全文获取类型
收费全文 | 21876篇 |
免费 | 2604篇 |
国内免费 | 1383篇 |
专业分类
电工技术 | 2437篇 |
综合类 | 2223篇 |
化学工业 | 2926篇 |
金属工艺 | 1522篇 |
机械仪表 | 2455篇 |
建筑科学 | 2157篇 |
矿业工程 | 871篇 |
能源动力 | 931篇 |
轻工业 | 1030篇 |
水利工程 | 560篇 |
石油天然气 | 731篇 |
武器工业 | 250篇 |
无线电 | 2642篇 |
一般工业技术 | 1910篇 |
冶金工业 | 762篇 |
原子能技术 | 221篇 |
自动化技术 | 2235篇 |
出版年
2024年 | 97篇 |
2023年 | 332篇 |
2022年 | 572篇 |
2021年 | 697篇 |
2020年 | 713篇 |
2019年 | 635篇 |
2018年 | 560篇 |
2017年 | 756篇 |
2016年 | 842篇 |
2015年 | 921篇 |
2014年 | 1464篇 |
2013年 | 1336篇 |
2012年 | 1659篇 |
2011年 | 1790篇 |
2010年 | 1331篇 |
2009年 | 1327篇 |
2008年 | 1227篇 |
2007年 | 1517篇 |
2006年 | 1376篇 |
2005年 | 1072篇 |
2004年 | 900篇 |
2003年 | 772篇 |
2002年 | 692篇 |
2001年 | 645篇 |
2000年 | 515篇 |
1999年 | 432篇 |
1998年 | 314篇 |
1997年 | 239篇 |
1996年 | 228篇 |
1995年 | 200篇 |
1994年 | 155篇 |
1993年 | 136篇 |
1992年 | 89篇 |
1991年 | 70篇 |
1990年 | 66篇 |
1989年 | 58篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1959年 | 5篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
A capillary switch is a system of two liquid drops, one sessile and the other pendant, obtained by overfilling a hole of radius R in a plate. When surface tension dominates gravity, the equilibrium shapes of the drops are spherical sections of equal radii. If the combined volume of the top VT and bottom VB drops exceeds , the system has three equilibrium states of which two are stable. This bistability is exploited in applications by toggling the system between its two stable states. Here, we examine the effectiveness of using an electric field for toggling. Bifurcation diagrams are obtained that depict how the system's response varies with applied field strength E, and show loss of stability at turning points and the possibility of hysteresis. A phase diagram in space is presented to readily infer when an electric field is an effective means for toggling. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1451–1459, 2014 相似文献
952.
Preparation and properties of polyamide‐6‐based thermoplastic laminate composites by a novel in‐mold polymerization technique
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nadya Dencheva Ana S. Sampaio Filipa M. Oliveira António S. Pouzada Antonio M. Brito Zlatan Denchev 《应用聚合物科学杂志》2014,131(8)
In this work, a method for preparation of polyamide‐6 (PA6) based laminates reinforced by glass fiber‐ (GFL) or polyamide‐66 (PA66) textile structures (PL) via reactive injection molding is disclosed. It is based on in‐mold anionic polymerization of ε‐caprolactam carried out at 165°C in the presence of the respective reinforcements performed in newly developed prototype equipment whose design concept and operation are described. Both composite types were produced for reaction times of 20 min, with conversion degrees of 97–99%. Initial mechanical tests in tension of GFL samples displayed almost twofold increase of the Young's modulus and stress at break values when compared with the neat anionic PA6. The improvement was proportional to the volume fraction Vf of glass fiber fabric that was varied in the 0.16–0.25 range. A 300% growth of the impact strength was registered in PL composites with Vf of PA66 textile of 0.1. Removing the surface finish of the latter was found to be a factor for improving the adhesion at the matrix–fiber interface. The mechanical behavior of GFL and PL composites was discussed in conjunction with the morphology of the samples studied by optical and electron microscopy and the matrix crystalline structure as revealed by synchrotron X‐ray diffraction. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40083. 相似文献
953.
