全文获取类型
收费全文 | 98551篇 |
免费 | 8635篇 |
国内免费 | 4797篇 |
学科分类
工业技术 | 111983篇 |
出版年
2024年 | 183篇 |
2023年 | 1151篇 |
2022年 | 1818篇 |
2021年 | 3102篇 |
2020年 | 2384篇 |
2019年 | 2236篇 |
2018年 | 2376篇 |
2017年 | 2697篇 |
2016年 | 2715篇 |
2015年 | 3536篇 |
2014年 | 4798篇 |
2013年 | 5882篇 |
2012年 | 6689篇 |
2011年 | 7280篇 |
2010年 | 6542篇 |
2009年 | 6519篇 |
2008年 | 6363篇 |
2007年 | 6050篇 |
2006年 | 6036篇 |
2005年 | 5065篇 |
2004年 | 4093篇 |
2003年 | 3677篇 |
2002年 | 4205篇 |
2001年 | 3567篇 |
2000年 | 2607篇 |
1999年 | 2106篇 |
1998年 | 1574篇 |
1997年 | 1271篇 |
1996年 | 1178篇 |
1995年 | 977篇 |
1994年 | 731篇 |
1993年 | 527篇 |
1992年 | 445篇 |
1991年 | 323篇 |
1990年 | 266篇 |
1989年 | 191篇 |
1988年 | 191篇 |
1987年 | 123篇 |
1986年 | 78篇 |
1985年 | 71篇 |
1984年 | 65篇 |
1983年 | 43篇 |
1982年 | 42篇 |
1981年 | 32篇 |
1980年 | 27篇 |
1979年 | 29篇 |
1978年 | 12篇 |
1977年 | 18篇 |
1976年 | 27篇 |
1975年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
992.
993.
994.
Shear creep resistance of styrene–isoprene–styrene (SIS)‐based hot‐melt pressure‐sensitive adhesives
The effects of the properties of substrates and tackifier on the shear creep of SIS‐based HMPSAs were investigated. The holding power (tb) and shear adhesion failure temperature (SAFT) were measured. The relationship between the complex viscosity and the holding power was examined. The holding power and SAFT values of the triblock SIS blends were higher than those of the diblock‐containing SIS blends, perhaps because blends using triblock SIS have higher crossover temperature and complex viscosity than those using diblock‐containing SIS. Higher levels of aromatic resin‐modified aliphatic tackifier and rosin ester were found to decrease the holding power of the HMPSAs. This maybe due to the fact that rosin ester and aromatic‐modified aliphatic resin are compatible with both the ends and midblocks of SIS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 825–831, 2006 相似文献
995.
In the present investigation, we develop a method for estimating rheological parameters of viscoelastic fluids using velocity measurement in a square straight channel. It is believed that a somewhat complicated patterns of secondary flows due to the non-zero second normal stress difference are more useful than the simple viscometric flows traditionally adopted in the determination of rheological parameters. The inverse problem of determining the rheological parameters from a set of velocity measurements is solved using a conjugate gradient method. When applied to a general constitutive equation encompassing the UCM model, the Oldroyd-B model and the PTT model, the present method is found to yield a reasonably accurate estimation of five rheological parameters simultaneously even with noisy velocity measurements. 相似文献
996.
997.
探讨了在Bacillus subtilis NX-2发酵生产g-聚谷氨酸(g-PGA)过程中,Mn2+对g-PGA结构中D-和L-谷氨酸组成的影响及其与催化L-谷氨酸生成D-谷氨酸的两个相关酶?谷氨酸消旋酶和D-氨基酸转氨酶之间的关系. 当Mn2+浓度由0增加到0.09 g/L时,D-谷氨酸比例从18%增加到77%;谷氨酸消旋酶活性从0.200 U/mg变为0.441 U/mg,提高了1倍多,D-氨基酸转氨酶活性则几乎没有变化. 说明谷氨酸消旋酶参与了L-到D-谷氨酸的转化过程,且Mn2+是通过改变谷氨酸消旋酶的活性来调节产物g-PGA的立体组成的,这与目前报道的枯草芽孢杆菌合成g-PGA过程中Mn2+浓度与g-PGA中D-, L-构型比无关的结果不同. 当Mn2+浓度为0.03 g/L时,发酵过程中生成的g-PGA中D-谷氨酸比例不变,维持在75%左右. 相似文献
998.
999.
Low crosslinked copolymer of linear and hyperbranched polyurethane (CHPU) was prepared, and the ionic conductivities and thermal properties of the composite polymer electrolytes composed of CHPU and LiClO4 were investigated. The FTIR and Raman spectra analysis indicated that the polyurethane copolymer could dissolve more lithium salt than the corresponding polymer electrolytes of the non crosslinked hyperbranched polyurethane, and showed higher conductivities. At salt concentration EO/Li = 4, the electrolyte CHPU30‐LiClO4 reached its maximum conductivity, 1.51 × 10?5 S cm?1 at 25°C. DSC measurement was also used for the analysis of the thermal properties of polymer electrolytes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3607–3613, 2007 相似文献
1000.