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971.
Amie Laycock Edith Camm Sherah Van Laerhoven Dave Gillespie 《Journal of Insect Behavior》2006,19(2):219-229
Cannibalism is a dietary option, the frequency of which, in most predator-prey systems, is inversely proportional to the abundance of primary prey. Under conditions of prey scarcity, in food webs involving plant-feeding omnivores, cannibals may choose to feed on either conspecifics or on the continuously-available but less nourishing plant substrate. We tested the effects of prey limitation and plant species on cannibalism in the omnivorous true bug, Dicyphus hesperus. Adult females preyed on first- and fourth-instar, and male conspecifics, and the rate of cannibalism increased under conditions of prey scarcity. Plant species affected cannibalism, with the highest cannibalism occurring on mullein, Verbascum thapsus and chrysanthemum, Chrysanthemum coronarium, and the lowest on tomato, Lycopersicon esculentum. Removal of leaf hairs from mullein reduced the rate of cannibalism. Host plant species affects the rates of cannibalism in D. hesperus and mechanisms other than the plant's value as food may contribute to this effect. 相似文献
972.
Hofinger ES Hoechstetter J Oettl M Bernhardt G Buschauer A 《Glycoconjugate journal》2008,25(2):101-109
Bovine testicular hyaluronidase (BTH) has been used as a spreading factor for many years and was primarily characterized by
its enzymatic activity. As recombinant human hyaluronidases are now available the bovine preparations can be replaced by the
human enzymes. However, data on the pH-dependent activity of hyaluronidases reported in literature are inconsistent in part
or even contradictory. Detection of the pH-dependent activity of PH-20 type hyaluronidases, i.e. recombinant human PH-20 (rhPH-20) and BTH, showed a shift of the pH optimum from acidic pH values in a colorimetric activity
assay to higher pH values in a turbidimetric activity assay. Contrarily, recombinant human Hyal-1 (rhHyal-1) and bee venom
hyaluronidase (BVH) exhibited nearly identical pH profiles in both commonly used types of activity assays. Analysis of the
hyaluronic acid (HA) degradation products by capillary zone electrophoresis showed that hyaluronan was catabolized by rhHyal-1
continuously into HA oligosaccharides. BTH and, to a less extent, rhPH-20 exhibited a different mode of action: at acidic
pH (pH 4.5) HA was degraded as described for rhHyal-1, while at elevated pH (pH 5.5) small oligosaccharides were produced
in addition to HA fragments of medium molecular weight, thus explaining the pH-dependent discrepancies in the activity assays.
Our results suggest a sub-classification of mammalian-type hyaluronidases into a PH-20/BTH and a Hyal-1/BVH subtype. As the
biological effects of HA fragments are reported to depend on the size of the molecules it can be speculated that different
pH values at the site of hyaluronan degradation may result in different biological responses. 相似文献
973.
974.
975.
Kana BD Gordhan BG Downing KJ Sung N Vostroktunova G Machowski EE Tsenova L Young M Kaprelyants A Kaplan G Mizrahi V 《Molecular microbiology》2008,67(3):672-684
Mycobacterium tuberculosis contains five resuscitation-promoting factor (Rpf)-like proteins, RpfA-E, that are implicated in resuscitation of this organism from dormancy via a mechanism involving hydrolysis of the peptidoglycan by Rpfs and partnering proteins. In this study, the rpfA-E genes were shown to be collectively dispensable for growth of M. tuberculosis in broth culture. The defect in resuscitation of multiple mutants from a 'non-culturable' state induced by starvation under anoxia was reversed by genetic complementation or addition of culture filtrate from wild-type organisms confirming that the phenotype was associated with rpf-like gene loss and that the 'non-culturable' cells of the mutant strains were viable. Other phenotypes uncovered by sequential deletion mutagenesis revealed a functional differentiation within this protein family. The quintuple mutant and its parent that retained only rpfD displayed delayed colony formation and hypersensitivity to detergent, effects not observed for mutants retaining only rpfE or rpfB. Furthermore, mutants retaining rpfD or rpfE were highly attenuated for growth in mice with the latter persisting better than the former in late-stage infection. In conjunction, these results are indicative of a hierarchy in terms of function and/or potency with the Rpf family, with RpfB and RpfE ranking above RpfD. 相似文献
976.
Wilkinson BL Long H Sim E Fairbanks AJ 《Bioorganic & medicinal chemistry letters》2008,18(23):6265-6267
A series of arabino glycosyl triazoles with varying hydrophobic groups were synthesised as putative mimics of decaprenolphosphoarabinose (DPA) as potential inhibitors of mycobacterial cell wall biosynthesis. Biological testing against Mycobacterium bovis BCG revealed low to moderate anti-mycobacterial activity, with strong dependence on the identity of the hydrophobic side chain. 相似文献
977.
