全文获取类型
收费全文 | 21187篇 |
免费 | 1904篇 |
国内免费 | 964篇 |
专业分类
电工技术 | 796篇 |
综合类 | 2934篇 |
化学工业 | 4519篇 |
金属工艺 | 2345篇 |
机械仪表 | 872篇 |
建筑科学 | 1320篇 |
矿业工程 | 652篇 |
能源动力 | 751篇 |
轻工业 | 995篇 |
水利工程 | 397篇 |
石油天然气 | 879篇 |
武器工业 | 118篇 |
无线电 | 1131篇 |
一般工业技术 | 2927篇 |
冶金工业 | 1360篇 |
原子能技术 | 244篇 |
自动化技术 | 1815篇 |
出版年
2025年 | 117篇 |
2024年 | 356篇 |
2023年 | 342篇 |
2022年 | 412篇 |
2021年 | 597篇 |
2020年 | 636篇 |
2019年 | 636篇 |
2018年 | 543篇 |
2017年 | 666篇 |
2016年 | 705篇 |
2015年 | 718篇 |
2014年 | 1080篇 |
2013年 | 1272篇 |
2012年 | 1461篇 |
2011年 | 1470篇 |
2010年 | 1073篇 |
2009年 | 1141篇 |
2008年 | 1053篇 |
2007年 | 1252篇 |
2006年 | 1211篇 |
2005年 | 1059篇 |
2004年 | 933篇 |
2003年 | 832篇 |
2002年 | 703篇 |
2001年 | 554篇 |
2000年 | 499篇 |
1999年 | 436篇 |
1998年 | 330篇 |
1997年 | 314篇 |
1996年 | 270篇 |
1995年 | 254篇 |
1994年 | 246篇 |
1993年 | 169篇 |
1992年 | 150篇 |
1991年 | 136篇 |
1990年 | 109篇 |
1989年 | 87篇 |
1988年 | 66篇 |
1987年 | 39篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1976年 | 2篇 |
1959年 | 2篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The viscometric, turbidimetric and potentiometric properties of copolymers of acrylamide (AM) with 2-acrylamido-2-methylpropanedimethylammonium chloride (AMPDAC) were studied in aqueous solutions. The AMPDAC polymers exhibit poor salt tolerance and large, negative viscosity/temperature coefficients. Furthermore, the polymers were found to be sensitive to changes in pH. The AMPDAC polymers undergo phase separation in the presence of dianions as a function of temperature and AMPDAC composition. 相似文献
2.
《Drying Technology》2007,25(5):831-839
Residence time distributions for an aqueous solution of 10% sodium chloride in a spouted bed dryer of inert particles were determined using the stimulus-response technique. Glass and polyethylene beads with diameters 2.6 and 3.4 mm were used as inert bodies in a cylindrical column of 14.0 cm diameter and 60° conical base. The effects of inert bodies load, air, and paste flow rates on the mean residence times and RTD were determined following 23 factorial designs. The RTD could be correlated to the perfect mixing cell model with R2 varying from 0.8684 to 0.9815. The mean residence times in CSBD varied from 10.8 to 13.9 and 10.7 to 13.3 min for glass and polyethylene beads, respectively. For both inert particles, mean residence times increased with bed height and decreased with paste feed rates. Also, terms of interaction among the factors were significant in some cases, showing a complex behavior of paste residence times. Equations obtained by response surface regression could predict mean residence times on glass and polyethylene beads with deviations lower than ±10%. 相似文献
3.
To confirm the reliability of the theory of phase equibria of multicomponent polymer 1/multicomponent polymer 2 systems (i.e. quasi-binary systems) and the method of computer experiment based on this theory (Brit. Polym. J., 23 (1990)285; 23 (1990)299; Polym. Int., 29 (1992)219), could point curves (CPC), two-phase volume ratios ( R ) and critical solution points (CSP) have been determined experimentally for the quasi-binary mixtures of poly(ethylene oxide) (M¯w = 647, M¯w/M¯n = 1.15; M¯w and M¯n, the weight-average and numberaverage molecular weights, respectively) and poly(propylene oxide) (M¯w = 2028, M¯w/M¯n = 1.08; and Mw = 2987, Mw/Mn = 1.13). The hydroxyl end groups of both polymers were methoxylated in advance by the Cooper & Booth method (Polymer, 18 (1977)164). The thermodynamic interaction parameter between both polymers, χ12, and the concentration dependence parameters for the above quasi-binary systems were determined by the method proposed in a previous paper (Brit. Polym. J., 23 (1990)299). CPC, R and CSP values calculated on the basis of the theory are in good agreement with the values determined experimentally. 相似文献
4.
