全文获取类型
收费全文 | 1972篇 |
免费 | 144篇 |
专业分类
2116篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 22篇 |
2021年 | 28篇 |
2020年 | 23篇 |
2019年 | 50篇 |
2018年 | 45篇 |
2017年 | 42篇 |
2016年 | 73篇 |
2015年 | 109篇 |
2014年 | 110篇 |
2013年 | 144篇 |
2012年 | 169篇 |
2011年 | 143篇 |
2010年 | 94篇 |
2009年 | 96篇 |
2008年 | 126篇 |
2007年 | 126篇 |
2006年 | 107篇 |
2005年 | 103篇 |
2004年 | 98篇 |
2003年 | 79篇 |
2002年 | 77篇 |
2001年 | 18篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 22篇 |
1997年 | 23篇 |
1996年 | 19篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 11篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
排序方式: 共有2116条查询结果,搜索用时 15 毫秒
991.
992.
Hasson H Biswas P Galli L Burastero SE Danise A Bigoloni A Carini E Locatelli M Vecchi A Lazzarin A Castagna A 《The new microbiologica》2006,29(4):223-230
Enfuvirtide (ENF) is the first HIV-1 entry inhibitor used in clinical practice and is currently administered via the subcutaneous route. We here evaluated whether ENF administration leads to a change in humoral parameters, including IgE, possibly related to ENF-associated injection site reactions (ISRs). A 24-week prospective study was conducted in multidrug resistant patients enrolled in the ENF Early Access Program characterized by CD4 counts < or =100 cells/microlitre and no other active antiretroviral drug. Licensed commercial laboratory assays were used to measure the parameters considered in this study. Results are reported as medians (interquartiles IQR). Statistical analyses were performed using Wilcoxon sign rank, Wilcoxon rank sum and Kruskall Wallis tests. Total IgM, IgA and IgG did not change significantly throughout the study. Conversely, a significant increase in IgE was observed in all patients, in those with normal as well as in those with altered IgE at baseline (BL). ISRs such as induration and number of nodules were more frequent in patients with altered BL IgE. IgE increased significantly in all patients, regardless of the different stratifications in their BL CD4 counts. Of note, the ENF-induced increase in CD4 occurred significantly in all patients, independently of their BL IgE levels. The immunological response associated with ENF treatment is accompanied by a selective increase in IgE levels. Determination of IgE could be used in the monitoring ISRs associated with ENE 相似文献
993.
Ortu S Molicotti P Sechi LA Pirina P Saba F Vertuccio C Deriu A Maida I Mura MS Zanetti S 《The new microbiologica》2006,29(1):75-80
We have developed a Real-Time PCR assay to detect M. tuberculosis using the iCycler iQ detection system by TaqMan assay directly on the clinical specimen. A total of 513 clinical samples were taken from patients with suspected tuberculosis and other patients that had an active mycobacterial infection, as well as patients with diagnosed tuberculosis who were receiving antitubercular therapy. The sensitivity and specificity of this assay, 10% and 100%, respectively, were compared to those of conventional microbiological methods. 相似文献
994.
Mitchell B Max Tianxia Wu Steven J Atlas Robert R Edwards Jennifer A Haythornthwaite Antonella F Bollettino Heather S Hipp Colin D McKnight Inge A Osman Erin N Crawford Maryland Pao Jemiel Nejim Albert Kingman Daniel C Aisen Michele A Scully Robert B Keller David Goldman Inna Belfer 《Molecular pain》2006,2(1):1-15
Most current methods for assessing pain in animals are based on reflexive measures and require constant interaction between the observer and the animal. Here we explore two new fully automated methods to quantify the impact of pain on the overall behavior of the organism. Both methods take advantage of the animals' natural preference for a dark environment. We used a box divided into two compartments: dark and bright. In the motoric operant task, "AngleTrack", one end of the box was raised so that the animals had to climb uphill to go from the light to the dark compartment. In the thermal operant task, "ThermalTrack", the floor of the dark compartment was heated to a given temperature, while the light compartment remained at 25°C. Rats were individually placed in the light box and their crossing between chambers monitored automatically for 30 minutes. The angle of the box, or the temperature of the dark compartment, was altered to challenge the animals' natural preference. We test the hypothesis that different models of pain (inflammatory or neuropathic) can be differentiated based on performance on these devices. Three groups of rats were tested at five different challenge levels on both tasks: 1) normal, 2) neuropathic injury pain (Spared Nerve Injury), and 3) inflammatory pain (intraplantar injection of Carrageenan). We monitored the position of the animals as well as their rate of switching between compartments. We find significant differences between the three groups and between the challenge levels both in their average position with respect to time, and in their switching rates. This suggests that the angle-track and thermal-track may be useful in assessing automatically the global impact of different types of pain on behavior. 相似文献
995.
De Rossi A Desiderio C 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2006,839(1-2):6-11
High sensitivity analysis of oxprenolol in spiked human urine has been performed by capillary zone electrophoresis (CZE) in ammonium formate buffer pH 2.5 using an uncoated capillary with 1cm length C18 on-capillary preconcentrator at the inlet side. The preconcentrator was fabricated in laboratory using the packing method and not encapped C18 5 microm particles as stationary phase material. The packed path was retained into the capillary by sintered stationary phase frits. Before running the CZE analysis, the oxprenolol was eluted from the preconcentrator by injecting a short plug of acetonitrile/water mixtures. With respect to classical CZE, the use of on-line preconcentrator widely increased the method sensitivity allowing the detection of the drug at 0.5 ng/mL (injected concentration). The method showed a linear response in the range of 1-150 ng/mL oxprenolol standard compound. The intra-day repeatability (n = 11) R.S.D. values for migration time, peak area and normalized peak area were 0.72%, 3.96% and 3.66%, respectively, while inter-day repeatability (n = 5 days) R.S.D. values were 2.74%, 9.41% and 9.83%, respectively. The method was successfully applied to the analysis of oxprenolol in extracted urine spiked at 250 pg/mL (oxprenolol LOQ concentration in urine). 相似文献
996.
