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41.
42.
研究了冬小麦-夏玉米→春玉米轮作中,长期施用磷肥、有机肥对土壤总磷库、无机磷库的影响及磷肥的产量效应.结果表明,长期施用磷肥、有机肥土壤全磷、总无机磷均有不同程度的积累,土壤磷素的积累以无机磷为主.根据土壤磷素的收支平衡状况,计算出维持土壤磷素收支平衡磷肥的临界用量:冬小麦-夏玉米种植年份为P2O594.7kg·hm-2,春玉米种植年份为P2O551.5kg·hm-2.根据肥料效应函数计算出磷肥(P2O5)的经济最佳、最高产量用量分别为:冬小麦-夏玉米种植年份为135.8、149.8kg·hm-2,春玉米种植年份为88.6、95.9kg·hm-2. 相似文献
43.
目的:探讨肝硬化患者血脂变化与Child-pugh分级之间的关系。方法:选取2009年3月至2011年3月我院收治的82例肝硬化患者作为研究对象,同时选取80例门诊健康体检者作为对照组,采用全自动生化分析仪分别测定空腹血脂水平。结果:空腹血脂水平显著低于对照组,两组比较差异有统计学意义(P<0.05);肝硬化组Child-pugh C级血脂水平显著低于Child-pugh B和Child-pugh A级,3组比较差异有统计学意义(P<0.05)。结论:不同Child-pugh级别的肝硬化患者血脂水平不同,随着Child-pugh分值越高患者的血脂水平越低。患者的血脂水平可能预示患者肝功能损害程度。 相似文献
44.
胡十齐周新伏罗自勉刘利华刘康 《现代生物医学进展》2012,12(23):4479-4481
目的:检测非霍奇金淋巴瘤(non-Hodgkin’s lymphoma,NHL)患者外周血中CD4+CD25+调节性T细胞(CD4+CD25+regulatoryT cell,Treg)的改变,探讨Treg与NHL的相关性。方法:病例组(n=60)为本院收治的初诊NHL患者,对照组(n=60)为本院健康体检者,用流式细胞技术联合标记CD4、CD25检测对照组及病例组化疗前、化疗后的外周血中CD4+CD25+调节性T细胞的分布特点。结果:(1)病例组化疗前外周血中CD4+细胞比例显著低于对照组(P<0.05),CD4+CD25+调节性T细胞比例显著高于对照组(P<0.05);(2)病例组化疗后,CD4+细胞比例明显高于化疗前(P<0.05),CD4+CD25+调节性T细胞比例明显低于化疗前(P<0.05);(3)病例组化疗后CD4+细胞比例与对照组无显著差异(P>0.05),而CD4+CD25+调节性T细胞比例显著高于对照组(P<0.05)。结论:非霍奇金淋巴瘤患者外周血中CD4+CD25+调节性T细胞比例升高,存在机体免疫抑制,化疗可降低CD4+CD25+调节性T细胞比例。 相似文献
45.
Sharma NR Mateu G Dreux M Grakoui A Cosset FL Melikyan GB 《The Journal of biological chemistry》2011,286(35):30361-30376
Hepatitis C virus (HCV) entry into permissive cells is a complex process that involves interactions with at least four co-factors followed by endocytosis and low pH-dependent fusion with endosomes. The precise sequence of receptor engagement and their roles in promoting HCV E1E2 glycoprotein-mediated fusion are poorly characterized. Because cell-free HCV tolerates an acidic environment, we hypothesized that binding to one or more receptors on the cell surface renders E1E2 competent to undergo low pH-induced conformational changes and promote fusion with endosomes. To test this hypothesis, we examined the effects of low pH and of the second extracellular loop (ECL2) of CD81, one of the four entry factors, on HCV infectivity. Pretreatment with an acidic buffer or with ECL2 enhanced infection through changing the E1E2 conformation, as evidenced by the altered reactivity of these proteins with conformation-specific antibodies and stable association with liposomes. However, neither of the two treatments alone permitted direct fusion with the cell plasma membrane. Sequential HCV preincubation with ECL2 and acidic buffer in the absence of target cells resulted in a marked loss of infectivity, implying that the receptor-bound HCV is primed for low pH-dependent conformational changes. Indeed, soluble receptor-pretreated HCV fused with the cell plasma membrane at low pH under conditions blocking an endocytic entry pathway. These findings suggest that CD81 primes HCV for low pH-dependent fusion early in the entry process. The simple triggering paradigm and intermediate conformations of E1E2 identified in this study could help guide future vaccine and therapeutic efforts to block HCV infection. 相似文献
46.