Nonisothermal crystallization kinetics of poly(butylene terephthalate)/multiwalled carbon nanotubes nanocomposites prepared by in situ polymerization
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Poly(butylene terephthalate)/multiwalled carbon nanotubes (PBT/MWNT) nanocomposites were prepared by in situ ring‐opening polymerization of cyclic butylene terephthalate oligomers (CBT). The nonisothermal crystallization behavior of the neat PBT and the PBT/MWNT nanocomposites was analyzed quantitatively. The results reveal that the combined Avrami/Ozawa equation exhibits great advantages in describing the nonisothermal crystallization of PBT and its nanocomposites. The presence of MWNTs has the nucleation effect promoting crystallization rate for the nanocomposites, and the maximum one is observed in the nanocomposite having 0.75 wt % MWNT content. On the other hand, the addition of MWNTs has the impeding effect reducing the chain mobility and retarding crystallization, which is confirmed by the crystallization activation energies. However, the nucleation effect of MWNTs plays the dominant role in the crystallization of PBT/MWNT nanocomposites, in other words, the incorporation of MWNTs is increasing the crystallization rate of the nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40849. 相似文献
954.
This study was undertaken to examine possible use of classic tetravalent tin‐based heat stabilizers for the preparation of a polymer plasticizer: poly(ε‐caprolactone) (PCL) and simultaneous stabilization of PVC in PVC/PCL mixtures. PCL was prepared from ε‐caprolactone (CL) by polymerization initiated by tin‐containing organic compounds and successfully used to simultaneously plasticize and stabilize PVC. Moreover, conditions under which the polymerization of CL took place directly in situ during PVC/CL mixture processing were found. The procedure yielded homogeneous plasticized PVC/PCL mixtures, which were stable and contained >90% of the original monomer content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41066. 相似文献
955.
Grigor B. Bantchev Kenneth M. Doll Girma Biresaw Karl E. Vermillion 《Journal of the American Oil Chemists' Society》2014,91(12):2117-2123
Reactions of epoxidized alkyl soyate with four different alcohols: ethanol, isopropyl alcohol, 2‐ethylhexanol, benzyl alcohol, in the presence of Brønsted acid catalyst, were investigated. Products, not reported in prior studies of similar reactions, were found. These were furan fatty acid alkyl esters (FFE, mixture of alkyl 8‐(5‐hexyl‐2‐furyl) octanoate and alkyl 9‐(5‐pentyl‐2‐furyl)nonanoate) which were unambiguously identified by means of GC–MS and two‐dimensional NMR. Evidence suggests that the FFE are formed by an acid‐catalyzed rearrangement of the epoxidized linoleates. The FFE were formed in presence of all four alcohols tested and in the presence of either sulfuric acid or Amberlyst 15 catalyst. Yields of up to 13 %, as quantified by GC and NMR spectroscopies, were observed. 相似文献
956.
Controlled delivery of growth‐hormone‐releasing peptide 6 from the poly(lactic‐co‐glycolic acid)–poly(ethylene glycol)–poly(lactic‐co‐glycolic acid) copolymer and the effect of a growth‐hormone‐releasing peptide 6–copolymer hydrogel on the growth of rex rabbits
下载免费PDF全文
![点击此处可从《应用聚合物科学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xin Zhang Yunyun Cheng Dan Su Chao Lu Xibi Fang Qiang Ma Dawei Zhang Hao Yu Linlin Hao Songcai Liu 《应用聚合物科学杂志》2014,131(9)
Growth‐hormone‐releasing peptide 6 (GHRP‐6) plays an important role in animal growth. However, there have been few studies focusing on the effect of GHRP‐6 on animal growth through controlled release systems. We synthesized the poly(lactic‐co‐glycolic acid) (PLGA)–poly(ethylene glycol) (PEG)–PLGA copolymer to investigate its controlled released effect on GHRP‐6 in vitro and to study the effect of a GHRP‐6–copolymer hydrogel on the growth of rex rabbits. The copolymer was synthesized with ring‐opening copolymerization and characterized by 1H‐NMR. The interaction between GHRP‐6 and the copolymer was characterized by Fourier transform infrared spectroscopy and X‐ray diffraction. The body weight, serum level of insulin‐like growth factor 1 (IGF‐1), and hair coat quality were studied in rex rabbits. The results show that hydrogen bonds formed between the N? H group in GHRP‐6 and the C?O group in the copolymer. The release mechanism of GHRP‐6 was a combination of a diffusion‐controlled mechanism and an erosion‐controlled mechanism in the copolymer. The serum level of IGF‐1, hair coat quality, and body weight were all significantly higher in the GHRP‐6–copolymer hydrogel group than in the other groups. These results indicate that the copolymer effectively controlled the release of GHRP‐6. In addition, the GHRP‐6–copolymer hydrogel increased the synthesis of IGF‐1 for a prolonged period and, thereby, increased the rex rabbits' growth and hair coat quality. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40185. 相似文献
957.
958.
959.
960.