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241.
Although some species of Annelida have an enormous capacity to regenerate, it is not yet known whether reestablishment of lost body parts is performed by stem cells, depends on preceding dedifferentiation of somatic cells, or is a combination of both. In order to clarify how, in the case of epimorphic regeneration, the blastemas are formed, we applied the thymidine analog 5'-bromo-2'-deoxyuridine (BrdU) in the dorvilleid polychaete Dorvillea bermudensis to identify cells in the S-phase of the cell cycle. Regeneration pulse-chase experiments were carried out to determine onset and dynamics of the proliferation process, and BrdU pulse-chase experiments were undertaken to follow cell fate. We found irregularly distributed S-phase cells throughout the body of adult specimens. Subsequent to amputation, these cells do not migrate from the amputee towards the wound site, where proliferation activity was documented no earlier than 16 h after fragmentation. In the initial phase, the proliferation rate at the anterior end exceeds the rate at the posterior end. Observance of identity could be demonstrated for the ectoderm and can be assumed for the two other germ layers. The anterior blastema transforms into the head, while the posterior forms the pygidium and persists as a proliferation zone; four or numerous segments are formed by intercalation between the former anterior or posterior blastema and the amputee. 相似文献
242.
Annika Wiemann Liselotte W. Andersen Per Berggren Ursula Siebert Harald Benke Jonas Teilmann Christina Lockyer Iwona Pawliczka Krzysztof Skóra Anna Roos Thomas Lyrholm Kirsten B. Paulus Valerio Ketmaier Ralph Tiedemann 《Conservation Genetics》2010,11(1):195-211
The population status of the harbour porpoise (Phocoena phocoena) in the Baltic area has been a continuous matter of debate. Here we present the by far most comprehensive genetic population structure assessment to date for this region, both with regard to geographic coverage and sample size: 497 porpoise samples from North Sea, Skagerrak, Kattegat, Belt Sea, and Inner Baltic Sea were sequenced at the mitochondrial Control Region and 305 of these specimens were typed at 15 polymorphic microsatellite loci. Samples were stratified according to sample type (stranding vs. by-caught), sex, and season (breeding vs. non-breeding season). Our data provide ample evidence for a population split between the Skagerrak and the Belt Sea, with a transition zone in the Kattegat area. Among other measures, this was particularly visible in significant frequency shifts of the most abundant mitochondrial haplotypes. A particular haplotype almost absent in the North Sea was the most abundant in Belt Sea and Inner Baltic Sea. Microsatellites yielded a similar pattern (i.e., turnover in occurrence of clusters identified by STRUCTURE). Moreover, a highly significant association between microsatellite assignment and unlinked mitochondrial haplotypes further indicates a split between North Sea and Baltic porpoises. For the Inner Baltic Sea, we consistently recovered a small, but significant separation from the Belt Sea population. Despite recent arguments that separation should exceed a predefined threshold before populations shall be managed separately, we argue in favour of precautionary acknowledging the Inner Baltic porpoises as a separate management unit, which should receive particular attention, as it is threatened by various factors, in particular local fishery measures. 相似文献
243.
Many problems concerning the work of anaesthesist and intensivist are evocated during the management of ECMO: indication, optimisation of artificial ventilation during ECMO, transportation of the patient and complications.The criteria of indication are now best known, but the vascular access (veino-venous or arterio-venous) are discussed depending of cardiac echographic evaluation but also splanchnic consequences. Artificial ventilation modalities are not completly validated and probably need a better individual exploration at bed. 相似文献
244.
