全文获取类型
收费全文 | 130660篇 |
免费 | 16306篇 |
国内免费 | 8520篇 |
专业分类
电工技术 | 9951篇 |
技术理论 | 4篇 |
综合类 | 11296篇 |
化学工业 | 17968篇 |
金属工艺 | 4359篇 |
机械仪表 | 7584篇 |
建筑科学 | 8758篇 |
矿业工程 | 3614篇 |
能源动力 | 3302篇 |
轻工业 | 8198篇 |
水利工程 | 3696篇 |
石油天然气 | 3776篇 |
武器工业 | 1254篇 |
无线电 | 14730篇 |
一般工业技术 | 12035篇 |
冶金工业 | 5508篇 |
原子能技术 | 1733篇 |
自动化技术 | 37720篇 |
出版年
2024年 | 236篇 |
2023年 | 1815篇 |
2022年 | 3619篇 |
2021年 | 5262篇 |
2020年 | 4143篇 |
2019年 | 3745篇 |
2018年 | 3816篇 |
2017年 | 5005篇 |
2016年 | 6507篇 |
2015年 | 7289篇 |
2014年 | 9459篇 |
2013年 | 10025篇 |
2012年 | 9185篇 |
2011年 | 8910篇 |
2010年 | 6970篇 |
2009年 | 7290篇 |
2008年 | 7257篇 |
2007年 | 8981篇 |
2006年 | 8374篇 |
2005年 | 7313篇 |
2004年 | 5331篇 |
2003年 | 4991篇 |
2002年 | 3763篇 |
2001年 | 2926篇 |
2000年 | 2283篇 |
1999年 | 1842篇 |
1998年 | 1333篇 |
1997年 | 1106篇 |
1996年 | 988篇 |
1995年 | 864篇 |
1994年 | 807篇 |
1993年 | 585篇 |
1992年 | 496篇 |
1991年 | 412篇 |
1990年 | 360篇 |
1989年 | 333篇 |
1988年 | 249篇 |
1987年 | 159篇 |
1986年 | 147篇 |
1985年 | 131篇 |
1984年 | 162篇 |
1983年 | 122篇 |
1982年 | 89篇 |
1981年 | 75篇 |
1980年 | 78篇 |
1979年 | 45篇 |
1966年 | 43篇 |
1964年 | 65篇 |
1962年 | 77篇 |
1955年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
《International Journal of Hydrogen Energy》2022,47(94):39931-39942
A dual-coolant integrated experimental facility named DRAGON-V has been developed at the Institute of Nuclear Energy Safety Technology, Hefei Institute of Physical Science, Chinese Academy of Sciences, for the key technology research and performance evaluation of candidate liquid lithium-lead (PbLi) blanket of hydrogen fusion reactors. The loop is composed of a material test sub-loop and thermal-hydraulic test sub-loop, the design parameters are PbLi inventory 20 tons, PbLi temperature up to 550 °C, the maximum PbLi flow rate up to 40 kg/s. A novel cold trap system is designed to remove the suspended and crystalized impurities in PbLi fluid with three cooling zones and cross row arrangement of rod bundle filter elements. The paper describes the loop itself and its major components, initial loop testing, flow and measurement diagnostics and current experiments. The obtained test results of the loop and its components have demonstrated that the new facility is fully functioning and ready for experimental studies of material corrosion with/without a magnetic field, magnetohydrodynamic (MHD) effect, purification, heat and mass transfer phenomena in PbLi flows and can also be used in mock-up testing in conditions relevant to fusion applications. 相似文献
3.
Liu Yang Pengfei Yu Wenyuan Li Fengliang Cao Xin Jin Sheng Xue Xianglong Zhang Tingwei Zhang Mingbo Wu Wenting Wu 《American Institute of Chemical Engineers》2022,68(9):e17760
Hydrogen peroxide (H2O2) has been listed as one of the 100 most important chemicals in the world. However, huge amount of residual H2O2 is hard to timely decomposed into O2 and H2O under acidic condition, easily resulting in explosion hazard. Here, we reported a core–shell structure catalyst, that is graphene with Co N structure encapsulated Co nanoparticles. Co N graphene shell serves as the active site for the H2O2 decomposition, and Co core further enhance this decomposition. Benefiting from it, the H2O2 decomposition were close to 100% after 6 cycles without pH adjustment, which increased 6 orders of magnitude compared with no catalyst. At the same time, the O2 generation reached 99.67% in 2 h with little metal leaching, and ·OH has been greatly inhibited to only 0.08%. This work can cleanly remove H2O2 with little deep oxidation and protect the process of H2O2 utilization to achieve a safer world. 相似文献
4.
大规模多输入多输出(Multiple-Input Multiple-Output, MIMO)可以有效提升5G SA网络的上行链路数据传输速率以及可靠性。针对5G SA网络上行链路速率和覆盖不均衡的情况,提出了基于大规模MIMO的分组算法,将发送信号矢量进行分组,组内采用最大似然检测,组外采用基于正交三角分解(QR分解)的干扰消除检测,并且结合5G频谱的叠加策略,在降低算法复杂度的同时,有效提升网络覆盖和速率。通过5G SA现网实测,通过MIMO降低分组数量能够提升分组检测性能,结合上行低频段频谱叠加策略能够有效提升5G SA网络上行覆盖30%,提升5G SA网络上行平均速率40%~80%,特别是弱覆盖边缘的网络速率,最高可达600%。 相似文献
5.