Edwin P. D. Pednault 《Computational Intelligence》1988,4(3):356-372
This paper presents a method of solving planning problems that involve actions whose effects change according to the situations in which they are performed. The approach is an extension of the conventional planning methodology in which plans are constructed through an iterative process of scanning for goals that are not yet satisfied, inserting actions to achieve them, and introducing subgoals to these actions. This methodology was originally developed under the assumption that one would be dealing exclusively with actions that produce the same effects in every situation. The extension involves introducing additional subgoals to actions above and beyond the preconditions of execution normally introduced. These additional subgoals, called secondary preconditions, ensure that the actions are performed in contexts conducive to producing the effects we desire. This paper defines and analyzes secondary preconditions from a mathematically rigorous standpoint and demonstrates how they can be derived from regression operators. 相似文献
5.
Cheng-Liang Chang Hsuan Chang Yuan-Cheng Chang 《Journal of the Chinese Institute of Chemical Engineers》2007
A hybrid mathematic model for pervaporation is proposed which incorporates the concepts of solution-diffusion model and pore model. The model allows performance prediction as well as the establishment of the internal concentration and pressure profiles within the membrane. The model parameters specific to the particular membrane and mixture system are determined using liquid sorption and pervaporation experimental data. The model is experimentally examined using ethanol–water mixtures and poly(dimethyl siloxane)–poly(vinyldiene fluoride) (PDMS–PVDF) composite membranes. The characteristics of flux and separation factor predicted using the model are in fair agreement with the experimental data under various feed concentrations and downstream pressures for different membrane arrangements, including single-layer, reverse single-layer and double-layer PDMS–PVDF composite membranes. Internal profiles of pressure, concentration and component mole fraction can be established using the model. Concentration polarization phenomena for ethanol and water are located at membrane interfaces and vapor–liquid interfaces, respectively. Performances of several different membrane designs are compared using the model. 相似文献
6.
Influence of the composition of the binder and the carbonation on the zeta potential values of hardened cementitious materials 总被引:1,自引:0,他引:1
Electroosmotic experiments have been carried out on eight different mixes of hardened cementitious matrixes including concrete, mortar and pastes, different types of binders, carbonated and non-carbonated specimens and different test conditions. From these trials, the zeta potential values have been determined and the optimum experimental parameters and devices have been established. In addition, the influence of the composition of the binder on the zeta potential has been quantified indicating that higher amounts of Al2O3 in the binder lead to higher positive values of zeta potential, while the SiO2 acts just on the opposite side. This has been explained in terms of the different i.e.p. (isoelectric point) for both oxides. Concerning the influence of carbonation, it increases the absolute value of the zeta potential toward more negative values; this behaviour has been attributed to the influence of the specifically adsorbed Ca2+ in the negative sites of the surface in the non-carbonated samples. 相似文献
7.
8.
ZHANG YuJun ZHANG WeiQing & YANG ChaoShuai State Key Laboratory of Geomechanics Geotechnical Engineering 《中国科学:信息科学(英文版)》2011,(7)
With the models of stress corrosion and pressure solution, by Yasuhara et al., two computation conditions were designed for a hypothetical nuclear waste repository in an unsaturated dual-porosity rock mass: (i) the fracture apertures are changed with the stress corrosion and pressure solution (the porosity of rock matrix is also a function of stress); (ii) the fracture apertures and the porosity of rock matrix are constants. Then the corresponding two-dimensional FEM analyses for the coupled thermohydro-mec... 相似文献
9.
In this paper, we consider the following nonlinear fractional three-point boundary value problem
10.
Summary In this paper, we investigate the discretization of an elliptic boundary value problem in 3D by means of the hp-version of the finite element method using a mesh of tetrahedrons. We present several bases based on integrated Jacobi polynomials
in which the element stiffness matrix has nonzero entries, where p denotes the polynomial degree. The proof of the sparsity requires the assistance of computer algebra software. Several numerical
experiments show the efficiency of the proposed bases for higher polynomial degrees p.
相似文献