全文获取类型
收费全文 | 787篇 |
免费 | 55篇 |
国内免费 | 2篇 |
出版年
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 19篇 |
2014年 | 27篇 |
2013年 | 31篇 |
2012年 | 40篇 |
2011年 | 41篇 |
2010年 | 34篇 |
2009年 | 26篇 |
2008年 | 60篇 |
2007年 | 40篇 |
2006年 | 42篇 |
2005年 | 42篇 |
2004年 | 36篇 |
2003年 | 48篇 |
2002年 | 58篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 13篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 11篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1971年 | 6篇 |
排序方式: 共有844条查询结果,搜索用时 115 毫秒
71.
A. A. Echelle J. C. Hackler J. B. Lack S. R. Ballard J. Roman S. F. Fox D. M. LeslieJr. R. A. Van Den Bussche 《Conservation Genetics》2010,11(4):1375-1387
A previous mtDNA study indicated that female-mediated gene flow was extremely rare among alligator snapping turtle populations
in different drainages of the Gulf of Mexico. In this study, we used variation at seven microsatellite DNA loci to assess
the possibility of male-mediated gene flow, we augmented the mtDNA survey with additional sampling of the large Mississippi
River System, and we evaluated the hypothesis that the consistently low within-population mtDNA diversity reflects past population
bottlenecks. The results show that dispersal between drainages of the Gulf of Mexico is rare (F
STmsat
= 0.43, ΦSTmtDNA = 0.98). Past range-wide bottlenecks are indicated by several genetic signals, including low diversity for microsatellites
(1.1–3.9 alleles/locus; H
e = 0.06–0.53) and mtDNA (h = 0.00 for most drainages; π = 0.000–0.001). Microsatellite data reinforce the conclusion from mtDNA that the Suwannee River population might eventually
be recognized as a distinct taxonomic unit. It was the only population showing fixation or near fixation for otherwise rare
microsatellite alleles. Six evolutionarily significant units are recommended on the basis of reciprocal mtDNA monophyly and
high levels of microsatellite DNA divergence. 相似文献
72.
Khakpay R Polster D Köles L Skorinkin A Szabo B Wirkner K Illes P 《Purinergic signalling》2010,6(3):349-359
Locus coeruleus (LC) neurons in a rat brain slice preparation were superfused with a Mg2+-free and bicuculline-containing external medium. Under these conditions, glutamatergic spontaneous excitatory postsynaptic
currents (sEPSCs) were recorded by means of the whole-cell patch-clamp method. ATP, as well as its structural analogue 2-methylthio
ATP (2-MeSATP), both caused transient inward currents, which were outlasted by an increase in the frequency but not the amplitude
of the sEPSCs. PPADS, but not suramin or reactive blue 2 counteracted both effects of 2-MeSATP. By contrast, α,β-methylene
ATP (α,β-meATP), UTP and BzATP did not cause an inward current response. Of these latter agonists, only BzATP slightly facilitated
the sEPSC amplitude and strongly potentiated its frequency. PPADS and Brilliant Blue G, as well as fluorocitric acid and aminoadipic
acid prevented the activity of BzATP. Furthermore, BzATP caused a similar facilitation of the miniature (m)EPSC (recorded
in the presence of tetrodotoxin) and sEPSC frequencies (recorded in its absence). Eventually, capsaicin augmented the frequency
of the sEPSCs in a capsazepine-, but not PPADS-antagonizable, manner. In conclusion, the stimulation of astrocytic P2X7 receptors
appears to lead to the outflow of a signalling molecule, which presynaptically increases the spontaneous release of glutamate
onto LC neurons from their afferent fibre tracts. It is suggested, that the two algogenic compounds ATP and capsaicin utilise
separate receptor systems to potentiate the release of glutamate and in consequence to increase the excitability of LC neurons. 相似文献
73.
