全文获取类型
收费全文 | 488篇 |
免费 | 70篇 |
国内免费 | 1篇 |
专业分类
559篇 |
出版年
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 13篇 |
2012年 | 25篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 22篇 |
2008年 | 20篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 17篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 10篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1994年 | 3篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 11篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1972年 | 7篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1968年 | 6篇 |
1967年 | 6篇 |
1966年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有559条查询结果,搜索用时 0 毫秒
111.
112.
Christine Graven Kim Brock Keith Hill David Ames Susan Cotton Lynette Joubert 《BMC neurology》2011,11(1):73
Background
There is much discourse in healthcare about the importance of client-centred rehabilitation, however in the realm of community-based therapy post-stroke there has been little investigation into the efficacy of goal-directed practice that reflects patients' valued activities. In addition, the effect of active involvement of carers in such a rehabilitation process and their subsequent contribution to functional and emotional recovery post-stroke is unclear. In community based rehabilitation, interventions based on patients' perceived needs may be more likely to alter such outcomes. In this paper, we describe the methodology of a randomised controlled trial of an integrated approach to facilitating patient goal achievement in the first year post-stroke. The effectiveness of this intervention in reducing the severity of post-stroke depression, improving participation status and health-related quality of life is examined. The impact on carers is also examined. 相似文献113.
Binding protein-independent histidine permease mutants. Uncoupling of ATP hydrolysis from transmembrane signaling 总被引:7,自引:0,他引:7
Periplasmic permeases consist of a substrate-binding receptor, located in the periplasm, and a membrane-bound complex composed of two integral membrane proteins and two nucleotide-binding proteins. The receptor interacts with the membrane-bound complex, which, upon receiving this signal, is postulated to hydrolyze ATP and translocate the substrate. We show that a class of mutations in the membrane-bound complex of the histidine permease, which allow transport in the absence of the substrate-binding protein, hydrolyze ATP independently from any signal. The data are compatible with the notion that cross-membrane signaling between the liganded periplasmic receptor and the cytoplasmic ATP-binding sites initiates conformational changes leading to ATP hydrolysis and substrate translocation. 相似文献
114.
Ames Ira H.; Hill Carol A.; Walton Daniel C.; Dashek William V. 《Plant & cell physiology》1979,20(6):1055-1061
Young seedlings of the tumor-prone amphiploid Nicotiana suaveolens? N. langsdorjfii were grown aseptically on nutrient mediumin a controlled environment chamber. At regular intervals theincidence of tumor formation was scored and plants were harvested.Total cytokinin activity was determined by means of the cucumbercotyledon bioassay, while ABA activity was measured by radioimmunoassay.A close correlation between onset of tumor formation and elevationin endogenous cytokinin activity was demonstrated, but no correlationwas observed between onset of tumorigenesis and change in thelevel of ABA. In addition, exposure of plants to exogenous ABAdid not alter therate of tumor formation. These results arediscussed in relation to the trigger mechanism for tumor inductionin the Nicotiana system.
1A preliminary report of some of this work was presented atthe American Society of Plant Physiologists meeting in June1978.
3Present address: Department of Biology, West Virginia University,Morgantown, West Virginia 26506, U.S.A. (Received March 10, 1979; ) 相似文献
115.
A I Bush R N Martins B Rumble R Moir S Fuller E Milward J Currie D Ames A Weidemann P Fischer 《The Journal of biological chemistry》1990,265(26):15977-15983
Western blots of normal human platelets, employing a monoclonal antibody raised against the full-length amyloid precursor protein of Alzheimer's disease (APP695), revealed major bands of 100-110 and 120-130 kDa in both cytosolic, membrane, and released fractions. These species were similar in size to forms seen in brain preparations and in plasma. There was no difference in Western blots of platelet preparations from Alzheimer patients compared with controls. Purified platelet amyloid precursor proteins were sequenced and shown to be amino terminally homogeneous. Immunohistochemistry localized the antigen to the platelet and megakaryocyte and demonstrated weak immunostaining of some lymphocytes. Immunoprecipitation of material released from platelets demonstrated that sedimentable full-length APP with the carboxyl-terminal epitope, and soluble APP lacking the carboxyl-terminal epitope, may exist in the circulation. Western blots and carboxyl-terminal and amino-terminal APP radioimmunoassay of material released by platelets in response to stimulation revealed that platelets release APP during degranulation. The function of platelet APP is yet to be determined, but the present studies suggest a role in regulation of the coagulation cascade or in platelet aggregation. 相似文献
116.
Gillian M. Payne Elena N. Spudich Giovanna Ferro-Luzzi Ames 《Molecular & general genetics : MGG》1985,200(3):493-496
Summary Duplicated sequences within hisM, a gene coding for a membrane-bound component of histidine transport, result in frequent deletions which, being in frame, allow production of an altered protein with aparent changed specificity of transport. While the wild-type transport system does not transport L-histidinol but does transport L-histidine and several of its analogs, the hisM deletion mutants do not transport the latter compounds but do transport L-histidinol. These results are interpreted as supporting the hypothesis (Ames and Higgins 1983) that transport through periplasmic systems involves binding of the substrate by the cytoplasmic membrane-bound components. 相似文献
117.
118.
The Effects of If‐Then Plans on Weight Loss: Results of the McGill CHIP Healthy Weight Program Randomized Controlled Trial 下载免费PDF全文
119.
The serine chemoreceptor Tsr and other methyl-accepting chemotaxis proteins (MCPs) control the swimming behaviour of Escherichia coli by generating signals that influence the direction of flagellar rotation. MCPs produce clockwise (CW) signals by stimulating the autophosphorylation activity of CheA, a cytoplasmic histidine kinase, and counter-clockwise signals by inhibiting CheA. CheW couples CheA to chemoreceptor control by promoting formation of MCP/CheW/CheA ternary complexes. To identify MCP structural determinants essential for CheA stimulation, we inserted fragments of the tsr coding region into an inducible expression vector and used a swimming contest called 'pseudotaxis' to select for transformant cells carrying CW-signalling plasmids. The shortest active fragment we found, Tsr (350–470), stimulated CheA in a CheW-dependent manner, as full-length Tsr molecules do. It spans a highly conserved 'core' (370–420) that probably specifies the CheA and CheW contact sites and other determinants needed for stimulatory control of CheA. Tsr (350–470) also carries portions of the left and right arms flanking the core, which probably play roles in regulating MCP signalling state. However, this Tsr fragment lacks all of the methylation sites characteristic of MCP molecules, indicating that methylation segments are not essential for generating receptor output signals. 相似文献
120.
A large-subunit mitochondrial ribosomal DNA sequence translocated to the nuclear genome of two stone crabs (Menippe) 总被引:1,自引:0,他引:1
Two DNA sequences that appear to be homologous to large-subunit
mitochondrial ribosomal RNA genes have been identified in the stone crabs
Menippe mercenaria and M. adina. Amplification from whole genomic DNA by
polymerase chain reaction (PCR) with oligonucleotide primers based on
conserved portions of large-subunit mitochondrial rRNA genes consistently
amplified two products of similar length (565 and 567 bp). These products
differed at 3% of their nucleotide bases, and could be distinguished by a
HindIII site. Only one of these sequences (designated the A sequence) was
detected by PCR in purified mitochondrial DNA. The other (designated the B
sequence) hybridized to total genomic DNA at a level consistent with a
nuclear genome location. It is unlikely that the type B product would have
been recognized as a nuclear copy by examination of its sequence alone.
This is the first report of a mitochondrial gene sequence translocated into
the nuclear genome of a crustacean.
相似文献