全文获取类型
收费全文 | 694篇 |
免费 | 6篇 |
国内免费 | 5篇 |
专业分类
化学 | 496篇 |
晶体学 | 7篇 |
力学 | 2篇 |
数学 | 41篇 |
物理学 | 159篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2016年 | 9篇 |
2015年 | 9篇 |
2014年 | 12篇 |
2013年 | 32篇 |
2012年 | 24篇 |
2011年 | 33篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 35篇 |
2007年 | 29篇 |
2006年 | 22篇 |
2005年 | 29篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 19篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 7篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 19篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 15篇 |
1980年 | 26篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 12篇 |
1973年 | 9篇 |
1969年 | 4篇 |
排序方式: 共有705条查询结果,搜索用时 15 毫秒
141.
I. Yamamoto N. Matsuura K. Miyakubo T. Yamada T. Munakata 《Journal of Electron Spectroscopy and Related Phenomena》2009,174(1-3):131
A high-precision sample stage for photoemission microscopy has been constructed to translate the sample by ±3 mm with accuracy better than 100 nm. The stage is actuated by step motors settled outside the vacuum. The accuracies of the translations were measured by observing a standard patterned sample with a photoemission electron microscope (PEEM) of 50 nm resolution. The accuracy was nearly independent of the distance of each translation step and the error was not accumulated by repeated steps. After round-trip translations up to 0.2 mm, the sample came back to the original position with accuracy of ±50 nm. The performance of the stage was demonstrated by observing growth processes of lead phthalocyanine (PbPc) films formed on graphite. 相似文献
142.
143.
Giant liposomes, or giant vesicles, are cell-size (approximately 5-100 microm) compartments enclosed with phospholipid bilayers, and have often been used in biological research. They are usually generated using hydration methods, "electroformation" and "gentle hydration (or natural swelling)", in which dry lamellar films of phospholipids are hydrated with aqueous solutions. In gentle hydration, however, giant liposomes are difficult to prepare from an electrostatically neutral phospholipid because lipid lamellae cannot repel each other. In this study, we demonstrate the efficient formation of giant liposomes using the gentle hydration of neutral phospholipid (dioleoyl phosphatidylcholine, DOPC) dry films doped with nonelectrolytic monosaccharides (glucose, mannose, and fructose). A mixture of DOPC and such a sugar in an organic solvent (chloroform/methanol) was evaporated to form the films, which were then hydrated with distilled water or Tris buffers containing sodium chloride. Under these conditions, giant liposomes spontaneously formed rapidly and assumed a swollen cell-sized spherical shape with low lamellarity, whereas giant liposomes from pure DOPC films had multilamellar lipid layers, miscellaneous shapes and smaller sizes. This observation indicates that giant unilamellar vesicles (GUVs) of DOPC can be obtained efficiently through the gentle hydration of sugar-containing lipid dry films because repulsion between lipid lamellae is enhanced by the osmosis induced by dissolved sugar. 相似文献
144.
The excited state intramolecular proton transfer (ESIPT) processes in 3‐methylsalicyclic acid (3‐MeSA) and 3‐methoxysalicyclic acid (3‐MeOSA) have been investigated in cyclohexane medium by emission spectroscopic techniques. The ESIPT process was characterized in 3‐MeSA from the large Stokes fluorescent band (455 nm), but it was suppressed by 3‐MeOSA in cyclohexane. The ESIPT process was found to be accelerated both in 3‐MeSA and 3‐MeOSA in the presence of a hydrogen bond accepting agent, triethylamine (TEA). Further, theoretical calculations were carried out at the ground and excited states to complement the experimental evidences. 相似文献
145.
