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51.
52.
Hong Z Olschewski A Reeve HL Nelson DP Hong F Weir EK 《American journal of physiology. Lung cellular and molecular physiology》2004,286(3):L531-L538
The anorectic agent dexfenfluramine (dex) causes the development of primary pulmonary hypertension in susceptible patients by an unknown mechanism. We compared the effects of dex with those of its major metabolite, nordexfenfluamine (nordex), in the isolated perfused rat lung and in isolated rings of resistance pulmonary arteries. Nordex caused a dose-dependent and more intense vasoconstriction, which can be inhibited by the nonspecific 5-hydroxytryptamine type 2 (5-HT(2)) blocker ketanserin. Similarly a rise in cytosolic calcium concentration ([Ca(2+)](i)) in dispersed pulmonary artery smooth muscle cells (PASMCs) induced by nordex could be prevented by ketanserin. Unlike prior observations with dex, nordex did not inhibit K(+) current or cause depolarization in PASMCs. Removal of Ca(2+) from the tissue bath or addition of nifedipine (1 microM) reduced ring contraction to nordex by 60 +/- 9 and 63 +/- 4%, respectively. The addition of 2-aminoethoxydiphenyl borate (2-APB), a blocker of store-operated channels and the inositol 1,4,5-trisphosphate receptor, caused a dose-dependent decrease in the ring contraction elicited by nordex. The combination of 2-APB (10 microM) and nifedipine (1 microM) completely ablated the nordex contraction. Likewise the release of Ca(2+) from the sarcoplasmic reticulum by cyclopiazonic acid markedly reduced the nordex contraction while leaving the KCl contraction unchanged. We conclude that nordex may be responsible for much of the vasoconstriction stimulated by dex, through the activation of 5-HT(2) receptors and that the [Ca(2+)](i) increase in rat PASMCs caused by dex/nordex is due to both influx of extracellular Ca(2+) and release of Ca(2+) from the sarcoplasmic reticulum. 相似文献
53.
We develop an evolutionary model that predicts that characters selected to signal individual identity will have properties differing from those expected for indicator signals of quality. Traits signaling identity should be highly variable, often display polymodal distributions, not be condition dependent (i.e., be cheap to produce and/or maintain), not be associated with fitness differences, exhibit independent assortment of component characters, and often occur as fixed phenotypes with a high degree of genetic determination. We illustrate the existence of traits with precisely these attributes in the ornamental, conspicuously variable, and sexually dimorphic breeding plumages of ruff sandpipers Philomachus pugnax and red-billed queleas Quelea quelea. Although ruffs lek and queleas are monogamous, both species breed in high-density aggregations with high rates of social interactions (e.g., aggression and territory defense). Under these socioecological conditions, individual recognition based on visual cues may be unusually important. In contrast to these species, we also review plumage characteristics in house finches Carpodacus mexicanus, a nonterritorial, dispersed-breeding species in which plumage ornamentation is thought to signal quality. In keeping with expectations for quality signals, house finch plumage is relatively less variable, unimodally distributed, condition dependent, correlated with fitness measures, has positively correlated component characters, and is a plastic, environmentally determined trait. We briefly discuss signals of identity in other animals. 相似文献
54.
Reeve JR Liddle RA McVey DC Vigna SR Solomon TE Keire DA Rosenquist G Shively JE Lee TD Chew P Green GM Coskun T 《American journal of physiology. Gastrointestinal and liver physiology》2004,287(2):G326-G333
Nonsulfated CCK(58) [CCK(58)(ns)] has not been considered to be of biological importance because CCK(58)(ns) binds poorly to the CCK(A) receptor and has only been identified once in intestinal extracts. In this work, a radioimmunoassay specific for the COOH-terminal region of gastrin and CCK (antibody 5135) was used to monitor the purification of CCK molecular forms from canine intestinal extracts. A minor immunoreactive peak was associated with a major absorbance peak during an ion-exchange, HPLC step. Characterization of this minor immunoreactive peak demonstrated that it was CCK(58)(ns). CCK(58)(ns) is 14% as immunoreactive as sulfated CCK(8) [CCK(8)(s)]. Amino acid analysis demonstrated that CCK(58)(ns) was present at 50% the amount of CCK(58)(s). In addition, we found that CCK(58)(ns) does not potently displace an (125)I-labeled CCK(10) analog from the CCK(A) receptor in mouse pancreatic membranes and does not stimulate amylase release from isolated pancreatic acini, or stimulate pancreatic secretion in an anesthetized rat model. By contrast, CCK(58)(ns) does bind to CCK(B) receptors and stimulates gastric acid secretion via this receptor. The presence of CCK(58)(ns) and its ability to selectively stimulate the CCK(B) receptor without stimulation of the CCK(A) receptor suggest that CCK(58)(ns) may have unique physiological properties, especially tissues where the nonsulfated peptide can act as a paracrine or neurocrine agent. 相似文献
55.
Kovatchev B Cox D Hill R Reeve R Robeva R Loboschefski T 《Applied psychophysiology and biofeedback》2001,26(2):127-140
This study continues our research to further validate the idea that ADHD (Attention Deficit/Hyperactivity Disorder) interferes with transition from one task to another and this interference can be quantified by a Consistency Index (CI) derived from a specific mathematical representation of EEG data. We reanalyze 32 previously reported data sets present new data for 35 boys and girls, ages 7-12, ADHD or control. Each data set contains EEG, recorded and digitized while participants perform consecutive 10-min tasks: video, reading, and math. For boys, the CI in ADHD was four times lower than in controls, p < .005, for girls this difference was two times, p < .05. ADHD/control classification based on the CI coincided with the DSM-IV criteria for 88% of the boys and for 67% of the girls. Post hoc analysis indicated that the classification utility of the CI diminished with age. A CI below 40% could be a discriminating, reliable, and reproducible marker of ADHD in young boys. 相似文献
56.