Hansen PS Brix TH Iachine I Sørensen TI Kyvik KO Hegedüs L 《American journal of physiology. Endocrinology and metabolism》2007,292(3):E765-E770
Serum thyrotropin (TSH), free thyroxine (T4), and free triiodothyronine (T3) levels illustrate the thyroid function set point, but the interrelations between these have never been characterized in detail. The aim of this study was to examine the associations between TSH and thyroid hormone levels in healthy euthyroid twins and to determine the extent to which the same genes influence more than one of these biochemical traits; 1,380 healthy euthyroid Danish twins (284 monozygotic, 286 dizygotic, 120 opposite-sex twin pairs) were recruited. Genetic and environmental associations between thyroid function measurements were examined using quantitative genetic modeling. In bivariate genetic models, the phenotypic relation between two measurements was divided into genetic and environmental correlations. Free T4 and free T3 levels were positively correlated (r=0.32, P<0.0001). The genetic correlation between serum free T4 and free T3 levels was rg=0.25 (95% CI 0.14-0.35), suggesting that a set of common genes affect both phenotypes (pleiotropy). The correlation between the environmental effects was re=0.41 (0.32-0.50). From this we calculated that the proportion of the correlation between free T4 and free T3 levels mediated by common genetic factors was 48%. Only 7% of the genetic component of serum free T3 levels is shared with serum free T4. Serum TSH and thyroid hormone levels did not share any genetic influences. In conclusion, thyroid hormone levels are partly genetically correlated genes that affect free T4 levels and exert pleiotropic effects on free T3 levels, although most of the genetic variance for these measurements is trait specific. 相似文献
74.
Characteristics of reactive oxygen species (ROS) production in isolated guinea-pig brain mitochondria respiring on alpha-glycerophosphate (alpha-GP) were investigated and compared with those supported by succinate. Mitochondria established a membrane potential (DeltaPsi(m)) and released H(2)O(2) in parallel with an increase in NAD(P)H fluorescence in the presence of alpha-GP (5-40 mm). H(2)O(2) formation and the increase in NAD(P)H level were inhibited by rotenone, ADP or FCCP, respectively, being consistent with a reverse electron transfer (RET). The residual H(2)O(2) formation in the presence of FCCP was stimulated by myxothiazol in mitochondria supported by alpha-GP, but not by succinate. ROS under these conditions are most likely to be derived from alpha-GP-dehydrogenase. In addition, huge ROS formation could be provoked by antimycin in alpha-GP-supported mitochondria, which was prevented by myxothiazol, pointing to the generation of ROS at the quinol-oxidizing center (Q(o)) site of complex III. FCCP further stimulated the production of ROS to the highest rate that we observed in this study. We suggest that the metabolism of alpha-GP leads to ROS generation primarily by complex I in RET, and in addition a significant ROS formation could be ascribed to alpha-GP-dehydrogenase in mammalian brain mitochondria. ROS generation by alpha-GP at complex III is evident only when this complex is inhibited by antimycin. 相似文献
75.
Dual effect of acid pH on purinergic P2X3 receptors depends on the histidine 206 residue 总被引:1,自引:0,他引:1
Gerevich Z Zadori ZS Köles L Kopp L Milius D Wirkner K Gyires K Illes P 《The Journal of biological chemistry》2007,282(47):33949-33957
Whole cell patch clamp investigations were carried out to clarify the pH sensitivity of native and recombinant P2X(3) receptors. In HEK293 cells permanently transfected with human (h) P2X(3) receptors (HEK293-hP2X(3) cells), an acidic pH shifted the concentration-response curve for alpha,beta-methylene ATP (alpha,beta-meATP) to the right and increased its maximum. An alkalic pH did not alter the effect of alpha,beta-meATP. Further, a low pH value increased the activation time constant (tau(on)) of the alpha,beta-meATP current; the fast and slow time constants of desensitization (tau(des1), tau(des2)) were at the same time also increased. Finally, acidification accelerated the recovery of P2X(3) receptors from the desensitized state. Replacement of histidine 206, but not histidine 45, by alanine abolished the pH-induced effects on hP2X(3) receptors transiently expressed in HEK293 cells. Changes in the intracellular pH had no effect on the amplitude or time course of the alpha,beta-meATP currents. The voltage sensitivity and reversal potential of the currents activated by alpha,beta-meATP were unaffected by extracellular acidification. Similar effects were observed in a subpopulation of rat dorsal root ganglion neurons expressing homomeric P2X(3) receptor channels. It is suggested that acidification may have a dual effect on P2X(3) channels, by decreasing the current amplitude at low agonist concentrations (because of a decrease in the rate of activation) and increasing it at high concentrations (because of a decrease in the rate of desensitization). Thereby, a differential regulation of pain sensation during e.g. inflammation may occur at the C fiber terminals of small DRG neurons in peripheral tissues. 相似文献
76.
