全文获取类型
收费全文 | 56866篇 |
免费 | 4762篇 |
国内免费 | 2481篇 |
专业分类
电工技术 | 3530篇 |
技术理论 | 3篇 |
综合类 | 3939篇 |
化学工业 | 9255篇 |
金属工艺 | 3302篇 |
机械仪表 | 3818篇 |
建筑科学 | 4504篇 |
矿业工程 | 1791篇 |
能源动力 | 1665篇 |
轻工业 | 3716篇 |
水利工程 | 1026篇 |
石油天然气 | 3858篇 |
武器工业 | 523篇 |
无线电 | 6188篇 |
一般工业技术 | 6810篇 |
冶金工业 | 2525篇 |
原子能技术 | 577篇 |
自动化技术 | 7079篇 |
出版年
2024年 | 100篇 |
2023年 | 988篇 |
2022年 | 1449篇 |
2021年 | 2265篇 |
2020年 | 1895篇 |
2019年 | 1520篇 |
2018年 | 1699篇 |
2017年 | 1872篇 |
2016年 | 1629篇 |
2015年 | 2248篇 |
2014年 | 2930篇 |
2013年 | 3279篇 |
2012年 | 3587篇 |
2011年 | 4036篇 |
2010年 | 3500篇 |
2009年 | 3276篇 |
2008年 | 3215篇 |
2007年 | 2974篇 |
2006年 | 3069篇 |
2005年 | 2561篇 |
2004年 | 1839篇 |
2003年 | 1627篇 |
2002年 | 1601篇 |
2001年 | 1376篇 |
2000年 | 1275篇 |
1999年 | 1506篇 |
1998年 | 1261篇 |
1997年 | 1099篇 |
1996年 | 989篇 |
1995年 | 821篇 |
1994年 | 659篇 |
1993年 | 477篇 |
1992年 | 413篇 |
1991年 | 260篇 |
1990年 | 210篇 |
1989年 | 164篇 |
1988年 | 119篇 |
1987年 | 77篇 |
1986年 | 61篇 |
1985年 | 41篇 |
1984年 | 32篇 |
1983年 | 27篇 |
1982年 | 29篇 |
1981年 | 17篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1940年 | 3篇 |
1933年 | 1篇 |
1929年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Neural Processing Letters - A lot of research attentions have been paid to image emotion analysis in recent years. Meanwhile, as convolutional neural networks (CNNs) have made great successful in... 相似文献
32.
Karn Pradeep He XiaoHai Zhang Jin Zhang Yanteng 《Multimedia Tools and Applications》2020,79(43-44):31783-31801
Multimedia Tools and Applications - Iris images collected under different conditions often suffer from specular reflections, cast shadows, motion blur, defocus blur, occlusion caused by eyelashes... 相似文献
33.
34.
Xian Suo Xili Cui Lifeng Yang Nan Xu Yuqi Huang Yi He Sheng Dai Huabin Xing 《Advanced materials (Deerfield Beach, Fla.)》2020,32(29):1907601
The design of highly stable and efficient porous materials is essential for developing breakthrough hydrocarbon separation methods based on physisorption to replace currently used energy-intensive distillation/absorption technologies. Efforts to develop advanced porous materials such as zeolites, coordination frameworks, and organic polymers have met with limited success. Here, a new class of ionic ultramicroporous polymers (IUPs) with high-density inorganic anions and narrowly distributed ultramicroporosity is reported, which are synthesized by a facile free-radical polymerization using branched and amphiphilic ionic compounds as reactive monomers. A covalent and ionic dual-crosslinking strategy is proposed to manipulate the pore structure of amorphous polymers at the ultramicroporous scale. The IUPs exhibit exceptional selectivity (286.1–474.4) for separating acetylene from ethylene along with high thermal and water stability, collaboratively demonstrated by gas adsorption isotherms and experimental breakthrough curves. Modeling studies unveil the specific binding sites for acetylene capture as well as the interconnected ultramicroporosity for size sieving. The porosity-engineering protocol used in this work can also be extended to the design of other ultramicroporous materials for the challenging separation of other key gas constituents. 相似文献
35.
