全文获取类型
收费全文 | 689篇 |
免费 | 32篇 |
国内免费 | 1篇 |
专业分类
722篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 22篇 |
2020年 | 8篇 |
2019年 | 17篇 |
2018年 | 25篇 |
2017年 | 17篇 |
2016年 | 27篇 |
2015年 | 42篇 |
2014年 | 47篇 |
2013年 | 50篇 |
2012年 | 61篇 |
2011年 | 48篇 |
2010年 | 35篇 |
2009年 | 29篇 |
2008年 | 44篇 |
2007年 | 49篇 |
2006年 | 39篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 28篇 |
2002年 | 21篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有722条查询结果,搜索用时 15 毫秒
21.
The crystals of the soil-isolated Bacillus thuringiensis (Bt) strain A4 consist of two polypeptides with molecular mass of 140 kDa and 32 kDa that exhibit insecticidal activity against
adult flies of Bactrocera oleae (Diptera). Plasmid curing applied to this strain resulted in the isolation of several subclones exhibiting alterations in
their crystal polypeptides as well as two acrystalliferous subclones. The crystals of subclone 1.1 lacked the 32-kDa polypeptide
and consisted uniquely of a 140-kDa polypeptide antigenically related to the parental 140-kDa crystal polypeptide. Additionally,
the crystals of this subclone exhibited insecticidal activity against B. oleae equivalent to that of the parental strain. Therefore, the 32-kDa crystal polypeptide is dispensable for insecticidal activity,
which appears to be dependent on the presence of the 140-kDa crystal polypeptide.
Received: 5 April 2000 / Accepted 2 May 2000 相似文献
22.
Mar Pujades-Rodriguez Adam Timmis Dimitris Stogiannis Eleni Rapsomaniki Spiros Denaxas Anoop Shah Gene Feder Mika Kivimaki Harry Hemingway 《PloS one》2014,9(8)
Background
Recent experimental evidence suggests that socioeconomic characteristics of neighbourhoods influence cardiovascular health, but observational studies which examine deprivation across a wide range of cardiovascular diseases (CVDs) are lacking.Methods
Record-linkage cohort study of 1.93 million people to examine the association between small-area socioeconomic deprivation and 12 CVDs. Health records covered primary care, hospital admissions, a myocardial infarction registry and cause-specific mortality in England (CALIBER). Patients were aged ≥30 years and were initially free of CVD. Cox proportional hazard models stratified by general practice were used.Findings
During a median follow-up of 5.5 years 114,859 people had one of 12 initial CVD presentations. In women the hazards of all CVDs except abdominal aortic aneurysm increased linearly with higher small-area socioeconomic deprivation (adjusted HR for most vs. least deprived ranged from 1.05, 95%CI 0.83–1.32 for abdominal aortic aneurysm to 1.55, 95%CI 1.42–1.70 for heart failure; I2 = 81.9%, τ2 = 0.01). In men heterogeneity was higher (HR ranged from 0.89, 95%CI 0.75–1.06 for cardiac arrest to 1.85, 95%CI 1.67–2.04 for peripheral arterial disease; I2 = 96.0%, τ2 = 0.06) and no association was observed with stable angina, sudden cardiac death, subarachnoid haemorrhage, transient ischaemic attack and abdominal aortic aneurysm. Lifetime risk difference between least and most deprived quintiles was most marked for peripheral arterial disease in women (4.3% least deprived, 5.8% most deprived) and men (4.6% least deprived, 7.8% in most deprived); but it was small or negligible for sudden cardiac death, transient ischaemic attack, abdominal aortic aneurysm and ischaemic and intracerebral haemorrhage, in both women and men.Conclusions
Associations of small-area socioeconomic deprivation with 12 types of CVDs were heterogeneous, and in men absent for several diseases. Findings suggest that policies to reduce deprivation may impact more strongly on heart failure and peripheral arterial disease, and might be more effective in women. 相似文献23.
