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Mammalian carbamyl phosphate synthetase (CPS). DNA sequence and evolution of the CPS domain of the Syrian hamster multifunctional protein CAD 总被引:2,自引:0,他引:2
J P Simmer R E Kelly A G Rinker J L Scully D R Evans 《The Journal of biological chemistry》1990,265(18):10395-10402
Glutamine-dependent carbamoyl-phosphate synthetase (EC 6.3.5.5) catalyzes the first step in de novo pyrimidine biosynthesis. The mammalian enzyme is part of a 240-kDa multifunctional protein which also has the second (aspartate carbamoyltransferase, EC 2.1.3.2), and third (dihydroorotase, EC 3.5.2.3) activities of the pathway. Shigesada et al. (Shigesada, K., Stark, G.R., Maley, J.A., and Davidson, J.N. (1985) Mol. Cell Biol. 175, 1-7) produced a truncated cDNA clone from a Syrian hamster cell line that contained most of the coding region for this protein. We have completed sequencing this clone, known as pCAD142. The cDNA insert contained all of the coding region for the glutaminase (GLN) and carbamyl phosphate synthetase (CPS) domains but lacked a short amino-terminal segment. By comparing the primary structure of the mammalian chimera to monofunctional proteins we have identified the borders of the functional domains. The GLN domain is 21 kDa, close to the size of the functionally similar polypeptide products of the Escherichia coli pabA and hisH genes. The domain has the three regions of homology common to trpG-type glutamine amidotransferases, as well as a fourth region specific to the carbamyl phosphate synthetases. The CPSase domain is similar to other reported CPSases in size (120 kDa), primary structure (37-67% amino acid identity), and homology between its amino and carboxyl halves. Analysis of the nucleotide and amino acid sequence identities among the various carbamyl phosphate synthetases suggests that the gene fusion which joined the GLN and CPS domains was an early event in the evolution of eukaryotic organisms and that the Saccharomyces cerevisiae enzyme consisting of separate subunits arose by defusion from an ancestral multifunctional protein. 相似文献
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Host compatibility of different spore-positive (Sp+)and spore-negative (Sp?) strain types of Frankia from alder stands in Finland was studied in Modulation tests with hydrocultures of Alnus glutinosa (L.) Gaertner, A. incana (L.) Moench and A. nitida Endl. Root nodules and soil samples from stands of A. incana (Lammi forest and Hämeenlinna forest) were dominated by Sp + types of Frankia (coded AiSp+ and AiSp+ H. respectively), which caused effective root nodules in test plants of A. incana, but failed to induce nodules in A. nitida. In A. glutinosa Frankia strain types AiSp + and AiSp + H caused small, ineffective root nodules with sporangia (coded Ineff ?), which were recognized by the absence or near absence of vesicles in the nodule tissue. Ineffective nodules without sporangia (coded Ineff ?) were induced on A. glutinosa with soil samples collected at Lammi swamp. The spore-negative strain type of Frankia was common in root nodules of A. glutinosa in Finland (Lammi swamp) and caused effective Sp? type root nodules (coded AgSp ?) in hydrocultures of A. incana, A. glutinosa and A. nitida. A different Sp + strain type of Frankia. coded AgSp+ Finland, was occasionally found in stands of A. glutinosa. It was clearly distinguished from strain type AiSp + by the ability to produce effective nodules on both A. glutinosa and A. incana. The nodulation capacities of soil and nodule samples were calculated from the nodulation response in hydrocutlure and served as a measure for the population density of infective Frankia particles. Sp + nodules from both strain types had equal and high nodulation capacities with compatible host species. The nodulation capacities of Sp type root nodules from A. glutinosa were consistently low. High frequencies of Frankia AiSp+ and AiSp+ H were found in the soil environment of dominant AiSp + nodule populations on A. incana. The numbers of infective particles of this strain type were insignificant in the soil environment of nearby Sp ? nodule populations on A. glutinosa and in the former field at Hämeen-linna near the Sp+ nodule area in Hämeenlinna forest. Strain type AgSp? had low undulation capacity in the soil environment of both A. incana and A. glutinosa stands, Explanations for the strong associations between Frankia strain types AiSp+ and AiSp ? H and A. incana and between strain type AgSp? and A. glutinosa are discussed in the light of host specificity and of some characteristics of population dynamics of both strain types. The possible need to adapt the concept of Frankia strain types Sp + and Sp ? to strains with some variation in spore development was stressed by the low potentials of strain type AiSp + H to develop spores in symbioses with hydrocultures of A. incnna. 相似文献
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J. Moradian-Oldak J. P. Simmer E. C. Lau P. E. Sarte H. C. Slavkin A. G. Fincham 《Biopolymers》1994,34(10):1339-1347
