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1.
A generalized kinematic viscosity-temperature correlation for undefined liquid heavy petroleum fractions has been developed to represent the data for a wide range of temperature from 100°C to 200°C. The correlation is based on the experimental kinematic viscosity data of true boiling point fractions of four Arabian crude oils. The characterization property required for estimation is 50% boiling point. The proposed correlation fits the experimental data with an overall absolute error of 6.1%. Experimental measurements of kinematic viscosity of heavy true boiling point fractions of Arabian crude oils were also obtained in order to develop the proposed correlation. 相似文献
2.
Two macromodeling techniques using rational bases are investigated to accurately predict the natural frequencies of highly resonant microwave structures. Three methods are proposed and compared to calculate pole‐free solutions to the Thiele continued fraction and vector fitting pole‐residue models of the characteristic equation det[Z(s)]. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. 相似文献
3.
4.
A new, simple and reliable empirical correlation for predicting the viscosities of heavy petroleum fractions is proposed, applicable to fractions with mid-boiling points from 80 to 550°C over a wide range of viscosities (0.4 to 260 mm2 s−1) and measurement temperatures (40 to 200°C). This correlation showed better accuracy in the prediction of heavy petroleum fraction viscosities than that of the most accurate and much more complicated predictive methods in the literature, since it gave an overall average absolute deviation of 6.5% when tested on 296 data for medium and heavy petroleum fractions. 相似文献
5.
The objectives of this research are to identify the membrane fouling potential due to different fractions of NOM and correlate
the physicochemical properties of NOM and membranes with the adsorption of humic substances on membrane and investigate the
mechanism of coagulation affecting UF, and find the optimum conditions of the combined of coagulation with UF membrane filtration
for NOM removal. For Nakdong river water, the humic acid fraction was the most reactive precursor fraction for the formation
of the ratio of THMFP/DOC (STHMFP) and TOXFP/DOC (STOXFP). The result of adsorption kinetics tests showed that hydrophobic
organics adsorbed much more quickly than hydrophilic organics on both membranes. Thus, hydrophobic compounds exhibited a preferential
adsorption onto membrane. In case of the effect of membrane properties on the adsorption of organic fractions, the adsorption
ratio (C1/Ce) was greater for the hydrophobic membrane than for the hydrophilic membrane regardless of the kind of organic fractions.
For combined coagulation with membrane process, flux reduction rate showed lower than the UF process alone. Also, the rate
of flux decline for the hydrophobic membrane was considerably greater than for the hydrophilic membrane. Applying the coagulation
process before membrane filtration showed not only reduced membrane fouling, but also improved removal of dissolved organic
materials that might otherwise not be removed by the membrane. That is, during the mixing period, substantial changes in particle
size distribution occurred under rapid and slow mixing conditions due to the simultaneous formation of microflocs and NOM
precipitates. Therefore, combined pretreatment using coagulation (both rapid mixing and slow mixing) improved not only dissolved
organic removal efficiency but also DBP (Disinfection By-Product) precursor's removal efficiency. 相似文献
6.
A fixed bed is gradually exhausted from top to bottom without backwashing; however, backwashing can rearrange the concentration
gradient in the bed. After backwashing, saturated particles which are located at the top of the bed are homogeneously distributed
in the bed. The used model to predict adsorption and backwashing effect of organic component is the plug flow pore surface
diffusion model (PFPSDM). A sensitivity analysis was performed to determine which parameters have the greatest impact on the
model results for components which can represent various organics. In addition, the effects of backwashing were examined by
rearranging concentration gradient. For single component sensitivity analysis, the molecular weight was an important parameter.
The breakthrough of the smaller molecular weight component was impacted more by backwashing. The SPDFR showed a significant
impact on the breakthrough pattern. When surface diffusion was the dominant mechanism, high SPDFR, the breakthrough profile
was sharper than when pore diffusion was dominant, low SPDFR. The adsorbability was an important parameter in determining
the breakthrough pattern. As expected, the strongly adsorbable component showed the later breakthrough. Backwashing yielded
earlier breakthrough for all single components and multi-components examined. 相似文献
7.
