全文获取类型
收费全文 | 2313篇 |
免费 | 260篇 |
出版年
2022年 | 17篇 |
2021年 | 25篇 |
2019年 | 18篇 |
2018年 | 30篇 |
2017年 | 21篇 |
2016年 | 41篇 |
2015年 | 73篇 |
2014年 | 81篇 |
2013年 | 86篇 |
2012年 | 119篇 |
2011年 | 103篇 |
2010年 | 85篇 |
2009年 | 58篇 |
2008年 | 127篇 |
2007年 | 117篇 |
2006年 | 107篇 |
2005年 | 90篇 |
2004年 | 83篇 |
2003年 | 94篇 |
2002年 | 67篇 |
2001年 | 74篇 |
2000年 | 86篇 |
1999年 | 73篇 |
1998年 | 27篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 21篇 |
1993年 | 19篇 |
1992年 | 61篇 |
1991年 | 37篇 |
1990年 | 37篇 |
1989年 | 35篇 |
1988年 | 39篇 |
1987年 | 35篇 |
1986年 | 34篇 |
1985年 | 33篇 |
1984年 | 19篇 |
1983年 | 30篇 |
1981年 | 19篇 |
1980年 | 24篇 |
1979年 | 35篇 |
1978年 | 18篇 |
1977年 | 19篇 |
1976年 | 18篇 |
1975年 | 17篇 |
1974年 | 33篇 |
1970年 | 16篇 |
1969年 | 18篇 |
1968年 | 18篇 |
排序方式: 共有2573条查询结果,搜索用时 31 毫秒
231.
The aim of the study was to determine the impact of demographic and anthropometric parameters on the gastric myoelectrical activity characteristics in a healthy Croatian population. The influence of age, sex, body mass index (BMI) and menstrual cycle phase on the gastric myoelectrical activity characteristics was assessed. The study included 120 healthy subjects of both sexes (60 male and 60 female), divided into four age groups (18-35, 36-50, 51-65 and > 65 years) and three BMI groups (BMI < 25, 25-30 and > 30). Female subjects of reproductive age were divided into three groups according to menstrual cycle phase (day 1-3, day 4-8 and day 9-20 of menstruation). All study subjects underwent percutaneous electrogastrography (EGG) for 60 min before and 60 min after a test meal. The following parameters of the gastric myoelectrical activity were observed: dominant frequency (DF); dominant frequency within normal range (DFNR, %); coefficient of variation for dominant frequency (CVDF); dominant strength (DS. mV); postprandial increase intensity in dominant strength (PPIIDS, %); bradygastria (BG, c/min, %); tachygastria (TG, c/min, %); and arrhythmia (AR). Age was found to influence preprandial but not postprandial DFNR, CVDF and AR. Sex influenced preprandial DF, CVDF, DS and BG, and postprandial DF, CVDF, PPIIDS and TG. BMI exerted an impact on preprandial TG and AR, and postprandial DF, CVDF and AR. The phase of menstrual cycle influenced DF in preprandial period and none of EGG parameters in postprandial period. 相似文献
232.
Rowbottom MW Vickers TD Tamiya J Zhang M Dyck B Grey J Schwarz D Heise CE Hedrick M Wen J Tang H Wang H Fisher A Aparicio A Saunders J Goodfellow VS 《Bioorganic & medicinal chemistry letters》2007,17(8):2171-2178
The design, synthesis, and SAR of a series of substituted spirohydantoins are described. Optimization of an in-house screening hit gave compounds that exhibited potent binding affinity and functional activity at MCH-R1. 相似文献
233.
