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151.
H. Iwatsuki Kazunobu Sasaki Masumi Suda Chikako Itano 《Histochemistry and cell biology》1997,107(6):459-468
To clarify the origin of the central cells in hepatic erythroblastic islands, glycoconjugates on the surface of cellular
constituents in fetal mice liver were ultrahistochemically examined using lectin staining. At 11 days of gestation, the cells
derived from mesenchyme in fetal liver, including sinusoidal macrophages, endothelial cells, and erythropoietic cells, bound
Griffonia simplicifolia isoagglutinin I-B4 (GS-I-B4), but hepatocytes lacked binding sites for the isolectin. Scavenger macrophages in the hepatic
cords at 13 days of gestation and the central cells in the erythroblastic islands at 15 days of gestation also bound GS-I-B4.
Hepatocytes, however, exhibited no GS-I-B4 binding site at any gestational day. At 11 days of gestation, none of the cells
in fetal liver had binding sites for soybean agglutinin (SBA), but cells derived from mesenchyme acquired these binding sites
at 13 days of gestation. The central cells in the erythroblastic islands also bound SBA, but hepatocytes did not bind the
lectin at all. The central cells in the erythroblastic islands can be considered to belong to a mesenchymal cell lineage,
and primitive sinusoidal macrophages at 11 days of gestation are possible precursors of these central cells.
Accepted: 22 January 1997 相似文献
152.
Mixed Valence Tin Oxides as Novel van der Waals Materials: Theoretical Predictions and Potential Applications
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Van der Waals (vdW) heterostructures, which can be assembled by combining 2D atomic crystals in a precisely chosen sequence, enable a wide range of potential applications in optoelectronics, photovoltaics, and photocatalysis. However, the difficulty of peeling isolated atomic planes and the lattice mismatch between different materials is the main obstacle to hinder vdW materials from more practical applications. In this work, the mixed valence tin oxides, SnxOy (0.5 < x/y < 1), are proposed as a new member of vdW materials and these mixed valence tin oxides show promise to overcome the above‐mentioned obstacle. Density‐functional theory calculations are combined with an evolutionary algorithm to predict the crystal structures of a series of previously reported tin oxides (Sn2O3, Sn3O4, Sn4O5, and Sn5O6), unreported compositions (Sn7O8, Sn9O10, and Sn11O12), and a new β ‐ SnO phase. These structures consist of β‐SnO, Sn2O3, and Sn3O4 monolayers. Their band gaps can be engineered in the 1.56–3.25 eV range by stacking the monolayers appropriately. The band gap depends linearly on the interlayer distance, as understood from interlayer Sn2+–Sn2+ and intralayer Sn2+–O interactions. SnxOy structures exhibit high photoabsorption coefficients and suitable band‐edge positions for photoexcited H2 evolution; this indicates potential for environmentally benign solar energy conversion in photovoltaic and photocatalytic applications. 相似文献
153.
154.
Summary
Bacillus subtilis C-756, a producer of cyclic adenosine 3,5-monophosphate (cAMP) phosphodiesterase inhibitor, was cultured in media adjusted to various water activity (aw) levels by addition of three different solutes, sodium chloride, ethylene glycol and polyethylene glycol 1540 (PEG).
B. subtilis C-756 can grow, however weakly, at aw levels of 0.94 and 0.93.The presence of all three solutes in the medium inhibited growth, cell mass as well as inhibitor production. PEG was found to be most inhibitory, but the effect can not be explained in terms of a decreased water activity in the medium. It is rather the increased viscosity of the medium, which results in a decreased oxygen transfer rate.Comparing ethylene glycol and sodium chloride, the presence of ethylene glycol appears to favour inhibitor production, whereas sodium chloride favours cell mass production. 相似文献
155.
Summary The brain of the Pacific hagfish, Eptatretus stouti, was studied immunocytochemically using antisera against somatostatin (SRIH), arginine vasopressin (AVP), and adrenocorticotropic hormone (ACTH). SRIH-immunoreactive perikarya were distributed bilaterally in the postoptic nucleus and in the hypothalamic nucleus. Although several short, stained fibers were observed in the vicinity of the perikarya, SRIH-immunoreactivity was not found in the neurohypophysis, nor in other parts of the brain. On the other hand, presumed arginine vasotocin (AVT) perikarya were distributed in an arc-shaped region extending from the posterior part of the preoptic nucleus to the anterior-most end of the hypothalamic nucleus and projected their fibers to the neurohypophysis. Most presumptive AVT perikarya were located close to the paired prehypophysial arteries near the anterior end of the postoptic nucleus. In the neurohypophysis, abundant presumptive AVT-fibers terminated in the posterior dorsal wall, although some fibers terminated in the anterior dorsal wall and only a few fiber endings were found in the ventral wall. No ACTH-positive cells were detected in the hagfish brain or in the pituitary gland.Supported from a grant from the National Science Foundation PCM 8141393 相似文献
156.
