全文获取类型
收费全文 | 2277篇 |
免费 | 175篇 |
国内免费 | 1篇 |
专业分类
2453篇 |
出版年
2024年 | 4篇 |
2023年 | 15篇 |
2022年 | 35篇 |
2021年 | 70篇 |
2020年 | 44篇 |
2019年 | 49篇 |
2018年 | 51篇 |
2017年 | 39篇 |
2016年 | 72篇 |
2015年 | 127篇 |
2014年 | 146篇 |
2013年 | 148篇 |
2012年 | 228篇 |
2011年 | 208篇 |
2010年 | 131篇 |
2009年 | 99篇 |
2008年 | 160篇 |
2007年 | 158篇 |
2006年 | 126篇 |
2005年 | 115篇 |
2004年 | 96篇 |
2003年 | 90篇 |
2002年 | 77篇 |
2001年 | 23篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 10篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1970年 | 2篇 |
1968年 | 3篇 |
1967年 | 1篇 |
1966年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有2453条查询结果,搜索用时 13 毫秒
991.
Nancy L. Segal Brittney A. Hernandez Jamie L. Graham Ulrich Ettinger 《Human nature (Hawthorne, N.Y.)》2018,29(4):402-417
Relationships of physical resemblance to personality similarity and social affiliation have generated considerable discussion among behavioral science researchers. A “twin-like” experimental design (involving genetically unrelated look-alikes, U-LAs) explores associations among resemblance in appearance, the Big Five personality traits, self-esteem, and social attraction within an evolutionary framework. The Personality for Professionals Inventory (PfPI), NEO/NEO-FFI-3, Rosenberg Self-Esteem Scale, and a Social Relationship Survey were variously completed by 45 U-LA pairs, identified from the “I’m Not a Look-Alike” project, Mentorn Media, and personal referrals. The mean U-LA intraclass correlations were negligible for all Big Five personality traits on the PfPI and NEO/NEO-FFI-3 (ri =??.02 and???.04, respectively). In contrast, mean ri values of .53 and .15 for monozygotic (MZA) and dizygotic (DZA) reared-apart twins, respectively, have been reported for these personality measures. The U-LA self-esteem correlation (ri =??.18) was also below the correlations reported for MZ and DZ reared-together twins (ri = .31 and .13, respectively). Finally, far fewer U-LAs expressed close social relationships (20%) than MZA (80%) and DZA (65%) twins. The present study extends earlier findings indicating that appearance is not meaningfully related to personality similarity and social relatedness. The criticism that MZ twins are alike in personality because their matched looks invite similar treatment by others is refuted. A more judicious interpretation is reactive genotype-environment correlation, namely that MZ twins’ similar personalities evoke similar reactions from others. MZ twins’ close social relations most likely derive from their perceptions of genetically based within-pair similarities that are lacking in U-LAs. 相似文献
992.
David A H Murray Richard J Lloyd Jamie E Hopkinson 《Australian Journal of Entomology》2005,44(1):62-67
Abstract Insecticide resistance in Helicoverpa armigera (Hübner) has led to the reduced efficacy of some older insecticide groups (pyrethroids and carbamates) and serious crop losses. Eight small-plot experiments were conducted to evaluate new insecticides for the management of H. armigera in grain crops. Several products showed efficacy equivalent to or better than the commercial standard, thiodicarb. Indoxacarb and spinosad at rates 50% or less of the registered rates for cotton were consistently superior to other tested products across the range of crops treated and provided residual protection for up to 14 d. The insect growth regulator compound, methoxyfenozide, was slower acting than other products tested, but demonstrated potential for H. armigera management. Pyridalyl performed well and warrants further evaluation in grain crops. We discuss the positioning of new compounds in an Insecticide Resistance Management Strategy (IRMS) in relation to a farming system that incorporates both grain and cotton crops. Use guidelines are recommended for indoxacarb, the first new compound to be registered in selected grain crops and cotton in Australia. These guidelines include restricted-use periods and limits on the number of applications per crop. It is anticipated that additional new compounds will be registered in grain crops, leading to the reduced selection pressure on the limited number of efficacious products. Coordinated insecticide use across farming systems and compatibility with developing integrated pest management programs should be fundamental considerations for the future IRMS. 相似文献
993.
