全文获取类型
收费全文 | 937篇 |
免费 | 90篇 |
国内免费 | 22篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 23篇 |
2021年 | 20篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 27篇 |
2016年 | 31篇 |
2015年 | 18篇 |
2014年 | 34篇 |
2013年 | 32篇 |
2012年 | 31篇 |
2011年 | 45篇 |
2010年 | 44篇 |
2009年 | 78篇 |
2008年 | 75篇 |
2007年 | 72篇 |
2006年 | 63篇 |
2005年 | 68篇 |
2004年 | 45篇 |
2003年 | 30篇 |
2002年 | 17篇 |
2001年 | 8篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 23篇 |
1996年 | 25篇 |
1995年 | 10篇 |
1994年 | 16篇 |
1993年 | 18篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有1049条查询结果,搜索用时 31 毫秒
61.
Ostadal P Alan D Hajek P Horak D Vejvoda J Trefanec J Mates M Vojacek J 《Molecular and cellular biochemistry》2003,246(1-2):45-50
The aim of our study was to evaluate whether a single dose of cerivastatin at the time of admission of patients with unstable angina pectoris (UAP) or non-Q-wave myocardial infarction (NQMI) can influence the serum level of C-reactive protein (CRP), interleukin-6 (IL-6) and interleukin-8 (IL-8) 24 h later. Forty-four patients with rest chest pain and subendocardial ischemia on ECG were randomized to receive cerivastatin 0.3 mg at the time of admission (group C+) to standard therapy or to remain just on standard therapy (group C–). Blood samples for determination of troponin I (TI), CRP, IL-6 and IL-8 were collected at admission (entry level) and 24 h later (final level). Patients with non-physiological baseline levels of TI, as well as patients with progression to Q wave MI were excluded. All baseline, clinical and demographic data and final values of TI were comparable in the two groups. In patients treated with cerivastatin (group C+, n = 13) we observed decrease in the CRP level (–6.73 ± 3.93 mg/L); on the other hand, in group C– (n = 17) the CRP level increased (+7.92 ± 2.77 mg/L, p = 0.004). Similar differences were observed also in IL-6: in group C+ the level was significantly reduced as compared with the increase in group C– (–0.76 ± 0.52 vs. 4.58 ± 1.49 ng/L, p = 0.005). The level of IL-8 was not affected. Our results suggest that early treatment with cerivastatin can decrease the serum level of CRP and IL-6 in patients with UAP/NQMI; this might positively influence their prognosis. Nevertheless, further studies are needed to support this hypothesis. 相似文献
62.
Ormseth OA Ben-David M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(5-6):419-428
Studies following the Exxon Valdez oil spill in Prince William Sound, Alaska indicated that river otters (Lontra canadensis) from oiled regions displayed symptoms of degraded health, including reduced body weight. We examined the fate of ingested
oil in the digestive tract and its effects on gut function in captive river otters. Fifteen wild-caught males were assigned
to three groups, two of which were given weathered crude oil in food (i.e., control, 5 ppm day−1, and 50 ppm day−1) under controlled conditions at the Alaska Sealife Center. Using glass beads as non-specific digesta markers and stable isotope
analysis, we determined the effects of ingested oil on retention time and nutrient uptake. Our data indicated that oil ingestion
reduced marker retention time when we controlled for activity and meal size. Fecal isotope ratios suggested that absorption
of lipids in the oiled otters might have been affected by reduced retention time of food. In addition, a dilution model indicated
that as much as 80% of ingested oil was not absorbed in high-dose animals. Thus, while the ingestion of large quantities of
weathered crude oil appears to reduce absorption of oil hydrocarbons and may alleviate systemic effects, it may concurrently
affect body condition by impacting digestive function.
Accepted: 18 May 2000 相似文献
63.
