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31.
Salinity tolerance of Saprolegnia parasitica coker 总被引:1,自引:0,他引:1
Experiments on two strains ofS. parasitica have shown that this species together with other species ofSaprolegnia have a high tolerance to salinity when vegetative growth alone is considered. The effect of temperature and salinity on asexual sporulation shows that at temperatures of up to 20°C good sporulation occurs in salinities of 3.5%.. At temperatures above this, sporulation is repressed and gammae tend to be formed. Temperature appears to have a marked effect on the initial germination of zoospores, but after 12 hours this effect is minimized.
Zusammenfassung Untersuchungen an zwei Stämmen vonS. parasitica haben gezeigt, daß diese Art, zusammen mit anderen Arten vonSaprolegnia, eine hohe Toleranz gegen Salinität hat, wenn das vegetative Wachstum allein in Betracht gezogen wird. Die Wirkung von Temperatur und Salinität an asexuellen Sporulation zeigt, daß bei Temperaturen bis zu 20°C eine gute Sporulation in einer Salinität von 3.5%. vorherrscht. Bei höheren Temperaturen wird Sporulation unterdrückt und bilden sich Gammae. Temperatur scheint eine bedeutende Wirkung an der initialen Germination von Zoosporen zu haben, jedoch ist diese Wirkung nach 12 Stunden minimal.相似文献
32.
Pamela D. Martin Gareth R. Dutton Phillip J. Brantley 《Obesity (Silver Spring, Md.)》2004,12(4):646-651
Objective: Although self‐efficacy has received increasing attention for its role in weight loss, there is less research examining this relationship in minority samples. The purpose of this study was to determine whether self‐efficacy for weight loss was predictive of weight change in a sample of African‐American women. Research Methods and Procedures: Subjects were 106 overweight or obese, low‐income African‐American women participating in a weight management intervention that involved either personalized monthly sessions with their primary care physician or standard care. Weight and self‐efficacy for weight loss were assessed at baseline and at the end of the 6‐month treatment. Results: For subjects in the personalized intervention, baseline self‐efficacy was predictive of subsequent weight change, such that higher levels of self‐efficacy before treatment were associated with less weight loss. In contrast, improvements in self‐efficacy during treatment were associated with greater weight loss for the personalized intervention group. Discussion: Results suggest high self‐efficacy for weight loss before treatment may be detrimental to success, whereas treatments that improve participants’ self‐efficacy may result in greater weight loss. High pretreatment self‐efficacy may be indicative of overconfidence or lack of experience with the difficulties associated with weight loss efforts. Whereas replication is needed, our results suggest that self‐efficacy is an important variable to consider when implementing weight loss interventions. 相似文献
33.
Magnocellular neurons of the supraoptic nucleus (SON) secrete oxytocin and vasopressin from axon terminals in the neurohypophysis, but they also release large amounts of peptide from their somata and dendrites, and this can be regulated both by activity-dependent Ca(2+) influx and by mobilization of intracellular Ca(2+). This somato-dendritic release can also be primed by agents that mobilise intracellular Ca(2+), meaning that the extent to which it is activity-dependent, is physiologically labile. We investigated the role of different Ca(2+) channels in somato-dendritic release; blocking N-type channels reduced depolarisation-induced oxytocin release from SONs in vitro from adult and post-natal day 8 (PND-8) rats, blocking L-type only had effect in PND-8 rats, while blocking other channel types had no significant effect. When oxytocin release was primed by prior exposure to thapsigargin, both N- and L-type channel blockers reduced release, while P/Q and R-type blockers were ineffective. Using confocal microscopy, we found immunoreactivity for Ca(v)1.2 and 1.3 channel subunits (which both form L-type channels), 2.1 (P/Q type), 2.2 (N-type) and 2.3 (R-type) in the somata and dendrites of both oxytocin and vasopressin neurons, and the intensity of the immunofluorescence signal for different subunits differed between PND-8, adult and lactating rats. Using patch-clamp electrophysiology, the N-type Ca(2+) current density increased after thapsigargin treatment, but did not alter the voltage sensitivity of the channel. These results suggest that the expression, location or availability of N-type Ca(2+) channels is altered when required for high rates of somato-dendritic peptide release. 相似文献
34.
