全文获取类型
收费全文 | 204251篇 |
免费 | 14794篇 |
国内免费 | 8226篇 |
专业分类
电工技术 | 9426篇 |
技术理论 | 11篇 |
综合类 | 19742篇 |
化学工业 | 20463篇 |
金属工艺 | 11205篇 |
机械仪表 | 18318篇 |
建筑科学 | 44335篇 |
矿业工程 | 7058篇 |
能源动力 | 5023篇 |
轻工业 | 9396篇 |
水利工程 | 5706篇 |
石油天然气 | 8114篇 |
武器工业 | 2225篇 |
无线电 | 12612篇 |
一般工业技术 | 21927篇 |
冶金工业 | 6196篇 |
原子能技术 | 1165篇 |
自动化技术 | 24349篇 |
出版年
2024年 | 391篇 |
2023年 | 2293篇 |
2022年 | 3978篇 |
2021年 | 5006篇 |
2020年 | 5205篇 |
2019年 | 4123篇 |
2018年 | 3963篇 |
2017年 | 5003篇 |
2016年 | 5578篇 |
2015年 | 6028篇 |
2014年 | 13639篇 |
2013年 | 11155篇 |
2012年 | 14263篇 |
2011年 | 15574篇 |
2010年 | 12785篇 |
2009年 | 13487篇 |
2008年 | 12122篇 |
2007年 | 14486篇 |
2006年 | 12682篇 |
2005年 | 11072篇 |
2004年 | 9012篇 |
2003年 | 8341篇 |
2002年 | 6814篇 |
2001年 | 5696篇 |
2000年 | 4692篇 |
1999年 | 3768篇 |
1998年 | 3018篇 |
1997年 | 2526篇 |
1996年 | 2073篇 |
1995年 | 1740篇 |
1994年 | 1495篇 |
1993年 | 1029篇 |
1992年 | 868篇 |
1991年 | 707篇 |
1990年 | 519篇 |
1989年 | 431篇 |
1988年 | 332篇 |
1987年 | 212篇 |
1986年 | 138篇 |
1985年 | 162篇 |
1984年 | 172篇 |
1983年 | 135篇 |
1982年 | 156篇 |
1981年 | 52篇 |
1980年 | 92篇 |
1979年 | 41篇 |
1978年 | 23篇 |
1976年 | 16篇 |
1975年 | 17篇 |
1959年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
航空发动机进气总温传感器测温误差研究 总被引:1,自引:0,他引:1
航空发动机进口总温测量的准确性是优化发动机控制率、保障发动机飞行安全的关键因素之一。针对影响传感器测量准确性的响应时间、恢复系数,通过空气动力学和热力学理论,分析出具体的影响因素,设计了多种结构模型,并通过热风洞试验、FloEFD软件建模和热流体仿真,从材料及结构上系统地提出了优化途径和改善办法并进行了验证,尤其是分析了双余度传感器的响应一致性误差并提出改善方法。研究结果为同类传感器的设计提供了参考和借鉴。 相似文献
103.
Han Yan Gu Yi Chen Lei Li Bing Liu Xiang Ming Chen 《International Journal of Applied Ceramic Technology》2020,17(2):790-796
SrLa[Ga1−x(R0.5Ti0.5)x]O4 (R = Mg, Zn) ceramics were prepared by a standard solid state sintering method. The single-phase ceramics with K2NiF4-type layered perovskite structure and I4/mmm space group were obtained, indicating that SrLa(R0.5Ti0.5) and SrLaGaO4 can form the unlimited solid solutions. With increasing x for R = Mg and Zn, εr increases monotonously, the Qf value first increases and then decreases, while τf increases from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: εr = 23.3, Qf = 89 400 GHz, τf = −0.8 ppm/°C for SrLa[Ga0.6(Mg0.5Ti0.5)0.4]O4 and εr = 23.3, Qf = 76 200 GHz, τf = 0.2 ppm/°C for SrLa[Ga0.7(Zn0.5Ti0.5)0.3]O4, indicating that the present solid solution ceramics are the promising candidates as microwave resonator materials for the telecommunication applications. 相似文献
104.
