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11.
A pure bacterial culture capable of utilizing either L-lysine or 2-chlorophenol (2-CP) as sole carbon source was isolated and used in continuous culture experiments to determine its response to dual substrate limitation by those two compounds. Dilution rate and feed composition were each set at three levels in a two factorial experimental design. The total chemical oxygen demand (COD) of the feed was fixed at 225 mg/L and its composition was varied by changing the ratio of lysine to 2-CP. The effects of the two independent variables (dilution rate and feed composition) on the concentrations of cells, lysine, COD, and dissolved organic carbon (DOC) in the reactors were systematic whereas the effects on the 2-CP concentration were less predictable. The concentrations of the two substrates responded to the two independent variables in a complex interactive manner which is not explained by existing models for dual, substitutable substrates. Rather, the results suggested that the prediction of the fate of a single organic component in a reactor receiving a multicomponent feed is a very difficult task. 相似文献
12.
Pedro J. N. Silva Richard K. Koehn Walter J. Diehl III Robin P. Ertl Elaine B. Winshell Mauro Santos 《Biochemical genetics》1989,27(7-8):451-467
Four samples of the musselMytilus edulis were taken between 1984 and 1987 from Stony Brook, New York, and used to study the glucose-6-phosphate isomerase (GPI) polymorphism
in this species.In vitro specific activity andin vivo flux measured in the same animals were found to be significantly correlated. A significant effect of GPI genotype on flux
was observed in one of the samples; overall, significant evidence of effect of genotype on enzyme activity was also obtained.
GPI activities of common genotypes tend to deviate less from the population mean than those of rare (frequency less than 5%)
genotypes. This suggests the possibility that rare GPI genotypes are rare as a consequence of having biochemical properties
that deviate from an optimum level and, therefore, having a lower fitness. In support of this hypothesis, we found in one
of our samples that shell length is a concave function of GPI activity with an intermediate optimum activity level.
The financial support provided to P.J.N.S. by the Luso-American Educational Commission (Fulbright Program), the Instituto
Nacional de Investigacao Científica (Portugal), and the Faculdade de Ciências da Universidade de Lisboa during several stages
of this research is gratefully acknowledged. Financial support from the Ministerio de Educatión y Ciencia (Spain) in the form
of a postdoctoral Fulbright/MEC fellowship to M.S. is also gratefully acknowledged. Research was supported by National Science
Foundation Grant BSR-8415060 to R.K.K. This is contribution No. 736 from the Program in Ecology and Evolution, State University
of New York at Stony Brook.
On leave from Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Campo Grande C2, Lisboa, Portugal. 相似文献
13.
Synopsis The behaviour of three piranha species,Serrasalmus marginatus, S. spilopleura, andPygocentrus nattereri, and their prey fishes was studied underwater in the Pantanal region, Mato Grosso, Brazil. General habits, predatory tactics, feeding behaviour, and social interactions while foraging, as well as defensive tactics of prey fishes were observed.S. marginatus is solitary whereas the other two species live in shoals; their agonistic behaviour varies accordingly, the simplest being displayed by the solitary species. Predatory tactics and feeding behaviour also vary:S. spilopleura shows the most varied diet and highly opportunistic feeding strategy, which includes aggressive mimicry. The solitaryS. marginatus, besides fin and scale-eating, occasionally cleans larger individuals ofP. nattereri. Several cichlid species display defensive tactics clearly related to piranha attacks: tail protecting, watching, and confronting the predator are the most commonly observed behaviours. Piranhas seem to strongly influence use of habitat, social structure, and foraging mode of the fish communities. 相似文献
14.
