全文获取类型
收费全文 | 2270篇 |
免费 | 104篇 |
国内免费 | 9篇 |
专业分类
化学 | 1538篇 |
晶体学 | 13篇 |
力学 | 77篇 |
数学 | 333篇 |
物理学 | 422篇 |
出版年
2023年 | 19篇 |
2022年 | 50篇 |
2021年 | 51篇 |
2020年 | 59篇 |
2019年 | 71篇 |
2018年 | 51篇 |
2017年 | 37篇 |
2016年 | 99篇 |
2015年 | 68篇 |
2014年 | 79篇 |
2013年 | 143篇 |
2012年 | 159篇 |
2011年 | 167篇 |
2010年 | 103篇 |
2009年 | 85篇 |
2008年 | 147篇 |
2007年 | 129篇 |
2006年 | 104篇 |
2005年 | 103篇 |
2004年 | 100篇 |
2003年 | 71篇 |
2002年 | 87篇 |
2001年 | 29篇 |
2000年 | 32篇 |
1999年 | 19篇 |
1998年 | 24篇 |
1997年 | 18篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 15篇 |
1979年 | 14篇 |
1978年 | 19篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1912年 | 3篇 |
排序方式: 共有2383条查询结果,搜索用时 31 毫秒
21.
Amino‐alcohol derivatives of fragrant, volatile aldehydes and ketones were synthesized in a one‐pot procedure by sequential cyanohydrin formation with trimethylsilyl cyanide and reduction with lithium aluminium hydride, or by ammonolysis of epoxide precursors. The amino alcohols are nonvolatile, stable properfumes releasing fragrant carbonyls by oxidation with sodium periodate or sodium bismuthate. Examples include amino alcohol properfumes of citronellal, Lilial®, lauryl aldehyde, menthone, benzaldehyde, and anisaldehyde. 相似文献
22.
Elena V Chubarova Denis G. Samsonenko Maxim N. Sokolov Olga A. Gerasko Vladimir P. Fedin Javier G. Platas 《Journal of inclusion phenomena and macrocyclic chemistry》2004,48(1-2):31-35
A new inclusion compound which is a supramolecular adduct of cucurbit[8]uril with two guest molecules of phenylphosphonic acid, PhP(O)(OH)2, included into the cavity as ``two guests in host'' is reported. The guests match both size and hydrophilicity/hydrophobicity requirements. Two phenyl groups of molecules of PhP(O)(OH)2 are directed toward the center of the large hydrophobic cavity whereas the PO(OH)2 groups are outward-looking and bound with each hydrophilic portal of cucurbit[8]uril by a short hydrogen bond. 相似文献
23.
Denis Kiely 《Journal of organometallic chemistry》2003,687(2):545-561
The synthesis of two novel cyclisation substrates for the asymmetric intramolecular Heck reaction is reported. Their cyclisation, in addition to a known substrate for cis-decalin formation, were tested with palladium complexes of BINAP and heterobidentate oxazoline-containing ligands. In general BINAP provides a more active catalyst system for the range of substrates tested although excellent enantioselectivities of up to 85% were obtained with the P,N ligands studied. A trend was noted whereby the t-leucine-derived oxazoline ligands were more reactive and enantioselective than the valine-derived analogues. Similarly, the diphenylphosphinoferrocenyloxazoline ligands were more reactive and selective than the corresponding diphenylphosphinophenyloxazoline ligands. 相似文献
24.
Islangulov RR Kozlov DV Castellano FN 《Chemical communications (Cambridge, England)》2005,(30):3776-3778
Selective low energy excitation of the metal-to-ligand charge transfer (MLCT) transition in [Ru(dmb)(3)](2+)(dmb = 4,4'-dimethyl-2,2'-bipyridine) in the presence of anthracene or 9,10-diphenylanthracene yields easily visualized upconverted singlet fluorescence resulting from triplet-triplet annihilation at low excitation power. 相似文献
25.