Margaret C. Della Vecchia Anna C. Rued Marcelo D. Carattino 《The Journal of biological chemistry》2013,288(8):5487-5495
Acid-sensing ion channels (ASICs) are trimeric cation-selective proton-gated ion channels expressed in the central and peripheral nervous systems. The pore-forming transmembrane helices in these channels are linked by short loops to the palm domain in the extracellular region. Here, we explore the contribution to proton gating and desensitization of Glu-79 and Glu-416 in the palm domain of ASIC1a. Engineered Cys, Lys, and Gln substitutions at these positions shifted apparent proton affinity toward more acidic values. Double mutant cycle analysis indicated that Glu-79 and Glu-416 cooperatively facilitated pore opening in response to extracellular acidification. Channels bearing Cys at position 79 or 416 were irreversibly modified by thiol-reactive reagents in a state-dependent manner. Glu-79 and Glu-416 are located in β-strands 1 and 12, respectively. The covalent modification by (2-(trimethylammonium)ethyl) methanethiosulfonate bromide of Cys at position 79 impacted conformational changes associated with pore closing during desensitization, whereas the modification of Cys at position 416 affected conformational changes associated with proton gating. These results suggest that β-strands 1 and 12 contribute antagonistically to activation and desensitization of ASIC1a. Site-directed mutagenesis experiments indicated that the lower palm domain contracts in response to extracellular acidification. Taken together, our studies suggest that the lower palm domain mediates conformational movements that drive pore opening and closing events. 相似文献
47.
Colleen B. Estigoy Fredrik Pontén Jacob Odeberg Benjamin Herbert Michael Guilhaus Michael Charleston Joshua W. K. Ho Darryl Cameron Cristobal G. dos Remedios 《Biophysical reviews》2009,1(1):43-49
The intercalated disc (ICD) occupies a central position in the transmission of force, electrical continuity and chemical communication between cardiomyocytes. Changes in its structure and composition are strongly implicated in heart failure. ICD functions include: maintenance of electrical continuity across the ICD; physical links between membranes and the cytoskeleton; intercellular adhesion; maintenance of ICD structure and function; and growth. About 200 known proteins are associated with ICDs, 40% of which change in disease. We systemically reviewed cardiac immunohistochemical data on the Human Protein Atlas (HPA) web site, ExPASy protein binding data and published papers on ICDs. We identified 43 proteins not previously reported, and confirmed 37 proteins that have previously been described. In addition, 102 proteins not present on the HPA web site but were described in ICDs in the literature. We group these into clusters that demonstrate functionally interactive groups of proteins demonstrating that ICDs play a key role in cardiomyocyte function. 相似文献
48.
Gabriela Meneses Ingeborg Becker Gabriela Rosas Gladis Fragoso 《Experimental parasitology》2009,123(4):362-368
This study describes the first days of Taenia crassiceps infection in BALB/c substrains, BALB/cAnN and BALB/cJ, using two stocks of the same strains which were kept in different animal facilities, conventional and pathogen-free conditions, respectively. This study shows that parasite growth restriction shown by conventional BALB/cJ mice changed to parasite growth permissiveness when pathogen-free BALB/cJ mice were used. In addition, the higher number of macrophages, NK cells and intraperitoneal level of IFN-γ found in the conventional restrictive BALB/cJ substrain vanished when the permissiveness to the parasite growth increased. No differences were found in DNA sequences of parasites collected before and after the change in the permissiveness to parasite growth which favors the possibility that the observed modifications could be due to changes in the murine strains and/or their maintenance conditions. 相似文献
49.
