全文获取类型
收费全文 | 896篇 |
免费 | 94篇 |
出版年
2023年 | 13篇 |
2022年 | 9篇 |
2021年 | 23篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 11篇 |
2017年 | 21篇 |
2016年 | 26篇 |
2015年 | 34篇 |
2014年 | 38篇 |
2013年 | 57篇 |
2012年 | 61篇 |
2011年 | 46篇 |
2010年 | 28篇 |
2009年 | 30篇 |
2008年 | 52篇 |
2007年 | 43篇 |
2006年 | 41篇 |
2005年 | 43篇 |
2004年 | 28篇 |
2003年 | 37篇 |
2002年 | 28篇 |
2001年 | 26篇 |
2000年 | 18篇 |
1999年 | 17篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 14篇 |
1990年 | 18篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1967年 | 3篇 |
排序方式: 共有990条查询结果,搜索用时 46 毫秒
91.
92.
cAMP-dependent signalling cascades regulate a number of CNS functions including brain inflammation processes. In this study, we characterized IL-1-induced IL-6 production in hippocampal cells using H19-7/IGF-IR cells and investigated the effect of changes in intracellular cAMP levels on IL-1 activity. IL-1 potently induced IL-6 mRNA expression with a corresponding increase in IL-6 release, in a time- and dose-dependent manner with a maximal at 24 h and with an EC50 value of 0.11 ng/ml. Cell pre-treatment with the IL-1sR antagonist produced a rightward shift of IL-1 dose-response effect with a corresponding decrease in IL-1 potency. IL-1-induced IL 6 release was attenuated in the presence of the p38 MAPK inhibitor SB203580 but was not significantly affected by the PKA inhibitor KT 5720. Western blotting analysis of phospho-CREB cell content showed a marked increase in CREB activation. Similar results were obtained by pharmacologically increasing cAMP using dibutyryl cyclic adenosine monophosphate (dbcAMP) or the cAMP-specific type-4 phosphodiesterase inhibitor rolipram. Both dbcAMP and rolipram increased IL-6 production to about 50% of IL-1 effect. However, in the presence of IL-1, IL-6 production was further potentiated by either dbcAMP and rolipram, reaching 300% and 500% IL-1-induced levels. These data implicate the role of cAMP-dependent pathways on IL-6 production in neuronal cells and suggest novel synergistic mechanisms of regulation of cytokine production in brain. 相似文献
93.
94.
Babacar Diao Papa Ahmed Fall Ibrahima Bah Cyrille Ze Ondo Yoro Diallo Lamine Niang Alain Khassim Ndoye Sérigne Maguèye Gueye Mamadou Ba Bay Assane Diagne 《Andrologie》2006,16(2):131-134
Patients and Methods
This is a retrospective study of patients admitted with gunshot injuries to the external genital organs to the urology departments of Aristide Le Dantec Hospital, Grand Yoff General Hospital and Dakar Principal Hospital, between January 1998 and January 2003. The following parameters were studied: patients’ age and gender, interval between accident and admission, clinical features, complementary investigations and treatment, and early and late outcomes.Results
Only males were observed and the mean age of these patients was 37.7 years (range: 22–52 years). Lesions were accidental in five cases. Two cases of testicular wounds, two cases of corpus cavernosum injuries, two cases of urethral injury, and one case of perineal wound were observed. After excision of the lesions, complementary procedures consisted of: orchidectomy in two cases, corpus cavernosum — albuginea suture in two cases and end-to-end urethral suture in one case. Perineoscrotal wounds were sutured three days after debridement. All patients received antibiotics and antitetanus serum. No death was observed during the immediate follow-up. No case of urethral stricture or erectile dysfunction was observed with a follow-up of 18 months. Semen analysis was normal in the two cases of orchidectomy. 相似文献95.
Ecosystem productivity can be predicted from potential relative growth rate and species abundance 总被引:4,自引:0,他引:4
We show that ecosystem-specific aboveground net primary productivity (SANPP, g g−1 day−1 , productivity on a per gram basis) can be predicted from species-level measures of potential relative growth rate (RGRmax ), but only if RGRmax is weighted according to the species' relative abundance. This is in agreement with Grime's mass-ratio hypothesis. Productivity was measured in 12 sites in a French Mediterranean post-agricultural succession, while RGRmax was measured on 26 of the most abundant species from this successional sere, grown hydroponically. RGRmax was only weakly correlated ( r 2 = 0.12, P < 0.05) with field age when species abundance was not considered, but the two variables were strongly correlated ( r 2 = 0.81, P < 0.001) when the relative abundance of species in each field was taken into account. SANPP also decreased significantly with field age. This resulted in a tight relationship ( r 2 = 0.77, P < 0.001) between productivity and RGRmax weighted according to species relative biomass contribution. Our study shows that scaling-up from the potential properties of individual species is possible, and that information on potential and realized species traits can be integrated to predict ecosystem functioning. 相似文献
96.
