全文获取类型
收费全文 | 1098篇 |
免费 | 9篇 |
国内免费 | 12篇 |
专业分类
化学 | 611篇 |
晶体学 | 5篇 |
力学 | 35篇 |
数学 | 325篇 |
物理学 | 143篇 |
出版年
2019年 | 6篇 |
2016年 | 11篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 31篇 |
2012年 | 24篇 |
2011年 | 36篇 |
2010年 | 20篇 |
2009年 | 21篇 |
2008年 | 38篇 |
2007年 | 50篇 |
2006年 | 33篇 |
2005年 | 41篇 |
2004年 | 39篇 |
2003年 | 29篇 |
2002年 | 28篇 |
2001年 | 24篇 |
2000年 | 15篇 |
1999年 | 12篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 13篇 |
1995年 | 23篇 |
1994年 | 22篇 |
1993年 | 13篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 21篇 |
1986年 | 33篇 |
1985年 | 28篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1980年 | 29篇 |
1979年 | 31篇 |
1978年 | 22篇 |
1977年 | 10篇 |
1976年 | 19篇 |
1975年 | 19篇 |
1974年 | 27篇 |
1973年 | 20篇 |
1972年 | 15篇 |
1971年 | 15篇 |
1970年 | 13篇 |
1969年 | 6篇 |
1968年 | 8篇 |
排序方式: 共有1119条查询结果,搜索用时 15 毫秒
11.
Aihara H Alston-Garnjost M Avery RE Barbaro-Galtieri A Barker AR Barnes AV Barnett BA Bauer DA Bengtsson H Bintinger DL Bobbink GJ Bolognese TS Bross AD Buchanan CD Buijs A Cain MP Caldwell DO Clark AR Cowan GD Crane DA Dahl OI Derby KA Eastman JJ Eberhard PH Eisner AM Enomoto R Erné FC Fujii T Gary JW Gorn W Hauptman JM Hofmann W Huth JE Hylen J Kamae T Kaye HS Kees KH Kenney RW Kerth LT Ko W Koda RI Kofler RR Kwong KK Lander RL Langeveld WG Layter JG Linde FL Lindsey CS Loken SC Lu A Lu X 《Physical review letters》1986,57(8):945-948
12.
Ionic conductivity of electroporated lipid bilayer membranes 总被引:1,自引:0,他引:1
13.
Eberhard Hohaus 《Monatshefte für Chemie / Chemical Monthly》1980,111(4):863-875
The i.r., u. v.,1H n.m.r.,13C n.m.r., and11B n.m.r. spectra of several substituted diphenylboron chelates derived from salicylaldehyde azomethines were compared with respect to the influence of the amine substituentR. O–B–N-6-ring constitution of the chelates29–32 [R=OH, NH2, NHC6H5, N(CH3)2] can be deduced from the spectra.
Als 3. Mitt. gilt:F. Umland undE. Hohaus mit Beiträgen vonW. Riepe, K. Brodte, C. Schleyerbach undD. Szonn. Untersuchungen über borhaltige Ringsysteme vom Chelattyp. Forschungsbericht des Landes Nordrhein-Westfalen Nr. 2538. Opladen: Westdeutscher Verlag. 1976. 相似文献
14.
Eberhard Bothe Helmut Gorner Joachim Opitz Dietrich Schulte-Frohlinde Aslam Siddiqi Malgorzata Wala 《Photochemistry and photobiology》1990,52(5):949-959
Double-stranded (ds) calf thymus DNA (0.4 mM), excited by 20 ns laser pulses at 248 nm, was studied in deoxygenated aqueous solution at room temperature and pH 6.7 in the presence of a sodium salt (10 mM). The quantum yields for the formation of hydrated electrons (phi c-), single-strand breaks (phi ssb) and double-strand breaks (phi dsb) were determined for various laser pulse intensities (IL). phi c- and phi ssb increase linearly with increasing IL; however, phi ssb has a tendency to reach saturation at high IL (greater than 5 X 10(6) Wcm-2). The ratio phi ssb/phi c-, representing the number of ssb per radical cation, is about 0.08 at IL less than or equal to 5 X 10(6) Wcm-2. For comparison, the number of ssb per OH radical reacting with dsDNA is 0.22. On going from argon to N2O saturation, phi ssb and phi dsb become larger by factors of approximately 5 and 10-15, respectively. This enhancement is produced by attack on DNA bases by OH radicals generated by N2O-scavenging of the photoelectrons. While phi ssb is essentially independent of the dose (Etot), phi dsb depends linearly on Etot in both argon- and N2O-saturated solutions. The linear dependence of phi dsb implies a square dependence of the number of dsb on Etot. This portion of dsb formation is explained by the occurrence of two random ssb, generated within a critical distance (h) in opposite strands. For both argon- and N2O-saturated solutions h was found to be of the order of 40-70 phosphoric acid diester bonds. On addition of electron scavengers such as 2-chloroethanol (or N2O plus t-butanol), phi dsb is similar to that in neat, argon-saturated solutions. Thus, hydrated electrons are not involved in the chemical pathway leading to laser-pulse-induced dsb of DNA. 相似文献
15.
