全文获取类型
收费全文 | 13148篇 |
免费 | 875篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 144篇 |
综合类 | 9篇 |
化学工业 | 3036篇 |
金属工艺 | 474篇 |
机械仪表 | 614篇 |
建筑科学 | 325篇 |
矿业工程 | 16篇 |
能源动力 | 422篇 |
轻工业 | 1274篇 |
水利工程 | 52篇 |
石油天然气 | 43篇 |
武器工业 | 1篇 |
无线电 | 1742篇 |
一般工业技术 | 2581篇 |
冶金工业 | 1791篇 |
原子能技术 | 141篇 |
自动化技术 | 1381篇 |
出版年
2023年 | 98篇 |
2022年 | 173篇 |
2021年 | 293篇 |
2020年 | 216篇 |
2019年 | 277篇 |
2018年 | 314篇 |
2017年 | 359篇 |
2016年 | 427篇 |
2015年 | 365篇 |
2014年 | 538篇 |
2013年 | 867篇 |
2012年 | 712篇 |
2011年 | 887篇 |
2010年 | 641篇 |
2009年 | 603篇 |
2008年 | 616篇 |
2007年 | 503篇 |
2006年 | 414篇 |
2005年 | 376篇 |
2004年 | 375篇 |
2003年 | 350篇 |
2002年 | 311篇 |
2001年 | 259篇 |
2000年 | 251篇 |
1999年 | 273篇 |
1998年 | 542篇 |
1997年 | 395篇 |
1996年 | 265篇 |
1995年 | 203篇 |
1994年 | 210篇 |
1993年 | 200篇 |
1992年 | 146篇 |
1991年 | 120篇 |
1990年 | 124篇 |
1989年 | 117篇 |
1988年 | 85篇 |
1987年 | 71篇 |
1986年 | 71篇 |
1985年 | 99篇 |
1984年 | 91篇 |
1983年 | 59篇 |
1982年 | 52篇 |
1981年 | 61篇 |
1980年 | 60篇 |
1979年 | 57篇 |
1978年 | 46篇 |
1977年 | 58篇 |
1976年 | 92篇 |
1975年 | 58篇 |
1973年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
De Young RJ 《Applied optics》1986,25(21):3850-3854
Beam profile measurements have been made as a function of time within the laser pulse and C2F5I pressure. Measurements indicate that the profile is determined directly by the optical excitation volume, produced by the solar simulator, and that media distortion plays a minor role compared to the build up of quenching species during the lasing pulse. 相似文献
83.
Suk Choo Chung Chang Duck Kong Young Ha Yum 《Journal of Mechanical Science and Technology》1987,1(2):133-139
The dynamic characteristics of the Korean Yi-dynasty bell type structure, including the acoustic effects, are analyzed both theoretically and experimentally. The numerical solutions of natural frequencies and mode shape for membrane and flexural behavior are obtained by using the NASTRAN program for the finite element method with plate shell elements of triangular and quadrilateral types. Test bells, A and B types similar to the Kap-Sa bell in Kong-Ju chosen among typical Korean Yi-dynasty bells, are manufactured on different scales to the original bell. To consider the effects of the variation of the structural dimension on the dynamic response, these bells are analyzed with respect to the variation of the thickness of the wall and the bottom rim and the asymmetric Dang-Jwas. The impact method with the Fast Fourier Transform Analyzer is adopted to experimentally assess the dynamic response. Results are in good agreement with the numerical solutions. 相似文献
84.
James R. Strife John G. Smeggil Wayne L. Worrell 《Journal of the American Ceramic Society》1990,73(4):838-845
The reactions of titanium carbide and hafnium carbide with iridium have been studied in thin film couples fabricated by vapor deposition processes. The reaction product layers after exposure in the temperature range of 1923 to 2400 K are dependent on the stoichiometry of the metal carbide layers and range from simple solid solutions to MIrx compounds. The observed microstructures are predictable from available thermochemical data. The morphology of residual carbon in the reacted metal carbide-iridium product layer varies from interfacial deposits to uniform carbon dispersion and depends upon exposure temperature and metal carbide stoichiometry. 相似文献
85.
An alternative test method to the traditional 180° “T” peel test has been developed for the measurement of interlaminar bonding in three-ply (polyester/aluminium/polypropylene) flexible-packaging, laminate materials. The new test is thought to involve mixed mode I (opening) and mode II (shearing) failure, and takes into account the yielding of the polypropylene layer during testing. The method allows more direct comparisons between materials to be made, and allows the measurement of strong bonds, where a peel test would result in yield or fracture of the substrate arms before debonding. 相似文献
86.
