全文获取类型
收费全文 | 2198篇 |
免费 | 64篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 27篇 |
综合类 | 2篇 |
化学工业 | 572篇 |
金属工艺 | 46篇 |
机械仪表 | 33篇 |
建筑科学 | 81篇 |
矿业工程 | 1篇 |
能源动力 | 77篇 |
轻工业 | 251篇 |
水利工程 | 7篇 |
石油天然气 | 6篇 |
无线电 | 240篇 |
一般工业技术 | 420篇 |
冶金工业 | 49篇 |
原子能技术 | 36篇 |
自动化技术 | 418篇 |
出版年
2024年 | 27篇 |
2023年 | 26篇 |
2022年 | 49篇 |
2021年 | 68篇 |
2020年 | 62篇 |
2019年 | 62篇 |
2018年 | 63篇 |
2017年 | 72篇 |
2016年 | 73篇 |
2015年 | 79篇 |
2014年 | 105篇 |
2013年 | 160篇 |
2012年 | 139篇 |
2011年 | 223篇 |
2010年 | 146篇 |
2009年 | 137篇 |
2008年 | 129篇 |
2007年 | 88篇 |
2006年 | 92篇 |
2005年 | 79篇 |
2004年 | 59篇 |
2003年 | 65篇 |
2002年 | 48篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 31篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 23篇 |
1995年 | 6篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有2266条查询结果,搜索用时 0 毫秒
991.
Mid infrared spectroscopy (MIR) combined with multivariate data analysis was used to discriminate between ewes milk samples according to their feeding systems (controls, ewes fed scotch bean and ewes fed soybean). The MIR spectra were scanned throughout the first 11 weeks of the lactation stage. When factorial discriminant analysis (FDA) with leave one-out cross-validation was applied, separately, to the three spectral regions in the MIR (i.e. 3000–2800, 1700–1500 and 1500–900 cm−1), the classification rate was not satisfactory. Therefore, the first principal component (PCs) scores (corresponding to 3, 10 and 10 for, respectively, the 3000–2800, 1700–1500 and 1500–900 cm−1) of the principal component analysis (PCA) extracted from each of the data sets were pooled (concatenated) into a single matrix and analysed by FDA. Correct classification amounting to 71.7% was obtained. Finally, the same procedure was applied to the MIR and fluorescence data sets and 98% of milk samples were found to be correctly classified. Milk samples belonging to control and soybean groups were 100% correctly classified. Regarding milk samples originating from the scotch bean group, only 2 out of 33 samples were misclassified. It was concluded that concatenation of the data sets collected from the two spectroscopic techniques is an efficient tool for authenticating milk samples according to their feeding systems, regardless of the lactation stage. 相似文献
992.
In this paper, the effects of viscoelastic characteristics on the creep crack growth initiation are studied by developing a new path-independent integral Gθv which allows us to compute the energy release rate with the finite element method. The originality of this approach is the perfect uncoupling between the viscous dissipation and the free energy which drives the crack propagation and the crack growth initiation. Coupled with an explicit finite element formulation of the linear viscoelastic behavior, this integral allows us to simulate accurate crack growth initiation. 相似文献
993.
Masselon C Pasa-Tolić L Tolić N Anderson GA Bogdanov B Vilkov AN Shen Y Zhao R Qian WJ Lipton MS Camp DG Smith RD 《Analytical chemistry》2005,77(2):400-406
In proteomics, effective methods are needed for identifying the relatively limited subset of proteins displaying significant changes in abundance between two samples. One way to accomplish this task is to target for identification by MS/MS only the "interesting" proteins based on the abundance ratio of isotopically labeled pairs of peptides. We have developed the software and hardware tools for online LC-FTICR MS/MS studies in which a set of initially unidentified peptides from a proteome analysis can be selected for identification based on their distinctive changes in abundance following a "perturbation". We report here the validation of this method using a mixture of standard proteins combined in different ratios after isotopic labeling. We also demonstrate the application of this method to the identification of Shewanella oneidensis peptides/proteins exhibiting differential abundance in suboxic versus aerobic cell cultures. 相似文献
994.
995.
We apply robust control techniques to an adaptive optics system including a dynamic model of the deformable mirror. The dynamic model of the mirror is a modification of the usual plate equation. We propose also a state-space approach to model the turbulent phase. A continuous time control of our model is suggested, taking into account the frequential behavior of the turbulent phase. An H(infinity) controller is designed in an infinite-dimensional setting. Because of the multivariable nature of the control problem involved in adaptive optics systems, a significant improvement is obtained with respect to traditional single input-single output methods. 相似文献
996.
