全文获取类型
收费全文 | 153927篇 |
免费 | 15602篇 |
国内免费 | 9115篇 |
专业分类
电工技术 | 12136篇 |
技术理论 | 3篇 |
综合类 | 12301篇 |
化学工业 | 22557篇 |
金属工艺 | 9898篇 |
机械仪表 | 10803篇 |
建筑科学 | 12179篇 |
矿业工程 | 5029篇 |
能源动力 | 4476篇 |
轻工业 | 10036篇 |
水利工程 | 3642篇 |
石油天然气 | 7675篇 |
武器工业 | 1876篇 |
无线电 | 18344篇 |
一般工业技术 | 16139篇 |
冶金工业 | 6642篇 |
原子能技术 | 1888篇 |
自动化技术 | 23020篇 |
出版年
2024年 | 533篇 |
2023年 | 1915篇 |
2022年 | 4275篇 |
2021年 | 5998篇 |
2020年 | 4446篇 |
2019年 | 3543篇 |
2018年 | 3969篇 |
2017年 | 4649篇 |
2016年 | 4399篇 |
2015年 | 6521篇 |
2014年 | 8114篇 |
2013年 | 9618篇 |
2012年 | 11613篇 |
2011年 | 12265篇 |
2010年 | 11564篇 |
2009年 | 11261篇 |
2008年 | 10913篇 |
2007年 | 10452篇 |
2006年 | 9587篇 |
2005年 | 8060篇 |
2004年 | 5794篇 |
2003年 | 5085篇 |
2002年 | 5076篇 |
2001年 | 4449篇 |
2000年 | 3175篇 |
1999年 | 2674篇 |
1998年 | 1647篇 |
1997年 | 1464篇 |
1996年 | 1257篇 |
1995年 | 1000篇 |
1994年 | 805篇 |
1993年 | 577篇 |
1992年 | 432篇 |
1991年 | 344篇 |
1990年 | 285篇 |
1989年 | 237篇 |
1988年 | 172篇 |
1987年 | 116篇 |
1986年 | 94篇 |
1985年 | 38篇 |
1984年 | 40篇 |
1983年 | 24篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1976年 | 7篇 |
1959年 | 10篇 |
1951年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Qiang Xia Tao Feng Xiaowei Lou Ying Wang Yangying Sun Daodong Pan Jinxuan Cao 《International Journal of Food Science & Technology》2020,55(2):669-680
As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples. 相似文献
92.
Shuang Shao Yong Liu Chun-Shui Xu Ying-Xuan Xu Bin Wu Xiao-Shu Zeng Xian-Feng Lu Xiang-Jie Yang 《金属学报(英文版)》2015,(1):7-14
The microstructure and mechanical properties of Mg–6Zn–1Y and Mg–6Zn–3Y(wt%) alloys under different cooling rates were investigated. The results show that the second dendrite arm spacing(SDAS) of Mg–6Zn–1Y and Mg–6Zn–3Y is reduced by 32 and 30% with increasing cooling rates(Rc) from 10.2 to 23 K/s, which can be predicted using a empirical model of SDAS=68 R 0:45:45cand SDAS=73 R 0c, respectively. The compressive strength of both alloys increases with increasing the cooling rate, which is attributed to the increase of volume fraction(Vf) of secondary phases under high cooling rate. The interaction of the cooling rate and component with SDAS has been theoretically analyzed using interdependence theory. 相似文献
93.
94.
95.
The hippocampus is crucial in learning, memory and emotion processing, and is involved in the development of different neurological and neuropsychological disorders. Several epigenetic factors, including DNA methylation, histone modifications and non-coding RNAs, have been shown to regulate the development and function of the hippocampus, and the alteration of epigenetic regulation may play important roles in the development of neurocognitive and neurodegenerative diseases. This review summarizes the epigenetic modifications of various cell types and processes within the hippocampus and their resulting effects on cognition, memory and overall hippocampal function. In addition, the effects of exposure to radiation that may induce a myriad of epigenetic changes in the hippocampus are reviewed. By assessing and evaluating the current literature, we hope to prompt a more thorough understanding of the molecular mechanisms that underlie radiation-induced epigenetic changes, an area which can be further explored. 相似文献
96.
Yong Liu Kangzhuang Chen Fengbo Dong Shuai Peng Yongjie Cui Chenyu Zhang Keqing Han Muhuo Yu Hui Zhang 《Ceramics International》2018,44(9):10199-10203
In this paper, polyborosilazane precursor was synthesied from HMDZ, HSiCl3, BCl3 and CH3NH2 using a multistep method. By controlling the storage conditions, parts of the polyborosilazane fibers were hydrolyzed. FT-IR, NMR, XRD, TEM and monofilament tensile strength test were employed to study the effects of hydrolysis of precursor on the structures and properties of polymer-derived SiBN ceramic fibers. FT-IR and NMR results indicate that Si-N group in PBSZ reacts with H2O to form Si-O-Si group. After pyrolysis reaction at 1400℃, Si-O-Si group will finally transformed into highly ordered cristobalite and β-quartz, resulting in formation of the wrinkled surface of the obtained SiBN ceramic fiber. The strip-like defects on fiber surface, according to monofilament tensile strength test, had a significant effect on mechanical property of the obtained SiBN ceramic fiber and caused no increase in fiber tensile strength of hydrolytic polyborosilazane fiber before and after pyrolytic process. 相似文献
97.
通过对CSFB语音方案原理的分析,结合业务模型及网络安全等方面的考虑,提出了一种支持4G CSFB的MSC改造规模预测方法,为端局后续建设提供了参考. 相似文献
98.
摘要:为了研究退火温度对镀锌DP980+Z烘烤硬化值的影响,退火温度控制在760~820℃之间,系统分析退火温度对烘烤硬化值的影响。通过准静态拉伸试验机测量烘烤硬化值及抗拉强度,采用lepara试剂对组织中的马氏体进行着色,利用金相显微镜及图像处理软件测量马氏体的体积分数;采用扫描电镜观察DP980+Z的双相组织特点,并且将组织图片通过CAD转化成有限元图进行网格划分,建立代表性体积单元(RVE),通过有限元分析铁素体、马氏体强度对烘烤硬化值的影响。在同样的变形量情况下,DP980+Z的原始屈服强度越高,烘烤硬化值越高。 相似文献
99.
Qiang Wang Lei Shen Tong Xue Gao Cheng Cheng Zhi Huang Hong Jin Fan Yuan Ping Feng 《Advanced functional materials》2021,31(2):2002187
The {100} facet of single-crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures. 相似文献
100.
该文针对当前矿井炮掘巷道大断面掘进普遍存在掘进施工较慢的实际,结合公司实际情况,有针对性地提出了解决的办法。 相似文献