全文获取类型
收费全文 | 53284篇 |
免费 | 5911篇 |
国内免费 | 3157篇 |
专业分类
电工技术 | 3186篇 |
技术理论 | 1篇 |
综合类 | 3930篇 |
化学工业 | 8961篇 |
金属工艺 | 2941篇 |
机械仪表 | 3467篇 |
建筑科学 | 3531篇 |
矿业工程 | 1314篇 |
能源动力 | 1348篇 |
轻工业 | 5860篇 |
水利工程 | 1138篇 |
石油天然气 | 2011篇 |
武器工业 | 464篇 |
无线电 | 6419篇 |
一般工业技术 | 6538篇 |
冶金工业 | 2097篇 |
原子能技术 | 657篇 |
自动化技术 | 8489篇 |
出版年
2024年 | 278篇 |
2023年 | 857篇 |
2022年 | 1647篇 |
2021年 | 2178篇 |
2020年 | 1679篇 |
2019年 | 1506篇 |
2018年 | 1678篇 |
2017年 | 1828篇 |
2016年 | 1750篇 |
2015年 | 2334篇 |
2014年 | 2924篇 |
2013年 | 3576篇 |
2012年 | 4130篇 |
2011年 | 4571篇 |
2010年 | 4073篇 |
2009年 | 3963篇 |
2008年 | 3809篇 |
2007年 | 3528篇 |
2006年 | 3236篇 |
2005年 | 2682篇 |
2004年 | 1948篇 |
2003年 | 1534篇 |
2002年 | 1432篇 |
2001年 | 1189篇 |
2000年 | 899篇 |
1999年 | 715篇 |
1998年 | 446篇 |
1997年 | 376篇 |
1996年 | 313篇 |
1995年 | 235篇 |
1994年 | 193篇 |
1993年 | 168篇 |
1992年 | 126篇 |
1991年 | 106篇 |
1990年 | 77篇 |
1989年 | 68篇 |
1988年 | 51篇 |
1987年 | 44篇 |
1986年 | 31篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 18篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
为了给海面溢油污染识别检测提供理论基础,根据菲涅尔反射公式的偏振反射系数,结合偏振双向反射率因子和粗糙海面的概率密度分布函数,建立了完善的pBRDF模型,仿真在不同太阳入射角度、不同探测器观测角度以及不同海面风速风向等条件下海水和油膜的偏振反射分布函数。结果表明:海水和油膜太阳天顶角为53°和56°时P偏振反射率分别为1.0×10^-5和2.5×10^-5,S偏振反射率随着太阳天顶角的增加而增加;海面风速越大偏振反射率峰值越小;海面风向只改变pBRDF的空间位置;海水和油膜线偏振度空间分布有明显差异。搭建实验平台相机以40°拍摄时,得出海水和油膜的线偏振度分别在0.2~0.4, 0.5~0.7之间,同时表明利用偏振探测获取目标场景的偏振度和偏振角图可提高图像质量。 相似文献
32.
Sowoon Seo Yunjeong Song Sun Mi Gu Hyun Kyu Min Jin Tae Hong Hye Jin Cha Jaesuk Yun 《International journal of molecular sciences》2020,21(23)
Background: Epilepsy is a chronic neurological disorder characterized by the recurrence of seizures. One-third of patients with epilepsy may not respond to antiseizure drugs. Purpose: We aimed to examine whether D-limonene, a cyclic monoterpene, exhibited any antiseizure activity in the pentylenetetrazole (PTZ)-induced kindling mouse model and in vitro. Methods: PTZ kindling mouse model was established by administering PTZ (30 mg/kg) intraperitoneally to mice once every 48 h. We performed immunoblot blots, immunohistochemistry (IHC), and high-performance liquid chromatography (HPLC) analysis after the behavioral study. Results: An acute injection of PTZ (60 mg/kg) induced seizure in mice, while pretreatment with D-limonene inhibited PTZ-induced seizure. Repeated administration of PTZ (30 mg/kg) increased the seizure score gradually in mice, which was reduced in D-limonene (10 mg/kg)-pretreated group. In addition, D-limonene treatment increased glutamate decarboxylase-67 (GAD-67) expression in the hippocampus. Axonal sprouting of hippocampal neurons after kindling was inhibited by D-limonene pretreatment. Moreover, D-limonene reduced the expression levels of Neuronal PAS Domain Protein 4 (Npas4)-induced by PTZ. Furthermore, the adenosine A2A antagonist and ZM241385 inhibited anticonvulsant activity and gamma-aminobutyric acid (GABA)ergic neurotransmission-induced by D-limonene. Conclusion: These results suggest that D-limonene exhibits anticonvulsant activity through modulation of adenosine A2A receptors on GABAergic neuronal function. SCH58261相似文献
33.
