全文获取类型
收费全文 | 133288篇 |
免费 | 18526篇 |
国内免费 | 3318篇 |
专业分类
电工技术 | 4540篇 |
技术理论 | 1篇 |
综合类 | 4003篇 |
化学工业 | 33710篇 |
金属工艺 | 5268篇 |
机械仪表 | 7117篇 |
建筑科学 | 6183篇 |
矿业工程 | 1338篇 |
能源动力 | 3965篇 |
轻工业 | 15588篇 |
水利工程 | 1681篇 |
石油天然气 | 2138篇 |
武器工业 | 466篇 |
无线电 | 18729篇 |
一般工业技术 | 25592篇 |
冶金工业 | 6355篇 |
原子能技术 | 1296篇 |
自动化技术 | 17162篇 |
出版年
2024年 | 327篇 |
2023年 | 1360篇 |
2022年 | 2445篇 |
2021年 | 3690篇 |
2020年 | 3821篇 |
2019年 | 5166篇 |
2018年 | 5612篇 |
2017年 | 5933篇 |
2016年 | 6609篇 |
2015年 | 6837篇 |
2014年 | 8027篇 |
2013年 | 10769篇 |
2012年 | 9323篇 |
2011年 | 10104篇 |
2010年 | 8931篇 |
2009年 | 8875篇 |
2008年 | 8161篇 |
2007年 | 7211篇 |
2006年 | 6607篇 |
2005年 | 5498篇 |
2004年 | 4623篇 |
2003年 | 4074篇 |
2002年 | 3789篇 |
2001年 | 3241篇 |
2000年 | 2820篇 |
1999年 | 1988篇 |
1998年 | 1983篇 |
1997年 | 1348篇 |
1996年 | 1101篇 |
1995年 | 788篇 |
1994年 | 658篇 |
1993年 | 564篇 |
1992年 | 418篇 |
1991年 | 382篇 |
1990年 | 333篇 |
1989年 | 302篇 |
1988年 | 252篇 |
1987年 | 210篇 |
1986年 | 154篇 |
1985年 | 131篇 |
1984年 | 105篇 |
1983年 | 76篇 |
1982年 | 54篇 |
1981年 | 44篇 |
1980年 | 41篇 |
1979年 | 43篇 |
1978年 | 40篇 |
1977年 | 49篇 |
1976年 | 75篇 |
1975年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
6‐Mercaptopurine‐Induced Fluorescence Quenching of Monolayer MoS2 Nanodots: Applications to Glutathione Sensing,Cellular Imaging,and Glutathione‐Stimulated Drug Delivery 下载免费PDF全文
Shih‐Chiang Chen Chang‐Yu Lin Tian‐Lu Cheng Wei‐Lung Tseng 《Advanced functional materials》2017,27(41)
Molybdenum disulfide (MoS2) nanodots (NDs) with sulfur vacancies have been demonstrated to be suitable to conjugate thiolated molecules. However, thiol‐induced fluorescence quenching of MoS2 NDs has been rarely explored. In this study, 6‐mercaptopurine (6‐MP) serves as an efficient quencher for the fluorescence of monolayer MoS2 (M‐MoS2) NDs. 6‐MP molecules are chemically adsorbed at the sulfur vacancy sites of the M‐MoS2 NDs. The formed complexes trigger the efficient fluorescence quenching of the M‐MoS2 NDs due to acceptor‐excited photoinduced electron transfer. The presence of glutathione (GSH) efficiently triggers the release of 6‐MP from the M‐MoS2 NDs, thereby switching on the fluorescence of the M‐MoS2 NDs. Thus, the 6‐MP‐M‐MoS2 NDs are implemented as a platform for the sensitive and selective detection of GSH in erythrocytes and live cells. Additionally, thiolated doxorubicin (DOX‐SH)‐loaded M‐MoS2 NDs (DOX‐SH/M‐MoS2 NDs) serve as GSH‐responsive nanocarriers for DOX‐SH delivery. In vitro studies reveal that the DOX‐SH/M‐MoS2 NDs exhibit efficient uptake by HeLa cells and greater cytotoxicity than free DOX‐SH and DOX. In vivo study shows that GSH is capable of triggering the release of DOX‐SH from M‐MoS2 ND‐based nanomaterials in mice. It is revealed that the DOX‐SH/M‐MoS2 NDs can be implemented for simultaneous drug delivery and fluorescence imaging. 相似文献
992.
