首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   109722篇
  免费   11156篇
  国内免费   6525篇
电工技术   7676篇
技术理论   6篇
综合类   9436篇
化学工业   16664篇
金属工艺   7100篇
机械仪表   7199篇
建筑科学   8173篇
矿业工程   4423篇
能源动力   3236篇
轻工业   9515篇
水利工程   2872篇
石油天然气   6358篇
武器工业   1146篇
无线电   11499篇
一般工业技术   10972篇
冶金工业   5181篇
原子能技术   1620篇
自动化技术   14327篇
  2024年   555篇
  2023年   1869篇
  2022年   3814篇
  2021年   4982篇
  2020年   3622篇
  2019年   2970篇
  2018年   3199篇
  2017年   3650篇
  2016年   3175篇
  2015年   4557篇
  2014年   5797篇
  2013年   6826篇
  2012年   7639篇
  2011年   8120篇
  2010年   7660篇
  2009年   7062篇
  2008年   7219篇
  2007年   7253篇
  2006年   6392篇
  2005年   5245篇
  2004年   3869篇
  2003年   3364篇
  2002年   3588篇
  2001年   3053篇
  2000年   2479篇
  1999年   2007篇
  1998年   1327篇
  1997年   1114篇
  1996年   1156篇
  1995年   887篇
  1994年   663篇
  1993年   506篇
  1992年   387篇
  1991年   297篇
  1990年   243篇
  1989年   187篇
  1988年   172篇
  1987年   109篇
  1986年   81篇
  1985年   41篇
  1984年   48篇
  1983年   39篇
  1982年   36篇
  1981年   37篇
  1980年   38篇
  1979年   14篇
  1976年   5篇
  1965年   6篇
  1959年   13篇
  1951年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
With the emergence of large-scale knowledge base, how to use triple information to generate natural questions is a key technology in question answering systems. The traditional way of generating questions require a lot of manual intervention and produce lots of noise. To solve these problems, we propose a joint model based on semi-automated model and End-to-End neural network to automatically generate questions. The semi-automated model can generate question templates and real questions combining the knowledge base and center graph. The End-to-End neural network directly sends the knowledge base and real questions to BiLSTM network. Meanwhile, the attention mechanism is utilized in the decoding layer, which makes the triples and generated questions more relevant. Finally, the experimental results on SimpleQuestions demonstrate the effectiveness of the proposed approach.  相似文献   
22.
23.
Networks and Spatial Economics - The relationship between shipping accessibility and maritime transport demand is studied based on the relationship between production and consumption and stochastic...  相似文献   
24.
Amphotericin B (AMB) was often used in intra-articular injection administration for fungal arthritis, because it could often bring a satisfactory therapeutic efficacy and a minimum systemic toxic side effect. However, because of the multiple operations and the frequent injections, the compliance of the patients was bad. Therefore, to develop a long-term sustained-released preparation of AMB for mycotic arthritis intra-articular administration is of great significance. The purpose of present study was to develop a long-term sustained-released in situ gel of a water-insoluble drug AMB for mycotic arthritis intra-articular administration. Based on the evaluations of the in vitro properties of the formulations, the formulation containing 10% (w/w) ethanol, 15% (w/w) PG, 0.75% (w/w) HA, 5% (w/w) purified soybean oil, 0.03% (w/w) α-tocopherol, 15% (w/w) water and 55% (w/w) glyceryl monooleate was selected as a suitable intra-articular injectable in situ gel drug delivery system for water-insoluble drug AMB. Furthermore, the results of the in vivo study on rabbits showed that the selected formulation was a safe and effective long-term sustained-released intra-articular injectable AMB preparation. Therefore, the presented in situ AMB gel could reduce the frequency of the administration in the AMB treatment of fungal arthritis, and then would get a good patient compliance.  相似文献   
25.
Li  Yuesong  Li  Shunlei  Guo  Kunyi  Fang  Xia  Habibi  Mostafa 《Engineering with Computers》2020,38(1):703-724

This research presents bending responses of FG-GPLRC plates based upon higher order shear deformation theory (HSDT) for various sets of boundary conditions. The rule of the mixture and modified Halpin–Tsai model are engaged to provide the effective material constant of the composite layers. By employing Hamilton’s principle, the governing equations of the structure are derived and solved with the aid of the differential quadrature method (DQM). Afterward, a parametric study is done to present the effects of three kinds of FG patterns, weight fraction of the GPLs, radius ratio, and thickness to inner radius ratio on the bending characteristics of the FG-GPLRC disk. Numerical results reveal that in the initial value of the \(Zt/h\), using more GPLs for reinforcing the structure provides an increase in the normal stresses but this matter is inverse for the higher value of the \(Zt/h\). The results show that considering the smaller radius ratio is a reason for boosting the shear stresses of the structure for each \(Zt/h\). Another consequence is that for the negative value of \(Zt/h\), it is true that by increasing \(h/{R}_{i}\) , the normal stresses increases but if there is positive value for \(Zt/h\), the radial and circumferential stresses fall down by having an increase in the \(h/{R}_{i}\).

  相似文献   
26.
Yang  Xi  Gao  Ling  Guo  Qing  Li  Yongjiang  Ma  Yue  Yang  Ju  Gong  Changyang  Yi  Cheng 《Nano Research》2020,13(10):2579-2594

Over the past decade, numerous studies have attempted to enhance the effectiveness of radiotherapy (external beam radiotherapy and internal radioisotope therapy) for cancer treatment. However, the low radiation absorption coefficient and radiation resistance of tumors remain major critical challenges for radiotherapy in the clinic. With the development of nanomedicine, nanomaterials in combination with radiotherapy offer the possibility to improve the efficiency of radiotherapy in tumors. Nanomaterials act not only as radiosensitizers to enhance radiation energy, but also as nanocarriers to deliver therapeutic units in combating radiation resistance. In this review, we discuss opportunities for a synergistic cancer therapy by combining radiotherapy based on nanomaterials designed for chemotherapy, photodynamic therapy, photothermal therapy, gas therapy, genetic therapy, and immunotherapy. We highlight how nanomaterials can be utilized to amplify antitumor radiation responses and describe cooperative enhancement interactions among these synergistic therapies. Moreover, the potential challenges and future prospects of radio-based nanomedicine to maximize their synergistic efficiency for cancer treatment are identified.

  相似文献   
27.
魏增 《中国氯碱》2015,(2):26-29
通过对ADC行业当前现状的分析,包括产能、产业格局、工艺、市场、环保、运输等方面问题的阐述,提出了以联二脲取代ADC发泡剂为新的产业分界点的观点,通过产业转移和上下游的调整,发挥东西部各自的综合优势,促进ADC发泡剂产业的升级。  相似文献   
28.
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results.  相似文献   
29.
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer.  相似文献   
30.
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号