全文获取类型
收费全文 | 1211篇 |
免费 | 22篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 16篇 |
综合类 | 4篇 |
化学工业 | 62篇 |
金属工艺 | 34篇 |
机械仪表 | 24篇 |
建筑科学 | 7篇 |
能源动力 | 8篇 |
轻工业 | 39篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 107篇 |
一般工业技术 | 97篇 |
冶金工业 | 751篇 |
原子能技术 | 6篇 |
自动化技术 | 76篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 11篇 |
2013年 | 32篇 |
2012年 | 23篇 |
2011年 | 25篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 22篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 13篇 |
2004年 | 12篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 41篇 |
1998年 | 242篇 |
1997年 | 156篇 |
1996年 | 99篇 |
1995年 | 40篇 |
1994年 | 53篇 |
1993年 | 38篇 |
1992年 | 7篇 |
1991年 | 14篇 |
1990年 | 16篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1977年 | 16篇 |
1976年 | 40篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有1236条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
HJ Lee HK Ha MH Kim YK Jeong PN Kim MG Lee JS Kim DJ Suh SG Lee YI Min YH Auh 《Canadian Metallurgical Quarterly》1997,169(2):517-520
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers. 相似文献
5.
6.
A chimeric dopamine transporter (DAT) cDNA encoding mutant human DAT (hDAT) protein in which the intracellular carboxyl-terminal tail is replaced by that of the bovine dopamine transporter (bDAT) was constructed. The chimeric hDAT cDNA was expressed in COS-7 cells, and [3H]dopamine and [3H]MPP+ uptake and [3H]CFT binding capacities were assessed. Substrate transport and ligand binding of bDAT were reduced by 32-43% as a result of substitution of the carboxyl tail in hDAT, suggesting that the functional characteristics of bDAT arise from differences in the carboxyl tail between human and bovine DAT. Thus, it appears that the sequences encoded within the carboxyl terminal of DAT would be one of the important determinants for its functions. 相似文献
7.
Watermarking for intellectual property protection 总被引:1,自引:0,他引:1
A new watermarking method for intellectual property (IP) protection is presented. The proposed method uses a uniquely generated stream of bits, known as a watermark, embedded into the self-test circuit to represent ownership. This scheme can detect the ownership rights of the IP provider even when the chip has been packaged. Experimental results show the proposed embedding technique can survive synthesis, placement and routing. The experimental results are given to demonstrate the proposed method. 相似文献
8.
Juin-Hung Chen Hen-Wai Tsao 《Lightwave Technology, Journal of》1998,16(7):1137-1148
This paper presents a design method of optical frequency modulation (FM) subcarrier (with super carrier) transmission modem. The nonideal link characteristics, including laser chirping, fiber dispersion, voltage controlled oscillator (VCO) phase noise, relative intensity noise (RIN), and equivalent network model of laser diode of such a system that may bring about signal distortion are discussed first. We then propose a hierarchical methods to establish the system equivalent model. Finally this FM modem is applied to a GSM wireless system, in which multichannel signals are transmitted over fiber between radio port and basestation, and system performance is appraised by its dynamic range. It is found that optical FM subcarrier (with super carrier) transmission technique can improve the system dynamic range, compared with the intensity modulated direct detection (IMDD) method, and this is a economical and efficient method 相似文献
9.
The antinociceptive effects of morphine (5 micrograms) microinjected into the ventrolateral periaqueductal gray were determined using both the tail flick and the foot withdrawal responses to noxious radiant heating in lightly anesthetized rats. Intrathecal injection of appropriate antagonists was used to determine whether the antinociceptive effects of morphine were mediated by alpha 2-noradrenergic, serotonergic, opioid, or cholinergic muscarinic receptors. The increase in the foot withdrawal response latency produced by microinjection of morphine in the ventrolateral periaqueductal gray was reversed by intrathecal injection of the cholinergic muscarinic receptor antagonist atropine, but was not affected by the alpha 2-adrenoceptor antagonist yohimbine, the serotonergic receptor antagonist methysergide, or the opioid receptor antagonist naloxone. In contrast, the increase in the tail flick response latency produced by morphine was reduced by either yohimbine, methysergide or atropine. These results indicate that microinjection of morphine in the ventrolateral periaqueductal gray inhibits nociceptive responses to noxious heating of the tail by activating descending neuronal systems that are different from those that inhibits the nociceptive responses to noxious heating of the feet. More specifically, serotonergic, muscarinic cholinergic and alpha 2-noradrenergic receptors appear to mediate the antinociception produced by morphine using the tail flick test. In contrast, muscarinic cholinergic, but not monoamine receptors appear to mediate the antinociceptive effects of morphine using the foot withdrawal response. 相似文献
10.
SB Levery MS Toledo E Suzuki ME Salyan S Hakomori AH Straus HK Takahashi 《Canadian Metallurgical Quarterly》1996,222(2):639-645
An acidic glycolipid (Band 1), purified from P. brasiliensis by a combination of ion exchange chromatography, HPLC, and HPTLC, was found to be reactive with sera of all patients with paracoccidioidomycosis (PCM). Monosaccharide analysis of Band 1 yielded mannose and galactose in a 2:1 ratio, while mild acid hydrolysis and mild periodate oxidation/NaB3H4 reduction indicated the presence of a terminal galactofuranose. Preliminary analysis of 1H-NMR and MS data suggests that the structure of the glycan is Galf beta 1-->6(Manp alpha 1-->3)Manp beta 1-->2Ins (Ins = myo-inositol). Removal of the galacto-furanose decreased by 60-80% the reactivity of sera from PCM patients with Band 1, suggesting that this residue is immunodominant. With the presumed absence of galactofuranose in mammalian hosts, compounds containing this residue may be useful targets for therapy of several parasitic and fungal diseases. 相似文献