全文获取类型
收费全文 | 1075篇 |
免费 | 51篇 |
国内免费 | 5篇 |
专业分类
化学 | 856篇 |
晶体学 | 27篇 |
力学 | 17篇 |
数学 | 40篇 |
物理学 | 191篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 12篇 |
2020年 | 24篇 |
2019年 | 26篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 25篇 |
2015年 | 24篇 |
2014年 | 33篇 |
2013年 | 51篇 |
2012年 | 51篇 |
2011年 | 62篇 |
2010年 | 36篇 |
2009年 | 30篇 |
2008年 | 66篇 |
2007年 | 55篇 |
2006年 | 66篇 |
2005年 | 81篇 |
2004年 | 48篇 |
2003年 | 59篇 |
2002年 | 54篇 |
2001年 | 30篇 |
2000年 | 34篇 |
1999年 | 10篇 |
1998年 | 13篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 21篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 19篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1973年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有1131条查询结果,搜索用时 203 毫秒
91.
傅元勇 周书华T. Koike S. Kinoshita Y. Ma Y. Miura K. Miwa Y. Miyagi K. Shirotori T. Suzuki H. Tamura K. Tsukada M. Ukai K. Futatsukawa K. Hosomi M. Kawai M. Mimori N. Terada N. Maruyama K. Aoki H Fujioka Y Kakiguchi T. Nagae D. Nakajima H Noumi T Takahashi T.N. Takahashi A. Toyota M. Dairaku T. Fukuda S. Minami W. Imoto S. Aiimura K. Tanida 《中国物理快报》2007,24(8):2216-2218
From the ^12 C(π^+,K^+)^12 AC reaction the γ -rays of 261.6±0.24 ke V(7/2^+ →5/2^+)and 1481.7±0.7 ke V(1/2^+ →5/2^+) of ^11 A B,and 2667.3±2.8 keV(1^- 2 → 2^- 1)of ^12 A C hypernuclei have been identified using a large germanium detector array Hyperball2 at K6 beam line of KEK. The observed energies of the transitions 1481.7keV and 261.6 keV are significantly different from the values predicted by the shell model using the △ and SN parameters determined from the ^7 △ Li data. 相似文献
92.
93.
Micron-sized monodispersed polystyrene (PS)/poly(3,5-xylidine) (PXy) composite particles were produced by chemical oxidative
seeded dispersion polymerization of 3,5-xylidine at 20 °C with 1.6-μm-sized monodispersed PS seed particles in HCl aqueous
solution, the pH of which was always kept at 2.5 with a pH stat. The composite particles produced consisted of a PS core and
a PXy shell.
Received: 16 December 1998 Accepted in revised form: 25 March 1999 相似文献
94.
95.
96.
In this study, a cation-exchange resin (CEX) of the K+-form, i.e., an enhancer resin, is used as a postcolumn conductimetric enhancer in the ion-exclusion chromatography of aliphatic carboxylic acids. The enhancer resin is filled in the switching valve of an ion chromatograph; this valve is usually used as a suppressor valve in ion-exchange chromatography. An aliphatic carboxylic acid (e.g., CH3COOH) separated by a weakly acidic CEX column of the H+-form converts into that of the K+-form (e.g., CH3COOK) by passing through the enhancer resin. In contrast, the background conductivity decreases because a strong acid (e.g., HNO3) with a higher conductimetric response in an eluent converts into a salt (e.g., KNO3) with a lower conductimetric response. Since the pH of the eluent containing the resin enhancer increases from 3.27 to 5.85, the enhancer accelerates the dissociations of analyte acids. Consequently, peak heights and peak areas of aliphatic carboxylic acids (e.g., acetic acid, propionic acid, butyric acid, and valeric acid) with the enhancer resin are 6.3-8.0 times higher and 7.2-9.2 times larger, respectively, than those without the enhancer resin. Calibrations of peak areas for injected analytes are linear in the concentration range of 0.01-1.0 mM. The detection limits (signal-to-noise ratio = 3) range from 0.10 μM to 0.39 μM in this system, as opposed to those in the range of 0.24-7.1 μM in the separation column alone. The developed system is successfully applied to the determination of aliphatic carboxylic acids in a chicken droppings sample. 相似文献
97.