安全壳泄漏率计算过程中,最重要的环节是以不同时刻测量数据对时间进行线性回归分析。对回归的显著性检验以及方差分析是评价试验结果有效性的重要手段。本文基于统计软件R对某电厂调试阶段安全壳泄漏率试验的数据进行分析,通过对线性回归模型的独立性、正态性和异方差性检验以及极端样本点的剔除等方式,探讨泄漏率计算前的回归诊断对计算结果可靠性的影响。通过回归诊断的实例分析发现,在安全壳泄漏率计算的数据样本中,可能存在自相关、非正态和异方差性等问题影响回归结果,进而影响泄漏率的最终结果。因此,在计算泄漏率结果时,须通过回归诊断方法评价数据的有效性,对不能通过检验的样本应通过适当方法对最终结果进行修正。 相似文献
36.
Earth-abundant IV-VI semiconductor SnSe is regarded as a promising thermoelectric material due to its intrinsic low thermal conductivity. In this report, the highly textured SnSe/Ag2 Se composites were first designed by solid solution method followed by spark plasma sintering(SPS) and their thermoelectric properties in two directions were investigated, and then, the performance of composites was further optimized with an additional ball milling. The coexistence of SnSe and Ag2 Se phases is clearly confirmed by energy-dispersive X-ray spectroscopy(EDX) in transmission electron microscopy(TEM). After ball milling, the size of SnSe grains as well as the incorporated Ag2 Se particles reduces effectively, which synergistically optimizes the electrical and thermal transport properties at high temperature range. As a result, a maximum ZT of ~0.74 at 773 K for SnSe+1.0%Ag_2 Se in the direction vertical to the pressing direction is achieved. Composite engineering with additional ball milling is thus proved to be an efficient way to improve the thermoelectric properties of SnSe, and this strategy could be applicable to other thermoelectric systems. 相似文献
37.
38.
为了给辉县景区减灾防灾提供地质依据,根据实际工程概况,研究了辉县部分景区地质灾害危险性预测评估及防治措施,预测评估了工程建设中、建设后可能引发或加剧地质灾害危险性,建设工程自身可能遭受已存在地质灾害危险性;评估了地质灾害危险性综合分区以及根据地质灾害危险性、防治难度和防治效益,对评估区适宜性作出评价,提出了防治地质灾害的措施和建议。 相似文献
39.
Zhanchong Zhao Xianhui Li Yong Zhang Chenwei He Xiaoxin Zhang Huayan Liu Qingzhi Yan 《International Journal of Applied Ceramic Technology》2020,17(4):1713-1722
Impeller is the key part of centrifugal pump to convey liquid. And combined with the engineering practice, we fabricated two types of open and semi-open SiC ceramic impellers with diameter of 100 mm and 160 mm via gelcasting and pressureless sintering. B4C and C were used as the sintering additives and sprayed drying granulation method was adopted for the starting SiC powder processing. Given the size and shape complexity of impeller, the optimized pH value, dispersant content, and solid-loading content for the fabrication of the SiC impellers were determined to be 10-11, 0.8 wt%, and 40 vol%, respectively. For the open impeller, blade height, cover board thickness, drying shrinkage, and sintering shrinkage are 10.5 mm, 4 mm, 10.3%, and 21.3%, respectively. For the semi-open ones, the corresponding parameters are 41 mm, 10 mm, 10.3%, and 21.3%, respectively. The average density of the two types of impellers is 3.15 g/cm3, and the mechanical properties of both impellers, including average hardness, flexural strength, compressive strength, and fracture toughness are 2478 HV, 436 MPa, 2093 MPa, and 3.17 MPa·m1/2, respectively. All variation coefficient values are smaller than 5%, which indicates a good uniformity in densities and mechanical properties of both the impellers. 相似文献
40.