全文获取类型
收费全文 | 2589篇 |
免费 | 84篇 |
国内免费 | 6篇 |
专业分类
化学 | 2084篇 |
晶体学 | 27篇 |
力学 | 23篇 |
数学 | 138篇 |
物理学 | 407篇 |
出版年
2022年 | 9篇 |
2021年 | 21篇 |
2020年 | 31篇 |
2019年 | 40篇 |
2018年 | 35篇 |
2017年 | 13篇 |
2016年 | 60篇 |
2015年 | 52篇 |
2014年 | 57篇 |
2013年 | 147篇 |
2012年 | 114篇 |
2011年 | 139篇 |
2010年 | 77篇 |
2009年 | 74篇 |
2008年 | 138篇 |
2007年 | 113篇 |
2006年 | 138篇 |
2005年 | 129篇 |
2004年 | 137篇 |
2003年 | 144篇 |
2002年 | 109篇 |
2001年 | 65篇 |
2000年 | 90篇 |
1999年 | 39篇 |
1998年 | 24篇 |
1997年 | 41篇 |
1996年 | 39篇 |
1995年 | 28篇 |
1994年 | 29篇 |
1993年 | 38篇 |
1992年 | 33篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 32篇 |
1987年 | 16篇 |
1986年 | 17篇 |
1985年 | 33篇 |
1984年 | 43篇 |
1983年 | 17篇 |
1982年 | 28篇 |
1981年 | 24篇 |
1980年 | 33篇 |
1979年 | 32篇 |
1978年 | 31篇 |
1977年 | 19篇 |
1976年 | 17篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 14篇 |
排序方式: 共有2679条查询结果,搜索用时 31 毫秒
1.
Hisatoyo Morinaga Natsumi Ogawa Mayu Sakamoto Hiroshi Morikawa 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):2466-2473
The thiol‐ene reaction between trans‐limonene oxide (trans‐LO) and ethane‐1,2‐dithiol in the presence of triethylborane affords a bio‐based bis‐functional epoxide (bis‐trans‐LO). The crosslinking reaction of bis‐trans‐LO with branched polyethyleneimine (BPEI; Mn = 600; BPEI600) at a feed ratio of bis‐trans‐LO/BPEI600 = 57/43 (wt/wt) yields the corresponding network polymer with Td10 (10% thermal decomposition temperature) of 304.7 °C in 98% yield. In contrast, negligible amounts of network polymer are obtained by the reaction of bis‐LO (bis‐functional epoxide derived from cis and trans‐LO) and BPEI600 regardless of the feed ratio. The mechanical strengths as measured by direct tensile tests of the network polymers derived from bis‐trans‐LO and BPEI600,1800 (Mn = 600 and 1800) were approximately 16 and 11 times higher than that of bis‐LO and BPEI1800, respectively. The tensile shear strengths of the metal‐to‐metal adhesive bonds induced by bis‐trans‐LO and BPEI600,1800 were 9.5 and 14.1 MPa, respectively. DMA revealed that the storage modulus of the network polymer derived from bis‐trans‐LO and BPEI1800 in the rubber region was higher than that of the material prepared from bis‐LO and BPEI1800, indicating higher crosslink density of the bis‐trans‐LO/BPEI1800 system. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2466–2473 相似文献
2.
3.
4.
Toshiro Watanabe Tapan Kumar Mazumder Shiro Nagai Keisuke Tsuji Shigeru Terabe 《Analytical sciences》2003,19(1):159-161
A micellar electrokinetic chromatography (MEKC) method was developed for estimating the angiotensin-I converting enzyme (ACE) inhibitory activity by separating the hippuric acid liberated in the ACE reaction mixture in the presence of an inhibitor, captopril. The hippuric acid was successfully separated and detected by MEKC with a 25 mM sodium dodecyl sulfate solution in a 25 mM phosphate-50 mM borate buffer at pH 7.0; the total analysis took about 5 min. A good linear relationship was observed between the inhibitor and the peak area of hippuric acid release. No significant difference in the ACE inhibitory activity (IC50) of captopril (an antihypertensive medicine) or autolyzed-mushrooms (functional foods) was observed between the conventional method and the MEKC method. The MEKC method was found to be a useful technique for a rapid assay of the ACE inhibitory activity. 相似文献
5.
6.
An optical fiber multi-function device consisting of a single gradient-index-rod lens and a multi-facet blazed reflection
grating is proposed to simultaneously realize functions of wavelength demultiplexing and optical signal distribution in a
multimode optical fiber transmission system. We analyzed the demultiplexing characteristics and the tolerance of optical components
using the ray trace method. This device can realize not only low loss optical signal distribution but also offers improved
demultiplexing characteristics in comparison with the previously proposed demultiplexer-multiposition switch. The following
characteristics are expected from the design using commercially available optical components: a working band of 0.64–0.88
μm, channel separation of 34–36 nm, 3 dB bandwidth of 27–28 nm, channel cross-talk of less than - 40 dB and minimum excess
insertion loss of 0.9–2.1 dB. 相似文献
7.
R. Minami A. Kasugai K. Takahashi N. Kobayashi Y. Mitsunaka K. Sakamoto 《International Journal of Infrared and Millimeter Waves》2006,27(1):13-24
A high efficiency launcher of quasi-optical (QO) mode converters for high power gyrotrons have been designed and tested. A
helical cut launcher radiates the RF power via its straight cut onto the first phase correcting mirror. The launchers have
been optimized for the TE31.8 mode at 170 GHz and TE22.6 mode at 110 GHz by numerically optimizing a launcher surface. The helical cut of the launcher has been optimized by taking
the taper angle into account. Further more, the amplitude of the surface perturbation have been optimized for improved focusing
in order to reduce the diffraction losses at the helical cut. Low power measurement shows a good agreement with the design.
High efficiency characteristics of the design have also been calculated on the assumption of frequency downshift due to the
thermal expansion of the cavity and stepwise frequency tuning by changing the operating mode. Besides, the possibility of
high efficiency launcher for higher mode is discussed, and these results give the prospect to high efficiency long pulse gyrotrons. 相似文献
8.
9.
Shigeru Tasaka Norihiro Inagaki Masaaki Igawa 《Journal of Polymer Science.Polymer Physics》1991,29(6):691-694
The permeability of annealed poly (l-(trimethylsilyl)-l-propyne) was studied from the viewpoint of structural information obtained from x-ray diffraction and density. The sample cast from benzene solution had low density (0.82 g/cm3) and high permeability, whereas the annealed sample had a higher density (0.88 g/cm3) and permeability lower by two orders of magnitude. The smaller-angle x-ray diffraction peak for each sample, which was likely to reflect the distance between intermolecular chains, increased in intensity and shifted toward higher angle, corresponding to the change of the density with annealing. The logarithmic oxygen permeability was proportional to the density, namely the free volume fraction correlated with the diffusion coefficient and controlled by annealing and swelling by alcohols. 相似文献
10.
Shigeru Yamagami 《Journal of Pure and Applied Algebra》2002,167(1):83-128
A duality for orbifolds is presented as an application of group extensions in tensor categories. 相似文献