全文获取类型
收费全文 | 534篇 |
免费 | 55篇 |
国内免费 | 1篇 |
专业分类
590篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 14篇 |
2015年 | 27篇 |
2014年 | 16篇 |
2013年 | 38篇 |
2012年 | 35篇 |
2011年 | 33篇 |
2010年 | 22篇 |
2009年 | 24篇 |
2008年 | 31篇 |
2007年 | 30篇 |
2006年 | 24篇 |
2005年 | 29篇 |
2004年 | 36篇 |
2003年 | 26篇 |
2002年 | 21篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 16篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1969年 | 1篇 |
1953年 | 1篇 |
1938年 | 3篇 |
1937年 | 2篇 |
1932年 | 1篇 |
1927年 | 1篇 |
排序方式: 共有590条查询结果,搜索用时 15 毫秒
491.
Jamila Mejdoubi Silvia C. C. M. van den Heijkant Frank J. M. van Leerdam Martijn W. Heymans Remy A. Hirasing Alfons A. M. Crijnen 《PloS one》2013,8(10)
Background
Expectant mothers and mothers of young children are especially vulnerable to intimate partner violence (IPV). The nurse-family partnership (NFP) is a home visitation program in the United States effective for the prevention of adverse child health outcomes. Evidence regarding the effect of nurse home visiting on IPV is inconsistent. This study aims to study the effect of VoorZorg, the Dutch NFP, on IPV.Methods
A random sample of 460 eligible disadvantaged women <26 years, with no previous live births, was randomized. Women in the control group (C; n=223) received usual care; women in the intervention group (I; n=237) received usual care plus nurse home visits periodically during pregnancy and until the child’s second birthday.Results
At 32 weeks of pregnancy, women in the intervention group self-reported significantly less IPV victimization than women in the control group in: level 2 psychological aggression (C: 56% vs. I: 39%), physical assault level 1 (C: 58% vs. I: 40%) and level 2 (C: 31% vs. I: 20%), and level 1 sexual coercion (C: 16% vs. I: 8%). Furthermore, women in the intervention group reported significantly less IPV perpetration in: level 2 psychological aggression (C: 60% vs. I: 46%), level 1 physical assault (C: 65% vs. I: 52%), and level 1 injury (C: 27% vs. I: 17%). At 24 months after birth, IPV victimization was significantly lower in the intervention group for level 1 physical assault (C: 44% vs. I: 26%), and IPV perpetration was significantly lower for level 1 sexual assault (C: 18% vs. I: 3%). Multilevel analyses showed a significant improvement in IPV victimization and perpetration among women in the intervention group at 24 months after birth.Conclusion
VoorZorg, compared with the usual care, is effective in reducing IPV during pregnancy and in the two years after birth among young high-risk women.Trial Registration
Dutch Trial Register NTR854 http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=854 相似文献492.
Selective decrease in circulating V alpha 24+V beta 11+ NKT cells during HIV type 1 infection. 总被引:5,自引:0,他引:5
Hans J J van der Vliet B Mary E von Blomberg Mette D Hazenberg Nobusuke Nishi Sigrid A Otto Birgit H van Benthem Maria Prins Frans A Claessen Alfons J M van den Eertwegh Giuseppe Giaccone Frank Miedema Rik J Scheper Herbert M Pinedo 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(3):1490-1495
CD1d-restricted NKT cells express an invariant TCR and have been demonstrated to play an important regulatory role in a variety of immune responses. Invariant NKT cells down-regulate autoimmune responses by production of type 2 cytokines and can initiate antitumor and antimicrobial immune responses by production of type 1 cytokines. Although defects in the (invariant) Valpha24+Vbeta11+ NKT cell population have been observed in patients with cancer and autoimmune diseases, little is known regarding the protective role of Valpha24+Vbeta11+ NKT cells in human infectious disease. In a cross-sectional study in HIV-1-infected individuals, we found circulating numbers of Valpha24+Vbeta11+ NKT cells to be reduced, independent of CD4+ T cell counts, CD4:CD8 ratios, and viral load. Because a small minority of Valpha24+Vbeta11+ NKT cells of healthy donors expressed HIV-1 (co)receptors and the vast majority of Valpha24+Vbeta11+ NKT cells in HIV-1-infected individuals expressed the Fas receptor, the depletion was more likely due to Fas-mediated apoptosis than to preferential infection of Valpha24+Vbeta11+ NKT cells by HIV-1. A longitudinal cohort study, in which patients were analyzed before seroconversion and 1 and 5 years after seroconversion, demonstrated that a large proportion of the depletion occurred within the first year postseroconversion. In this longitudinal study no evidence was found to support an important role of Valpha24+Vbeta11+ NKT cells in determining the rate of progression during HIV-1 infection. 相似文献
493.
