全文获取类型
收费全文 | 5353篇 |
免费 | 759篇 |
国内免费 | 474篇 |
专业分类
电工技术 | 216篇 |
技术理论 | 1篇 |
综合类 | 159篇 |
化学工业 | 992篇 |
金属工艺 | 192篇 |
机械仪表 | 155篇 |
建筑科学 | 130篇 |
矿业工程 | 7篇 |
能源动力 | 383篇 |
轻工业 | 104篇 |
水利工程 | 59篇 |
石油天然气 | 34篇 |
武器工业 | 10篇 |
无线电 | 1074篇 |
一般工业技术 | 969篇 |
冶金工业 | 41篇 |
原子能技术 | 180篇 |
自动化技术 | 1880篇 |
出版年
2024年 | 4篇 |
2023年 | 166篇 |
2022年 | 140篇 |
2021年 | 194篇 |
2020年 | 205篇 |
2019年 | 128篇 |
2018年 | 112篇 |
2017年 | 123篇 |
2016年 | 153篇 |
2015年 | 138篇 |
2014年 | 301篇 |
2013年 | 359篇 |
2012年 | 559篇 |
2011年 | 611篇 |
2010年 | 462篇 |
2009年 | 574篇 |
2008年 | 415篇 |
2007年 | 528篇 |
2006年 | 482篇 |
2005年 | 208篇 |
2004年 | 97篇 |
2003年 | 77篇 |
2002年 | 88篇 |
2001年 | 82篇 |
2000年 | 85篇 |
1999年 | 83篇 |
1998年 | 56篇 |
1997年 | 47篇 |
1996年 | 32篇 |
1995年 | 16篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1986年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有6586条查询结果,搜索用时 31 毫秒
1.
Bone related diseases have caused serious threats to human health owing to their complexity and specificity. Fortunately, owing to the unique 3D network structure with high aqueous content and functional properties, emerging hydrogels are regarded as one of the most promising candidates for bone tissue engineering, such as repairing cartilage injury, skull defect, and arthritis. Herein, various design strategies and synthesis methods (e.g., 3D-printing technology and nanoparticle composite strategy) are introduced to prepare implanted hydrogel scaffolds with tunable mechanical strength, favorable biocompatibility, and excellent bioactivity for applying in bone regeneration. Injectable hydrogels based on biocompatible materials (e.g., collagen, hyaluronic acid, chitosan, polyethylene glycol, etc.) possess many advantages in minimally invasive surgery, including adjustable physicochemical properties, filling irregular shapes of defect sites, and on-demand release drugs or growth factors in response to different stimuli (e.g., pH, temperature, redox, enzyme, light, magnetic, etc.). In addition, drug delivery systems based on micro/nanogels are discussed, and its numerous promising designs used in the application of bone diseases (e.g., rheumatoid arthritis, osteoarthritis, cartilage defect) are also briefed in this review. Particularly, several key factors of hydrogel scaffolds (e.g., mechanical property, pore size, and release behavior of active factors) that can induce bone tissue regeneration are also summarized in this review. It is anticipated that advanced approaches and innovative ideas of bioactive hydrogels will be exploited in the clinical field and increase the life quality of patients with the bone injury. 相似文献
2.
Nianxiu Duan Junjun Li Sha Song Feng Wang Yiwei Yang Di Nie Caifen Wang Yingjie Sheng Yali Tao Jie Gao Can Xu Yan Wei Yong Gan 《Advanced functional materials》2021,31(46):2100605
Tumor-specific enhanced delivery of chemotherapeutics and modulators to tumor cells and activated pancreatic stellate cells (aPSCs), respectively, represents safer and more effective therapy for pancreatic cancer. Herein, a membrane type 1-matrix metalloproteinase (MT1-MMP)-cleavable spacer is used to assemble low-density cRGDfK onto thermosensitive liposomes loaded with phosphorylated calcipotriol (PCAL) and doxorubicin (DOX), yielding MR-T-PD. The liposome-linked cRGDfK prodrug on MR-T-PD surface is first activated by MT1-MMP, which is selectively expressed on tumor endothelial cells, to release cRGDfK. The free cRGDfK specifically promotes tumor angiogenesis, leading to 3.4-fold higher accumulation and a wider distribution of MR-T-PD in tumors. Furthermore, MR-T-PD rapidly releases PCAL and DOX into the interstitium under heat treatment. The released DOX enters tumor cells to induce apoptosis, whereas the PCAL prodrug is converted to CAL by alkaline phosphatase on the surface of aPSCs; CAL can then enter aPSCs to induce quiescence and promote the antitumor effect of DOX. Finally, by enhancing the exposure of DOX and CAL to tumor cells and aPSCs, respectively, in a tumor-specific manner, MR-T-PD exerts superior efficacy (a 5.9-fold decrease in tumor weight) without causing additional side effects. Overall, this prodrug-based smart liposome system represents a promising paradigm for pancreatic cancer therapy. 相似文献
3.
