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排序方式: 共有98条查询结果,搜索用时 343 毫秒
41.
Variation in meiotic recombination frequencies among human males 总被引:11,自引:0,他引:11
Meiotic recombination is essential for the segregation of homologous chromosomes and the formation of normal haploid gametes. Little is known about patterns of meiotic recombination in human germ cells or the mechanisms that control these patterns. Here, newly developed immunofluorescence techniques, based on the detection of MLH1 (a DNA mismatch repair protein) foci on synaptonemal complexes (SCs) at prophase I of meiosis, were used to examine recombination in human spermatocytes. The mean number of MLH1 foci per cell in all donors was 48.0 with range from 21 to 65. Remarkable variation in the recombination frequency was noted among 11 normal individuals: the mean frequencies of chromosomal recombination foci ranged from a low of 42.5 to a high of 55.0 exchanges. Donor age did not contribute to this variation. There was no correlation between this variation and the frequency of gaps (discontinuities) or splits (unpaired chromosome regions) in the SCs. The mean percentage of cells with gaps was 35% (range: 20% to 58%) and with splits was 7% (range: 0% to 37%). Bivalents without a recombination focus were rare, with a frequency of only 0.3%. Thus, achiasmate chromosomes appear to be rare in human male meiosis. 相似文献
42.
Histone H1 phosphorylation was examined during embryonic development of Drosophila hydei. A changing pattern of H1 phosphorylation upon separation on an acid-urea polyacrylamide gel was observed in the course of Drosophila embryogenesis. It is considered to be related to the decrease of the mitotic activity of the cells as development proceeds. 相似文献
43.
Maria Sporbert Petr Keil Gunnar Seidler Helge Bruelheide Ute Jandt Svetlana Aćić Idoia Biurrun Juan Antonio Campos Andraž Čarni Milan Chytrý Renata Ćušterevska Jürgen Dengler Valentin Golub Florian Jansen Anna Kuzemko Jonathan Lenoir Corrado Marcenò Jesper Erenskjold Moeslund Aaron Pérez-Haase Solvita Rūsiņa Urban Šilc Ioannis Tsiripidris Vigdis Vandvik Kiril Vasilev Risto Virtanen Erik Welk 《Journal of Biogeography》2020,47(10):2210-2222
44.
Kiril Mishev Detelin Stefanov Kalina Ananieva Chavdar Slavov Evguéni D. Ananiev 《Plant Growth Regulation》2009,58(1):61-71
Darkness mediates different senescence-related responses depending on the targeting of dark treatment (whole plants or individual
leaves) and the organs that perceive the signal (leaves or cotyledons). In this study, we presented data on the differential
effects of 2-day dark treatment on progression of senescence in cotyledons and primary leaves of 14-day-old plants of Cucurbita pepo L. (zucchini). The lack of changes in chlorophyll a, chlorophyll b and carotenoid contents as well as in the PSI activity measured by the far-red induced alterations in the P700 oxidation levels and the quantum yield of electron transport from Q
A
− to PSI end acceptors () indicated higher resistance of cotyledons to the applied dark stress compared to the primary leaves. In contrast to cotyledons,
PSI activity in the primary leaves was significantly inhibited. Concerning the activity of PSII analyzed by the changes in
the JIP-test parameters (the maximal efficiency of PSII photochemistry, ; the performance index, PIABS; the efficiency of Q
A
− reoxidation, ψ
0 and the effective dissipation per reaction center, DI0/RC), no differences were observed between cotyledons and primary leaves, thus suggesting that PSI activity in the true leaves
was more susceptible to the applied dark stress. The transfer of the darkened plants to normal light regime resulted in delayed
senescence in cotyledons which was in contrast to results on Arabidopsis, thus implying the existence of specific mechanisms of cotyledon senescence in different monocarpic plants. 相似文献
45.
Adriana Bakalova Hristo Varbanov Stancho Stanchev Darvin Ivanov 《Inorganica chimica acta》2010,363(7):1568-1576
Platinum(II) and platinum(IV) complexes with 3-amino-5-methyl-5-(4-pyridyl)-2,4-imidazolidenedione (L) with general formulaе cis-[PtL2X2]·nH2O and [PtL2Cl4], where X = Cl−, Br−, I− and n = 2-4) were synthesized. The novel compounds were fully characterized by elemental analysis, IR, 1H, 13C, 195Pt NMR spectra, thermal analysis and molar conductivity. The geometry of Pt(II) complexes and of the organic ligand in the gas phase were optimized using the hybrid DFT method B3LYP with LANL2DZ and 6-31G** basis sets. Some physicochemical parameters as dipole moment, HOMO, LUMO energies and ESP charges were calculated. The comparison of the bond length and angles, obtained from the X-ray analysis and DFT calculations is realized. The cytotoxic effects of these complexes in human T-cell leukemia KE-37 (SKW-3) are reported. 相似文献
46.
47.
Mitko Mladenov Vase Tanska Tanja Vitkovska Icko Gjorgoski Suzana Dinevska-Kofkarovska Trajce Stafilov Kiril Hristov Desislava Duridanova 《Journal of thermal biology》2008,33(8):431-436
Molecular mechanisms responsible for age-dependent deterioration of biochemical functions have not been completely revealed as yet. We studied the role of ascorbic acid food supplementation in young and aged acute heat-exposed rats. The duration of heat exposure (40±0.5 °C) for heat-exposed Wistar rats, at the age of 35 days and 22–24 months, was approximately 2 h. In the aged heat-unexposed animals cholesterol and triglycerides were considerably high, whereas tissues ascorbic acid, glutathione and methylglyoxal were significantly low. Administration of vitamin C reverted these age-associated differences to the status comparable to young rats. The role of vitamin C supplementation was almost the same in young heat-exposed animals. In this direction in young rats suppression of LTC4 synthesis is evident during acute heat exposure as a result of vitamin C treatment. The importance of vitamin C treatment for young heat-exposed rats is in the protection of apoptosis, if it is determined across the LTC4 changes. In contrary, in old heat-exposed rats, vitamin C does not suppress the apoptotic processes. The results suggest that oxidative and apoptotic processes in the liver and the kidney as a result of the acute heat exposure is presumably subject of ascorbic acid deficiency. 相似文献
48.
