全文获取类型
收费全文 | 7124篇 |
免费 | 370篇 |
国内免费 | 42篇 |
专业分类
化学 | 5534篇 |
晶体学 | 58篇 |
力学 | 95篇 |
数学 | 585篇 |
物理学 | 1264篇 |
出版年
2023年 | 45篇 |
2022年 | 121篇 |
2021年 | 155篇 |
2020年 | 121篇 |
2019年 | 135篇 |
2018年 | 103篇 |
2017年 | 92篇 |
2016年 | 248篇 |
2015年 | 217篇 |
2014年 | 271篇 |
2013年 | 456篇 |
2012年 | 540篇 |
2011年 | 629篇 |
2010年 | 377篇 |
2009年 | 338篇 |
2008年 | 490篇 |
2007年 | 423篇 |
2006年 | 423篇 |
2005年 | 346篇 |
2004年 | 296篇 |
2003年 | 256篇 |
2002年 | 290篇 |
2001年 | 129篇 |
2000年 | 141篇 |
1999年 | 74篇 |
1998年 | 51篇 |
1997年 | 66篇 |
1996年 | 64篇 |
1995年 | 52篇 |
1994年 | 37篇 |
1993年 | 39篇 |
1992年 | 43篇 |
1991年 | 25篇 |
1990年 | 37篇 |
1989年 | 39篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 15篇 |
1985年 | 31篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1976年 | 12篇 |
1975年 | 14篇 |
1970年 | 17篇 |
排序方式: 共有7536条查询结果,搜索用时 15 毫秒
41.
Yun SH Sohn BH Jung JC Zin WC Lee JK Song O 《Langmuir : the ACS journal of surfaces and colloids》2005,21(14):6548-6552
Hexagonal arrangement of iron oxide nanoparticles was fabricated by utilizing a single-layered film of diblock copolymer micelles. The synthesis was directly performed on the solid substrate by oxygen plasma with preserving the dimensional order of micelles so that separate procedures for synthesis and deposition of nanoparticles were not necessary. Since the oxygen plasma treatment also eliminated polymers, pure patterns of iron oxide nanoparticles were obtained. Moreover, easy control over the size of nanoparticles enabled us to selectively create a ferrimagnetic or a superparamagnetic pattern of iron oxide nanoparticles without altering the fabrication process. 相似文献
42.
Immobilized polysiloxane-anchored permethyl-β-cyclodextrin (Chirasil-Dex) with a cyclodextrin content of approximately 30 % by weight, previously employed as a versatile chiral stationary phase for the separation of enantiomers by GC, has been used for the separation of enantiomers by capillary supercritical fluid chromatography (SFC). A considerable number of racemates could be resolved, e.g. aromatic alcohols, amino alcohols (TFA derivatives), and underivatized acids. Many pharmaceutical compounds were among those analyzed, including several NSAIDs (e.g. ibuprofen and ketoprofen), a steroidal drug (nor-gestrel), a barbiturate (hexobarbital), and others. Among the racemates resolved were many which cannot be analyzed by GC owing to low volatility or decomposition at elevated temperatures. For two racemates, analysis temperature and mobile phase density were systematically varied to give constant analysis times or capacity factors k. Low temperatures (ca 60 °C) yielded the best separation in term of separation factor, α, or resolution, Rs, even though higher densities had to be used. In comparison with GC, capillary SFC was able to furnish higher separation factors and similar resolution. The applicability of capillary SFC for the analysis of mixtures of cyclodextrin derivatives, e.g. those used in the synthesis of Chirasil-Dex, was, furthermore, demonstrated. 相似文献
43.
In an attempt to elucidate the underlying mechanisms for iron toxicity in plants, the combined effects of iron overload and light intensities on the photosynthetic capacity of leaves were particularly focussed upon in this study, using mung bean seedlings grown under varied conditions regarding the supply of light and iron. The seedlings, when supplied with excess iron (up to 1.0 m M ) and low light (40 W/m2 ), did not suffer any loss of photosynthesis; further, the typical symptoms of iron toxicity, as shown in the leaves grown in sunlight at ca 450 W/m2 on an average, were not seen in those. Nonetheless, excess iron supply resulted in a marked increase in photosensitivity of the low light-adapted seedlings. A large portion of iron accumulated in chloroplasts by the supply of excess iron was found to be incorporated into thylakoids as nonheme iron (NHI), which acts as a potent sensitizer, photogenerating singlet oxygen (1 O2 ). The generation rate of 1 O2 from thylakoids linearly increased with increasing content of NHI; this was in parallel with the NHI content dependence of photoinactivation rates of photosynthetic electron transport and key enzymes of the Calvin cycle in chloroplasts. The results suggest that Fe-dependent photosensitization reactions, occurring via the 1 O2 mechanism, may be deeply involved in cellular processes leading to developing iron toxicity symptoms in plants. 相似文献
44.
45.
Transmission gratings of holographic polymer-dispersed liquid crystals (HPDLC) are prepared under controlled reaction conditions by adding various amounts of chain-transfer agent (CTA). The resulting films have a higher gel content with lower cross-link density, less dark reaction, less grating shrinkage with much smoother LC/polymer interfaces, smaller induction period, and fast saturation of diffraction efficiency, which shows a maximum of 95 % with 1 % CTA. An optimum LC content of 35 % is verified on the basis of morphology and reaction kinetics. 相似文献
46.
The surface-enhanced Raman scatterings of dimethyl sulfide, diethyl sulfide and dimethyl disulfide have been investigated in silver sol. The dimethyl disulfide molecule decomposes on silver to the corresponding mercaptide implying facile cleavage of its S---S bond. The C---S bond in dialkyl monosulfide appears not to cleave on silver. For diethyl sulfide, the C2 conformation seems to be favorable on silver than other conformations. 相似文献
47.
Tae Oan Ahn Jung Ho Kim Jong Chan Lee Han Mo Jeong Jong-Yoon Park 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):435-441
A macro-azoinitiator containing polyarylate segment and azo group was prepared by the solution polycondensation of azobiscyanopentanoyl chloride and hydroxy-terminated polyarylates having viscosity-average molecular weights of 6200, 8100, and 12 400. These macro-azoinitiators were used in the radical polymerization of styrene to synthesize polyarylate-polystyrene block copolymers. Thermal properties measured by the differential scanning calorimetry indicated the phase separated morphology of the block copolymers except at low molecular weight of the block constituents. © 1993 John Wiley & Sons, Inc. 相似文献
48.
49.
Abachi S Baringer P Bylsma BG DeBonte R Koltick D Loeffler FJ Low EH McIlwain RL Miller DH Ng CR Rangan LK Shibata EI Derrick M Gan KK Kooijman P Loos JS Musgrave B Price LE Repond J Sugano K Weiss JM Wood DE Blockus D Brabson B Brom J Jung C Ogren H Rust DR Akerlof C Chapman J Errede D Kesten P Meyer DI Nitz D Seidl AA Thun R Willutzky M Cork B 《Physical review letters》1986,57(16):1990-1993
50.
T. Rösel P. Schlemmer J. Röder L. Frost K. Jung H. Ehrhardt 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,23(4):359-363
A new method, and first results for an impact energy 2 eV above the threshold of ionisation of helium, are presented for the measurement of absolute triple differential cross sections (TDCS) in a crossed beam experiment. The method is based upon measurement of beam/target overlap densities using known absolute total ionisation cross sections and of detection efficiencies using known absolute double differential cross sections (DDCS). For the present work the necessary absolute DDCS for 1 eV electrons had also to be measured. Results are presented for several different coplanar kinematics and are compared with recent DWBA calculations. 相似文献