MiE is a facial involuntary reaction that reflects the real emotion and thoughts of a human being. It is very difficult for a normal human to detect a Micro-Expression (MiE), since it is a very fast and local face reaction with low intensity. As a consequence, it is a challenging task for researchers to build an automatic system for MiE recognition. Previous works for MiE recognition have attempted to use the whole face, yet a facial MiE appears in a small region of the face, which makes the extraction of relevant features a hard task. In this paper, we propose a novel deep learning approach that leverages the locality aspect of MiEs by learning spatio-temporal features from local facial regions using a composite architecture of Convolutional Neural Network (CNN) and Long Short Term Memory (LSTM). The proposed solution succeeds to extract relevant local features for MiEs recognition. Experimental results on benchmark datasets demonstrate the highest recognition accuracy of our solution with respect to state-of-the-art methods. 相似文献
4.
《Ceramics International》2022,48(14):19971-19977
Molybdenum diboride is unique among transition metal diborides because it exists in both hexagonal (AlB2-type) and rhombohedral structures. However, it is difficult to stabilize the superconducting AlB2-type phase, which requires either extreme synthesis condition or suitable chemical doping. Here we report the structural and physical properties of Sc-doped nonstoichiometric molybdenum diborides (Mo0.95Sc0.05)1-xB2 and (Mo1-yScy)0.71B2 prepared by the common arc melting method. The AlB2-type phase is found to form over wide ranges of 0 ≤ x ≤ 0.29 and 0.025 ≤ y ≤ 0.30 for the first time, and bulk superconductivity with Tc up to 7.9 K is observed. Tc increases with increasing x in the (Mo0.95Sc0.05)1-xB2 series, but evolves nonmonotonically with varying y in the (Mo1-yScy)0.71B2 series. Despite this contrast, Tc of both borides follows nearly the same linear dependence on the electron-phonon coupling constant, suggesting that it is mainly controlled by the electron-phonon interaction. In addition, the stabilization of AlB2-type structure is attributed to the decrease in the number of d electrons as a consequence of Sc doping, which suggests that a similar effect may be achieved by substituting Mo with other d electron-poorer metal elements. 相似文献
5.
《Ceramics International》2022,48(15):21663-21670
In this study, two series of GaxSb40-xS60 (x = 4, 6, 8, 10 mol%) and GaySb36S64-y (y = 3, 5, 6 mol%) glasses were prepared and the relationship between their compositional and acousto-optic (AO) properties was investigated systematically for the first time. In the GaySb36S64-y system, the AO figure of merit (M2) increased as the Ga increased, and the maximum M2 of the Ga6Sb36S58 glass was 455.78 × 10?18 s3/g, which is ~301 times greater than that of fused silica and ~2.5 times greater than that of As2S3 chalcogenide (ChG) glass at 1550 nm. However, its thermo-optic coefficients (dn/dT) varied greatly (32.1 × 10?6 °C?1–57.2 × 10?6 °C?1), and acoustic attenuations (α) at 10 MHz were high, from 5.446 dB/cm to 7.274 dB/cm. In the GaxSb40-xS60 glass system, the M2 value and α at different ultrasonic frequencies gradually decreased with the improvement of Ga. Compared with the GaySb36S64-y system, the GaxSb40-xS60 glass system had lower α (at 10 MHz) and dn/dT, which are 5.001 dB/cm–5.563 dB/cm and 17.3 × 10?6 °C?1–55.6 × 10?6 °C?1, respectively. These results provide a significant reference for the further development of novel ChG glasses and help expand their application fields. 相似文献
6.
Yusong Tu Pei Li Jiajia Sun Jie Jiang Fangfang Dai Chengzhang Li Yuanyan Wu Liang Chen Guosheng Shi Yanwen Tan Haiping Fang 《Advanced functional materials》2021,31(13):2008018
Despite long-term efforts for exploring antibacterial agents or drugs, potentiating antibacterial activity and meanwhile minimizing toxicity to the environment remains a challenge. Here, it is experimentally shown that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity that is significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two-orders-of-magnitude greater than the activity of its surrounding copper ions. It is demonstrated that rGO is functionalized through the cation–π interaction to massively adsorb copper ions to form a rGO–copper composite and result in an extremely low concentration level of surrounding copper ions (less than ≈0.5 µm ). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu2+ into Cu+, which greatly enhances the antibacterial activity. Notably, this rGO functionality through cation–π interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells. 相似文献
7.
