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31.
Inhibition by Cyclic AMP of Phorbol Ester-Potentiated Norepinephrine Release from Guinea Pig Brain Cortical Synaptosomes 总被引:8,自引:4,他引:4
Hisato Shuntoh Kohtaro Taniyama Hisashi Fukuzaki Chikako Tanaka 《Journal of neurochemistry》1988,51(5):1565-1572
The involvement of Ca2+/phospholipid-dependent protein kinase (protein kinase C, PKC) and cyclic AMP-dependent protein kinase in the K+-evoked release of norepinephrine (NE) was studied using guinea pig brain cortical synaptosomes preloaded with [3H]NE. 12-O-Tetradecanoylphorbol-13-acetate (TPA), a potent activator of PKC, enhanced the K+-evoked release of [3H]NE, in a concentration-dependent manner, but with no effect on the spontaneous outflow and uptake of [3H]NE in the synaptosomes. The apparent affinity of the evoked release for added calcium but not the maximally evoked release was increased by TPA (10(-7) M). Inhibitors of PKC, polymyxin B, and a more potent inhibitor, staurosporine, counteracted the TPA-induced potentiation of the evoked release. Both forskolin and dibutyryl cyclic AMP (DBcAMP) enhanced the evoked release, but reduced the TPA-potentiated NE release. A novel inhibitor of cyclic AMP-dependent protein kinase, KT5720, blocked both the forskolin-induced increase in the evoked release and its inhibition of TPA-induced potentiation in the evoked release, thereby suggesting that forskolin or DBcAMP counteracts the Ca2+-dependent release of NE by activating cyclic AMP-dependent protein kinase. These results suggest that the activation of PKC potentiates the evoked release of NE and that the activation of cyclic AMP-dependent protein kinase acts negatively on the PKC-activated exocytotic neurotransmitter release process in brain synaptosomes of the guinea pig. 相似文献
32.
Water culture, growth chamber, greenhouse and field experiments were conducted to compare the effect of NH4−N and NO3−N on yield and N uptake of rapeseed (Brassica campestris L.). In water culture, the yields of 28-day old rapeseed plants grown at 14 μg N ml−1 were double with NO3 compared to NH4, but N uptake was little affected. There was no such effect when concentration was reduced to 3.5 or 7 μg N ml−1. The yield and N uptake of 26-day old rapeseed grown on six soils (pH 4.6 to 6.5) in pots in a growth chamber were much greater
with NO3 than with NH4, although N concentration was more in the NH4- than the NO3-grown plants. In a greenhouse experiment with rapeseed grown on 12 potted soils, the N uptake of applied N was greater with
NO3 than with NH4 on all soils. Averages were 63% with NH4 and 78% with NO3. However, NH4-fixation capacities of the soils were only weakly correlated with yield from the two sources of N (r=0.48) and the relation
was similar with N uptake. In contrast to the behavior of water culture, growth chamber and greenhouse experiments, the 33
field experiments did not show consistent difference in seed yield with NH4 and NO3 applied at time of seeding. In nine field experiments where band application was used for Ca(NO3)2, (NH4)2 SO4, NH4 NO3, yield tended to be greatest for (NH4)2SO4. However, in 19 experiments on acid soils with and without lime, yields in most cases were similar with (NH4)2SO4 and NH4 NO3. Nitrification inhibitors were added to spring banded NH4-based fertilizers in five experiments, but the yields were not influenced.
Scientific Paper No. 558, Lacombe Research Station, Agriculture Canada. 相似文献
33.
Laboratory incubation and field experiments were conducted to evaluate thiourea, ATC (4-amino-1, 2, 4 triazole hydrochloride)
and N-Serve 24 E (2-chloro-6-trichloromethyl-pyridine) as inhibitors of nitrification of fertilizer N. In the incubation experiment,
most of the added aqueous NH3 or urea was nitrified at 14 days on both soils, but addition of the inhibitors to fertilizer N decreased the conversion of
NH4−N to NO3−N markedly. There was less nitrification for ATC and thiourea but not for N-Serve 24 E when the fertilizers and the inhibitors
were placed at a point as opposed to when mixed into soil. After 28 days, ATC and N-Serve 24 E were more effective in inhibiting
nitrification than thiourea. ATC and N-Serve 24 E also inhibited release of mineral N (NH4−N+NO3−N) from native soil N. In the uncropped field experiment, which received N fertilizers in the fall, nitrification of fall-applied
N placed in the 15-cm bands was almost complete by early May in the Malmo soil, but not in the Breton soil. When ATC or thiourea
had been applied with urea, nitrification of fall-applied N was depressed by May and the recovery of applied N as NH4−N was greater with increasing band spacing to 60 cm or placing N fertilizer in nests (a method of application where urea
prills were placed at a point in the soil in the center of 60×60 cm area). In late June, the percentage recovery of fall-applied
N in soil as NH4−N or mineral N increased with wide band spacing, or nest placement, or by adding ATC to fertilizer N on both soils. These
results indicate that placing ammonium-based N fertilizers in widely-spaced bands or in nests with low rates of inhibitors
slows nitrification enough to prevent much of the losses from fall-applied N.
