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991.
Rocha-Granados Cdel M Sánchez-Hernández C Sánchez-Hernández C Martínez-Gallardo NA Ochoa-Alejo N Délano-Frier JP 《Planta》2005,222(5):794-810
Two hydroxyproline-rich glycopeptide systemin (TobHS) precursor proteins known as preproTobHypSys-A and B were recently discovered
in tobacco (Nicotiana tabacum L.) [Pearce et al. in Nature 411:817–820, 2001]. In this work, the effect of elicitors, insect damage, and abiotic stress on the expression of preproTobHypSys-A
ppTobHS-A) in tobacco plants was evaluated. Foliar application of methyl jasmonate preferentially induced the systemic expression of
ppTobHS-A in leaves phyllotactically one position above-treated leaves. Abscisic acid strongly induced ppTobHS-A, but water-stress did not. Mechanical wound-induction of ppTobHS-A in young plantlets was rapidly (1 h) and simultaneously detected in wounded and upper unwounded leaves, whereas in older
plants induction was slow (12 h) and localized. ppTobHS-A was induced in plants infested with Bemisia tabaci or damaged by herbivory with Manduca sexta larvae. Compared to mechanical wounding, larval herbivory induced a stronger and more stable expression of ppTobHS-A. Moreover, exposure to Manduca-damaged plants induced its expression in neighboring intact plants. In most treatments, the expression patterns of ppTobHS-A coincided with those of selected wound-responsive (WR) genes (e.g., PIOX, NtPI-I, TPI). This correlation was tighter in the wounded and MeJA-treated leaves, whereas in distal, undamaged leaves, it appeared to
depend on the type of WR gene examined and on the type of damage sustained by the plant. These results are consistent with
the perceived role of the TobHS in defense signaling. 相似文献
992.
PDGF activates K-Cl cotransport through phosphoinositide 3-kinase and protein phosphatase-1 in primary cultures of vascular smooth muscle cells 总被引:3,自引:0,他引:3
K-Cl cotransport (K-Cl COT, KCC) is an electroneutrally coupled movement of K and Cl present in most cells. In this work, we studied the pathways of regulation of K-Cl COT by platelet-derived growth factor (PDGF) in primary cultures of vascular smooth muscle cells (VSMCs). Wortmannin and LY 294002 blocked the PDGF-induced K-Cl COT activation, indicating that the phosphoinositide 3-kinase (PI 3-K) pathway is involved. However, PD 98059 had no effect on K-Cl COT activation by PDGF, suggesting that the mitogen-activated protein kinase pathway is not involved under the experimental conditions tested. Involvement of phosphatases was also examined. Sodium orthovanadate, cyclosporin A and okadaic acid had no effect on PDGF-stimulated K-Cl COT. Calyculin A blocked the PDGF-stimulated K-Cl COT by 60%, suggesting that protein phosphatase-1 (PP-1) is a mediator in the PDGF signaling pathway/s. In conclusion, our results indicate that the PDGF-mediated pathways of K-Cl COT regulation involve the signaling molecules PI 3-K and PP-1. 相似文献
993.
Programmed ribosomal bypassing occurs in decoding phage T4 gene 60 mRNA. Half the ribosomes bypass a 50 nucleotide gap between codons 46 and 47. Peptidyl-tRNA dissociates from the "take-off" GGA, codon 46, and re-pairs to mRNA at a matched GGA "landing site" codon directly 5' of codon 47 where translation resumes. The system described here allows the contribution of peptidyl-tRNA re-pairing to be measured independently of dissociation. The matched GGA codons have been replaced by 62 other matched codons, giving a wide range of bypassing efficiencies. Codons with G or C in either or both of the first two codon positions yielded high levels of bypassing. The results are compared with those from a complementary study of non-programmed bypassing, where the combined effects of peptidyl-tRNA dissociation and reassociation were measured. The wild-type, GGA, matched codons are the most efficient in their gene 60 context in contrast to the relatively low value in the non-programmed bypassing study. 相似文献
994.
995.
Secondary lymphoid tissue chemokine (CCL21) activates CXCR3 to trigger a Cl- current and chemotaxis in murine microglia 总被引:6,自引:0,他引:6
Rappert A Biber K Nolte C Lipp M Schubel A Lu B Gerard NP Gerard C Boddeke HW Kettenmann H 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(7):3221-3226
Microglial cells represent the major immunocompetent element of the CNS and are activated by any type of brain injury or disease. A candidate for signaling neuronal injury to microglial cells is the CC chemokine ligand CCL21, given that damaged neurons express CCL21. Investigating microglia in acute slices and in culture, we demonstrate that a local application of CCL21 for 30 s triggered a Cl(-) conductance with lasted for tens of minutes. This response was sensitive to the Cl(-) channel blockers 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid and 4-acetamide-4'-isothiocyanatostilbene, 2,2'-disulfonic acid. Moreover, CCL21 triggered a chemotaxis response, which was sensitive to Cl(-) channel blockers. In microglial cells cultured from CCR7 knockout mice, CCL21 produced the same type of Cl(-) current as well as a chemotaxis response. In contrast, in microglial cells from CXCR3 knockout mice, CCL21 triggered neither a Cl(-) conductance nor a chemotaxis response after CCL21 application. We conclude that the CCL21-induced Cl(-) current is a prerequisite for the chemotaxis response mediated by the activation of CXCR3 but not CCR7 receptors, indicating that in brain CCL21 acts via a different receptor system than in lymphoid organs. 相似文献
996.