A physical map of bacteriophage T4 including the positions of strong promoters and terminators recognized in vitro 总被引:14,自引:0,他引:14
Hermann Gram Hans-Dieter Liebig Alfons Hack Elisabeth Niggemann Wolfgang Rüger 《Molecular & general genetics : MGG》1984,194(1-2):232-240
Summary We present a linearized physical map of the genome of bacteriophage T4. This map contains the cleavage sites for restriction enzymes SmaI, KpnI, SalI, BglII, XhoI, XbaI, ClaI, HaeII, EcoRI, and EcoRV. It also contains about 200 TaqI sites. The promoter sites recognized in vitro and a number of rho independent terminators have also been mapped. 相似文献
494.
Carla Pereira Magalhães Joaquim A. Ribeiro Ana P. Guedes Ana L. Arantes Diana Z. Sousa Alfons J. M. Stams Maria M. Alves Ana Júlia Cavaleiro 《Microbial biotechnology》2020,13(4):962-973
Glycerol-rich waste streams produced by the biodiesel, bioethanol and oleochemical industries can be treated and valorized by anaerobic microbial communities to produce methane. As current knowledge of the microorganisms involved in thermophilic glycerol conversion to methane is scarce, thermophilic glycerol-degrading methanogenic communities were enriched. A co-culture of Thermoanaerobacter and Methanothermobacter species was obtained, pointing to a non-obligately syntrophic glycerol degradation. This hypothesis was further studied by incubating Thermoanaerobacter brockii subsp. finnii and T. wiegelii with glycerol (10 mM) in pure culture and with different hydrogenotrophic methanogens. The presence of the methanogen accelerated glycerol fermentation by the two Thermoanaerobacter strains up to 3.3 mM day−1, corresponding to 12 times higher volumetric glycerol depletion rates in the methanogenic co-cultures than in the pure bacterial cultures. The catabolic pathways of glycerol conversion were identified by genome analysis of the two Thermoanaerobacter strains. NADH and reduced ferredoxin formed in the pathway are linked to proton reduction, which becomes thermodynamically favourable when the hydrogen partial pressure is kept low by the hydrogenotrophic methanogenic partner. 相似文献
495.
Wolfgang Harreither Alfons K. G. Felice Regina Paukner Lo Gorton Dr. Roland Ludwig Christoph Sygmund 《Biotechnology journal》2012,7(11):1359-1366
Cellobiose dehydrogenase (CDH) is an emerging enzyme in the field of bioelectrocatalysis. Due to its flexible cytochrome domain, which acts as a built‐in redox mediator, CDH is capable of direct electron transfer (DET) to electrode surfaces. This rare property is employed in mediatorless “third generation” biosensors. The ability of Corynascus thermophilus CDH to oxidize glucose under physiological conditions makes it a promising candidate for miniaturized glucose biosensors or glucose powered biofuel cell anodes. We report for the first time the electrochemical application and characterization of a recombinantly produced CDH in a glucose biosensor. Recombinant CDH from C. thermophilus (rCtCDH) was expressed by the methylotrophic yeast Pichia pastoris (376 U L–1, 132 mg L–1). A comparative characterization of rCtCDH and CtCDH shows identical pH optima, KM values and heme b midpoint potentials. In contrast, the specific activity of rCtCDH (2.84 U mg–1) and consequently the turnover numbers were ~five‐times lower than for CtCDH, which was caused by a sub‐stoichiometric occupation of catalytic sites with flavin‐adenin‐dinukleotid (FAD). The performance of rCtCDH‐modified electrodes demonstrates the suitability for electrochemical studies. This opens the possibility to engineer the substrate specificity of C. thermophilus CDH for specific carbohydrates by rational engineering or directed evolution. 相似文献
496.
Markus Butz Lars Timmermann Joachim Gross Bettina Pollok Martin Dirks Harald Hefter Alfons Schnitzler 《Journal of Physiology》2006,99(1):14-20
Writing is a highly skilled and overlearned movement. In patients suffering from writer's cramp, a focal task-induced dystonia, writing is impaired or even impossible due to involuntary muscle contractions and abnormal posture, which occur as soon as the person picks up a pen or within writing a few words. The underlying pathophysiological mechanisms of this movement disorder are not fully understood up to now. The aim of the present study was to unravel the oscillatory network underlying physiological writing in healthy subjects and dystonic writing in writer's cramp patients. Using whole-head magnetoencephalography (MEG) and the analysis tool dynamic imaging of coherent sources (DICS) we studied oscillatory neural coupling during writing in eleven healthy subjects and eight patients suffering from writer's cramp. Simultaneous recording of brain activity with MEG and activity of forearm and hand muscles with surface electromyography (EMG) was performed while subjects were writing for five minutes with their dominant right hand. Applying DICS sources of strongest cerebro-muscular coherence and cerebro-cerebral coherence during writing were identified, which consistently included six brain areas in both, the control subjects and the patients: contralateral and ipsilateral sensorimotor cortex, ipsilateral cerebellum, contralateral thalamus, contralateral premotor and posterior parietal cortex. Coherence between cortical sources and muscles appeared primarily in the frequency of writing movements (3-7 Hz) while coherence between cerebral sources occurred primarily around 10 Hz (8-13 Hz). Interestingly, consistent coupling between both sensorimotor cortices was observed in patients only, whereas coupling between ipsilateral cerebellum and the contralateral posterior parietal cortex was found in control subjects only. These results are consistent with the often described bilateral pathophysiology and impaired sensorimotor integration in writer's cramp patients. 相似文献
497.