Scientific Paper No. 552, Lacombe Research Station, Research Branch, Agric, Can. 相似文献
34.
The juice of unripe fruit from a wild species of tomato, Lycopersicon peruvianum (L.) Mill., LA 107, contains over 50% of its soluble proteins as the sum of two proteinase inhibitors. These are the highest levels of proteinase inhibitors and highest percentage of soluble proteins as proteinase inhibitors of any plant or animal tissue found to date. Fruit of the modern tomato, L. esculentum Mill., contains only negligible quantities of the two inhibitors. The two proteinase inhibitors in the fruit of L. peruvianum are members of the Inhibitor I and II families previously found in potato tubers and in leaves of wounded potato and tomato plants. The levels of the two inhibitors in the unripe fruit decrease significantly during ripening. Unripe fruit from other wild Lycopersicon species such as L. parviflorum Rick, Kesicki, Fobes et Holle, L. hirsutum Humb. et Bonpe., L. pimpinellifolium Mill., and other lines of L. peruvianum contain moderate levels of the inhibitors that also decrease during ripening. Another wild tomato species, L. pennellii Corr., is similar to L. esculentum in not containing the two proteinase inhibitors in either unripe or ripe fruit. The transient levels of the inhibitors in fruit of wild species indicate that they are present in unripe fruit as defensive chemicals against insects, birds or small mammals and their disappearance during ripening may render them edible to facilitate seed dispersal. High levels of mRNAs coding for Inhibitors I and II in unripe fruit of L. peruvianum, LA 107, indicate that strong promoters may regulate the developmentally expressed proteinase-inhibitor genes in tomato fruit that may have a substantial potential for use in genetic-engineering experiments to enhance the production of large quantities of proteinase inhibitors or other proteins in field tomatoes.Abbreviations poly(A)+ mRNA
polyadenylated mRNA
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide electrophoresis
Project 1791, College of Agriculture and Home Economics Research Center, Washington, State University 相似文献
35.
Agnes Janoshazi David M. Ojcius Bruce Kone Julian L. Seifter A. K. Solomon 《The Journal of membrane biology》1988,103(2):181-189
Summary A membrane protein that is immunochemically similar to the red cell anion exchange protein, band 3, has been identified on the basolateral face of the outer medullary collecting duct (MCD) cells in rabbit kidney. In freshly prepared separated rabbit MCD cells, M.L. Zeidel, P. Silva and J.L. Seifter (J. Clin. Invest.
77:1682–1688, 1986) found that Cl–/HCO
3
-
exchange was inhibited by the stilbene anion exchange inhibitor, DIDS (4,4-diisothiocyano-2,2-disulfonic stilbene), with aK
1 similar to that for the red cell. We have measured the binding affinities of a fluorescent stilbene inhibitor, DBDS (4,4-dibenzamido-2,2-disulfonic stilbene), to MCD cells in 28.5 mM citrate and have characterized both a high-affinity site (K
1
s
=93±24 mM) and a lower affinity site (K
2
s
=430±260 nM), which are closely similar to values for the red cell of 110±51 nM for the high-affinity site and 980±200 nM for the lower affinity site (A.S. Verkman, J.A. Dix & A.K. Solomon,J. Gen. Physiol.
81:421–449, 1983). When Cl– replaces citrate in the buffer, the two sites collapse into a single one withK
1
s
=1500±400 nM, similar to the singleK
1
s
=1200±200 nM in the red cell (J.A. Dix, A.S. Verkman & A.K. Solomon,J. Membrane Biol.
89:211–223, 1986). The kinetics of DBDS binding to MCD cells at 0.25 M–1 are characterized by a fast process, =0.14±0.03 sec, similar to =0.12±0.03 sec in the red cell. These similarities show that the physical chemical characteristics of stilbene inhibitor binding to MCD cell band 3 closely resemble those for red cell band 3, which suggests that the molecular structure is highly conserved. 相似文献
36.
