全文获取类型
收费全文 | 5090篇 |
免费 | 157篇 |
国内免费 | 9篇 |
专业分类
化学 | 3767篇 |
晶体学 | 72篇 |
力学 | 54篇 |
综合类 | 2篇 |
数学 | 177篇 |
物理学 | 1184篇 |
出版年
2023年 | 31篇 |
2022年 | 37篇 |
2021年 | 52篇 |
2020年 | 83篇 |
2019年 | 98篇 |
2018年 | 72篇 |
2017年 | 29篇 |
2016年 | 103篇 |
2015年 | 135篇 |
2014年 | 96篇 |
2013年 | 231篇 |
2012年 | 263篇 |
2011年 | 271篇 |
2010年 | 156篇 |
2009年 | 164篇 |
2008年 | 237篇 |
2007年 | 283篇 |
2006年 | 241篇 |
2005年 | 276篇 |
2004年 | 220篇 |
2003年 | 189篇 |
2002年 | 186篇 |
2001年 | 115篇 |
2000年 | 115篇 |
1999年 | 72篇 |
1998年 | 50篇 |
1997年 | 44篇 |
1996年 | 78篇 |
1995年 | 55篇 |
1994年 | 48篇 |
1993年 | 71篇 |
1992年 | 68篇 |
1991年 | 64篇 |
1990年 | 55篇 |
1989年 | 56篇 |
1988年 | 52篇 |
1987年 | 58篇 |
1986年 | 53篇 |
1985年 | 88篇 |
1984年 | 84篇 |
1983年 | 42篇 |
1982年 | 56篇 |
1981年 | 49篇 |
1980年 | 62篇 |
1979年 | 60篇 |
1978年 | 51篇 |
1977年 | 39篇 |
1976年 | 41篇 |
1974年 | 29篇 |
1973年 | 30篇 |
排序方式: 共有5256条查询结果,搜索用时 0 毫秒
961.
962.
Tetsuji Kametani Hiroko Kasai Etsuko Sato Toshio Suzuki 《Journal of Chemical Sciences》1988,100(2-3):91-111
For the purpose of organic syntheses of some corynanthe-type indole alkaloids, sesquiterpenes, and steroids, optically active
intermediates cyclopentanone 3-allylalcohol, α-methylene-γ-butylo lactones andtrans-hydrindanone-propionic acid, were synthesized from (R)- and (S)-isopropylideneglyceraldehyde derived fromD-mannitol andLascorbic acid, respectively, utilizing Claisen rearrangement as a key reaction. Actually total syntheses of natural alkaloids,
(-)-antirhine, (+)-dihydroantirhine and (-) dihydrocorynantheol were accomplished. 相似文献
963.
964.
965.
T. Sato 《Journal of Radioanalytical and Nuclear Chemistry》1983,76(1):215-224
In order to obtain information about postnatal changes in trace element levels in rat tissues, the age-dependent variations in the concentrations of 6 elements (Fe, Zn, Co, Se, Rb and Cs) were investigated by thermal neutron activation analysis. Several variation patterns were revealed in their concentrations as a function of postnatal age, depending on the combination of an element and an organ: (1) A steady state without significant variations (Zn and Se in brain, Rb and Cs in liver), (2) accumulation till a steady level is attained in time (Se in liver and kidney, Co in kidney), (3) depletion till a steady level is attained in time (Fe and Co in brain, Zn in liver and kidney, Rb and Cs in kidney), (4) permanent depletion (Rb and Cs in brain), and 95) initial drop followed by gradual increase in concentration levels (Fe in liver and kidney, Co in liver) 相似文献
966.
967.
(Styrene-p-chlorostyrene) triblock copolymers of the ABA and BAB types (A—polystyrene; B—poly-p-chlorostyrene) were prepared by anionic polymerization and their conformational behaviours in solutions were studied from measurements of the dipole moments. Two solvents, toluene and cumene, were used for the study; toluene is a good solvent for both polystyrene and poly-p-chlorostyrene whereas cumene is a selective solvent, good for polystyrene but poor for poly-p-chlorostyrene. It was found that the dipole moments of the block copolymers measured in toluene are the same for the ABA and BAB copolymers; in cumene however the dipole moment of the BAB copolymer is smaller than that of the ABA copolymer. The results give an additional support to our previous conclusion that the conformation of the block copolymers in a good solvent such as toluene could be approximated with a pseudo-random coil form; in a selective solvent, however, some anomalies take place in the conformation of the block copolymers, as deduced from intrinsic viscosity, osmotic pressure and light scattering measurements. 相似文献
968.
C.B. Zamboni D.N.S. Giovanni V.L.R. Salvador I.M. Sato R.Z. Mendonça F.H. Wen M.S. Simons 《X射线光谱测定》2019,48(5):465-475
In this study, multielemental analysis of Lonomia obliqua (Lepidoptera, Saturniidae) caterpillar was performed using energy dispersive X-ray fluorescence and instrumental neutron activation analysis techniques. This caterpillar is poisonous and has the ability to cause fatal hemorrhagic effects in humans after contact. The need of this study is related to morphological changes (mainly size and color) observed in some caterpillars used for preparation of antilonomic serum (antivenom). The samples were classified as healthy (caterpillars of control) and unhealthy (caterpillars visibly modified). The XRF measurements were performed in an energy dispersive X-ray fluorescence spectrometer and the instrumental neutron activation analysis using the IEA-R1 nuclear reactor at IPEN. The results show significant differences for several elements (mainly, P, Cl, Ca, Ti, Mn, Fe, Ni, and Zn) in unhealthy caterpillars that can affect the development of this species as well as the quality and yield of the antivenom. Furthermore, its elemental characterization contributes for the understanding the potential pharmacological (procoagulant and antithrombotic) in the prevention of life-threatening blood clots. 相似文献
969.
Hiroyuki Okamoto Kohei Noda Moritsugu Sakamoto Tomoyuki Sasaki Yasuhiro Wada Nobuhiro Kawatsuki Hiroshi Ono 《Optical Review》2017,24(4):510-516
We developed a method for the design of multilevel anisotropic diffraction gratings based on a genetic algorithm. The method is used to design the multilevel anisotropic diffraction gratings based on input data that represent the output from the required grating. The validity of the proposed method was evaluated by designing a multilevel anisotropic diffraction grating using the outputs from an orthogonal circular polarization grating. The design results corresponded to the orthogonal circular polarization grating structures that were used to provide outputs to act as the input data for the process. Comparison with existing design methods shows that the proposed method can reduce the number of human processes that are required to design multilevel anisotropic diffraction gratings. Additionally, the method will be able to design complex structures without any requirement for subsequent examination by a human designer. The method can contribute to the development of optical elements by designing multilevel anisotropic diffraction gratings. 相似文献
970.