全文获取类型
收费全文 | 206673篇 |
免费 | 29139篇 |
国内免费 | 15142篇 |
专业分类
电工技术 | 19600篇 |
技术理论 | 2篇 |
综合类 | 21901篇 |
化学工业 | 25684篇 |
金属工艺 | 13916篇 |
机械仪表 | 15358篇 |
建筑科学 | 16261篇 |
矿业工程 | 9180篇 |
能源动力 | 5814篇 |
轻工业 | 23455篇 |
水利工程 | 6564篇 |
石油天然气 | 8189篇 |
武器工业 | 3234篇 |
无线电 | 22816篇 |
一般工业技术 | 17505篇 |
冶金工业 | 8225篇 |
原子能技术 | 3521篇 |
自动化技术 | 29729篇 |
出版年
2025年 | 31篇 |
2024年 | 3855篇 |
2023年 | 4244篇 |
2022年 | 8624篇 |
2021年 | 11027篇 |
2020年 | 8083篇 |
2019年 | 5561篇 |
2018年 | 5953篇 |
2017年 | 7121篇 |
2016年 | 6284篇 |
2015年 | 9813篇 |
2014年 | 12220篇 |
2013年 | 14156篇 |
2012年 | 17248篇 |
2011年 | 17825篇 |
2010年 | 16875篇 |
2009年 | 16313篇 |
2008年 | 16384篇 |
2007年 | 15552篇 |
2006年 | 13497篇 |
2005年 | 10663篇 |
2004年 | 7781篇 |
2003年 | 5185篇 |
2002年 | 4878篇 |
2001年 | 4235篇 |
2000年 | 3331篇 |
1999年 | 1327篇 |
1998年 | 520篇 |
1997年 | 393篇 |
1996年 | 337篇 |
1995年 | 302篇 |
1994年 | 209篇 |
1993年 | 161篇 |
1992年 | 142篇 |
1991年 | 104篇 |
1990年 | 115篇 |
1989年 | 94篇 |
1988年 | 55篇 |
1987年 | 51篇 |
1986年 | 45篇 |
1985年 | 26篇 |
1984年 | 31篇 |
1983年 | 26篇 |
1982年 | 21篇 |
1981年 | 31篇 |
1980年 | 55篇 |
1979年 | 42篇 |
1976年 | 18篇 |
1959年 | 32篇 |
1951年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
1.
Yifan Zhang Shaowei Bo Tao Feng Xialing Qin Yilin Wan Shanshan Jiang Chunxiao Li Jing Lin Tianfu Wang Xin Zhou Zhong‐Xing Jiang Peng Huang 《Advanced materials (Deerfield Beach, Fla.)》2019,31(21)
To design a clinically translatable nanomedicine for photodynamic theranostics, the ingredients should be carefully considered. A high content of nanocarriers may cause extra toxicity in metabolism, and multiple theranostic agents would complicate the preparation process. These issues would be of less concern if the nanocarrier itself has most of the theranostic functions. In this work, a poly(ethylene glycol)‐boron dipyrromethene amphiphile (PEG‐F54‐BODIPY) with 54 fluorine‐19 (19F) is synthesized and employed to emulsify perfluorohexane (PFH) into a theranostic nanoemulsion (PFH@PEG‐F54‐BODIPY). The as‐prepared PFH@PEG‐F54‐BODIPY can perform architecture‐dependent fluorescence/photoacoustic/19F magnetic resonance multimodal imaging, providing more information about the in vivo structure evolution of nanomedicine. Importantly, this nanoemulsion significantly enhances the therapeutic effect of BODIPY through both the high oxygen dissolving capability and less self‐quenching of BODIPY molecules. More interestingly, PFH@PEG‐F54‐BODIPY shows high level of tumor accumulation and long tumor retention time, allowing a repeated light irradiation after a single‐dose intravenous injection. The “all‐in‐one” photodynamic theranostic nanoemulsion has simple composition, remarkable theranostic efficacy, and novel treatment pattern, and thus presents an intriguing avenue to developing clinically translatable theranostic agents. 相似文献
2.
