全文获取类型
收费全文 | 338篇 |
免费 | 4篇 |
国内免费 | 4篇 |
专业分类
化学 | 157篇 |
晶体学 | 1篇 |
力学 | 12篇 |
数学 | 71篇 |
物理学 | 105篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 17篇 |
2012年 | 19篇 |
2011年 | 18篇 |
2010年 | 6篇 |
2009年 | 9篇 |
2008年 | 15篇 |
2007年 | 13篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 9篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1975年 | 4篇 |
1972年 | 2篇 |
1970年 | 3篇 |
1965年 | 2篇 |
1956年 | 1篇 |
1936年 | 1篇 |
1935年 | 4篇 |
排序方式: 共有346条查询结果,搜索用时 31 毫秒
91.
To provide photostabilization for entomopathogenic fungi by anionic dyes, composite matrices based on clay-biopolymer combinations were prepared. In the first step, the negative surface charge of various clays (montmorillonite, attapulgite, bentonite and kaolinite) was reversed to positive by adsorption to the polycationic biopolymer chitosan. The second step involved adsorption of the toxicologically safe anionic dyes fast green (FG) and naphthol yellow S (NYS) to the clay complexes. Compared with cytotoxic photoprotectants like berberine, palmatine and acriflavine, the anionic dyes have no adverse effects up to a concentration of 1 M. In assays using various clay-chitosan-dye matrices and UV irradiation from a lamp source, it was evident that both FG and NYS provided considerable photostabilization for conidia of the entomopathogenic fungus Aschersonia spp. that served as a model biocontrol agent. Apparently, because of the light-dispersing property, bentonite and attapulgite per se provided significant photoprotection. All clay matrices containing FG provided a substantial photostabilization effect. 相似文献
92.
Side-chain liquid crystal polyacrylates and polysiloxanes containing different photochromic spironaphthoxazine side groups were synthesized. Thermodynamic, spectral and kinetic properties of the polymers were investigated. The structure of the mesophase is discussed. 相似文献
93.
Agarose acrobeads were produced by encapsulating polyacrolein microspheres (acrobeads) of 0.2 μm average diameter within an
agarose matrix. Crosslinked agarose acrobeads of diameters ranging from 0.5 to 0.8 mm were found to be optimal spheres for
specific hemoperfusion purposes. Agarose provides the biocompatibility and mechanical strength of the agarose acrobeads. Acrobeads
contain a high aldehyde-group content through which various amino ligands, i.e., proteins, antigens, antibodies, enzymes,
and so on, can be covalently bound in a single step under physiological pH (or other pH). Thus, antibodies, antigens, or toxic
materials may be directly removed from whole blood by hemoperfusion. During in vitro and in vivo hemoperfusion trials, the
content of erythrocytes, leukocytes, and thrombocytes was essentially unaltered. Likewise, a battery of the soluble blood
components (Cl-, K+, Na+, Ca2+, PO
4
-
), total proteins, albumin, and C
4
′
component of the complement cascade, as well as the enzymes SGOT, LDH, and alkaline phosphatase, remained constant within
narrow limits during the hemoperfusion procedure. The chemical and physical structure of the beads is stable; neither acrolein
nor bead fragments were detected in hemoperfusion trials. Similarly, leakage of antibody bound to the agarose acrobeads into
the blood is insignificant.
Thus far, we have demonstrated the efficacy of the crosslinked agarose acrobeads for extracorporeal removal of “unwanted”
substances from whole blood in the following systems: (a) removal of specific antigens (digoxin or paraquat removal with antidigoxin
or antiparaquat antibodies bound to the acrobeads, respectively), (b) removal of specific antibody (antiBSA) removal with
BSA bound to the beads), (c) removal of immune complexes (BSA-antiBSA complex removal with C1q bound to acrobeads), and (d)
removal of specific metals (removal of iron with deferoxamine bound to the agarose acrobeads). 相似文献
94.
Glaser Robert Geresh Shimona Luria Shlomo Drouin Marc Michel André 《Structural chemistry》1994,5(4):277-282
Hydrogenation ofZ-(–)-(1R, 3R, 4S)-menthyl 2-formamido-4,4,4-trifluoro-2-butenoate catalyzed by Pd/C was performed at atmospheric pressure to yield a mixture of (2R, 1R, 3R, 4S)- and (2S, 1R, 3R, 4S)-menthyl 2-formamido-4,4,4-trifluorobutanoate diastereomers in a 5545 ratio, respectively. Repeated fractional crystallization from ethyl acetate and vapor diffusion of petroleum ether afforded (+)–(2S, 1R, 3R, 4S)-menthyl 2-formamido-4,4,4-trifluorobutanoate as clear colorless, crystalline prisms which were subjected to single-crystal X-ray diffraction analysis. The crystals belong to the orthorhombic system P212121, and at 213 K:a=5.054(1),b= 10.000(2),c=32.707(1) Å,V=1652.9(4) Å3,Z=4,R(F)=0.040, andR
w
(F)=0.037. The finding of the (2S)-configuration for the formamido-acid portion of the (+)-ester enabled the configurational assignment of the asymmetric hydrogenation products ofZ-methyl 2-formamido-4, 4,4-trifluoro-2-butenoate catalyzed by chiral diphosphine/rhodium(I) complexes. 相似文献
95.