The present study was to investigate the effects and action mechanisms of dehydroepiandrosterone (DHEA) on steroidogenesis
in rat adrenal zona glomerulosa cells (ZG). ZG cells were incubated with DHEA in the presence or absence of angiotensin II
(AngII), a high concentration of potassium, 8-Br-cAMP, forskolin, 25-OH-cholesterol, pregnenolone, progesterone, deoxycorticosterone,
corticosterone, A23187, or cyclopiazonic acid (CPA) at 37°C for 1 h. The concentration of aldosterone or pregnenolone in the
culture medium was then measured by radioimmunoassay (RIA). The cells were used to determine the cellular cAMP content. The
data demonstrated that: (1) DHEA inhibited AngII-, high concentration of KCl-, forskolin-, 8-Br-cAMP-, 25-OH-cholesterol-,
pregnenolone-, progesterone-, deoxycorticosterone-, corticosterone-, A23187-, or CPA-stimulated aldosterone release; (2) DHEA
increased 25-OH-cholesterol-stimulated pregnenolone release but not when 25-OH-cholesterol was combined with trilostane; (3)
DHEA noncompetitively inhibited aldosterone synthase but showed uncompetitive inhibition of P450scc. These results suggest
that DHEA acts directly on rat ZG cells to diminish aldosterone secretion by inhibition of a post-cAMP pathway or by acting
on intracellular Ca2+ mobilization. In addition it affects the function of post-P450scc steroidogenic enzymes.
Ling-Ling Chang and Paulus S. Wang contributed equally to this work. 相似文献
245.
Fabiano Severo Rodembusch Fernando Paulus Leusin Luis Fernando da Costa Medina Adriano Brandelli Valter Stefani 《Photochemical & photobiological sciences》2005,4(3):254-259
Three new benzazole isothiocyanate fluorescent dyes, 2-(4'-isothiocyanate-2'-hydroxyphenyl)benzoxazole, 2-(4'-isothiocyanate-2'-hydroxyphenyl)benzothiazole and 2-(4'-isothiocyanate-2'-hydroxyphenyl)benzimidazole were synthesised, purified until optical purity grade and characterised by spectroscopic techniques. UV/VIS and steady-state fluorescence were also applied to characterise the photophysical behaviour of the dyes. These dyes exhibit an intense fluorescence emission with a large Stokes shift, inherent to the class of benzazoles which relax by the excited state intramolecular proton transfer (ESIPT) mechanism. The dyes were studied for labeling bovine serum albumin (BSA), resulting conjugates BSA-dye with a remarkable photostability under UV/VIS radiation in relation to classical protein labels. The resulting conjugates presented fluorescence in the blue-green region. Direct fluorescence detection of protein-labeled with those dyes after polyacrylamide gel electrophoresis indicates their potential use as fluorescent probes for proteins. 相似文献
246.
Three genome-wide association studies and a linkage analysis identify HERC2 as a human iris color gene
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Kayser M Liu F Janssens AC Rivadeneira F Lao O van Duijn K Vermeulen M Arp P Jhamai MM van Ijcken WF den Dunnen JT Heath S Zelenika D Despriet DD Klaver CC Vingerling JR de Jong PT Hofman A Aulchenko YS Uitterlinden AG Oostra BA van Duijn CM 《American journal of human genetics》2008,82(2):411-423
Human iris color was one of the first traits for which Mendelian segregation was established. To date, the genetics of iris color is still not fully understood and is of interest, particularly in view of forensic applications. In three independent genome-wide association (GWA) studies of a total of 1406 persons and a genome-wide linkage study of 1292 relatives, all from the Netherlands, we found that the 15q13.1 region is the predominant region involved in human iris color. There were no other regions showing consistent genome-wide evidence for association and linkage to iris color. Single nucleotide polymorphisms (SNPs) in the HERC2 gene and, to a lesser extent, in the neighboring OCA2 gene were independently associated to iris color variation. OCA2 has been implicated in iris color previously. A replication study within two populations confirmed that the HERC2 gene is a new and significant determinant of human iris color variation, in addition to OCA2. Furthermore, HERC2 rs916977 showed a clinal allele distribution across 23 European populations, which was significantly correlated to iris color variation. We suggest that genetic variants regulating expression of the OCA2 gene exist in the HERC2 gene or, alternatively, within the 11.7 kb of sequence between OCA2 and HERC2, and that most iris color variation in Europeans is explained by those two genes. Testing markers in the HERC2-OCA2 region may be useful in forensic applications to predict eye color phenotypes of unknown persons of European genetic origin. 相似文献
247.
