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971.
Fieldwork in connection with the project to document the flora of the Mixteca Alta region, northwestern Oaxaca, Mexico, has resulted in the discovery of a new species, Ageratina pendula. 相似文献
972.
Relationship between the levels of wheat-rye metaphase I chromosomal pairing and recombination revealed by GISH 总被引:3,自引:0,他引:3
The metaphase I and anaphase I stages of meiosis of wheat×rye hybrids carrying the ph1b mutation were analyzed by genomic in situ hybridization. This technique allows distinction between three different types of
wheat-rye associations in metaphase I configurations as well as detection of wheat-rye recombinant chromosomes in anaphase
I cells. The frequency of associations between wheat and rye chromosomes greatly exceeded the level of wheat-rye recombination
found in the three hybrids examined. Extremely distal associations, which account for about 50% of the total wheat-rye metaphase
I chromosomal pairing, can explain such a discrepancy between metaphase I and anaphase I data. It is further discussed whether
these associations reflect very distally located chiasmata or nonchiasmatic pairing. The sizes of the segments exchanged in
wheat-rye recombinant chromosomes provide cytological evidence that wheat-rye recombination is restricted to the distal chromosomal
regions.
Received: 24 August 1995; in revised form: 27 February 1996 / Accepted: 28 March 1996 相似文献
973.
Kjetil Taskn Rigmor Solberg Ying Zhao Vidar Hansson Tore Jahnsen Michael J. Siciliano 《Genomics》1996,36(3):535
We have determined the chromosomal localization of the gene for the catalytic subunit Cα of cAMP-dependent protein kinase (locus PRKACA) to human chromosome 19 using polymerase chain reaction (PCR) and Southern blot analysis of two different somatic cell hybrid mapping panels. In addition, PCR analysis of a chromosome 19 mapping panel revealed the presence of a human Cα-specific amplification product only in cell lines containing the region 19p13.1 to 19q12. Finally, two-color fluorescencein situhybridization to metaphase chromosomes using the human Cα cDNA and human chromosome 19 inter-Alu-PCR product as probes localized the human Cα gene to chromosome region 19p13.1. 相似文献
974.
Zuhal Keskil Cem Z. G rgü n Ugur Hodoglugil Hakan Zengil 《Chronobiology international》1996,13(6):465-475
The presence of time-dependent variations in the in vitro sensitivity of aorta preparations to either vasoconstricting or relaxing agents was investigated in rats maintained in light from 08: 00 to 20: 00 and in darkness from 20: 00 to 08: 00. Rat thoracic aorta rings were obtained from animals sacrificed at four different times of the day. The rat aorta was found to be more sensitive to the constricting effect of phenylephrine at 15: 00, and of 5-hydroxytryptamine at 21: 00. On the other hand, both endothelium-dependent and -independent relaxations were more remarkable at 03: 00 than at other times of the day. These variations represented significant circadian rhythms when analyzed by analysis of variance. Different in vitro responsiveness to these agents might reflect changes in the sensitivity and/or number of related receptors in vascular preparations. In conclusion, the circadian time of animal sacrifice to obtain vascular preparations constitutes an important aspect of the research method and a key determinant of findings. (Chronobiology International, 13(6), 465-475, 1996) 相似文献
975.