Three different forms of perturbation theories, variational perturbation, finite perturbation and second-order, are evaluated regarding their value for calculation of electronic polarizabilities of small and intermediate size molecules. It is concluded that with the practical constraint of a small basis set the variational perturbation method is the most promising alternative for calculation of polarizabilities. For several small molecules, our calculated polarizabilities indicate that both IEHT and ab initio wave functions give values in close agreement with each other. Variational perturbation calculations of polarizabilities with IEHT wave functions also include the DNA bases. 相似文献
96.
Secondary esters and those with sterical hindrance at the beta carbon were reacted with base, carbon disulfide, and methyl iodide to produce methyl 2-carboalkoxydithioalkenoate (2). These compounds were reacted with BrF(3), forming the corresponding alpha-trifluoromethyl esters (3) along with 1,1-difluoro-2-trifluoromethyl-2-alkyl ethers (4). The products of type 4 have been transformed to derivatives of type 3, thus raising the overall yields of the target respective alpha-trifluoromethyl esters to 65-80%. The reaction is tolerant to different functional groups such as halogens, protected alcohols, esters, and lactones. 相似文献
97.
Anna Galperin Shlomo Margel 《Journal of polymer science. Part A, Polymer chemistry》2006,44(12):3859-3868
Radiopaque microspheres of sizes ranging from 0.2 to 1.4 μm were formed by the dispersion polymerization of the monomer 2‐methacryloyloxyethyl(2,3,5‐triiodobenzoate) in 2‐methoxyethanol. The effects of various polymerization parameters, including the monomer concentration, initiator type and concentration, and stabilizer molecular weight and concentration, on the molecular weight, size, and size distribution of the particles were elucidated. The characterization of these iodinated microspheres was accomplished with routine methods such as Fourier transform infrared, nuclear magnetic resonance, thermogravimetric analysis, differential scanning calorimetry, gel permeation chromatography, scanning electron microscopy, Brunauer–Emmett–Teller measurements, and elemental analysis. Because of the presence of iodine atoms in these microspheres, they were expected to possess a radiopaque nature. The radiopacity of these particles dispersed in water and in the dry state was demonstrated with an imaging technique based on X‐ray absorption usually used in hospitals. These novel radiopaque microspheres may be used for different X‐ray imaging needs, such as blood pooling, body organs, embolization, dental compositions, implants, prostheses, and nanocomposites. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3859–3868, 2006 相似文献
98.
Roee Engelberg Jochen Knemann Stefano Leonardi Joseph Naor 《Journal of Discrete Algorithms》2007,5(2):262-279
We study budgeted variants of classical cut problems: the Multiway Cut problem, the Multicut problem, and the k-Cut problem, and provide approximation algorithms for these problems. Specifically, for the budgeted multiway cut and the k-cut problems we provide constant factor approximation algorithms. We show that the budgeted multicut problem is at least as hard to approximate as the sparsest cut problem, and we provide a bi-criteria approximation algorithm for it. 相似文献
99.
Rappport A. Glaser O. Folin A. Svedberg L. Cuny J. Robert H. Cordebard F. W. Allen J. M. Luck P. Wenger Ch. Cimerman A. Maulbetsch K. Lang K. Hinsberg D. Laszlo M. T. Hanke K. K. Koessler J. M. Looney Z. Dische C. van Zijp H. Engelberg und G. Plancher 《Fresenius' Journal of Analytical Chemistry》1935,101(7-8):312-320
Ohne Zusammenfassung 相似文献
100.
M. Stschigol Rappaport A. Glaser O. Folin A. Svedberg L. Cuny J. Robert H. Cordebard F. W. Allen J. M. Luck P. Wenger Ch. Cimerman A. Maulbetsch K. Lang K. Hinsberg D. Laszlo M. T. Hanke K. K. Koessler J. M. Looney Z. Dische C. van Zijp F. Rappaport H. Engelberg und G. Plancher 《Fresenius' Journal of Analytical Chemistry》1935,101(7-8):312
Ohne Zusammenfassung 相似文献