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   128759篇
  免费   8871篇
  国内免费   3114篇
电工技术   6830篇
技术理论   1篇
综合类   6642篇
化学工业   20505篇
金属工艺   6300篇
机械仪表   6943篇
建筑科学   9081篇
矿业工程   3197篇
能源动力   3672篇
轻工业   8837篇
水利工程   2362篇
石油天然气   4678篇
武器工业   887篇
无线电   13487篇
一般工业技术   16224篇
冶金工业   10278篇
原子能技术   1371篇
自动化技术   19449篇
  2025年   357篇
  2024年   2116篇
  2023年   1971篇
  2022年   3231篇
  2021年   4420篇
  2020年   3645篇
  2019年   3266篇
  2018年   3252篇
  2017年   3503篇
  2016年   3541篇
  2015年   4650篇
  2014年   5641篇
  2013年   7812篇
  2012年   7806篇
  2011年   8623篇
  2010年   7690篇
  2009年   7540篇
  2008年   7544篇
  2007年   7361篇
  2006年   6688篇
  2005年   5808篇
  2004年   4092篇
  2003年   3559篇
  2002年   3330篇
  2001年   2705篇
  2000年   2245篇
  1999年   2229篇
  1998年   1684篇
  1997年   1551篇
  1996年   1393篇
  1995年   1262篇
  1994年   1093篇
  1993年   927篇
  1992年   829篇
  1991年   551篇
  1990年   631篇
  1989年   571篇
  1988年   458篇
  1987年   443篇
  1986年   385篇
  1985年   453篇
  1984年   452篇
  1983年   332篇
  1982年   322篇
  1981年   296篇
  1980年   290篇
  1979年   278篇
  1978年   254篇
  1977年   230篇
  1976年   213篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
建设工程涉外设计合同风险防范   总被引:2,自引:0,他引:2  
中国参加WTO后,在扩大对外开放、拉动内需保增长政策指导下,一大批重点建设工程陆续上马,有许多外国设计企业及其在华机构加入中国建设工程的设计,其中,国有独资项目占据很大的比重。笔者结合参与全国十运会场馆一南京奥体中心以及江苏省人民医院扩建、南京图书管等多个大型项目工程全程法律保障实践,就工程设计合同风险防范,一舒管见。  相似文献   
82.
Owing to the deficiency in early warning for high concrete dam,a formula was established to characterize the deformation behavior of high concrete dam as a whole.The early warning index of spatial deformation was calculated by low probability principle on the basis of the deformation entropy formula proposed.The steps were as follows.Firstly,the probability method was utilized to define the degree of order and degree of chaos for each survey point.Secondly,the weight distribution among the survey points was...  相似文献   
83.
Cu–dinitro–diamino phthalocyanine was synthesized and converted to the diazonium salt. Polyacrylamide bonded CuPc(NO2)2 [PAA–CuPc(NO2)2] (I) was synthesized by hot polymerization of acrylamide and this diazonium salt. Polymer(I) is water soluble and contains about 7 mol % CuPc(NO2)2 rings, which are covalently bonded to PAA. Polymer(I) shows good photoconductivity, which is much better than that of the corresponding phthalocyanine monomers. By doping with iodine (I2), the photosensitivity of polymer(I) is increased, which through fluorescence analysis is explained by the fact that a charge–transfer complex (CTC) of polymer(I) with I2 is formed. The influence of interface layer (IFL) and charge–transportation material (CTM) on the photoconductivity of polymer(I) were also studied.  相似文献   
84.
85.
86.
Tungsten oxide (WO3) nanorods array prepared using chemical vapor deposition techniques was studied. The influence of oxygen gas concentration on the nanoscale tungsten oxide structure was observed; it was responsible for the stoichiometric and morphology variation from nanoscale particle to nanorods array. Experimental results also indicated that the deposition temperature was highly related to the morphology; the chemical structure, however, was stable. The evolution of the crystalline structure and surface morphology was analyzed by scanning electron microscopy, Raman spectra and X-ray diffraction approaches. The stoichiometric variation was indicated by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.  相似文献   
87.
In this paper, we propose a new hard problem, called bilateral inhomogeneous small integer solution (Bi-ISIS), which can be seen as an extension of the small integer solution problem on lattices. The main idea is that, instead of choosing a rectangle matrix, we choose a square matrix with small rank to generate Bi-ISIS problem without affecting the hardness of the underlying SIS problem. Based on this new problem, we present two new hardness problems: computational Bi-ISIS and decisional problems. As a direct application of these problems, we construct a new lattice-based key exchange (KE) protocol, which is analogous to the classic Diffie- Hellman KE protocol. We prove the security of this protocol and show that it provides better security in case of worst-case hardness of lattice problems, relatively efficient implementations, and great simplicity.  相似文献   
88.
The mechanisms and kinetics of radical entry in emulsion polymerizations utilizing redox initiation are investigated using polymerization rate data obtained by reaction calorimetry and electrospray mass spectroscopy analysis of initiator-derived aqueous-phase products. These data have been used to evaluate an initiation scheme for redox-initiated emulsion polymerizations of common monomers such as styrene and methyl methacrylate based around the oxidant, tert-butyl hydroperoxide. Redox initiators are broadly classed by the solubility of their radical products: Hydrophilic radicals enter by propagating to a critical degree of polymerization to become surface-active whilst more hydrophobic radicals may enter particles directly. When direct entry is applicable (the hydrophobic case), initiation efficiency will always be very high.  相似文献   
89.
90.
刘峰  李俊明 《重型机械》2006,(Z1):80-83
详细论述了卷取机动态力矩的数学模型及在控制系统中的实现问题,最后给出了采用CAD计算动态力矩和动态电流、确定相关工艺参数的方法.  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