Marcelo R. de Carvalho Flávio A. Bockmann Dalton S. Amorim Carlos Roberto F. Brandão Mário de Vivo José L. de Figueiredo Heraldo A. Britski Mário C. C. de Pinna Naércio A. Menezes Fernando P. L. Marques Nelson Papavero Eliana M. Cancello Jorge V. Crisci John D. McEachran Robert C. Schelly John G. Lundberg Anthony C. Gill Ralf Britz Quentin D. Wheeler Melanie L. J. Stiassny Lynne R. Parenti Larry M. Page Ward C. Wheeler Julián Faivovich Richard P. Vari Lance Grande Chris J. Humphries Rob DeSalle Malte C. Ebach Gareth J. Nelson 《Evolutionary biology》2007,34(3-4):140-143
35.
Prater CA Redmond CT Barney W Bonning BC Potter DA 《Journal of economic entomology》2006,99(4):1129-1137
Agrotis ipsilon multiple nucleopolyhedrovirus (family Baculoviridae, genus Nucleopolyhedrovirus, AgipMNPV), a naturally occurring baculovirus, was found infecting black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), on central Kentucky golf courses. Laboratory, greenhouse, and field studies investigated the potential of AgipMNPV for managing black cutworms in turfgrass. The virus was highly active against first instars (LC50 = 73 occlusion bodies [OBs] per microl with 2-microl dose; 95% confidence intervals, 55-98). First instars that ingested a high lethal dose stopped feeding and died in 3-6 d as early second instars, whereas lethally infected fourth instars continued to feed and grow for 4-9 d until death. Sublethal doses consumed by third or fifth instars had little or no effect on subsequent developmental rate or pupal weight. Horizontal transmission of AgipMNPV in turfgrass plots was shown. Sprayed suspensions of AgipMNPV (5 x 10(8) - 6 x 10(9) OBs/m2) resulted in 75 to > 93% lethal infection of third or fourth instars in field plots of fairway-height creeping bentgrass, Agrostis stolonifera (Huds.), and on a golf course putting green collar. Virus spray residues (7 x 10(9) OBs/m2) allowed to weather on mowed and irrigated creeping bentgrass field plots significantly increased lethal infection of implanted larvae for at least 4 wk. This study, the first to evaluate a virus against a pest in turfgrass, suggests that AgipMNPV has potential as a preventive bioinsecticide targeting early instar black cutworms. Establishing a virus reservoir in the thatch and soil could suppress successive generations of that key pest on golf courses and sport fields. 相似文献
36.
The amitochondriate eukaryote Trichomonas vaginalis contains a divergent thioredoxin-linked peroxiredoxin antioxidant system 总被引:2,自引:0,他引:2
Coombs GH Westrop GD Suchan P Puzova G Hirt RP Embley TM Mottram JC Müller S 《The Journal of biological chemistry》2004,279(7):5249-5256
Trichomonas is an amitochondriate parasitic protozoon specialized for an anaerobic lifestyle. Nevertheless, it is exposed to oxygen and is able to cope with the resultant oxidative stress. In the absence of glutathione, cysteine has been thought to be the major antioxidant. We now report that the parasite contains thioredoxin reductase, which functions together with thioredoxin and thioredoxin peroxidase to detoxify potentially damaging oxidants. Thioredoxin reductase and thioredoxin also reduce cystine and so may play a role in maintaining the cellular cysteine levels. The importance of the thioredoxin system as one of the major antioxidant defense mechanisms in Trichomonas was confirmed by showing that the parasite responds to environmental changes resulting in increased oxidative stress by up-regulating thioredoxin and thioredoxin peroxidases levels. Sequence data indicate that the thioredoxin reductase of Trichomonas differs fundamentally in structure from that of its human host and thus may represent a useful drug target. The protein is generally similar to thioredoxin reductases present in other lower eukaryotes, all of which probably originated through horizontal gene transfer from a prokaryote. The phylogenetic signal in thioredoxin peroxidase is weak, but evidence from trees suggests that this gene has been subject to repeated horizontal gene transfers from different prokaryotes to different eukaryotes. The data are thus consistent with the complexity hypothesis that predicts that the evolution of simple pathways such as the thioredoxin cascade are likely to be affected by horizontal gene transfer between species. 相似文献
37.