Dehairs F. Rao R. G. Chandra Mohan P. Raman A.V. Marguillier S. Hellings L. 《Hydrobiologia》2000,431(2-3):225-241
Stable carbon isotopic composition and C/N ratio were used to trace the input of carbon associated with mangrove litter into the estuary of the Godavari–Gautami delta system and Kakinada bay (Andhra Pradesh, India). Suspended organic matter in the mangrove channels was more depleted in 13C (average 13C = –24.5) than in Kakinada bay which showed 13C values for suspended matter (average 13C = –22.7) closer to those expected for marine phytoplankton. Suspended organic matter from mangrove channels was enriched in nitrogen (average C/N atom ratio 12.7) and 13C (average 13C = –24.5) relative to mangrove leaf litter, which had a C/N ratio of 75 and a 13C value of –28. Lowest C/N ratios for suspended matter were observed during southwest monsoon when rainfall was highest. Although in general, mangrove litter fall was also lower during this period, no clear correlation was observed between litter fall and C/N ratio of suspended matter. In general, the composition of suspended matter pointed towards phytoplankton as a major component. Isotopic composition of zooplankton suggested selective feeding on 13C-enriched, marine phytoplankton in open Kakinada bay and on 13C-depleted organic matter, such as estuarine phytoplankton and mangrove litter, in the mangrove channels. From the 13C signature, it appeared that mangrove carbon was present to some extent in zooplankton and macrofauna from the mangrove mudflats and channels, but the signal rapidly decreased in Kakinada bay. Nitrogen isotopic composition of zooplankton and macrofauna indicated a progressive enrichment of 15N away from the mangrove forest towards the northern part of Kakinada bay, in approach of Kakinada city. This is thought to reflect input of anthropogenic nitrogen enriched in 15N and subsequent uptake of this enriched nitrogen into the aquatic food chain. 相似文献
64.
The apoplastic pH of guard cells probably acidifies in response to light, since light induces proton extrusion by both guard
cells and epidermal leaf cells. From the data presented here, it is concluded that these apoplastic pH changes will affect
K+ fluxes in guard cells of Arabidopsis thaliana (L.) Heynh. Guard cells of this species were impaled with double-barrelled microelectrodes, to measure the membrane potential
(Em) and the plasma-membrane conductance. Guard cells were found to exhibit two states with respect to their Em, a depolarized and a hyperpolarized state. Apoplastic acidification depolarized Em in both states, though the origin of the depolarization differed for each state. In the depolarized state, the change in
Em was the result of a combined pH effect on instantaneously activating conductances and on the slow outward rectifying K+ channel (s-ORC). At a more acidic apoplastic pH, the current through instantaneously activated conductances became more inwardly
directed, while the maximum conductance of s-ORC decreased. The effect on s-ORC was accompanied by an acceleration of activation
and deactivation of the channel. Experiments with acid loading of guard cells indicated that the effect on s-ORC was due to
a lowered intracellular pH, caused by apoplastic acidification. In the hyperpolarized state, the pH-induced depolarization
was due to a direct effect of the apoplastic pH on the inward rectifying K+ channel. Acidification shifted the threshold potential of the channel to more positive values. This effect was accompanied
by a decrease in activation times and an increase of deactivation times, of the channel. From the changes in Em and membrane conductance, the expected effect of acidification on K+ fluxes was calculated. It was concluded that apoplastic acidification will increase the K+-efflux in the depolarized state and reduce the K+-influx in the hyperpolarized state.
Received: 28 April 1997 / Accepted: 10 November 1997 相似文献
65.
目的:构建两个高表达人TNFα和IL-1β细胞系,建立抗炎药物筛选细胞模型。方法:运用PCR的方法从载体pCMVSport-TNFα和p CMVSport-IL1β上扩增目的基因,以亚克隆方法将目的基因分别插入真核表达载体pcDNA3.1和pFLAG-CMV中,用单酶切、PCR扩增和基因测序的方法鉴定重组效果,然后将重组成功的质粒转入HEK293细胞系内,挑选能够稳定表达并遗传的单克隆细胞株,用蛋白免疫印迹(Western blot)法分析其表达效果。结果:三种鉴定方法均显示重组质粒构建成功。Western blot结果显示,细胞株T3、T4均能较高表达炎症因子TNF-α;细胞株I2、I3、I5均能较高表达炎症因子IL-1β。结论:成功构建了TNFα和IL-1β靶标的药物筛选细胞模型,为筛选具有抗炎作用的中药提供了一个新平台。 相似文献
66.
67.
