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1.
Stability and procured instability characterize two opposing types of swimming, steady and maneuvering, respectively. Fins can be used to manipulate flow to adjust stability during swimming maneuvers either actively using muscle control or passively by structural control. The function of the dorsal fins during turning maneuvering in two shark species with different swimming modes is investigated here using musculoskeletal anatomy and muscle function. White‐spotted bamboo sharks are a benthic species that inhabits complex reef habitats and thus have high requirements for maneuverability. Spiny dogfish occupy a variety of coastal and continental shelf habitats and spend relatively more time cruising in open water. These species differ in dorsal fin morphology and fin position along the body. Bamboo sharks have a larger second dorsal fin area and proportionally more muscle insertion into both dorsal fins. The basal and radial pterygiophores are plate‐like structures in spiny dogfish and are nearly indistinguishable from one another. In contrast, bamboo sharks lack basal pterygiophores, while the radial pterygiophores form two rows of elongated rectangular elements that articulate with one another. The dorsal fin muscles are composed of a large muscle mass that extends over the ceratotrichia overlying the radials in spiny dogfish. However, in bamboo sharks, the muscle mass is divided into multiple distinct muscles that insert onto the ceratotrichia. During turning maneuvers, the dorsal fin muscles are active in both species with no differences in onset between fin sides. Spiny dogfish have longer burst durations on the outer fin side, which is consistent with opposing resistance to the medium. In bamboo sharks, bilateral activation of the dorsal in muscles could also be stiffening the fin throughout the turn. Thus, dogfish sharks passively stiffen the dorsal fin structurally and functionally, while bamboo sharks have more flexible dorsal fins, which result from a steady swimming trade off. J. Morphol. 274:1288–1298, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
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3.
Household‐level correlates of children's physical activity levels in and across 12 countries 下载免费PDF全文
Deirdre M. Harrington Fiona Gillison Stephanie T. Broyles Jean‐Philippe Chaput Mikael Fogelholm Gang Hu Rebecca Kuriyan Anura Kurpad Allana G. LeBlanc Carol Maher Jose Maia Victor Matsudo Timothy Olds Vincent Onywera Olga L. Sarmiento Martyn Standage Mark S. Tremblay Catrine Tudor‐Locke Pei Zhao Peter T. Katzmarzyk for the ISCOLE Research Group 《Obesity (Silver Spring, Md.)》2016,24(10):2150-2157
4.
5.
M N Simon T Winckler R Mutzel M Véron J C da Costa Maia 《Biochemical and biophysical research communications》1992,184(3):1142-1151
Extracts from Dictyostelium discoideum contain type 2A and 2C serine/threonine-specific protein phosphatases with properties very similar to those from mammals according to their sensitivity to okadaic acid and to their dependence for divalent cations. In contrast, no type 1 protein phosphatase is found at any time of development, neither in the cytosolic nor in the particulate fraction, using glycogen phosphorylase a, casein, histone or the non-proteinous 4-Methylumbelliferyl phosphate as substrates. Both type 2A and 2C protein phosphatase activities remain constant throughout the development cycle. 相似文献
6.
We have broadly defined the DNA regions regulating esterase6 activity in
several life stages and tissue types of D. melanogaster using P-
element-mediated transformation of constructs that contain the esterase6
coding region and deletions or substitutions in 5' or 3' flanking DNA.
Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and
the primary sequences regulating its activity lie between -171 and -25 bp
relative to the translation initiation site: deletion of these sequences
decrease activity approximately 20-fold. Hemolymph activity is also
modulated by four other DNA regions, three of which lie 5' and one of which
lies 3' of the coding region. Of these, two have positive and two have
negative effects, each of approximately twofold. Esterase6 activity is
present also in two male reproductive tract tissues; the ejaculatory bulb,
which is another ancestral activity site, and the ejaculatory duct, which
is a recently acquired site within the melanogaster species subgroup.
Activities in these tissues are at least in part independently regulated:
activity in the ejaculatory bulb is conferred by sequences between -273 and
-172 bp (threefold decrease when deleted), while activity in the
ejaculatory duct is conferred by more distal sequences between -844 and
-614 bp (fourfold decrease when deleted). The reproductive tract activity
is further modulated by two additional DNA regions, one in 5' DNA (-613 to
-284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to
+2731 bp; threefold decrease when deleted) that probably overlaps the
adjacent esteraseP gene. Collating these data with previous studies
suggests that expression of EST6 in the ancestral sites is mainly regulated
by conserved proximal sequences while more variable distal sequences
regulate expression in the acquired ejaculatory duct site.
相似文献
7.
Developmental regulation of hexosamine biosynthesis by protein phosphatases 2A and 2C in Blastocladiella emersonii. 下载免费PDF全文
L C Etchebehere M N Simon R B Campanh P D Zapella M Vron J C Maia 《Journal of bacteriology》1993,175(16):5022-5027
Extracts of the aquatic fungus Blastocladiella emersonii were found to contain protein phosphatases type 1, type 2A, and type 2C with properties analogous to those found in mammalian tissues. The activities of all three protein phosphatases are developmentally regulated, increasing during sporulation, with maximum level in zoospores. Protein phosphatases 2A and 2C, present in zoospore extracts, catalyze the dephosphorylation of L-glutamine:fructose-6-phosphate amidotransferase (EC 2.6.1.16, amidotransferase), a key regulatory enzyme in hexosamine biosynthesis. The protein phosphatase inhibitor okadaic acid induces encystment and inhibits germ tube formation but does not affect the synthesis of the chitinous cell wall. These results strongly suggest that phosphatase 2C is responsible for the dephosphorylation of amidotransferase in vivo. This dephosphorylation is inhibited by uridine-5'-diphospho-N-acetylglucosamine, the end product of hexosamine synthesis and the substrate for chitin synthesis. This result demonstrates a dual role of uridine-5'-diphospho-N-acetylglucosamine by inhibiting the activity of the phosphorylated form of amidotransferase and by preventing its dephosphorylation by protein phosphatases. 相似文献
8.
