首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7168篇
  免费   573篇
  国内免费   301篇
电工技术   348篇
综合类   377篇
化学工业   1156篇
金属工艺   476篇
机械仪表   485篇
建筑科学   587篇
矿业工程   226篇
能源动力   133篇
轻工业   465篇
水利工程   136篇
石油天然气   624篇
武器工业   57篇
无线电   750篇
一般工业技术   867篇
冶金工业   471篇
原子能技术   71篇
自动化技术   813篇
  2024年   8篇
  2023年   118篇
  2022年   200篇
  2021年   328篇
  2020年   230篇
  2019年   187篇
  2018年   211篇
  2017年   218篇
  2016年   200篇
  2015年   296篇
  2014年   331篇
  2013年   442篇
  2012年   424篇
  2011年   486篇
  2010年   407篇
  2009年   379篇
  2008年   431篇
  2007年   389篇
  2006年   382篇
  2005年   318篇
  2004年   179篇
  2003年   164篇
  2002年   156篇
  2001年   152篇
  2000年   173篇
  1999年   211篇
  1998年   195篇
  1997年   152篇
  1996年   128篇
  1995年   115篇
  1994年   104篇
  1993年   88篇
  1992年   60篇
  1991年   39篇
  1990年   32篇
  1989年   26篇
  1988年   14篇
  1987年   11篇
  1986年   10篇
  1985年   8篇
  1984年   5篇
  1983年   6篇
  1982年   3篇
  1981年   6篇
  1980年   5篇
  1977年   2篇
  1976年   3篇
  1975年   3篇
  1971年   3篇
  1969年   1篇
排序方式: 共有8042条查询结果,搜索用时 15 毫秒
1.
Multimedia Tools and Applications - Semantic segmentation of ocean remote sensing images classifies each pixel in the image according to the ocean background and island type, and is an important...  相似文献   
2.
In the present research,nutrient broth(NB)medium was identified to be able to neutralize the antibac-terial activity of chitosan and its derivatives.Therefore,an improved test method independent of NB medium was proposed to precisely quantify the antibacterial effectiveness and efficiency of chitosan.The minimum bactericidal concentration(MBC)of chitosan was 60 μg mL-1 against S.aureus and E.coli,and 0.01%(w/v)chitosan could kill 100%of bacteria within 3 min.From another point of view,the neutralizing efficiency of NB could be tripled by adding 25 g L-1 of sodium chloride.Then the neutraliz-ing mechanism of NB medium was ascribed to flocculation between chitosan and protein.Adding extra sodium chloride could significantly reduce the size of floccules,and smaller floccules would lose the ability of binding with bacteria directly,showing higher neutralizing rate on the macro scale.  相似文献   
3.
建立了一种快速、灵敏测定药物中盐酸美西律的双波长分光光度法。在弱碱性溶液中,虎红与盐酸美西律反应生成离子缔合物,使溶液发生褪色现象,光谱曲线上呈现2个较强的负吸收峰,它们分别位于472和560 nm,在此2个波长处,盐酸美西律的线性范围为0.04~2.6 mg/L,表观摩尔吸光系数(κ)分别为5.87×104(472 nm)和3.59×104 L/(mol·cm)(560 nm),检出限为0.033(472 nm)和0.035 mg/L(560 nm)。用双波长法测定时,其表观摩尔吸光系数(κ)达9.46×104 L/(mol·cm),检出限为0.017 mg/L。双波长法用于盐酸美西律药片测定,加标回收率为97.7%~103%,相对标准偏差(RSD)为2.2%~2.6%。  相似文献   
4.
The micro-arc oxidation (MAO) coatings were prepared in four different electrolyte systems, including mixed acid, phosphate, phosphate-aluminate and phosphate-silicate electrolytes. The friction and wear properties of MAO coatings in ambient air, seawater and four groups of saline solutions related to seawater were investigated. The results showed that the addition of silicate to phosphate could increase the density of the coating. The phosphate-aluminate ceramic layer exhibited the lowest wear rate in various environments. Additionally, the friction coefficient and wear rate of MAO coating in seawater were lower than those in ambient air, which was due to the boundary lubrication effect of seawater. Meanwhile, the presence of divalent metal salts in seawater made its lubricity better than other salt solutions.  相似文献   
5.
