全文获取类型
收费全文 | 618篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 5篇 |
综合类 | 5篇 |
化学工业 | 191篇 |
金属工艺 | 8篇 |
机械仪表 | 7篇 |
建筑科学 | 8篇 |
能源动力 | 24篇 |
轻工业 | 43篇 |
水利工程 | 2篇 |
石油天然气 | 7篇 |
无线电 | 61篇 |
一般工业技术 | 136篇 |
冶金工业 | 57篇 |
原子能技术 | 6篇 |
自动化技术 | 79篇 |
出版年
2024年 | 2篇 |
2023年 | 16篇 |
2022年 | 36篇 |
2021年 | 28篇 |
2020年 | 35篇 |
2019年 | 26篇 |
2018年 | 38篇 |
2017年 | 25篇 |
2016年 | 18篇 |
2015年 | 7篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 26篇 |
2011年 | 37篇 |
2010年 | 20篇 |
2009年 | 30篇 |
2008年 | 23篇 |
2007年 | 18篇 |
2006年 | 7篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有639条查询结果,搜索用时 15 毫秒
91.
The polymer systems of vinyl latex, epoxy latex/resin, and phenol formaldehyde were used to modify sand-cement mortar at room temperature. The compressive strength increased with an increase of the latex/resin concentration, with the addition of CaCl2 or CaCO3, and with the addition of superplasticizer. Tensile and flexural strengths also increased with polymer incorporation. The porosity of the modified mortar decreased with the addition of resin. The percentage of water absorption and acid solubility were found to decrease for the latex/resin modified samples. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1251–1257, 1997 相似文献
92.
The biodegradability of low density polyethylene (LDPE)/starch and LDPE/starch/starch acetate (STAc) blends was tested and observed to be dependent on STAc content. The binary and ternary blends containing up to a maximum concentration of 30% starch were examined for their thermal, mechanical, and morphological properties. The blends with no STAc or 2.5% STAc show almost no adherence of two phases. With 10% STAc, dispersion of starch was observed to increase with some adherence to LDPE. Tensile strength, elongation at break, and Izod impact strength of the blends decreased with increased starch content. However, incorporation of STAc along with starch improved all these properties, particularly elongation at break and toughness. The melt flow index was also improved on partial substitution of starch by STAc. Maximum biodegradability was observed for the blends containing 30% (starch + STAc). Cell growth was observed to increase with increasing concentration of (starch + STAc) in the blends. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2791–2802, 1999 相似文献
93.
S. R. Koteswara Rao B. Kamsala Devi K. Sreenivasa Rao K. Prasad Rao 《The International Journal of Advanced Manufacturing Technology》2009,45(1-2):16-24
High-strength heat-treatable aluminum alloy AA2219 finds application in aerospace industries. Though it has good weldability, with alternating current–tungsten inert gas welding, the joint efficiency obtained is only 40%, particularly in thicker plates. In the present study, an attempt has been made to improve the weld metal properties by modifying the chemistry of fusion zone and post-weld thermo-mechanical treatments. Fillers were made through casting route by melting conventional 2319 filler with Sc and Mg. Two levels of Sc (0.3% and 0.6%) and four levels of Mg (0.3% to 0.6%) were varied. Compressive deformation was done on the fusion zone of the weld to get three levels of percentage of reduction (4%, 8%, and 12%). As welded specimens and welds after compressive deformation, those were subjected to post-weld aging treatments at 190ºC for different periods up to 100 h. Compressive deformation on the welds made with modified filler of 2319 with Sc and Mg resulted in significant improvement in the weld metal strength. 相似文献
94.
Stability of the kinetic Alfven wave in a plasma of hydrogen, oxygen and electrons is studied. Each species is modeled by drifting ring distributions in the direction parallel to the magnetic field, while in the perpendicular direction the distribution is simulated with a loss cone type distribution obtained through the subtraction of two Maxwellian distributions with different temperatures. It is found that for frequency w* < WHwith w* andWH the Doppler shifted and hydrogen ion gyro-frequencies, respectively, the growth rate of the kinetic Alfven wave increases with the increase in propagation angles and density of oxygen ions. On the other hand, for frequencies w* < WOwithWOthe oxygen ion gyro-frequency the growth rate is independent of the oxygen ion density. 相似文献
95.
