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   55341篇
  免费   5239篇
  国内免费   2658篇
电工技术   3497篇
技术理论   8篇
综合类   3627篇
化学工业   9416篇
金属工艺   2932篇
机械仪表   3273篇
建筑科学   3979篇
矿业工程   1508篇
能源动力   1754篇
轻工业   3488篇
水利工程   1099篇
石油天然气   2834篇
武器工业   646篇
无线电   6948篇
一般工业技术   6764篇
冶金工业   2905篇
原子能技术   697篇
自动化技术   7863篇
  2024年   256篇
  2023年   909篇
  2022年   1803篇
  2021年   2450篇
  2020年   1819篇
  2019年   1522篇
  2018年   1696篇
  2017年   1809篇
  2016年   1626篇
  2015年   2279篇
  2014年   2704篇
  2013年   3433篇
  2012年   3571篇
  2011年   3787篇
  2010年   3322篇
  2009年   3228篇
  2008年   3108篇
  2007年   2944篇
  2006年   2975篇
  2005年   2468篇
  2004年   1852篇
  2003年   1616篇
  2002年   1671篇
  2001年   1531篇
  2000年   1316篇
  1999年   1330篇
  1998年   1159篇
  1997年   989篇
  1996年   801篇
  1995年   670篇
  1994年   495篇
  1993年   429篇
  1992年   329篇
  1991年   266篇
  1990年   183篇
  1989年   179篇
  1988年   144篇
  1987年   86篇
  1986年   88篇
  1985年   77篇
  1984年   33篇
  1983年   27篇
  1982年   37篇
  1981年   34篇
  1980年   23篇
  1979年   21篇
  1977年   16篇
  1976年   19篇
  1974年   13篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
The {100} facet of single-crystalline TiO2(B) is an ideal platform for inserting Li ions, but it is hard to be obtained due to its high surface energy. Here, the single-crystalline TiO2(B) nanobelts from H2Ti3O7 with nearly 70% {100} facets exposed are synthesized, which significantly enhances Li-storage capacity. The first-principle calculations demonstrate an ab in-plane 2D diffusion through the exposed {100} facets. As a consequence, the nanobelts can significantly accommodate Li ions in LiTiO2 formula with specific capacity up to 335 mAh g−1, which is in good agreement with the electrochemical characterizations. Coating with conductive and protective poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), the cut-off discharge voltage is as low as 0.5 V, leading to a capacity of 160.7 mAh g−1 after 1500 cycles with a retention rate of 66% at 1C. This work provides a practical strategy to increase the Li-ion capacity and cycle stability by tailoring the crystal orientation and nanostructures.  相似文献   
32.
Cone-beam X-ray luminescence computed tomography (CB-XLCT) is an attractive hybrid imaging modality, and it has the potential of monitoring the metabolic processes of nanophosphors-based drugs in vivo. However, the XLCT imaging suffers from a severe ill-posed problem. In this work, a sparse nonconvex Lp (0?p?L1 regularization. Further, an iteratively reweighted split augmented lagrangian shrinkage algorithm (IRW_SALSA-Lp) was proposed to efficiently solve the non-convex Lp (0?p?p-values (1/16, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8) in both 3D digital mouse experiments and in vivo experiments. The results demonstrate that the proposed non-convex methods outperform L2 and L1 regularization in accurately recovering sparse targets in CB-XLCT. And among all the non-convex p-values, our Lp(1/4?p?相似文献   
33.
The solvent-dependent polymorphism of the active pharmaceutical ingredient (API) carbamazepine is interpreted from calculations of the solid-state and API-solvent intermolecular interactions. These simulations suggested that apolar solute-solute interactions could be disrupted by apolar solvents. In contrast, the polar solute-solute interactions were found to be easily disrupted by polar and protic solvents. This is consistent with experimental observations that the crystallization of the metastable form II is more dominant in apolar solvents. The Mercury program remains the gold standard in terms of usability; however, further expansion into more complex simulation techniques could make this package of even greater use in pharmaceutical manufacturing workflows.  相似文献   
34.
35.
Journal of Mechanical Science and Technology - A multi-robot collaborative towing system fixed on floating base for high load marine work was established in this paper, and its dynamics and...  相似文献   
36.
A technique using a lifting scheme is presented for constructing compactly supported wavelets whose coefficients are composed of free variables locating in an interval. An efficient approach-based wavelet for image compression is developed by selecting the coefficients of the 9-7 wavelet filter and associated lifting scheme. Furthermore, the rationalised coefficients wavelet filter that can be implemented with simple integer arithmetic is achieved and its characteristic is close to the well known original irrational coefficients 9-7 wavelet filters developed by A. Cohen et al. (Commun. Pure Appl. Maths., vol.45, no.1, p.485-560, 1992). To reduce the computational cost of image coding applications further, an acceleration technique is proposed for the lifting steps. Software and hardware simulations show that the new method has very low complexity, and simultaneously preserves the high quality of the compressed image.  相似文献   
37.
湘中海相浅层湘冷1井酸压工艺研究及应用   总被引:2,自引:0,他引:2  
湘冷1井具有气层埋藏浅(400m-500m)、纵向上裂隙发育的特点,属低孔、低渗的含泥质灰岩致密储层。大量室内实验和研究采用“前置液酸压+闭合酸化”工艺技术,并优选了相应降阻酸和闭合酸配方。通过酸压实现了该井工业油气流的突破,取得了明显的增产效果,为新区海相浅层气的开发探索出了一套成熟的改造增产措施。  相似文献   
38.
江澄 《山西建筑》2006,32(4):42-43
从政策、城市与区域规划、环境、文化及其传承因素、基础设施等方面探析了高校新校区选址有关的主要影响因素,以满足高等学校大规模的扩建要求,促进高等教育的发展。  相似文献   
39.
In this letter, we introduce and investigate a new problem referred to as the All Hops Shortest Paths (AHSP) problem. The AHSP problem involves selecting, for all hop counts, the shortest paths from a given source to any other node in a network. We derive a tight lower bound on the worst-case computational complexities of the optimal comparison-based solutions to AHSP.  相似文献   
40.
文章介绍了运煤车间爆破拆除工程的设计、施工经过及防后座的措施,对于复杂爆破环境的建筑物拆除有一定参考意义。  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