全文获取类型
收费全文 | 7926篇 |
免费 | 846篇 |
国内免费 | 497篇 |
专业分类
电工技术 | 881篇 |
综合类 | 1275篇 |
化学工业 | 328篇 |
金属工艺 | 199篇 |
机械仪表 | 440篇 |
建筑科学 | 684篇 |
矿业工程 | 139篇 |
能源动力 | 197篇 |
轻工业 | 122篇 |
水利工程 | 129篇 |
石油天然气 | 169篇 |
武器工业 | 83篇 |
无线电 | 1300篇 |
一般工业技术 | 1106篇 |
冶金工业 | 108篇 |
原子能技术 | 148篇 |
自动化技术 | 1961篇 |
出版年
2024年 | 7篇 |
2023年 | 72篇 |
2022年 | 89篇 |
2021年 | 133篇 |
2020年 | 210篇 |
2019年 | 183篇 |
2018年 | 186篇 |
2017年 | 238篇 |
2016年 | 259篇 |
2015年 | 276篇 |
2014年 | 392篇 |
2013年 | 534篇 |
2012年 | 529篇 |
2011年 | 558篇 |
2010年 | 448篇 |
2009年 | 472篇 |
2008年 | 452篇 |
2007年 | 519篇 |
2006年 | 490篇 |
2005年 | 431篇 |
2004年 | 372篇 |
2003年 | 302篇 |
2002年 | 302篇 |
2001年 | 245篇 |
2000年 | 231篇 |
1999年 | 209篇 |
1998年 | 167篇 |
1997年 | 152篇 |
1996年 | 143篇 |
1995年 | 128篇 |
1994年 | 90篇 |
1993年 | 82篇 |
1992年 | 61篇 |
1991年 | 50篇 |
1990年 | 51篇 |
1989年 | 38篇 |
1988年 | 28篇 |
1987年 | 16篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 17篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 2篇 |
排序方式: 共有9269条查询结果,搜索用时 140 毫秒
1.
Peng Li Haibin Jiang Ariel Barr Zhichu Ren Rui Gao Hua Wang Weiwei Fan Meifang Zhu Guiyin Xu Ju Li 《Advanced functional materials》2021,31(51):2105845
Mercury, lead, and cadmium are among the most toxic and carcinogenic heavy metal ions (HMIs), posing serious threats to the sustainability of aquatic ecosystems and public health. There is an urgent need to remove these ions from water by a cheap but green process. Traditional methods have insufficient removal efficiency and reusability. Structurally robust, large surface-area adsorbents functionalized with high-selectivity affinity to HMIs are attractive filter materials. Here, an adsorbent prepared by vulcanization of polyacrylonitrile (PAN), a nitrogen-rich polymer, is reported, giving rise to PAN-S nanoparticles with cyclic π-conjugated backbone and electronic conductivity. PAN-S can be coated on ultra-robust melamine (ML) foam by simple dipping and drying. In agreement with hard/soft acid/base theory, N- and S-containing soft Lewis bases have strong binding to Hg2+, Pb2+, Cu2+, and Cd2+, with extraordinary capture efficiency and performance stability. Furthermore, the used filters, when collected and electrochemically biased in a recycling bath, can release the HMIs into the bath and electrodeposit on the counter-electrode as metallic Hg0, Pb0, Cu0, and Cd0, and the PAN-S@ML filter can then be reused at least 6 times as new. The electronically conductive PAN-S@ML filter can be fabricated cheaply and holds promise for scale-up applications. 相似文献
2.
Stefano Mariani Antonino Amedeo La Mattina Alessandro Paghi Lucanos Strambini Giuseppe Barillaro 《Advanced functional materials》2021,31(26):2100774
Here, a fluoride-assisted route for the controlled in-situ synthesis of metal nanoparticles (NPs) (i.e., AgNPs, AuNPs) on polydimethylsiloxane (PDMS) is reported. The size and coverage of the NPs on the PDMS surface are modulated with time and over space during the synthetic process, leveraging the improved yield (10×) and faster kinetics (100×) of NP formation in the presence of F− ions, compared to fluoride-free approaches. This enables the maskless preparation of both linear and step gradients and patterns of NPs in 1D and 2D on the PDMS surface. As an application in flexible plasmonics/photonics, continuous and step-wise spatial modulations of the plasmonic features of PDMS slabs with 1D and 2D AgNP gradients on the surface are demonstrated. An excellent spatially resolved tuning of key optical parameters, namely, optical density from zero to 5 and extinction ratio up to 100 dB, is achieved with AgNP gradients prepared in AgF solution for 12 minutes; the performance are comparable to those of commercial dielectric/interference filters. When used as a rejection filter in optical fluorescence microscopy, the AgNP-PDMS slabs are able to reject the excitation laser at 405 nm and retain the green fluorescence of microbeads (100 µm) used as test cases. 相似文献
3.
