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21.
Muscarine stimulated a concentration-dependent accumulation of [3H]inositol phosphates in bovine adrenal medullary cells preloaded with [3H]inositol. This muscarinic activation of inositol phospholipid metabolism was fully inhibited by the -ligand 1,3-di-o-tolylguanidine (DTG) with an IC50 of approximately 45 M. Higher concentrations (100 M) of (+) N-allylnormetazocine (SKF-10047) also partially inhibited this response. A concentration of DTG sufficient to fully inhibit the muscarinic response also produced a significant partial inhibition of [3H]inositol phosphate accumulation in response to histamine but not to angiotensin II. These data demonstrate that -compounds inhibit agonist-stimulated inositol phospholipid metabolism in bovine adrenal medullary cells, with a degree of selectivity towards the muscarinic response. 相似文献
22.
Joseph E. Donnelly Dennis J. Jacobsen Janet E. Whatley James O. Hill Larry L. Swift Alan Cherrington Brent Polk Zung V. Tran George Reed 《Obesity (Silver Spring, Md.)》1996,4(3):229-243
Obesity and low levels of physical and metabolic fitness are risk factors for cardiovascular disease and diabetes. The purpose of this investigation was to attenuate obesity and improve physical and metabolic fitness in elementary school children. Schools have the opportunity, mechanisms, and personnel in place to deliver nutrition education, fitness activities, and a school food service that is nutritious and healthy. Cohorts from grades 3 to 5 in two school districts in rural Nebraska (Intervention/Control) participated in a 2-year study of physical activity and modified school lunch program. Data collection for aerobic capacity, body composition, blood chemistry, nutrition knowledge, energy intake, and physical activity was at the beginning and end of each year. Int received enhanced physical activity, grade specific nutrition education, and a lower fat and sodium school lunch program. Con continued with a regular school lunch and team sports activity program. At year 2, Int lunches had significantly less energy (9%), fat (25%), sodium (21%), and more fiber (17%). However, measures of 24-hour energy intake for Int and Con showed significant differences for sodium only. Physical activity in the classroom was 6% greater for Int compared to Con (p < 0.05) but physical activity outside of school was ?16 % less for Int compared to Con (p < 0.05). Body weight and body fat were not different between schools for normal weight or obese children. No differences were found for cholesterol, insulin, and glucose; however, HDL cholesterol was significantly greater and cholesterol/HDL was significantly less for Int compared to Con (p < 0.05). It appears that compensation in both energy intake and physical activity outside of school may be responsible for the lack of differences between Int and Con. 相似文献
23.
The vesicle supply centre (VSC) model (Bartnicki-Garcia et al., 1989) for hyphal tip growth is powerful because it can model
diverse developmental morphologies and predicts cellular organization based in current cell biology. It predicts that tip
growth results from the random distribution of cell surface synthesizing vesicles from a point in the tip, the VSC, which
determines their pattern of impact and fusion at the plasma membrane. We derive equations for tip-high gradients of vesicle
fusions, generated by mechanisms not related to a supply centre, which create typical hyphal morphologies. These equations
direct the conceptual basis for tip growth to vesicle fusion gradients, presumably mediated by a putative membrane skeleton
associated with the plasma membrane. We also show that the organization and behaviour of motile organelles in growing hyphal
tips of the oomycete,Saprolegnia ferax, argue against the presence of an apparatus capable of generating the distribution of vesicles postulated by the VSC model.
We conclude that the VSC model is unlikely to describe the mechanistic basis of tip growth inS. ferax, and therefore, at best, it is not universally applicable. 相似文献
24.
Since their introduction, the interaction trap and other two-hybrid systems have been used to study protein-protein interactions. Despite their general use, little is known about the extent to which the degree of protein interaction determined by two-hybrid approaches parallels the degree of interaction determined by biochemical techniques. In this study, we used a set of lexAop-LEU2 and lexAop-lacZ reporters to calibrate the interaction trap. For the calibration, we used two sets of proteins, the Myc-Max-Mxi1 helix-loop-helix proteins, and wild-type and dimerization-defective versions of the lambda cI repressor. Our results indicate that the strength of interaction as predicted by the two-hybrid approach generally correlates with that determined in vitro, permitting discrimination of high-, intermediate-, and low-affinity interactions, but there was no single reporter for which the amount of gene expression linearly reflected affinity measured in vitro. However, some reporters showed thresholds and only responded to stronger interactions. Finally, some interactions were subject to directionality, and their apparent strength depended on the reporter used. Taken together, our results provide a cautionary framework for interpreting affinities from two-hybrid experiments. 相似文献
25.
