全文获取类型
收费全文 | 130470篇 |
免费 | 12426篇 |
国内免费 | 7308篇 |
专业分类
电工技术 | 9420篇 |
技术理论 | 2篇 |
综合类 | 9796篇 |
化学工业 | 18816篇 |
金属工艺 | 7601篇 |
机械仪表 | 8041篇 |
建筑科学 | 9712篇 |
矿业工程 | 3589篇 |
能源动力 | 3615篇 |
轻工业 | 12138篇 |
水利工程 | 3411篇 |
石油天然气 | 5171篇 |
武器工业 | 1264篇 |
无线电 | 16264篇 |
一般工业技术 | 15002篇 |
冶金工业 | 6155篇 |
原子能技术 | 1717篇 |
自动化技术 | 18490篇 |
出版年
2024年 | 674篇 |
2023年 | 2127篇 |
2022年 | 4227篇 |
2021年 | 5729篇 |
2020年 | 4131篇 |
2019年 | 3162篇 |
2018年 | 3466篇 |
2017年 | 4052篇 |
2016年 | 3604篇 |
2015年 | 5179篇 |
2014年 | 6725篇 |
2013年 | 8239篇 |
2012年 | 9302篇 |
2011年 | 10046篇 |
2010年 | 9167篇 |
2009年 | 8874篇 |
2008年 | 8786篇 |
2007年 | 8409篇 |
2006年 | 7768篇 |
2005年 | 6393篇 |
2004年 | 4441篇 |
2003年 | 3364篇 |
2002年 | 3387篇 |
2001年 | 2923篇 |
2000年 | 2645篇 |
1999年 | 2203篇 |
1998年 | 1876篇 |
1997年 | 1623篇 |
1996年 | 1449篇 |
1995年 | 1219篇 |
1994年 | 954篇 |
1993年 | 794篇 |
1992年 | 632篇 |
1991年 | 475篇 |
1990年 | 400篇 |
1989年 | 316篇 |
1988年 | 262篇 |
1987年 | 193篇 |
1986年 | 159篇 |
1985年 | 140篇 |
1984年 | 102篇 |
1983年 | 77篇 |
1982年 | 73篇 |
1981年 | 72篇 |
1980年 | 64篇 |
1979年 | 46篇 |
1978年 | 32篇 |
1977年 | 33篇 |
1976年 | 54篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO2 : O2 : N2 = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
Chun-Tsen Lu Kun-Wei Lin Huey-Ing Chen Hung-Ming Chuang Chun-Yuan Chen Wen-Chau Liu 《Electron Device Letters, IEEE》2003,24(6):390-392
A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated. 相似文献
3.
In this study, the effect and side-effect of epidural injection with lappaconitine compound for post-operative analgesia was observed. One hundred and twenty patients were randomly divided into 4 groups. Lappaconitine compound (LB) consisted of 12 mg of lappaconitine and 22.5 mg of bupivacaine, was given to group A (the group of observation), and lappaconitine 12 mg, bupivacaine 22.5 mg and morphine 2 mg to group B, C and D respectively for control. All were given by epidural injection with single blind method during post-operative pain of incision operation. Result showed that the initiating of analgesia was quicker in group A and C than that in group B and D, and the efficacy was group D > A > C > B. There was significant difference between group A and B in the above two parameters, P < 0.01 and P < 0.05. The analgisia maintenence time of single injection was D > A > B > C, that of group D was significantly longer than that of group A (P < 0.01). It indicated that the epidural injection with LB was more rapid and potent than that with lappaconitine alone in post-operative analgesia, and the former had no side-effect, it was safer than morphine. 相似文献
4.
5.
Horng-Dar Lin 《Circuits and Devices Magazine, IEEE》1995,11(4):25-31
Identifies the basic technological components of multimedia communications. Among these technologies, multimedia processing and transmission already benefit heavily from VLSI advances. in fact, these two technologies could not have matured without special-purpose VLSI chips. We have examined basic processing required in these technologies and some VLSI architectures. The focus has been on standard-compliant VLSI chips, because the eventual goal of communications is to allow everyone to reach others without constraints. There are still a number of evolving standards, which means that we might witness yet another wave of VLSI chips for multimedia communications 相似文献
6.
本文用计算机数字模拟方法研究了电活性分子多层Z型L-B膜修饰电极的循环伏安行为。计算了电极与修饰L-B膜分子第一层之间的电荷转移速度常数K_o,L-B膜分子层间的电荷转移速度常数k_i;对峰电位差△E_p及阳极峰面积Q的影响,以及在不同条件下各层分子的氧化态分数随扫描时间的变化。为研究和设计电活性分子修饰电极的实际体系提供了大量数据和信息。 相似文献
7.
本文提出新型布线算法,集李氏迷宫法与线搜索法的长处为一体,以饱和带法进行动态排序,以线搜索法确定借孔位置,然后用李氏法进行单层布线,获得最佳路径,从而达到线型好,布通率高的效果。 相似文献
8.
On the magnetic-wall approximation for their slots, shielded coplanar waveguides (SCPWs) and semienclosed CPWs (SECPWs) are analyzed through an intensive use of elliptic function transformation. CAD-oriented formulas for the quasi-TEM parameters of SCPWs and SECPWs, including their coupled versions, are derived. The comparison of the results calculated here with previous ones show 2% accuracy for formulas in the practical situation where the slots are not too wide, e.g., s / (s + 2w) ≥ 0.2 for an SCPW. © 1994 John Wiley & Sons, Inc. 相似文献
9.
10.