全文获取类型
收费全文 | 265篇 |
免费 | 15篇 |
专业分类
280篇 |
出版年
2023年 | 1篇 |
2022年 | 9篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 19篇 |
2012年 | 17篇 |
2011年 | 34篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 20篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 12篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1996年 | 4篇 |
1994年 | 2篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有280条查询结果,搜索用时 15 毫秒
21.
22.
Lochner JE Honigman LS Grant WF Gessford SK Hansen AB Silverman MA Scalettar BA 《Journal of neurobiology》2006,66(6):564-577
Tissue plasminogen activator (tPA) has been implicated in a variety of important cellular functions, including learning-related synaptic plasticity and potentiating N-methyl-D-aspartate (NMDA) receptor-dependent signaling. These findings suggest that tPA may localize to, and undergo activity-dependent secretion from, synapses; however, conclusive data supporting these hypotheses have remained elusive. To elucidate these issues, we studied the distribution, dynamics, and depolarization-induced secretion of tPA in hippocampal neurons, using fluorescent chimeras of tPA. We found that tPA resides in dense-core granules (DCGs) that traffic to postsynaptic dendritic spines and that can remain in spines for extended periods. We also found that depolarization induced by high potassium levels elicits a slow, partial exocytotic release of tPA from DCGs in spines that is dependent on extracellular Ca(+2) concentrations. This slow, partial release demonstrates that exocytosis occurs via a mechanism, such as fuse-pinch-linger, that allows partial release and reuse of DCG cargo and suggests a mechanism that hippocampal neurons may rely upon to avoid depleting tPA at active synapses. Our results also demonstrate release of tPA at a site that facilitates interaction with NMDA-type glutamate receptors, and they provide direct confirmation of fundamental hypotheses about tPA localization and release that bear on its neuromodulatory functions, for example, in learning and memory. 相似文献
23.
Sara Gari Jacob R. S. Malungo Adriane Martin-Hilber Maurice Musheke Christian Schindler Sonja Merten 《PloS one》2013,8(8)
This paper explores the effect of social relations and gender-based conflicts on the uptake of HIV testing in the South and Central provinces of Zambia. We conducted a community-based cross-sectional study of 1716 randomly selected individuals. Associations were examined using mixed-effect multivariable logistic regression. A total of 264 men (64%) and 268 women (56%) had never tested for HIV. The strongest determinants for not being tested were disruptive couple relationships (OR = 2.48 95% CI = 1.00–6.19); tolerance to gender-based violence (OR = 2.10 95% CI = 1.05–4.32) and fear of social rejection (OR = 1.48 95% CI = 1.23–1.80). In the Zambian context, unequal power relationships within the couple and the community seem to play a pivotal role in the decision to test which until now have been largely underestimated. Policies, programs and interventions to rapidly increase HIV testing need to urgently address gender-power inequity in relationships and prevent gender-based violence to reduce the negative impact on the lives of couples and families. 相似文献
24.
Abstract A thermophilic Lactobacillus , isolate VB183, was tested for comparative glucose and pentose utilization. The possible adverse effect of high concentrations of metabolic end products on cell yield was lessened or eliminated by using low substrate concentrations. Possible growth due to intracellular reserve material, was counteracted by starving the cells for 90 min before being used as inoculant. Isolate VB183 exhibited a higher growth rate on glucose (μ= 1.08 h−1 ) than on ribose (μ= 0.76 h−1 ). L. salivarius was included as a pentose non-fermenting control and showed no significant difference between growth on basal medium with and without ribose. VB183 was also found to utilize l (+)-arabinose but not d (−)-arabinose, stressing the importance of the isomer of the sugars tested. 相似文献
25.
