全文获取类型
收费全文 | 1223篇 |
免费 | 104篇 |
出版年
2023年 | 14篇 |
2022年 | 14篇 |
2021年 | 40篇 |
2020年 | 29篇 |
2019年 | 36篇 |
2018年 | 47篇 |
2017年 | 38篇 |
2016年 | 42篇 |
2015年 | 99篇 |
2014年 | 63篇 |
2013年 | 106篇 |
2012年 | 132篇 |
2011年 | 112篇 |
2010年 | 75篇 |
2009年 | 54篇 |
2008年 | 67篇 |
2007年 | 68篇 |
2006年 | 52篇 |
2005年 | 45篇 |
2004年 | 38篇 |
2003年 | 28篇 |
2002年 | 30篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1327条查询结果,搜索用时 15 毫秒
991.
992.
993.
Pavla Bojarov Karel Kenek Marek Kuzma Lucie Petrskov Karel Bezouka Darius-Jean Namdjou Lothar Elling Vladimír Ken 《Journal of Molecular Catalysis .B, Enzymatic》2008,50(2-4):69
A complex trisaccharide β-d-GalpNAcA-(1 → 4)-β-d-GlcpNAc-(1 → 4)-d-ManpNAc (3) was prepared in a good yield (35%) in a transglycosylation reaction catalyzed by β-N-acetylhexosaminidase from Talaromyces flavus using p-nitrophenyl 2-acetamido-2-deoxy-β-d-galacto-hexodialdo-1,5-pyranoside (1) as a donor followed by the in situ oxidation of the aldehyde functionality by NaClO2. The disaccharide β-d-GlcpNAc-(1 → 4)-d-ManpNAc (2) was used as galactosyl acceptor. A disaccharide β-d-GalpNAcA-(1 → 4)-d-GlcpNAc (4; 39%) originated as a by-product in the reaction. Oligosaccharides comprising a carboxy moiety at C-6 are shown to be very efficient ligands to natural killer cell activation receptors, particularly to human receptor CD69. Thus, oxidized trisaccharide 3 is the best-known oligosaccharidic ligand to this receptor, with IC50 = 2.5 × 10−9 M. The presented method of introducing a β-d-GalpNAcA moiety into carbohydrate structures is versatile and can be applied in the synthesis of other complex oligosaccharides. 相似文献
994.
Emily Mulherin Jill Bryan Marijke Beltman Luke O'Grady Eugene Pidgeon Lucie Garon Andrew Lloyd John Bainbridge Helen O'Shea Paul Whyte Séamus Fanning 《BMC veterinary research》2008,4(1):1-8
Background
Results regarding the use of bovine somatotropin for enhancing fertility in dairy cattle are variable. Here, the hypothesis was tested that a single injection of a sustained-release preparation of bovine somatotropin (bST) during the preovulatory period would improve pregnancy success of lactating dairy cows at first service. 相似文献995.
996.
Lucie Laplane 《Biology & philosophy》2018,33(3-4):18
The clonal evolution (CE) model and the cancer stem cell (CSC) model are two independent models of cancers, yet recent data shows intersections between the two models. This article explores the impacts of the CSC model on the CE model. I show that CSC restriction, which depends on CSC frequency in cancer cell populations and on the probability of dedifferentiation of cancer non-stem cells (non-CSCs) into CSCs, can favor or impede some patterns of evolution (linear or branched evolution) and some processes of evolution (drift, evolution by natural selection, complex adaptations). Taking CSC restriction into account for the CE model thus has implications for the way in which we understand the patterns and processes of evolution, and can also provide new leads for therapeutic interventions. 相似文献
997.
Moeller L Grünberg M Zehnsdorf A Aurich A Bley T Strehlitz B 《Journal of biotechnology》2011,153(3-4):133-137
Biosensor-controlled substrate feeding was used in a citric acid production process with the yeast strain Yarrowia lipolytica H222 with glucose as the carbon source. The application of an online glucose biosensor measurement facilitated the performance of long-time repeated fed-batch process with automated bioprocess control. Ten cycles of repeated fed-batch fermentation were carried out in order to validate both the stability of the microorganism for citric acid production and the robustness of the glucose biosensor in a long-time experiment. In the course of this fermentation with a duration of 553 h, a slight loss of productivity from 1.4 g/(L×h) to 1.1 g/(L×h) and of selectivity for citric acid from 91% to 88% was observed. The glucose biosensor provided 6,227 measurements without any loss of activity. 相似文献
998.
