全文获取类型
收费全文 | 135篇 |
免费 | 6篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 12篇 |
2013年 | 11篇 |
2012年 | 10篇 |
2011年 | 6篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 12篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有141条查询结果,搜索用时 46 毫秒
1.
Effect of postnatal development on calcium currents and slow charge movement in mammalian skeletal muscle 总被引:16,自引:3,他引:13
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Single- (whole-cell patch) and two-electrode voltage-clamp techniques were used to measure transient (Ifast) and sustained (Islow) calcium currents, linear capacitance, and slow, voltage-dependent charge movements in freshly dissociated fibers of the flexor digitorum brevis (FDB) muscle of rats of various postnatal ages. Peak Ifast was largest in FDB fibers of neonatal (1-5 d) rats, having a magnitude in 10 mM external Ca of 1.4 +/- 0.9 pA/pF (mean +/- SD; current normalized by linear fiber capacitance). Peak Ifast was smaller in FDB fibers of older animals, and by approximately 3 wk postnatal, it was so small as to be unmeasurable. By contrast, the magnitudes of Islow and charge movement increased substantially during postnatal development. Peak Islow was 3.6 +/- 2.5 pA/pF in FDB fibers of 1-5-d rats and increased to 16.4 +/- 6.5 pA/pF in 45-50-d-old rats; for these same two age groups, Qmax, the total mobile charge measurable as charge movement, was 6.0 +/- 1.7 and 23.8 +/- 4.0 nC/microF, respectively. As both Islow and charge movement are thought to arise in the transverse-tubular system, linear capacitance normalized by the area of fiber surface was determined as an indirect measure of the membrane area of the t-system relative to that of the fiber surface. This parameter increased from 1.5 +/- 0.2 microF/cm2 in 2-d fibers to 2.9 +/- 0.4 microF/cm2 in 44-d fibers. The increases in peak Islow, Qmax, and normalized linear capacitance all had similar time courses. Although the function of Islow is unknown, the substantial postnatal increase in its magnitude suggests that it plays an important role in the physiology of skeletal muscle. 相似文献
2.
A. Magalhaes B. Maigret J. Hoflack J. N. F. Gomes H. A. Scheraga 《Journal of Protein Chemistry》1994,13(2):195-215
Although the majority of the ion pairs found in proteins consists of two charges of opposite sign, the observation of some unusual arrangements of two arginines led us to a search of such occurrences in the Brookhaven Protein Data Bank. We have found 41 Arginine-Arginine interactions with a C...C distance less than 5 å. Computer graphics analysis of these structures shows that most of the Arg-Arg pairs are found in the vicinity of the surface of the proteins, in an easily hydrated region. In order to determine which factors could stabilize such arrangements of species of similar charge, we have carried out AM1 semi-empirical calculations on a model of two guanidinium ions surrounded by several water molecules. The results show the existence of stable clusters with six or more water molecules, with distances between C atoms around 3 å. The bridging role of the water molecules is an important structural and energetic feature and we find bridges of two and three molecules between the guanidinium ions. These results are in good agreement with the structures found in our search of the experimental data. Enhancement of the electrostatic potential around these clusters, when compared to one of the guanidinium ions alone, is also demonstrated. 相似文献
3.
Molecular evolution of voltage-sensitive ion channel genes: on the origins of electrical excitability 总被引:14,自引:0,他引:14
We have analyzed nucleic acid and amino acid sequence alignments of a
variety of voltage-sensitive ion channels, using several methods for
phylogenetic tree reconstruction. Ancient duplications within this family
gave rise to three distantly related groups, one consisting of the Na+ and
Ca++ channels, another the K+ channels, and a third including the cyclic
nucleotide-binding channels. A series of gene duplications produced at
least seven mammalian homologues of the Drosophila Shaker K+ channel;
clones of only three of these genes are available from all three mammalian
species examined (mouse, rat, and human), pointing to specific genes that
have yet to be recovered in one or another of these species. The
Shaw-related K+ channels and the Na+ channel family have also undergone
considerable expansion in mammals, relative to flies. These expansions
presumably reflect the needs of the high degree of physiological and
neuronal complexity of mammals. Analysis of the separate domains of the
four-domain channels (Ca++ and Na+) supports their having evolved by two
sequential gene duplications and implies the historical existence of a
functional two-domain channel.