Bo Wu Huiying Du Ping Hu Zhanyu Gao Ruikai Liu Chonghua Pei 《Journal of Energetic Materials》2021,39(1):10-22
ABSTRACT In recent years, the exploration of a practical strategy for novel energetic molecules with high energy and low sensitivity is very desirable but highly challenging. Novel ionic energetic molecules have attracted much attention in this area due to their prominent advantages including low sensitivities, high thermal stability, and excellent energy performances. Herein, five different ionic energetic molecules based on new monovalent and divalent 4-oxyl-3,5-dinitropyrazolate moieties with enhanced oxygen balance have been synthesized, characterized and evaluated as potential high-energy materials. Thermal stability, sensitivities and energy output test were measured and studied in detail. The heats of formation and energetic parameters were calculated by using Gaussian 09 suite of programs and EXPLO 5 code. The results suggest that all as-prepared new molecules exhibit good thermal stability with high decomposition temperature (3, 231°C; 5, 160°C; 6, 185°C; 7, 180°C; 8, 213°C), and relative low sensitivity (IS > 20 J, FS = 324 N). Inheriting the significant oxygen content of monovalent and divalent 4-oxyl-3,5-dinitropyrazolate moieties, they also possess good energy properties (v D = 8238 ~ 9208 m s?1, P = 26.8 ~ 36.7 GPa, V o = 481.8 ~ 959.4 L kg?1), which make them competitive high-energy materials. 相似文献
3.
Haijuan Nan Tetiana M. Stepanova Natalia V. Kondratiuk Yuanyang Nie Bo Li 《International Journal of Food Science & Technology》2022,57(8):5532-5541
The gel-forming ability of myofibrillar protein (MP) is highly correlated with the characteristics of emulsified meat products. Incorporation of Agaricus bisporus (Ab) powder into MP gels may enhance its gel properties to facilitate the development of a novel and safe meat product. Therefore, this study investigated the effects of Ab powder on gel strength, water holding capacity (WHC), texture, rheological behaviour, LF-NMR spin–spin relaxation (T2), microstructure and protein secondary structure of the MP gel system. The results indicated that the gel strength, WHC, G' value and G" value were significantly improved when the addition of Ab powder increased from 0% to 6% (P < 0.05). Meanwhile, the T2 relaxation time was shortened, and free water was transformed into immobilised water. The texture of the gel was improved when 1%–4% Ab powder was added compared to the control. Furthermore, Ab filled in the gel network and promoted the unfolding of MP α-helix and the formation of MP β-sheet during the thermal denaturation of MP, leading to a dense aggregated network structure. The study suggested that Ab could be a promising ingredient in improving chicken MP's gel properties and developing fat-reduced meat products. 相似文献
4.
结合工程实例,论述了低应变检测配合静载测试的必要性及应注意的问题,着重介绍了对缺陷桩承载力的检测过程及分析思路。 相似文献
5.
选取铜山铜矿具有代表性的铜山矿段1号矿体、前山矿段4号矿体、前山南矿段30号矿体,将地质勘探资料与回采后地质资料所确定的矿体的形态、厚度、底板位移、资源储量等参数进行对比。分析了矿体勘、采资料误差的原因,探讨了合理的生产勘探方法及勘探网度,分析并划分了合理的勘探类型,为类似矿床的勘探、开发提供借鉴。 相似文献
6.
7.
我国煤炭企业传统的“大量生产、大量消费、大量废弃”的模式,存在着许多严重问题,如环境污染、煤炭资源的产出率低、利用率低、回收率低等。长此以往,煤炭企业将面临资源枯竭、无煤可采的局面,将无法满足我国经济又好又快的发展需求。因此,煤炭企业发展循环经济是大势所趋,势在必行。文章主要分析了煤炭企业发展循环经济的必要性,并对煤炭企业发展循环经济的路径问题进行了较深入地探讨。 相似文献
8.
9.
10.