Lucie Moeller Andreas Zehnsdorf Andreas Aurich Gerold Barth Thomas Bley Beate Strehlitz 《Engineering in Life Science》2013,13(2):163-171
The genetically modified yeast strain Yarrowia lipolytica H222‐S4(p67ICL1)T5 is able to utilize sucrose as a carbon source and to produce citric and isocitric acids in a more advantageous ratio as compared to its wild‐type equivalent. In this study, the effect of pH of the fermentation broth (pH 6.0 and 7.0) and proteose‐peptone addition on citric acid production by the recombinant yeast strain were investigated. It was found that the highest citric acid production occurred at pH 7.0 without any addition of proteose‐peptone. Furthermore, two process strategies (fed‐batch and repeated fed‐batch) were tested for their applicability for use in citric acid production from sucrose by Y. lipolytica. Repeated fed‐batch cultivation was found to be the most effective process strategy: in 3 days of cycle duration, approximately 80 g/L citric acid was produced, the yield was at least 0.57 g/g and the productivity was as much as 1.1 g/Lh. The selectivity of the bioprocess for citric acid was always higher than 90% from the very beginning of the fermentation due to the genetic modification, reaching values of up to 96.4% after 5 days of cycle duration. 相似文献
999.
Novakova L Ruzicka E Jech R Serranova T Dusek P Urgosik D 《Neuro endocrinology letters》2007,28(1):21-25
Deep brain stimulation of the subthalamic nucleus (DBS STN) is an effective treatment method in advanced Parkinson's disease (PD) providing marked improvement of its major motor symptoms. In addition, non-motor effects have been reported including weight gain in PD patients after DBS STN. Using retrospective survey, we aimed to evaluate weight changes in our patients with advanced PD treated with DBS STN. We inquired 25 PD patients (16 men, 9 women), of mean age 55 (42-65) years, mean PD duration 15 (9-21) years, who previously received bilateral DBS STN. We obtained valid data from 23 patients. In the first survey, 1 to 45 months after DBS, weight gain was found in all patients comparing to pre-DBS period. The mean increase was 9.4 kg (from 1 to 25 kg). The patients' mean body mass index (BMI) increased from 23.7 to 27.0 kg/m2, i.e. by 3.3 kg/m2 (+2 to +6.1 kg/m2). In the repeated survey one year later, in 12 of the patients body weight moderately decreased, 3 did not change, and 6 patients further increased their weight. Possible explanations of body weight gain after DBS STN include a reduction of energy output related to elimination of dyskinesias, improved alimentation or direct influence on function of lateral hypothalamus by DBS STN. 相似文献
1000.
Lucie Crépin Thibault Nidelet Isabelle Sanchez Sylvie Dequin Carole Camarasa 《Applied and environmental microbiology》2012,78(22):8102-8111
The efficiency of nitrogen use is a key determinant of the completion of alcoholic fermentation. We analyzed the kinetics of consumption of 18 nitrogen compounds by 14 Saccharomyces cerevisiae strains of various origins in a synthetic medium that mimicked a grape must. The kinetic profiles of total nitrogen consumption were diverse, but the order of nitrogen source consumption was similar for all strains. The nitrogen compounds could be classified into three groups, according to their order of use: prematurely consumed (Lys), early consumed (Asp, Thr, Glu, Leu, His, Met, Ile, Ser, Gln, and Phe), and late consumed (ammonium, Val, Arg, Ala, Trp, and Tyr). The initial concentrations of these compounds did not alter the order in which they were consumed, except for arginine and ammonium. Early consumed amino acids are transported by specific permeases under Ssy1p-Ptr3p-Ssy5 (SPS)-mediated control that are expressed at the beginning of consumption. Most nitrogen compounds consumed late are transported by permeases under nitrogen catabolite repression (NCR), and others (Val, Trp, and Tyr) are transported by SPS-regulated low-affinity permeases. Therefore, the kinetic characteristics of transporters, as well as SPS and NCR, are likely key factors controlling the temporal sequence of consumption of nitrogen compounds and constitute a system highly conserved in S. cerevisiae species. This work sheds new light on the mechanistic basis of the sequential use of different nitrogen compounds in complex environments. 相似文献