Bertini L Rossi I Zambonelli A Amicucci A Sacchi A Cecchini M Gregori G Stocchi V 《Microbiological research》2006,161(1):59-64
Tuber ectomycorrhizae in a Tuber magnatum "truffière", located in Central Italy, were studied using molecular methods. Specifically, RFLP-ITS analyses, ITS sequencing and specific probes hybridization were used to identify 335 Tuber-like ectomycorrhizal morphotypes. Molecular identification was possible even when distinct morphological characteristics were lacking. For the first time, T. magnatum ectomycorrhizae and other coexisting Tuber species collected in the field were analysed using molecular tools for unambiguous identification. Although the "truffière" under investigation yields good harvests of T. magnatum fruiting bodies, the percentage of T. magnatum ectomycorrhizae found was very low (less than 4.4% of the 335 root tips analysed), whereas the percentages of Tuber maculatum and Tuber rufum were considerably higher (48.9% and 19.0%, respectively). 相似文献
997.
998.
Naldini A Leali D Pucci A Morena E Carraro F Nico B Ribatti D Presta M 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(7):4267-4270
Inflammation plays an important role in the onset of angiogenesis. In the present study, we show that osteopontin (OPN), a proinflammatory mediator involved in tissue repair, induces IL-1beta up-regulation in human monocytes. This was accompanied by the enhanced production of TNF-alpha, IL-8, and IL-6, a decreased release of IL-10, and increased p38 phosphorylation. The supernatants of OPN-treated monocytes were highly angiogenic when delivered on the chick embryo chorioallantoic membrane. The angiogenic response was completely abrogated by a neutralizing anti-IL-1 Ab, thus indicating that this cytokine represents the major proangiogenic factor expressed by OPN-activated monocytes. Accordingly, rIL-1beta mimicked the proangiogenic activity of OPN-treated monocyte supernatants, and IL-1R (type I) was found to be expressed in the chorioallantoic membrane. In conclusion, OPN-activated monocytes may contribute to the onset of angiogenesis through a mechanism mediated by IL-1beta. 相似文献
999.
Metere A Mallozzi C Minetti M Domenici MR Pèzzola A Popoli P Di Stasi AM 《Journal of neurochemistry》2006,97(5):1327-1336
Quinolinic acid (QA) has been shown to evoke neurotoxic events via NMDA receptor (NMDAR) overactivation and oxidative stress. NMDARs are particularly vulnerable to free radicals, which can modulate protein tyrosine kinase (PTK) and phosphotyrosine phosphatase (PTP) activities. The src family of tyrosine kinases are associated with the NMDAR complex and regulate NMDA channel function. Because QA is an NMDAR agonist as well as a pro-oxidant agent, we investigated whether it may affect the activity of PTKs and PTPs in vivo and in vitro. In synaptosomes prepared from striata dissected 15 min, 30 min or 15 days after bilateral injection of QA we observed modulation of the phosphotyrosine pattern; a significant decrease in PTP activity; and a sustained increase in c-src and lyn activity at 15 and 30 min after treatment with QA, followed by a decrease 2 weeks later. Striatal synaptosomes treated in vitro with QA showed time- and dose-dependent modulation of c-src and lyn kinase activities. Moreover, the nitric oxide synthase inhibitor NG-nitro-L-arginine-methyl ester, the NMDAR antagonist d-2-amino-5-phosphonovaleric acid and pyruvate suppressed the QA-induced modulation of c-src activity. These findings suggest a novel feature of QA in regulating src kinase activity through the formation of reactive radical species and/or NMDAR overactivation. 相似文献
1000.
Santini MT Romano R Rainaldi G Indovina P Ferrante A Motta A Indovina PL 《Radiation research》2006,166(5):734-745
The metabolic changes that occur as a function of time in MG-63 osteosarcoma three-dimensional tumor spheroids undergoing radiation-induced apoptosis were studied using high-resolution proton nuclear magnetic resonance ((1)H-NMR) spectroscopy. Specifically, the (1)H-NMR spectra of MG-63 spheroids collected at 24, 48 and 72 h after exposure to 5 Gy of ionizing radiation were compared to the spectra of their respective controls. Small spheroids (about 50-80 microm in diameter) with no hypoxic center were used. Apoptosis was verified by both staining of spheroid DNA with the Hoechst 33258 dye and determination of caspase 3 enzyme activity at the three times examined. The results demonstrate that, as the percentage of apoptosis rises with time after exposure to ionizing radiation, the metabolic changes that take place in MG-63 spheroids follow very precise temporal dynamics. In particular, significant time-related increases in both CH(2) and CH(3) mobile lipids, considered by many authors as markers of apoptosis, were observed. In addition, temporal variations were also observed in choline-containing metabolites, reduced glutathione (GSH), glutamine/glutamate, taurine, alanine, creatine/phosphocreatine and lactate. These data show that in addition to CH(2) and CH(3) lipids, other metabolites can also be extremely useful in a deeper understanding of the temporal dynamics of radiation-induced apoptosis. This comprehension is particularly important in spheroids, a cell model of great complexity that resembles in vivo tumors much more closely than monolayer cultures. Ultimately, it is hoped that such studies can help to evaluate the outcome of radiotherapy protocols more accurately. 相似文献