Jordan Shaun Bankiewicz Krzysztof S. Eberling Jamie L. VanBrocklin Henry F. O'Neil James P. Jagust William J. 《Neurochemical research》1998,23(4):513-517
In vivo brain microdialysis was used to monitor 6-[18F]fluoro-L-m-tyrosine (FMT) uptake and metabolism in the striatum of conscious freely moving rats for 3 hours after FMT injection (25 mg/kg, iv). Microdialysate collected 20 to 120 min post-dose, contained FMT at a concentration (0.2 to 0.3 nM) approximately ten-fold below that of its metabolite [18F]fluoro-3-hydroxyphenylacetic acid (FPAC; 3.2 to 3.3 nM). D-amphetamine (2.5 mg/kg, i.p.) injected 120 min after significantly increased microdialysate FPAC (3.27 ± 0.31 nM to 4.51 ± 0.45 nM) in control but not reserpinized rats. Taken together these data demonstrate FMT is heavily metabolized following its entry into the striatum yielding FPAC which appears to be stored, at least in part, in reserpine sensitive cytoplasmic vesicles. Presynaptic retention of FPAC may contribute to the preferential accumulation of FMT positron emission tomography (PET) signaling in dopaminergic brain areas. 相似文献
994.
We evaluate the grand potential of a cluster of two molecular species, equivalent to its free energy of formation from a binary vapour phase, using a non-equilibrium molecular dynamics technique where guide particles, each tethered to a molecule by a harmonic force, move apart to disassemble a cluster into its components. The mechanical work performed in an ensemble of trajectories is analysed using the Jarzynski equality to obtain a free energy of disassembly, a contribution to the cluster grand potential. We study clusters of sulphuric acid and water at 300 K, using a classical interaction scheme, and contrast two modes of guided disassembly. In one, the cluster is broken apart through simple pulling by the guide particles, but we find the trajectories tend to be mechanically irreversible. In the second approach, the guide motion and strength of tethering are modified in a way that prises the cluster apart, a procedure that seems more reversible. We construct a surface representing the cluster grand potential, and identify a critical cluster for droplet nucleation under given vapour conditions. We compare the equilibrium populations of clusters with calculations reported by Henschel et al. [J. Phys. Chem. A 2014;118:2599] based on optimised quantum chemical structures. 相似文献
995.
996.
Jiri Simek Jiri Tuma Vlastimil Dohnal Karel Musil Zuzana Ducaiová 《Acta Physiologiae Plantarum》2016,38(7):172
In this pot experiment, cucumbers (Cucumis sativus L.) were grown in a model soil contaminated by three different concentrations of cadmium (40, 160, and 320 mg.kg?1) with different accompanied anions (Cl?, SO4 2?). In all variants, the most Cd (90 %) was accumulated in the roots, but higher content in the case of Cl?. The distribution of Cd in various cucumber organs was as follows: root > stem > leaf > fruits. However, in variants with higher doses of Cd with SO4 2?, the ratio was changed as follows: root > leaf > stem > fruits. In all variants, least of Cd (max. 1 %) was found in fruits. Variants with the highest Cd doses were significantly different by comparison with all other variants, but higher content was in the case of Cl? anion. Stimulation effect on the biomass production and growth of aerial parts and roots of plants in all variants with Cd was observed. Toxicity symptoms, mainly in the presence of leaf chlorosis and yellowing, were more visible in the variants with Cl?, in comparison with SO4 2?. The amounts of phenol compounds in leaves rose almost in all variants. Only the variants with higher Cd content with SO4 2? showed slight reduction. One possible explanation of reduced content may be their bounding on Cd. The content of salicylic acid was reduced in all variants with Cd treatment. However, it is difficult to conclude their role in plant defence responses to heavy metal, because their actual defence mechanism is still unclear. However, from these results, we can suggest that the accompanying anion and the form in which Cd exists may have an impact on the involvement of various antioxidant systems. 相似文献
997.