We have earlier isolated a glucocorticoid-resistant, dedifferentiated rat hepatoma variant, the clone 2, which exhibited deficient stress activation of the major stress-inducible heat-shock protein hsp68.Multidrug-resistant variants were isolated from clone 2 cells using increasing concentrations of colchicine. The induction deficiency of hsp68 was maintained in the colchicine-resistant clone 2 cells grown for several months in the presence of 1 g/ml colchicine (termed ashighly multidrug-resistant variant) indicating that this heat-shock protein is not involved in the multidrug resistance. No alteration of the protein synthesis pattern was observed except the strong increase of the P-glycoprotein, which correlated with high level of corresponding mRNA. Stableheat-resistant variants of clone 2 were also isolated, which showed increaseddrug resistance to several drugs, i.e. they becamemoderately multidrug-resistant. This moderate multidrug resistance of the heat-resistant variants was further increased by stepwise selection with colchicine (highly multidrug-resistant heat-resistant variants). The levels of P-glycoprotein mRNA and protein were elevated both in the heat-resistant, non drug selected, moderately drug-resistant and in heatresistant, colchicine selected, highly drug-resistant variants. Decreased retention of antitumor drugs was observed in all multidrug-resistant variants indicating that P-glycoprotein was functional. Verapamil increased doxorubicin retention and cytotoxicity significantly. Our results showing that severely stressed hepatoma cells overexpressed the multidrug resistance gene(s) raise the possibility that the P-glycoprotein may participate in protection against enviromental stress such as heat.Abbreviations hsp
heat-shock protein
- MDR
multidrug resistance
- P-gp
P-glycoprotein 相似文献
976.
Isolation of an anaerobic bacterium which reductively dechlorinates tetrachloroethene and trichloroethene 总被引:5,自引:0,他引:5
Strain TEA, a strictly anaerobic, motile rod with one to four lateral flagella and a crystalline surface layer was isolated from a mixed culture that completely reduces chlorinated ethenes to ethene. The organism coupled reductive dehalogenation of tetrachloroethene or trichloroethene to cis-1,2-dichloroethene to growth, using molecular hydrogen as the electron donor. It was unable to grow fermentatively or in the presence of tri- or tetrachloroethene with glucose, pyruvate, lactate, acetate or formate. The 16S rDNA sequence of strain TEA was 99.7% identical to that of Dehalobacter restrictus. The two organisms thus are representatives of the same species or the same genus within the Bacillus/Clostridium subphylum of the gram-positive bacteria. 相似文献
977.
978.
Kristian Aspegren Leena Mannonen Anneli Ritala Riitta Puupponen-Pimiä Ulrika Kurtén Marjatta Salmenkallio-Marttila Veli Kauppinen Teemu H. Teeri 《Molecular breeding : new strategies in plant improvement》1995,1(1):91-99
Transgenic plant cell cultures have a potential for production and secretion of important proteins and peptides. To assess the possibilities of using a stable barley suspension culture for secretion of heterologous proteins in active form, we expressed the cDNA of the thermostable-glucanase (EGI) ofTrichoderma reesei in barley suspension cells. The cDNA coding for EGI and its signal sequence was placed under the control of the CaMV 35S promoter and the construction was transferred to the cells by particle bombardment. Stably transformed lines were obtained by selecting for a cotransformed antibiotic resistance marker. The expression of EGI cDNA led to accumulation of EGI in the culture medium, as shown by analysis with EGI-specific antibodies. Enzymatic assays confirmed that the EGI secreted by the suspension cells retained its activity and thermostable character. Furthermore, it was shown that the enzyme produced by the transgenic suspension culture could be used for degradation of soluble-glucans during mashing. 相似文献
979.
The influence of mediterranean pine vole (Microtus (Terricola) duodecimcostatus) mound-building activity in two Western Spanish Pyrenees plant communities (Mesobromion erecti and Festucion eskiae-Nardion strictae) were studied. The plants colonizing the gaps in these areas are different in the two cases considered. The plant composition of surrounding plant communities seems to be the main factor in revegetation. Mound-building activity changes the species' relative frequency and life-form spectrum, decreases the monocytyledonous/dicotyledonous ratio and increases diversity by diminishing the presence of dominant plant species.Abbreviations ME
Mesobromion erecti
- FN
Festucion eskiae-Nardion strictae
- (monocots)
Monocotyledonous
- (dicots)
Dicotyledonous 相似文献
980.
