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   376563篇
  免费   28511篇
  国内免费   15924篇
电工技术   22107篇
技术理论   56篇
综合类   23756篇
化学工业   62340篇
金属工艺   21029篇
机械仪表   24290篇
建筑科学   29266篇
矿业工程   12247篇
能源动力   11133篇
轻工业   21551篇
水利工程   6321篇
石油天然气   24757篇
武器工业   3347篇
无线电   42071篇
一般工业技术   44016篇
冶金工业   19905篇
原子能技术   3844篇
自动化技术   48962篇
  2024年   1483篇
  2023年   5738篇
  2022年   9964篇
  2021年   14221篇
  2020年   11079篇
  2019年   9006篇
  2018年   10293篇
  2017年   11664篇
  2016年   10461篇
  2015年   14093篇
  2014年   18185篇
  2013年   22010篇
  2012年   23349篇
  2011年   25827篇
  2010年   22547篇
  2009年   21623篇
  2008年   21144篇
  2007年   20434篇
  2006年   21114篇
  2005年   18413篇
  2004年   12138篇
  2003年   10754篇
  2002年   9838篇
  2001年   8998篇
  2000年   9063篇
  1999年   10357篇
  1998年   8564篇
  1997年   7094篇
  1996年   6657篇
  1995年   5581篇
  1994年   4565篇
  1993年   3258篇
  1992年   2630篇
  1991年   2035篇
  1990年   1584篇
  1989年   1287篇
  1988年   1060篇
  1987年   703篇
  1986年   561篇
  1985年   361篇
  1984年   248篇
  1983年   212篇
  1982年   208篇
  1981年   138篇
  1980年   136篇
  1979年   71篇
  1978年   34篇
  1977年   39篇
  1976年   58篇
  1975年   20篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
沈忠士  王希龄 《钢铁研究》1995,(2):47-49,35
重点介绍了武钢热冷连轧计算机轧制工艺数学模型,武钢数模的开发创新使用情况及其取得的经济效益和社会效益。  相似文献   
162.
在工业生产条件下,对影响HPb59-1水平连铸律材热轧开裂的熔铸工艺进行了试验研究.取三个熔铸工艺因素:铸造速度、冷却水压力、冷却水温度.试验结果表明;铸造速度对热轧开裂影响极为显著,使其控制在410mm/min左右可获得较为理想的效果.  相似文献   
163.
164.
The effects of epithelial removal and cyclooxygenase inhibition on contractions induced by exogenous acetylcholine (ACh) and electrical field stimulation (EFS) were evaluated in horse tracheal strips and bronchial rings. Epithelial removal potentiated the response to ACh but had no influence on the response to EFS. The effect of epithelial removal was not altered by pretreating the tissues with meclofenamate, a cyclooxygenase inhibitor. In trachealis strips, meclofenamate augmented contractions induced by EFS but not by ACh. In bronchial rings, meclofenamate augmented EFS-induced contraction to a greater extent than ACh-induced contraction. These effects of meclofenamate were epithelium-independent. We conclude that horse airway epithelium produces a relaxant factor that is not a prostanoid. Endogenous prostanoids originating from non-epithelial sites inhibit only cholinergic nerves in the trachea but both parasympathetic nerves and smooth muscle in the bronchi.  相似文献   
165.
In this study we examined the effects of retinol (ROH), a metabolic precursor of retinoic acid (RA), on Staphylococcus aureus Cowan I (SAC)-induced immunoglobulin synthesis of cord blood mononuclear cells (CBMC) and adult peripheral blood mononuclear cells (PBMC). ROH augmented SAC-induced IgM synthesis of CBMC by 5.9 +/- 1.5-fold (n = 7, mean +/- s.d.), and IgG synthesis of adult PBMC by 16.3 +/- 5.1-fold (n = 3) at optimal concentrations of 10(-6) M and 10(-11) M, respectively. No augmenting effects could be demonstrated for the other immunoglobulin isotypes. Time-course studies showed that the synthesis of IgM by CBMC was accelerated with detectable immunoglobulin in supernatant fluids starting on day 3. ROH augmented immunoglobulin synthesis of CBMC stimulated by Epstein-Barr virus (EBV), a T cell-independent polyclonal activator, and of EBV-transformed B cell clones (2.5 +/- 0.2 and 4.1 +/- 1.5-fold increase, respectively), which suggests that ROH can act directly on B cells to enhance immunoglobulin synthesis. In contrast, when ROH was preincubated with cord blood T cells, washed and added to the B cell-enriched fraction with SAC, no increase (0.9-1.8-fold) in IgM synthesis was obtained. Thus, the principal mechanism(s) by which ROH augments immunoglobulin synthesis is by acting on B cells. This is in contrast to the immunoglobulin-enhancing effects of RA which is mediated by T cells, or T cell products, e.g. cytokine. Our studies suggest that RA and ROH may have different pathways of immunoglobulin-enhancing effects, perhaps mediated by different retinoid binding proteins resulting in gene activation and immunoglobulin synthesis.  相似文献   
166.
A crucial step in manufacturing microcircuits is the wire bonding process in which a very thin gold wire must be formed to connect two surfaces in the microcircuit. The quality of the wire bond can be measured by visual inspection and a pull test—both of which are high-reliability, high-cost approaches to statistical process control. Westinghouse wanted to develop a high-reliability, low-cost quality assurance system. In this paper, we report on a year-long study to construct a neural network model that is capable of predicting the quality of wire bonds. The results of our modeling efforts reveal that neural networks are useful tools for statistical process control problems.  相似文献   
167.
郭士伦  郝秀红 《核技术》1995,18(2):85-89
介绍了液体通过核孔膜规律方面取得的新认识,包括:(1)纯净液体通过核孔膜的规律;(2)核孔膜测定液体粘滞系数的各种方法;(3)各种物质溶液浓度的核孔膜测定;(4)液相混合物快速分离和化学分离;(5)流体中固体微粒对核孔膜的堵塞及其公式;(6)用核孔膜滤除液中各各斩规律。  相似文献   
168.
The present study was undertaken to evaluate the postoperative relapse from the period of unwiring to 1 year postoperatively and its correlation to the amount of mandibular setback and change in vertical dimension after mandibular bilateral sagittal split osteotomy. Twenty-seven patients were evaluated cephalometrically by the time preoperatively, 6 weeks, 6 months and 1 year postoperatively. It was found that 1) the average amount of mandibular setback at pogonion point, 6 weeks postoperatively, is 7.6mm backward and 1.9mm downward, 2) the average amount of horizontal relapse at pogonion point, 6 months and 1 year postoperatively, are 1.9mm and 2.3mm respectively. 86% of the horizontal relapse, 1 year postoperatively, occurs in the first 6 months after removal of intermaxillary fixation, 3) the average amount of vertical relapse at pogonion point, 6 months and 1 year postoperatively, are 0.9mm and 1.1mm upward. 82% of the vertical relapse, 1 year postoperatively, occurs in the first 6 months after removal of intermaxillary fixation, 4) the amount of 1 year postoperatively horizontal relapse is significantly correlated both with the amount of horizontal mandibular set back and vertical downward change (r = 0.58, 0.67, p < 0.001), whereas the amount of vertical relapse is with the vertical downward change only, but horizontal setback isn't.  相似文献   
169.
振动对火箭炮密集度影响研究   总被引:2,自引:0,他引:2  
潘宏侠  赵剡 《兵工学报》1993,14(4):17-22
  相似文献   
170.
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