blocked the action of PTH on blood flow, whereas L‐NAME alone had no effect. PTH treatment increased femoral cortical bone volume and formation rate by 20% and 110%, respectively (P < 0.001). PTH had no effect on trabecular bone volume in the femoral metaphysis although trabecular thickness and number were increased and decreased by 25%, respectively. Co‐treatment with L‐NAME restricted the PTH‐stimulated increase in cortical bone formation but had no clear‐cut effects in trabecular bone. Co‐treatment with L‐NAME did not affect the mechanical strength in femurs induced by iPTH. These results suggest that NO‐mediated vasorelaxation plays partly a role in the anabolic action of PTH on cortical bone. © 2016 The Authors. Cell Biochemistry and Function published by John Wiley & Sons, Ltd. 相似文献
10.