Angelina Rakovska Janos P. Kiss Peter Raichev Maria Lazarova Reni Kalfin Kiril Milenov 《Neurochemistry international》2002,40(3):269-275
The modulation of striatal cholinergic neurons by somatostatin (SOM) was studied by measuring the release of acetylcholine (ACh) in the striatum of freely moving rats. The samples were collected via a transversal microdialysis probe. ACh level in the dialysate was measured by the high performance liquid chromatography method with an electrochemical detector. Local administration of SOM (0.1, 0.5 and 1 microM) produced a long-lasting and concentration-dependent increase in the basal striatal ACh output. The stimulant effect of SOM was antagonized by the SOM receptor antagonist cyclo(7-aminopentanoyl-Phe-D-Trp-Lys-Thr[BZL]) (1 microM). In a series of experiments, we studied the effect of 6,7-dinitroquinoxaline-2, 3-dione (DNQX), a selective non-NMDA (N-methyl-D-aspartate) glutamatergic antagonist, on the basal and SOM-induced ACh release from the striatum. DNQX, 2 microM, perfused through the striatum had no effect on the basal ACh output but inhibited the SOM (1 microM)-induced ACh release. The non-NMDA glutamatergic receptor antagonist 1-(4-aminophenyl)-4-methyl-7,8-methylendioxy-5H-2,3- benzodiazepine (GYKI-52466), 10 microM, antagonized the SOM (1 microM)-induced release of ACh in the striatum. Local administration of the NMDA glutamatergic receptor antagonist, 2-amino-5-phosphonopentanoic acid (APV), 100 microM, blocked SOM (1 microM)-evoked ACh release. Local infusion of tetrodotoxin (1 microM) decreased the basal release of ACh and abolished the 1 microM SOM-induced increase in ACh output suggesting that the stimulated release of ACh depends on neuronal firing. The present results are the first to demonstrate a neuromodulatory role of SOM in the regulation of cholinergic neuronal activity of the striatum of freely moving rats. The potentiating effect of SOM on ACh release in the striatum is mediated (i) by SOM receptor located on glutamatergic nerve terminals, and (ii) by NMDA and non-NMDA glutamatergic receptors located on dendrites of cholinergic interneurones of the striatum. 相似文献
49.
Wolfgang Willner Borja Jiménez‐Alfaro Emiliano Agrillo Idoia Biurrun Juan Antonio Campos Andraž Čarni Laura Casella János Csiky Renata Ćušterevska Yakiv P. Didukh Jörg Ewald Ute Jandt Florian Jansen Zygmunt Kącki Ali Kavgacı Jonathan Lenoir Aleksander Marinšek Viktor Onyshchenko John S. Rodwell Joop H.J. Schaminée Jozef Šibík Željko Škvorc Jens‐Christian Svenning Ioannis Tsiripidis Pavel Dan Turtureanu Rossen Tzonev Kiril Vassilev Roberto Venanzoni Thomas Wohlgemuth Milan Chytrý 《应用植被学》2017,20(3):494-512
50.
Hristov KL Cui X Brown SM Liu L Kellett WF Petkov GV 《American journal of physiology. Cell physiology》2008,295(5):C1344-C1353
We investigated the role of large-conductance Ca(2+)-activated K(+) (BK) channels in beta3-adrenoceptor (beta3-AR)-induced relaxation in rat urinary bladder smooth muscle (UBSM). BRL 37344, a specific beta3-AR agonist, inhibits spontaneous contractions of isolated UBSM strips. SR59230A, a specific beta3-AR antagonist, and H89, a PKA inhibitor, reduced the inhibitory effect of BRL 37344. Iberiotoxin, a specific BK channel inhibitor, shifts the BRL 37344 concentration response curves for contraction amplitude, net muscle force, and tone to the right. Freshly dispersed UBSM cells and the perforated mode of the patch-clamp technique were used to determine further the role of beta3-AR stimulation by BRL 37344 on BK channel activity. BRL 37344 increased spontaneous, transient, outward BK current (STOC) frequency by 46.0 +/- 20.1%. In whole cell mode at a holding potential of V(h) = 0 mV, the single BK channel amplitude was 5.17 +/- 0.28 pA, whereas in the presence of BRL 37344, it was 5.55 +/- 0.41 pA. The BK channel open probability was also unchanged. In the presence of ryanodine and nifedipine, the current-voltage relationship in response to depolarization steps in the presence and absence of BRL 37344 was identical. In current-clamp mode, BRL 37344 caused membrane potential hyperpolarization from -26.1 +/- 2.1 mV (control) to -29.0 +/- 2.2 mV. The BRL 37344-induced hyperpolarization was eliminated by application of iberiotoxin, tetraethylammonium or ryanodine. The data indicate that stimulation of beta3-AR relaxes rat UBSM by increasing the BK channel STOC frequency, which causes membrane hyperpolarization and thus relaxation. 相似文献