相似文献
4.
Prashant G. Bhat Ajay M. V. Kumar Balaji Naik Srinath Satyanarayana Deepak KG Sreenivas A. Nair Suryakanth MD Einar Heldal Donald A. Enarson Anthony J. Reid 《PloS one》2013,8(12)
Background
Severe acute malnutrition (SAM) is the most serious form of malnutrition affecting children under-five and is associated with many infectious diseases including Tuberculosis (TB). In India, nutritional rehabilitation centres (NRCs) have been recently established for the management of SAM including TB. The National TB Programme (NTP) in India has introduced a revised algorithm for diagnosing paediatric TB. We aimed to examine whether NRCs adhered to these guidelines in diagnosing TB among SAM children.Methods
A cross-sectional study involving review of records of all SAM children identified by health workers during 2012 in six tehsils (sub-districts) with NRCs (population: 1.8 million) of Karnataka, India.Results
Of 1927 identified SAM children, 1632 (85%) reached NRCs. Of them, 1173 (72%) were evaluated for TB and 19(2%) were diagnosed as TB. Of 1173, diagnostic algorithm was followed in 460 (37%). Among remaining 763 not evaluated as per algorithm, tuberculin skin test alone was conducted in 307 (41%), chest radiography alone in 99 (13%) and no investigations in 337 (45%). The yield of TB was higher among children evaluated as per algorithm (4%) as compared to those who were not (0.3%) (OR: 15.3 [95%CI: 3.5-66.3]). Several operational challenges including non-availability of a full-time paediatrician, non-functioning X-ray machine due to frequent power cuts, use of tuberculin with suboptimal strength and difficulties in adhering to a complex diagnostic algorithm were observed.Conclusion
This study showed that TB screening in NRCs was sub-optimal in Karnataka. Some children did not reach the NRC, while many of those who did were either not or sub-optimally evaluated for TB. This study pointed to a number of operational issues that need to be addressed if this collaborative strategy is to identify more TB cases amongst malnourished children in India. 相似文献5.
6.
G.C. Micke T.M. Sullivan R.J. Soares Magalhaes P.J. Rolls S.T. Norman V.E.A. Perry 《Animal reproduction science》2010,117(1-2):1-10
Maternal nutrient intake during gestation can alter fetal growth. Whilst this has been studied extensively in the sheep, less is known about effects in the bovine. Composite-breed beef heifers were allocated to either a high (H/? = 76 MJ metabolisable energy (ME) and 1.4 kg crude protein (CP)) or low (L/? = 62 MJ ME and 0.4 kg CP daily) nutritional treatment at artificial insemination. Half of each nutritional group changed to an opposite nutritional group at the end of the first trimester (?/H = 82 MJ ME and 1.4 kg CP; ?/L = 62 MJ ME and 0.4 kg CP daily), resulting in 4 treatment groups: HH (n = 16); HL (n = 19); LH (n = 17); LL (n = 19). During the third trimester all heifers were fed the same diets. Fetuses were measured at 4-weekly intervals beginning at day 39 of gestation. Calves were also measured at birth for physical body variables. Low maternal nutrient intake was associated with decreased crown-rump length at day 39 (P < 0.01) and increased thoracic diameter at day 95 (P < 0.01). Umbilical cord diameter was reduced in L/? fetuses in the first trimester (P < 0.05) but was greater in ?/L fetuses in the second trimester compared to their respective H counterparts (P < 0.05). Calf birth weight was decreased in association with ?/L maternal diets (P < 0.05). In conclusion, fetal development of cattle may be affected by maternal nutrition as early as day 39 of gestation. This may be followed by either compensatory fetal growth, or alternatively, preferential fetal tissue growth that is dependant upon maternal nutrition. Clearly, calf birth weight may be altered by maternal nutrition during mid-gestation. 相似文献
7.
