全文获取类型
收费全文 | 7280篇 |
免费 | 1465篇 |
国内免费 | 1199篇 |
专业分类
化学 | 5580篇 |
晶体学 | 156篇 |
力学 | 393篇 |
综合类 | 114篇 |
数学 | 911篇 |
物理学 | 2790篇 |
出版年
2024年 | 20篇 |
2023年 | 147篇 |
2022年 | 273篇 |
2021年 | 306篇 |
2020年 | 347篇 |
2019年 | 336篇 |
2018年 | 313篇 |
2017年 | 329篇 |
2016年 | 358篇 |
2015年 | 421篇 |
2014年 | 463篇 |
2013年 | 512篇 |
2012年 | 658篇 |
2011年 | 738篇 |
2010年 | 534篇 |
2009年 | 429篇 |
2008年 | 531篇 |
2007年 | 465篇 |
2006年 | 394篇 |
2005年 | 343篇 |
2004年 | 281篇 |
2003年 | 280篇 |
2002年 | 346篇 |
2001年 | 251篇 |
2000年 | 142篇 |
1999年 | 136篇 |
1998年 | 86篇 |
1997年 | 68篇 |
1996年 | 75篇 |
1995年 | 75篇 |
1994年 | 55篇 |
1993年 | 36篇 |
1992年 | 38篇 |
1991年 | 33篇 |
1990年 | 39篇 |
1989年 | 22篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1959年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有9944条查询结果,搜索用时 328 毫秒
981.
Mir MH Ong JX Kole GK Tan GK McGlinchey MJ Wu Y Vittal JJ 《Chemical communications (Cambridge, England)》2011,47(42):11633-11635
A pair of trans,trans-muconate ligands have been successfully aligned in two novel Au(I) macrocycles by design from phosphino metal precursors that undergo photochemical cycloaddition reactions quantitatively, resulting in the formation of cyclooctadiene derivatives. 相似文献
982.
Ge HM Yan W Guo ZK Luo Q Feng R Zang le Y Shen Y Jiao RH Xu Q Tan RX 《Chemical communications (Cambridge, England)》2011,47(8):2321-2323
Precursor-fed cultivation of endophytic Chaetomium globosum 1C51 afforded nine novel "unnatural" halogenated chaetoglobosins including those with more preferable immunosuppressive activity. 相似文献
983.
Ying Hui Shao Xiao Ning Ren Zi Ru Liu Xiang Zhang 《Journal of Thermal Analysis and Calorimetry》2011,103(2):617-623
The eutectic ternary phase diagrams of some typical volatilizable energetic materials have been investigated by high pressure
differential scanning calorimeter (PDSC). The ternary H–X phase diagrams for TNT/TNAZ/DNTF (TTD) and TNAZ/DNTF/RDX (TDR) systems were constructed by the correlation of the apparent
fusion heat with the composition (H–X method). And, the ternary T–X phase diagrams (the temperature dependence on composition) for the two ternary systems were constructed by calculating from
the data of the five T–X binary phase diagrams. The eutectic compositions (mol%) of TTD and TDR ternary systems were obtained to be 52.3/27.3/20.4
(H–X method), 53.2/25.8/21.0 (T–X method) and 54.9/39.6/5.5 (H–X method), 55.1/42.2/2.7 (T–X method), respectively. The eutectic temperatures of the ternary systems were obtained by PDSC determination and T–X method calculation to be 76.5 and 76.7 °C, 47.5 and 50.2 °C, respectively. It is shown that the results obtained by two methods
are in agreement and the error in measuring or calculating eutectic compositions and temperatures for the two ternary systems
are within allowable ranges of ±3 mol% and ±3 °C, respectively. Moreover, by means of constructing two ternary H–X phase diagrams with different fixed composition of a component and comparing the apparent fusion heat of eutectics with calculated
one, the results obtained from H–X method for TTD system were proved. The results showed that the gasification or volatilization of easy volatile materials
could be efficiently restrained by high pressure atmosphere, and the perfectly and ideally H–X ternary phase diagrams can be constructed. In comparison with T–X method, H–X method has as a virtue of being quick and simple, especially on constructing ternary phase diagram. 相似文献
984.
985.
Das MC Xiang S Zhang Z Chen B 《Angewandte Chemie (International ed. in English)》2011,50(45):10510-10520
Immobilization of functional sites within metal-organic frameworks (MOFs) is very important for their ability to recognize small molecules and thus for their functional properties. The metalloligand approach has enabled us to rationally immobilize a variety of different functional sites such as open metal sites, catalytic active metal sites, photoactive metal sites, chiral pore environments, and pores of tunable sizes and curvatures into mixed metal-organic frameworks (M'MOFs). In this Minireview, we highlight some important functional M'MOFs with metalloligands for gas storage and separation, enantioselective separation, heterogeneous asymmetric catalysis, sensing, and as photoactive and nanoscale drug delivery and biomedical imaging materials. 相似文献
986.