Alexandros D. Tselepis George Hahalis Constantinos C. Tellis Eleni C. Papavasiliou Panagiota T. Mylona Alexandra Kourakli Dimitrios C. Alexopoulos 《Journal of lipid research》2010,51(11):3331-3341
Lipoprotein-associated phospholipase A2 (Lp-PLA2) is an independent cardiovascular risk factor. We investigated the plasma levels of Lp-PLA2 activity and mass as a function of plasma lipid levels, LDL subclass profile, and oxidative stress in patients with β-thalassemia. Thirty-five patients with β-thalassemia major (β-TM) and 25 patients with β-thalassemia intermedia (β-TI) participated in the study. Lp-PLA2 activity and mass were measured in total plasma, in apolipoprotein (apo)B-depleted plasma (HDL-Lp-PLA2), and in LDL subclasses. Lp-PLA2 activity produced and secreted from peripheral blood monocytes in culture was also determined. Patients with β-thalassemia are characterized by a predominance of small-dense LDL particles, increased oxidative stress, and very high plasma levels of Lp-PLA2 mass and activity, despite low LDL-cholesterol levels. A significant positive correlation between plasma Lp-PLA2 activity or mass and 8-isoprostane (8-epiPGF2a) and ferritin levels as well as intima-media thickness (IMT) values was observed. An increase in secreted and cell-associated Lp-PLA2 activity from monocytes in culture was observed in both patient groups. The HDL-Lp-PLA2 activity and mass as well as the ratio of HDL-Lp-PLA2/plasma Lp-PLA2 were significantly higher in both patient groups compared with the control group. In conclusion, patients with β-thalassemia exhibit high plasma Lp-PLA2 levels, attributed to increased enzyme secretion from monocytes/macrophages and to the predominance of sdLDL particles in plasma. Plasma Lp-PLA2 is correlated with carotid IMT, suggesting that this enzyme may be implicated in premature carotid atherosclerosis observed in β-thalassemia. 相似文献
24.
Eleni Manousaki Kosmoula Galanaki Lamprini Papadimitriou Nicolas Kalogerakis 《International journal of phytoremediation》2014,16(7-8):755-769
The phytoremediation potential of the halophyte Limoniastrum monopetalum for the removal of Cd and Pb from polluted sites is assessed in this work. Two pot experiments were conducted; the first with wild L. monopetalum grown on soil polluted with Cd and Pb irrigated at different salinities, and the second with commonly cultivated ornamental L. monopetalum grown on soil polluted with Cd irrigated also at different salinities. The data revealed that wild L. monopetalum is a Cd and Pb tolerant plant able to accumulate at least 100 ppm of cadmium in its shoots without showing any significant decrease in terms of biomass production, chlorophyll content or water content suggesting that it could be an accumulator of Cd. Pb above-ground accumulation was kept at low levels with the majority of Pb localized in the roots. On the other hand, contrasting results were obtained for ornamental L. monopetalum which although it was found to be also Cd tolerant, Cd accumulation in its tissues was kept at significantly lower levels especially compared to that of the wild ecotype. In addition for ornamental L. monopetalum salinity did not have a positive effect on Cd accumulation and translocation as observed in the wild type and in other halophytes. Analysis of the salt excretion crystals on the leaf surface confirmed that wild and cultivated ornamental L. monopetalum excrete cadmium and lead through their salt glands as a possible metal detoxification mechanism, although the amount excreted by the ornamental L. monopetalum is significantly less. 相似文献
25.
Eleni A. Charmpila Maximilian Wagner Bettina Reichenbacher 《Journal of fish biology》2021,98(5):1450-1455
Otolith morphology is a widely accepted tool for species identification in teleost fish, but whether this holds true for very small species remains to be explored. Here, the saccular otoliths of the cryptobenthic Mediterranean clingfish Gouania (Gobiesocidae) are described for the first time. The new data, although preliminary, indicate that otolith morphology and morphometry support the recognition of the recently differentiated five species of Gouania in the Mediterranean Sea. Furthermore, otoliths of phylogenetically closely related Gouania species resemble each other more than do those of the more distantly related species. 相似文献
26.
Eleni K. Efthimiadou Nikos Katsaros Alexandra Karaliota George Psomas 《Inorganica chimica acta》2007,360(15):4093-4102
The neutral mononuclear copper(II) complexes with the quinolone antibacterial drugs, pipemidic acid and N-propyl-norfloxacin, in the presence or absence of nitrogen-donor heterocyclic ligands, 2,2′-bipyridine, 1,10-phenanthroline or 2,2′-dipyridylamine, have been prepared and characterized spectroscopically. The interaction of copper(II) with the deprotonated quinolone ligand leads to the formation of the neutral mononuclear complexes of the type [Cu(quinolone)2(H2O)] (1)–(2) while the presence of the N-donor ligand leads to the formation of the neutral mononuclear complexes of the type [Cu(quinolone)(N-donor)Cl] (3)–(8). In all the complexes, copper(II) is pentacoordinate having a distorted square pyramidal geometry. The electron paramagnetic resonance spectra of 1 and 2 are typical of mononuclear Cu(II) complexes, while for the mixed-ligands complexes 3–8 a mixture of dimeric and monomeric species is indicated. The interaction of the complexes with calf-thymus DNA has been investigated with diverse spectroscopic techniques and has shown that the complexes can be bound to calf-thymus DNA by the intercalative mode. The antimicrobial activity of the complexes has been tested on three different microorganisms. All the complexes show an increased biological activity in comparison to the corresponding free quinolone ligand. 相似文献
27.