Irene Mangialavori Mariela Ferreira-Gomes Mar��a F. Pignataro Emanuel E. Strehler Juan Pablo F. C. Rossi 《The Journal of biological chemistry》2010,285(1):123-130
The purpose of this work was to obtain information about conformational changes of the plasma membrane Ca2+-pump (PMCA) in the membrane region upon interaction with Ca2+, calmodulin (CaM) and acidic phospholipids. To this end, we have quantified labeling of PMCA with the photoactivatable phosphatidylcholine analog [125I]TID-PC/16, measuring the shift of conformation E2 to the auto-inhibited conformation E1I and to the activated E1A state, titrating the effect of Ca2+ under different conditions. Using a similar approach, we also determined the CaM-PMCA dissociation constant. The results indicate that the PMCA possesses a high affinity site for Ca2+ regardless of the presence or absence of activators. Modulation of pump activity is exerted through the C-terminal domain, which induces an apparent auto-inhibited conformation for Ca2+ transport but does not modify the affinity for Ca2+ at the transmembrane domain. The C-terminal domain is affected by CaM and CaM-like treatments driving the auto-inhibited conformation E1I to the activated E1A conformation and thus modulating the transport of Ca2+. This is reflected in the different apparent constants for Ca2+ in the absence of CaM (calculated by Ca2+-ATPase activity) that sharply contrast with the lack of variation of the affinity for the Ca2+ site at equilibrium. This is the first time that equilibrium constants for the dissociation of Ca2+ and CaM ligands from PMCA complexes are measured through the change of transmembrane conformations of the pump. The data further suggest that the transmembrane domain of the PMCA undergoes major rearrangements resulting in altered lipid accessibility upon Ca2+ binding and activation. 相似文献
50.
Dr. Diethard Sanders 《Facies》2000,42(1):227-243
Summary On Kos island, Greece, along an investigated coastal segment 3 km in length, four adjacent sectors were distinguished, (1)
Empros beach, a rocky shore with plunging cliffs and a steeply dipping, submarine talus, (2) Thermi beach, a „coarse-clastic
beach” with a subaerial cliff fringed by a bouldery to coarse gravelly beach with poorly developed zonation, (3) Dimitra beach,
a gravelly beach with well-developed zonation, and (4) Phokas beach, a gravelly beach characterized by finer mean grain size.
The lateral variation in Holocene coastal morphology would lead to different transgressive records: „rapid” sea-level rise
that may be suggested by transgression of the rocky shore is contemporaneous with „gradual” rise recorded by transgression
of the gravelly beaches.
Dimitra beach is an about 500 m long, cuspate, microtidal, wave-dominated gravelly beach. From land offshore, in its fairweather
configuration it shows
During storm upbuilding, the foreshore sand flats disappeared, the gravel ridges were eroded and an even, more gently dipping
storm beachface developed. Beach restoration in a swell regime proceeded in feedback with the emergent fairweather beach morphology.
During ensuing fairweather, the foreshore sand flats were partly winnowed. On Dimitra beach the layer involved in beach face
to uppermost shoreface dynamics was about 1 m thick and 10–15 m wide. In fossil gravelly beach successions, features formed
during highenergy events include both berms and master bedding surfaces. Features of the waning stage are fairweather plunge
steps and relic storm/swell beachfaces (lower beachface). From cuspate gravel ridges of the upper beachface probably only
the basal part is preserved. 相似文献
(a) | a backshore of rounded gravels to small, rounded boulders, |
(b) | a winter storm berm paved by disc-shaped clasts, |
(c) | a belt of beach cusps each centered by an oblique-triangular foreshore sand flat, and flanked by gravel ridges of roughly triangular shape in plan view, |
(d) | a fairweather plunge step, |
(e) | a. „relic storm/swell beachface” (uppermost shoreface during fairweather) of clean, rounded coarse gravels to cobbles, |
(f) | a storm/swell plunge step, and |
(g) | a vencer of gravels to boulders that, farther seaward, grades into submarine sand flats. |