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91.
Du Liping Ding Yuqing Prokop Aleš Tanner Robert D. 《Applied biochemistry and biotechnology》2001,91(1-9):387-404
Bubble size is a key variable for predicting the ability to separate and concentrate proteins in a foam fraction ation process.
It is used to characterize not only the bubble-specific interfacial a rea but also coalescence of bubbles in the foam phase.
This article describes the development of a photoelectric method for measuring the bubble size distribution in both bubble
and foam columns for concentrating proteins. The method uses a vacuum to withdraw a stream of gas-liquid dispersion from the
bubble or foam column through a capillary tube with a funnel-shaped inlet. The resulting sample bubble cylinders are detected,
and their lengths are calculated by using two pairs of infrared photoelectric sensors that are connected with a high-speed
data acquisition system controlled by a microcomputer. The bubble size distributions in the bubble column 12 and 1 cm below
the interface and in the foam phase 1 cm above the interface are obtained in a continuous foam fractionation process for concentrating
ovalbumin. The effects of certain operating conditions such as the feed protein concentration, superficial gas velocity, liquid
flow rate, and solution pH are investigated. The results may prove to be helpful in understanding the mechanisms controlling
the foam fractionation of proteins. 相似文献
92.
Park Don-Hee Witt Andrew R. Tanner Robert D. Roth John A. 《Applied biochemistry and biotechnology》1995,51(1):339-346
Previously collected data describing aerated synthetic waste water, treated in a continuous stirred-tank reactor, are analyzed to understand better the dynamic response to step changes in the dilution rate,D. Comparing a change inD between steady states leads to hysteresis trajectories on both the graph of specific growth rate, μ, vs limiting substrate level (S) and the graph of (S) vs the cell level (X). Qualitative differences between the three different monitored cases will be compared to simulations of simple models at various dilution level changes in order to gain understanding of the dynamics of the process.
相似文献93.
Using a finite-element program, the drag on an unbounded fluid in an (inelastic) power-law fluid is estimated. Comparison with upper and lower bounds, and with experimental data is given. Some remarks on wall effects are also made, and it is shown that wall effects are negligible forn ? 0.5. 相似文献
94.
The reactions of Os3(CO)12 and Os3(CO)10(NCMe)2 with NEt3 have been reinvestigated. Two new products, Os3(CO)10(μ-CH2C(H)?NEt2)(μ-H)) (2) and Os3(CO)10(syn-μ-η1-CHCHNEt2)(μ-H) (3) were obtained in low yields, 4% and 7%, in addition to the previously reported compound Os3(CO)10(anti-μ-η1-CHCHNEt2(μ-H) (1) (20% yield) when the reaction was conducted at 25°C using Os3(CO)10(NCMe)2. Compounds 2 and 3 were characterized by IR, 1H NMR and single-crystal X-ray diffraction analyses. Compound 2 contains a bridging methyl-metallated N-ethylimine ligand formed by the cleavage of one ethyl group from the NEt3. Compound 3 is an isomer of 1 in which the bridging ligand has a syn conformation with respect to the cluster as compared with the anti conformation in 1. Compound 3 slowly isomerizes to 1. Compound 3 is de-carbonylated by exposure to UV radiation and is transformed to the new compound Os3(CO)9(μ3-CC(H)?NEt2)(μ-H)2 (4) (58% yield) by an additional CH activation to form a triply bridging η1-diethylaminovinylidene ligand. Compound 4 isomerizes to the compound Os3(CO)9(μ3-HCCNEt2)(μ-H)2 (5) (70% yield) at 68°C. The latter contains a triply briding ynamine ligand which exhibits structural and reactivity features that are characteristic of a carbene ligand at the amine-substituted carbon atom. Crystal data: for 2, space group = P21/c, a = 9.236(2) Å, b = 12.469(2) Å, c = 18.107(3) Å, β = 104.67(1)°, Z = 4, 2518 reflections, R = 0.031; for 3, space group = P21/m, a = 7.644(1) Å, b = 12.706(2) Å, c = 11.912(2) Å, β = 108.02(1)°, Z = 2, 1295 reflections, R = 0.030; for 4, space group = P21/n, a = 10.233(2) Å, b = 14.834(4) Å, c = 14.538(2) Å, β = 99.88(2)°, Z = 4, 2403 reflections, R = 0.036. 相似文献
95.
96.
97.
98.
