全文获取类型
收费全文 | 376563篇 |
免费 | 28511篇 |
国内免费 | 15924篇 |
专业分类
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 |
出版年
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.
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.
Qiwen Wang Xiaoyun Sun Bruce L. Golden Lenore Desilets Edward A. wasil Scott Luco Adam Peck 《Computers & Operations Research》1993,20(8)
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.
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.
170.