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   19454篇
  免费   730篇
  国内免费   440篇
工业技术   20624篇
  2024年   15篇
  2023年   126篇
  2022年   188篇
  2021年   313篇
  2020年   263篇
  2019年   278篇
  2018年   266篇
  2017年   252篇
  2016年   255篇
  2015年   342篇
  2014年   613篇
  2013年   757篇
  2012年   1302篇
  2011年   3643篇
  2010年   1614篇
  2009年   1512篇
  2008年   1123篇
  2007年   1027篇
  2006年   852篇
  2005年   961篇
  2004年   789篇
  2003年   841篇
  2002年   527篇
  2001年   252篇
  2000年   213篇
  1999年   275篇
  1998年   348篇
  1997年   238篇
  1996年   187篇
  1995年   161篇
  1994年   137篇
  1993年   105篇
  1992年   99篇
  1991年   85篇
  1990年   69篇
  1989年   71篇
  1988年   66篇
  1987年   47篇
  1986年   48篇
  1985年   45篇
  1984年   51篇
  1983年   31篇
  1982年   42篇
  1981年   33篇
  1980年   21篇
  1979年   14篇
  1977年   20篇
  1976年   19篇
  1974年   19篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 454 毫秒
91.
文中严格地讨论了任意截面形状,任意模式的柱形谐振腔Q值与构成该谐振器的传输线衰减常数间的关系,给出了更一般的公式,推广了Davidson和Sim-monds^[1]、Barlow和Cullen^[2]以及Yeh和Shimabukuro^[3,4]的结果。  相似文献   
92.
The bicycle industry is an interesting case where East Asian firms have made a considerable impact, but where Taiwan has outperformed Korea. In the Korean sector, none of the well-known chaebol such as Samsung have become involved, and the incumbent firms experienced slow growth until there was government intervention in the 1980s. In Taiwan, small dynamic firms responded to large export orders in the early 1970s, and established a lasting lead which has been regenerated through technological upgrading. The paper argues that both countries’ bicycle industries have a vertically non-integrated structure, with extensive internal sub-contracting, and that the differences between the countries can be attributed to the timing and effcacy of industrial policy interventions.  相似文献   
93.
PURPOSE: To demonstrate a superselective intraarterial chemotherapy as a therapeutic alternative in the treatment of previously treated recurrent lymph node metastases in breast cancer. METHODS: 14 patients with recurrent lymph node metastases in cases of breast cancer were presented to be treated by intraarterial chemotherapy of 25 mg mitoxantrone/m2 over a period of 24 hours. In two patients with superclavicular lymph node involvement an intraarterial therapy could not be carried out because of a vascular connection to the anterior spinal artery. Involved lymph stations could be reached in superselective technique by side branches of the subclavian artery. Heparin coverage was given intravenously. Every patient had had surgery, radiation, systemic chemo- and hormonal therapy before and was now graded as inoperable. Therapy indication was given by local tumour-induced symptoms. RESULTS: In the 12 treated cases complete remission was seen in three, partial remission in 4, a steady state in two and a progressive disease in three. There were no complications or severe side effects. CONCLUSION: Intraarterial chemotherapy is an effective and well tolerated treatment in recurrent lymph node metastases in cases of breast cancer even if conventional therapies can no longer be used.  相似文献   
94.
并矢格林函数的对偶关系   总被引:1,自引:0,他引:1  
文中给出了均匀有界空间中的并矢格林函数在几种情况下的对偶关系,并应用于同轴腔的并矢格林函数。  相似文献   
95.
We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII) for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO2 interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force which is sufficient to overcome the silicon fracture resistance.  相似文献   
96.
97.
The problem of the non-causal inversion of linear multivariable discrete-time systems is analyzed in the geometric approach framework and is solved through the computation of convolution profiles which guarantee perfect tracking under the assumption of infinite-length preaction and postaction time intervals. It is shown how the shape of the convolution profiles is related to both the relative degree and the invariant zeros of the plant. A computational setting for the convolution profiles is derived by means of the standard geometric approach tools. Feasibility constraints are also taken into account. A possible implementation scheme, based on a finite impulse response system acting on a stabilized control loop, is provided.  相似文献   
98.
本文讨论了用辉光放电法制备氮化硅薄膜时衬底温度、射频功率和气体流量比对薄膜的电导率、介电常数和击穿强度的影响。通过优化生长条件,制备了优质非晶氮化硅薄膜,其介电常数为7.5、击穿强度为5.5MV/cm、电导率为10-13(Ωcm)-1。  相似文献   
99.
对传统双曲线极尖的四极透镜进行了磁性能分析。在此基础上,提出了极尖断面为折线的四极透镜结构。磁场的数值分析以及测量结果表明:该结构产生的场梯度均匀,且具有磁场集中、磁场梯度高、便于加工和安装的对称性控制等优点。该结构的四极透镜已用于CYCIAE-30回旋加速器和HI-13串列加速器束流输运线之中  相似文献   
100.
Bi-layer CoCrTa/Cr films were deposited on textured aluminium or textured NiP-plated aluminium substrate by d.c. magnetron sputtering. The crystal anisotropy and thereby magnetic properties depending on substrate material, substrate temperature and texturing, were investigated. The magnetic crystal anisotropy induced by the mechanical texture on aluminium or NiP/Al substrates along the texture lines for the film deposited at high temperature, were clearly observed, while the film deposited at low temperature shows less prominent anisotropic behaviour. X-ray diffraction analysis indicates a change in the preferred orientation of the chromium and CoCrTa films sputtered on different substrates at different temperatures. It was found that a high substrate temperature was beneficial to the formation of Cr(002) and therefore epitaxial growth of Co(11¯20) on Cr(002) for either aluminium or NiP/Al substrates.  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