Summary For numerical solution of the reaction-mass transfer equations for immobilised biocatalysts it may be better to start integration at the particle surface and proceed inwards: calculations are targetted on the region to which practically interesting changes are often confined (because concentrations are effectively zero in the interior); and during iterative solution wrong initial estimates may be rejected after detecting anomalies early in the integration.Symbols Cb
substrate concentration in bulk (mol m–3)
- c
dimensionless substrate concentration (C/Cb) (-)
- De
effective diffusion coefficient (m2s–1)
- Da
Damkohler number (V.ro
2/De.Ks) (-)
- Ks
substrate concentration kinetic coefficient (mol m–3)
- ke
external mass transfer coefficient (ms–1)
- ro
bead radius (m)
- Sh
Sherwood number (ke.ro/De) (-)
- V
maximum rate per unit volume in beads (mol m–3s–1)
- x
dimensionless distance from bead centre (r/ro) (-)
-
dimensionless kinetic coefficient (Ks/Cb) (-)
- o
effectiveness factor (-) 相似文献
15.
Oxidation of γ-Hydroxybutyrate to Succinic Semialdehyde by a Mitochondrial Pyridine Nucleotide-Independent Enzyme 总被引:2,自引:0,他引:2
Elaine E. Kaufman Thomas Nelson David Miller Noam Stadlan 《Journal of neurochemistry》1988,51(4):1079-1084
An antibody that inhibits over 95% of the cytosolic NADP+-dependent gamma-hydroxybutyrate (GHB) dehydrogenase activity of either rat brain or kidney was found to inhibit only approximately 50% of the conversion of [1-14C]GHB to 14CO2 by rat kidney homogenate. A similar result was obtained with sodium valproate, a potent inhibitor of GHB dehydrogenase. The mitochondrial fraction from rat brain and kidney was found to catalyze the conversion of [1-14C]GHB to 14CO2. The dialyzed mitochondrial fraction also catalyzed the oxidation of GHB to succinic semialdehyde (SSA) in a reaction that did not require added NAD+ or NADP+ and which was not inhibited by sodium valproate. The enzyme from the mitochondrial fraction which converts GHB to SSA appears to be distinct from the NADP+-dependent cytosolic oxidoreductase which catalyzes this reaction. 相似文献
16.
17.
William P. Norred Elaine Wang Hwansoo Yoo Ronald T. Riley Alfred H. Merrill Jr. 《Mycopathologia》1992,117(1-2):73-78
The effects of fumonisins B1FB1, B2(FB{2}), and the backbone of fumonisin B1 remaining after hydrolysis of the tricarballylic groups with base (HFB1) on sphingolipid biosynthesis were studied in both primary rat hepatocytes and pig kidney epithelial cells (LLC-PK1). Fumonisins were potent inhibitors of sphingolipid biosynthesis in hepatocytes (IC50 of FB1=0.1 M), but overt toxicity was not observed. In renal cells, fumonisins also inhibited sphingosine biosynthesis (IC50 for FB1=35 M), and caused decreased cell proliferation as well. Higher doses (70 M) killed renal cells after exposure for 3 days. The inhibition of de novo sphingolipid biosynthesis was specific, and appeared to be at the site of ceramide synthase, which catalyzes the formation of dihydroceramide or ceramide by the addition of the amide-linked fatty acid to sphinganine or sphingosine. These results may account for the ability of fumonisins to cause equine leucoencephalomalacia and to promote tumor formation. 相似文献
18.
Regeneration of transgenic plants of Prunus armeniaca containing the coat protein gene of Plum Pox Virus 总被引:1,自引:0,他引:1
Margit Laimer da Câmara Machado Artur da Câmara Machado Veronika Hanzer Hans Weiss Ferdinand Regner Herta Steinkellner Diethard Mattanovich Regina Plail Elisabeth Knapp Birgit Kalthoff Hermann Katinger 《Plant cell reports》1992,11(1):25-29
Summary A system was developed which allows the transfer of foreign genes into apricot cultivars. We report the transformation and regeneration of Prunus armeniaca plants with Agrobacterium tumefaciens strain LBA 4404 containing various binary plasmids, pBinGUSint, carrying the marker gene ß-glucuronidase (GUS) and pBinPPVm, carrying the coat protein gene of Plum Pox Virus (PPV). The marker gene GUS was used for optical evaluation of the efficiency of the transformation system. The coat protein gene of PPV was used to introduce coat protein mediated resistance against one of the most important pathogens of stone fruit trees in Europe and the whole Mediterranean area. This is the first report of the successful integration of a viral coat protein gene into a fruit tree species, opening a new perspective on the control of the disease.Abbreviations GUS
ß-glucuronidase
- PPV
Plum Pox Virus
- BA
6-benzylaminopurine
- NPTII
neomycin phosphotransferase II
- CP
coat protein
- CaMV
Cauliflower Mosaic Virus
- P35S 35S
promoter
- MS
Murashige and Skoog
- PCR
polymerase chain reaction
- P/C/I
phenol/chloroform/isoamylalcohol
- RNase
ribonuclease
- dNTP
deoxyribonucleosidetriphosphate
- DMSO
dimethyl sulfoxide 相似文献
19.
