全文获取类型
收费全文 | 108941篇 |
免费 | 10151篇 |
国内免费 | 5751篇 |
专业分类
电工技术 | 6343篇 |
技术理论 | 7篇 |
综合类 | 7940篇 |
化学工业 | 17814篇 |
金属工艺 | 6586篇 |
机械仪表 | 6947篇 |
建筑科学 | 8045篇 |
矿业工程 | 3428篇 |
能源动力 | 3078篇 |
轻工业 | 8751篇 |
水利工程 | 2168篇 |
石油天然气 | 6394篇 |
武器工业 | 910篇 |
无线电 | 12016篇 |
一般工业技术 | 12578篇 |
冶金工业 | 5073篇 |
原子能技术 | 1294篇 |
自动化技术 | 15471篇 |
出版年
2024年 | 410篇 |
2023年 | 1663篇 |
2022年 | 3031篇 |
2021年 | 4343篇 |
2020年 | 3261篇 |
2019年 | 2879篇 |
2018年 | 3264篇 |
2017年 | 3542篇 |
2016年 | 3277篇 |
2015年 | 4408篇 |
2014年 | 5608篇 |
2013年 | 6658篇 |
2012年 | 7355篇 |
2011年 | 8122篇 |
2010年 | 7417篇 |
2009年 | 6972篇 |
2008年 | 6789篇 |
2007年 | 6505篇 |
2006年 | 6230篇 |
2005年 | 5269篇 |
2004年 | 3842篇 |
2003年 | 3520篇 |
2002年 | 3757篇 |
2001年 | 3171篇 |
2000年 | 2435篇 |
1999年 | 2321篇 |
1998年 | 1620篇 |
1997年 | 1380篇 |
1996年 | 1361篇 |
1995年 | 1041篇 |
1994年 | 798篇 |
1993年 | 614篇 |
1992年 | 465篇 |
1991年 | 357篇 |
1990年 | 265篇 |
1989年 | 214篇 |
1988年 | 187篇 |
1987年 | 119篇 |
1986年 | 94篇 |
1985年 | 49篇 |
1984年 | 40篇 |
1983年 | 32篇 |
1982年 | 39篇 |
1981年 | 15篇 |
1980年 | 26篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 13篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
921.
922.
923.
D. B. Min 《Journal of the American Oil Chemists' Society》1983,60(3):544-545
Soybean oil, hydrogenated soybean oil, and corn oil were exposed to fluorescent light for different periods of time to obtain a wide range of flavor qualities. The flavor qualities of these oils were evaluated by sensory and gas Chromatographic methods. Sensory evaluation was conducted using a 10-point hedonic scale to rate overall flavor quality. The sensory panel was made up of 94 members from 8 different laboratories. The correlation coefficients (r) of the flavor scores between sensory evaluation and instrumental analysis for soybean oil, hydrogenated soybean oil, and corn oil were 0.95, 0.97 and 0.97, respectively. These results were very close to the correlation coefficients (r) 0.99, 0.98 and 0.95 obtained from 10 sensory panel members from one specific laboratory. 相似文献
924.
The deposition of coke from methane on a Ni/MgAl2O4 catalyst 总被引:1,自引:0,他引:1
Temperature-programmed reaction techniques and Raman spectroscopy were used to characterize coke species deposited on a 5% Ni/MgAl2O4 catalyst for dry reforming of methane. The CH4 temperature-programmed decomposition profiles showed that the ignited decomposition temperatures of CH4 increased from 273 to 378 °C when MgAl2O4 replaced the catalyst support γ-Al2O3. The temperature-programmed oxidation, temperature-programmed hydrogenation and temperature-programmed CO2 reaction profiles showed that there were three carbon species (i.e. Cα, Cβ and Cγ) on the catalyst surface. Raman spectroscopy showed that Cγ was graphite-like carbon species, which was responsible for catalyst deactivation. The Cγ species was the most inactive species toward H2 and O2, while it was unexpectedly more active toward CO2. The unique reactivity of CO2 with different coke specie could be ascribed to the carbonate, bidentate and formate species formation on MgAl2O4 surface. These surface species enhanced the oxidation of Cγ species and thus contributed to the high stability of Ni/MgAl2O4 catalyst. 相似文献
925.
A new kind of organophilic clay, cotreated by methyl tallow bis‐2‐hydroxyethyl quaternary ammonium and epoxy resin into sodium montmorillonite (to form a strong interaction with polyamide 66 matrix), was prepared and used in preparing PA66/clay nanocomposites (PA66CN) via melt‐compounding method. Three different types of organic clays, CL30B–E00, CL30B–E12, and CL30B–E23, were used to study the effect of epoxy resin in PA66CN. The morphological, mechanical, and thermal properties have been studied using X‐ray diffraction, transmission electron microscopy (TEM), mechanical, and thermal analysis, respectively. TEM analysis of the nanocomposites shows that most of the silicate layers were exfoliated to individual layers and to some thin stacks containing a few layers. PA66CX–E00 and PA66CX–E12 had nearly exfoliated structures in agreement with the SAXS results, while PA66CX–E23 shows a coexistence of intercalated and exfoliated structures. The storage modulus of PA66 nanocomposites was higher than that of the neat PA66 in the whole range of tested temperature. On the other hand, the magnitude of the loss tangent peak in α‐ or β‐transition region decreased gradually with the increase in the clay loading. Multiple melting behavior in PA66 was also observed. Thermal stability more or less decreased with an increasing inorganic content. Young's modulus and tensile strength were enhanced by introducing organoclay. Among the three types of nanocomposites prepared, PA66CX–E12 showed the highest improvement in properties, while PA66CX–E23 showed properties inferior to that of PA66CX–E00 without epoxy resin. In conclusion, an optimum amount of epoxy resin is required to form the strong interaction with the amide group of PA66. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1711–1722, 2006 相似文献
926.
针对TD-LTE系统中同步性错误随机发生的问题,提出了一种通过ARM+DSP+FPGA平台的嵌入式系统实现帧号和原语的同步校正方法。该方法基于TD-LTE射频一致性测试仪表硬件平台,通过该嵌入式系统中ARM、DSP、FPGA间的协调工作,由GPMC模块通过帧号和原语两方面对系统同步性进行校正。在TD-LTE射频一致性测试仪表硬件平台中进行了验证,结果表明,该方法在实现帧号与子帧号同步校正的基础上明显提高了TD-LTE系统通信的稳定性。 相似文献
927.
928.
929.
930.
Identical twins pose a great challenge to face recognition due to high similarities in their appearances. Motivated by the psychological findings that facial motion contains identity signatures and the observation that twins may look alike but behave differently, we develop a talking profile to use the identity signatures in the facial motion to distinguish between identical twins. The talking profile for a subject is defined as a collection of multiple types of usual face motions from the video. Given two talking profiles, we compute the similarities of the same type of face motion in both profiles and then perform the classification based on those similarities. To compute the similarity of each type of face motion, we give higher weights to more abnormal motions which are assumed to carry more identity signature information. 相似文献