Asterless is a centriolar protein required for centrosome function and embryo development in Drosophila 总被引:1,自引:0,他引:1
Varmark H Llamazares S Rebollo E Lange B Reina J Schwarz H Gonzalez C 《Current biology : CB》2007,17(20):1735-1745
BACKGROUND: Centrosomes, the major organizers of the microtubule network in most animal cells, are composed of centrioles embedded in a web of pericentriolar material (PCM). Recruitment and stabilization of PCM on the centrosome is a centriole-dependent function. Compared to the considerable number of PCM proteins known, the molecular characterization of centrioles is still very limited. Only a few centriolar proteins have been identified so far in Drosophila, most related to centriole duplication. RESULTS: We have cloned asterless (asl) and found that it encodes a 120 kD highly coiled-coil protein that is a constitutive pancentriolar and basal body component. Loss of asl function impedes the stabilization/maintenance of PCM at the centrosome. In embryos deficient for Asl, development is arrested right after fertilization. Asl shares significant homology with Cep 152, a protein described as a component of the human centrosome for which no functional data is yet available. CONCLUSIONS: The cloning of asl offers new insight into the molecular composition of Drosophila centrioles and a possible model for the role of its human homolog. In addition, the phenotype of asl-deficient flies reveals that a functional centrosome is required for Drosophila embryo development. 相似文献
234.
Reichardt I Stierhof YD Mayer U Richter S Schwarz H Schumacher K Jürgens G 《Current biology : CB》2007,17(23):2047-2053
During plant cytokinesis membrane vesicles are efficiently delivered to the cell-division plane, where they fuse with one another to form a laterally expanding cell plate. These membrane vesicles were generally believed to originate from Golgi stacks. Recently, however, it was proposed that endocytosis contributes substantially to cell-plate formation. To determine the relative contributions of secretory and endocytic traffic to cytokinesis, we specifically inhibited either or both trafficking pathways in Arabidopsis. Blocking traffic to the division plane after the two pathways had converged at the trans-Golgi network disrupted cytokinesis and resulted in binucleate cells, whereas impairment of endocytosis alone did not interfere with cytokinesis. By contrast, inhibiting ER-Golgi traffic by eliminating the relevant BFA-resistant ARF-GEF caused retention of newly synthesized proteins, such as the cytokinesis-specific syntaxin KNOLLE in the ER, and prevented the formation of the partitioning membrane. Our results suggest that during plant cytokinesis, unlike animal cytokinesis, protein secretion is absolutely essential, whereas endocytosis is not. 相似文献
235.
The Arabidopsis MATE transporter TT12 acts as a vacuolar flavonoid/H+ -antiporter active in proanthocyanidin-accumulating cells of the seed coat 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《The Plant cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Marinova K Pourcel L Weder B Schwarz M Barron D Routaboul JM Debeaujon I Klein M 《The Plant cell》2007,19(6):2023-2038
Phenotypic characterization of the Arabidopsis thaliana transparent testa12 (tt12) mutant encoding a membrane protein of the multidrug and toxic efflux transporter family, suggested that TT12 is involved in the vacuolar accumulation of proanthocyanidin precursors in the seed. Metabolite analysis in tt12 seeds reveals an absence of flavan-3-ols and proanthocyanidins together with a reduction of the major flavonol quercetin-3-O-rhamnoside. The TT12 promoter is active in cells synthesizing proanthocyanidins. Using translational fusions between TT12 and green fluorescent protein, it is demonstrated that this transporter localizes to the tonoplast. Yeast vesicles expressing TT12 can transport the anthocyanin cyanidin-3-O-glucoside in the presence of MgATP but not the aglycones cyanidin and epicatechin. Inhibitor studies demonstrate that TT12 acts in vitro as a cyanidin-3-O-glucoside/H(+)-antiporter. TT12 does not transport glycosylated flavonols and procyanidin dimers, and a direct transport activity for catechin-3-O-glucoside, a glucosylated flavan-3-ol, was not detectable. However, catechin-3-O-glucoside inhibited TT12-mediated transport of cyanidin-3-O-glucoside in a dose-dependent manner, while flavan-3-ol aglycones and glycosylated flavonols had no effect on anthocyanin transport. It is proposed that TT12 transports glycosylated flavan-3-ols in vivo. Mutant banyuls (ban) seeds accumulate anthocyanins instead of proanthocyanidins, yet the ban tt12 double mutant exhibits reduced anthocyanin accumulation, which supports the transport data suggesting that TT12 mediates anthocyanin transport in vitro. 相似文献
236.
