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   1931篇
  免费   90篇
  国内免费   4篇
电工技术   21篇
综合类   1篇
化学工业   409篇
金属工艺   25篇
机械仪表   31篇
建筑科学   122篇
矿业工程   3篇
能源动力   79篇
轻工业   120篇
水利工程   19篇
石油天然气   12篇
无线电   179篇
一般工业技术   311篇
冶金工业   286篇
原子能技术   7篇
自动化技术   400篇
  2023年   10篇
  2022年   18篇
  2021年   27篇
  2020年   22篇
  2019年   21篇
  2018年   35篇
  2017年   39篇
  2016年   37篇
  2015年   47篇
  2014年   69篇
  2013年   130篇
  2012年   97篇
  2011年   138篇
  2010年   99篇
  2009年   102篇
  2008年   104篇
  2007年   91篇
  2006年   111篇
  2005年   85篇
  2004年   92篇
  2003年   68篇
  2002年   67篇
  2001年   32篇
  2000年   26篇
  1999年   32篇
  1998年   28篇
  1997年   24篇
  1996年   35篇
  1995年   25篇
  1994年   20篇
  1993年   30篇
  1992年   25篇
  1991年   21篇
  1990年   14篇
  1989年   20篇
  1988年   7篇
  1987年   12篇
  1986年   9篇
  1985年   18篇
  1984年   16篇
  1983年   6篇
  1982年   17篇
  1981年   10篇
  1980年   7篇
  1979年   12篇
  1978年   8篇
  1977年   7篇
  1976年   13篇
  1975年   7篇
  1970年   7篇
排序方式: 共有2025条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
The aim of this study was to evaluate the combined effect of salt (sodium chloride, 0–8% w/v), sorbate (potassium sorbate, 0–4.5% w/v), nisin (0–500 ppm) and lysozyme (0–500 ppm) on the survival of Clostridium sporogenes as a non‐toxigenic surrogate of Clostridium botulinum in terms of the probability of growth by using a central composite rotatable design. The results indicated that salt and sorbate were the most effective factors in preventing the growth of Cl. sporogenes in high‐moisture (>95%) and low‐acid conditions. The probability of growth of Cl. sporogenes in broth was reduced by combinations of salt and sorbate. Nisin and lysozyme had insignificant effects on the probability of growth of Cl. sporogenes (P > 0.05). Lysozyme individually and in combination with nisin had no inhibitory effect on Cl. sporogenes. Overall, the addition of sorbate and lysozyme may allow the salt concentration to be reduced while preventing growth.  相似文献   
65.
Human dental pulp stem cells (hDPSCs) are some of the most promising stem cell types for regenerative therapies given their ability to grow in the absence of serum and their realistic possibility to be used in autologous grafts. In this review, we describe the particular advantages of hDPSCs for neuroregenerative cell therapies. We thoroughly discuss the knowledge about their embryonic origin and characteristics of their postnatal niche, as well as the current status of cell culture protocols to maximize their multilineage differentiation potential, highlighting some common issues when assessing neuronal differentiation fates of hDPSCs. We also review the recent progress on neuroprotective and immunomodulatory capacity of hDPSCs and their secreted extracellular vesicles, as well as their combination with scaffold materials to improve their functional integration on the injured central nervous system (CNS) and peripheral nervous system (PNS). Finally, we offer some perspectives on the current and possible future applications of hDPSCs in neuroregenerative cell therapies.  相似文献   
66.
The dynamics of the local atomic pair correlations in the FeSe x Te1?x ( x = 0.1, 0.5, and 0.9) system were investigated using the dynamic pair density function analysis obtained from inelastic neutron scattering. Distinct differences are observed between the superconducting and nonsuperconducting compositions, particularly involving the local dynamics of the Fe-Fe correlations. The energy scale of the observed differences is between 25 and 30 meV. In the nonsuperconducting FeSe0.1Te0.9, the Fe-Fe correlations are enhanced with cooling that may signal stronger exchange interactions, while in the superconducting compositions of FeSe0.9Te0.1 and FeSe0.5Te0.5, they are suppressed.  相似文献   
67.
68.
69.
In the current study, the morphology including tortuosity, and the permeability of 50-mm thick commercially available 30, 40, 50, and 80 pores per inch (PPI) alumina ceramic foam filters (CFFs) have been investigated. Measurements have been taken of cell (pore), window, and strut sizes, porosity, tortuosity, and liquid permeability. Water velocities from ~0.015 to 0.77 m/s have been used to derive both first-order (Darcy) and second-order (Non-Darcy) terms for being used with the Forchheimer equation. Measurements were made using 49-mm “straight through” and 101-mm diameter “expanding flow field” designs. Results from the two designs are compared with calculations made using COMSOL 4.2a® 2D axial symmetric finite element modeling (FEM), as a function of velocity and filter PPI. Permeability results are correlated using directly measurable parameters and compared with the previously published results. Development of improved wall sealing (49 mm) and elimination of wall effects (101 mm) have led to a high level of agreement between experimental, analytic, and FEM methods (±0 to 7 pct on predicted pressure drop) for both types of experiments. Tortuosity has been determined by two inductive methods, one using cold-solidified samples at 60 kHz and the other using liquid metal at 50 Hz, giving comparable results.  相似文献   
70.
According to some recent research, Americans hold a great deal of misinformation about important political issues. However, such investigations treat incorrect answers to quiz questions measuring knowledge as evidence of misinformation. This study instead defines misperceptions as incorrect answers that respondents are confident are correct. Two surveys of representative samples of American adults on the Affordable Care Act reveal that most people were uncertain about the provisions in the law. Confidently held incorrect beliefs were far less common than incorrect answers. Misperceptions were most prevalent on aspects of the law on which elites prominently and persistently made incorrect claims. Furthermore, although Americans appear to have learned about the law between 2010 and 2012, misperceptions on many provisions of the law persisted.  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