Szafer-Glusman E Giansanti MG Nishihama R Bolival B Pringle J Gatti M Fuller MT 《Current biology : CB》2008,18(18):1426-1431
Cell shape and membrane remodeling rely on regulated interactions between the lipid bilayer and cytoskeletal arrays at the cell cortex. During cytokinesis, animal cells build an actomyosin ring anchored to the plasma membrane at the equatorial cortex. Ring constriction coupled to plasma-membrane ingression separates the two daughter cells. Plasma-membrane lipids influence membrane biophysical properties such as membrane curvature and elasticity and play an active role in cell function, and specialized membrane domains are emerging as important factors in regulating assembly and rearrangement of the cytoskeleton. Here, we show that mutations in the gene bond, which encodes a Drosophila member of the family of Elovl proteins that mediate elongation of very-long-chain fatty acids, block or dramatically slow cleavage-furrow ingression during early telophase in dividing spermatocytes. In bond mutant cells at late stages of division, the contractile ring frequently detaches from the cortex and constricts or collapses to one side of the cell, and the cleavage furrow regresses. Our findings implicate very-long-chain fatty acids or their derivative complex lipids in allowing supple membrane deformation and the stable connection of cortical contractile components to the plasma membrane during cell division. 相似文献
978.
Francisco Carvallo-Chaigneau Cristina Trejo-Solís Celedonio Gómez-Ruiz Ernesto Rodríguez-Aguilera Lucía Macías-Rosales Edith Cortés-Barberena Carlos Cedillo-Peláez Isabel Gracia-Mora Lena Ruiz-Azuara Vicente Madrid-Marina Fernando Constantino-Casas 《Biometals》2008,21(1):17-28
The aim of this study was to evaluate the in vitro and in vivo effects of the new chemotherapy agent Casiopeina III-ia [(4,4′-dimethyl-2,2′-bipiridine)(acetylacetonate)
Copper (II) nitrate] on HCT-15 (p53–/-) colon cellular line. In vitro, the drug reduced the viability and induced necrosis
and apoptosis in a dose dependent manner, without affecting cell cycle phases. Apoptosis was related to Bax increasing levels,
suggesting a caspase-dependent mechanism of death, as verified by nucleosomal fragmentation of DNA. In vivo, the antitumor activity of Casiopeina III-ia was tested in HCT-15
cells transplanted to nude mice. In this study we will show that the novel antineoplastic agent Casiopeina III-ia is active
on this colon tumor line, setting out as a good candidate for the treatment of colon tumors refractory to chemotherapy.
Lena Ruiz-Azuara - Previously as Lena Ruiz-Ramirez. 相似文献
979.
Expression of the rabies virus nucleoprotein in plants at high-levels and evaluation of immune responses in mice 总被引:1,自引:0,他引:1
Perea Arango I Loza Rubio E Rojas Anaya E Olivera Flores T Gonzalez de la Vara L Gómez Lim MA 《Plant cell reports》2008,27(4):677-685
Transgenic plants have been employed successfully as a low-cost system for the production of therapeutically valuable proteins
including antibodies, antigens and hormones. Here, we report expression of a full-length nucleoprotein gene of rabies virus
in transgenic tomato plants. The nucleoprotein was also transiently expressed in Nicotiana benthamiana plants by agroinfiltration. In both cases, the nucleoprotein was expressed at high levels, 1–5% of total soluble protein
in tomato and 45% in N. benthamiana. Previously, only epitopes of the nucleoprotein had been expressed in plants. The presence and expression of the transgene
was verified by PCR, Southern, northern and western blots. Mice were immunized both intraperitoneally (i.p.) and orally with
tomato protein extracts containing the N protein induced the production of antibodies. The antibody titer of mice immunized
i.p., was at least four times higher than that of mice immunized orally. These results were reflected in the challenge experiments
where i.p.-immunized mice were partially protected against a peripheral virus challenge whereas orally immunized mice were
not. This protection was comparable to that obtained in previous experiments employing different expression systems. Work
is in progress to express both G and N proteins in transgenic plants and evaluate protection in mice. 相似文献
980.
The proliferation and migration of Retinal Pigment Epithelium cells resulting from an epithelial-mesenchymal transition plays a key role in proliferative vitreoretinopathy, which leads to retinal detachment and the loss of vision. In neurons, glutamate has been shown to activate the Ras/Raf/MEK/ERK cascade, which participates in the regulation of proliferation, differentiation, and survival processes. Although glutamate-stimulation and the activation of ERK1/2 by different stimuli have been shown to promote RPE cell proliferation, the signaling pathway(s) linking these effects has not been established. We analyzed the molecular mechanisms leading to glutamate-induced proliferation by determining ERK1/2 and CREB phoshporylation in chick RPE cells in primary culture and the human-derived RPE cell line ARPE-19. This study shows for the first time, that glutamate promotes RPE cell proliferation by activating two distinct signaling pathways linked to selective glutamate receptor subtypes. Results demonstrate that glutamate stimulates RPE cell proliferation as well as ERK and CREB phosphorylation. These effects were mimicked by the mGluR agonist ACPD and by NMDA, and were prevented by the respective receptor inhibitors MCPG and MK-801, indicating a cause-effect relationship between these processes. Whereas mGluR promoted proliferation by activating the MEK/ERK/CREB cascade, NMDA stimulated proliferation through the MEK-independent activation of Ca(2+)/calmodulin-dependent kinases. The blockage of both signaling pathways to proliferation by KN-62 suggests the involvement of CaMKs in the control of glutamate-induced proliferation at a common step, downstream of CREB, possibly the regulation of cell cycle progression. Based on these findings, the participation of glutamate in the development of PVR can be considered. 相似文献