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791.
Summary
Hydra oligactis exposed to 3 g/ml actinomycin D for 24 hours regenerated only the first pair of tentacles (the mid-laterals). If left uncut, actinomycin D treated animals underwent a reduction of the normal number of tentacles to two or less.Inductive activity was retained in the 2-tentacled hypostomes. However, the tentacles present exhibited reduced capacities to capture and manipulate prey.Histological studies showed that the tentacles of actinomycin D treated hydra were morphologically identical to those of the controls. The interstitial cell (I-cell) population of the treated animals, however, became depleted. Replacing the hypostome of an actinomycin D treated hydra with a normal hypostome reversed the cellular effects of actinomycin D treatment.The modifications in tentacle morphogenesis occurring after actinomycin D treatment are consistent with an impairment of hypostomal function in the animal. It is suggested that the morphological site of this malfunction may be in the nervous system.Research supported by American Cancer Society Institutional Grant No. 342-9157, USPHS Institutional Grant No. 342-9241 and by a grant from Research Corporation.Part of this work was completed while L.H. was an undergraduate research student supported by the National Science Foundation. 相似文献
792.
The effect of Cu toxicity on photosynthetic function, chlorophyll and Ca2+ content of Cu-tolerant Silene compacta plants grown in nutrient solution was studied. Since, in plants grown under 8 μ M Cu, the chlorophyll and Ca2+ concentration as well as the photosystem II (PSII) photochemistry were increased, compared to the control, the development of an adaptive mechanism of the Cu-tolerant ecotype of S. compacta to 8 μ M Cu is suggested. Increased Cu tolerance of the S. compacta ecotype reflects modulation of the photosynthetic apparatus to optimize photosynthesis. However, exposure of plants to 160 μ M Cu resulted in a marked increase of the fraction of closed PSII centres and decreased quantum yield of PSII electron transport (ΦPSU ) which was accompanied by a significant decline of relative quantum yield for O2 evolution (Aox /Apt ). The concentration of chlorophyll and Ca2+ in leaves also decreased significantly under 160 μ M Cu treatment. Photochemical quenching (qp ) displayed a reduction as a result of perturbation of the photosynthetic electron transfer chain, while non-photochemical quenching (qN ) increased. High Cu treatment reduced photosynthetic productivity of S. compacta plants which can be attributed, in part, to pertubation of photosynthetic process and photosynthetic pigments as well as to Ca2+ loss. 相似文献
793.
G. Ouzounidou 《Biologia Plantarum》1995,37(1):71-78
The effects of Cu2+ on growth, chlorophyll and other ion contents ofKoeleria splendens originated from Cu-contaminated soil have been investigated in nutrient solution. The most evident Cu2+ effects concern the root growth, especially the root length. Since in plants grown under lower Cu2+ concentrations (4 and 8 μM) root elongation, biomass, chlorophyll, Mg2+, Fe2+, Ca2+ and K+ content were increased compared with the control, the development of an adaptive mechanism ofK. splendens to Cu2+ is suggested. High Cu2+ concentration (160 μM) caused a significant reduction in root length and biomass as well as a decreased rate of chlorophyll biosynthesis. The reduction of growth can be correlated with the toxic effect of Cu2+ on photosynthesis, root respiration and protein synthesis in roots. 160 μM Cu2+-treatment had a negative influence on the concentrations of Ca2+, Fe2+, Mg2+ and K+ and a positive influence on the Cu2+ concentration in the plant tissues. Loss of nutrients similar to the senescence response suggests that excess of Cu2+ leads to the progressive senescence of the plants. Our results demonstrate the existence of an adaptive mechanism ofK. splendens under low Cu2+ concentrations, while high Cu2+ quantities cause disturbances in plant function. 相似文献
794.
795.
Tentacles excised from syphistoma polyps of Aurelia aurita undergo rapid regeneration to form whole polyps following exposure to an excess or absence of specific ions. It has been shown that a 12–18 h exposure of isolated tentacles to 58 mM excess of Cs+ results in a rapid firing of nematocysts, followed by an accelerated, synchronous polyp morphogenesis. Absence of Mgt2+ from the culture solution for 4–24 h also led to an accelerated, synchronous polyp regeneration. In either experimental set-up, incubation in 5–10 mM hydroxyurea effectively halted regeneration. Exposure to an excess of Li+ (50–200 mm) or K+ (10–50 mM) caused no firing of nematocysts and a percentage of polyp regeneration only slightly higher than control tentacles. Use of the K+ channel blocker tetraethylammonium (TEA; 100–300 mM) lead to similar levels of regeneration. A Ca2+ or K+-reduced artificial culture solution did not enhance regeneration. Ouabain (1 mM) dampened the Cs+ induced acceleration of polyp morphogenesis, and when given without Cs+, elicited a control level response. 相似文献
796.
