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951.
Hiner AN Hernández-Ruíz J Arnao MB García-Cánovas F Acosta M 《Biotechnology and bioengineering》1996,50(6):655-662
Horseradish peroxidase (HRP) is a commercially important enzyme that is available from a number of supply houses in a variety of grades of purity and isoenzymic combinations. The present article describes a comparative study made on nine HRP preparations. Six of these samples were predominantly composed of basic HRP, pl 8.5, and three of acidic HRP, pl 3.5. Two of the basic preparations were of lower purity than the others. The apparent molar catalytic activity of basic HRP with 0.5 mMABTS and 0.2 mM H(2)O(2) was around 950 s(-1) (about 770 s(-1) for the less pure samples) and with a 5 mM guaiacol and 0.6 mM H(2)O(2) was about 180 s(-1) for all the samples. A similar value (approximately 1000 s(-1)) was observed for acidic HRP but only at higher concentrations of ABTS (20 mM). With 20 mM guaiacol the molar catalytic activity of the acid isoenzyme was 65 s(-1). The apparent K(M) for ABTS of the acidic isoenzyme was 4 mM whereas for the basic isoenzyme it was 0.1 mM. All the enzymes were inactivated by H(2)O(2) when it was supplied as the only substrate. Under these conditions the partition ratio (r = number of catalytic cycles given by the enzyme before its inactivation), apparent dissociation constant (K(l)), and apparent rate constant of inactivation (k(inact)) were about twice as large for the acidic samples (1350, 2.6 mM, 9 . 10(-3) s(-1)) as for the basic (650, 1.3 mM, 5 . 10(-3) s(-1)). The apparent catalytic constant (k(cat)) was 3-4 times larger, and the efficiency of catalysis (k(cat)/K(l)) was double for the acidic isoenzyme, but the efficiency of inactivation (k(inact)/K(l)) was similar. The data obtained provide useful information for those using HRP isoenzymes for biotechnological applications (e.g., biosensors, bioreactors, or assays). (c) 1996 John Wiley & Sons, Inc. 相似文献
952.
The distribution of Keratella species from 15 different lakes in North Patagonia (Argentina) was analysed. The genus was not present at altitudes above 1000 m. K. tropica was restricted to Patagonian Plateau lakes with a comparatively high conductivity. A morphometric analysis of the widely distributed K. cochlearis was performed. Results showed three groups of K. cochlearis corresponding to Andean lakes, Patagonian Plateau lakes and a Patagonian Reservoir. 相似文献
953.
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
954.
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
955.
956.
A preliminary report on the use of transfer factor for treating stage D3 hormone-unresponsive metastatic prostate cancer 总被引:4,自引:0,他引:4
Dr. Giancarlo Pizza Caterina De Vinci Diego Cuzzocrea Domenico Menniti Ernesto Aiello Paolo Maver Giuseppe Corrado Piero Romagnoli Ennio Dragoni Giuseppe LoConte Umberto Riolo Aldopaolo Palareti Paolo Zucchelli Vittorio Fornarola Dimitri Viza 《Biotherapy》1996,9(1-3):123-132
As conventional treatments are unsuccessful, the survival rate of stage D3 prostate cancer patients is poor. Reports have
suggested the existence of humoral and cell-mediated immunity (CMI) against prostate cancer tumour-associated antigens (TAA).
These observations prompted us to treat stage D3 prostate cancer patients with an in vitro produced transfer factor (TF) able
to transfer, in vitro and in vivo, CMI against bladder and prostate TAA. Fifty patients entered this study and received one
intramuscular injection of 2–5 units of specific TF monthly. Follow-up, ranging from 1 to 9 years, showed that complete remission
was achieved in 2 patients, partial remission in 6, and no progression of metastatic disease in 14. The median survival was
126 weeks, higher than the survival rates reported in the literature for patients of the same stage. 相似文献
957.
958.
Populations ofLuzula multiflora s.l. in Ireland were examined karyologically. Plants from 14 populations were invariably tetraploid with 2n=24. Chromosomes of the tetraploid are of AL type (true tetraploidy). Meiosis of the tetraploids is of the same type as described for otherLuzula taxa in the literature. In meiosis, 12 bivalents are regularly formed. A hypothesis based on the morphological and allozyme data, that the tetraploids are of alloploid origin, is supported by the present results. Meiosis in an artificial hybrid between the presumed parental taxa,L. campestris andL. pallidula, was studied; a certain tendency towards chromosome doubling was observed. The geographical distribution of theL. multiflora cytotypes is also discussed. 相似文献
959.
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
960.
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