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   8527篇
  免费   91篇
  国内免费   5篇
电工技术   45篇
综合类   3篇
化学工业   707篇
金属工艺   51篇
机械仪表   61篇
建筑科学   113篇
矿业工程   13篇
能源动力   71篇
轻工业   337篇
水利工程   22篇
石油天然气   25篇
无线电   477篇
一般工业技术   621篇
冶金工业   5505篇
原子能技术   52篇
自动化技术   520篇
  2022年   25篇
  2021年   35篇
  2020年   30篇
  2018年   40篇
  2017年   34篇
  2016年   36篇
  2015年   31篇
  2014年   77篇
  2013年   179篇
  2012年   129篇
  2011年   122篇
  2010年   108篇
  2009年   113篇
  2008年   133篇
  2007年   146篇
  2006年   113篇
  2005年   123篇
  2004年   109篇
  2003年   116篇
  2002年   98篇
  2001年   89篇
  2000年   93篇
  1999年   221篇
  1998年   1622篇
  1997年   905篇
  1996年   667篇
  1995年   360篇
  1994年   342篇
  1993年   362篇
  1992年   108篇
  1991年   123篇
  1990年   133篇
  1989年   114篇
  1988年   108篇
  1987年   109篇
  1986年   92篇
  1985年   114篇
  1984年   58篇
  1983年   82篇
  1982年   75篇
  1981年   69篇
  1980年   84篇
  1979年   49篇
  1978年   53篇
  1977年   163篇
  1976年   340篇
  1975年   43篇
  1974年   24篇
  1973年   32篇
  1972年   26篇
排序方式: 共有8623条查询结果,搜索用时 31 毫秒
71.
72.
This paper reports a method to produce networks of crystalline gallium oxide comprised of one‐dimensional (1D) nanostructures. Because of the unique arrangement of wires, these crystalline networks are termed as ‘nanowebs’. Nanowebs are of great technological interest since they contain wire densities of the order of 109 cm–2. A possible mechanism for the fast self‐assembly of crystalline metal oxide nanowires involves multiple nucleation and coalescence via oxidation–reduction reactions at the molecular level. The preferential growth of nanowires parallel to the substrate enabled them to coalesce into regular polygonal networks. The individual segments of the polygonal network consist of both nanowires and nanotubules of β‐gallium oxide. Individual wire properties contribute to a nanoweb’s overall capacity and the implications for devices based on nanowebs are expected to be enormous.  相似文献   
73.
74.
Thirty-two consecutive patients with haematological disorders, in need of a permanent central venous catheter (CVC) were randomly allocated to have their CVC bandages (Tegaderm) changed once (OAW, n = 20) or twice (TAW, n = 19) a week. The two randomization arms were balanced in respect of age, sex, and underlying disease. The exit site of the CVC was inspected daily through the transparent bandage and erythema was noted. If severe erythema occurred, daily wet gauze dressings were applied. Samples for bacterial cultures were taken from the exit site of the CVC at every change of bandages. There was no difference in complications leading to removal of the CVC between the two groups (7/20 OAW vs. 7/19 TAW) or in CVC survival-time (P = 0.4). However, the OAW group had more positive CVC tip cultures (OAW 11/14 vs. TAW 2/9; P < 0.05) and a tendency to: (i) more extra dressings (P = 0.08); (ii) more cultures from the exit skin site showing high numbers of colony forming units (P = 0.07); (iii) shorter time to first exit site infection (P = 0.09); and (iv) more Gram-positive septicaemias (P = 0.08). Both clinical and bacteriological data in this study indicate that changing transparent polyurethane CVC bandages twice a week is superior to once a week.  相似文献   
75.
76.
77.
78.
Switched reluctance (SR) motors with differing structures are compared in terms of their torque prediction capabilities. The first structure is doubly salient with conventional laminations, also referred to as the CRS motor. The second has semiclosed stator slots and a cylindrical rotor with anisotropic magnetic properties arising from axial laminations interleaved with nonmagnetic material, also referred to as the CRR motor. The second structure has been claimed, on theoretical grounds, to be the superior structure in terms of torque per stator volume. The present comparison, based on RMS currents, concludes that the torque produced by the conventionally laminated motor is approximately 2.5 times that of the anisotropic design when the two copper losses are equalized. However, when the CRR motor has been optimized in terms of magnetic and electric loading, the CRS motor is still twice as torque productive. These results reverse the benefits previously claimed for the anisotropic motor design  相似文献   
79.
Antidepressant-induced adverse sexual effects are becoming more frequently reported by patients who require pharmacotherapy. A MED-LINE search was conducted to generate articles reporting such events. We report here on the sexual side effects associated with tricyclics, monoamine oxidase inhibitors including moclobemide, selective serotonin reuptake inhibitors, bupropion, and on the newer antidepressants venlafaxine and nefazadone. We conclude that adverse sexual effects are an increasingly important side effect of antidepressant medications, and patients must be routinely asked about their occurrence.  相似文献   
80.
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