全文获取类型
收费全文 | 1824篇 |
免费 | 37篇 |
国内免费 | 4篇 |
专业分类
化学 | 1310篇 |
晶体学 | 25篇 |
力学 | 15篇 |
数学 | 111篇 |
物理学 | 404篇 |
出版年
2023年 | 11篇 |
2022年 | 11篇 |
2021年 | 21篇 |
2020年 | 23篇 |
2019年 | 36篇 |
2018年 | 32篇 |
2017年 | 16篇 |
2016年 | 41篇 |
2015年 | 29篇 |
2014年 | 54篇 |
2013年 | 75篇 |
2012年 | 89篇 |
2011年 | 117篇 |
2010年 | 83篇 |
2009年 | 69篇 |
2008年 | 108篇 |
2007年 | 106篇 |
2006年 | 103篇 |
2005年 | 95篇 |
2004年 | 69篇 |
2003年 | 105篇 |
2002年 | 100篇 |
2001年 | 50篇 |
2000年 | 39篇 |
1999年 | 18篇 |
1998年 | 25篇 |
1997年 | 22篇 |
1996年 | 19篇 |
1995年 | 21篇 |
1994年 | 14篇 |
1993年 | 8篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 14篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1974年 | 7篇 |
1973年 | 7篇 |
1967年 | 7篇 |
排序方式: 共有1865条查询结果,搜索用时 15 毫秒
51.
52.
Ishii A Kawai T Tekura K Oshida H Nakayama J 《Angewandte Chemie (International ed. in English)》2001,40(10):1924-1926
53.
54.
Tadashi Miyasaka Hiromichi Tanaka Kazue Satoh Mie Imahashi Kentaro Yamaguchi Yoichi Iitaka 《Journal of heterocyclic chemistry》1987,24(3):873-875
A highly efficient intramolecular nitrene insertion was observed upon irradiation of 6-azidouridine derivatives. The N6,2′-cyclo structure of the product was determined unequivocally by X-ray crystallography. 相似文献
55.
Kentaro Okuma Jun-ichi Sakata Yuji Tachibana Takumi Honda Hiroshi Ohta 《Tetrahedron letters》1987,28(52):6649-6652
Wittig reagents were successfully changed to symmetrical olefins when treated with elemental selenium. The reaction proceeds through a selenocarbonyl intermediate, which existence was confirmed by Diels-Alder reaction. 相似文献
56.
Keiichiro Ishikawa Nobuyasu Hanari Yoshitaka Shimizu Toshihide Ihara Akira Nomura Masahiko Numata Takashi Yarita Kenji Kato Koichi Chiba 《Accreditation and quality assurance》2011,16(6):311-322
Purity assay of high-purity materials (HPMs) of phthalic acid esters (PAEs) was carried out by means of a mass balance method.
In this method, chromatographic methods such as gas chromatography-flame ionization detector (GC-FID) and/or high-performance
liquid chromatography (HPLC) in combination with other methods such as Karl-Fischer (KF) titration and vacuum evaporation
(VE) were applied. The sum of the impurities estimated by these methods allowed the estimation of the purity of the main component
by difference. Seven PAEs with varying side chain structures and levels of impurities were analysed on a systematic way in
which impurities were classified into several groups in terms of their abundance, availability of qualitative information
and availability of authentic compounds, etc. The absolute quantity of each impurity was determined by GC-FID and/or HPLC
based on the calibration made by the authentic compounds of impurities whenever available. The purities in mass fraction of
these PAEs were certified at the National Metrology Institute of Japan (NMIJ), and the PAEs were registered as primary reference
materials playing an essential role in linking the metrological traceability of the Japan Calibration Service System (JCSS)
to the International System of Units (SI). 相似文献
57.
Copper-mediated chemoselective trifluoromethylation at the benzylic position by the use of shelf-stable electrophilic trifluoromethylating reagents 3 in good to high yields under mild conditions is described for the first time. The generality of this trifluoromethylation for a wide variety of benzyl bromides facilitates the rapid creation of structural diversity of medicinal candidates in drug discovery. 相似文献
58.
The wave-splitting phase-shifting digital holography using a pixelated microretarder array is proposed. By using four intensity images recorded by the pixelated microretarder array, Stokes parameters of the incident wave can be calculated. The fully complex amplitude distribution of the object wave can be obtained by using Stokes parameters, if the polarization states of the object and reference waves are linear and orthogonal. Two sets of experimental results are provided to verify the feasibility of the proposed method. One is the result for a movie recording using a CW laser and the other is the result for instant recording using a single pulsed laser. 相似文献
59.
Hiroshi Nomura 《Optical Review》2010,17(5):499-506
A lithographic test pattern, the phase shift grating (PSG) z monitor, is introduced. Through the use of phase shift techniques, position errors of images in the z-direction translate into lateral shifts in the printed pattern. The lateral shifts are easily measurable using an overlay metrology tool. Each z monitor pattern in a test mask can be directly read for the sign and magnitude of the z error. When the experimental conditions, namely, the period of a PSG and a coherent factor of the lithography tool simultaneously satisfies a criterion of the asymmetric two-beam interference between the zeroth-order ray and either of the two first-order rays of diffraction, the linearity of a z-vs-overlay curve is always complete and the slope of the curve is constant everywhere in the image field. Using state-of-the-art overlay metrology tools, we realized subnanometer-order accuracy in the z measurement. 相似文献
60.
Tanaka T Teramura K Arakaki K Funabiki T 《Chemical communications (Cambridge, England)》2002,(22):2742-2743
Photoassisted selective catalytic reduction of NO with ammonia (photo-SCR) at low temperature over irradiated TiO2 in a flow reactor was confirmed to proceed efficiently and the adsorbed ammonia reacted with NO under irradiation of TiO2. 相似文献