De Jonghe S Lamote I Venkataraman K Boldin SA Hillaert U Rozenski J Hendrix C Busson R De Keukeleire D Van Calenbergh S Futerman AH Herdewijn P 《The Journal of organic chemistry》2002,67(3):988-996
The synthesis of a new series of D-erythro-homoceramide analogues is described. Several synthetic approaches were investigated. Homoceramides can be successfully synthesized from L-homoserine as chiral building block and a protected Weinreb-amide as a key intermediate. The synthesis of short-chain analogues with a heptyl side chain, as well as with a phenyl residue in the sphingoid part (instead of the naturally occurring tridecyl side chain), was effected. The homoceramides 15-17 and 24 were investigated for their potential to reverse the inhibitory effect of fumonisin B(1) on axonal growth. Unfortunately, none of the tested compounds showed any biological activity due to their lack of metabolism to glucosylhomoceramide. 相似文献
26.
Buneva VN Kanyshkova TG Vlassov AV Semenov DV Khlimankov DYu Breusova LR Nevinsky GA 《Applied biochemistry and biotechnology》1998,75(1):63-76
Various catalytically active antibodies (Abs), or abzymes, have been detected recently in the sera of patients with autoimmune
pathologies, in whom their presence is probably associated with autoimmunization. Normal humans are generally not considered
to have abzymes, since no obvious immunizing factors are present. Here is shown by different methods that IgG from the milk
of normal females possesses both DNase and RNase activities. The activities were also present in the IgG F(ab′)2 and Fab fragments.
Affinity modification of IgG by the chemically reactive derivative of an oligonucleotide led to preferential modification
of the L chain of IgG. After separation of the subunits by sodium dodecyl sulfate electrophoresis in a gel containing DNA,
an in-gel assay showed DNase activity in the L chain. The L chain separated by affinity chromatography on DNA-cellulose was
catalytically active. These findings speak in favor of the generation of cat alytic Abs by the immune system of healthy mothers.
It is known that the treatment of adults with DNases and RNases offers protection from viral and bacterial diseases. Since
breast milk protects the infants from infec tions until the immune system is developed, this raises the possibility that catalytic
Abs like nucleases, may possess a protective role. 相似文献
27.
Pavel M. Bleher Denis V. Kosygin Yakov G. Sinai 《Communications in Mathematical Physics》1995,170(2):375-403
We consider the Weyl asymptotic formula
相似文献
28.
Photolysis of complexes of the type M(2)(CO)(6)(RC(5)H(4))(2) (where M = W, Mo, Cr and R = H (Cp) or CH(3) (Cp')) leads to the production of short lived 17-electron radicals. Direct electrochemical characterization of these intermediates has been achieved using a technique known as photomodulated voltammetry (PMV). The results from PMV analysis are in excellent agreement with literature estimates for CpMo(CO)(3)(*) and CpCr(CO)(3)(*). However, CpW(CO)(3)(*) is found to be shifted oxidatively 115 mV relative to previous literature estimates. The change in the value for the tungsten complex changes previous estimates to the bond dissociation energy for tungsten metal hydrides by 3.0 +/- 0.9 kcal/mol. Lifetime information on the radicals is also reported based on the phase shift of the electrochemical signal observed by PMV under limiting current conditions. 相似文献
29.
Andrzej Machocki Tadeusz Borowiecki Andrezej Denis 《Reaction Kinetics and Catalysis Letters》1993,51(2):541-545
The studies of the influence of the kind of natural calcium mineral and the kind and amount of sodium promoter on the conversion degree of methane and oxygen, selectivity and yield of the oxidative conversion of methane have shown the usability of limestone as a basic component of the catalyst for this process. 相似文献
30.
We study the Hermite transform onL
2() where is a Gaussian measure on a Lusin locally convex spaceE. We are then lead to a Hilbert space () of analytic functions onE which is also a natural range for the Laplace transform. LetB be a convenient Hilbert-Schmidt operator on the Cameron-Martin spaceH of . There exists a natural sequence Cap
n
of capacities onE associated toB. This implies the Kondratev-Yokoi theorem about positive linear forms on the Hida test-functions space. 相似文献
|