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   73602篇
  免费   5401篇
  国内免费   2801篇
电工技术   3884篇
技术理论   6篇
综合类   4450篇
化学工业   12705篇
金属工艺   3954篇
机械仪表   4811篇
建筑科学   5192篇
矿业工程   2405篇
能源动力   2232篇
轻工业   4783篇
水利工程   1008篇
石油天然气   5280篇
武器工业   461篇
无线电   7657篇
一般工业技术   9435篇
冶金工业   3934篇
原子能技术   750篇
自动化技术   8857篇
  2024年   301篇
  2023年   1263篇
  2022年   2104篇
  2021年   2909篇
  2020年   2198篇
  2019年   1962篇
  2018年   2301篇
  2017年   2502篇
  2016年   2075篇
  2015年   2696篇
  2014年   3439篇
  2013年   4218篇
  2012年   4349篇
  2011年   4864篇
  2010年   4183篇
  2009年   3959篇
  2008年   3867篇
  2007年   3730篇
  2006年   3808篇
  2005年   3442篇
  2004年   2299篇
  2003年   2092篇
  2002年   1872篇
  2001年   1652篇
  2000年   1803篇
  1999年   2048篇
  1998年   1767篇
  1997年   1425篇
  1996年   1406篇
  1995年   1186篇
  1994年   957篇
  1993年   717篇
  1992年   546篇
  1991年   428篇
  1990年   327篇
  1989年   254篇
  1988年   226篇
  1987年   142篇
  1986年   120篇
  1985年   96篇
  1984年   66篇
  1983年   40篇
  1982年   42篇
  1981年   30篇
  1980年   25篇
  1979年   13篇
  1977年   7篇
  1976年   8篇
  1975年   5篇
  1945年   4篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
SSO(Single Sign On)是并购整合后期的技术整合中必须要实现的一个功能,而通常不能直接将并购者的用户数据与被并购者的用户数据直接合并,本文着重分析了在实现SSO数据整合中可能存在的问题,并针对各个问题给出了初步的解决方案.  相似文献   
92.
笨蛋     
唐骏 《现代计算机》2010,(6):133-133
我喜欢挑战,总是不停地给自己寻找新目标。我不喜欢安逸的感觉,安逸会让我心里发慌。当我发现,现在做的事,十几二十年都可能没有大改变,看现在就可以预见未来,我就不再对它感兴趣了。所以,我总是不停地经历转折。  相似文献   
93.
Sun 《微型计算机》2009,(16):163-164
上期中,我们为大家带来了早期显卡的发展情况——显卡从无到有,从2D到3D,从性能到性能变强,其中的故事也非常的精彩。在经历了早期群雄逐鹿的时代后,显卡市场逐渐呈NVIDIA和ATI两分天下的局面。  相似文献   
94.
Since the harmonic components in the signal to be analyzed are uncertain and diverse, it is difficult to make the sampling frequency and the signal length be harmonically related to the component frequencies included in the signal, and the leakage is produced in the discrete Fourier transform. Based on the definition of the Herfindahl index in economics, the spectrum concentration can be defined and computed. The appropriate number of points can be decided according to the peak location of the spectrum concentration. The method and the examples are specified in detail in the paper.  相似文献   
95.
A new algorithm for reducing control points in lofted surface interpolation to rows of data points is presented in this paper. The key step of surface lofting is to obtain a set of compatible B-spline curves interpolating each row. Given a set of points and their parameterization, a necessary and sufficient condition is proposed to determine the existence of interpolating B-spline curves defined on a given knot vector. Based on this condition, we first properly construct a common knot vector that guarantees the existence of interpolating B-spline curves to each row of points. Then we calculate a set of interpolating B-spline curves defined on the common knot vector by energy minimization. Using this method, fewer control points are employed while maintaining a visually pleasing shape of the lofted surface. Several experimental results demonstrate the usability and quality of the proposed method.  相似文献   
96.
97.
