全文获取类型
收费全文 | 1621篇 |
免费 | 84篇 |
国内免费 | 19篇 |
专业分类
化学 | 1182篇 |
晶体学 | 23篇 |
力学 | 15篇 |
数学 | 117篇 |
物理学 | 387篇 |
出版年
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 38篇 |
2020年 | 19篇 |
2019年 | 27篇 |
2018年 | 23篇 |
2017年 | 20篇 |
2016年 | 32篇 |
2015年 | 36篇 |
2014年 | 42篇 |
2013年 | 77篇 |
2012年 | 99篇 |
2011年 | 118篇 |
2010年 | 59篇 |
2009年 | 61篇 |
2008年 | 83篇 |
2007年 | 96篇 |
2006年 | 81篇 |
2005年 | 101篇 |
2004年 | 100篇 |
2003年 | 97篇 |
2002年 | 83篇 |
2001年 | 23篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 19篇 |
1997年 | 29篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1986年 | 5篇 |
1985年 | 28篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 7篇 |
1961年 | 4篇 |
排序方式: 共有1724条查询结果,搜索用时 31 毫秒
111.
112.
Banás P Otyepka M Jerábek P Petrek M Damborský J 《Journal of computer-aided molecular design》2006,20(6):375-383
1,2,3-Trichloropropane (TCP) is a highly toxic, recalcitrant byproduct of epichlorohydrin manufacture. Haloalkane dehalogenase (DhaA) from Rhodococcus sp. hydrolyses the carbon–halogen bond in various halogenated compounds including TCP, but with low efficiency (k
cat/K
m = 36 s-1 M-1). A Cys176Tyr-DhaA mutant with a threefold higher catalytic efficiency for TCP dehalogenation has been previously obtained by error-prone PCR. We have used molecular simulations and quantum mechanical calculations to elucidate the molecular mechanisms involved in the improved catalysis of the mutant, and enantioselectivity of DhaA toward TCP. The Cys176Tyr mutation modifies the protein access and export routes. Substitution of the Cys residue by the bulkier Tyr narrows the upper tunnel, making the second tunnel “slot” the preferred route. TCP can adopt two major orientations in the DhaA enzyme, in one of which the halide-stabilizing residue Asn41 forms a hydrogen bond with the terminal halogen atom of the TCP molecule, while in the other it bonds with the central halogen atom. The differences in these binding patterns explain the preferential formation of the (R)- over the (S)-enantiomer of 2,3-dichloropropane-1-ol in the reaction catalyzed by the enzyme. 相似文献
113.
The coadsorption of carbon monoxide (CO) and water molecules on a Ru(0 0 1) surface has been studied by infrared spectroscopy, LEED and STM. At high CO coverage phases, a 2×2-(2CO+D2O) structure was observed on both UHV and electrode surfaces. Electrode potential dependent structures from CO and water adlayers on an electrode surface were reproduced on a UHV surface by controlling molecular orientations of the first layer and second over-layer water molecules. At lower CO coverages, a CO band center showed coverage dependent shift down to 1444 cm−1 due to an electron transfer from a lone pair of a water molecule to CO 2π*. 相似文献
114.
Molecular organization in MAPLE‐deposited conjugated polymer thin films and the implications for carrier transport characteristics
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ban Xuan Dong Anton Li Joseph Strzalka Gila E. Stein Peter F. Green 《Journal of Polymer Science.Polymer Physics》2017,55(1):39-48
The morphological structure of poly(3‐hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin‐casting methods are investigated. The MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side‐chain stacking, π–π stacking, and conjugated backbone directions. Moreover, the average molecular orientations and relative degrees of crystallinity of MAPLE‐deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin‐casting technique. Despite the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in‐plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin‐cast samples, exhibiting similar transport activation energies (56 vs. 54 meV) to those reported in the literature for high mobility polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 39–48 相似文献
115.
116.
Masashi Watanabe 《先进技术聚合物》2005,16(10):744-748
In this article the possibility of using various elastic polymer substrates for preparing wrinkled gold films was studied. The gold film was deposited on the substrate using an ion‐sputtering technique, while the substrate was stretched and fixed on a frame. The obtained gold film had wrinkles with a striped pattern. However, whether the pattern was well regulated or not depended on the substrate material. Polydimethylsiloxane (PDMS) was the preferable material when it did not contain fillers. Materials containing fillers are not suitable for this purpose. However, double layer substrates that consist of the PDMS without fillers (the upper layer) and the material containing fillers (the lower layer) could be used to obtain a relatively well‐ordered pattern. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
117.