A 3D Hybrid of Chemically Coupled Nickel Sulfide and Hollow Carbon Spheres for High Performance Lithium–Sulfur Batteries 下载免费PDF全文
Chao Ye Lei Zhang Chunxian Guo Dongdong Li Anthony Vasileff Haihui Wang Shi‐Zhang Qiao 《Advanced functional materials》2017,27(33)
Lithium–sulfur batteries are a promising next‐generation energy storage device owing to their high theoretical capacity and the low cost and abundance of sulfur. However, the low conductivity and loss of active sulfur material during operation greatly limit the rating capabilities and cycling stability of lithium–sulfur batteries. In this work, a unique sulfur host hybrid material comprising nanosized nickel sulfide (NiS) uniformly distributed on 3D carbon hollow spheres (C‐HS) is fabricated using an in situ thermal reduction and sulfidation method. In the hybrid material, the nanosized NiS provides a high adsorption capability for polysulfides and the C‐HS serves as a physical confinement for polysulfides and also a 3D electron transfer pathway. Moreover, NiS has strong chemical coupling with the C‐HS, favoring fast charge transfer and redox kinetics of the sulfur electrode. With a sulfur loading of up to 2.3 mg cm?2, the hybrid material‐based lithium–sulfur batteries offer a capacity decay as low as 0.013% per cycle and a capacity of 695 mA h g?1 at 0.5 C after 300 cycles. This unique 3D hybrid material with strong chemical coupling provides a promising sulfur host for high performance lithium–sulfur batteries. 相似文献
993.
Unusual Twisting Phonons and Breathing Modes in Tube‐Terminated Phosphorene Nanoribbons and Their Effects on Thermal Conductivity 下载免费PDF全文
By studying tube‐terminated phosphorene nanoribbons (PNRs), it is found that unusual phonon and thermal properties can emerge from topologically new edges. The lattice dynamics calculations show that in tube‐terminated PNRs, the breaking of rotation symmetry suppresses the degeneracy of phonon modes, causing the emergence of twisting mode. An anomalous change of an out‐of‐plane acoustic mode to breathing modes with nonzero energy at the center of Brillouin zone occurs when the phosphorene sheet is converted into a tube‐terminated PNR. These unusual twisting and breathing modes provide a larger phase space for scattering phonons, thus explaining the low thermal conductivity of tube‐terminated PNRs revealed by molecular dynamics calculations. Due to the change in the stress field distribution caused by the tube edge, a nearly strain‐independent thermal conductivity in tube‐terminated PNRs is observed, which is in contrast to the apparent enhancement of thermal conductivity in pristine and dimer‐terminated PNRs under tensile strain. The work reveals intriguing phononic and thermal behaviors of tube‐terminated 2D materials. 相似文献
994.
Low‐Power Nonvolatile Charge Storage Memory Based on MoS2 and an Ultrathin Polymer Tunneling Dielectric 下载免费PDF全文
Myung Hun Woo Byung Chul Jang Junhwan Choi Khang June Lee Gwang Hyuk Shin Hyejeong Seong Sung Gap Im Sung‐Yool Choi 《Advanced functional materials》2017,27(43)
Low‐power, nonvolatile memory is an essential electronic component to store and process the unprecedented data flood arising from the oncoming Internet of Things era. Molybdenum disulfide (MoS2) is a 2D material that is increasingly regarded as a promising semiconductor material in electronic device applications because of its unique physical characteristics. However, dielectric formation of an ultrathin low‐k tunneling on the dangling bond‐free surface of MoS2 is a challenging task. Here, MoS2‐based low‐power nonvolatile charge storage memory devices are reported with a poly(1,3,5‐trimethyl‐1,3,5‐trivinyl cyclotrisiloxane) (pV3D3) tunneling dielectric layer formed via a solvent‐free initiated chemical vapor deposition (iCVD) process. The surface‐growing polymerization and low‐temperature nature of the iCVD process enable the conformal growing of low‐k (≈2.2) pV3D3 insulating films on MoS2. The fabricated memory devices exhibit a tunable memory window with high on/off ratio (≈106), excellent retention times of 105 s with an extrapolated time of possibly years, and an excellent cycling endurance of more than 103 cycles, which are much higher than those reported previously for MoS2‐based memory devices. By leveraging the inherent flexibility of both MoS2 and polymer dielectric films, this research presents an important milestone in the development of low‐power flexible nonvolatile memory devices. 相似文献
995.
