全文获取类型
收费全文 | 4561篇 |
免费 | 165篇 |
国内免费 | 22篇 |
专业分类
化学 | 3396篇 |
晶体学 | 44篇 |
力学 | 63篇 |
数学 | 307篇 |
物理学 | 938篇 |
出版年
2023年 | 24篇 |
2022年 | 36篇 |
2021年 | 46篇 |
2020年 | 52篇 |
2019年 | 72篇 |
2018年 | 55篇 |
2017年 | 45篇 |
2016年 | 112篇 |
2015年 | 84篇 |
2014年 | 109篇 |
2013年 | 208篇 |
2012年 | 260篇 |
2011年 | 279篇 |
2010年 | 130篇 |
2009年 | 139篇 |
2008年 | 276篇 |
2007年 | 267篇 |
2006年 | 280篇 |
2005年 | 267篇 |
2004年 | 199篇 |
2003年 | 197篇 |
2002年 | 171篇 |
2001年 | 91篇 |
2000年 | 93篇 |
1999年 | 73篇 |
1998年 | 39篇 |
1997年 | 50篇 |
1996年 | 53篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 43篇 |
1992年 | 68篇 |
1991年 | 55篇 |
1990年 | 41篇 |
1989年 | 41篇 |
1988年 | 44篇 |
1987年 | 39篇 |
1986年 | 36篇 |
1985年 | 76篇 |
1984年 | 55篇 |
1983年 | 41篇 |
1982年 | 43篇 |
1981年 | 41篇 |
1980年 | 33篇 |
1979年 | 37篇 |
1978年 | 31篇 |
1977年 | 32篇 |
1976年 | 42篇 |
1975年 | 30篇 |
1973年 | 24篇 |
排序方式: 共有4748条查询结果,搜索用时 31 毫秒
41.
Y. Miyamoto Y. Saito M. Magara S. Usuda 《Journal of Radioanalytical and Nuclear Chemistry》2003,255(3):553-557
To clarify the magnitude of wash-out effect of rain on the elemental composition of airborne dust and the possible origin of the dust, the dust samples were collected with a high-volume air sampler at the JAERI-Tokai. The dust suspended in rain was also collected from rain by filtration. Up to 20 elements in both types of the dust were determined by instrumental neutron activation analysis. It was found that the elements determined could be classified into 3 groups from the elemental composition and the elemental correlation in both types of the dust samples. 相似文献
42.
Y. Saito T. Okazaki A. Ohshita K. Mihama 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):403-405
Optical emission and absorption spectra from a growth zone in Cu smoke were measured by using a quartz prism spectrograph and a single-grating spectrophotometer. Atomic lines of Cu, band systems of Cu2 were observed. Two new band systems with 0–0 band heads at 252.88 and 238.79 nm were found. The continuous spectra due to Rayleigh scattering by fine particles were also observed. Variations of density of various species as a function of vertical position were revealed. 相似文献
43.
Toshio Matsushita Ken Hirotsu Taiichi Higuchi Kichisuke Nishimoto Masaaki Yoshifuji Katsuhiro Shibayama Naoki Inamoto 《Tetrahedron letters》1984,25(31):3321-3324
Ab initio Calculations of the isomerization reaction of diphosphene 1-sulfide (2′) to thiadiphosphirane (3′) suggest that the energy barrier of the reaction in the ground state is 25 kcal/mol and that 2′ lies 21 kcal/mol above 3′, while the calculations show that there exists one local minimum on the lowest triplet energy surface. 相似文献
44.
45.
46.
Summary Pyridinium ylide complexes of methylcobaloxime were synthesized by the treatment of an ylide with Co(Hdmg)2 Me(SMe2). The crystal structure of one of the complexes, [Co(Hdmg)2Me C5H5NCHCOPh]C6H6 has been determined by x-ray diffraction techniques. The crystals are monoclinic, space group P21/c, witha = 10.456(5),b = 11.079(4),c = 24.58(1) Å, = 99.58(6), V = 2808 Å3, Z = 4. The Co-C (ylide) bond distance is 2.18 Å and Co-C(methyl) 2.04 Å. C(ylide)-Co-C(methyl) bond angle is 174.9°. The crystal, i.r. and1H n.m.r. data suggest that thetrans-influence of the ylide ligands is larger than that of py, Melm, OH2 or PPh3. 相似文献
47.
Hiroshi Saito Hitoshi Kurabe Eiichi Suzuki Fumio Watari 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1995,51(14)
The IR spectra (4000-250 cm−1) of CH3SCl and CD3SCl in solid argon have been obtained. Fundamental vibrations, except the torsional vibrations, have been assigned. Normal coordinate analysis has been carried out omitting the torsional modes. 相似文献
48.
M Horie K Saito Y Hoshino N Nose N Hamada H Nakazawa 《Journal of chromatography. A》1990,502(2):371-378
A simple and selective method for the determination of sulphamethazine (SMT) and its metabolite, N4-acetylsulphamethazine (N4-AcSMT), in meat by high-performance liquid chromatography (HPLC) with photodiode-array detection was developed. The drugs were extracted from meat with 0.2% metaphosphoric acid-methanol (6:4), followed by a Bond-Elut C18 clean-up procedure. The HPLC separation was carried out on a Supersphere RP-18e column (125 X 4.0 mm I.D.) using 0.05 M sodium dihydrogenphosphate (pH 4.5)-acetonitrile (8:2) as the mobile phase at a flow-rate of 0.5 ml/min, and monitored with a photodiode-array detector. The recoveries of SMT and N4-AcSMT from meat fortified at 0.5 micrograms/g were 90.1-93.3 and 93.0-94.4%, respectively, with coefficients of variation of 1.9-3.2 and 1.5-2.7%. The limits of detection were 0.02 micrograms/g for each drug. SMT was found in ten samples of imported meat (12.5%) at levels ranging from 0.05 to 1.05 micrograms/g. 相似文献
49.
Saito H Sivaguru J Jockusch S Inoue Y Adam W Turro NJ 《Chemical communications (Cambridge, England)》2005,(27):3424-3426
Oxazolidinone-functionalized enecarbamates undergo diastereoselective E/Z photoisomerization upon direct and triplet sensitized irradiations with chiral/achiral sensitizers, showing that the enhanced product diastereoselectivity depends on the solvent and temperature. 相似文献
50.
Tuo Jiang Samuele Bordi Angus E. McMillan Kuang-Yen Chen Fumito Saito Paula L. Nichols Benedikt M. Wanner Jeffrey W. Bode 《Chemical science》2021,12(20):6977
The current laboratory practices of organic synthesis are labor intensive, impose safety and environmental hazards, and hamper the implementation of artificial intelligence guided drug discovery. Using a combination of reagent design, hardware engineering, and a simple operating system we provide an instrument capable of executing complex organic reactions with prepacked capsules. The machine conducts coupling reactions and delivers the purified products with minimal user involvement. Two desirable reaction classes – the synthesis of saturated N-heterocycles and reductive amination – were implemented, along with multi-step sequences that provide drug-like organic molecules in a fully automated manner. We envision that this system will serve as a console for developers to provide synthetic methods as integrated, user-friendly packages for conducting organic synthesis in a safe and convenient fashion.Using a combination of reagent design, hardware engineering, and a simple operating system we provide an instrument capable of executing complex organic reactions using prepacked capsules with minimal user involvement. 相似文献