Photoredox catalysis is a green solution for organics transformation and CO2 conversion into valuable fuels, meeting the challenges of sustainable energy and environmental concerns. However, the regulation of single-atomic active sites in organic framework not only influences the photoredox performance, but also limits the understanding of the relationship for photocatalytic selective organic conversion with CO2 valorization into one reaction system. As a prototype, different single-atomic metal (M) sites (M2+ = Fe2+, Co2+, Ni2+, Cu2+, and Zn2+) in hydrogen-bonded organic frameworks (M-HOF) backbone with bridging structure of metal-nitrogen are constructed by a typical “two-in-one” strategy for superior photocatalytic C N coupling reactions integrated with CO2 valorization. Remarkably, Zn-HOF achieves 100% conversion of benzylamine oxidative coupling reactions, 91% selectivity of N-benzylidenebenzylamine and CO2 conversion in one photoredox cycle. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to synergic effect of atomically dispersed metal sites and HOF host, decreasing the reaction energy barriers, enhancing CO2 adsorption and forming benzylcarbamic acid intermediate to promote the redox recycle. This work not only affords the rational design strategy of single-atom active sites in functional HOF, but also facilitates the fundamental insights upon the mechanism of versatile photoredox coupling reaction systems.  相似文献   
98.
Precise adjustment of the pore size, damage repair, and efficient cleaning is all challenges for the wider application of inorganic membranes. This study reports a simple strategy of combining dry-wet spinning and electrosynthesis to fabricate stainless-steel metal–organic framework composite membranes characterized by customizable pore sizes, targeted reparability, and high catalytic activity for membrane cleaning. The membrane pore size can be precisely customized in the range of 14–212 nm at nanoscale, and damaged membranes can be repaired by targeted treatment in 120 s. In addition, advanced oxidation processes can be used to quickly clean the membrane and achieve 98% flux recovery. The synergistic actions of the membrane matrix and the selective layer increase the adsorption energy of active sites to oxidant, shorten the electron transfer cycle, and enhance the overall catalytic performance. This study can provide a new direction for the development of advanced membranes for water purification and high-efficiency membrane cleaning methods.  相似文献   
99.
Smart textiles with good mechanical adaptability play an important role in personal protection, health monitoring, and aerospace applications. However, most of the reported thermally responsive polymers has long response time and poor processability, comfort, and wearability. Skin-core structures of thermally responsive fibers with multiple commercial fiber cores and temperature-responsive hydrogel skins are designed and fabricated, which exhibit rapid mechanical adaptability, good thermohardening, and thermal insulation. This universal method enables tight bonding between various commercial fiber cores and hydrogel skins via specific covalently anchored networks. At room temperature, prepared fibers show softness, flexibility, and skin compatibility similar to those of ordinary fibers. As temperature rises, smart fibers become hard, rigid, and self-supporting. The modulus of hydrogel skin increases from 304% to 30883%, showing good mechanoadaptability and impact resistance owing to the synergy between hydrophobic interactions and ionic bonding. Moreover, this synergistic effect leads to an increase in heat absorption, and fibers exhibit good thermal insulation, which reduces the contact temperature of the body surface by ≈25 °C under the external temperature of 95 °C, effectively preventing thermal burns. Notably, the active mechanoadaptability of these smart fibers using conductive fibers as cores is demonstrated. This study provides feasibility for fabricating environmentally adaptive intelligent textiles.  相似文献   
100.
Following logic in the silicon semiconductor industry, the existence of native oxide and suitable fabrication technology is essential for 2D semiconductors in planar integronics, which are surface-sensitive to typical coating technologies. To date, very few types of integronics are found to possess this feature. Herein, the 2D Bi2O2Te developed recently is reported to possess large-area synthesis and controllable thermal oxidation behavior toward single-crystal native oxides. This shows that surface-adsorbed oxygen atoms are inclined to penetrate across [Bi2O2]n2n+ layers and bond with the underlying [Te]n2n− at elevated temperatures, transforming directly into [TeO4]n2n− with the basic architecture remaining stable. The oxide can be adjusted to form in an accurate layer-by-layer manner with a low-stress sharp interface. The native oxide Bi2TeO6 layer (bandgap of ≈2.9 eV) exhibits visible-light transparency and is compatible with wet-chemical selective etching technology. These advances demonstrate the potential of Bi2O2Te in planar-integrated functional nanoelectronics such as tunnel junction devices, field-effect transistors, and memristors.  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