9,10‐Diaminoanthracenes Revisited: The Influence of N‐Substituents on Their Electronic States
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Masashi Uebe Prof. Dr. Tatsuhisa Kato Prof. Dr. Kazuyoshi Tanaka Dr. Akihiro Ito 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(52):18923-18931
The electronic and molecular structures of 9,10‐diamino‐substituted anthracenes with different N‐substituents have been re‐examined. In particular, different N‐substituents influence both the electronic and molecular structures of the oxidized species of 9,10‐diaminoanthracenes. The anthrylene moiety of 9,10‐bis(N,N‐di(p‐anisyl)amino)anthracene retains its planarity during the course of two successive one‐electron oxidations, whereas 9,10‐bis(N,N‐dimethylamino)anthracene and 9,10‐bis(N‐p‐anisyl‐N‐methylamino)anthracene undergo a substantial structural change to a butterfly‐like structure through a two‐electron oxidation process. The structural changes observed for the oxidized states are ascribed to significant differences in the frontier molecular orbitals of the above‐mentioned three kinds of 9,10‐diaminoanthracenes due to different extents of mixing between the amine‐localized and anthrylene‐localized orbitals. 相似文献
118.
Kato D Masaike M Majima T Hirata Y Mizutani F Sakata M Hirayama C Kunitake M 《Chemical communications (Cambridge, England)》2002,(22):2616-2617
Novel two-dimensional (2D) cross-linked polysiloxane LB films were prepared and applied for glucose sensing as H2O2-permselective films in order to block other electroactive interferences, such as L-ascorbic acid, L-cysteine, uric acid and acetaminophen; the 2D cross-linked polysiloxane monolayers were remarkably effective in eliminating interfering responses and had a rapid response for glucose, even though the films were only a monolayer thick. 相似文献
119.
Krokovny P Abe K Abe K Abe T Adachi I Ahn BS Aihara H Akatsu M Asano Y Aso T Aulchenko V Aushev T Bakich AM Ban Y Banas E Bay A Bedny I Behera PK Bizjak I Bondar A Bozek A Bracko M Brodzicka J Browder TE Casey BC Chang P Chao Y Chen KF Cheon BG Chistov R Choi SK Choi Y Danilov M Dong LY Drutskoy A Eidelman S Eiges V Enari Y Everton CW Fang F Fukunaga C Gabyshev N Garmash A Gershon T Golob B Gordon A Guo R Haba J Hanagaki K Handa F Harada Y Hayashii H Hazumi M Heenan EM Higuchi T Hinz L Hojo T 《Physical review letters》2002,89(23):231804
We report the first observation of a B meson decay that is not accessible by a direct spectator process. The channel B(0)-->D(+)(s)K- is found in a sample of 85 x 10(6) BB; events, collected with the Belle detector at KEKB, with a branching fraction B(B(0)-->D(+)(s)K-)=(4.6(+1.2)(-1.1)+/-1.3) x 10(-5). We also obtain evidence for the B0-->D(+)(s)pi(-) decay with branching fraction B(B0-->D(+)(s)pi(-))=(2.4(+1.0)(-0.8)+/-0.7) x 10(-5). This value may be used to extract a model-dependent value of |V(ub)|. 相似文献
120.
Bai JZ Ban Y Bian JG Chen AD Chen HF Chen HS Chen JC Chen XD Chen YB Cheng BS Chi SP Chu YP Choi JB Cui XZ Dai YS Dong LY Du ZZ Dunwoodie W Fu HY Fu LP Gao CS Gu SD Guo YN Guo ZJ Han SW Han Y Harris FA He J He JT He KL He M He X Hong T Heng YK Hu GY Hu HM Hu QH Hu T Huang GS Huang XP Huang YZ Izen JM Ji XB Jiang CH Jin Y Jones BD Kang JS Ke ZJ Kim HJ Kim SK Kim TY Kong D Lai YF Li D Li HB Li HH Li J Li JC Li PQ Li QJ Li RY Li W Li WG Li XN Li XQ Liu B Liu F Liu F Liu HM Liu J Liu JP Liu TR 《Physical review letters》2002,88(10):101802
We report values of R = sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider. 相似文献