de Torres-Zabala M Truman W Bennett MH Lafforgue G Mansfield JW Rodriguez Egea P Bögre L Grant M 《The EMBO journal》2007,26(5):1434-1443
We have found that a major target for effectors secreted by Pseudomonas syringae is the abscisic acid (ABA) signalling pathway. Microarray data identified a prominent group of effector-induced genes that were associated with ABA biosynthesis and also responses to this plant hormone. Genes upregulated by effector delivery share a 42% overlap with ABA-responsive genes and are also components of networks induced by osmotic stress and drought. Strongly induced were NCED3, encoding a key enzyme of ABA biosynthesis, and the abscisic acid insensitive 1 (ABI1) clade of genes encoding protein phosphatases type 2C (PP2Cs) involved in the regulation of ABA signalling. Modification of PP2C expression resulting in ABA insensitivity or hypersensitivity led to restriction or enhanced multiplication of bacteria, respectively. Levels of ABA increased rapidly during bacterial colonisation. Exogenous ABA application enhanced susceptibility, whereas colonisation was reduced in an ABA biosynthetic mutant. Expression of the bacterial effector AvrPtoB in planta modified host ABA signalling. Our data suggest that a major virulence strategy is effector-mediated manipulation of plant hormone homeostasis, which leads to the suppression of defence responses. 相似文献
77.
Kis Z Sas K Gyulai Z Treso B Petrovay F Kapusinszky B Csire M Endresz V Burian K Mandi Y Vecsei L Gonczol E 《The new microbiologica》2007,30(3):213-220
The aim of this study was to examine whether chronic infections and genetic factors of the host play roles in the pathophysiology of acute noncardioembolic ischemic stroke. Blood samples from 59 subjects with ischemic stroke and 52 control patients were investigated by nested PCR for the presence of C. pneumoniae DNA, HCMV DNA and enterovirus RNA, by ELISA for the levels of antibodies to C. pneumoniae, HCMV, HSV, HHV-6, EBV and the inflammatory chemokine IL-8, and by PCR for promoter polymorphism of the IL-8 and CD14 host genes. Associations of stroke with the HCMV IgG and HSV-1 IgA antibody levels were observed. No association of stroke was detected with the presence of C. pneumoniae, HCMV or enterovirus nucleic acids in the peripheral blood, C. pneumoniae IgM, IgG and IgA, the HSV IgG, the EBV IgG, or HHV-6 IgG antibody levels, the pathogen burden, the IL-8 or CD14 promoter polymorphisms, or with the serum levels of IL-8 in the overall study population. These results are consistent with the hypothesis that certain pathogens are involved in the development of ischemic stroke. 相似文献
78.
Oszvald M Kang TJ Tomoskozi S Tamas C Tamas L Kim TG Yang MS 《Molecular biotechnology》2007,35(3):215-223
Epitopes often require co-delivery with adjuvant and targeting proteins to enable recognition by the immune system, and this approach may also increase the efficacy of the antigen. In this study, we assess and describe the ability of transgenic rice plants to express a fusion protein consisting of the B-subunit of the Escherichia coli heat-labile enterotoxin (LTB) and a synthetic core-neutralizing epitope (COE) of porcine epidemic diarrhea virus (PEDV), inducing an enteric disease that is seen most predominantly in piglets. Both components of the fusion proteins were detected with Western blot analysis. The fusion protein was determined to assemble into pentamers, as was evidenced by its ability to bind to GM1 gangliosides, and evidenced an average level of expression in a transgenic rice endosperm. This indicates that the expression system of the plant is capable of generating a sizable amount of antigen, possibly allowing for the successful development of an edible vaccine. 相似文献
79.
80.