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51.
Rapid eyemovements during rapid-eye-movement (REM) sleep are associated withrapid, shallow breathing. We wanted to know whether thiseffect persisted during increased respiratory drive byCO2. In eight healthy subjects, werecorded electroencephalographic, electrooculographic, andelectromyographic signals, ventilation, and end-tidalPCO2 during the night. InspiratoryPCO2 was changed to increaseend-tidal PCO2 by 3 and 6 Torr. During normocapnia, rapid eye movements were associated with a decreasein total breath time by 0.71 ± 0.19 (SE) s(P < 0.05) because of shortenedexpiratory time (0.52 ± 0.08 s,P < 0.001) and with a reduced tidalvolume (89 ± 27 ml, P < 0.05) because of decreased rib cage contribution (75 ± 18 ml, P < 0.05). Abdominal (11 ± 16 ml, P = 0.52) and minuteventilation (0.09 ± 0.21 ml/min, P = 0.66) did not change. Inhypercapnia, however, rapid eye movements were associated with afurther shortening of total breath time. Abdominal breathing was alsoinhibited (79 ± 23 ml, P < 0.05), leading to a stronger inhibition of tidal volume and minuteventilation (1.84 ± 0.54 l/min,P < 0.05). We conclude thatREM-associated respiratory changes are even more pronounced duringhypercapnia because of additional inhibition of abdominal breathing.This may contribute to the reduction of the hypercapnic ventilatory response during REM sleep.

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52.
Dopamine has been implicated in the modulation of diverse forms of behavioral plasticity, including appetitive learning and addiction. An important challenge is to understand how dopamine's effects at the cellular level alter the properties of neural circuits to modify behavior. In the nematode C. elegans, dopamine modulates habituation of an escape reflex triggered by body touch. In the absence of food, animals habituate more rapidly than in the presence of food; this contextual information about food availability is provided by dopaminergic mechanosensory neurons that sense the presence of bacteria. We find that dopamine alters habituation kinetics by selectively modulating the touch responses of the anterior-body mechanoreceptors; this modulation involves a D1-like dopamine receptor, a Gq/PLC-beta signaling pathway, and calcium release within the touch neurons. Interestingly, the body touch mechanoreceptors can themselves excite the dopamine neurons, forming a positive feedback loop capable of integrating context and experience to modulate mechanosensory attention.  相似文献   
53.
Inflammatory breast cancer (IBC) is a rare and highly invasive type of breast cancer, and patients diagnosed with IBC often face a very poor prognosis. IBC is characterized by the lack of primary tumor formation and the rapid accumulation of cancerous epithelial cells in the dermal lymphatic vessels. Given that normal epithelial cells require attachment to the extracellular matrix (ECM) for survival, a comprehensive examination of the molecular mechanisms underlying IBC cell survival in the lymphatic vessels is of paramount importance to our understanding of IBC pathogenesis. Here we demonstrate that, in contrast to normal mammary epithelial cells, IBC cells evade ECM-detachment-induced apoptosis (anoikis). ErbB2 and EGFR knockdown in KPL-4 and SUM149 cells, respectively, causes decreased colony growth in soft agar and increased caspase activation following ECM detachment. ERK/MAPK signaling was found to operate downstream of ErbB2 and EGFR to protect cells from anoikis by facilitating the formation of a protein complex containing Bim-EL, LC8, and Beclin-1. This complex forms as a result of Bim-EL phosphorylation on serine 59, and thus Bim-EL cannot localize to the mitochondria and cause anoikis. These results reveal a novel mechanism that could be targeted with innovative therapeutics to induce anoikis in IBC cells.Inflammatory breast cancer (IBC) is a rare and highly invasive type of breast cancer, and patients diagnosed with IBC often face a very poor prognosis. The 5-year survival rate for patients with IBC is <40%, while the 5-year survival rate of all other breast cancers combined is approximately 90%.1, 2, 3, 4 This poor prognosis can be attributed