The azido tetrazolo valence isomerism of twenty 9-methyl-s-triazolo[4,3-c]tetrazolo[1,5-a]pyrimidines with different substituents at position 5 has been studied by means of 1H NMR spectroscopy. All the compounds have been found to be tetrazoles in the solid state and in (CD3)2SO solution; in CF3COOH azido and tetrazolo isomers are in equilibrium. From equilibrium constants K and thermodynamic data determined it is concluded that in this series K depends on both electronic effects and steric requirements of the 5-substituents. A linear relation between K and σ was found for 5-arylderivatives because ΔS° keeps approximately constant and the substituent mainly operates on ΔH°. 相似文献
16.
17.
Juraj Pavlinec Eberhard Borsig 《Journal of polymer science. Part A, Polymer chemistry》1981,19(9):2305-2312
A study was made of the methyl methacrylate (MMA) solution polymerization in CCl4-pyridine mixtures as well as in net components at 30, 50, and 70°C. The results obtained show that there are no significant deviations from additivity in the overall chain transfer constants that fit the straight line between the values of Cs for CCl4 and pyridine. It can be concluded that the EDA interaction between CCl4 and pyridine does not change the sensitivity of each component for chain transfer from propagation PMMA free radical. The pyridine in the system increases the rate of MMA polymerization as a result of the higher rate of initiation. 相似文献
18.
Eberhard M. Schröder 《Journal of Geometry》1995,53(1-2):167-178
Letq be a regular quadratic form on a vector space (V, $\mathbb{F}$ ) and assume dimV ≥ 4 and ¦ $\mathbb{F}$ ¦ ≥ 4. We consider a permutation ? of the central affine quadric $\mathcal{F}$ := {x εV ¦q(x) = 1} such that $$(*)x \cdot y = \mu \Leftrightarrow x^\varphi \cdot y^\varphi = \mu \forall x,y\varepsilon \mathcal{F}$$ holds true, where μ is a fixed element of $\mathbb{F}$ and where “·” is the scalar product associated withq. We prove that ? is induced (in a certain sense) by a semi-linear bijection (σ,?): (V, $\mathbb{F}$ ) → (V, $\mathbb{F}$ ) such thatq o ?o q, provided $\mathcal{F}$ contains lines and the pair (μ, $\mathbb{F}$ ) has additional properties if there ar no planes in $\mathcal{F}$ . The cases μ,≠ 0 and μ = 0 require different techniques. 相似文献
19.
We consider the differential equation on a finite interval I, where I contains m turning points, that is here, zeros of ?. Using asymptotic estimates proved by R. E. LANGER for solutions of (*) for intervals containing only one turning point we derive asymptotic estimates (for ρ → ) for a special fundamental system of solutions of (*) in I. The results obtained are fundamental for the investigation of eigenvalue problems defined by (*) and suitable boundary conditions. 相似文献
20.
LetG(V,E) be a graph. A mappingf:E{0,1}
m
is called a (binary) coding ofG, if the induced mapping
, assigns different vectors to the vertices. For the Boolean sum,f is called aB-code, and for the mod 2 sum anM-code. Letm
B
(G) resp.m
M
(G) be the smallest lengthm for whichB-codes resp.M-codes are possible. Trivially,m
B
(G),m
M
(G) log2|V|. Improving results of Z. Tuza we showm
B
(G)log2|V| + 1,m
M
(G)log2|V|+4. 相似文献