全文获取类型
收费全文 | 374880篇 |
免费 | 24905篇 |
国内免费 | 12700篇 |
专业分类
电工技术 | 18450篇 |
技术理论 | 56篇 |
综合类 | 20231篇 |
化学工业 | 60890篇 |
金属工艺 | 19115篇 |
机械仪表 | 22018篇 |
建筑科学 | 26522篇 |
矿业工程 | 11352篇 |
能源动力 | 10156篇 |
轻工业 | 20634篇 |
水利工程 | 5862篇 |
石油天然气 | 23023篇 |
武器工业 | 2603篇 |
无线电 | 38420篇 |
一般工业技术 | 42991篇 |
冶金工业 | 39681篇 |
原子能技术 | 3398篇 |
自动化技术 | 47083篇 |
出版年
2024年 | 1345篇 |
2023年 | 5397篇 |
2022年 | 8981篇 |
2021年 | 12614篇 |
2020年 | 9832篇 |
2019年 | 8054篇 |
2018年 | 9607篇 |
2017年 | 11007篇 |
2016年 | 10242篇 |
2015年 | 12960篇 |
2014年 | 16268篇 |
2013年 | 19569篇 |
2012年 | 22267篇 |
2011年 | 24793篇 |
2010年 | 19849篇 |
2009年 | 19063篇 |
2008年 | 18559篇 |
2007年 | 18009篇 |
2006年 | 18827篇 |
2005年 | 19327篇 |
2004年 | 12828篇 |
2003年 | 11110篇 |
2002年 | 8945篇 |
2001年 | 8193篇 |
2000年 | 8277篇 |
1999年 | 10263篇 |
1998年 | 14271篇 |
1997年 | 10556篇 |
1996年 | 8845篇 |
1995年 | 6777篇 |
1994年 | 5441篇 |
1993年 | 4182篇 |
1992年 | 2731篇 |
1991年 | 2259篇 |
1990年 | 1802篇 |
1989年 | 1504篇 |
1988年 | 1307篇 |
1987年 | 900篇 |
1986年 | 732篇 |
1985年 | 508篇 |
1984年 | 311篇 |
1983年 | 284篇 |
1982年 | 323篇 |
1981年 | 304篇 |
1980年 | 320篇 |
1979年 | 126篇 |
1978年 | 130篇 |
1977年 | 646篇 |
1976年 | 1374篇 |
1975年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Weight smoothing to improve network generalization 总被引:2,自引:0,他引:2
A weight smoothing algorithm is proposed in this paper to improve a neural network's generalization capability. The algorithm can be used when the data patterns to be classified are presented on an n-dimensional grid (n>/=1) and there exists some correlations among neighboring data points within a pattern. For a fully-interconnected feedforward net, no such correlation information is embedded into the architecture. Consequently, the correlations can only be extracted through sufficient amount of network training. With the proposed algorithm, a smoothing constraint is incorporated into the objective function of backpropagation to reflect the neighborhood correlations and to seek those solutions that have smooth connection weights. Experiments were performed on problems of waveform classification, multifont alphanumeric character recognition, and handwritten numeral recognition. The results indicate that (1) networks trained with the algorithm do have smooth connection weights, and (2) they generalize better. 相似文献
112.
利用TM资料测量毛乌素沙地面积的方法和结果 总被引:1,自引:0,他引:1
利用1:25万陆地卫星TM资料和地形图,在GIS支持下,建立毛乌素沙地图形数据库,对毛乌素沙地目前流沙分布的范围进行了调查研究。重.资、介绍了利用陆地卫星TM资料对毛乌素沙地的面积进行测童计算的技术和方法,给出了最新测贡得到的毛乌素沙地全区总面积和分布于各旗县的沙地面积数据。 相似文献
113.
Shouhong Wang 《Information Systems Management》1994,11(2):36-43
Business reengineering requires new systems analysis tools for process modeling. An object-oriented (OO) approach may be better than the traditional data flow diagram method in modeling business processes. This article explains the development of an OO tool that may potentially benefit IS in reengineering business processes. 相似文献
114.