Georgia Varelogianni Igor Oliynyk Godfried M. Roomans Marie Johannesson 《Cell biology international》2010,34(3):245-252
Defective chloride transport in epithelial cells increases mucus viscosity and leads to recurrent infections with high oxidative stress in patients with CF (cystic fibrosis). NAC (N‐acetylcysteine) is a well known mucolytic and antioxidant drug, and an indirect precursor of glutathione. Since GSNO (S‐nitrosoglutathione) previously has been shown to be able to promote Cl? efflux from CF airway epithelial cells, it was investigated whether NAC also could stimulate Cl? efflux from CF and non‐CF epithelial cells and through which mechanisms. CFBE (CF bronchial epithelial cells) and normal bronchial epithelial cells (16HBE) were treated with 1 mM, 5 mM, 10 mM or 15 mM NAC for 4 h at 37°C. The effect of NAC on Cl? transport was measured by Cl? efflux measurements and by X‐ray microanalysis. Cl? efflux from CFBE cells was stimulated by NAC in a dose‐dependent manner, with 10 mM NAC causing a significant increase in Cl? efflux with nearly 80% in CFBE cells. The intracellular Cl? concentration in CFBE cells was significantly decreased up to 60% after 4 h treatment with 10 mM NAC. Moreover immunocytochemistry and Western blot experiments revealed expression of CFTR channel on CFBE cells after treatment with 10 mM NAC. The stimulation of Cl? efflux by NAC in CF airway epithelial cells may improve hydration of the mucus and thereby be beneficial for CF patients. 相似文献
797.
798.
Min Fang Robert J. Kremer Peter P. Motavalli Georgia Davis 《Applied microbiology》2005,71(7):4132-4136
Bacterial diversity in transgenic and nontransgenic corn rhizospheres was determined. In greenhouse and field studies, metabolic profiling and molecular analysis of 16S rRNAs differentiated bacterial communities among soil textures but not between corn varieties. We conclude that bacteria in corn rhizospheres are affected more by soil texture than by cultivation of transgenic varieties. 相似文献
799.
Human immunodeficiency virus type 1 gp41 antibodies that mask membrane proximal region epitopes: antibody binding kinetics, induction, and potential for regulation in acute infection 总被引:3,自引:1,他引:2
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Alam SM Scearce RM Parks RJ Plonk K Plonk SG Sutherland LL Gorny MK Zolla-Pazner S Vanleeuwen S Moody MA Xia SM Montefiori DC Tomaras GD Weinhold KJ Karim SA Hicks CB Liao HX Robinson J Shaw GM Haynes BF 《Journal of virology》2008,82(1):115-125
Two human monoclonal antibodies (MAbs) (2F5 and 4E10) against the human immunodeficiency virus type 1 (HIV-1) envelope g41 cluster II membrane proximal external region (MPER) broadly neutralize HIV-1 primary isolates. However, these antibody specificities are rare, are not induced by Env immunization or HIV-1 infection, and are polyspecific and also react with lipids such as cardiolipin or phosphatidylserine. To probe MPER anti-gp41 antibodies that are produced in HIV-1 infection, we have made two novel murine MAbs, 5A9 and 13H11, against HIV-1 gp41 envelope that partially cross-blocked 2F5 MAb binding to Env but did not neutralize HIV-1 primary isolates or bind host lipids. Competitive inhibition assays using labeled 13H11 MAb and HIV-1-positive patient plasma samples demonstrated that cluster II 13H11-blocking plasma antibodies were made in 83% of chronically HIV-1 infected patients and were acquired between 5 to 10 weeks after acute HIV-1 infection. Both the mouse 13H11 MAb and the three prototypic cluster II human MAbs (98-6, 126-6, and 167-D) blocked 2F5 binding to gp41 epitopes to variable degrees; the combination of 98-6 and 13H11 completely blocked 2F5 binding. These data provide support for the hypothesis that in some patients, B cells make nonneutralizing cluster II antibodies that may mask or otherwise down-modulate B-cell responses to immunogenic regions of gp41 that could be recognized by B cells capable of producing antibodies like 2F5. 相似文献
800.
Accelerated prion disease pathogenesis in Toll-like receptor 4 signaling-mutant mice 总被引:1,自引:0,他引:1
Spinner DS Cho IS Park SY Kim JI Meeker HC Ye X Lafauci G Kerr DJ Flory MJ Kim BS Kascsak RB Wisniewski T Levis WR Schuller-Levis GB Carp RI Park E Kascsak RJ 《Journal of virology》2008,82(21):10701-10708
Prion diseases such as scrapie involve the accumulation of disease-specific prion protein, PrP(Sc), in the brain. Toll-like receptors (TLRs) are a family of proteins that recognize microbial constituents and are central players in host innate immune responses. The TLR9 agonist unmethylated CpG DNA was shown to prolong the scrapie incubation period in mice, suggesting that innate immune activation interferes with prion disease progression. Thus, it was predicted that ablation of TLR signaling would result in accelerated pathogenesis. C3H/HeJ (Tlr4(Lps-d)) mice, which possess a mutation in the TLR4 intracellular domain preventing TLR4 signaling, and strain-matched wild-type control (C3H/HeOuJ) mice were infected intracerebrally or intraperitoneally with various doses of scrapie inoculum. Incubation periods were significantly shortened in C3H/HeJ compared with C3H/HeOuJ mice, regardless of the route of infection or dose administered. At the clinical phase of disease, brain PrP(Sc) levels in the two strains of mice showed no significant differences by Western blotting. In addition, compared with macrophages from C3H/HeOuJ mice, those from C3H/HeJ mice were unresponsive to fibrillogenic PrP peptides (PrP residues 106 to 126 [PrP(106-126)] and PrP(118-135)) and the TLR4 agonist lipopolysaccharide but not to the TLR2 agonist zymosan, as measured by cytokine production. These data confirm that innate immune activation via TLR signaling interferes with scrapie infection. Furthermore, the results also suggest that the scrapie pathogen, or a component(s) thereof, is capable of stimulating an innate immune response that is active in the central nervous system, since C3H/HeJ mice, which lack the response, exhibit shortened incubation periods following both intraperitoneal and intracerebral infections. 相似文献