Humphrey Fonge Lixin Jin Jan Cleynhens Guy Bormans Alfons Verbruggen 《Bioorganic & medicinal chemistry》2010,18(1):396-402
We have developed four 99mTc(CO)3-labeled lipophilic tracers as potential radiolabeling agents for cells based on a hexadecyl tail. 99mTc(CO)3-hexadecylamino-N,N′-diacetic acid (negatively charged), 99mTc(CO)3-hexadecylamino-N-α-picolyl-N′-acetic acid (uncharged), 99mTc(CO)3-N,N′-dipicolylhexadecylamine (positively charged), 99mTc(CO)3-N-hexadecylaminoethyl-N′-aminoethylamine (positively charged) were prepared in a radiolabeling yield: >90%. Preliminary cell uptake studies were performed in mixed blood cells with or without plasma and were compared with 99mTc-d,l-HMPAO and [18F]FDG. In plasma-free blood cells, maximum uptake (78%) was obtained for 99mTc(CO)3-N-hexadecylaminoethyl-N′-aminoethylamine after 60 min incubation (compared to 55% and 23% for 99mTc-d,l-HMPAO and [18F]FDG, respectively) while in plasma-rich medium, 99mTc(CO)3-N,N′-dipicolylhexadecylamine was best bound (54%, similar to the binding of 99mTc-d,l-HMPAO). Biodistribution in normal mice showed mainly hepatobiliary clearance of the agents and initial high lung uptake. The radiolabeled compounds showed good blood clearance with maximally 7.9% injected dose per gram at 60 min post injection. While the least lipophilic agent (99mTc(CO)3-N,N′-dipicolylhexadecylamine, log P = 1.3) showed the best cell uptake, there appears to be no direct correlation between lipophilicity and tracer uptake in mixed blood cells. In view of its comparable cell uptake to well known cell labeling agent 99mTc-d,l-HMPAO, 99mTc(CO)3-N,N′-dipicolylhexadecylamine merits further evaluation as a potential cell labeling agent. 相似文献
498.
Peter J. M. Middeldorp Maurice L. G. C. Luijten Bram A. van de Pas Miriam H. A. van Eekert Serv W. M. Kengen Gosse Schraa Alfons J. M. Stams 《Bioremediation Journal》1999,3(3):151-169
The current knowledge on microbial reductive dechlorination of chlorinated ethenes (CEs) and its application are discussed. Physiological studies on CEs dechlorinating microorganisms indicate that a distinction can be made between cometabolic dechlorination and halorespiration. Whereas cometabolic dechlorination is a coincidental and nonspecific side reaction, catalyzed by several methanogenic and acetogenic bacteria, halorespiration is a specific enzymatic reaction from which metabolic energy can be gained. In contrast to the well-studied biological dechlorination of PCE to cis-DCE, little is known about the biology of the further dechlorination from cis-DCE to ethene. Bacteria performing the latter reaction have not yet been isolated. Microbial reductive dechlorination can be applied to the in situ bioremediation of CEs contaminated sites. From laboratory and field studies, it has become clear that the dechlorination of tetrachloroethene (PCE) to cis-clichloroethene (cis-DCE) occurs rapidly and can be stimulated relatively easily. However, complete reduction to ethene appears to be a slower process that is more difficult to achieve. 相似文献
499.
Voltage-dependent anion channels (VDACs) have originally been characterized as mitochondrial porins. Starting in the late 1980s, however, evidence began to accumulate that VDACs can also be expressed in plasma membranes. In this review, we briefly revisit the historical milestones in the discovery of plasma membrane-bound VDAC, and we critically analyze the evidence for VDAC plasma membrane localization obtained from various purification strategies and recently from plasma membrane proteomics studies. We discuss the possible biological function and relevance of VDAC in the plasma membrane and finally discuss a hypothetical model of how VDAC may be targeted to the plasma membrane. 相似文献
500.
Roel J. W. Meulepas Alfons J. M. Stams Piet N. L. Lens 《Reviews in Environmental Science and Biotechnology》2010,9(1):59-78
Biological sulfate reduction can be used for the removal and recovery of oxidized sulfur compounds and metals from waste streams. However, the costs of conventional electron donors, like hydrogen and ethanol, limit the application possibilities. Methane from natural gas or biogas would be a more attractive electron donor. Sulfate reduction with methane as electron donor prevails in marine sediments. Recently, several authors succeeded in cultivating the responsible microorganisms in vitro. In addition, the process has been studied in bioreactors. These studies have opened up the possibility to use methane as electron donor for sulfate reduction in wastewater and gas treatment. However, the obtained growth rates of the responsible microorganisms are extremely low, which would be a major limitation for applications. Therefore, further research should focus on novel cultivation techniques. 相似文献