AL Jensen MK Thomsen H Aaes M Andreasen J S?ndergaard 《Canadian Metallurgical Quarterly》1993,37(3-4):329-336
Growth hormone (GH) has recently been shown to affect polymorphonuclear neutrophil granulocyte (PMN) function and to be secreted by mononuclear cells, indicating that the hormone may be active in an immunophysiologic network, acting as an endo- or paracrine priming agent. The purpose of the present study was to evaluate the chemotactic responsiveness of canine peripheral PMN in a dog with acromegaly, caused by spontaneous, progesterone-induced hypersecretion of GH and, secondary to this, a seven-fold increase in insulin-like growth factor I (IGF-I). The chemotactic responsiveness towards zymosan-activated serum (ZAS) and leukotriene B4 (LTB4) was evaluated at a time when the dog suffered from acromegaly and again 57 days after corrective surgery (ovariohysterectomy). The experiments showed that PMN from the patient exhibited enhanced chemotactic migration that appeared to be associated with the hypersomatotropic condition as judged from the reversibility of the phenomenon. The glucose intolerance and elevated serum alkaline phosphatase that were observed in the acromegalic dog were also shown to be reversible following surgery. 相似文献
115.
The effects of adenosine and sodium nitroprusside (SNP) on central hemodynamics and myocardial blood flow and metabolism were investigated postoperatively after elective coronary artery bypass (CABG) surgery in ten sedated and mechanically ventilated patients in the intensive care unit. During three consecutive 15-min periods, SNP (0.8 +/- 0.1 micrograms.kg-1 x min-1), adenosine (88.9 +/- 13.3 micrograms.kg-1 x min-1), and then again SNP (0.7 +/- 0.1 micrograms.kg-1 x min-1) were infused to control postoperative hypertension at a mean arterial pressure of approximately 80 mm Hg. Systemic and pulmonary hemodynamics and global (coronary sinus flow, CSF) as well as regional (great cardiac vein flow, GCVF) myocardial blood flow and metabolic variables were measured. During adenosine infusion, in comparison to SNP, heart rate was unchanged, stroke volume index and cardiac index increased (24% and 32%, respectively), and the systemic vascular resistance index decreased (-26%). Mean pulmonary arterial pressure (24%) as well as pulmonary capillary wedge pressure (27%) and central venous pressure (18%) were higher with adenosine compared to SNP. Adenosine also increased CSF and GCVF (108% and 103%, respectively) without altering the CSF/GCVF flow ratio compared to SNP. Furthermore, adenosine increased the coronary oxygen content (51%) and decreased the arterio-great cardiac vein oxygen content difference (-48%) without changing regional myocardial oxygen consumption, indicating a more pronounced hyperkinetic myocardial circulation compared to SNP. In addition, adenosine infusion decreased arterial PO2 (-11%) and increased the intrapulmonary shunt fraction (57%). The PR interval time of the electrocardiogram was prolonged (12%) and the ST segment was more depressed during adenosine infusion compared to SNP.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
116.
A G?rling 《Canadian Metallurgical Quarterly》1993,47(4):2783-2799
117.
118.
EEPROM的参数设置控制着系统的基本功能,设置的改变对系统的起动和运行起着重要作用。本文详细地列出了EEPROM的地址分配表,并通过上机实验对那些重要的地址了详细的说明。 相似文献
119.
The preembedding double immunoreaction method was used to study interrelations of enkephalinergic and GABAergic neuronal elements in the dorsal raphe nucleus of the Wistar albino rat. The enkephalin-like neuronal elements were immunoreacted by the peroxidase-antiperoxidase method and silver-gold intensified, which showed strongly and was specific. The GABA-like immunoreactive neurons were immunoreacted by the peroxidase-antiperoxidase method only. GABA-like neural somata were postsynaptic to both the enkephalin-like immunoreactive and the non-immunoreactive axon terminals. The enkephalin-like immunoreactive axon terminals were also found to synapse GABA-like immunoreactive dendrites. The GABA-like immunoreactive neuronal elements were also found to receive synapses from other non-immunoreactive as well as GABA-like immunoreactive axon terminals. Almost all of the synapses appeared to be asymmetrical. Possible functional activity of interactions among the enkephalinergic, GABAergic, and serotonergic neuronal elements in the dorsal raphe nucleus are discussed. 相似文献
120.