We have demonstrated that dehydroepiandrosterone (DHEA) acts directly on rat zona fasciculata-reticularis (ZFR) cells to diminish corticosterone secretion by an inhibition of post-cAMP pathway, and decreases functions of steroidogenic enzymes after P450(scc) as well as steroidogenic acute regulatory (StAR) protein expression. However, the mechanisms by which DHEA engages with environmental messenger signals which translate into interfering StAR protein expression are still unclear. This study explored the effects of DHEA on the phosphorylation/activation of extracellular signal-regulated kinases (ERKs). ERK activation resulted in enhancing phosphorylation of steroidogenic factor-1 (SF-1) and increased StAR protein expression. ZFR cells were incubated in the presence or absence of adrenocorticotropin (ACTH), forskolin (FSK), 25-OH-cholesterol, U0126, and H89 at 37 degrees C. The concentration of corticosterone released into the media was measured by radioimmunoassay (RIA). The cells were used to extract protein for Western blot analysis of ERKs or StAR protein expression or immunoprecipitation of SF-1 analysis. The results suggested that (1) ERK pathway of rat ZFR cells might be PKA dependent, (2) ERK activity was required for SF-1 phosphorylation to upregulate steroidogenesis in rat ZFR cells, and (3) DHEA did not affect ERK phosphorylation, however, it attenuated forskolin-stimulated SF-1 phosphorylation to affect StAR protein expression. 相似文献
248.
Harzheim D Pfeiffer KH Fabritz L Kremmer E Buch T Waisman A Kirchhof P Kaupp UB Seifert R 《The EMBO journal》2008,27(4):692-703
Important targets for cAMP signalling in the heart are hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels that underlie the depolarizing 'pacemaker' current, I(f). We studied the role of I(f) in mice, in which binding of cAMP to HCN4 channels was abolished by a single amino-acid exchange (R669Q). Homozygous HCN4(R669Q/R669Q) mice die during embryonic development. Prior to E12, homozygous and heterozygous embryos display reduced heart rates and show no or attenuated responses to catecholaminergic stimulation. Adult heterozygous mice display normal heart rates at rest and during exercise. However, following beta-adrenergic stimulation, hearts exhibit pauses and sino-atrial node block. Our results demonstrate that in the embryo, HCN4 is a true cardiac pacemaker and elevation of HCN4 channel activity by cAMP is essential for viability. In adult mice, an important function of HCN4 channels is to prevent sinus pauses during and after stress while their role as a pacemaker of the murine heart is put into question. Most importantly, our results indicate that HCN4 channels can fulfil their physiological function only when cAMP is bound. 相似文献
249.
250.
Wang SW Hwang GS Chen TJ Wang PS 《American journal of physiology. Endocrinology and metabolism》2008,295(2):E497-E504
Arecoline is one of the major components of betel nuts, which have been consumed as chewing gum in Southeast Asia. In this study, the effects of arecoline on testosterone (T) secretion were explored. Male rats were injected with human chorionic gonadotropin (hCG, 5 IU/kg) or arecoline (1 microg/kg) plus hCG via a jugular catheter. Blood samples were collected at several time intervals subsequent to the challenge. Rat anterior pituitary was treated with gonadotropin-releasing hormone in vitro with or without arecoline, and then the concentrations of luteinizing hormone (LH) in the medium were measured. Rat Leydig cells were purified by Percoll density gradient centrifugation and incubated with arecoline, hCG, forskolin, 8-bromo-cAMP (8-Br-cAMP), nifedipine, nimodipine, or tetrandrine at 34 degrees C for 1 h. A single intravenous injection of arecoline resulted in an increase of the hCG-induced level of plasma T. Administration of arecoline (10(-8) to 10(-6) M) in vitro increased T production in Leydig cells. The stimulatory effect of arecoline on T release in vitro was enhanced by hCG (0.001 IU/ml), forskolin (10(-6) M), or 8-Br-cAMP (10(-5) M). By contrast, nifedipine, nimodipine, or tetrandrine inhibited the increased T concentrations induced by arecoline. Western blot showed that arecoline increases steroidogenic acute regulatory (StAR) protein expression compared with vehicle. These results suggested that arecoline stimulates testosterone production by acting directly on Leydig cells via mechanisms involving an activation of L-type calcium channels, increasing the activity of 17beta-hydroxysteroid dehydrogenase and enhancing the expression of StAR. 相似文献