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1.
2.
A large number of low molecular weight polar cryoprotective agents have recently been found to induce erythroid differentiation of Friend leukemic cells in vitro. The effect of these agents on membrane fluidity in phospholipid vesicles was studied by determining the solid-to-liquid crystalline phase transition using differential scanning calorimetry. Some of the inducing agents studies were found to raise the normal transition temperature ( by a few degrees. All of these agents were found to produce a separate transition at a much higher temperature. Changes in the head group of the phospholipid, the pH, the presence of divalent cations, and the addition of other membrane-active compounds were found to significantly influence the inducing agent's effects on the of phospholipid membranes.The ability of the different agents to produce a new transition at a high temperature was found to correlate well with their ability to incude Friend leukemic cell differentiation. The possible mechanisms of action of the chemical inducers, and the significance of the observed membrane effects on differentiation and malignancy are discussed. It is concluded that inducing agents decrease the fluidity and stabilize phospholipid membranes, and that their effects in cell differentiation might be initiated by a similar change in the properties of cell membranes. 相似文献
3.
Immunoperoxidase detection of myeloid antigens in glycolmethacrylate-embedded human bone marrow 总被引:2,自引:0,他引:2
E Archimbaud A Islam H D Preisler 《The journal of histochemistry and cytochemistry》1987,35(5):595-599
Different methods for fixation and exposure of antigenic determinants were tested for detection of a granulocytic differentiation antigen by the monoclonal antibody L12-2, using an indirect immunoperoxidase method on semi-thin sections of undecalcified, glycolmethacrylate-embedded human bone marrow biopsies. Fixation in Bouin's solution for 3 hr gave a more intense and more homogeneous immunological staining than fixation in absolute methanol, 4% formalin, B5, or Michel's medium, and the morphological detail was excellent. Digestion by pronase or trypsin was required. Coating the glass slides with Alcian blue prevented loss of sections from the slides during the staining procedure. Bouin fixation also made possible detection of two other differentiation antigens expressed in the granulocytic series, using the monoclonal antibodies 1G10 and R1B19. Furthermore, the same technique also permitted detection of factor VIII-RAg in the megakaryocytes, as well as recognition of cells of the erythroid series by use of polyclonal rabbit antisera. 相似文献
4.
Volker Nicolai 《Oecologia》1991,88(1):132-137
Summary The arthropod communities living on the bark of the oak species Quercus macrocarpa and Q. ellipsoidalis were investigated in a North American oak savanna. Differences were found in the community structure of the arthropods living on the bark of these two tree species, although they have the same fissured bark type. In the North American oak savanna ecosystem the most important disturbance factor is fire, which maintains species richness. Highest numbers of species and specimens were found at moderately disturbed sites. Three main ecological groups of arthropods living on the bark of trees can be distinguished in relation to the degree of disturbance: (1) Inhabitants of bark of trees restricted to undisturbed sites: they do not occur in fire-disturbed areas; (2) Inhabitants of bark of trees adapted to a moderate degree of disturbance: many species occur in high numbers only in moderately disturbed areas; and (3) Specialist inhabitants of bark of trees in heavily disturbed areas. The number of specimens of these species increases per trunk with the frequency of disturbance. 相似文献
5.
Summary In the species studied song appears to have two functions; an epigamic function = Display Song, and a contact function = Solitary Song. Solitary Song appears to be common to all the species studied. Its utterance indicates that the bird is unpaired or separated from another individual with which it has formed a bond. InUraeginthus bengalus, U. angolensis, andAmandava amandava Solitary Song is also uttered by the hen in similar circumstances. InLonchura punctulata, A. amandava, andEuodice malabarica song is usually but not completely inhibited by the presence of a mate, in whose absence Solitary Song will be uttered even when other individuals of the same species are present. In the species studied of the generaEstrilda, Lagonosticta, andUraeginthus Solitary Song is inhibited by the continued close proximity of another bird even though this may be of the same sex or of a different species and may elicit aggressive or fleeing reactions; but conditions of close association with a bird other than a suitable mate would presumably only occur under captive conditions. There appears to be a distance factor controlling such inhibition. There is evidence of the inhibition of song due to the presence of a mate in other passerine species. 相似文献
6.
Jürgen Nicolai 《Journal of Ornithology》1959,100(1):39-46
Zusammenfassung Der heranwachsende Junggimpel empfängt während seiner Nestlingszeit und den sich anschließenden Wochen bis zum Erlangen der Selbständigkeit von den Eltern Eindrücke, die sein späteres Geschlechtsverhalten und seine stimmliche Entwicklung entscheidend beeinflussen. Ein normales Geschlechtsverhalten entwickelt sich nur dann, wenn der Jungvogel von den eigenen Eltern oder Artgenossen aufgezogen wird. Erfolgt die Aufzucht durch andere Lebewesen (Kanarienvogel, Mensch), so tritt eine mehr oder weniger deutliche Prägung der sozialen und sexuellen Reaktion auf diese Arten ein. Mit dieser Prägung geht eine Fixation der Lautäußerungen (Lockruf, Gesang) an die der Eltern — vor allem des Vaters — Hand in Hand. Trägt der Vater normale Lockrufe und den arttypischen Gesang vor, so erfährt auch der Junggimpel eine ormale stimmliche Entwicklung. Sind aber Lockrufe und Gesang in Klangfarbe und Komposition abweichend, so lernt der Jungvogel selektiv alle diese Abweichungen und behält sie zeitlebens bei. Ein Jungmännchen, das von Kanarien aufgezogen wurde, erlernte unter einer Schar anderer Junggimpel den Gesang des einzigen anwesenden Kanarienmännchens und gab ihn an seine Söhne weiter. Vier Jahre später sangen die Urenkel dieses Vogels noch die Kanarienstrophen in unveränderter Form. — Von Menschen aufgezogene Gimpel konzentrieren ihren Lerneifer auf die Lautäußerungen des Pflegers; sie erlernen vorgepfiffene Melodien: bis zu drei kurze Volkslieder. Während die jungen Männchen ausschließlich dem Gesang des Vaters ihre Aufmerksamkeit zuwenden, nehmen die Weibchen nach ihrer Verpaarung neben den vom Vater erlernten Motiven auch solche aus dem Gesang des Gatten auf. Nur der erste Partner hat auf ihre Gesanganusbildung Einfluß.Die sensible Periode der stimmlichen Entwicklung fällt mit der Zeit zusammen, in der frühsexuelle Stimmungen den Junggimpel beherrschen. Sein Lerneifer ist auf dasjenige Lebewesen konzentriert, das ihn aufzog und dem er — aus dem daraus erwachsenen hohen Grade persönlicher Bindung heraus — seine ersten sexuellen Anträge machte. 相似文献
7.