96.
Sunil Shah Angshuman Pal Tushar Rajyaguru R. S. R. Murthy Surekha Devi 《应用聚合物科学杂志》2008,107(5):3221-3229
A series of copolymeric nanoparticles of the partially water‐soluble monomer ethyl methacrylate and the water‐soluble monomer 2‐hydroxyl ethyl methacrylate were synthesized from emulsions containing sodium dodecyl sulfate via free‐radical polymerization. Lamotrigine, as a model drug, was loaded in nanoparticles during in situ polymerization. A stable and transparent poly(ethyl methacrylate‐co‐hydroxyl ethyl methacrylate) nanolatex was produced for all compositions and characterized for particle size by dynamic light scattering and transmission electron microscopy. Particles were found to be smaller than 50 nm in size. Structural characterization of copolymers was done by infrared spectrometry, gel permeation chromatography, and NMR spectroscopy. Drug encapsulation efficiency was determined by ultraviolet (UV)–visible spectrometry and was found to be 26–62% for copolymers with different compositions. UV data suggest molecular‐level dispersion of the drug in the nanoparticles. In vitro drug‐release studies showed the controlled release of lamotrigine. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
97.
Pyrrole was polymerized in the presence of anhydrous ferric chloride as oxidant and p‐toluene sulfonic acid as dopant. Polypyrrole‐coated short nylon fibers were prepared by polymerizing pyrrole in the presence of short nylon fibers. The resultant polypyrrole (PPy) and PPy‐coated nylon fiber (F‐PPy) were then used to prepare rubber composites based on acrylonitrile butadiene rubber (NBR). The cure pattern, direct current (DC) conductivity, mechanical properties, morphology, thermal degradation parameters, and microwave characteristics of the resulting composites were studied. PPy retarded the cure reaction while F‐PPy accelerated the cure reaction. Compared to PPy, F‐PPy was found to be more effective in enhancing the DC conductivity of NBR. The tensile strength and modulus values increased on adding PPy and F‐PPy to NBR, suggesting a reinforcement effect. Incorporation of PPy and F‐PPy improved the thermal stability of NBR. The absolute value of the dielectric permittivity, alternating current (AC) conductivity, and absorption coefficient of the conducting composites prepared were found to be much greater than the gum vulcanizate. PPy and F‐PPy were found to decrease the dielectric heating coefficient and skin depth significantly. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
98.
For a wide class of stochastic processes including processes belonging to the curved exponential families, it is proved that Wald SPRT is optimal in the sense of minimizing the expectations of increasing processes associated with the stochastic process. The increasing processes are given by the Doob-Meyer decompositions of the log-probability ratio under the two hypotheses. 相似文献
99.
100.
Chemical modification of pinewood was carried out by impregnating the wood with styrene as the impregnating monomer and in combination with a crosslinking monomer glycidyl methacrylate (GMA). Polymerization was carried out by catalyst heat treatment. Dimensional stability in terms of antiswell efficiency was determined and improved on treatment with polymer. Water uptake percentage was also improved for styrene‐GMA treated wood samples over styrene treated or untreated wood samples. Mechanical properties such as bending strength measured in terms of modulus of elasticity and modulus of rupture of polymer‐treated samples showed an improvement over untreated ones. Treatment also resulted an improvement in compressive strengths. Thermal properties of the wood samples were evaluated by thermogravimetric analyzer and differential scanning calorimeter. Biodegradability of the treated and untreated wood samples was determined and improvement was obtained on treatment. As a whole, styrene‐GMA treated wood samples showed more improvement over untreated or styrene‐treated samples. POLYM. COMPOS., 28:1–5, 2007. © 2007 Society of Plastics Engineers 相似文献