Physiological basis of reduced Al tolerance in ditelosomic lines of Chinese Spring wheat 总被引:13,自引:0,他引:13
Aluminum tolerance was assessed in the moderately Al-tolerant wheat (Triticum aestivum L.) cultivar Chinese Spring and a set of ditelosomic lines derived from Chinese Spring. Three ditelosomic lines lacking chromosome
arms 4DL, 5AS and 7AS, respectively, exhibited decreased Al tolerance relative to the euploid parent Chinese Spring based
on reduced root growth in Al-containing solutions. The physiological basis of the reduced Al tolerance was investigated. Measurements
by inductively coupled argon plasma mass spectroscopy of root apical Al accumulation demonstrated that two of these three
lines had a decreased ability to exclude Al from the root apex, the site of Al phytotoxicity. As Al-induced malate exudation
has been suggested to be an important physiological mechanism of Al tolerance in wheat, this parameter was quantified and
malate exudation was shown to be smaller in all three deletion lines compared with Chinese Spring. These results suggest that
the decreased Al tolerance in at least two of the three ditelosomic lines is due to the loss of different genes independently
influencing a single Al-tolerance mechanism, rather than to the loss of genes encoding alternative Al-tolerance mechanisms.
Received: 3 July 2000 / Accepted: 9 August 2000 相似文献
8.
Spada RG da Silva D Abdel-Hamid AZ Sobral-Hamaguchi SS Zuim NR Zanotti-Magalhaes EM Magalhaes LA Ribeiro-Paes JT 《Memórias do Instituto Oswaldo Cruz》2002,97(Z1):53-58
The analysis of the genetic variability related to susceptibility to Schistosoma mansoni infection in the vector of the genus Biomphalaria is important in terms of a better understanding of the epidemiology of schistosomiasis itself, the possible pathological implications of this interaction in vertebrate hosts, and the formulation of new strategies and approaches for disease control. In the present study, the genetic variability of B. glabrata strains found to be resistant or susceptible to S. mansoni infection was investigated using DNA amplification by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). The amplification products were analyzed on 8% polyacrylamide gel and stained with silver. We selected 10 primers, since they have previously been useful to detect polymorphism among B. glabrata and/or B. tenagophila. The results showed polymorphisms with 5 primers. Polymorphic bands observed only in the susceptible strain. The RAPD-PCR methodology represents an adequate approach for the analysis of genetic polymorphisms. The understanding of the genetic polymorphisms associated to resistance may contribute to the future identification of genomic sequences related to the resistance/susceptibility of Biomphalaria to the larval forms of S. mansoni and to the development of new strategies for the control of schistosomiasis. 相似文献
9.
Felicori LF Souza CT Velarde DT Magalhaes A Almeida AP Figueiredo S Richardson M Diniz CR Sanchez EF 《Protein expression and purification》2003,30(1):32-42
A kallikrein-like proteinase of Lachesis muta muta (bushmaster) venom, designated LV-Ka, was purified by gel filtration and anion exchange chromatographies. Physicochemical studies indicated that the purified enzyme is a 33 kDa monomeric glycoprotein, the Mr of which fell to 28 kDa after deglycosylation with PNGase F. Approximately 77% of the protein sequence was determined by sequencing the various fragments derived from digestions with endoproteases. The partial sequence obtained suggests that LV-Ka is of a similar size to other serine proteinases (i.e., approximately 234 amino acid residues). Sequence studies on the NH2-terminal region of the protein indicate that LV-Ka shares a high degree of sequence homology with the kallikrein-like enzymes EI and EII from Crotalus atrox, with crotalase from Crotalus adamanteus and significant homology with other serine proteinases from snake venoms and vertebrate serum enzymes. LV-Ka showed kallikrein-like activity, releasing bradikinin from kininogen as evidenced by guinea pig bioassay. In addition, intravenous injection of the proteinase (0.8 microg/g) was shown to lower blood pressure in experimental rats. In vitro, the isolated proteinase was shown to have neither fibrin(ogeno)lytic activity nor coagulant effect. LV-Ka was active upon the kallikrein substrates S-2266 and S-2302 (specific activity=13.0 and 31.5 U/mg, respectively; crude venom=0.25 and 6.0 U/mg) but had no proteolytic effect on dimethylcasein and insulin B chain. Its enzymatic activity was inhibited by NPGB and PMSF, indicating that the enzyme is a serine proteinase. Interestingly, one of the other reactions catalyzed by plasma kallikrein, the activation of plasminogen was one of the activities exhibited by LV-Ka. 相似文献