to a number of factors, including the propensity for misdiagnosis of the disease due to its unique clinical presentation.5, 6, 7 In contrast to most breast cancers, IBC is characterized by the lack of discernible primary tumor formation and the accumulation of cancerous epithelial cells in the dermal lymphatic vessels.8 This lodging of IBC cells in the dermal lymphatics manifests as what appears to be inflammation, oftentimes causing clinicians to incorrectly diagnose the malady. Given that IBC cells are inherently aggressive, misdiagnosis is particularly problematic as a correct diagnosis or appropriate treatment is prolonged until more advanced disease is discovered. Thus it is imperative to gain a better understanding of the unique molecular mechanisms underlying IBC pathogenesis so that improved therapies can be designed to specifically eliminate IBC cells in a manner that improves patient outcome.Unfortunately, few treatment options exist that are specifically designed to combat IBC. A review of nearly 400 IBC patients treated at The University of Texas MD Anderson Cancer Center between 1974 and 2005 demonstrated that there has been no significant improvement in prognosis for patients with IBC over the past 30 years.1 Many recent studies have focused on assessing the efficacy of chemotherapeutic regimens in IBC cells/patients where success had previously been observed only in the treatment of non-IBCs.9, 10 Some progress has been made in understanding the mechanisms underlying the invasive nature of IBC. For instance, Akt1 has been identified as a possible chemotherapeutic target that appears to be involved in the aggressive behavior of IBC cells.11 Other studies have identified RhoC, which is overexpressed in 90% of IBC tissue samples, as a potent oncogene contributing to IBC pathogenesis.11, 12, 13, 14, 15 More recently, evidence implicating the membrane protein TIG1 and the receptor tyrosine kinase Axl in the oncogenic behavior of IBC cells has been uncovered.16 However, despite these advances, knowledge of the biological mechanisms underlying IBC pathogenesis remains fairly rudimentary, and additional research dedicated to understanding the unique molecular pathways involved in IBC progression remains essential.Given that IBC cells do not form a palpable primary tumor and instead flourish in suspension in the lymph of the dermal lymphatic vessels, we hypothesized that IBC cells must have an inherent ability to survive in the absence of attachment to the extracellular matrix (ECM). Normal mammary epithelial cells require attachment to the ECM to inhibit anoikis, which is defined as caspase-dependent cell death caused by ECM detachment.17 It has become clear that tumor progression and metastasis require cancer cells to inhibit anoikis, oftentimes through alterations in intracellular signaling pathways.18, 19, 20 Interestingly, previous studies have shown that ErbB2 and EGFR, which are hyperactivated in a substantial percentage of IBC patients,21 can effectively antagonize the anoikis program to facilitate anchorage-independent growth.22, 23, 24, 25, 26, 27, 28 However, a detailed examination of the molecular mechanisms underlying anoikis inhibition in IBC cells has yet to be completed. In this study, we demonstrate that signaling from EGFR and ErbB2 through ERK/MAPK has a major role in the ability of IBC cells to survive in the absence of ECM attachment. Surprisingly, we have discovered that ERK-mediated anoikis suppression in IBC cells is not due to targeting of the pro-apoptotic protein Bim-EL for degradation that has previously been observed in mammary epithelial cells.23, 27 Rather, ERK activation in IBC cells promotes the formation of a protein complex containing Bim-EL, Beclin-1, and LC8, which functions to sequester Bim-EL from the mitochondria and thereby block anoikis. In support of the importance of this signaling pathway in IBC patients, five of the seven IBC patient samples assayed showed discernible Bim-EL staining. Collectively, these data identify a novel mechanism utilized by IBC cells to survive during ECM detachment and reveal a potential target for the development of anoikis-inducing chemotherapeutics targeting IBC cells.  相似文献   
54.
55.