Adjustments in the geometry of the separation zone of an inclined parallel plate sedimenter, previously developed, permitted an extensive increase in the volumetric clarification rate of broth containing yeast (S. cerevisiae). The prototype, having an internal capacity of 1340 ml, was fed with fermentation broth containing 18.8% v/v cells, while 16.4 ml/min of clarified broth containing 0.3% v/v cells was removed in the overflow. The underflow, containing 23.8% v/v cells, was recycled to the fermenter at a rate of 60.6 ml/min. These results demonstrated the viability of using exclusively gravitational sedimentation for cellular recycling in continuous alcoholic fermentation. Without a doubt, this system represents the simplest technological alternative among those thus far proposed for continuous alcoholic fermentation. The low cost of installation, maintenance and operation permitted projection of its application for any scale of production.List of Symbols
A
Cross sectional area of the sedimentation zone
-
b
Distance between two parallel plates, height of the triangle or diameter of the circle (for rectangular, triangular or circular cross sections of the sedimentation zone, respectively)
-
b
Mean distance travelled by the cells during sedimentation within the sedimentation zone with each cross sectional geometry
-
B
f
Biomass content of the fermentation broth
-
B
o
Biomass content of the overflow
-
B
u
Biomass content of the underflow
-
Eff.
Sedimentation efficiency
-
f
Factor corresponding to the clarification velocity obtained with a certain cross sectional geometry relative to that obtained with the rectangular sedimentation zone geometry
-
g
Gravitational acceleration
-
H
Length of the plates
-
Q
a
Clarification rate
-
Q
f
Feed rate
-
Q
o
Overflow rate
-
Q
u
Underflow rate
-
rect
Indicates a rectangular cross section
-
S
Total sedimentation area (horizontal projection of the internal contour of the sedimentation zone
-
tr
Indicates a triangular cross section
- s
Linear settling velocity of one cell in the broth
- v
Linear clarification velocity of the broth in a vertical sedimenter = s
-
Linear clarification velocity of the broth in an inclined sedimenter of slope
-
Slope of the sedimentation zone relative to the horizontal
-
Porosity factor = 1 — (volume fraction of cells)
-
cell
Cell density
-
m
Density of the medium
-
broth
Broth viscosity 相似文献
9.
Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans 总被引:2,自引:0,他引:2
Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and
D. simulans for two common allozyme forms, as well as for several other
less common variants. Parallel latitudinal clines in the frequencies of the
common EST6-F and EST6-S allozymes in these species have previously been
interpreted in terms of a shared amino acid polymorphism that distinguishes
the two variants and is subject to selection. Here we compare the sequences
of four D. simulans Est-6 isolates and show that overall estimates of
nucleotide heterozygosity in both coding and 5' flanking regions are more
than threefold higher than those obtained previously for this gene in D.
melanogaster. Nevertheless, the ratio of replacement to exon silent-site
polymorphism in D. simulans is less than the ratio of replacement to silent
divergence between D. simulans and D. melanogaster, which could be the
result of increased efficiency of selection against replacement
polymorphisms in D. simulans or to divergent selection between the two
species. We also find that the amino acid polymorphisms separating EST6- F
and EST6-S in D. simulans are not the same as those that separate these
allozymes in D. melanogaster, implying that the shared clines do not
reflect shared molecular targets for selection. All comparisons within and
between the two species reveal a remarkable paucity of variation in a
stretch of nearly 400 bp immediately 5' of the gene, indicative of strong
selective constraint to retain essential aspects of Est-6 promoter
function.
相似文献
10.
Silvia M.C. Dias João B. Fernandes José G.S. Maia Otto R. Gottlieb Hugo E. Gottlieb 《Phytochemistry》1982,21(7):1737-1740
The trunk wood of an Amazonian Aniba (Lauraceae) species contains, besides dillapiol and the benzodioxane-type neolignan eusiderin, four bicyclo(3.2.1)octanoid neolignans. These comprise representatives of the canellin-type: the known methoxycanellin-A and the novel compounds characterized as (1R, 3S, 4S, 5S, 6S, 7R)-1-allyl-4-hydroxy-3, 5-dimethoxy-7-methyl-6-(3′-methoxy-4′, 5′-methylenedioxyphenyl)-8-oxo-bicyclo(3.2.1)octane; (1R, 3S, 4S, 5S, 6S, 7R)-1-allyl-4-hydroxy-3, 5-dimethoxy-7-methyl-6-(3′, 4′, 5′-trimethoxyphenyl)-8-oxobicyclo(3.2.1)octane and (1R, 4R, 5R, 6S, 7R, 8S)-1-allyl-4, 8-dihydroxy-5-methoxy-7-methyl-6-(3′-methoxy-4′,5′-methylenedioxyphenyl)-3-oxobicyclo(3.2.1)octane. 相似文献