Summary Structural changes in drosopterinosomes (red pigment granules) of Rana japonica in the process of erythrophore differentiation were studied by light and electron microscopy. On the basis of the degree of pterinosome differentiation, three types can be recognized: Typ-I drosopterinosomes appear first during metamorphosis and have clear limiting membranes and amorphous materials within. Those of type-II are found in abundance shortly after metamorphosis and have inner structures, consisting of fibrillae and/or small lamellae in dense concentric arrangement. Type-III is found abundantly in adults and acquires an almost homogeneously electron-dense mature morphology, probably from the deposition of electron-dense materials. On the basis of counts of pterinosomes, a successive transformation from type I to III is suggested. The differences among red drosopterinosomes, yellow sepiapterinosomes in xanthophore and melanosomes are not always distinguishable electron microscopically. Discrimination is possible by careful examination of lamellar patterns characteristic of the respective granules and by a simultaneous application of light and electron microscopy. From this viewpoint, a re-evaluation of the identification of granules previously reported was effected.This work was supported by a grant in aid to T. H. from the Ministry of Education (No. 92112, 1971). 相似文献
157.
Summary ATP photophosphorylation by spinach thylakoid was examined to evaluate its use as an ATP regeneration reaction in biosynthetic reactors that consume ATP. Initial rate of cyclic photophosphorylation mediated by phenazine methosulfate was found to be 218 mole ATP/h.mg Chlorophyll. This activity was stable for over 3 months at –85°C. When phosphoryl transfer reactions were coupled to cyclic photophosphorylation, ATP was continuously regenerated by thylakoid between 14–24 times in batch reactors. 相似文献
158.
Distinctive effect of angiotensin II on prostaglandin production in dog renal and femoral arteries 总被引:2,自引:0,他引:2
The effect of angiotensin II (Ang II) on prostaglandin (PG) production in dog renal and femoral vasculature was examined in vivo and in vitro. In pentobarbital anesthetized dogs, the reduction of blood flow induced by intra-arterial infusion of Ang II was potentiated by pre-treatment with indomethacin (5 mg/kg) in the renal but not the femoral vasculature. Isolated renal and femoral arterial strips were incubated and the release of PGE2 and PGI2 (as 6-keto-PGF1 alpha) into the medium was measured by radioimmunoassay. Basal PGE2 and PGI2 production by renal and femoral arterial strips was approximately the same. PGI2 production was predominant for both strips. Ang II stimulated PG production in renal but not femoral arteries. In the renal artery, Ang II-induced PG production was inhibited by indomethacin (10(-6) M), mepacrine (10(-4) M) and saralasin (10(-6) M). These results suggest that Ang II stimulates PG production by the renal artery per se and the Ang II receptor is linked to phospholipase A2 in the renal but not the femoral artery. 相似文献
159.
The exchange rate constant between free Mg2+ and Mg2+ bound to adenosine 5′-triphosphate (ATP) was determined at various temperatures from the 31P-NMR spectra of ATP in the absence and presence of Mg2+. The activation free energy of this exchange reaction showed that Mg2+ binds asymmetrically to the β- and γ-phosphoryl groups and that it coordinates with the β-phosphoryl group more tightly than with the γ-phosphoryl group of ATP. On binding, Mg2+ becomes located closer to the β-phosphoryl group. This asymmetric location of Mg2+ weakens the chemical bond of the terminal bridged phosphoryl group, thus causing specific cleavage of this group. This mechanism was confirmed by an ab initio molecular orbital calculation, and by experiments on the stability of ATP in aqueous solution. 相似文献
160.
Long-term changes in Secchi disk transparency in Lake Nakaumi, Japan, from 1932 to the present, which includes the periods
before and after the loss of eelgrass (Zostera marina L.) beds, were compiled from previous reports. During the first (July 1932–February 1934) and the second (January 1949–November
1950) periods, the mean transparency was greater than 3 m at all observed stations. Data during the third period (July 1954–March
1956) are only available for the station at the center of the lake. The mean transparency during the third period was significantly
lower than that of the second period but higher than the mean during the fourth period. This observation suggests that the
decrease of transparency occurred during the third period. Because the decline of eelgrass beds in Lake Nakaumi occurred in
the mid-1950s, the decrease of transparency most likely resulted from the shift in primary producers from submerged macrophytes
to phytoplankton. Although the maximum transparency sometimes exceeded 3 m, mean transparencies during the fourth period (May
1975–December 2003) were less than 2 m at all stations, significantly lower than those during the first and second periods.
The shift in the chief primary producer, from benthic macrophytes to phytoplankton, caused a subsequent shift in secondary
producers. The opportunistic filter-feeding bivalve Musculista senhousia, regarded as a biofouling species of local fisheries, increased in Lake Nakaumi. The long-term monitoring data of transparency
suggested that restoration of submerged aquatic vegetation may be indispensable for the remediation of the lake environment
in this shallow eutrophic lagoon. 相似文献