The molecular design of short peptides to achieve a tailor-made functional architecture has attracted attention during the past decade but remains challenging as a result of insufficient understanding of the relationship between peptide sequence and assembled supramolecular structures. We report a hybrid-resolution model to computationally explore the sequence–structure relationship of self-assembly for tripeptides containing only phenylalanine and isoleucine. We found that all these tripeptides have a tendency to assemble into nanofibers composed of laterally associated filaments. Molecular arrangements within the assemblies are diverse and vary depending on the sequences. This structural diversity originates from (1) distinct conformations of peptide building blocks that lead to different surface geometries of the filaments and (2) unique sidechain arrangements at the filament interfaces for each sequence. Many conformations are available for tripeptides in solution, but only an extended β-strand and another resembling a right-handed turn are observed in assemblies. It was found that the sequence dependence of these conformations and the packing of resulting filaments are determined by multiple competing noncovalent forces, with hydrophobic interactions involving Phe being particularly important. The sequence pattern for each type of assembly conformation and packing has been identified. These results highlight the importance of the interplay between conformation, molecular packing, and sequences for determining detailed nanostructures of peptides and provide a detailed insight to support a more precise design of peptide-based nanomaterials. 相似文献
105.
106.
Julio Flores-Gonzalez Juan Carlos Cancino-Díaz Leslie Chavez-Galan 《International journal of molecular sciences》2020,21(22)
Recent advances in the field of flow cytometry (FCM) have highlighted the importance of incorporating it as a basic analysis tool in laboratories. FCM not only allows the identification of cell subpopulations by detecting the expression of molecules in the cell membrane or cytoplasm, but it can also quantify and identify soluble molecules. The proper functioning of the FCM requires six fundamental systems, from those related to the transport of events to the systems dedicated to the analysis of information. In this review, we have identified the main considerations that every FCM user must know for an optimal antibody panel design, the quality systems that must govern the FCM protocols to guarantee reproducible results in research or clinical laboratories. Finally, we have introduced the current evidence that highlights the relevance of FCM in the investigation and clinical diagnosis of respiratory diseases, establishing important advances in the basic and clinical study of diseases as old as Tuberculosis along with the recent proposals for the monitoring and classification of patients infected with the new SARS-CoV2 virus. 相似文献
107.
108.
为了避免和减轻由过大隔震层位移引起的损害,对基础隔震框架结构装设调频液柱阻尼器(tuned liquid column damper,简称TLCD)后混合系统的减振效果进行研究。建立了单层和多层混合控制系统在地震作用下的运动方程,采用TLCD-结构体系转化为调频质量阻尼器(tuned mass damper,简称TMD)-结构体系的等效方法,利用TMD参数优化公式,得到单个TLCD初始设计参数,并采用状态空间方程得到多个TLCD最优设计参数。通过对某8层基础隔震结构进行模拟,证明了该理论设计方法的合理性。该混合结构不仅可以减小隔震层位移和加速度,而且对上部结构位移和加速度反应都能更有效的控制。 相似文献
109.
Xian‑Zhi Zhai Jin Qu Shu‑Meng Hao Ya‑Qiong Jing Wei Chang Juan Wang Wei Li Yasmine Abdelkrim Hongfu Yuan Zhong‑Zhen Yu 《纳微快报(英文)》2020,(4):137-151
Mn-based rechargeable aqueous zinc-ion batteries(ZIBs)are highly promising because of their high operating voltages,attractive energy densities,and eco-friendliness.However,the electrochemical performances of Mn-based cathodes usually suffer from their serious structure transformation upon charge/discharge cycling.Herein,we report a layered sodium-ion/crystal water co-intercalated Birnessite cathode with the formula of Na0.55Mn2O4·0.57H2O(NMOH)for high-performance aqueous ZIBs.A displacement/intercalation electrochemical mechanism was confirmed in the Mn-based cathode for the first time.Na+and crystal water enlarge the interlayer distance to enhance the insertion of Zn^2+,and some sodium ions are replaced with Zn^2+ in the first cycle to further stabilize the layered structure for subsequent reversible Zn^2+/H^+ insertion/extraction,resulting in exceptional specific capacities and satisfactory structural stabilities.Additionally,a pseudo-capacitance derived from the surface-adsorbed Na^+ also contributes to the electrochemical performances.The NMOH cathode not only delivers high reversible capacities of 389.8 and 87.1 mA h g^−1 at current densities of 200 and 1500 mA g^−1,respectively,but also maintains a good long-cycling performance of 201.6 mA h g^−1 at a high current density of 500 mA g^−1 after 400 cycles,which makes the NMOH cathode competitive for practical applications. 相似文献
110.
既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。 相似文献