研究了不同等温退火工艺对8030铝合金导线组织及性能的影响。结果表明:等温退火前后合金均由α-Al基体和Al6Fe相组成。在同一等温温度下,随着等温时间的延长组织逐渐趋于均匀化;同一等温时间下,随着等温温度的升高,组织趋于均匀化的时间缩短。经过等温退火处理后铝合金导线的导电率均有所提高,在470 ℃均匀化退火24 h后再经240 ℃等温4 h,合金导电率达到最高值57.21%IACS,比未经热处理试样的导电率提高了2.4%IACS。经过等温退火处理后铝合金导线的硬度及抗拉强度均有所降低,塑性大幅度提高。在470 ℃均匀化退火24 h后再经260 ℃等温8 h,合金的伸长率最高可达23.64%。热处理前后合金均为塑性断裂。  相似文献   
6.
Although WeChat has recently spawned significant resolutions in technology-mediated social contact and interpersonal communication, the research regarding the social and psychological impacts of the newly emerging technology is relatively few. The primary purpose of the current empirical research is to unearth whether and how WeChat interaction could enhance overseas students’ sense of subjective well-being by concentrating on social integration, bridging relationships, and bonding relationships. Using web-based data of 228 Chinese subjects, the obtained results reveal that the time spent on WeChat significantly and directly impacts users’ subjective well-being. Additionally, the findings demonstrate that social integration, bridging relationships, bonding relationships are all significant predictors to subjective well-being. Furthermore, the perceptions of social integration and social capital could play the crucial mediating roles in the connection between WeChat use and the dependent variable of subjective well-being. Therefore, these outcomes may shed light on a more nuanced comprehending of the influence of the new social media interaction on sojourner’s social adaption and overall life quality in the digital age.  相似文献   
7.
Despite a substantial literature suggests that computer-mediated communication impact individuals’ various psychosocial factors, relatively few studies have elucidated the underlying mechanism behind these associations. Building upon self-disclosure theory and previous studies, the principal purpose of this present research is to systematically explore the relationships among microblog utilization, online self-disclosure, friendship maintenance, and perceived life satisfaction. A web-based survey was implemented using a total of 426 university students in Northwestern China. Structural equation modeling reveals that intensity of microblog use is positively associated with these students’ friendship maintenance and life satisfaction. Additionally, online self-disclosure plays the crucial mediatory role in the relationships between microblog use, quality of relationships, and gratification with life. The results imply that as microbloggers disclosure their inner thoughts or emotional states with other users online, they could foster their friendship maintenance and obtain greater life satisfaction. However, contrary to the expectation, students’ friendship maintenance is not discovered to be a significant predictor of the sense of life satisfaction in the online environment. Overall, these obtained outcomes of the empirical work could offer new insights into the deep comprehending of the social psychological process of microblogging among younger generation in the new media context.  相似文献   
8.
Pang  Beibei  Hao  Fei  Yang  Yixuan  Park  Doo-Soon 《The Journal of supercomputing》2020,76(7):5442-5459
The Journal of Supercomputing - The increasing social problems on population, resources and environment enable the interaction between nature and humanity to become one of the most active research...  相似文献   
9.
Three temperature-sensitive monolithic columns were prepared by atom transfer radical polymerization and oxidation–reduction method using the initiator systems of CCl4/FeCl2, BPO/DMA, and APS/TEMED, respectively. The three monoliths were characterized by scanning electron microscopy, nitrogen adsorption, and thermogravimetric analysis. The obtained monolithic columns were used as on-line solid phase extraction sorbent coupled with high-performance liquid chromatography for the enrichment of β-sitosterol. By comparing some influencing factors on the adsorption, the optimum temperature-sensitive monolithic column which was initiated by CCl4/FeCl2 was selected for enrichment of β-sitosterol from plant oil. The maximum adsorption capacity of the monolith for β-sitosterol was 10.0031 mg/g. The limit of detection and limit of quantitation were 0.039 and 0.13 mg/mL, respectively. The recovery was in the range of 90.21–98.26%. The results showed that the monolith had better selectivity for β-sitosterol and could be used for enrichment of β-sitosterol in food samples. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47683.  相似文献   
10.
Single-phase polycrystalline Mo2BC ceramic bulks were synthesized successfully from molybdenum, boron, and graphite powders using the spark plasma sintering method. Herein, it was established that the synthesis temperature of the Mo2BC ceramic could be as low as 1300 °C. Transmission electron microscopy (TEM) characterization confirmed that the crystal structure of the Mo2BC ceramic was comparable to that of the MoAlB ceramic. The Vickers hardness of the Mo2BC ceramic was measured to be 18.1 GPa. Additionally, the compressive strength, flexural strength, and fracture toughness were determined to be 1.74 GPa, 457.72 MPa, and 3.26 MPa· m1/2, respectively. The Mo2BC bulk exhibited typical brittle features, in which intergranular and transgranular fractures were the main failure modes.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号