Canilha L Santos VT Rocha GJ Almeida e Silva JB Giulietti M Silva SS Felipe MG Ferraz A Milagres AM Carvalho W 《Journal of industrial microbiology & biotechnology》2011,38(9):1467-1475
Experiments based on a 23 central composite full factorial design were carried out in 200-ml stainless-steel containers to study the pretreatment,
with dilute sulfuric acid, of a sugarcane bagasse sample obtained from a local sugar–alcohol mill. The independent variables
selected for study were temperature, varied from 112.5°C to 157.5°C, residence time, varied from 5.0 to 35.0 min, and sulfuric
acid concentration, varied from 0.0% to 3.0% (w/v). Bagasse loading of 15% (w/w) was used in all experiments. Statistical
analysis of the experimental results showed that all three independent variables significantly influenced the response variables,
namely the bagasse solubilization, efficiency of xylose recovery in the hemicellulosic hydrolysate, efficiency of cellulose
enzymatic saccharification, and percentages of cellulose, hemicellulose, and lignin in the pretreated solids. Temperature
was the factor that influenced the response variables the most, followed by acid concentration and residence time, in that
order. Although harsher pretreatment conditions promoted almost complete removal of the hemicellulosic fraction, the amount
of xylose recovered in the hemicellulosic hydrolysate did not exceed 61.8% of the maximum theoretical value. Cellulose enzymatic
saccharification was favored by more efficient removal of hemicellulose during the pretreatment. However, detoxification of
the hemicellulosic hydrolysate was necessary for better bioconversion of the sugars to ethanol. 相似文献
26.
27.
Germano Siqueira Adriane MF Milagres Walter Carvalho Gerald Koch André Ferraz 《Biotechnology for biofuels》2011,4(1):7
Background
Lignin and hemicelluloses are the major components limiting enzyme infiltration into cell walls. Determination of the topochemical distribution of lignin and aromatics in sugar cane might provide important data on the recalcitrance of specific cells. We used cellular ultraviolet (UV) microspectrophotometry (UMSP) to topochemically detect lignin and hydroxycinnamic acids in individual fiber, vessel and parenchyma cell walls of untreated and chlorite-treated sugar cane. Internodes, presenting typical vascular bundles and sucrose-storing parenchyma cells, were divided into rind and pith fractions. 相似文献28.
29.
Klippel B Lochner A Bruce DC Davenport KW Detter C Goodwin LA Han J Han S Land ML Mikhailova N Nolan M Pennacchio L Pitluck S Tapia R Woyke T Wiebusch S Basner A Abe F Horikoshi K Keller M Antranikian G 《Journal of bacteriology》2011,193(17):4547-4548
Glaciecola sp. strain 4H-3-7+YE-5 was isolated from subseafloor sediments at Suruga Bay in Japan and is capable of efficiently hydrolyzing cellulose and xylan. The complete genome sequence of Glaciecola sp. 4H-3-7+YE-5 revealed several genes encoding putatively novel glycoside hydrolases, offering a high potential for plant biomass degradation. 相似文献
30.
de Melo ME Cabral AB Maciel MA da Silveira VM de Souza Lopes AC 《Current microbiology》2011,62(5):1596-1601
The objectives of this study were to determine the distribution of phylogenetic groups among Klebsiella pneumoniae isolates from Recife, Brazil and to assess the relationship between the groups and the isolation sites and resistance profile.
Ninety four isolates of K. pneumoniae from hospital or community infections and from normal microbiota were analyzed by gyrA PCR–RFLP, antibiotic susceptibility, and adonitol fermentation. The results revealed the distinction of three phylogenetic
groups, as it has also been reported in Europe, showing that these clusters are highly conserved within K. pneumoniae. Group KpI was dominantly represented by hospital and community isolates while groups KpII and KpIII displayed mainly normal
microbiota isolates. The resistance to third generation cephalosporins, aztreonam, imipenem, amoxicillin/clavulanic acid,
and streptomycin was only observed in KpI. The percentage of resistance was higher in KpI, followed by KpII and KpIII. The
differences in the distribution of K. pneumoniae phylogenetic groups observed in this study suggest distinctive clinical and epidemiological characteristics among the three
groups, which is important to understand the epidemiology of infections caused by this organism. This is the first study in
Brazil on K. pneumoniae isolates from normal microbiota and community infections regarding the distribution of phylogenetic groups based on the gyrA gene. 相似文献