全文获取类型
收费全文 | 10926篇 |
免费 | 797篇 |
国内免费 | 776篇 |
出版年
2024年 | 10篇 |
2023年 | 135篇 |
2022年 | 352篇 |
2021年 | 671篇 |
2020年 | 389篇 |
2019年 | 481篇 |
2018年 | 426篇 |
2017年 | 321篇 |
2016年 | 467篇 |
2015年 | 729篇 |
2014年 | 843篇 |
2013年 | 833篇 |
2012年 | 1043篇 |
2011年 | 833篇 |
2010年 | 501篇 |
2009年 | 478篇 |
2008年 | 518篇 |
2007年 | 491篇 |
2006年 | 391篇 |
2005年 | 373篇 |
2004年 | 294篇 |
2003年 | 257篇 |
2002年 | 191篇 |
2001年 | 207篇 |
2000年 | 151篇 |
1999年 | 163篇 |
1998年 | 97篇 |
1997年 | 110篇 |
1996年 | 110篇 |
1995年 | 102篇 |
1994年 | 107篇 |
1993年 | 65篇 |
1992年 | 65篇 |
1991年 | 84篇 |
1990年 | 53篇 |
1989年 | 43篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 23篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 153 毫秒
971.
Li NJ Zeng GM Huang DL Hu S Feng CL Zhao MH Lai C Huang C Wei Z Xie GX 《Bioresource technology》2011,102(17):8137-8142
The production of oxalate at different initial Pb2+ concentrations during solid-state fermentation of straw with Phanerochaete chrysosporium was investigated. It was found that the maximal peak value of oxalate concentration (22.84 mM) was detected at the initial Pb2+ concentration of 200 mg kg−1 dry straw, while the minimum (15.89 mM) at the concentration of 600 mg Pb2+ kg−1 dry straw, and at moderate concentration of Pb2+ the capability of oxalic acid secretion was enhanced. In addition, it was also found that more oxalic acid accumulation went together with better Pb2+ passivation effect and higher manganese peroxidase (MnP) activity. The present findings will improve the understandings of the interactions of heavy metals with white-rot fungi and the role of oxalate in lignin degradation system, which could provide useful references for more efficient treatment of Pb-contaminated lignocellulosic waste. 相似文献
972.
An increasing progress on the role of Hedgehog (Hh) signaling for carcinogenesis has been achieved since the link of Hh pathway to human cancer was firstly established. In particular, the critical role of Hh signaling in the development of Basal cell carcinoma (BCC) has been convincingly demonstrated by genetic mutation analyses, mouse models of BCCs, and successful clinical trials of BCCs using Hh signaling inhibitors. In addition, the Hh pathway activity is also reported to be involved in the pathogenesis of Squamous Cell Carcinoma (SCC), melanoma and Merkel Cell Carcinoma. These findings have significant new paradigm on Hh signaling transduction, its mechanisms in skin cancer and even therapeutic approaches for BCC. In this review, we will summarize the major advances in the understanding of Hh signaling transduction, the roles of Hh signaling in skin cancer development, and the current implications of “mechanism-based” therapeutic strategies. 相似文献
973.
During brain development, each neuron must find and synapse with the correct pre- and postsynaptic partners. The complexity
of these connections and the relatively large distances some neurons must send their axons to find the correct partners makes
studying brain development one of the most challenging, and yet fascinating disciplines in biology. Furthermore, once the
initial connections have been made, the neurons constantly remodel their dendritic and axonal arbours in response to changing
demands. Neurexin and neuroligin are two cell adhesion molecules identified as important regulators of this process. The importance
of these genes in the development and modulation of synaptic connectivity is emphasised by the observation that mutations
in these genes in humans have been associated with cognitive disorders such as Autism spectrum disorders, Tourette syndrome
and Schizophrenia. The present review will discuss recent advances in our understanding of the role of these genes in synaptic
development and modulation, and in particular, we will focus on recent work in invertebrate models, and how these results
relate to studies in mammals. 相似文献
974.