Local structures of the hydrogenated (Ni0.6Nb0.4)1-xZrx (x = 0.3-0.4) amorphous alloys attract much attention for the sake of their epoch-making electronic transport behaviors. We investigated the local structures by XAFS for the as-quenched (Ni0.6Nb0.4)0.65Zr0.35 and hydrogenated [(Ni0.6Nb0.4)0.65Zr0.35]0.922H0.078 amorphous alloys, in which ballistic conductivity has been observed. XAFS results of the Ni K-edge are analyzed based on the structure model deduced by the first principle calculation. The analysis suggests that highly distorted icosahedral Ni5Nb3Zr5 cluster, which has a centered-Ni and a surrounding Nb triangle, is a main structural unit of (Ni0.6Nb0.4)0.65Zr0.35 and the [(Ni0.6Nb0.4)0.65Zr0.35]0.922H0.078 amorphous alloys. This distorted icosahedral Ni5Nb3Zr5 cluster can be associated with the occurrence of the singular electronic transport behaviors of the hydrogenated (Ni0.6Nb0.4)0.65Zr0.35 alloy. 相似文献
146.
This paper is concerned with data-based selection of the bandwidth for a data sharpening estimator in nonparametric regression. Two kinds of bandwidths are considered: a bandwidth vector which has a different bandwidth for each covariate, and a scalar bandwidth that is common for all covariates. A plug-in method is developed and its theoretical performance is fully investigated. The proposed plug-in method works efficiently in our simulation study. 相似文献
147.
Hao J Matsuura F Kishi Y Kita M Uemura D Asai N Iwashita T 《Journal of the American Chemical Society》2006,128(24):7742-7743
The C34 and C2' stereochemistry of pteriatoxins A-C has been established. The availability of all the stereoisomers via total synthesis has played an indispensable role. 相似文献
148.
Yamada M Yao I Hayasaka T Ushijima M Matsuura M Takada H Shikata N Setou M Kwon AH Ito S 《Analytical and bioanalytical chemistry》2012,402(5):1921-1930
Direct tissue analysis using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) provides the means
for in situ molecular analysis of a wide variety of biomolecules. This technology—known as imaging mass spectrometry (IMS)—allows
the measurement of biomolecules in their native biological environments without the need for target-specific reagents such
as antibodies. In this study, we applied the IMS technique to formalin-fixed paraffin-embedded samples to identify a substance(s)
responsible for the intestinal obstruction caused by an unidentified foreign body. In advance of IMS analysis, some pretreatments
were applied. After the deparaffinization of sections, samples were subjected to enzyme digestion. The sections co-crystallized
with matrix were desorbed and ionized by a laser pulse with scanning. A combination of α-amylase digestion and the 2,5-dihydroxybenzoic
acid matrix gave the best mass spectrum. With the IMS Convolution software which we developed, we could automatically extract
meaningful signals from the IMS datasets. The representative peak values were m/z 1,013, 1,175, 1,337, 1,499, 1,661, 1,823, and 1,985. Thus, it was revealed that the material was polymer with a 162-Da unit
size, calculated from the even intervals. In comparison with the mass spectra of the histopathological specimen and authentic
materials, the main component coincided with amylopectin rather than amylose. Tandem MS analysis proved that the main components
were oligosaccharides. Finally, we confirmed the identification of amylopectin by staining with periodic acid-Schiff and iodine.
These results for the first time show the advantages of MALDI-IMS in combination with enzyme digestion for the direct analysis
of oligosaccharides as a major component of histopathological samples. 相似文献
149.
LK Das SW Park SJ Cho A Ghosh 《Dalton transactions (Cambridge, England : 2003)》2012,41(36):11009-11017
Two new trinuclear hetero-metallic copper(ii)-zinc(ii) complexes [(CuL)(2)Zn(N(3))(2)] ( and ) have been synthesized using [CuL] as a so-called "metalloligand" (where H(2)L = N,N'-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Complexes and have the same molecular formula but crystallize in different crystal systems (triclinic for and monoclinic for ) with space group P1[combining macron] for and P2(1)/c for . is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligand" [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges. The Zn(ii) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal azide ions. In complex , in addition to the double phenoxido bridge, the two terminal Cu(ii) ions are linked to the central Zn(ii) via a μ(-l,l) azido bridge giving rise to a square pyramidal environment around the Cu(ii) ions and consequently the structure becomes linear. These two species can be considered as "linear-bent" isomers. EPR spectra and ESI mass spectra show that the two isomers are identical in solution. The DFT calculation reveals that the energy of is 7.06 kcal mol(-1) higher than that of . The existence of both isomers in the solid state suggests that crystal packing interactions in are more efficient and probably compensate for the difference in energy. 相似文献
150.