首页 | 官方网站   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   87989篇
  免费   6302篇
  国内免费   2982篇
工业技术   97273篇
  2024年   331篇
  2023年   1338篇
  2022年   2336篇
  2021年   3195篇
  2020年   2387篇
  2019年   2070篇
  2018年   2297篇
  2017年   2574篇
  2016年   2401篇
  2015年   3013篇
  2014年   4102篇
  2013年   5161篇
  2012年   5328篇
  2011年   5612篇
  2010年   4987篇
  2009年   4789篇
  2008年   4557篇
  2007年   4477篇
  2006年   4723篇
  2005年   4186篇
  2004年   2832篇
  2003年   2538篇
  2002年   2224篇
  2001年   2051篇
  2000年   2306篇
  1999年   2591篇
  1998年   2404篇
  1997年   1907篇
  1996年   1760篇
  1995年   1455篇
  1994年   1225篇
  1993年   882篇
  1992年   657篇
  1991年   545篇
  1990年   409篇
  1989年   367篇
  1988年   319篇
  1987年   175篇
  1986年   165篇
  1985年   112篇
  1984年   98篇
  1983年   63篇
  1982年   60篇
  1981年   54篇
  1980年   38篇
  1979年   32篇
  1978年   13篇
  1977年   33篇
  1976年   16篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
In this letter, we supplement the derivation in Laurent's paper by mathematically proving that combining binary continuous phase modulation (CPM) signals in different bit durations results in the decomposed CPM expression consisting of a set of continuous amplitude-modulated pulse functions.  相似文献   
42.
A feasibility analysis methodology adopted from reactive distillation is applied to membrane reactors. A model is formulated to depict the reactive liquid phase composition on the retentate side of a continuous type membrane reactor. The effects of both the chemical reaction kinetics and the membrane mass transfer kinetics on the feasible products are elucidated by means of retentate phase diagrams and bifurcation analysis. The proposed method can be applied to various membrane processes, independent of the specific structure of the membrane. Two quaternary reaction systems are considered to illustrate the methodology. In the first hypothetical system, it is shown how selective membranes can influence the sequence of effective volatilities which in turn affects the feasible products of the system. In the second example of practical importance, i.e. the heterogeneously catalysed synthesis of propyl acetate coupled with permeation through a porous polycarbonate membrane, the dusty gas model is applied to describe the component fluxes through the membrane. For the latter reaction system, the existence of reactive arheotrope is demonstrated. Arheotropes represent mass transfer controlled feasible products of membrane separation process.  相似文献   
43.
概述了钛铜复合棒研制开发及发展历程,并介绍了钛铜复合棒的主要性能,以及钛铜复合棒的标准化情况。  相似文献   
44.
Wet adhesion is widely adopted in biological adhesion systems in nature. Wet adhesion is studied in this paper with the focus on the effect of different contact shapes (flat, concave, convex, and ring-like) on the adhesion force. The evolution of the liquid bridge between a fiber tip and substrate during the detaching process shows two transition points. The first transition from the radius-controlled to the contact-angle controlled process is critical to influence the strength and robustness of adhesion. We show that a concave shape is more effective than a flat one, while a convex shape has no advantage. A ring-like contact shape has advantages in a hydrophobic environment and on a rough surface.  相似文献   
45.
BaMgAl10O17∶Eu2 (BAM) was prepared in the microemulsion system and its phase behavior was studied. There exists a small region in the reverse microemulsion system where the dispersed particles are of spherical form. In this way, BAM blue phosphor with good dispersion can be synthesized. The microemulsion phase diagrams of the pseudo-ternary system (Triton X-100/cosurfactant-oil-BAM brine) were first established intuitively by the dilution method. The microstructure of microemulsions was determined through eyeballing, conductance technique, and polar optical microscopy. Its phase behavior is affected by various factors, such as temperature (room temperature, 30, 40 ℃), oil, surfactants, and cosurfactants in microemulsions. According to the phase diagrams, the microemulsion system of Triton X-100/1-hexanol-hexane-BAM brine was chosen to prepare the precursor. The BAM phosphor can be obtained via sintering the precursor at a comparatively low temperature. The phosphors were characterized by XRD and vacuum ultraviolet (VUV) spectra.  相似文献   
46.
47.
48.
A novel integrated vacuum field emission (VFE) differential amplifier (diff-amp) utilizing carbon nanotube (CNT) emitters has been developed. A dual-mask microfabrication process was employed to achieve a VFE diff-amp by integrating identical CNT VFE transistors with built-in split gates and integrated anodes. The identical pair of triode amplifiers was well-matched in their device characteristics. The measured ac small-signal characteristics of the diff-amp showed a common-mode-rejection ratio (CMRR) of ~ 320 (~ 50 dB). The proposed analytical model of the CMRR was verified to be in good agreement with the experimental data. The successful implementation of the CNT diff-amp demonstrates a new way to achieve temperature and radiation tolerant VFE integrated microelectronics.  相似文献   
49.
推行岩土工程体制,在确保给定的安全水平条件下达到综合造价最低的目的。  相似文献   
50.
随着计算机及网络技术在现代企业生产经营管理中的广泛应用,特别是以网络为信息交流平台的企业CMIS、ERP和MRPII等管理系统的应用推广,使得企业生产经营的管理技术和理念相比传统管理的方式、方法也发生了根本性的变化。企业内外形成和交流的信息量成倍增加,组织生产经营信息逐步表现为操作流程规范化、信息应用集成化和信息环境复杂化的趋势,从而使得组织信息交流语言及接口的规范统一,标准化也日显重要。  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-23

京公网安备 11010802026262号