The development of traditional urbanisation has generated environmental problems, so the Chinese Government has proposed a new-type of urbanisation path with uniquely Chinese characteristics. How does this new-type of urbanisation affect CO2 emissions? Based on panel data from 29 provinces in China (2005 to 2016), we apply an exploratory spatial data analysis model, a spatial econometric model, and a threshold model to analyse the spatial autocorrelation of CO2 emissions, the direct and indirect effects of new-type urbanisation on CO2 emissions, and the threshold characteristics produced by technological progress, respectively. The key results are: (1) CO2 emissions show significant positive autocorrelation in China, and the spatial distribution of CO2 emissions is HH (High-High) or LL (Low-Low) clustered in most provinces; (2) new-type urbanisation has a paradoxical effect on CO2 emissions. Energy-saving technology has a rebound effect on CO2 emissions, but environmental technology inhibits CO2 emissions; (3) by eliminating the rebound effect of energy-saving technology on CO2 emissions and promoting environmental technology, new-type urbanisation indirectly inhibits CO2 emissions; (4) new-type urbanisation exhibits a threshold effect on CO2 emissions due to the different levels of energy-saving technology and environmental technology. Finally, policy recommendations for CO2 emissions reduction are proposed from the perspective of new-type urbanisation, energy-saving technology, and environmental technology. 相似文献
8.
《Ceramics International》2020,46(13):21343-21350
The transition metal sulfides have gained extensive interest in energy storage devices owing to their unique features. However, the research-based on cobalt, copper and manganese sulfide composites is limited while they are considered as promising contenders for supercapacitor electrodes. The simplest and facile one-step electrodeposition technique was adopted for the direct growth of CuMnS and CoMnS on a Ni-substrate. The electrochemical properties of CuMnS and CoMnS electrodes were investigated and maximum specific capacitances of 1691 and 2290 F/g, respectively, were obtained at 10 A/g current density. Further, these electrodes are investigated with activated carbon (AC) electrode to fabricate asymmetric supercapacitor devices where CoMnS//AC exhibited superior energy density values than CuMnS//AC device. However, both the devices show a relatively uniform capacitance retention rate (~94%) after 2500 charging-discharging cycles. Furthermore, the role of capacitive- and diffusive-controlled contributions in the charge storage phenomenon of supercapacitor devices are explicitly scrutinized by employing Dunn's model. Co-electrodeposition of transition metal sulfides has great potential as electrode material for highly effective supercapacitor devices. 相似文献
9.
采用近红外光谱法对转基因油/非转基因油的混合溶液进行研究。对采集到的原始光谱分别进行多元散射校正(MSC)、一阶导数(FD)、移动窗口平滑(MWS)、Savitzky-Golay平滑一阶导数(SG1)预处理。研究比较了不同预处理方法对转基因油/非转基因油支持向量机(SVM)建模判别分析的影响,其中MSC预处理后的模型预测效果最好,准确率为91.6%。为了进一步提高模型的精度与稳定性,采用连续投影算法(SPA)对全波长进行特征波长筛选。利用筛选后的15个特征波长输入到SVM中,预测准确率提高到98.3%。实验结果表明,采用近红外光谱法,可以实现对转基因油/非转基因油快速检测,不仅适用于纯转基因油的鉴别,也适用于非转基因油中掺入转基因油的鉴别。 相似文献
10.
《Ceramics International》2020,46(6):7388-7395
In this study, the effect of ZnO seed layer on the growth of uniform CdS nanostructures was investigated using chemical bath deposition technique. Besides, the influence of molar concentration of reagents on the surface morphology, structural and optoelectrical properties of the deposited CdS thin films were examined. The CdS nanostructures were grown on bare glass and ZnO/glass substrates with different reagent molar concentrations. The results indicated an improvement in the homogeneity and uniformity of the grown CdS nanostructures on ZnO seed layer which can be due to the low lattice mismatch between ZnO and CdS structures. The CdS/ZnO samples were optimized by changing the molar concentration of reagents. A three–dimensional intersecting vertical nanosheet morphology with hexagonal structure was obtained when modified chemical concentration of 0.5 M was applied. The XRD pattern of CdS nanosheets indicated the hexagonal phase of CdS which were strongly orientated along (002) plane. The elevated intensity of dominant peak related to this sample confirmed the improved crystal quality of this CdS nanostructure comparing to the other samples. The UV–Vis spectrum demonstrated a high absorption coefficient for CdS intersecting nanosheets which might be due to the high specific surface area and light trapping behavior of this sample. The photoluminescence study also showed an improvement in optical properties of optimized CdS nanostructures. In order to study the optoelectrical properties of CdS nanostructures, metal–semiconductor–metal photodetectors were fabricated with different CdS samples and their current–voltage characteristics were analyzed. The results indicated an enhancement in photosensitivity, responsivity, and speed of photodetectors based on optimized CdS nanostructures. 相似文献