Proteinase K, the extracellular serine endopeptidase (E.C. 3.4.21.14) from the fungus Tritirachium album limber, is homologous to the bacterial subtilisin proteases. The binding geometry of the synthetic inhibitor carbobenzoxy-Ala-Phechloromethyl Ketone to the active site of proteinase K was the first determined from a Fourier synthesis based on synchrotron X-ray diffraction data between 1.8 Å and 5.0 Å resolution. The protein inhibitor complexes was refined by restrained least-squares minimization with the data between 10.0 and 1.8 Å. The final R factor was 19.1% and the model contained 2,018 protein atoms, 28 inhibitors atoms, 125 water molecules, and two Ca2+ ions. The peptides portion of the inhibitor is bound to the active center of proteinase K by means of a three-stranded antiparallel pleated sheet, with the side chain of the phenylalanine located in the P1 site. Model building studies, with lysine replacing phenylalanine in the inhibitor, explain the relatively unspecific catalytic activity of the enzyme. 相似文献
37.
Thiobacillus tepidarius (type strain) was grown in microaerophilic conditions, on tetrathionate, thiosulfate or crystalline So. The rates of tetrathionate, thiosulfate, elemental sulfur (So) and sulfite oxidation of the different cultures were measured respirometrically, using exponentially growing cells, with an oxygen electrode. Cells growing on the three different sulfur compounds retain thiosulfate-, tetrathionate, and So-oxidizing activities (SOA), but lack respiratory sulfite-oxidizing activity. The SOA for all the cultures was almost totally inhibited by 50 M myxothiazol, an inhibitor of the quinone-cytochrome b region, and by 10 M of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). Tetrathionate- and thiosulfate-oxidizing activities were moderately and weakly inhibited by 50 M totally inhibited (>95%) all respiratory activities. This study suggests that electrons released by So oxidation enter the respiratory chain in the quinone-cytochrome b region.Abbreviation SOA
sulfur-oxidizing activity 相似文献
38.
The effect of eight different acetylcholinesterase inhibitors (AChEIs) on the activity of acetylcholinesterase (AChE) molecular forms was investigated. Aqueous-soluble and detergent-soluble AChE molecular forms were separated from rat brain homogenate by sucrose density sedimentation. The bulk of soluble AChE corresponds to globular tetrameric (G4), and monomeric (G1) forms. Heptylphysostigmine (HEP) and diisopropylfluorophosphate were more selective for the G1 than for the G4 form in aqueous-soluble extract. Neostigmine showed slightly more selectivity for the G1 form both in aqueous- and detergent-soluble extracts. Other drugs such as physostigmine, echothiophate, BW284C51, tetrahydroaminoacridine, and metrifonate inhibited both aqueous- and detergent-soluble AChE molecular forms with similar potency. Inhibition of aqueous-soluble AChE by HEP was highly competitive with Triton X-100 in a gradient, indicating that HEP may bind to a detergent-sensitive non-catalytic site of AChE. These results suggest a differential sensitivity among AChE molecular forms to inhibition by drugs through an allosteric mechanism. The application of these properties in developing AChEIs for treatment of Alzheimer disease is considered.Special issue dedicated to Dr. Morris H. Aprison. 相似文献
39.
Taina Tiainen 《Plant cell reports》1992,10(12):604-607
Summary The role of ethylene in embryogenesis of cultured potato anthers was studied indirectly by testing various substances known to affect ethylene formation. The reducing agents ascorbic acid and L-cysteine prevented browning of anther cultures and significantly stimulated embryogenesis. Embryogenesis was also promoted by the use of the ethylene inhibitors AgNO3 and n-propyl-gallate and by the polyamines spermidine and putrescine. The use of the ethylene releasing compound ethrel significantly inhibited embryogenesis.Abbreviations MS
Murashige & Skoog
- PVP
polyvinylpyrrolidone
- MW
molecular weight
- ACC
1-aminocyclopropane-1-carboxylic acid
- ethrel
2-chloroethylphosphonic acid (ethephon) 相似文献
40.
The indirect chiral separation of the four stereoisomers (1)-(4) of a novel carbonic anhydrase inhibitor with two chiral centers in the molecule is reported. The method is based on chemical derivatization of the secondary amino group of the inhibitor with chiral isocyanate, formation of diastereomeric urea derivatives, each with three chiral centers in the molecule, and their separation under nonchiral HPLC conditions. The attempts to separate racemic mixture (1) + (2) from its diastereomeric counterpart (3) + (4) under nonchiral conditions, and to separate enantiomers (1) and (2) directly on a chiral stationary phase (CSP) are also reported. The indirect method was utilized for the assessment of an in vivo inversion of configuration at either one or both chiral centers of the molecule of (1). Analyses of selected whole blood and urine samples from human subjects after multiple bilateral topical ocular dosing with (1) did not reveal the presence of any of the three possible stereoisomers (2)-(4) of (1) indicating that the inversion of configuration at neither one nor two chiral centers of (1) occurs in vivo. 相似文献