A somatic cell hybrid map of the long arm of human chromosome 17, containing the familial breast cancer locus (BRCA1). 总被引:6,自引:6,他引:0
We describe a detailed somatic cell hybrid map of human chromosome 17q11.2-q23, containing the familial breast and ovarian cancer locus (BRCA1) and highly informative closely linked markers. An X-irradiation panel of 38 hamster/human and mouse/human hybrids with fragments of chromosome 17 was generated and characterized with 22 STS markers from this chromosome. A detailed map of 61 probes onto chromosome 17q, subdividing the chromosome arm into 25 regions, was done by using a panel of hybrids with well-defined breakpoints and nine chromosome-mediated gene transfectants. Our localization of RARA, TOP2, EDH17B1 and 2, and possibly WNT3, between THRA1 and D17S181, two markers known to flank BRCA1, suggests that any of these is a potential candidate for the BRCA1 locus. The marker D17S579 (Mfd188), which is believed to be very close to BRCA1, maps closest to the EDH17B genes. 相似文献
8.
Zhuqing Mao Nicolai Müller Sabrina Borusak David Schleheck Bernhard Schink 《Environmental microbiology》2023,25(11):2068-2074
Phosphite is a stable phosphorus compound that, together with phosphate, made up a substantial part of the total phosphorus content of the prebiotic Earth's crust. Oxidation of phosphite to phosphate releases electrons at an unusually low redox potential (−690 mV at pH 7.0). Numerous aerobic and anaerobic bacteria use phosphite as a phosphorus source and oxidise it to phosphate for synthesis of nucleotides and other phosphorus-containing cell constituents. Only two pure cultures of strictly anaerobic bacteria have been isolated so far that use phosphite as an electron donor in their energy metabolism, the Gram-positive Phosphitispora fastidiosa and the Gram-negative Desulfotignum phosphitoxidans. The key enzyme of this metabolism is an NAD+-dependent phosphite dehydrogenase enzyme that phosphorylates AMP to ADP. These phosphorylating phosphite dehydrogenases were found to be related to nucleoside diphosphate sugar epimerases. The produced NADH is channelled into autotrophic CO2 fixation via the Wood-Ljungdahl (CO-DH) pathway, thus allowing for nearly complete assimilation of the substrate electrons into bacterial biomass. This extremely efficient type of electron flow connects energy and carbon metabolism directly through NADH and might have been important in the early evolution of life when phosphite was easily available on Earth. 相似文献
9.
Sven Erik Godtfredsen Anne Munk Rasmussen Martin Ottesen Peer Rafn Nicolai Peitersen 《Applied microbiology and biotechnology》1984,20(1):23-28
Summary Acetolactate decarboxylase activity has been detected among three genera, nine species and 263 strains of lactic acid bacteria tested in the course of a screening for acetolactate decarboxylases amenable for use in brewing as maturation aid. Streptococcus diacetylactis strain FD-64-D was found to generate a decarboxylase exhibiting a satisfactory activity and an excellent stability at the pH prevailing in beer and wort. This decarboxylase could not be solubilized but enzymatically active, freeze-dried cells were effective for satisfactory flavour maturation of beer although difficulties were encountered during attempts to remove the applied cell material by filtration of the beer. Lactobacillus casei DSM 2547 was likewise found to produce a decarboxylase exhibiting a satisfactory activity and stability at the low pH of beer and which, in addition, was readily solubilized. A method has been developed for pilot scale production of preparations of this decarboxylase suitable for use in brewing.Abbreviations DSM
Deutsche Sammlung von Microorganismen
- EDTA
Ethylene diaminetetra-acetic acid 相似文献
10.
The extraordinary sensitivity of early erythroid progenitor cells (BFU-e) of normal human bone marrow to tritiated thymidine ([3H]TdR) was studied. While exposure of bone-marrow cells to [3H]TdR for 1 hr resulted in the death of only 40% of the granulocyte-macrophage progenitor cells (CFU-c), 90% of BFU-e were killed. Experiments in which normal bone-marrow cells were mixed with bone-marrow cells which had been exposed to [3H]TdR demonstrated that the excessive killing of BFU-e by [3H]TdR reflected carry-over of the [3H]TdR by the exposed cells. A carry-over effect was not observed for CFU-c, suggesting the presence of a fundamental difference in the metabolism of TdR between CFU-c and BFU-e. There was a suggestion of a carry-over effect regarding two other S-phase-specific agents, hydroxyurea and 1-β-D-arabinofuranosylcytosine. 相似文献