Fristrup P Dideriksen BB Tanner D Norrby PO 《Journal of the American Chemical Society》2005,127(39):13672-13679
This paper describes a study of reactivity and enantioselectivity for a series of methyl-substituted styrenes in the Jacobsen-Katsuki (Mn(salen)-catalyzed) epoxidation reaction. Competition experiments provided kinetic data for the reactivity of the seven possible methyl-substituted styrenes (mono-, di- and trisubstituted) relative to styrene itself, ee values were measured by chiral GC, and absolute configurations were secured by chemical correlation. Of particular interest was the switch in absolute configuration at the benzylic position of the epoxides derived from (Z)- and (E)-alpha,beta-dimethylstyrene, respectively. The results could be rationalized in terms of an approach vector with the phenyl substituent proximal to the salen. As opposed to alkyl groups, a proximal phenyl group has very little effect on the rate of the reaction. Consideration of distal vs proximal approach allows prediction of absolute stereochemistry as a function of alkene substitution pattern. Trisubstituted alkenes with one phenyl group cis to the alkene hydrogen can be identified as a favored substrate class in the title reaction, with both rate and selectivity close to the classic (Z)-beta-substituted styrene substrates. 相似文献
99.
Fermentation broth normally contains many extracellular enzymes of industrial interest. To separate such enzymes on-line could
be useful in reducing the cost of recovery as well as in keeping their yield at a maximum level by minimizing enzyme degradation
from broth proteases (either the desired enzymes or the proteases could be removed selectively or both removed together and
then separated). Several large-scale separation methods are candidates for such on-line recovery such as ultrafiltration,
precipitation, and two-phase partitioning. Another promising technique for on-line recovery is adsorptive bubble fractionation,
the subject of this study. Bubble fractionation, like ultrafiltration, does not require contaminating additives and can complement
ultrafiltration by preconcentrating the enzymes using the gases normally present in a fermentation process. A mixture of enzymes
in an aqueous bubble solution can, in principle, be separated by adjusting the pH of that solution to the isoelectric point
(pI) of each enzyme as long as the enzymes have different pIs. The model system investigated here is comprised of three enzyme
separations and the problem is posed as the effect of pectinase (a charged enzyme) on the bubble fractionation of invertase
(a relatively hydrophilic enzyme) from α-amylase (a relatively hydrophobic enzyme).
The primary environmental variable studied, therefore, is the pH in the batch bubble fractionation column. Air was used as
the carrier gas. This prototype mixture exemplifies an aerobic fungal fermentation process for producing enzymes. The enzyme
concentration here is measured as total protein concentration by the Coomassie Blue (Bradford) solution method (1), both as a function of time and column position for each batch run. Since, from a previous study (2), it was found that invertase and α-amylase in a two-enzyme system can be partially separated in favor of one vs the other
at two different pHs (pH 5.0 and 9.0) with significant separation ratios, emphasis is placed on the effect of pectinase at
these pHs. In this study, the addition of pectinase reduced the total separation ratio of the α-amylase-invertase mixture
at both pHs. 相似文献
100.
Tanner PA Zhou X Wong WT Kratzer C Yersin H 《The journal of physical chemistry. B》2005,109(27):13083-13090
The compound Tb[Au(CN)2]3.3H(2)O crystallizes in a layered structure in the hexagonal space group P6(3)/mcm with the 9-coordinate environment of Tb3+ comprising six (CN)- and three OH2 in a tricapped trigonal prism. The shortest Au...Au distance is 3.31 angstroms. The vibrational spectra show that the series Ln[Au(CN)2]3.3H2O (Ln = Y, Pr, Sm, Eu, Tb) are isostructural. The electronic spectra of Eu[Au(CN)2]3.3H2O clearly show that Eu3+ occupies one site of spectroscopic site symmetry D3h, in agreement with the crystallographic data. The electronic emission and absorption spectra of Tb[Au(CN)2]3.3H2O have been recorded at temperatures down to 1.5 K, and the f-f pure electronic transitions are interpreted in detail as arising from the lowest electronic states (in D3h symmetry) (7F6)E' in absorption and (5D4)E' in emission. At low energy, further bands are assigned to the vibronic structure of the CN stretching and water stretching modes, with the latter more predominant. Although the CN stretching vibrations show exclusive infrared or Raman activity in Tb[Au(CN)2]3.3H2O, both of these infrared and Raman active modes are observed in the two-center vibronic transitions. The reasons for this are discussed. 相似文献