In this paper we show the effect of oxygen and light on the expression of the photosynthetic apparatus of a mutant heterologously
expressing the puc operon. This mutant was obtained by introducing in trans an expression plasmid, bearing the puc A, B, and C genes of Rhv. sulfidophilum, as well as its own promoter, in an LHII− mutant of Rb. capsulatus. The results showed that oxygen and light repressed LHII expression. Even low-light intensities lowered the LHII content
to undetectable levels by spectrophotometry or by SDS-PAGE. In high-light grown cells, where the relative ratios of LHI and
LHII complexes were significantly diminished, we were able to detect LHII complexes. Under the latter condition, the absorption
spectrum showed that some pigment accumulated in the membrane even in the absence of cell division. These pigments were used
in a later step to assemble LHII complexes, when the high-light grown cells were transferred to semiaerobiosis in the dark.
Transition of high-light grown cells to low-light conditions allowed us to study the adaptability of these heterologous mutant
cells. We observed that adaptation never occurred, in part probably owing to energy limitation.
Received: 20 November 2001 / Accepted: 31 December 2001 相似文献
997.
Gontijo CM Pacheco RS Orefice F Lasmar E Silva ES Melo MN 《Memórias do Instituto Oswaldo Cruz》2002,97(5):751-753
Although cases of leishmaniasis co-infection have been described in acquired immunodeficiency syndrome patients as well as those who have undergone organ transplants, to our knowledge, the present report is the first documented case of simultaneous cutaneous, visceral and ocular leishmaniasis due to Leishmania (Viannia) braziliensis in a transplant patient. The patient had been using immunosuppressive drugs since receiving a transplanted kidney. The first clinical signs of leishmaniasis included fever, thoracic pain, hepatosplenomegaly, leucopenia and anemia. The cutaneous disease was revealed by the presence of amastigotes in the skin biopsy. After three months, the patient presented fever with conjunctive hyperemia, intense ocular pain and low visual acuity. Parasites isolated from iliac crest, aqueous humor and vitreous body were examined using a range of molecular techniques. The same strain of L. (V.) braziliensis was responsible for the different clinical manifestations. The immunosuppressive drugs probably contributed to the dissemination of Leishmania. 相似文献
998.
Lovett JL Marchesini N Moreno SN Sibley LD 《The Journal of biological chemistry》2002,277(29):25870-25876
Calcium-mediated microneme secretion in Toxoplasma gondii is stimulated by contact with host cells, resulting in the discharge of adhesins that mediate attachment. The intracellular source of calcium and the signaling pathway(s) triggering release have not been characterized, prompting our search for mediators of calcium signaling and microneme secretion in T. gondii. We identified two stimuli of microneme secretion, ryanodine and caffeine, which enhanced release of calcium from parasite intracellular stores. Ethanol, a previously characterized trigger of microneme secretion, stimulated an increase in parasite inositol 1,4,5-triphosphate, implying that this second messenger may mediate intracellular calcium release. Consistent with this observation, xestospongin C, an inositol 1,4,5-triphosphate receptor antagonist, inhibited microneme secretion and blocked parasite attachment and invasion of host cells. Collectively, these results suggest that T. gondii possess an intracellular calcium release channel with properties of the inositol 1,4,5-triphosphate/ryanodine receptor superfamily. Intracellular calcium channels, previously studied almost exclusively in multicellular animals, appear to also be critical to the control of parasite calcium during the initial steps of host cell entry. 相似文献
999.
Membrane proximal lysosomes are the major vesicles responsible for calcium-dependent exocytosis in nonsecretory cells 总被引:1,自引:0,他引:1 下载免费PDF全文
Similar to its role in secretory cells, calcium triggers exocytosis in nonsecretory cells. This calcium-dependent exocytosis is essential for repair of membrane ruptures. Using total internal reflection fluorescence microscopy, we observed that many organelles implicated in this process, including ER, post-Golgi vesicles, late endosomes, early endosomes, and lysosomes, were within 100 nm of the plasma membrane (in the evanescent field). However, an increase in cytosolic calcium led to exocytosis of only the lysosomes. The lysosomes that fused were predominantly predocked at the plasma membrane, indicating that calcium is primarily responsible for fusion and not recruitment of lysosomes to the cell surface. 相似文献
1000.