998.
Jamie L. Kuck Julie A. Bastarache Ciara M. Shaver Joshua P. Fessel Sergey I. Dikalov James M. May Lorraine B. Ware 《Biochemical and biophysical research communications》2018,495(1):433-437
Background
Increased endothelial permeability is central to shock and organ dysfunction in sepsis but therapeutics targeted to known mediators of increased endothelial permeability have been unsuccessful in patient studies. We previously reported that cell-free hemoglobin (CFH) is elevated in the majority of patients with sepsis and is associated with organ dysfunction, poor clinical outcomes and elevated markers of oxidant injury. Others have shown that Vitamin C (ascorbate) may have endothelial protective effects in sepsis. In this study, we tested the hypothesis that high levels of CFH, as seen in the circulation of patients with sepsis, disrupt endothelial barrier integrity.Methods
Human umbilical vein endothelial cells (HUVEC) were grown to confluence and treated with CFH with or without ascorbate. Monolayer permeability was measured by Electric Cell-substrate Impedance Sensing (ECIS) or transfer of 14C-inulin. Viability was measured by trypan blue exclusion. Intracellular ascorbate was measured by HPLC.Results
CFH increased permeability in a dose- and time-dependent manner with 1 mg/ml of CFH increasing inulin transfer by 50% without affecting cell viability. CFH (1 mg/ml) also caused a dramatic reduction in intracellular ascorbate in the same time frame (1.4 mM without CFH, 0.23 mM 18 h after 1 mg/ml CFH, p < 0.05). Pre-treatment of HUVECs with ascorbate attenuated CFH induced permeability.Conclusions
CFH increases endothelial permeability in part through depletion of intracellular ascorbate. Supplementation of ascorbate can attenuate increases in permeability mediated by CFH suggesting a possible therapeutic approach in sepsis. 相似文献999.
This article analyses 845 posts across 78 threads on an English Defence League message board from 20 September 2013 to 4 October 2013 that examined how online activists construct and develop their racial prejudice. Through seeing whites as blameless victims, the posts highlighted the presence of hostility towards Islam and Muslims in a clear in-group and out-group racial binary, where racist comments were never contested or challenged. Rather, they were wholeheartedly supported with social and cultural division at the centre of the prejudice, scapegoating and stereotyping directed towards Islam and Muslims. For a movement that presents itself as anti-racist, the real-life everyday narrative indicates the reality of its most ardent supporters. 相似文献
1000.
Z Cervinková J Simek 《Physiological research / Academia Scientiarum Bohemoslovaca》1992,41(2):141-146
The effect of propylthiouracil (PTU) on the growth activity of intact liver and liver regenerating after partial (65-70%) hepatectomy (PH) was studied in rats. PTU (Propycil, Kali-Chemie, FRG) was dissolved in drinking water (1 g PTU per litre) and this was given to the rats, as their sole source of fluids, three days before PH and then up to the end of the experiment. In rats given PTU, marked inhibition of liver DNA synthesis and the mitotic activity of hepatocytes was found after PH. This effect was potentiated to some extent by partial inanition of the experimental animals given PTU, as demonstrated in a paired feeding test in control rats. PTU inhibition of DNA synthesis in intact and regenerating liver also took effect in thyroidectomized rats, even with substitution (thyroid hormone) therapy. The experiments demonstrated that the effect of propylthiouracil on DNA synthesis in the liver is mediated primarily by way of its direct effect on the liver. 相似文献