A new method for forming isotropic, laminar, and columnar pyrolytic carbons is proposed. For this, a low RPM (below 2.4 rpm) tumbling bed has been used to deposit pyrolytic carbons from hydrocarbon gases. All deposits were made on graphite substrates from propane and methane at a constant temperature of 1200°C. The microstructures of the pyrolytic carbons deposited were dependent on the flow pattern of the reactant gas, the rpm of the reactor, the hydrocarbon concentration, the nature of the hydrocarbon, and the geometry of the bed. Isotropic pyrolytic carbon is formed under deposition conditions where homogeneous nucleation occurs in the gas phase and at the gas flow conditions where the gas-borne droplets can collide on the substrate. Laminar carbon is formed under deposition conditions where homogeneous nucleation does not occur in the gas phase and at gas flow conditions where the carbon species existing in the bulk of the gas phase can collide on the substrate. Columnar carbon is formed when any carbon products existing in the bulk of the gas phase cannot collide on the substrate. The suggested deposition mechanism can also be applied to pyrolytic carbons deposited in a fluidized bed or in a stationary bed. In particular, isotropic carbon can be obtained even in a stationary bed if the requirements for the deposition of the isotropic carbon described above are satisfied. 相似文献
87.
C. C. Young 《Journal of the American Oil Chemists' Society》1984,61(3):576-581
A new approach to interpret triglyceride data obtained by gas liquid chromatography (GLC) in order to determine cocoa butter
equivalents (CBE) in chocolate is described. The approach is based on the known straight line relationship which exists between
the C50 and C54 triglycerides of cocoa butter of different origins and the realization that, for currently available CBE conforming to CAOBISCO’s
criteria, a similar band relationship exists. The technique described enables the quantity of unspecified CBE in a chocolate
containing an unknown cocoa butter to be determined to an accuracy of ±1.5% when present in chocolate at the 5% level. Nut
oils (almond, walnut or hazelnut) are sometimes present in mainland European chocolates and, should CBE also be present, it
is possible to calculate the combined percentages of nut oil and CBE in the chocolate. The method of interpretation described
is not dependent on a particular GLC technique for determining triglycerides. Interpretation of other laboratories’ results
obtained using different GLC instruments and procedures has shown that the method enables any CBE present in the fat under
examination to be determined accurately. The method compensates for variations in the composition of CBE and for the differences
between cocoa butters of different origin. A detailed knowledge of CBE compositions is not required and only a few cocoa butter/CBE
standards are necessary. The method described is graphical, enabling small laboratories not equipped with microcomputers to
utilize the method. The calculation can, however, be programmed for a computer. 相似文献
88.
Dong Won Cho Young Hae Lee Tae Youn Lee Mitsuo Gen 《Journal of Intelligent Manufacturing》2014,25(5):1025-1042
In this paper we propose an adaptive genetic algorithm that produces good quality solutions to the time dependent inventory routing problem (TDIRP) in which inventory control and time dependent vehicle routing decisions for a set of retailers are made simultaneously over a specific planning horizon. This work is motivated by the effect of dynamic traffic conditions in an urban context and the resulting inventory and transportation costs. We provide a mixed integer programming formulation for TDIRP. Since finding the optimal solutions for TDIRP is a NP-hard problem, an adaptive genetic algorithm is applied. We develop new genetic representation and design suitable crossover and mutation operators for the improvement phase. We use adaptive genetic operator proposed by Yun and Gen (Fuzzy Optim Decis Mak 2(2):161–175, 2003) for the automatic setting of the genetic parameter values. The comparison of results shows the significance of the designed AGA and demonstrates the capability of reaching solutions within 0.5 % of the optimum on sets of test problems. 相似文献
89.
The dependent deformations and evidence of structural changes were measured on pastes of C3S containing CaCl2, and on pastes of C3S or a C3S/C2S blend cured at 65°C. It was concluded that the addition of CaCl2 enhances the role of the “pore component” in controlling irreversible strains even when well-hydrated pastes are dried. The formation of ore stable CSH at 65°C can explain the reduction in time-dependent deformations observed for these pastes. Even though a change in pore size distribution occurs at 65°C, it is not considered to affect irreversible strains in well-hydrated pastes. 相似文献
90.
A MECHANISTICALLY BASED MATHEMATICAL MODEL OF SULFUR DIOXIDE ABSORPTION INTO A CALCIUM HYDROXIDE SLURRY IN A SPRAY DRYER 总被引:3,自引:0,他引:3
George P. Partridge Wayne T. Davis Robert M. Counce Gregory D. Reed 《Chemical Engineering Communications》1990,96(1):97-112
A mathematical model has been developed to predict So2 absorption and removal during the constant rate drying period of a spray dryer. The model, based on film theory, treats the atomized slurry droplets as spheres containing discrete sorbent particles of slaked lime with the fluid uniformly distributed around the individual particles. The model includes gas and liquid phase mass transfer coefficients as well as resistance to Ca(OH)2 dissolution. A sensitivity analysis has been conducted and a comparison was made between pilot-scale experimental data and model-predicted values of S02 removal efficiency. 相似文献