Reaction of 2-propargylphenylcarbamates with diphenyliodonium salts via Meyer-Schuster rearrangement
Hideki Minami Noriko Okamoto Takuya Sueda Takatsugu Sakaguchi Minoru Ishikura Reiko Yanada 《Tetrahedron letters》2017,58(45):4277-4280
The syntheses of 2,3-dihydro-4-quinolones from 2-propargylphenylcarbamates by one-pot tandem process that involves Meyer-Schuster rearrangement or arylative Meyer-Schuster rearrangement/Michael addition of carbamate nitrogen to the resulting vinyl ketones have been developed. Phenylcarbamates tethering tertiary propargyl alcohols underwent arylative Meyer-Schuster rearrangement/Friedel-Crafts alkylation to produce 2,3-dihydroindenones. 相似文献
98.
The synthesis of various trifluoromethylated amino compounds was studied using trifluoroacetaldehyde, an industrial bulk material, as a starting compound. One general application of trifluoroacetaldehyde is the preparation of trifluoroethylamino derivatives via reductive amination reaction. This synthesis includes the formation of the corresponding N,O-acetal intermediates followed by their reduction using NaBH4 or 2-picoline borane complex, affording the target trifluoroethylamino compounds in moderate to good yields (47-87%).Another general application of trifluoroacetaldehyde is the synthesis of chiral α-substituted trifluoroethylamino compounds. In this synthesis, trifluoroacetaldehyde was first converted into the chiral trifluoromethyl tert-butyl sulfinimine, which was subjected to 1,2-nucleophilic addition reactions across its CN double bond. The addition of phenyllithium afforded α-(phenyl)trifluoroethylamino derivative in 83% yield and with 96% de. Allylation and Reformatsky reactions produced the corresponding α-substituted trifluoroethylamino derivatives in 82 and 58% yields and with 90 and 91% de, respectively. 相似文献
99.
Development of sulfide glass-ceramic electrolytes for all-solid-state lithium rechargeable batteries
Akitoshi Hayashi Keiichi Minami Masahiro Tatsumisago 《Journal of Solid State Electrochemistry》2010,14(10):1761-1767
Development of Li2S–P2S5-based glass-ceramic electrolytes is reviewed. Superionic crystals of Li7P3S11 and Li3.25P0.95S4 were precipitated from the Li2S–P2S5 glasses at the selected compositions. These high temperature or metastable phases enhanced conductivity of glass ceramics
up to over 10−3 S cm−1 at room temperature. The original (or mother) glass electrolytes itself showed somewhat lower conductivity of 10−4 S cm−1 and have important role as a precursor for obtaining the superionic crystals, which were not synthesized by a conventional
solid-state reaction. The substitution of P2O5 for P2S5 at the composition 70Li2S·30P2S5 (mol%) improved both conductivity and electrochemical stability of glass-ceramic electrolytes. The all-solid-state In/LiCoO2 cell using the 70Li2S·27P2S5·3P2O5 (mol%) glass-ceramic electrolyte showed initial capacity of 105 mAh g−1 (gram of LiCoO2) at the current density of 0.13 mA cm−2 and exhibited higher electrochemical performance than that using the 70Li2S·30P2S5 glass-ceramic electrolyte. 相似文献
100.
Shogo Ura Kenji Kintaka Hideyuki Awazu Yasuhiro Awatsuji Junji Nishii 《Optical Review》2011,18(1):99-102
An interference exposure system using a phase-shifting mask was proposed for generating periodic sawtooth optical intensity
profile with chirp in period. Multiple space-harmonic waves are launched from the mask by diffraction, and the sawtooth optical
intensity is formed by interference based on Fourier synthesis after propagation through an air gap. The design concept merely
utilizing positive diffraction-order harmonics with tilt illumination of an exposure light and a design algorithm based on
time-reversed configuration for calculating required phase shift amount were proposed and discussed. A phase-shifting mask
for a blazed grating of very high chirp rate was designed to demonstrate its potential and feasibility. The grating period
changes from 2.2 to 3.1 μm gradually within 0.3 mm length. Sawtooth-like optical intensity profile was confirmed by theoretical
simulation as well as preliminary experimental results. 相似文献