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   2101篇
  免费   54篇
  国内免费   5篇
电工技术   117篇
综合类   3篇
化学工业   401篇
金属工艺   64篇
机械仪表   34篇
建筑科学   47篇
能源动力   73篇
轻工业   122篇
水利工程   2篇
无线电   288篇
一般工业技术   330篇
冶金工业   406篇
原子能技术   90篇
自动化技术   183篇
  2023年   8篇
  2022年   13篇
  2021年   30篇
  2020年   26篇
  2019年   29篇
  2018年   31篇
  2017年   35篇
  2016年   41篇
  2015年   28篇
  2014年   51篇
  2013年   99篇
  2012年   61篇
  2011年   111篇
  2010年   89篇
  2009年   79篇
  2008年   96篇
  2007年   68篇
  2006年   81篇
  2005年   60篇
  2004年   60篇
  2003年   71篇
  2002年   77篇
  2001年   51篇
  2000年   33篇
  1999年   47篇
  1998年   157篇
  1997年   82篇
  1996年   80篇
  1995年   48篇
  1994年   48篇
  1993年   47篇
  1992年   30篇
  1991年   25篇
  1990年   23篇
  1989年   32篇
  1988年   15篇
  1987年   13篇
  1986年   24篇
  1985年   20篇
  1984年   23篇
  1983年   15篇
  1982年   16篇
  1981年   16篇
  1980年   13篇
  1979年   8篇
  1978年   8篇
  1977年   8篇
  1976年   9篇
  1975年   9篇
  1972年   5篇
排序方式: 共有2160条查询结果,搜索用时 15 毫秒
1.
Carbohydrates, fats, and proteins are the underlying energy sources for animals and are catabolized through specific biochemical cascades involving numerous enzymes. The catabolites and metabolites in these metabolic pathways are crucial for many cellular functions; therefore, an imbalance and/or dysregulation of these pathways causes cellular dysfunction, resulting in various metabolic diseases. Bone, a highly mineralized organ that serves as a skeleton of the body, undergoes continuous active turnover, which is required for the maintenance of healthy bony components through the deposition and resorption of bone matrix and minerals. This highly coordinated event is regulated throughout life by bone cells such as osteoblasts, osteoclasts, and osteocytes, and requires synchronized activities from different metabolic pathways. Here, we aim to provide a comprehensive review of the cellular metabolism involved in bone development and homeostasis, as revealed by mouse genetic studies.  相似文献   
2.
Polyvinylalcohol (PVA) polymer gel is a temperature sensitive polymeric gel, with a critical transition temperature (with H2O) of 310 K. At higher than 310 K, this temperature sensitive polymer gel shrinks because of discharging water, whereas at lower temperatures, the gel swelled because of absorbing water. The reversibility of the gel's volume change was confirmed by temperature swing. The adsorption behavior of an organic compound onto the PVA polymer gel in water was tested at various temperatures. The amount of adsorbed organic compound increased remarkably at temperatures higher than about 310 K. Then, it was confirmed that the organic compound in PVA polymer gel could be reversibly adsorbed and desorbed by a temperature change between 293 and 323 K. The mechanism of adsorption of the organic compound onto the PVA polymer gel could be explained by hydration and dehydration of polymer gel.  相似文献   
3.
We derive a linear correspondence between the variables of an encoder and those of a corresponding syndrome former. Using the derived correspondence, we show that the log-likelihood ratio of an information bit conditioned on a received sequence can be equally calculated using the syndrome trellis. It is shown that the proposed method also applies to recursive systematic convolutional codes which are typical constituent codes for turbo codes. Moreover, we show that soft-in syndrome decoding considering a priori probabilities of information bits is possible in the same way as for Viterbi decoding based on the code trellis. Hence, the proposed method can be applied to iterative decoding such as turbo decoding. We also show that the proposed method is effective for high-rate codes by making use of trellis modification.  相似文献   
4.
5.
We fabricated a 1-GHz-spaced 16-channel arrayed-waveguide grating (AWG) by using a new AWG configuration where the path of each arrayed waveguide winds backward and forward across a 4-in diameter wafer without crossing any other waveguides. The ultra-narrow (< 1 GHz) and stable transmission bands of this AWG can be used to construct a wavelength reference standard covering the S, C, and L bands in the dense wavelength-division-multiplexing network systems whose frequency deviation is /spl plusmn/160 MHz.  相似文献   
6.
We describe a low-loss athermal silica-based interleave filter with a lattice-form structure. We athermalize the filter by using a silicone-filled groove formed in each delay line and we employ a low-loss design to reduce the accumulated groove excess loss in the multiple delay lines. By using these designs, we obtained a very low groove excess loss of 0.4 dB and achieved satisfactory temperature insensitivity and optical characteristics with this filter.  相似文献   
7.
A silica-based 1.5%-/spl Delta/ 100 GHz-spacing 32-channel athermal arrayed-waveguide grating (AWG) with compact size and extremely low insertion loss is described. By reducing the fibre coupling loss and the excess loss in a silicone-filled groove, an insertion loss of 1.3 dB was achieved with this athermal AWG.  相似文献   
8.
We present simulation results of the vortex dynamics in a trapped Bose-Einstein condensate in the presence of a rotating optical lattice. Changing the potential amplitude and the relative rotation frequency between the condensate and the optical lattice, we find a rich variety of dynamical phases of vortices. In particular, when the optical lattice rotates faster than the condensate, the competition between the pinning force and the interactions by nucleated interstitial vortices leads to the melting of vortex lattice, yielding a vortex liquid phase.  相似文献   
9.
A strontium tantalum sulfide, SrTa2S5, has a hexagonal structure with lattice constants of a =3.32 and c=24.1 Å. With decreasing temperature the electrical resistivity decreases monotonically and exhibits an abrupt superconducting transition at 3.16 K (midpoint). The diamagnetic susceptibility is observed below Tc. The magnetic susceptibility is nearly independent of temperature above Tc and shows Pauli paramagnetism.  相似文献   
10.
Living organisms including humans drive circadian rhythm, and this rhythm influences the social structure and daily life of human beings. The suprachiasmatic nucleus (SCN) has been established as a pacemaker for mammalian circadian rhythm. There are many kinds of neurotransmitters and neuromodulators in this nucleus. The circadian systems are involved in oscillation, input (entrainment) and output (overt rhythm). Therefore in this review, pharmacological characteristics of circadian systems in relation to the SCN are discussed by focussing especially upon the roles of various neurotransmitters and modulators.  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