Grace G. D. Han Kun‐Hua Tu Farnaz Niroui Wenshuo Xu Si Zhou Xiaochen Wang Vladimir Bulović Caroline A. Ross Jamie H. Warner Jeffrey C. Grossman 《Advanced functional materials》2017,27(45)
Monolayer 2D MoS2 grown by chemical vapor deposition is nanopatterned into nanodots, nanorods, and hexagonal nanomesh using block copolymer (BCP) lithography. The detailed atomic structure and nanoscale geometry of the nanopatterned MoS2 show features down to 4 nm with nonfaceted etching profiles defined by the BCP mask. Atomic resolution annular dark field scanning transmission electron microscopy reveals the nanopatterned MoS2 has minimal large‐scale crystalline defects and enables the edge density to be measured for each nanoscale pattern geometry. Photoluminescence spectroscopy of nanodots, nanorods, and nanomesh areas shows strain‐dependent spectral shifts up to 15 nm, as well as reduction in the PL efficiency as the edge density increases. Raman spectroscopy shows mode stiffening, confirming the release of strain when it is nanopatterned by BCP lithography. These results show that small nanodots (≈19 nm) of MoS2 2D monolayers still exhibit strong direct band gap photoluminescence (PL), but have PL quenching compared to pristine material from the edge states. This information provides important insights into the structure–PL property correlations of sub‐20 nm MoS2 structures that have potential in future applications of 2D electronics, optoelectronics, and photonics. 相似文献
996.
Using Bulk Heterojunctions and Selective Electron Trapping to Enhance the Responsivity of Perovskite–Graphene Photodetectors 下载免费PDF全文
Liang Qin Liping Wu Bhupal Kattel Chunhai Li Yong Zhang Yanbing Hou Judy Wu Wai‐Lun Chan 《Advanced functional materials》2017,27(47)
Graphene field effect transistor sensitized by a layer of semiconductor (sensitizer/GFET) is a device structure that is investigated extensively for ultrasensitive photodetection. Among others, organometallic perovskite semiconductor sensitizer has the advantages of long carrier lifetime and solution processable. A further step to improve the responsivity is to design a structure that can promote electron–hole separation and selective carrier trapping in the sensitizer. Here, the use of a hybrid perovskite–organic bulk heterojunction (BHJ) as the light sensitizer to achieve this goal is demonstrated. Our spectroscopy and device measurements show that the CH3NH3PbI3–PCBM BHJ/GFET device has improved charge separation yield and carrier lifetime as compared to a reference device with a CH3NH3PbI3 sensitizer only. The key to these enhancement is the presence of [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM), which acts as charge separation and electron trapping sites, resulting in a 30‐fold increase in the photoresponsivity. This work shows that the use of a small amount of electron or hole acceptors in the sensitizer layer can be an effective strategy for improving and tuning the photoresponsivity of sensitizer/GFET photodetectors. 相似文献
997.
Facile Two‐Step Synthesis of All‐Inorganic Perovskite CsPbX3 (X = Cl,Br, and I) Zeolite‐Y Composite Phosphors for Potential Backlight Display Application 下载免费PDF全文
Jia‐Yi Sun Freddy T. Rabouw Xian‐Feng Yang Xie‐Yi Huang Xi‐Ping Jing Shi Ye Qin‐Yuan Zhang 《Advanced functional materials》2017,27(45)
Recently developed CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (QDs) hold great potential for various applications owing to their superior optical properties, such as tunable emissions, high quantum efficiency, and narrow linewidths. However, poor stability under ambient conditions and spontaneous ion exchange among QDs hinder their application, for example, as phosphors in white‐light‐emitting diodes (WLEDs). Here, a facile two‐step synthesis procedure is reported for luminescent and color‐tunable CsPbX3–zeolite‐Y composite phosphors, where perovskite QDs are encapsulated in the porous zeolite matrix. First zeolite‐Y is infused with Cs+ ions by ion exchange from an aqueous solution and then forms CsPbX3 QDs by diffusion and reaction with an organic solution of PbX2. The zeolite encapsulation reduces degradation and improves the stability of the QDs under strong illumination. A WLED is fabricated using the resulting microscale composites, with Commission Internationale de I'Eclairage (CIE) color coordinates (0.38, 0.37) and achieving 114% of National Television Standards Committee (NTSC) and 85% of the ITU‐R Recommendation BT.2020 (Rec.2020) coverage. 相似文献
998.
999.
1000.
Kamel Benachenhou Mhamed Hamadouche Abdelmalik Taleb‐Ahmed 《International Journal of Satellite Communications and Networking》2017,35(3):215-230
This paper deals with the analysis of the acquisition process performed by a global navigation satellite system (GNSS) receiver with a pilot and data channel or in case of GNSS hybrid receiver. Signal acquisition decides the presence or absence of GNSS signal by comparing signal under test with a fixed threshold and provides a code delay and a Doppler frequency estimation, but in low signal conditions or in a noisy environment; acquisition systems are vulnerable and can give a high false alarm and low detection probability. Firstly, we introduce a cell‐averaging‐constant false alarm rate (CFAR) then a data‐pilot cell‐averaging‐CFAR detector fusion based to deal with these situations. In this context, we use a new mathematical derivation to develop a closed‐form analytic expressions for the probabilities of detection and false alarm. The performances of the proposed detector are evaluated and compared with a non‐CFAR case through an analytical and numerical results validated by Mont Carlo simulations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献