全文获取类型
收费全文 | 1613篇 |
免费 | 80篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 12篇 |
2021年 | 47篇 |
2020年 | 36篇 |
2019年 | 30篇 |
2018年 | 59篇 |
2017年 | 52篇 |
2016年 | 69篇 |
2015年 | 90篇 |
2014年 | 94篇 |
2013年 | 108篇 |
2012年 | 155篇 |
2011年 | 135篇 |
2010年 | 94篇 |
2009年 | 51篇 |
2008年 | 99篇 |
2007年 | 101篇 |
2006年 | 93篇 |
2005年 | 83篇 |
2004年 | 70篇 |
2003年 | 72篇 |
2002年 | 48篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 12篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1976年 | 1篇 |
排序方式: 共有1693条查询结果,搜索用时 703 毫秒
51.
52.
53.
Anna Gumieniczek Hanna Hopkała Marcin Pruchniak 《Central European Journal of Biology》2007,2(4):538-546
In the present study, the induction of oxidative stress was examined in the testis of alloxan-induced diabetic rabbits. In
addition, the protective effect of repaglinide, an oral anti-diabetic, at a dose of 1 mg daily was studied after four and
eight weeks of the treatment. For these purposes, the levels of superoxide dismutase (Cu,Zn-SOD), catalase (CAT), glutathione
peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione (GSH), ascorbic acid (AA), lipid peroxidation products (LPO)
and protein carbonyl groups (PCG) were quantified. Hyperglycemia resulted in significant increases in the antioxidative enzymes,
Cu, Zn-SOD, CAT, GSH-Px, and GSSG-R after four and eight weeks, respectively. There was also an increase in GSH level, and
a decrease in the level of AA. These effects were accompanied by an elevation in testicular LPO levels and PCG levels. Repaglinide
was found to normalize the activity of GSSG-R and levels of GSH and AA, and blunted the increased lipid peroxidation, however
no decrease in PCG levels were observed. In conclusion, some oxidative changes provoked in the testis of rabbits by hyperglycemia,
were found to be reduced with repaglinide treatment at therapeutic dose. 相似文献
54.
A new smut fungus Ustilago aldabrensis on the grass Dactyloctenium ctenoides is described and illustrated from Aldabra Island in the Seychelles archipelago. It is compared with similar species known
on the genus Dactyloctenium. A further two smut fungi infecting this host plant genus, U. dactyloctenii-gigantei and U. idonea are discussed. U. dactyloctenii-gigantei is reported for the first time from Nigeria on a new host plant, D. aegyptium. U. idonea is redescribed, and its nomenclature and geographical distribution are clarified. A key to smut fungi infecting species of
Dactyloctenium is provided. 相似文献
55.
Dong A Xu X Edwards AM;Midwest Center for Structural Genomics;Structural Genomics Consortium Chang C Chruszcz M Cuff M Cymborowski M Di Leo R Egorova O Evdokimova E Filippova E Gu J Guthrie J Ignatchenko A Joachimiak A Klostermann N Kim Y Korniyenko Y Minor W Que Q Savchenko A Skarina T Tan K Yakunin A Yee A Yim V Zhang R Zheng H Akutsu M Arrowsmith C Avvakumov GV Bochkarev A Dahlgren LG Dhe-Paganon S Dimov S Dombrovski L Finerty P Flodin S Flores A Gräslund S Hammerström M Herman MD Hong BS 《Nature methods》2007,4(12):1019-1021
We tested the general applicability of in situ proteolysis to form protein crystals suitable for structure determination by adding a protease (chymotrypsin or trypsin) digestion step to crystallization trials of 55 bacterial and 14 human proteins that had proven recalcitrant to our best efforts at crystallization or structure determination. This is a work in progress; so far we determined structures of 9 bacterial proteins and the human aminoimidazole ribonucleotide synthetase (AIRS) domain. 相似文献
56.
Marcin Brzeziski Joanna Pyrlik Marcin Churski Ewa Komar Andrzej Zalewski 《Ethology : formerly Zeitschrift fur Tierpsychologie》2019,125(11):791-801
The perception and assessment of predation risk often cause changes in the activities of animals and induce behavioural responses that may in turn affect their movements and distribution. To simulate high predation risk in a midfield pond riparian habitat, we used fresh faeces from ranch American mink Neovison vison and recorded behavioural responses of water voles Arvicola amphibius. In areas where mink odour was deployed, the numbers of captured vole individuals and their trappability were significantly lower than in control areas. Several voles migrated from the zones with deployed mink faeces to the areas without faeces, thus proving that increased predation risk affects the distribution of individuals in a population. The response to mink odour was much more pronounced in females than in males; in areas with deployed mink faeces, not a single female was trapped. We conclude that although American mink is a non‐native, invasive predator, water voles respond to mink odour by reducing their activity and/or by avoiding places with higher predation risk. 相似文献
57.
Augustin Long Marion Jean Muriel Albalat Nicolas Vanthuyne Michel Giorgi Marcin Grecki Jean‐Pierre Dutasta Alexandre Martinez 《Chirality》2019,31(11):910-916
The five‐steps synthesis of a hemicryptophane cage combining a benzene‐1,3,5‐tricarboxamide unit and a cyclotriveratrylene (CTV) moiety is described. Chiral high‐performance liquid chromatography (HPLC) was used to resolve the racemic mixture. The absolute configuration of the isolated enantiomers was assigned by comparison of the experimental electronic circular dichroism (ECD) spectra with the calculated ones. X‐ray molecular structures reveal that the capped benzene‐1,3,5‐tricarboxamide unit adopts a structurally chiral conformation in solid state: the chirality of CTV moiety controls the Λ or Δ orientation of the three amides. 相似文献
58.
Steady-state quenching and time-resolved fluorescence measurements of L-tryptophan binding to the tryptophan-free mutant W19/99F of the tryptophan repressor of Escherichia coli have been used to observe the coreperessor microenvirnment changes upon ligand binding. Using iodide and acrylamide as quenchers, we have resolved the emission spectra of the corepressor into two components. The bluer component of L-tryptophan buried in the holorepressor exhibits a maximum of the fluorescence emission at 336 nm and can be characterized by a Stern–Volmer quenching constant equal to about 2.0–2.3 M–1. The second, redder component is exposed to the solvent and possesses the fluorescence emission and Stern–Volmer quenching constant characteristic of L-tryptophan in the solvent. When the Trp holorepressor is bound to the DNA operator, further alterations in the corepressor fluorescence are observed. Acrylamide quenching experiments indicate that the Stern–Volmer quenching constant of the buried component of the corepressor decreases drastically to a value of 0.56 M–1. The fluorescence lifetimes of L-tryptophan in a complex with Trp repressor decrease substantially upon binding to DNA, which indicates a dynamic mechanism of the quenching process. 相似文献
59.
60.
Dubin G Popowicz G Krajewski M Potempa J Dubin A Holak TA 《Journal of biomolecular NMR》2004,28(3):295-296
The increasing antibiotic resistance of an important human pathogen Staphylococcus aureus calls for the development of new therapeutic strategies. Staphylococcal cysteine proteases have been suggested as targets for such therapies. The recent discovery of staphostatins, specific protein inhibitors of these enzymes, gives prospects for the design and production of synthetic, low molecular weight analogs which might become drugs. We have decided to structurally characterize staphostatin A, a representative inhibitor of staphylococcal cysteine proteases, and to assess its binding mode to the target protease with the view of clarifying the specificity determinants. Here we report the (1)H, (15)N and (13)C NMR resonance assignments of staphostatin A. 相似文献