This article introducesActif the French its framework architecture : – for readers already in the its domain, it will give a global and prospective view on this project and light on the “stakeholders” role with respect to ITS deployment ; – for the newcomers, it shall introduce the issues of interoperability and information exchange between systems, and help understand how theActif approach may be similar to the systems engineering approach they are familiar with in their domain. 相似文献
997.
Estimation of parasitic capacitances in a MOSFET device is very important, notably in mixed circuit simulation. For deep-submicron LDD MOSFETs, the extrinsic capacitance (overlap plus fringing capacitances) is a growing fraction of the total gate capacitance. A correct estimation of the extrinsic capacitance requires an accurate modeling of each of its constituents. However the major existing models do not correctly predict the overlap capacitance and the inner fringing capacitance (which is often ignored). In this paper a new approach to model the overlap Cov and fringing Cif+Cof capacitances in the zero-current regime is presented. The bias dependence of the extrinsic capacitance is investigated and a detailed study of the influence of the LDD doping dose is also undertaken. Then, an efficient, simple and continuous model describing the evolution of overlap and fringing capacitances in all operating regimes of a n-channel LDD MOSFET is developed. Finally this model is incorporated in an existing compact-model for circuit simulation. It is shown that this new model leads to excellent results in comparison with full 2D numerical device simulation. 相似文献
998.
Junhua Ji Christophe A. Codemard Jayanta K. Sahu Johan Nilsson 《Optical Fiber Technology》2010,16(6):428-441
In this paper, we present basic design rules for double-clad fibers that enable efficient 1st-Stokes operation of cladding-pumped fiber Raman devices. Limiting factors that we treat include unwanted 2nd-Stokes generation, material damage in the core, pump pulse dispersion, inner-cladding NA, background loss, pulse shape and pump noise. With a well-designed fiber, we calculate that a pump-to-signal brightness enhancement of over 2000 is possible, with certain pump parameters. On experimental work, we report a 100 W cladding-pumped fiber Raman laser at 1120 nm. Furthermore, a double-clad Raman fiber with large-mode area, ~40 μm core diameter, pumped by a Q-switched Nd:YAG laser is used to generate Stokes pulses with 1 mJ energy. 相似文献
999.
Haifaa Mokbel Cyril Poriel Joëlle Rault‐Berthelot Frédéric Dumur Didier Gigmes Joumana Toufaily Tayssir Hamieh Daniela Cordella Christophe Detrembleur Jacques Lalevée 《应用聚合物科学杂志》2016,133(12)
A novel photoinitiator based on a spiroxanthene scaffold in the presence of an iodonium salt is proposed for the cationic ring‐opening polymerization of a diepoxide, as well as for the free‐radical polymerization of an acrylate upon violet LED exposure (385 and 405 nm). Good‐to‐excellent rates of polymerization and final conversions are obtained. These systems are characterized by a higher reactivity compared with that of anthracene/iodonium salt used as reference for cationic near UV polymerization. The addition of a poly(ionic liquid) improves the cationic polymerization profiles. The photochemical mechanisms are studied by steady‐state photolysis, fluorescence, and electron spin resonance spin‐trapping techniques. Molecular orbital calculations give an insight into the light absorption properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43213. 相似文献
1000.
Narimane Mati‐Baouche Hélène De Baynast Christophe Vial Fabrice Audonnet Shengnan Sun Emmanuel Petit Fabienne Pennec Vanessa Prevot Philippe Michaud 《应用聚合物科学杂志》2015,132(2)
This study was conducted on the both solid and solubilized chitosans to propose an approach for the physico‐chemical, thermal and mechanical characterizations of this polysaccharide. The polysaccharide used was a 90% deacetylated chitosan having a molecular weight of 98.4 kDa. The flow property of chitosan solutions was evaluated revealing a shear‐thinning behavior. The thermal characterization was carried out by studying heat specific capacity, glass transition temperature, and thermal conductivity on chitosan dried specimens (solid state). Their Tg were measured by DSC and confirmed by DMA at 102 and 122°C depending on concentrations of initial chitosan solutions. The mechanical characterization was conducted by analyzing Young modulus, tensile strength, and elongation at break of chitosan specimens. They exhibited a higher elongation at break and a lower tensile strength when made from high concentrated chitosan solution (9% w/v). Differences in mechanical behavior of specimens were explained by differences of crystallinity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41257. 相似文献