全文获取类型
收费全文 | 2787篇 |
免费 | 110篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 58篇 |
综合类 | 13篇 |
化学工业 | 651篇 |
金属工艺 | 73篇 |
机械仪表 | 124篇 |
建筑科学 | 94篇 |
矿业工程 | 6篇 |
能源动力 | 197篇 |
轻工业 | 180篇 |
水利工程 | 21篇 |
石油天然气 | 15篇 |
无线电 | 231篇 |
一般工业技术 | 596篇 |
冶金工业 | 215篇 |
原子能技术 | 20篇 |
自动化技术 | 420篇 |
出版年
2024年 | 9篇 |
2023年 | 33篇 |
2022年 | 76篇 |
2021年 | 102篇 |
2020年 | 86篇 |
2019年 | 78篇 |
2018年 | 126篇 |
2017年 | 89篇 |
2016年 | 99篇 |
2015年 | 74篇 |
2014年 | 106篇 |
2013年 | 216篇 |
2012年 | 110篇 |
2011年 | 170篇 |
2010年 | 134篇 |
2009年 | 127篇 |
2008年 | 132篇 |
2007年 | 122篇 |
2006年 | 90篇 |
2005年 | 82篇 |
2004年 | 62篇 |
2003年 | 64篇 |
2002年 | 42篇 |
2001年 | 32篇 |
2000年 | 27篇 |
1999年 | 43篇 |
1998年 | 59篇 |
1997年 | 40篇 |
1996年 | 39篇 |
1995年 | 40篇 |
1994年 | 37篇 |
1993年 | 27篇 |
1992年 | 23篇 |
1991年 | 25篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 22篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 16篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1973年 | 5篇 |
排序方式: 共有2914条查询结果,搜索用时 15 毫秒
1.
A Rate-Control vaginal device was developed which overcomes the low bioavailability and unpredictable Q - t1/2 type release and absorption rate profiles of flurogestone acetate delivered by the currently marketed Syncro-Mate pessary.
The in vitro release and vaginal absorption profiles from the Rate-Control vaginal device were run simultaneously, a linear Q - t relationship was obtained with a significant improvement in bioavailability. A mathematical model was developed to correlate the in vitro drug release and the vaginal absorption profiles of flurogestone acetate from the vaginal devices.
The design, development and the simultaneous release and absorption profiles of flurogestone acetate from this new vaginal device were outlined and discussed. 相似文献
The in vitro release and vaginal absorption profiles from the Rate-Control vaginal device were run simultaneously, a linear Q - t relationship was obtained with a significant improvement in bioavailability. A mathematical model was developed to correlate the in vitro drug release and the vaginal absorption profiles of flurogestone acetate from the vaginal devices.
The design, development and the simultaneous release and absorption profiles of flurogestone acetate from this new vaginal device were outlined and discussed. 相似文献
2.
Masood Parang Rao V. Arimilli Satish P. Ketkar 《International Communications in Heat and Mass Transfer》1985,12(2):179-189
A special boundary integral method developed for two-dimensional regions containing circular holes is used to calculate temperature and heat transfer on the boundaries of several selected regions. The geometrical configuration of the region is arbitrary and convective boundary conditions are assumed. An important feature of the method is analytic representation of temperature and its normal derivative on the interior circular holes in the form of a harmonic series. This makes the application of the boundary integral method convenient and free from conditioning problems associated with small interior boundaries. Heat transfer from circular isothermal interior holes are calculated for several illustrative examples using three terms of the harmonic series representation for heat transfer at each of the circular boundaries. The results are presented and discussed. 相似文献
3.
As the wave of globalization washes over geographical boundaries, the world steps into the era of a new knowledge-based economy with governments striving to encourage innovation in industry especially through national systems of innovation. A national system of innovation (NSI) is considered important because how a nation utilizes and exploits its NSI will determine whether it can compete and ride the wave of globalization or be carried by it and thrashed onto the shores of the new economy. This paper seeks to highlight the linkages developed for enabling communication among the various NSI stakeholders for achieving goals in one such effort, viz. the Multimedia Super Corridor (MSC) Cluster of Malaysia. The MSC offers a vision to create a global multimedia climate through an integrated environment of interlinked elements and attributes. The government of Malaysia, realising the significance of the NSI as a way to better utilize, exploit, and enhance systems, is making efforts to this effect. The efforts include bringing together various stakeholder organizations under the "Multimedia Flagship Applications" to develop flagship applications. This is for the development of information technology applications to pave the way toward a knowledge-based economy. The MSC Cluster is presented here as a physical manifestation of the NSI, and it gives an idea as to how policy makers can design linkages for communication among the various stakeholders to further national innovative performance and competitiveness in general. 相似文献
4.
Sodium‐ion conducting polymer electrolytes based on poly(vinyl alcohol) complexed with sodium bromide were prepared with a solution‐casting technique. The structure of these films was determined with X‐ray diffraction, and the complexation of the salt with the polymer was confirmed with Fourier transform infrared spectroscopy studies. Electrical conductivity was measured with an alternating‐current impedance analyzer in the frequency range of 100 Hz to 1 MHz and in the temperature range of 303–373 K. It was observed that the magnitude of conductivity increased with the increase in the salt concentration as well as the temperature. The nature of the charge transport in these polymer electrolyte films was determined with both Wagner's polarization technique and the Watanabe technique. The dominant conducting species were found to be ions, particularly anions. Optical absorption studies were performed in the wavelength range of 200–600 nm, and the absorption edge, direct band gap, and indirect band gap values were evaluated. Electrochemical cells were fabricated, and their discharge characteristics were studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
5.