Tully TP Bergum JS Schwarz SR Durand SC Howell JM Patel RN Cino PM 《Journal of industrial microbiology & biotechnology》2007,34(3):193-202
BMS-353645, also known as sordarin, was of interest based on its activity against pathogenic fungi. The objective of these
studies was to provide high quality starting substrate for chemical modification aimed at further improving biological activity,
with particular interest in the inhibition of Aspergillus. In the work presented here, Design of Experiments, or DOE, was successfully combined with traditional approaches to significantly
improve sordarin yields in fermentation flasks. Overall, yields were increased 25-fold from <100 μg/g to as high as 2,609 μg/g
in flasks through the use of various medium and conduction changes supplemented with DOE. The improved process was then successfully
scaled to pilot plant tanks with the best batch producing 2,389 μg/g sordarin at the 250-l scale. 相似文献
237.
We develop a comprehensive biogeochemical framework for understanding and quantitatively evaluating metals bio-protection
in sulfidic microbial systems. We implement the biogeochemical framework in CCBATCH by expanding its chemical equilibrium
and biological sub-models for surface complexation and the formation of soluble and solid products, respectively. We apply
the expanded CCBATCH to understand the relative importance of the various key ligands of sulfidic systems in Zn detoxification.
Our biogeochemical analysis emphasizes the relative importance of sulfide over other microbial products in Zn detoxification,
because the sulfide yield is an order of magnitude higher than that of other microbial products, while its reactivity toward
metals also is highest. In particular, metal-titration simulations using the expanded CCBATCH in a batch mode illustrate how
sulfide detoxifies Zn, controlling its speciation as long as total sulfide is greater than added Zn. Only in the absence of
sulfide does complexation of Zn to biogenic organic ligands play a role in detoxification. Our biogeochemical analysis conveys
fundamental insight on the potential of the key ligands of sulfidic systems to effect Zn detoxification. Sulfide stands out
for its reactivity and prevalence in sulfidic systems. 相似文献
238.
Roland Schwarz Chunguang Liang Christoph Kaleta Mark Kühnel Eik Hoffmann Sergei Kuznetsov Michael Hecker Gareth Griffiths Stefan Schuster Thomas Dandekar 《BMC bioinformatics》2007,8(1):313
Background
Modeling of metabolic networks includes tasks such as network assembly, network overview, calculation of metabolic fluxes and testing the robustness of the network. 相似文献239.
240.
Adam P Schoof J Hartmann M Schwarz S Puppe B Ott M Rosenwald A Ott G Muller-Hermelink HK 《Cytogenetic and genome research》2007,118(2-4):328-336
Follicular lymphoma (FL) constitutes the neoplastic equivalent of germinal center B-cells. Like its physiological counterpart, FL grows in (atypical) follicular structures, the formation of which is as yet poorly understood. Recent data indicate that in early tumour stages, neoplastic FL cells home to and colonise reactive germinal centers. Laser microdissection (LMD) and micromanipulation techniques now allow for the molecular genetic analysis of single cell mutation patterns in FL. The purpose of the present study was the analysis of the sequence and order of somatic mutations in FL, i.e. the influence of the germinal center microenvironment on the clonal evolution in different grades of FL. By generating phylogenetic trees as calculated from tumour cell sequences, the clonal evolution from a putative progenitor cell was elucidated and finally, the tumour cell migration pattern in disease progression was assessed by analyzing biopsies at different time points in relapsed tumours. Four patients suffering from FL were included in the study. A primary FL grade 1 showed clustering of genetically related subclones in distinct follicles. A moderate interfollicular exchange of tumour cells was detected. Three cases of FL grade 2 were found to show decreased subclonal clustering in follicles and an increase in the interfollicular migration. Accumulations of replacement mutations in antigen binding domains (CDR) and silent mutations in non-antigen binding domains (FR), respectively, indicating antigen influence on hypermutation were only found in the case of FL grade 1. Our conclusion is that the microenvironment in germinal centers exercises influence on clonal evolution and tumour cell distribution patterns in FL. With increasing histologic grade during disease progression, a reduced intraclonal diversity and selection of subclones also occurs outside the setting of transformation to high-grade lymphoma. Antigen-dependent hypermutations were only seen in FL grade 1, while in progressed FL, random mutation patterns and a decrease of clonal diversity were found. 相似文献