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   22782篇
  免费   883篇
  国内免费   83篇
电工技术   293篇
综合类   44篇
化学工业   5146篇
金属工艺   478篇
机械仪表   460篇
建筑科学   1718篇
矿业工程   160篇
能源动力   686篇
轻工业   2135篇
水利工程   182篇
石油天然气   56篇
武器工业   1篇
无线电   1487篇
一般工业技术   4161篇
冶金工业   2769篇
原子能技术   137篇
自动化技术   3835篇
  2023年   152篇
  2022年   308篇
  2021年   533篇
  2020年   312篇
  2019年   327篇
  2018年   493篇
  2017年   425篇
  2016年   530篇
  2015年   479篇
  2014年   689篇
  2013年   1506篇
  2012年   1081篇
  2011年   1518篇
  2010年   1092篇
  2009年   1043篇
  2008年   1265篇
  2007年   1098篇
  2006年   939篇
  2005年   865篇
  2004年   774篇
  2003年   688篇
  2002年   660篇
  2001年   392篇
  2000年   376篇
  1999年   413篇
  1998年   409篇
  1997年   371篇
  1996年   340篇
  1995年   297篇
  1994年   302篇
  1993年   297篇
  1992年   250篇
  1991年   214篇
  1990年   201篇
  1989年   230篇
  1988年   186篇
  1987年   177篇
  1986年   174篇
  1985年   239篇
  1984年   214篇
  1983年   184篇
  1982年   168篇
  1981年   195篇
  1980年   130篇
  1979年   147篇
  1978年   143篇
  1977年   127篇
  1976年   138篇
  1975年   120篇
  1974年   105篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
861.
The production of zeolite granules varies in the amounts of binder content and different drying/activation temperatures. Here, the influence of moisture content and cyclic moisture loading and unloading on the mechanical properties like the strength of three different types of zeolite granules has been studied by uniaxial compression tests. The force‐displacement curves and scanning electron microscopy pictures of the granule and fracture surfaces show that with increasing number of moistening‐drying cycles, a continuous decrease in the strength of granules take place due to non‐regenerative damage of the structure.  相似文献   
862.
863.
864.
865.
866.
Abstract

Context: Aerosol delivery to animals in preclinical settings has historically been very challenging, requiring the use of techniques, such as intratracheal instillation and dry powder insufflation, that are somewhat invasive, inefficient and not representative of clinical inhalation.

Objective: The objective of this work is to develop a system to deliver dry powder to dogs in an efficient and effective manner for the study of new anti-migraine compounds in development.

Materials and methods: The new device uses a metered aliquot of a dry gas to force dry powder drug from a pre-filled HPMC capsule into an AeroChamber® spacer for subsequent inhalation by the animal.

Results: The delivery of two invesigational migraine drugs via the new device was assessed in vitro using abbreviated Andersen cascade impaction and showed the device is capable of generating a reproducible delivered dose of up to ~68% with more than 50% of the dose in the respirable range. In vivo studies have also been performed showing that this device effectively delivered the migraine drugs to spontaneously breathing dogs using a proprietary validated dog inhalation model.

Discussion: Results confirmed that the air pressurized capsule device (APCD) was effective in delivering the APIs to lungs of the animals. The in vivo data verified the advantages of inhaled delivery over oral delivery for this class of drugs and were used to establish the cardiopulmonary and respiratory side effect liability profile for these compounds.

Conclusions: This work has demonstrated the utility of this device for quick and accurate screening of prospective drug candidates, representing a significant improvement in ease of use and reprodicibility over current delivery methods.  相似文献   
867.
868.
869.
Motivated by the possibility of modifying energy levels of a molecule without substantially changing its band gap, the impact of gradual fluorination on the optical and structural properties of zinc phthalocyanine (FnZnPc) thin films and the electronic characteristics of FnZnPc/C60 (n = 0, 4, 8, 16) bilayer cells is investigated. UV–vis measurements reveal similar Q‐ and B‐band absorption of FnZnPc thin films with n = 0, 4, 8, whereas for F16ZnPc a different absorption pattern is detected. A correlation between structure and electronic transport is deduced. For F4ZnPc/C60 cells, the enhanced long range order supports fill factors of 55% and an increase of the short circuit current density by 18%, compared to ZnPc/C60. As a parameter being sensitive to the organic/organic interface energetics, the open circuit voltage is analyzed. An enhancement of this quantity by 27% and 50% is detected for F4ZnPc‐ and F8ZnPc‐based devices, respectively, and is attributed to an increase of the quasi‐Fermi level splitting at the donor/acceptor interface. In contrast, for F16ZnPc/C60 a decrease of the open circuit voltage is observed. Complementary photoelectron spectroscopy, external quantum efficiency, and photoluminescence measurements reveal a different working principle, which is ascribed to the particular energy level alignment at the interface of the photoactive materials.  相似文献   
870.
The architecture of the Renzo Piano Building Workshop (RPBW) is renowned internationally for the formal refinement of its components and detailing as well as for its sensitive responses to context, both in terms of its physical surroundings and local construction traditions. But, as architectural author and Piano specialist Peter Buchanan reminds us, the central concern of the practice remains focused on the original core impetus of expandingthe bounds of what technology and materials can achieve.  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