B. R. Singh T. Krogstad Y. S. Shivay B. G. Shivakumar M. Bakkegard 《Nutrient Cycling in Agroecosystems》2005,73(2-3):245-256
Phosphorus (P) enrichment can lead to imbalance in nutrient availability and pollution of terrestrial and aquatic ecosystems. Hence studies were carried out to investigate fractionation and sorption of P in eleven P-enriched soils collected from different agro-climatic sites in Norway. Different P fractions viz. total, organic, inorganic (easily soluble P, Fe-P, Al-P, Ca-P and occluded P), Pw (water extractable), and NH4-lactate extractable P (PAL) at the beginning and after the completion of the experiments varied widely among the soils studied, indicating a wide variability of P supplying capacity of these soils. Soluble P was positively correlated to Ca-P (r = 0.94; P < 0.001), Pw (r = 0.87; P < 0.001), pH (r = 0.79; P < 0.01) and PAL (r = 0.79; P < 0.01), whereas it was negatively correlated with ammonium oxalate-extractable Al (Alox) (r = ?0.68; P < 0.05). Iron-P was only moderately related to Alox(r = 0.64; P < 0.05) and Pox(r = 0.70; P < 0.05), whereas it was not related to any of the other parameters tested. The α [α = Pox/(Feox + Alox)] was highly correlated with PAL (r = 0.93; P < 0.001), pH (r = 0.87; P < 0.001), inorganic P (r = 0.80; P < 0.01) and Pw(r = 0.77; P < 0.01) but moderately to total P (r = 0.71; P < 0.05). Adsorption data fitted well to the Langmuir equation for most soils. The P affinity constant (k), adsorption maximum (b) and thus maximum buffering capacity (mbc) and adsorption isotherm of P were highest in the sandy clay soil from Øsaker, which also contained high amounts of Fe, Al and clay particles and the lowest in sandy soil from Vestrålen, which contained very high initial PALand the lowest content of Fe, Al, silt and clay among all the soils studied. The P affinity constant (k) was correlated positively and significantly to clay content (r = 0.66; P < 0.05), whereas mbc was correlated positively and significantly to clay content (r = 0.63; P < 0.05) and ammonium oxalate-extractable Fe (Feox) (r = 0.63; P < 0.05). Phosphorus desorption of the soils varied widely depending on the initial P status and texture of the soils. Phosphorus desorbed by NH4-lactate was many fold higher as compared to CaCl2 in most soils. 相似文献
8.
Resin adsorption technique with XAD-8 and XAD-4 was used to characterize the raw water from Erlong reservoir in Jilin province of China. The NOM chemical composition sequences of four organic fractions in the raw water,from high to low,are fulvic acid (FA) fraction,hydrophilic non-acid (HPINA) fraction,hydrophilic acid (HPIA) fraction,and humic acid (HA) fraction. Experimental results show that FA is the main precursor of THMFP among the four organic fractions. However,HA or hydrophobic acid exhibits the highest chlorination activity in forming THMs. It is also found that the value of FI/DOC or SUVA and the specific THMFP have better positive correlation. It is implied that certain source water has unique nature of NOM and DBPs. 相似文献
9.
《Journal of Great Lakes research》2020,46(4):976-988
Surface sediments and three sediment cores from the western basin and one sediment core from the Sandusky basin were analyzed to document spatial and temporal changes in five phosphorus fractions and total phosphorus (TP). The areal distributions of the bioavailable fractions NaCl-Pi, NaBD-Pi, and NaOH-Pi and the refractory organic fraction Res-P were broadly consistent and contrasted with those of the detrital fraction HCl-Pi which showed that high concentrations occurred mostly in high-energy littoral zones and low concentrations largely in profundal depositional areas. The contrasting distributions were induced by interactions among tributary inputs, wave action, circulation, and biogeochemical cycling and transfer in the basin. As revealed by the Sandusky basin sediment record, the detrital fraction HCl-Pi was dominant (70% of TP) during European settlement and decreased rapidly by 28.0% in the early 1910s due largely to impoundments of the Maumee and Sandusky Rivers. While HCl-Pi has ever since remained relatively constant, NaCl-Pi, NaBD-Pi, and NaOH-Pi increased significantly between 1950 and 1970 in the two basins. However, the post-regulation sediment records differed considerably among these coring sites. There was a marked increase of TP in two cores, corresponding to recent return of eutrophication and massive harmful algal blooms but contrasting with a relatively constant, low loading into the lake. This signified the role of internal loading as derived partialy from legacy pollution. Furthermore, NaCl-Pi has increased progressively throughout all the records. We conclude that the increased levels of NaCl-Pi in surface sediments may have altered the internal loading and contributed to the resurgences of harmful algal blooms in Lake Erie. 相似文献
10.
David R. Stoutemyer 《Journal of Symbolic Computation》2011,46(7):859-887
This article provides goals for the design and improvement of default computer algebra expression simplification. These goals can also help users recognize and partially circumvent some limitations of their current computer algebra systems. Although motivated by computer algebra, many of the goals are also applicable to manual simplification, indicating what transformations are necessary and sufficient for good simplification when no particular canonical result form is required.After motivating the ten goals, the article then explains how the Altran partially factored form for rational expressions was extended for Derive and for the computer algebra in Texas Instruments products to help fulfill these goals. In contrast to the distributed Altran representation, this recursive partially factored semi-fraction form:
- •
- does not unnecessarily force common denominators,
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- discovers and preserves significantly more factors,
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- can represent general expressions, and
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- can produce an entire spectrum from fully factored over a common denominator through complete multivariate partial fractions, including a dense subset of all intermediate forms.