Qing Pan Timon Rabczuk Chong Chen 《International journal for numerical methods in engineering》2022,123(2):610-633
We present a new isogeometric analysis (IGA) approach based on extended Loop subdivision scheme for solving various geometric flows defined on subdivision surfaces. The studied flows include the second-order, fourth-order, and sixth-order geometric flows, such as averaged mean curvature flow, constant mean curvature flow, and minimal mean-curvature-variation flow, which are generally derived by minimizing the associate energy functionals with -gradient flow respectively. The geometric flows are discretized by means of subdivision based IGA, where the finite element space is formulated by the limit form of the extended Loop subdivision for different initial control meshes. The basis functions, consisting of quartic box-splines corresponding to each subdivided control mesh, are utilized to represent the geometry exactly. For the cases of the evolution of open surfaces with any shape boundary, high-order continuous boundary conditions derived from the mixed variational forms of the geometric flows should be implemented to be consistent with the isogeometric concept. For time discretization, we adopt an adaptive semi-implicit Euler scheme. By several numerical experiments, we study the convergence behaviors of the proposed approach for solving the geometric flows with high-order boundary conditions. Moreover, the numerical results also show the accuracy and efficiency of the proposed method. 相似文献
6.
益生菌可在肠道定植从而发挥抗炎或抗氧化活性,有利于宿主肠道健康。本实验研究了从新疆传统发酵乳制品中分离得到的8?株植物乳杆菌对大肠杆菌侵袭和过氧化氢刺激肠上皮细胞HT-29的保护作用。结果表明:在8?株植物乳杆菌中,植物乳杆菌35具有最高的黏附能力。植物乳杆菌35可通过取代、竞争、排阻的方式抑制大肠杆菌对HT-29细胞的黏附,抑制率分别为42.60%、59.17%、60.19%。植物乳杆菌35及其多糖可抑制大肠杆菌刺激HT-29细胞产生白细胞介素-8;同时保护HT-29细胞免受过氧化氢的损伤,增加超氧化物歧化酶、谷胱甘肽过氧化物酶活力水平并降低丙二醛含量。结论:植物乳杆菌35及其粗胞外多糖具有抑制大肠杆菌O157诱导的炎症性肠病的潜力。 相似文献
7.
农村综合能源系统通过多种能源的协同互补,在满足农村用户多元化用能需求的同时,能有效提升能源利用效率和用能经济性。首先,在考虑适应农村典型场景的基础上,提出了一种三层协同自律的农村综合能源分层协同运行优化框架。然后,基于农村综合能源系统典型设备,建立了三层农村综合能源系统源-储-荷联合优化调度模型以及相应的优化调度流程。调度模型中冬季通过对沼气发电机组的余热回收与空气源热泵协同对用户供热;夏季对沼气发电机组余热进行回收,并通过溴化锂制冷机与空气源热泵联合对农村用户供冷。最后,对农村综合能源系统多层协同优化方法进行了算例分析,结果表明该优化方法提高了农村居民用能的经济性,验证了所提方法的有效性。 相似文献
8.
目的:探讨姜黄素的主要肠道代谢物四氢姜黄素(tetrahydrocurcumin,THC)对血小板活化和聚集的影响及其可能的分子机制。方法:在体外实验中,用不同浓度的THC(0、0.5、1、10 μmol/L)提前与健康人纯化血小板共同孵育40 min,然后加入凝血酶激活血小板2 min,用流式细胞术测定血小板表面CD62P和CD63的表达量,用酶联免疫吸附法测定血小板释放血小板因子-4(platelet factor-4,PF4)和趋化因子配体-5(chemokine ligand 5,CCL5)水平,用血小板聚集仪检测血小板释放ATP水平和血小板最大聚集率,用Western blot蛋白免疫印迹法检测血小板磷酸肌醇-3-激酶(phosphoinositide 3-kinase,PI3K)和Akt蛋白的磷酸化水平。结果:与模型组(血小板悬液中加入0.05%二甲基亚砜)相比,THC能抑制凝血酶诱导的血小板表面CD62P和CD63的表达,抑制PF4、CCL5和ATP的释放,降低血小板最大聚集率,下调PI3K和Akt蛋白的磷酸化水平,且呈浓度依赖效应,其中10 μmol/L的浓度下作用效果显著(P<0.01、P<0.001)。PI3K的特异性激动剂740 Y-P可部分逆转THC对PF4和CCL5释放和血小板聚集的抑制作用(P<0.05、P<0.01)。结论:THC具有显著抑制血小板活化和聚集的作用,其机制可能是THC可下调PI3K/Akt介导的信号通路。 相似文献
9.
10.
Flow phenomena of three-dimensional conducting Casson fluid through a stretching sheet are proposed in the present investigation with the impact of the magnetic parameter in a permeable medium. The adaptation of particular transformations is useful to modify the governing equations into their nondimensional as well as the ordinary form. However, these transformed equations are nonlinear and approximate analytical methods for the solution of the complex form of governing equations. In particular, the Adomian decomposition method is proposed for the solution. The behavior of several variables, such as the magnetic and porous matrix, on the flow profile as well as the rate of shear stress, are discussed via graphs and tables. The conformity of the current result with the earlier study shows a road map for further investigation. The major concluding remarks are; the retardation in the velocity distribution is rendered due to an increase in the Casson parameter moreover, the Casson parameter favors in reducing the rate of shear stress coefficient in magnitude. 相似文献