DJ López M Egido-Gabas I López-Montero JV Busto J Casas M Garnier F Monroy B Larijani FM Goñi A Alonso 《Biophysical journal》2012,102(9):2077-2085
We propose that accumulated membrane bending energy elicits a neutral sphingomyelinase (SMase) activity in human erythrocytes. Membrane bending was achieved by osmotic or chemical processes, and SMase activity was assessed by quantitative thin-layer chromatography, high-performance liquid chromatography, and electrospray ionization-mass spectrometry. The activity induced by hypotonic stress in erythrocyte membranes had the pH dependence, ion dependence, and inhibitor sensitivity of mammalian neutral SMases. The activity caused a decrease in SM contents, with a minimum at 6 min after onset of the hypotonic conditions, and then the SM contents were recovered. We also elicited SMase activity by adding lysophosphatidylcholine externally or by generating it with phospholipase A(2). The same effect was observed upon addition of chlorpromazine or sodium deoxycholate at concentrations below the critical micellar concentration, and even under hypertonic conditions. A unifying factor of the various agents that elicit this SMase activity is the accumulated membrane bending energy. Both hypo-and hypertonic conditions impose an increased curvature, whereas the addition of surfactants or phospholipase A(2) activation increases the outer monolayer area, thus leading to an increased bending energy. The fact that this latent SMase activity is tightly coupled to the membrane bending properties suggests that it may be related to the general phenomenon of stress-induced ceramide synthesis and apoptosis. 相似文献
97.
Awada M Soulage CO Meynier A Debard C Plaisancié P Benoit B Picard G Loizon E Chauvin MA Estienne M Peretti N Guichardant M Lagarde M Genot C Michalski MC 《Journal of lipid research》2012,53(10):2069-2080
Dietary intake of long-chain n-3 PUFA is now widely advised for public health and in medical practice. However, PUFA are highly prone to oxidation, producing potentially deleterious 4-hydroxy-2-alkenals. Even so, the impact of consuming oxidized n-3 PUFA on metabolic oxidative stress and inflammation is poorly described. We therefore studied such effects and hypothesized the involvement of the intestinal absorption of 4-hydroxy-2-hexenal (4-HHE), an oxidized n-3 PUFA end-product. In vivo, four groups of mice were fed for 8 weeks high-fat diets containing moderately oxidized or unoxidized n-3 PUFA. Other mice were orally administered 4-HHE and euthanized postprandially versus baseline mice. In vitro, human intestinal Caco-2/TC7 cells were incubated with 4-hydroxy-2-alkenals. Oxidized diets increased 4-HHE plasma levels in mice (up to 5-fold, P < 0.01) compared with unoxidized diets. Oxidized diets enhanced plasma inflammatory markers and activation of nuclear factor kappaB (NF-κB) in the small intestine along with decreasing Paneth cell number (up to -19% in the duodenum). Both in vivo and in vitro, intestinal absorption of 4-HHE was associated with formation of 4-HHE-protein adducts and increased expression of glutathione peroxidase 2 (GPx2) and glucose-regulated protein 78 (GRP78). Consumption of oxidized n-3 PUFA results in 4-HHE accumulation in blood after its intestinal absorption and triggers oxidative stress and inflammation in the upper intestine. 相似文献
98.
Guillaume Vilain Josette Garnier Gaëlle Tallec Julien Tournebize 《Biogeochemistry》2012,111(1-3):253-271
Production and accumulation of nitrous oxide (N2O), a major greenhouse gas, in shallow groundwater might contribute to indirect N2O emissions to the atmosphere (e.g., when groundwater flows into a stream or a river). The Intergovernmental Panel on Climate Change (IPCC) has attributed an emission factor (EF5g) for N2O, associated with nitrate leaching in groundwater and drainage ditches—0.0025 (corresponding to 0.25% of N leached which is emitted as N2O)—although this is the subject of considerable uncertainty. We investigated and quantified the transport and fate of nitrate (NO3 ?) and dissolved nitrous oxide from crop fields to groundwater and surface water over a 2-year period (monitoring from April 2008 to April 2010) in a transect from a plateau to the river with three piezometers. In groundwater, nitrate concentrations ranged from 1.0 to 22.7 mg NO3 ?–N l?1 (from 2.8 to 37.5 mg NO3 ?–N l?1 in the river) and dissolved N2O from 0.2 to 101.0 μg N2O–N l?1 (and from 0.2 to 2.9 μg N2O–N l?1 in the river). From these measurements, we estimated an emission factor of EF5g = 0.0026 (similar to the value currently used by the IPCC) and an annual indirect N2O flux from groundwater of 0.035 kg N2O–N ha?1 year?1, i.e., 1.8% of the previously measured direct N2O flux from agricultural soils. 相似文献
99.
Violle C Enquist BJ McGill BJ Jiang L Albert CH Hulshof C Jung V Messier J 《Trends in ecology & evolution》2012,27(4):244-252
Despite being recognized as a promoter of diversity and a condition for local coexistence decades ago, the importance of intraspecific variance has been neglected over time in community ecology. Recently, there has been a new emphasis on intraspecific variability. Indeed, recent developments in trait-based community ecology have underlined the need to integrate variation at both the intraspecific as well as interspecific level. We introduce new T-statistics ('T' for trait), based on the comparison of intraspecific and interspecific variances of functional traits across organizational levels, to operationally incorporate intraspecific variability into community ecology theory. We show that a focus on the distribution of traits at local and regional scales combined with original analytical tools can provide unique insights into the primary forces structuring communities. 相似文献
100.
Malou N Tran TN Nappez C Signoli M Le Forestier C Castex D Drancourt M Raoult D 《PloS one》2012,7(2):e31744