利用模糊控制和比例积分微分(PID)控制相结合的手段对注塑机料筒温度进行了控制,同时以Matlab 6.0软件为仿真平台,对料筒温度控制进行了模拟仿真研究。实验发现,在注塑机料筒升温过程中利用CHR整定的PID控制手段和模糊控制手段,恒温过程中利用人工整定的PID控制手段,可保证快速的料筒升温响应速率和稳定的保温过程。通过实际注塑实验对该仿真结果进行了验证,在十组实验中,料筒温度误差不超过2%,产品翘曲变形量不超过0.059 mm。 相似文献
4.
The intermittent wind power in isolated hybrid distributed generation (IHDG) may cause serious problems associated with frequency (f) and power (P) fluctuation. Energy storage devices such as battery, super capacitor, and superconducting magnetic energy storage (SMES) may be used to reduce these fluctuations associated with f and P. This paper presents a study of IHDG power system for improving both f and P deviation profiles with the help of SMES. The studied IHDG power system is consisted of wind turbine generator and diesel engine generator. Both f and P control problems of the studied power system model are addressed in presence or absence of SMES. Fuzzy logic based proportional–integral–derivative (PID) controller with SMES is used for the purpose of minimization of f and P deviations. The different tunable parameters of the PID controller and those of the SMES are tuned by a novel quasi-oppositional harmony search algorithm. Performance study of the IHDG power system model is carried out under different perturbation conditions. The results demonstrate minimum f and P deviations may be achieved by using the proposed fuzzy logic based PID controller along with SMES. 相似文献
5.
According to the definition of spectral integral,a new spectral characteristic parameter,with the name Reversed Spectral Absorption Integral(RSAI),is proposed and used to retrieve the chromium content based on the Partial Least Squares Regression(PLSR) model.The contrastive study with other traditional spectral characteristic parameters,including differential transformation,inverse transformation,absorption area,etc.indicates that(1) the first derivation of square root transformed model can predict the chromium content quantitatively in terms of spectral transformations.(2) the stability of the absorption area model is slightly poor,and the chromium content of samples can only be estimated roughly.(3) However,as to the inversed spectral absorption integral model,the adjustment determination coefficient(Ad-R2) of the modeling and verification is 0.73 and 0.77,while the Root Mean Squared Error(RMSE) is 2.63 mg/kg and 2.36 mg/kg respectively with Relative Percent Deviation(RPD) being 3.21,which shows that the RSAI model has excellent prediction ability.So,the inversed spectral absorption integral new model can improve the accuracy and stability used to retrieve the chromium content,which provides a new idea for monitoring the chromium contamination in soil. 相似文献
6.
7.
We present a domain decomposition boundary integral equation method for two-dimensional partial differential equations. The overlapping Schwarz method is employed to improve the dual reciprocity boundary element method. The resulting algorithm turns out to be more accurate than a non-overlapping approach previously proposed. Some numerical results showing the improved accuracy and efficiency of the methods are given. 相似文献
8.
9.
文章通过对时差式超声波流量检测方法的分析,提出了基于过零检测技术及积分法的信号处理方法,避免了繁琐的信号处理,降低了整机功耗。结合工作时序的设计,提出了实现低功耗超声波液体流量检测的措施。 相似文献
10.
基于多相滤波器的信道化接收机及其应用研究 总被引:16,自引:0,他引:16
本文主要研究了应用多相滤波技术的信道化接收机建模问题。在给定信道频谱划分方案下,推导了基于多相 滤波器的信道化接收机数学模型。并由此模型设计了一个四信道模拟系统。最后用仿真实验结果验证了模型的正确性。 相似文献