Thomas J McLoughlin Eleni Mylona Troy A Hornberger Karyn A Esser Francis X Pizza 《Journal of applied physiology》2003,94(3):876-882
We determined the effect of muscle contractions resulting from high-frequency electrical stimulation (HFES) on inflammatory cells in rat tibialis anterior (TA), plantaris (Pln), and soleus (Sol) muscles at 6, 24, and 72 h post-HFES. A minimum of four and a maximum of seven rats were analyzed at each time point. HFES, applied to the sciatic nerve, caused the Sol and Pln to contract concentrically and the TA to contract eccentrically. Neutrophils were higher (P < 0.05) at 6 and 24 h after HFES in the Sol, Pln, and TA muscles relative to control muscles. ED1(+) macrophages in the Pln were elevated at 6 and 24 h after HFES and were also elevated in the Sol and TA after HFES relative to controls. ED2(+) macrophages in the Sol and TA were elevated at 24 and 72 h after HFES, respectively, and were also elevated in the Pln after HFES relative to controls. In contrast to the TA muscles, the Pln and Sol muscles showed no gross histological abnormalities. Collectively, these data indicate that both eccentric and concentric contractions can increase inflammatory cells in muscle, regardless of whether overt histological signs of injury are apparent. 相似文献
28.
Stimulation of adhesion molecule expression in human endothelial cells (HUVEC) by adrenomedullin and corticotrophin 总被引:1,自引:0,他引:1
Hagi-Pavli E Farthing PM Kapas S 《American journal of physiology. Cell physiology》2004,286(2):C239-C246
Adrenomedullin (AM) and corticotrophin (ACTH) are both vasoactive peptides produced by a variety of cell types, including endothelial cells. Although AM and ACTH are considered to be important in the control of blood pressure and the response to stress, respectively, their role in inflammation and the immune response has not been clarified. This study shows, with the use of a cell-based ELISA, that AM and ACTH induce cell surface expression of the adhesion molecules E-selectin, VCAM-1, and ICAM-1 on human umbilical vein endothelial cells (HUVEC). Furthermore, this effect appears to be mediated in part via elevation of cAMP, given that both peptides elevate cAMP, the cell-permeable cAMP analog dibutyryl cAMP is able to mimic induction of all three cell adhesion molecules and the effect of AM and ACTH is inhibited by the adenylyl cyclase inhibitor SQ-22536. These findings demonstrate a role for AM and ACTH in the regulation of the immune and inflammatory response. E-selectin; intercellular adhesion molecule-1; vascular cell adhesion molecule-1; adrenomedullin; adrenocorticotropic hormone; human umbilical vein endothelial cells 相似文献
29.
Aromatic amino-acid side chains are essential components for the structure and function of proteins. We present herein a set of NMR experiments for time-efficient resonance assignment of histidine and tyrosine side chains in uniformly 13C/15N-labeled proteins. The use of band-selective 13C pulses allows to deal with linear chains of coupled spins, thus avoiding signal loss that occurs in branched spin systems during coherence transfer. Furthermore, our pulse schemes make use of longitudinal 1H relaxation enhancement, Ernst-angle excitation, and simultaneous detection of 1H and 13C steady-state polarization to achieve significant signal enhancements. 相似文献
30.
Eleni Timotheadou Konstantine T. Kalogeras Georgia-Angeliki Koliou Ralph M. Wirtz Flora Zagouri Angelos Koutras Elke Veltrup Christos Christodoulou George Pentheroudakis Aris Tsiftsoglou Pavlos Papakostas Gerasimos Aravantinos Vasilios Venizelos Dimitrios Pectasides Paris Kosmidis Charisios Karanikiotis Christos Markopoulos Helen Gogas George Fountzilas 《Translational oncology》2017,10(4):589-598