The acoustic structure of echolocation pulses emitted by Japanese pipistrellePipistrellus abramus (Temminck, 1840) bats during different phases of aerial hawking is described here for the first time. Behavioural observations
of the foraging flight in conjunction with acoustical analysis of echolocation pulses indicated a flight path consisting of
four distinct phases following the reconnaissance or search phase. Short (∼4.68 ms) and relatively broadband frequencymodulated
(FM) pulses (∼23.55 kHz bandwidth) were emitted at a repetition rate of 15 Hz during presumed target approach. Presumed insect
capture consisted of an early and a late buzz phase. Both buzz types were emitted at high repetition rates (111 Hz in early
to 222 Hz in late) and consisted of very short, broadband FM pulses (1.26 ms in early to 0.3 ms in late). There was also a
characteristically sharp drop in both the peak and terminal frequencies of each echolocation pulse during the transition from
early to late buzz. No pulses were recorded during the final phase of foraging referred to as a “post-buzz pause”. Thus the
foraging behaviour of this species consisted of five sequential phases involving four broad types of echolocation pulses. 相似文献
38.
39.
Matthews GD Guzadhur L Grace A Huang CL 《Journal of applied physiology (Bethesda, Md. : 1985)》2012,112(11):1847-1863
Electrocardiographic QT- and T-wave alternans, presaging ventricular arrhythmia, reflects compromised adaptation of action potential (AP) duration (APD) to altered heart rate, classically attributed to incomplete Na(v)1.5 channel recovery prior to subsequent stimulation. The restitution hypothesis suggests a function whose slope directly relates to APD alternans magnitude, predicting a critical instability condition, potentially generating arrhythmia. The present experiments directly test for such correlations among arrhythmia, APD alternans and restitution. Mice haploinsufficient in the Scn5a, cardiac Na(+) channel gene (Scn5a(+/-)), previously used to replicate Brugada syndrome, were used, owing to their established arrhythmic properties increased by flecainide and decreased by quinidine, particularly in right ventricular (RV) epicardium. Monophasic APs, obtained during pacing with progressively decrementing cycle lengths, were systematically compared at RV and left ventricular epicardial and endocardial recording sites in Langendorff-perfused Scn5a(+/-) and wild-type hearts before and following flecainide (10 μM) or quinidine (5 μM) application. The extent of alternans was assessed using a novel algorithm. Scn5a(+/-) hearts showed greater frequencies of arrhythmic endpoints with increased incidences of ventricular tachycardia, diminished by quinidine, and earlier onsets of ventricular fibrillation, particularly following flecainide challenge. These features correlated directly with increased refractory periods, specifically in the RV, and abnormal restitution and alternans properties in the RV epicardium. The latter variables were related by a unique, continuous higher-order function, rather than a linear relationship with an unstable threshold. These findings demonstrate a specific relationship between alternans and restitution, as well as confirming their capacity to predict arrhythmia, but implicate mechanisms additional to the voltage feedback suggested in the restitution hypothesis. 相似文献
40.
Michael J. Bayly Gareth D. Holmes Paul I. Forster David J. Cantrill Pauline Y. Ladiges 《PloS one》2013,8(8)