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91.
Summary The influence of shear forces on adherent mammalian cells was investigated by means of a developed flow chamber. The viability of the cells decreased with increasing exposure level and duration. Additional, changes in the morphology of the cells due to the shear forces were observed.
Offprint requests to: G. Kretzmer 相似文献
92.
Fröhlich S Lotz M Larson B Lübbert A Schügerl K Seekamp M 《Biotechnology and bioengineering》1991,38(1):56-64
The local properties of the dispersed gas phase (gasholdup, bubble diamater, and bubble velocity) were measured and evaluated at different positions in the riser and downcomer of a pilot plant reactor and, for comparison, in a laboratory reactor. These were described in Parts I and II of this series of articles during yeast cultivation and with model media. In the riser of the pilot plant reactor, the local gas holdup and bubble velocities varied only slightly in axial direction. The gas holdup increased considerably, while the bubble velocity increased only slightly with aeration rate. The bubble size diminished with increasing distance from the aerator in the riser, since the primary bubble size was larger than the equilibrium bubble size. In the downcomer, the mean bubble size was smaller than in the riser. The mean bubble size varied only slightly, the bubble velocity was accelerated, and the gas holdup decreased from top to bottom in the downcomer. In pilot plant at constant aeration rate, the properties of the dispersed phase were nearly constant during the batch cultivation, i.e., they depended only slightly on the cell concentration. In the laboratory reactor, the mean bubble sizes were much larger than in the pilot plant reactor. In the laboratory reactor, the bubble velocities in the riser and downcomer increased, and the mean gas holdup and bubble diameter in the downcomer remained constant as the aeration rate was increased. 相似文献
93.
Summary The transmembrane permeation rate of the medium and the membrane transmission of low- and high-molecular medium components were evaluated for a microfiltration sampling system as a function of the operation time. 相似文献
94.
An apparatus for the detailed investigation of the influence of shear stress on adherent BHK cells was developed. Shear forces between 0.0 and 2.5 N m-2 were studied. The influence on cell viability, cell morphology, cell lysis, and cell size was determined. Increasing shear forces as well as increasing exposure duration caused increasing changes in cell morphology and cell death. A "critical shear stress level" was determined. 相似文献
95.
96.
E. Coli was cultivated in batch and continuous operations in the presence of an antifoam agent in stirred-tank and in single- and ten-stage airlift tower reactors with an outer loop. The maximum specific growth rate, mu(m), the substrate yield coefficient, Y(x/s), the respiratory quotient, RQ, substrate conversion, U(s), the volumetric mass transfer coefficient, K(L)a, the specific interfacial area, a, and the specific power input, P/V(L), were measured and compared. If a medium is used with a concentration of complex substrates (extracts) 2.5 times higher than that of glucose, a spectrum of C sources is available and cell regulation influences reactor performance. Both mu(m) and Y(X/S), which were evaluated in batch reactors, cannot be used for continuous reactors or, when measured in stirred-tank reactors, cannot be employed for tower-loop reactors: mu(m) is higher in the stirred-tank batch than in the tower-loop batch reactor, mu(m) and Y(x/s) are higher in the continuous reactor than in the batch single-stage tower-loop reactor. The performance of the single-stage is better than that of the ten-stage reactor due to the inefficient trays employed. A reduction of the medium recirculation rate reduces OTR, U(s), Pr, and Y(X/S) and causes cell sedimentation and flocculation. The volumetric mass transfer coefficient is reduced with increasing cultivation time; the Sauter bubble diameter, d(s), remains constant and does not depend on operational conditions. An increase in the medium recirculation rate reduces k(L)a. The specific power input, P/V(L), for the single-stage tower loop is much lower with the same k(L)a value than for a stirred tank. The relationship k(L)a vs. P/V(L) evaluated for model media in stirred tanks, can also be used for cultivations in these reactors. 相似文献
97.
Summary The influence of the concentrations of NaCl, NaJ, KJ and/or Na2SO4 on the foaminess of BSA solutions is investigated. The foaminess increases with increasing salt concentrations as expected for NaCl, NaJ and Na2SO4. With KJ the foaminess exhibits an anomaly. The dependence of the foaminess on the pH is complex. In the presence of buffer there is a minimum at 4.81 and a maximum at 4.7. In the absence of buffer the foaminess reaches a maximum at pH 4 and a minimum at 3. The anomaly of BSA solutions is well-known but not yet fully understood.Symbols BSA
Bovine Serum Albumin
- C
concentration
- CBSA
concentration of BSA
- CBUFFER
concentration of buffer
- CSALT
concentration of salt
- Vs
equilibrium volume of the foam
- Vtg
volumetric gas flow rate
- =Vs/Vtg
foaminess 相似文献
98.
Summary Electrooptical and light scattering methods for measuring the structure of two phase flow, especially bubble size, are described and compared with photographic and electrical conductivity methods.Symbols L
length
- T
time
- M
mass
- d
bubble diameter
-
mean bubble diameter
- dK
inside diameter of the sensor capillary
-
1
longitudinal distance between start and stop sensors
-
1B
pierced length of bubble
- t
time
-
t1
length of square-wave signal at start sensor
-
t2
length of square-wave signal at stop sensor
-
112
time delay between start and stop signals
- VB
bubble volume
- VB
bubble velocity
- wSG
superficial gas velocity 相似文献
99.
Summary The photographic and electrical conductivity methods to measure the structure of two phase flow, especially bubble size, bubble frequency, local gas hold-up and, for the latter, the bubble velocity are described.Symbols
specific interfacial area
- a
gas/liquid interfacial area
- B
constant in Eq. (4)
- d
diameter of the bubbles
- d
mean diameter of the bubbles
- dS
Sauter diameter
- EG
relative gas hold up
- I
current
- kL
mass transfer coefficient across the gas/liquid interface
- kL
local kL
-
LT–1
-
LT–1
-
1
longitudinal distance between the start and stop sensors
-
1B
pierced length of the bubble
- t
time
-
t1
length of the square-wave signal at the start sensor
-
t2
length of the square-wave signal at the stop sensor
-
t12
time delay between start and stop signals
- V
volume of the bubbling layer
- VL
volume of the bubble free layer
- VB
bubble volume
- vB
bubble velocity 相似文献
100.