The expression of proteins that play a role in neuronal differentiation was examined in central nervous system (CNS) micromass embryo cell cultures and compared to expression at comparable developmental stages in vivo. The protein product of the src proto-oncogene (pp60c-src) has been postulated to have a specific role in development because, although it is expressed in many tissues, marked increases in amount and activity of pp60c-src
occur in neurons at the time of differentiation. Another protein of interest, high molecular weight neurofilament (NF) protein, is found in differentiated neurons. In the present study, changes over time in the expression of these two proteins in vitro and in vivo were examined. In the micromass cell cultures, primary cells from day 12 rat embryo CNS are plated at high density and differentiate into neurons during five days in culture. Tissues from embryos grown in vivo were assessed at 12 and 17 days post-coitum. Proteins were quantified by PAGE separation of equal amounts of total protein followed by transfer to membranes, immunoblotting, and densitometric scanning of blots. Increases in the amount of both proteins with neuronal differentiation was shown. Protein kinase activity of immunoprecipitated pp60c-src
also increased in cell cultures and in embryos. Similarity in patterns of expression between in vitro and in vivo tissue samples provides further evidence that the cultures closely simulate in vivo differentiation and are a useful system for examining expression of developmental genes in vitro.Abbreviations BCIP
5-bromo-4-chloro-3-indolylphosphate p-toluidine salt
- CNS
central nervous system
- DPBS
Dulbecco's phosphate-buffered saline
- GAM-AP
goat anti-mouse IgG alkaline phosphatase conjugate
- LB
limb bud
- NF
high molecular weight neurofilament protein
- NBT
nitroblue tetrazolium chloride
- SDS-PAGE
polyacrylamide gel electrophoresis
- PVDF
polyvinylidene difluoride
- RIPA
radioimmunoprecipitation
- TBS
Tris-buffered saline
- TTBS
TBS with 0.05% Tween-20
Presented in part at the 1989 and 1990 Teratology Society Meetings and the 1990 Society of Toxicology Meetings. 相似文献
20.
J. E. Irvine G. T. A. Benda B. L. Legendre G. R. Machado Jr 《Plant Cell, Tissue and Organ Culture》1991,26(2):115-125
This study investigates the frequency of apparent and permanent expression of marker change following two types of tissue culture, conventional callus and direct regeneration cultures, and for two markers it relates this frequency to that following breeding. Each clone was used for only one marker. After conventional callus culture, plants of the sugarcane clone Arundoid B, a clone having a growth habit with shortened internodes and leaves, were freed of this marker at a rate of 1 in 172 plants. Marker remission in a second clone with a leaf blotch was enhanced in the presence of a mutagen. Callus culture alone gave a remission rate of 1/280 plants, while treatment of callus with ethyl methanesulfonate gave a remission rate of 1/42 plants. Of two markers subjected to vegetative and sexual transmission, the first, a leaf marker, was stable in callus culture with no remissions; crossing with non-marker parents produced progeny with 54% lacking the marker. The second, a stalk marker (multibud), showed epigenetic effects during two generations of vegetative propagation; plants lacking the multibud marker produced vegetative progeny in which the marker reappeared. Nine crosses to nonmarker parents produced progeny of which an average of 29% had the marker. The use of stalk chimeras as markers demonstrated that passage through conventional callus or direct regeneration culture resulted in the loss of the donor phenotype in all plants regenerated. Phenotypic variation in plants derived from callus culture appears to arise from several sources; chimeral segregants, epigenetic transients, and mutational variants. 相似文献