Calmodulin (CaM) activates the skeletal muscle ryanodine receptor (RyR1) at nanomolar Ca(2+) concentrations but inhibits it at micromolar Ca(2+) concentrations, indicating that binding of Ca(2+) to CaM may provide a molecular switch for modulating RyR1 channel activity. To directly examine the Ca(2+) sensitivity of RyR1-complexed CaM, we used an environment-sensitive acrylodan adduct of CaM. The resulting (ACR)CaM probe displayed high-affinity binding to, and Ca(2+)-dependent regulation of, RyR1 similar to that of unlabeled wild-type (WT) CaM. Upon addition of Ca(2+), (ACR)CaM exhibited a substantial (>50%) decrease in fluorescence (K(Ca) = 2.7 +/- 0.8 microM). A peptide derived from the RyR1 CaM binding domain (RyR1(3614)(-)(43)) caused an even more pronounced Ca(2+)-dependent fluorescence decrease, and a >or=10-fold leftward shift in its K(Ca) (0.2 +/- 0.1 microM). In the presence of intact RyR1 channels in SR vesicles, (ACR)CaM fluorescence spectra were distinct from those in the presence of RyR1(3614)(-)(43), although a Ca(2+)-dependent decrease in fluorescence was still observed. The K(Ca) for (ACR)CaM fluorescence in the presence of SR (0.8 +/- 0.4 microM) was greater than in the presence of RyR1(3614)(-)(43) but was consistent with functional determinations showing the conversion of (ACR)CaM from channel activator (apoCaM) to inhibitor (Ca(2+)CaM) at Ca(2+) concentrations between 0.3 and 1 microM. These results indicate that binding to RyR1 targets evokes significant changes in the CaM structure and Ca(2+) sensitivity (i.e., CaM tuning). However, changes resulting from binding of CaM to the full-length, tetrameric channels are clearly distinct from changes caused by the RyR1-derived peptide. We suggest that the Ca(2+) sensitivity of CaM when in complex with full-length channels may be tuned to respond to physiologically relevant changes in Ca(2+).  相似文献   
56.
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58.
Differences in the biogeochemistry of nitrogen (N) and phosphorus (P) lead to differential losses and inputs during and over time after fire such that fire may affect nutrient limitation of primary productivity. We conducted a nutrient addition experiment in scrubby flatwoods, a Florida scrub community type, to test the hypothesis that nutrient limitation of primary productivity shifts from N limitation in recently burned sites to P limitation in longer unburned sites. We added three levels of N, P, and N and P together to sites 6 weeks, 8 years, and 20 years postfire and assessed the effects of nutrient addition on above- and belowground productivity and nutrient concentrations. At the community level, nutrient addition did not affect aboveground biomass, but root productivity increased with high N?+?P addition in sites 8 and 20 years after fire. At the species level, N addition increased leaf biomass of saw palmetto (Serenoa repens) in sites 6 weeks and 20 years postfire, while P addition increased foliar %P and apical shoot growth of scrub oak (Quercus inopina) in sites 8 and 20 years postfire, respectively. Contrary to our hypothesis, nutrient limitation does not appear to shift with time after fire; recently burned sites show little evidence of nutrient limitation, while increased belowground productivity indicates that scrubby flatwoods are co-limited by N and P at intermediate and longer times after fire.  相似文献   
59.
To maintain protein homoeostasis, animals have developed stress response pathways such as the ubiquitin proteasome system (UPS). Joshi and colleagues have demonstrated that in Caenorhabditis elegans, dopamine release from neurons acts on receptors in the epithelia to modulate protein turnover, by controlling the expression of regulators of the xenobiotic stress response. Dopamine receptor mutants challenged with pathogenic bacteria were defective in protein turnover and were also more sensitive to infection thus highlighting a role for monoamine signalling in innate immunity and stress responses.  相似文献   
60.
1. We have compared the concentration and chemical composition of carp and human plasma lipoproteins and studied their interaction with human fibroblast LDL receptors. 2. The main lipoproteins in carp are of high density (HDL) in contrast to low density lipoproteins (LDL) in human. 3. Carp lipoproteins are devoid of apolipoprotein (apo) E, a major ligand for interaction with LDL receptors in mammals. 4. Carp very low density lipoproteins (VLDL) and LDL but not HDL nor apoA-I cross react with human LDL in their interaction with LDL receptors on human cultured fibroblasts. 5. Carp liver membranes possess high affinity receptors that are saturable and have calcium dependent ligand specificity (apoB and apoE) similar to human LDL receptor. Carp VLDL and LDL but not HDL nor its major apolipoprotein complexed to L-alpha-phosphatidylcholine dimyristoyl (apoA-I-DMPC) competed with the specific binding of human LDL to this receptor.  相似文献   
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