全文获取类型
收费全文 | 10397篇 |
免费 | 260篇 |
国内免费 | 46篇 |
专业分类
化学 | 7022篇 |
晶体学 | 125篇 |
力学 | 352篇 |
数学 | 1056篇 |
物理学 | 2148篇 |
出版年
2022年 | 57篇 |
2021年 | 77篇 |
2020年 | 96篇 |
2019年 | 104篇 |
2018年 | 81篇 |
2017年 | 68篇 |
2016年 | 197篇 |
2015年 | 175篇 |
2014年 | 179篇 |
2013年 | 472篇 |
2012年 | 483篇 |
2011年 | 566篇 |
2010年 | 326篇 |
2009年 | 256篇 |
2008年 | 477篇 |
2007年 | 515篇 |
2006年 | 545篇 |
2005年 | 479篇 |
2004年 | 407篇 |
2003年 | 386篇 |
2002年 | 379篇 |
2001年 | 191篇 |
2000年 | 182篇 |
1999年 | 122篇 |
1998年 | 130篇 |
1997年 | 174篇 |
1996年 | 202篇 |
1995年 | 133篇 |
1994年 | 154篇 |
1993年 | 172篇 |
1992年 | 141篇 |
1991年 | 108篇 |
1990年 | 105篇 |
1989年 | 129篇 |
1988年 | 123篇 |
1987年 | 102篇 |
1986年 | 104篇 |
1985年 | 149篇 |
1984年 | 158篇 |
1983年 | 110篇 |
1982年 | 140篇 |
1981年 | 138篇 |
1980年 | 124篇 |
1979年 | 115篇 |
1978年 | 120篇 |
1977年 | 115篇 |
1976年 | 93篇 |
1975年 | 118篇 |
1974年 | 106篇 |
1973年 | 94篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
Shi Nian-Qing Prahl Kristine Hendrick Jim Cruz Jose Lu Ping Cho Jae-Yong Jones Sharon Jeffries Thomas 《Applied biochemistry and biotechnology》2000,84(1-9):201-216
Pichia stipitis CBS 6054 will grow on d-xylose, d-arabinose, and l-arabinose. d-Xylose and l-arabinose are abundant in seed hulls of maize, and their utilization is important in processing grain residues. To elucidate
the degradation pathway for l-arabinose, we obtained a mutant, FPL-MY30, that was unable to grow on d-xylose and l-arabinose but that could grow on d-arabinitol. Activity assays of oxidoreductase and pentulokinase enzymes involved in d-xylose, d-arabinose, and l-arabinose pathways indicated that FPL-MY30 is deficient in d-xylitol dehydrogenase (D-XDH), d- and l-arabinitol dehydrogenases, and d-ribitol dehydrogenase. Transforming FPL-MY30 with a gene for xylitol dehydrogenase (PsXYL2), which was cloned from CBS 6054 (Gen Bank AF127801), restored the D-XDH activity and the capacity for FPL-MY30 to grow on
l-arabinose. This suggested that FPL-MY30 is critically deficient in XYL2 and that the d-xylose and l-arabinose metabolic pathways have xylitolas a common intermediate. The capacity for FPL-MY30 to grow on d-arabinitol could proceed through d-ribulose. 相似文献
84.
Microwave induced delayed phosphorescence (MIDP) measurements have been performed in the 00 bands of the phosphorescence spectrum of benzene dissolved in two phases of cyclohexane. From the relative radiative rates for decay of the three zero-field levels it is concluded that on the average the symmetry of the electronic structure is lower than D2h. In the monoclinic low temperature stable phase of cyclohexane (phase II) the structure is approximately antiquinoidal, and in the metastable phase III it is approximately quinoidal. 相似文献
85.
Paul Schaffer James F. Britten Alan Davison Alun G. Jones John F. Valliant 《Journal of organometallic chemistry》2003,680(1-2):323-328
Two homoleptic Re(I) complexes of ortho and para-carborane isocyanide ligands were prepared as the first examples of a new class of metal-based BNCT and BNCS agents. The target compounds were prepared in low yield through the reaction of [Re2(O2CPh)4Cl2] and [Re2(OAc)4Cl2] with 3-isocyano-1,2-dicarba-closo-dodecaborane and a para-carborane azetidine derivative respectively. The desired product from the latter reaction was characterized crystallographically and is only the second reported molecular structure of a homoleptic Re(I) isonitrile complex. 相似文献
86.
A. S. Paschoa M. Cholewa K. W. Jones N. P. Singh M. E. Wrenn 《Journal of Radioanalytical and Nuclear Chemistry》1987,115(2):231-240
A combination of two techniques, PIXE (particle induced x-ray emission) and RBS (Rutherford backscattering), is proposed as an analytical tool to measure uranium and thorium in environmental and biological samples and in the study of the micro-distribution of uranium is low Z matrices such as biological tissue.Work supported by U.S. Department of Energy Contracts DE-AC02-76CH-00116 (MC, KWJ) and DE-AC02-76EV-00119 (NPS, MEW). One of us (ASP) is grateful to FINEP (Financiadora de Estudos e Projetos) and CNPq (Conselho Nacional de Desenvolvimento Cientifico e Technológico). 相似文献
87.
Pyrolysis of homoadamant-3-ene (), generated from 1-adamantylcarbene (), leads to the same three olefins (, , and ) that are produced from pyrolysis of 3-homoadamantyl acetate (). 相似文献
88.
89.
90.