Recombinant murine amelogenins M179 and M166 were expressed in Escherichia coli and purified. The aggregation properties of these amelogenins have been investigated in aqueous solutions as well as acetonitrile-containing solutions using dynamic light scattering. Dynamic light scattering provides direct measurement of the translational diffusion coefficient and hydrodynamic radius, and of an estimate of the molecular weight. Polydispersity and statistical parameters of how to interpret the analysis are also provided. Amelogenin aggregation was examined in solutions of a range of pH, ionic strengths, and protein concentrations. It was shown that at pH 7.8–8 and ionic strength of 0.02–0.05M the M179 molecules form monodispersed aggregates with hydrodynamic radii ranging from 15 to 19 nm. Analysis of hydrodynamic radii and size distribution of M179 aggregates in acetonitrile-containing solvents compared to that in aqueous solutions indicated a primary role for hydrophobic interactions in the association process of amelogenin molecules to form aggregates. Comparison between the aggregates formed by M179 and M166, which lacks the hydrophilic carboxy-terminal 13 residue sequence of M179, suggested that the self-assembly of amelogenin molecules to form stable and monodisperse aggregates requires the presence of the hydrophilic carboxy-terminal sequence of M179. © 1994 John Wiley & Sons, Inc. 相似文献
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This report identifies a component of normal human fibroblasts that forms a covalent linkage with thrombin and urokinase (urinary plasminogen activator) and mediates most of the specific cellular binding of these proteases. This component, here named protease-nexin (PN), is both associated with the cell surface and released into the culture medium. In several ways PN resembles antithrombin III (AT3), a prominent inhibitor of thrombin in serum: PN links thrombin, probably via an ester bond; PN does not link thrombin blocked at its catalytic site serine; PN has a high-affinity heparin-binding site; and heparin greatly accelerates the rate of linkage between soluble PN and thrombin. Despite these similarities, PN and AT3 are distinct; they differ in size and are not immunologically cross-reactive. Whereas AT3 regulates the proteolytic activity of thrombin in serum, PN may regulate the activity of serine proteases at and near the cell surface. 相似文献
7.
Addition of insulin to nonproliferating serum-free cultures of secondary chicken embryo (CE) cells caused a 30% to 50% increase in cell number. Addition of any one of several glucocorticoids (dexamethasone, cortisol, or corticosterone) to the cultures two days before insulin addition increased the mitogenic effect of insulin by about twofold at each insulin concentration tested. This glucocorticoid stimulation of cell proliferation was “permissive” because in the absence of insulin glucocorticoids caused little increase in cell number (usually less than 15%). Glucocorticoids were maximally active at low concentrations (e.g., 10?10 M dexamethasone). Steroids without glucocorticoid activity were inactive over a wide range of concentrations. Glucocorticoids increased the mitogenic response to insulin largely by increasing the percentage of cells that insulin stimulated to synthesize DNA. The maximum mitogenic effect of insulin upon CE cells rapidly decreased after the cells were serially subcultured. After only nine population doublings (4 passages) in culture, the response to insulin was diminished by about 70%. The mitogenic effect of insulin plus dexamethasone declined similarly during serial subculture, and was always about twofold greater than the effect of insulin alone. The cells maintained their mitogenic responsiveness to serum as these responses decreased. In contrast to the growth promoting influence of glucocorticoids in the presence of insulin, glucocorticoids inhibited the mitogenic response of CE cells to serum. This result may resolve our above findings with reports that glucocorticoids inhibit the proliferation of CE cells. 相似文献
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Lobopodians, a paraphyletic group of rare but morphologically diverse Palaeozoic vermiform animals bearing metameric appendages, are key to the origin of extant panarthropods. First discovered in 1983 on Mount Stephen (Yoho National Park, British Columbia), the Cambrian (Wuliuan) Burgess Shale lobopodian nicknamed ‘Collins’ monster’ is formally described as Collinsovermis monstruosus gen. et sp. nov. A formal systematic treatment of the comparable and poorly known lobopodian Acinocricus stichus from Utah is also provided. The body of Collinsovermis is plump and compact but shows the diagnostic suspension-feeding characters of luolishaniid lobopodians. It possesses 14 contiguous pairs of lobopods, lacking space between them. The 6 anterior pairs are elongate, adorned with about 20 pairs of long and slightly curved ventral spinules arranged in a chevron-like pattern. These appendages terminate in a pair of thin claws and their dorsal surfaces are covered in minute spines or setae. The 8 posterior lobopod pairs, which attach to a truncated body termination, are stout and smooth, each terminated by a single strong recurved claw. Each somite bears a pair of dorsal spines; somites 4 and posteriad bear an additional median spine. The spines on somites 1–3 are much shorter than the spines on the remaining somites. The head is short, bears a terminal mouth and a pair of antenniform outgrowths, and is covered by an oblong sclerite. Collinsovermis, plus Collinsium and Acinocricus, are found to comprise a sub-group of stout luolishaniid lobopodians with remarkably long spinules on the front lobopods, interpreted here as a clade (Teratopodidae fam. nov.) This clade is distinct from both the comparatively slenderer Luolishania and a sub-group composed of Facivermis and Ovatiovermis lacking body sclerites. Luolishaniids were mostly sessile forerunners of arthropods that had coupled efficient suspension-feeding devices and, as in Collinsovermis, strong defensive or deterrent features. 相似文献