Dopamine is crucial for habit learning. Activities of midbrain dopaminergic neurons are regulated by the cortical and subcortical signals among which glutamatergic afferents provide excitatory inputs. Cognitive implications of glutamatergic afferents in regulating and engaging dopamine signals during habit learning, however, remain unclear. Here, we show that mice with dopaminergic neuron-specific NMDAR1 deletion are impaired in a variety of habit-learning tasks, while normal in some other dopamine-modulated functions such as locomotor activities, goal-directed learning, and spatial reference memories. In vivo neural recording revealed that dopaminergic neurons in these mutant mice could still develop the cue-reward association responses; however, their conditioned response robustness was drastically blunted. Our results suggest that integration of glutamatergic inputs to DA neurons by NMDA receptors, likely by regulating associative activity patterns, is a crucial part of the cellular mechanism underpinning habit learning. 相似文献
975.
5-Hydroxymethylfurfural (HMF) and furfural could be separated by the Aminex HPX-87H column chromatography, however, the separation and quantification of acetic acid and levulinic acid in biomass hydrolysate have been difficult with this method. In present study, the HPLC separation of acetic acid and levulinic acid on Aminex HPX-87H column has been investigated by varying column temperature, flow rate, and sulfuric acid content in the mobile phase.The column temperature was found critical in resolving acetic acid and levulinic acid. The resolution for two acids increased dramatically from 0.42 to 1.86 when the column temperature was lowered from 60 to 30 °C. So did the capacity factors for levulinic acid that was increased from 1.20 to 1.44 as the column temperature dropped. The optimum column temperature for the separation was found at 45 °C. Variation in flow rate and sulfuric acid concentration improved not as much as the column temperature did. 相似文献
976.
977.
In the present study, the photo-hydrogen production performances by Rhodopseudomonas palustris CQK 01 growing from the inoculated cells with ultra-sonication pretreatment (R. palustris CQK 01-USP) were experimentally investigated in batch culture and compared with that without pretreatment (R. palustris CQK 01-NP). It was found that the ultra-sonication pretreatment modified membrane morphology and broke up part of the cells, resulting in improvement of membrane permeability and bacterial activities and hence, helping the improvement of hydrogen production. The hydrogen production rate, hydrogen yield and energy conversion efficiency with R. palustris CQK 01-USP were increased to be nearly 2 times higher than that with R. palustris CQK 01-NP. The parametric study showed that under the conditions of initial glucose concentration 50 mmol/l, inoculum size 12%, illumination wavelength 590 nm, the photobioreactor with R. palustris CQK 01-USP obtained the optimal hydrogen production rate 0.54 mmol/l/h, hydrogen yield 1.2 mol-H2/mol-glucose and energy conversion efficiency 9.03%. 相似文献
978.
979.
Lan T Liu W Xie X Xu S Huang K Peng J Shen X Liu P Wang L Xia P Huang H 《Molecular endocrinology (Baltimore, Md.)》2011,25(12):2094-2105
Diabetic nephropathy is characterized by accumulation of glomerular extracellular matrix proteins, such as fibronectin (FN). Here, we investigated whether sphingosine kinase (SphK)1 pathway is responsible for the elevated FN expression in diabetic nephropathy. The SphK1 pathway and FN expression were examined in streptozotocin-induced diabetic rat kidney and glomerular mesangial cells (GMC) exposed to high glucose (HG). FN up-regulation was concomitant with activation of the SphK1 pathway as reflected in an increase in the expression and activity of SphK1 and sphingosine 1-phosphate (S1P) production in both diabetic kidney and HG-treated GMC. Overexpression of wild-type SphK1 (SphK(WT)) significantly induced FN expression, whereas treatment with a SphK inhibitor, N,N-dimethylsphingosine, or transfection of SphK1 small interference RNA or dominant-negative SphK1 (SphK(G82D)) abolished HG-induced FN expression. Furthermore, addition of exogenous S1P significantly induced FN expression in GMC with an induction of activator protein 1 (AP-1) activity. Inhibition of AP-1 activity by curcumin attenuated the S1P-induced FN expression. Finally, by inhibiting SphK1 activity, both N,N-dimethylsphingosine and SphK(G82D) markedly attenuated the HG-induced AP-1 activity. Taken together, these results demonstrated that the SphK1 pathway plays a critical role in matrix accumulation in GMC under diabetic condition, suggesting that the SphK1 pathway could be a potential therapeutic target for diabetic nephropathy. 相似文献
980.