The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was investigated.The key of magnetizing-roasting is the gasification reaction between reductants and CO2.Since biochar could react with CO2 more rapidly at lower temperature,the reactivity of biochar is better than that of anthracite.The gasification of biochar could produce reducing condition ofφCO/(φCO+φCO2)about 10%-20% between 700-800 ℃,which is in accord with the atmosphere and temperature of Fe2O3 reduction.So it is beneficial to the reduction of iron mineral of pyrite cinder.Compared with anthracite,biochar could decrease the roasting temperature from825 to 750 ℃ and roasting time from 20 to 15min,which shows that a better effect of magnetization could be obtained in the condition of lower temperature and shorter time.Using biochar as reductant,iron concentrate extracted from pyrite cinder as about 64%iron grade could be produced,and the recovery is over 90% under the condition of above 90% grinding particle less than 0.045 mm and magnetic intensity of 0.124-0.194 T. 相似文献
34.
35.
Ha-Nul Lee Joo-Hee Choi Ji-Yeon Park Jae-Hun Ahn Da Eun Jang Jae Gun Shim Jong-Hwan Park Young-Min Kim 《Food science and biotechnology》2021,30(4):583
Vegetable soup (VS), a plant-based functional food, has been used as a traditional folk medicine and is attracting attention for its ability to enhance the immune response. β-Glucan, a well-established and effective immunomodulator, has synergistic effects when used in combination with some bioactive compounds. In the present study, we aimed to evaluate the synergistic immunomodulatory effects of the combination of VS and β-glucan on macrophage-mediated immune responses. β-Glucan was demonstrated to synergistically enhance the VS-stimulated immune response, including the production of interleukin-6, tumor necrosis factor-α, and nitric oxide, mainly through the mitogen-activated protein kinase pathway in macrophages. In addition, this combination has the potential for further development in functional foods with immune-enhancing activity.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10068-021-00888-x. 相似文献
36.
37.
硫化物预处理方法研究及测定中的质量保证 总被引:1,自引:0,他引:1
针对水和废水中硫离子的特点,设计制作了测定硫化物的酸化—吹气—吸收预处理装置,并验证了该装置对硫化物的回收效果,简化了原来的预处理方法。总结分光测定过程中注意的若干事项,确定了最佳实验条件,使该方法具有更准确、简便、快速的特点。 相似文献
38.
Supported metal catalysts, particularly noble metals supported on SiO2, have attracted considerable attention due to the importance of the silica–metal interface in heterogeneous catalysis and in electronic device fabrication. Several important issues, e.g., the stability of the metal–oxide interface at working temperatures and pressures, are not well-understood. In this review, the present status of our understanding of the metal–silica interface is reviewed. Recent results of model studies in our laboratories on Pd/SiO2/Mo(1 1 2) using LEED, AES and STM are reported. In this work, epitaxial, ultrathin, well-ordered SiO2 films were grown on a Mo(1 1 2) substrate to circumvent complications that frequently arise from the silica–silicon interface present in silica thin films grown on silicon. 相似文献
39.
改进型UDP组播的性能分析及其在实时电源控制系统中的应用 总被引:1,自引:0,他引:1
文章通过采用带连接的UDP、I/O复用技术、关闭UDP校验和功能、负载均衡等技术对普通的UDP组播技术进行改进,使之在每个控制周期(1ms)内满足了分布式实时控制系统的实时性和可靠性要求。在将改进型的UDP组播技术应用于实际控制系统之前,文中构建了一个模拟局域网进行测试,对比结果表明改进后的组播技术无论在数据包延迟、丢包率等方面较改进前的UDP组播性能有较大幅度的提高。 相似文献
40.
基于虚拟仪器的现代温度检测系统的研究 总被引:3,自引:0,他引:3
对一个基于虚拟仪器的现代温度检测系统进行了系统的论述,并给出了具体实现方案及结果。 相似文献