Protein Phosphorylation and Calcium Uptake into Rat Forebrain Synaptosomes: Modulation by the σ Ligand, 1,3-Ditolylguanidine 总被引:1,自引:0,他引:1
Paul J. Brent Lynn Herd Heather Saunders Alistair T. R. Sim Peter R. Dunkley 《Journal of neurochemistry》1997,68(5):2201-2211
Abstract: The σ ligand 1,3-di- O -tolylguanidine (DTG) increased basal dynamin and decreased depolarization-stimulated phosphorylation of the synaptosomal protein synapsin Ib without having direct effects on protein kinases or protein phosphatases. DTG dose-dependently decreased the basal cytosolic free Ca2+ concentration ([Ca2+ ]i ) and blocked the depolarization-dependent increases in [Ca2+ ]i . These effects were inhibited by the σ antagonists rimcazole and BMY14802. The nitric oxide donors sodium nitroprusside (SNP) and 8-( p -chlorophenylthio)guanosine-3',5'-cyclic monophosphorothioate decreased basal [Ca2+ ]i and the KCl-evoked rise in [Ca2+ ]i to an extent similar to DTG. SNP, but not DTG, produced a rise in cyclic GMP levels, suggesting that the effect of DTG on [Ca2+ ]i was not mediated via downstream regulation of cyclic GMP levels. DTG increased 45 Ca2+ uptake and efflux under basal conditions and inhibited the 45 Ca2+ uptake induced by depolarization with KCl. The KCl-evoked rise in [Ca2+ ]i was inhibited by ω-conotoxin (ω-CgTx)-GVIA and -MVIIC but not nifedipine and ω-agatoxin-IVA. The effect of DTG on decreasing the KCl-evoked rise in [Ca2+ ]i was additive with ω-CgTx-MVIIC but not with ω-CgTx-GVIA. These data suggest that DTG was producing some of its effects on synapsin I and dynamin phosphorylation and intrasynaptosomal Ca2+ levels via inhibition of N-type Ca2+ channels. 相似文献
26.
Patricia E. Gallagher Thomas P. Brent 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1984,782(4):394-401
Further purification of a human placental 3-methyladenine-DNA glycosylase by phosphocellulose column chromatography yielded a 6000-fold increase in specific activity with greater than 5% recovery. Although 3-methyladenine was the predominant base released from double-stranded methylated DNA by this enzyme, minor releasing activities for 7-methylguanine and 3-methylguanine were also observed. During purification, the three DNA glycosylase activities consistently copurified with constant ratios of specific activity. Moreover, all the activities were heat-inactivated at 50°C at the same rate, required double-stranded methylated DNA as substrate, were inhibited by spermine and spermidine, and were not subject to product inhibition. These data strengthen the likelihood that the three activities are associated with a single DNA glycosylase. 相似文献
27.
Brent R. Larson 《Life sciences》1982,30(12):1003-1012
Presented is a pilot project describing a new strategy for mass spectrometric peptide sequencing. Using orthophthalaldehyde (OPA), two peptides were derivatized and their fluorescent adducts isolated using reversed phase high performance liquid chromatography. The OPA-peptides were permethylated and the derivatized molecules subjected to direct probe mass spectral analysis. The spectra obtained from the OPA-peptides was analogous to those observed for standard -acyl permethyl derivatives enabling the complete sequence of the peptides to be determined. 相似文献
28.
Shoot tip, bud, leaf, stem and root explants from bearing trees, offshoots, seedlings, and asexual plantlets ofPhoenix dactylifera L. were cultured on modified Murashige and Skoog nutrient media containing 3 g/l activated charcoal, 100 mg/l 2,4-dichlorophenoxyacetic acid, 3 mg/l
N
6-(Δ2-isopentyl)adenine to obtain callus. Differential morphogenetic responses were obtained from calli dependent on the explant
type and parent source. Subcultured shoot tips and leafy lateral buds callus on nutrient media devoid of charcoal and supplemented
with 0.1 mg/l α-naphthaleneacetic acid (NAA) produced adventitious plantlets. Subcultured leaf calli produced roots only. Root callus failed
to exhibit any morphogenetic response upon subculturing. Undifferentiated non-leafy buds and stem tissues did not give rise
to callus, regardless of the parent source. Generally, the best callus and embryogenetic responses from explants were obtained
from seedling and plantlet parent sources. Similarly, organogenetic responses such as root formation and shoot development
from shoot tips cultured on media containing 10 mg/l NAA were also related to the parent explant source.
Mention of a trademark or proprietary product in the paper does not constitute a guarantee or warranty of the product by the
U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be available. 相似文献
29.
F. Brent Johnson 《Chemico-biological interactions》1982,40(1):97-112
Quantitative assays for the morphological transformation of 3T3 Swiss mouse cells by herpes simplex type 2 virus (HSV-2) were employed to examine the effect on cell transformation of chemical carcinogens and suspected carcinogens. Exposure of the cells to the chemical compound, followed by virus infection, resulted in enhancement of transformation when compared to that observed with chemical or virus alone. Enhancement occurred in tests utilizing either UV light-inactivated HSV-2 (strain 333) or a temperature-sensitive (ts) mutant of HSV-2 [A8(293)]. A series of seven ts-mutants were tested and exhibited varying degrees of transformation. Enhancement of transformation occurred in cells treated with hydrazine (HZ) and 1,2-dimethylhydrazine (SDMH). No enhancement occurred when cells were treated with monomethylhydrazine, 1,1-dimethylhydrazine and the jet fuels JP-5, JP-10, RJ-4 and RJ-5. A strong time dependence after treatment was demonstrated with some enhancement seen at 6 h after chemical treatment but the greatest enhancement appeared when virus infection began after 24 h of chemical exposure. 相似文献
30.
G R Williams J W Harney B M Forman H H Samuels G A Brent 《The Journal of biological chemistry》1991,266(29):19636-19644