In this work, we provide the evidence of polymer transcrystallinity in the presence of carbon nanotubes (CNTs). The interfacial morphology of carbon nanotube fiber-polypropylene matrix is investigated by means of polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The supramolecular microstructures of polypropylene transcrystals induced by the nanotube fiber are observed in the range of isothermal crystallization temperatures from 118 °C to 132 °C. The dynamic process of transcrystallization is analyzed by using the theory of heterogeneous nucleation. Microstructure analysis shows that the nanotubes can nucleate the growth of both α- and γ-transcrystal, and α-transcrystals dominate the overall interfacial morphology. Close to the nanotube fiber surface, a cross-hatched lamellar microstructure composed of mother lamellae and daughter lamellae is observed. 相似文献
6.
Educational research over the past three years has intensified such that the context of learning resources needs to be properly modeled. Many researchers have described and even mandated the use of ontologies in the research being conducted, yet the process of actually connecting one or more ontologies to a learning object has not been extensively discussed. This paper describes a practical model for associating multiple ontologies with learning objects while making full use of the IEEE LOM specification. The model categorizes these ontologies according to five major categories of context based on the most popular fields of study actively being pursued by the educational research community: Thematic context, Pedagogical context, Learner context, Organizational context, and Historical/Statistical context. 相似文献
7.
Large internal strains and stresses can be produced by low temperature implantation over small distances from the free surface in a thick substrate. These are typically non-uniform and have large composition gradients. In dilute bcc solutions, containing unclustered interstitial implants, the residual macroscopic strains may be treated as isotropic. The calculation of residual strain (or stress) is based upon anisotropic elasticity theory and internal stress is given in terms of the dipole tensor for individual defects in single crystal films. In a completely elastic zone, forces act to maintain a rigid outside surface and cause the strain distribution to be zero along directions parallel to the free surface. This produces a strain magnification along the perpendicular direction from Poisson contractions. If the implanted zone is completely relaxed by plastic deformation, the strains are described by the free expansion strains due to both implants and lattice damage. There is no angular dependence of the free expansion strain in this extreme condition. One can determine whether a zone is completely elastic, completely relaxed by plastic deformation, or in some intermediate state from plots of strain against sin2, where is the angle of tilt relative to the surface normal. These results may be obtained from X-ray Bragg intensity data by measuring shifts and line broadening from (hkl) planes at different tilt angles. Theoretical results are given for both single crystal and polycrystalline materials in terms of residual strain and stress. 相似文献
8.
Poornachandran R. Mohan Kumar N. Saravana Kumar R. Baskaran S. 《Microsystem Technologies》2021,27(11):4101-4109
Microsystem Technologies - The quantitative analysis of microwave noise available in the double gate (DG) high electron transistors of mobility (HEMT) is reported in this paper. For this analysis,... 相似文献
9.
T. Chandrasekhara Rao G. Lakshminarayana N. B. L. Prasad S. Jagan Mohan Rao G. Azeemoddin D. Atchyuta Ramayya S. D. Thirumala Rao 《Journal of the American Oil Chemists' Society》1984,61(9):1472-1473
The seeds and extracted oils ofCarissa spinarum (Apocynaceae), (I),Leucaena leucocephala (Leguminosae) (II) andPhysalis minima (Solanaceae) (III) were analyzed for characteristics and compositions. The seeds of I, II and III contained 22.4, 6.4 and
40.0% oil and 10.1, 27.6 and 17.9% protein, respectively. The oils of I, II and III had, respectively, iodine values 70.1,
113.5 and 122.5; saponification values 186, 188 and 189; unsaponifiable matter 5.2, 2.5 and 0.8%, and the following fatty
acid compositions (area %): palmitic 12.6, 14.2, 10.5; stearic 7.6, 6.1, 8.6; oleic 72.7, 20.1, 17.3; linoleic 5.2, 53.8,
61.4; linolenic 0.9, 1.8, 0.0, and arachidic 1.0, 2.3, 0.0. II contained 1.7% lignoceric acid. III contained small amounts
of hexadecenoic (0.1%), epoxy (0.6%) and hydroxy (1.5%) fatty acids. 相似文献
10.
Design of Barrages with Genetic Algorithm Based Embedded Simulation Optimization Approach 总被引:2,自引:2,他引:0
Raj Mohan Singh 《Water Resources Management》2011,25(2):409-429
Barrages are hydraulic structures constructed across rivers to divert flow into irrigation canals or power generation channels.
The most of these structures are founded on permeable foundation. The optimum cost of these structures is nonlinear function
of factors that cause the seepage forces under the structure. There is, however, no procedure to ascertain the basic barrage
parameters such as depth of sheet piles or cutoffs and the length and thickness of floor in a cost–effective manner. In this
paper, a nonlinear optimization formulation (NLOF), which consists of an objective function of minimizing total cost, is solved
using genetic algorithm (GA). The mathematical model that represents the subsurface flow is embedded in the NLOF. The applicability
of the approach has been illustrated with a typical example of barrage profile. The results obtained in this study shows drastic
cost savings when the proposed NLOF is solved using GA than that of using classical optimization technique and conventional
method. A parametric analysis has also been performed to study the effect of varying soil and hydrological conditions on design
parameters and on over all cost. 相似文献