DNA binding and the topology of DNA have been determined in complexes formed by >20 archaeal histone variants and archaeal histone dimer fusions with residue replacements at sites responsible for histone fold dimer:dimer interactions. Almost all of these variants have decreased affinity for DNA. They have also lost the flexibility of the wild type archaeal histones to wrap DNA into a negative or positive supercoil depending on the salt environment; they wrap DNA into positive supercoils under all salt conditions. The histone folds of the archaeal histones, HMfA and HMfB, from Methanothermus fervidus are almost identical, but (HMfA)(2) and (HMfB)(2) homodimers assemble into tetramers with sequence-dependent differences in DNA affinity. By construction and mutagenesis of HMfA+HMfB and HMfB+HMfA histone dimer fusions, the structure formed at the histone dimer:dimer interface within an archaeal histone tetramer has been shown to determine this difference in DNA affinity. Therefore, by regulating the assembly of different archaeal histone dimers into tetramers that have different sequence affinities, the assembly of archaeal histone-DNA complexes could be localized and used to regulate gene expression. 相似文献
57.
Reeve JR Green GM Chew P Eysselein VE Keire DA 《American journal of physiology. Gastrointestinal and liver physiology》2003,285(2):G255-G265
CCK-58 differs from CCK-8 in patterns of expression of pancreatic secretion of fluid and amylase and gallbladder contraction. These differences have physiological relevance only if CCK-58 release is stimulated by nutrients entering the intestine and if CCK-58 circulates in sizeable amounts. In this study, we report that when radiolabeled CCK-58 is added to rat blood and plasma is formed, there is extensive loss and degradation of the radioactive peptide. Therefore, a new method was developed to minimize loss and degradation of this label. This method recovered >85% of the label with no detectable degradation. Furthermore, the optimized method recovered all unlabeled exogenous cholecystokinin molecular forms in >80% yields. Blood from fasted rats and rats in which cholecystokinin release was stimulated by the trypsin inhibitor camostat contained only CCK-58 (3.5 +/- 0.5 and 17 +/- 1.5 fmol/ml, respectively). Because CCK-58 predominates in the blood, this molecular form should be used in studies on the physiology and pathophysiology of cholecystokinin. 相似文献
58.
Mutational analysis of differences in thermostability between histones from mesophilic and hyperthermophilic archaea 下载免费PDF全文
Amino acid residues responsible for the large difference in thermostability between HMfB and HFoB, archaeal histones from the hyperthermophile Methanothermus fervidus and the mesophile Methanobacterium formicicum, respectively, have been identified by site-specific mutagenesis. The thermal denaturation of approximately 70 archaeal histone variants has been monitored by circular dichroism, and the data generated were fit to a two-state unfolding model (dimer-->two random coil monomers) to obtain a standard-state (1M) melting temperature for each variant dimer. The results of single-, double-, and triple-residue substitutions reveal that the much higher stability of rHMfB dimers, relative to rHFoB dimers, is conferred predominantly by improved intermolecular hydrophobic interactions near the center of the histone dimer core and by additional favorable ion pairs on the dimer surface. 相似文献
59.
Merkel RL Cox DJ Kovatchev B Morris J Seward R Hill R Reeve R 《Applied psychophysiology and biofeedback》2000,25(3):133-142
The primary diagnostic procedure for Attention-Deficit/Hyperactivity Disorder (ADHD) is the clinical interview, because psychological, neuropsychological, and neurological tests to date have not had sufficient specificity. Currently, there is no objective means to measure severity of ADHD, or the extent to which it is benefited by various dosages of medication. We recently reported that a certain EEG profile, the Consistency Index, occurring during the transition between two easy cognitive tasks clearly differentiated ADHD from non-ADHD boys between the ages of 8 and 12. The current study replicated this with older males (19–25) using different tasks, and a double blind, placebo versus Ritalin® controlled crossover design. Seven ADHD subjects were found to have a significantly lower Consistency Index than 6 non-ADHD males while transitioning from 2 Simple tasks during placebo condition, while only the ADHD subjects demonstrated a significant improvement in their Consistency Index while on Ritalin®. Similar but nonsignificant trends were observed while transitioning across Hard tasks. 相似文献
60.
Porter VA Reeve HL Cornfield DN 《American journal of physiology. Lung cellular and molecular physiology》2000,279(4):L751-L757
To study developmental changes in intracellular calcium handling in pulmonary artery smooth muscle cells (PASMCs), cells were isolated from distal and proximal pulmonary arteries from rabbits at different developmental stages: juvenile (4-6 wk old), newborn (<48 h), and full-term fetal. Isolated PASMCs were studied using the calcium-sensitive dye fura 2. Cells from each age group responded to caffeine with an increase in calcium; however, ryanodine (50 microM) only increased calcium in fetal distal PASMCs. The ryanodine-induced increase was due to influx of extracellular calcium because it was blocked by removal of extracellular calcium or by diltiazem. The calcium-sensitive potassium (K(Ca)) channel blocker iberiotoxin produced a transient increase in calcium in the fetal distal PASMCs, which could be inhibited by prior application of ryanodine. Conversely, the ryanodine response was inhibited if iberiotoxin was given first. With the use of electrophysiology and confocal microscopy, fetal PASMCs were shown to exhibit spontaneous transient outward currents and calcium sparks, respectively. These observations suggest that ryanodine-sensitive release of calcium from the sarcoplasmic reticulum and K(Ca) channels act together to control intracellular calcium only in fetal distal PASMCs. 相似文献