Xunbao Duan Steve G. Kelsen Allen B. Clarkson Jr Rong Ji Salim Merali 《Proteomics》2010,10(11):2165-2174
To better understand lung oxidant stress responses, we examined A549 lung cells exposed to H2O2 using “stable isotope labeling by amino acids.” We identified 466 cytosolic and 387 nuclear proteins; H2O2 exposure produced ≥twofold differences in 31, all were downregulations. None were previously reported as oxidant stress response proteins, although they share common functions. One of the responders, treacle, was linked to p53, an important oxidative stress response. The Treacher Collins–Franceschetti syndrome can result from treacle mutation and insufficiency was suggested to cause increased p53 leading to the syndrome. However, results here indicate p53 and treacle responses to H2O2 are independent: treacle remains suppressed after p53 recovery; the threshold for treacle reduction is well above that for p53 induction; and treacle suppression by short interfering RNA does not modify the p53 response. Evidence of treacle antioxidant activity include reduction being driven by proteasome degradation independently of mRNA, typical for oxidant‐absorbing proteins, and increased sensitivity to H2O2 consequent to short interfering RNA suppression. Data here show a link between oxidative stress and treacle reduction, demonstrate that treacle does not control p53, provide evidence of a treacle oxidant defense role, support the hypothesis that oxidant stress plays a role in the Treacher Collins–Franceschetti syndrome, and raise the possibility that treacle plays an anti‐oxidant role in lungs. 相似文献
68.
Menno Hoekstra Christian A.C. van der Lans Lars Gullestad Pål Aukrust Theo J.C. van Berkel Erik A.L. Biessen 《Biochemical and biophysical research communications》2010,394(3):792-797
Background
MicroRNAs are being used in the oncology field to characterize tumors and predict the survival of cancer patients. Here, we explored the potential of microRNAs as biomarkers for coronary artery disease (CAD) and acute coronary syndromes.Methods and results
Using real-time PCR-based profiling, we determined the microRNA signature of peripheral blood mononuclear cells (PBMCs) from stable and unstable CAD patients and unaffected controls. 129 of 157 microRNAs measured were expressed by PBMCs and low variability between separate PBMC pools was observed. The presence of CAD in general coincided with a marked 5-fold increase (P < 0.001) in the relative expression level of miR-135a, while the expression of miR-147 was 4-fold decreased (P < 0.05) in PBMCs from CAD patients as compared to controls, resulting in a 19-fold higher miR-135a/miR-147 ratio (P < 0.001) in CAD. MicroRNA/target gene/biological function linkage analysis suggested that the change in PBMC microRNA signature in CAD patients is probably associated with a change in intracellular cadherin/Wnt signaling. Interestingly, unstable angina pectoris patients could be discriminated from stable patients based upon their relatively high expression level of a cluster of three microRNAs including miR-134, miR-198, and miR-370, suggesting that the microRNA signatures can be used to identify patients at risk for acute coronary syndromes.Conclusions
The present study is the first to show that microRNA signatures can possibly be utilized to identify patients exhibiting atherosclerotic CAD in general and those at risk for acute coronary syndromes. Our findings highlight the importance of microRNAs signatures as novel tool to predict clinical disease outcomes. 相似文献69.
An immunoaffinity liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantitation of the zinc endopeptidase matrix metalloproteinase 9 (MMP-9) from mouse serum. Sample preparation for the assay included magnetic bead-based enrichment using an MMP-9 antibody and was performed in a 96-well plate format using a liquid-handling robotic platform. The surrogate peptide GSPLQGPFLTAR derived from MMP-9 by trypsin digestion was monitored using an on-line capillary flow trap-release chromatography setup incorporating a series of trap columns (C18, strong cation exchange, and another C18) prior to nanoflow chromatography and nanospray ionization with selected reaction monitoring (SRM) detection. The assay was fit-for-purpose validated and found to be accurate (<15% interbatch relative error) and precise (<15% interbatch coefficient of variation) across a range from 0.03 to 7.3 nM mouse MMP-9. Finally, the method was employed to measure MMP-9 concentrations in 30 naïve mouse serum samples, and results were compared with those obtained by an immunoassay. 相似文献
70.
合贝爽联合阿托伐他汀治疗不稳定型心绞痛的效果分析 总被引:1,自引:0,他引:1
目的:分析合贝爽联合阿托伐他汀治疗不稳定型心绞痛的临床疗效,为相关治疗提供参考。方法:回顾性分析我院2007年1月至2009年6月确诊为不稳定型心绞痛而住院的患者140例,随机分为常规治疗组、合贝爽治疗组、阿托伐他汀治疗组与合贝爽联合阿托伐他汀治疗组,每组35例患者,持续用药治疗2周后,分析比较各组临床症状的缓解或消失情况。结果:合贝爽联合阿托伐他汀治疗组的心电图(ST-T改变)、早搏、心悸、胸痛、胸闷等主要症状的改善程度明显高于其他三组,差异有统计学意义,P<0.01,但其产生不良反应率偏高。结论:合贝爽联合阿托伐他汀治疗不稳定心绞痛虽可显著缓解心绞痛发作症状,但是也存在较大的副作用,用药时需要引起注意。 相似文献