全文获取类型
收费全文 | 206677篇 |
免费 | 25995篇 |
国内免费 | 5819篇 |
专业分类
电工技术 | 9723篇 |
技术理论 | 11篇 |
综合类 | 8799篇 |
化学工业 | 43745篇 |
金属工艺 | 10486篇 |
机械仪表 | 11106篇 |
建筑科学 | 11608篇 |
矿业工程 | 4004篇 |
能源动力 | 4723篇 |
轻工业 | 16492篇 |
水利工程 | 3469篇 |
石油天然气 | 9641篇 |
武器工业 | 1053篇 |
无线电 | 24713篇 |
一般工业技术 | 37964篇 |
冶金工业 | 11899篇 |
原子能技术 | 5048篇 |
自动化技术 | 24007篇 |
出版年
2024年 | 2012篇 |
2023年 | 2823篇 |
2022年 | 4881篇 |
2021年 | 6807篇 |
2020年 | 6889篇 |
2019年 | 6971篇 |
2018年 | 8062篇 |
2017年 | 8798篇 |
2016年 | 8847篇 |
2015年 | 9386篇 |
2014年 | 10969篇 |
2013年 | 13655篇 |
2012年 | 12087篇 |
2011年 | 12513篇 |
2010年 | 11226篇 |
2009年 | 10976篇 |
2008年 | 10403篇 |
2007年 | 9799篇 |
2006年 | 8942篇 |
2005年 | 7611篇 |
2004年 | 6093篇 |
2003年 | 5990篇 |
2002年 | 6002篇 |
2001年 | 5410篇 |
2000年 | 4809篇 |
1999年 | 3777篇 |
1998年 | 2776篇 |
1997年 | 2315篇 |
1996年 | 2041篇 |
1995年 | 1770篇 |
1994年 | 1513篇 |
1993年 | 1278篇 |
1992年 | 1251篇 |
1991年 | 1113篇 |
1990年 | 1117篇 |
1989年 | 1029篇 |
1988年 | 910篇 |
1987年 | 853篇 |
1986年 | 783篇 |
1985年 | 731篇 |
1984年 | 719篇 |
1981年 | 681篇 |
1979年 | 744篇 |
1978年 | 783篇 |
1977年 | 747篇 |
1976年 | 761篇 |
1975年 | 718篇 |
1974年 | 721篇 |
1973年 | 729篇 |
1972年 | 707篇 |
排序方式: 共有10000条查询结果,搜索用时 15 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.
Huai‐Ning Wu Xiao‐Wei Zhang 《International Journal of Adaptive Control and Signal Processing》2019,33(10):1552-1566
This paper studies an enhanced state estimation problem of distributed parameter processes modeled by a linear parabolic partial differential equation using mobile sensors. The proposed estimation scheme contains a state estimator and the guidance of mobile sensors, where the spatial domain is decomposed into multiple subdomains according to the number of sensors and each sensor is capable of moving within the respective subdomain. The state estimator is desired to make the state estimation error system exponentially stable while providing an performance bound. The mobile sensor guidance is used to enhance the transient performance of the error system. By the Lyapunov direct technique, an integrated design of state estimator and mobile sensor guidance laws is developed in the form of bilinear matrix inequalities (BMIs) to meet the desired design objectives. Moreover, to make the performance bound as small as possible, a suboptimal enhanced state estimation problem is formulated as a BMI optimization one, which can be solved via an iterative linear matrix inequality algorithm. Finally, numerical simulations are given to show the effectiveness of the proposed method. 相似文献
3.
4.
q-Rung orthopair fuzzy sets (q-ROFSs), originally presented by Yager, are a powerful fuzzy information representation model, which generalize the classical intuitionistic fuzzy sets and Pythagorean fuzzy sets and provide more freedom and choice for decision makers (DMs) by allowing the sum of the power of the membership and the power of the nonmembership to be less than or equal to 1. In this paper, a new class of fuzzy sets called q-rung orthopair uncertain linguistic sets (q-ROULSs) based on the q-ROFSs and uncertain linguistic variables (ULVs) is proposed, and this can describe the qualitative assessment of DMs and provide them more freedom in reflecting their belief about allowable membership grades. On the basis of the proposed operational rules and comparison method of q-ROULSs, several q-rung orthopair uncertain linguistic aggregation operators are developed, including the q-rung orthopair uncertain linguistic weighted arithmetic average operator, the q-rung orthopair uncertain linguistic ordered weighted average operator, the q-rung orthopair uncertain linguistic hybrid weighted average operator, the q-rung orthopair uncertain linguistic weighted geometric average operator, the q-rung orthopair uncertain linguistic ordered weighted geometric operator, and the q-rung orthopair uncertain linguistic hybrid weighted geometric operator. Then, some desirable properties and special cases of these new operators are also investigated and studied, in particular, some existing intuitionistic fuzzy aggregation operators and Pythagorean fuzzy aggregation operators are proved to be special cases of these new operators. Furthermore, based on these proposed operators, we develop an approach to solve the multiple attribute group decision making problems, in which the evaluation information is expressed as q-rung orthopair ULVs. Finally, we provide several examples to illustrate the specific decision-making steps and explain the validity and feasibility of two methods by comparing with other methods. 相似文献
5.
Gongshuo Yu Xuesong Li Tao Bai Xiaobing He Jinlong Fan Jianbo Shang 《Journal of Nuclear Science and Technology》2020,57(5):599-606
ABSTRACTIn view of the complexity of current detection efficiency calibration of radioactive gas sources, a method using solid planar sources to be equivalent to gas sources was studied. For the 50 mL gas source box, an optimal equivalent scheme was selected by Monte Carlo Simulations. Then, the full-energy-peak efficiency curve of gas sources at the measurement position of 25 cm, with source-to-detector distance of 25 cm, was fitted by measuring solid planar sources with known activity. To verify the accuracy of the efficiency curve, 41Ar, 133Xe and 87Kr gases were produced and determined by length-compensated method. Then, their full-energy-peak efficiencies at 25 cm position away from the detector were directly calibrated. The percentage efficiency deviations between interpolation from the efficiency curve and direct calibration are all less than 2.5%, which proves the accuracy of the equivalent method. This calibration method is a general one and can be also used for some other radioactive sample measurements, such as non-destructive analysis of gaseous fission product samples with a suitable source-to-detector distance. 相似文献
6.
本研究采用低真空室温射频等离子体对解淀粉芽胞杆菌CICC 10035进行预处理,通过改变放电功率、处理时间和工作气压等参数,筛选最佳工艺条件,并使用蛋白质组学技术,对差异蛋白质进行生物信息学分析,探讨等离子体预处理对菌体生长和产酶性能的影响。结果表明,等离子体预处理的最佳工艺条件为:放电功率120 W,处理时间15 s,工作气压135 Pa。在最佳条件下,发酵48 h后,α-淀粉酶酶活超过400 U/mL,与对照样相比提高约20%。蛋白组学分析表明,等离子体预处理对菌体的蛋白合成及代谢产生了较强的正效应,尤其在DNA修复和氨基酸合成上,一方面提高了菌体活性,延缓其衰亡过程;另一方面促进了α-淀粉酶在菌体内的合成和分泌。 相似文献
7.
分析了锯齿式接链环结构的不合理性和其换代产品弧齿式接链环结构的合理性,并对两者的技术性能、使用寿命等进行了比较分析,认为弧齿式接链环具有较高的破断强度和疲劳强度,是目前井下使用的接链环更新换代的最佳产品。 相似文献
8.
9.
10.