全文获取类型
收费全文 | 114188篇 |
免费 | 24725篇 |
国内免费 | 1371篇 |
专业分类
电工技术 | 3224篇 |
综合类 | 2924篇 |
化学工业 | 49313篇 |
金属工艺 | 2027篇 |
机械仪表 | 2289篇 |
建筑科学 | 3227篇 |
矿业工程 | 1152篇 |
能源动力 | 3055篇 |
轻工业 | 27753篇 |
水利工程 | 487篇 |
石油天然气 | 3499篇 |
武器工业 | 72篇 |
无线电 | 9721篇 |
一般工业技术 | 19759篇 |
冶金工业 | 2909篇 |
原子能技术 | 481篇 |
自动化技术 | 8392篇 |
出版年
2024年 | 295篇 |
2023年 | 875篇 |
2022年 | 1910篇 |
2021年 | 2651篇 |
2020年 | 4747篇 |
2019年 | 7299篇 |
2018年 | 6494篇 |
2017年 | 7405篇 |
2016年 | 7361篇 |
2015年 | 7137篇 |
2014年 | 8112篇 |
2013年 | 9028篇 |
2012年 | 8681篇 |
2011年 | 8427篇 |
2010年 | 6465篇 |
2009年 | 6108篇 |
2008年 | 5626篇 |
2007年 | 6283篇 |
2006年 | 5816篇 |
2005年 | 4816篇 |
2004年 | 4219篇 |
2003年 | 3830篇 |
2002年 | 3522篇 |
2001年 | 2981篇 |
2000年 | 2724篇 |
1999年 | 1934篇 |
1998年 | 1046篇 |
1997年 | 788篇 |
1996年 | 699篇 |
1995年 | 569篇 |
1994年 | 508篇 |
1993年 | 424篇 |
1992年 | 324篇 |
1991年 | 265篇 |
1990年 | 191篇 |
1989年 | 122篇 |
1988年 | 81篇 |
1987年 | 101篇 |
1986年 | 76篇 |
1985年 | 82篇 |
1984年 | 76篇 |
1983年 | 39篇 |
1982年 | 27篇 |
1981年 | 20篇 |
1980年 | 33篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
202.
I. Tsukanov M. Hall 《International journal for numerical methods in engineering》2003,56(13):1949-1972
In this paper we discuss the data structure and algorithms for the direct application of generalized Leibnitz rules to the numerical computation of partial derivatives in forward mode. The proposed data structure provides constant time access to the partial derivatives, which accelerates the automatic differentiation computations. The interaction among elements of the data structure is explained by several numerical examples. The paper contains analysis of the developed data structure and algorithms. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
203.
X. Gong W. Ma J.C. Ostrowski K. Bechgaard G.C. Bazan A.J. Heeger S. Xiao D. Moses 《Advanced functional materials》2004,14(4):393-397
The electronic properties, carrier injection, and transport into poly(9,9‐dioctylfluorene) (PFO), PFO end‐capped with hole‐transporting moieties (HTM), PFO–HTM, and PFO end‐capped with electron‐transporting moieties (ETM), PFO–ETM, were investigated. The data demonstrate that charge injection and transport can be tuned by end‐capping with HTM and ETM, without significantly altering the electronic properties of the conjugated backbone. End‐capping with ETM resulted in more closely balanced charge injection and transport. Single‐layer electrophosphorescent light‐emitting diodes (LEDs), fabricated from PFO, PFO–HTM and PFO–ETM as hosts and tris[2,5‐bis‐2′‐(9′,9′‐dihexylfluorene)pyridine‐κ2NC3′]iridium(III ), Ir(HFP)3 as the guest, emitted red light with brightnesses of 2040 cd m–2, 1940 cd m–2 and 2490 cd m–2 at 290 mA cm–2 (16 V) and with luminance efficiencies of 1.4 cd A–1, 1.4 cd A–1 and 1.8 cd A–1 at 4.5 mA cm–2 for PFO, PFO–HTM, and PFO–ETM, respectively. 相似文献
204.
We have developed new photopolymers that have superior waterproof properties and that can easily interact with polyfunctional acrylate compounds, thus serving as hydrophobic photocrosslinking reagents. Acryloylmorpholine monomers whose homopolymers were less moisture absorbing than the usual water‐soluble polymers but were still water soluble to a good degree, were copolymerized with other acryloyl monomers. We then introduced the photosensitive (meth)acryloyl group to side chains of the resulting polymers. Among six copolymers examined, the copolymers composed of acryloyl morpholine, hydroxyethyl acrylate, ethyl, or methyl methacrylate, and methacryloyl isocyanate were found to have nicely balanced hydrophilicity and waterproof properties, in addition to good compatibility with hydrophobic photocrosslinking reagents. The composite polymers thus obtained were confirmed to be promising photopolymers usable even in a highly humid environment. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 684–692, 2003 相似文献
205.
206.
Polymer networks in which poly(propylene imine) dendrimers (Astramol?) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one‐step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino‐dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two‐step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino‐dendrimer, to form a star‐like, acrylate‐terminated polyTHF multi‐macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end‐groups and unreacted amino‐groups of the dendrimer. This cross‐linking reaction occurred spontaneously upon heating of the solution of the multi‐macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films. © 2003 Society of Chemical Industry 相似文献
207.
208.
209.
The effect of humidity during storage on the crosslinking reactions of isocyanate groups was investigated with attenuated total reflectance Fourier transform infrared spectroscopy with pressure‐sensitive adhesives composed of poly[ethyl acrylate‐co‐(2‐ethylhexyl acrylate)‐co‐(2‐hydroxyethyl methacrylate)] as a base resin and polyisocyanate as a crosslinker. A peak‐resolving analysis of the amide II region revealed four bands. According to an analysis of the Fourier transform infrared spectra of the model compounds, these four bands were assigned to free urethane linkages, hydrogen‐bonded urethane linkages, free urea linkages, and hydrogen‐bonded urea linkages. As expected, storage under humid conditions led to the formation of free and hydrogen‐bonded urea linkages corresponding to the promotion of isocyanate consumption. Peak resolution of the amide II region was found to be a reasonable way of monitoring urethane and urea linkages during crosslinking reactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3039–3045, 2003 相似文献
210.