Enzyme production in a cell recycle fermentation system was studied by computer simulations, using a mathematical model of -amylase production by Bacillus amyloliquefaciens. The model was modified so as to enable simulation of enzyme production by hypothetical organisms having different production kinetics at different fermentation conditions important for growth and production. The simulations were designed as a two-level factorial assay, the factor studied being fermentation with or without cell recycling, repression of product synthesis by glucose, kinetic production constants, product degradation by a protease, mode of fermentation, and starch versus glucose as the substrate carbon source.The main factor of importance for ensuring high enzyme production was cell recycling. Product formation kinetics related to the stationary growth phase combined with continuous fermentation with cell recycling also had a positive impact. The effect was greatest when two or more of these three factors were present in combinations, none of them alone guaranteeing a good result. Product degradation by a protease decreased the amount of product obtained; however, when combined with cell recycling, the protease effect was overshadowed by the increased production. Simulation of this type should prove a useful tool for analyzing troublesome fermentations and for identifying production organisms for further study in integrated fermentation systems.List of Symbols
a
proportionality constant relating the specific growth rate to the logarithm of G (h)
-
a
1
reaction order with respect to starch concentration
-
a
2
reaction order with respect to glucose concentration
-
c
starch concentration (g/l)
-
c
0
starch concentration in the feed (g/l)
-
D
dilution rate (h–1)
-
e
intrinsic intracellular amylase concentration (g product/g cell mass)
-
E
extracellular amylase concentration (g/l)
-
F
volumetric flow rate (l/h)
-
G
average number of genome equivalents of DNA/cell
-
K
1
intracellular repression constant
-
K
2
intracellular repression constant
-
K
s
Monod saturation constant (g/l)
-
k
3
product excretion rate constant (h–1)
-
k
I
translation constant (g product/g mRNA/h)
-
k
d
first order decay constant (h–1)
-
k
dw
first order decay constant (h–1)
-
k
gl
rate constant for glucose production (g/l/h)
-
k
m, dgr
saturation constant for product degradation (g/l)
-
k
st
rate constant for starch hydrolysis (g/l/h)
-
k
t1
proportionality constant for amylase production (g mRNA/g substrate)
-
k
t2
proportionality constant for amylase production (g mRNA *h/g substrate)
-
k
w
protease excretion rate constant (h–1)
-
k
wt1
proportionality constant for protease production (g mRNA/g substrate)
-
k
wt2
proportionality constant for protease production (g mRNA *h/g substrate)
-
k
wI
translation constant (g protease/g mRNA/h)
-
m
maintenance coefficient (g substrate/g cell mass/h)
-
n
number of binding sites for the co-repressor on the cytoplasmic repressor
-
Q
repression function, K1/K2 less than or equal to 1.0
-
Q
w
repression function, K1/K2 less than or equal to 1.0
-
r
intrinsic amylase mRNA concentration (g mRNA/g cell mass)
-
r
m
intrinsic protease mRNA concentration (g mRNA/g cell mass)
-
R
ex
retention by the filter of the compounds x=: C starch, E amylase, or S glucose
-
R
t
amylase transport rate (g product/g cell mass/h)
-
R
wt
protease transport rate (g protease/g cell mass/h)
-
R
s
rate of glucose production (g/l/h)
-
R
c
rate of starch hydrolysis (g/l/h)
-
S
0
feed concentration of free reducing sugar (g/l)
-
s
extracellular concentration of reducing sugar (g/l)
-
t
time (h)
-
V
volume (1)
-
w
intracellular protease concentration (g/l)
-
W
extracellular protease concentration (g/l)
-
X
cell mass concentration (dry weight) (g/l)
-
Y
yield coefficient (g cell mass/g substrate)
-
substrate uptake (g substrate/g cell mass/h)
-
specific growth rate of cell mass (h–1)
-
d
specific death rate of cells (h–1)
-
m
maximum specific growth rate of cell mass (h–1)
-
m,dgr
maximum specific rate of amylase degradation (h–1)
This study was supported by the Nordic Industrial Foundation Bioprocess Engineering Programme and the Center for Process Biotechnology, The Technical University of Denmark. 相似文献