全文获取类型
收费全文 | 622619篇 |
免费 | 53861篇 |
国内免费 | 24005篇 |
专业分类
电工技术 | 34204篇 |
技术理论 | 70篇 |
综合类 | 40017篇 |
化学工业 | 111976篇 |
金属工艺 | 33837篇 |
机械仪表 | 38132篇 |
建筑科学 | 48977篇 |
矿业工程 | 19598篇 |
能源动力 | 16618篇 |
轻工业 | 43391篇 |
水利工程 | 11113篇 |
石油天然气 | 39427篇 |
武器工业 | 4657篇 |
无线电 | 68885篇 |
一般工业技术 | 73839篇 |
冶金工业 | 31425篇 |
原子能技术 | 5760篇 |
自动化技术 | 78559篇 |
出版年
2024年 | 2290篇 |
2023年 | 8444篇 |
2022年 | 15304篇 |
2021年 | 21990篇 |
2020年 | 17554篇 |
2019年 | 15858篇 |
2018年 | 17881篇 |
2017年 | 20430篇 |
2016年 | 19042篇 |
2015年 | 25432篇 |
2014年 | 31313篇 |
2013年 | 38055篇 |
2012年 | 38728篇 |
2011年 | 42517篇 |
2010年 | 38002篇 |
2009年 | 35964篇 |
2008年 | 34953篇 |
2007年 | 33769篇 |
2006年 | 34773篇 |
2005年 | 30796篇 |
2004年 | 20770篇 |
2003年 | 18566篇 |
2002年 | 17402篇 |
2001年 | 15587篇 |
2000年 | 15837篇 |
1999年 | 17079篇 |
1998年 | 13187篇 |
1997年 | 11225篇 |
1996年 | 10536篇 |
1995年 | 8737篇 |
1994年 | 7217篇 |
1993年 | 4974篇 |
1992年 | 3991篇 |
1991年 | 3009篇 |
1990年 | 2285篇 |
1989年 | 1855篇 |
1988年 | 1505篇 |
1987年 | 978篇 |
1986年 | 757篇 |
1985年 | 498篇 |
1984年 | 370篇 |
1983年 | 268篇 |
1982年 | 236篇 |
1981年 | 154篇 |
1980年 | 152篇 |
1979年 | 64篇 |
1978年 | 20篇 |
1977年 | 24篇 |
1976年 | 28篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
201.
The authors reply to the comments by Koppelaar and Tolhuizen (see ibid. vol.46, no.9, p.573, 1998). They state that the optimum choice of the slopes used to perform the encoding process in a projection code always results in maximizing the minimum Hamming distance so that d=2 r 相似文献
202.
203.
TiNi shape memory alloys prepared by normal sintering 总被引:4,自引:0,他引:4
Ning Zhang P. Babayan Khosrovabadi J. H. Lindenhovius B. H. Kolster 《Materials Science and Engineering: A》1992,150(2):263-270
This paper covers the use of conventional press and sinter of titanium and nickel equiatomic blends, involving transient liquid phases. A notable development has been the fabrication of homogeneous compacts from the elemental powders. Results indicate that employment of a double-stage sintering cycle is effective to sustain the geometrical integrity of the sintered sample. The TiNi alloy prepared in this manner exhibits a recovery strain of 4.6% by generating a restoring stress of 230 MPa, with a martensitic transformation point Ms of 34 °C. 相似文献
204.
205.
A model in which jointly optimal stocks of material and finished products are to be chosen is reexamined. While it costs less to hold material, a certain percentage of the random demand not immediately satisfied by previously finished products is lost. We pay particular attention to the dependence of the optimal stocks on the initial ones, which assumes an interesting form. For example, if the stock of finished products is high but the combined stock is low, die quantity of material ordered depends on the stock of finished products. 相似文献
206.
本文讨论了温度、搅拌和时间三要素对感光乳剂和工艺过程的影响,指出了上述影响的后果和严格过程控制的重要性,提出克服影响的措施。 相似文献
207.
特征X射线能谱法测定Fe^+注入小麦种子的深度 总被引:5,自引:2,他引:3
用110keV Fe^+离子束垂直注入小麦种胚后,在扫描电子显微镜上沿种子纵沟剖面,在不同深度上测量Fe元素被激发出的特征X射线强度分布,结果表明分布呈指数衰减,与晶体中的热扩散分布相类似,并对此进行了讨论。 相似文献
208.
2,3,4- or 2,3,5-trisubstituted furans were highly regioselectively formed from the cycloisomerization reaction of the same starting cyclopropenes 1 via the subtle choice of the transition metal halides. Under the catalysis of 5 mol % PdCl2(CH3CN)2, 2,3,5-trisubstituted furans 2 were given in 50-88% yields with 95-99% regioselectivities, while 2,3,4-trisubstituted furans 3 were formed in 78-96% yields with 99% regioselectivities under the catalysis of 5 mol % CuI. 相似文献
209.
J. Weise Dr.‐Ing. O. Yezerska M. Busse M. Haesche V. Zanetti‐Bueckmann M. Schmitt 《Materialwissenschaft und Werkstofftechnik》2007,38(11):901-906
Micro‐porous syntactic foams were produced by means of integration of glass bubbles into aluminium and zinc matrices. Preforms of glass bubbles were pressure infiltrated with the alloys AlSi9Cu9 ans ZnAl4Cu using squeeze casting. The preforms were sintered thermically without the use of bonding agents. Using the combination of different sintering steps syntactic foams with locally different densities could be produced. The mechanical properties of the foams were tested indicating a high compression strength of the foams and a very good compression energy absorption. Furthermore, corrosion behaviour and behaviour at higher temperatures were investigated. 相似文献
210.
We define the very rich language of composed conditionals on a three‐valued logic and use this language as the communication tool between man and machine. Communication takes place for three reasons: knowledge acquisition, query, and response. Learning, thinking, and answering questions are of a pure information theoretical nature. The pivot of this knowledge processing concept is the amount of information (bit) we receive if a conditional becomes true. We follow an axiomatic approach to information theory rather than the classical probabilistic approach of Shannon; information comes first, and then comes probability. In the light of this philosophy, query and response experience new interpretations. Both, acquisition and response are realized by maximizing entropy and minimizing relative entropy, respectively. The iterative solution of these mathematical optimization problems gives new insights into the adaptation of prior knowledge to new information. Our expert system shell SPIRIT supports this kind of knowledge processing, which will be established by suitable examples. © 2003 Wiley Periodicals, Inc. 相似文献