Dr. Hai‐Feng Xiang Dr. Stephen Sin‐Yin Chui Prof. V. A. L. Roy Prof. Chi‐Ming Che 《化学:亚洲杂志》2011,6(12):3223-3229
Organic photovoltaic (OPV) cells using metal(II) (Pt, Pd, Cu, and Ni) chelates of 8‐hydroxyquinoline (Hq) or 5,7‐dimethyl‐8‐hydroxy‐quinoline (HMe2q) as an electron donor were fabricated by vacuum deposition. The bis(5,7‐dimethyl‐8‐hydroxyquinolinato)platinum(II) [Pt(Me2q)2]‐based OPVs showed the best performance with an open voltage (VOC) of 0.42 V, a short circuit current density (JSC) of 14.8 mA cm?2, and a maximum power conversion efficiency (ηP) of 2.4 %. The X‐ray single‐crystal structures together with the grazing incidence X‐ray diffraction (GIXRD) data of thin film samples reveal that the peripheral methyl substituent(s) and platinum(II) ion are essential for the high degree of film crystallinity resulting in improved performance of the as‐fabricated field‐effect transistors (FETs) and OPV cells. 相似文献
987.
The method of native chemical ligation between an unprotected peptide α‐thioester and an N‐terminal cysteine–peptide to give a native peptide in aqueous solution is one of the most effective peptide ligation methods. In this work, a systematic theoretical study was carried out to fully understand the detailed mechanism of ligation. It was found that for the conventional native chemical ligation reaction between a peptide thioalkyl ester and a cysteine in combination with an added aryl thiol as catalyst, both the thiol‐thioester exchange step and the transthioesterification step proceed by an anionic concerted SN2 displacement mechanism, whereas the intramolecular rearrangement proceeds by an addition–elimination mechanism, and the rate‐limiting step is the thiol‐thioester exchange step. The theoretical method was then extended to study the detailed mechanism of the auxiliary‐mediated peptide ligation between a peptide thiophenyl ester and an N‐2‐mercaptobenzyl peptide in which both the thiol‐thioester exchange step and intramolecular acyl‐transfer step proceed by a concerted SN2‐type displacement mechanism. The energy barrier of the thiol‐thioester exchange step depends on the side‐chain steric hindrance of the C‐terminal amino acid, whereas that of the acyl‐transfer step depends on the side‐chain steric hindrance of the N‐terminal amino acid. 相似文献
988.
Dr. Yasuhiro Yamashita Takaki Imaizumi Dr. Xun‐Xiang Guo Prof. Dr. Shū Kobayashi 《化学:亚洲杂志》2011,6(9):2550-2559
Asymmetric [3+2] cycloaddition of α‐aminoester Schiff bases with substituted olefins is one of the most efficient methods for the preparation of chiral pyrrolidine derivatives in optically pure form. In spite of its potential utility, applicable substrates for this method have been limited to Schiff bases that bear relatively acidic α‐hydrogen atoms. Here we report a chiral silver amide complex for asymmetric [3+2] cycloaddition reactions. A silver complex prepared from silver bis(trimethylsilyl)amide (AgHMDS) and (R)‐DTBM‐SEGPHOS worked well in asymmetric [3+2] cycloaddition reactions of α‐aminoester Schiff bases with several olefins to afford the corresponding pyrrolidine derivatives in high yields with remarkable exo‐ and enantioselectivities. Furthermore, α‐aminophosphonate Schiff bases, which have less acidic α‐hydrogen atoms, also reacted with olefins with high exo‐ and enantioselectivities. The stereoselectivities of the [3+2] cycloadditions with maleate and fumarate suggested that the reaction proceeded by means of a concerted mechanism. An NMR spectroscopic study indicated that complexation of AgHMDS with the bisphosphine ligand was not complete, and that free AgHMDS, which did not show any significant catalytic activity, existed in the catalyst solution. This means that significant ligand acceleration occurred in the current reaction system. 相似文献
989.
A low-cost electrorheological (ER) material made of micro/nano-structured montmorillonite/titania particles was prepared by
a one-pot solvothermal method. The micro/nano-structured particles were characterized by X-ray diffraction, Fourier transform
infrared spectra, and scanning electron microscopy. It was found that the nanorod-like titania assembled on the surface of
montmorillonite, the diameters of the nanorods were about 30 nm, and the lengths were about 300 nm. The electrorheological
property of the micro/nano-structured particles in silicone oil was measured under dc electric fields. It was found that the
micro/nano-structured montmorillonite/titania ER fluid exhibited much stronger electrorheological effect compared to pure
montmorillonite and pure titania nanorod ER fluids, while its leaking current density was significantly lower than that of
montmorillonite ER fluid. The stronger electrorheological effect might be attributed to the larger interfacial polarization
and interparticle friction, which originated from the unique structure and morphology of micro/nano-structured particles,
compared to pure montmorillonite and pure titania nanorods. 相似文献
990.