全文获取类型
收费全文 | 7973篇 |
免费 | 848篇 |
国内免费 | 3篇 |
专业分类
8824篇 |
出版年
2023年 | 50篇 |
2022年 | 80篇 |
2021年 | 148篇 |
2020年 | 136篇 |
2019年 | 182篇 |
2018年 | 183篇 |
2017年 | 205篇 |
2016年 | 316篇 |
2015年 | 468篇 |
2014年 | 468篇 |
2013年 | 571篇 |
2012年 | 620篇 |
2011年 | 563篇 |
2010年 | 456篇 |
2009年 | 377篇 |
2008年 | 446篇 |
2007年 | 409篇 |
2006年 | 354篇 |
2005年 | 390篇 |
2004年 | 368篇 |
2003年 | 355篇 |
2002年 | 320篇 |
2001年 | 69篇 |
2000年 | 48篇 |
1999年 | 82篇 |
1998年 | 72篇 |
1997年 | 62篇 |
1996年 | 66篇 |
1995年 | 54篇 |
1994年 | 47篇 |
1993年 | 49篇 |
1992年 | 51篇 |
1991年 | 35篇 |
1990年 | 44篇 |
1989年 | 42篇 |
1988年 | 36篇 |
1987年 | 34篇 |
1986年 | 38篇 |
1985年 | 21篇 |
1984年 | 41篇 |
1983年 | 30篇 |
1982年 | 41篇 |
1981年 | 30篇 |
1980年 | 35篇 |
1979年 | 27篇 |
1978年 | 26篇 |
1977年 | 21篇 |
1976年 | 25篇 |
1975年 | 26篇 |
1971年 | 18篇 |
排序方式: 共有8824条查询结果,搜索用时 93 毫秒
71.
This paper deals with the botanical study of a family funerary enclosure located in the Porta Nocera necropolis in Pompeii
(southwestern Italy). This study is part of a Franco-Italian programme investigating Roman funerary rituals. The choice of
the context was due to the exceptional preservation of the archaeological features, which offered the opportunity to observe
the remains of the proceedings which took place in a funerary enclosure in great detail. An adequate methodology had to be
developed and a 3D recording of every single artefact or ecofact has been made. Both ground surfaces and graves provided botanical
results. Those from the ground surfaces consisted mainly of fruit offering residues (especially fig and grape), while a much
wider range of species was observed in the tombs, including cereals, pulses, other kinds of fruits, weeds and bread/pastry.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
72.
Demougeot C Méthy D Prigent-Tessier A Garnier P Bertrand N Guilland JC Beley A Marie C 《Free radical research》2003,37(1):59-67
For a better understanding of the role of iron imbalance in neuropathology, a liposoluble iron complex (ferric hydroxyquinoline, FHQ) was injected into striatum of rats. The effects of two modalities of iron injections on brain damage, hydroxyl radical ( •OH) production (assessed by the salicylate method coupled to microdialysis) and tissue reactive iron level (evaluated ex vivo by the propensity of the injected structure for lipid peroxidation) were examined. Rapid injection of FHQ (10 nmoles of 5 mM FHQ pH 3 solution over 1-min period) but not that of corresponding vehicle led to extensive damage associated with increased tissue free iron level in the injected region. Conversely, neither lesion nor free iron accumulation was observed after slow FHQ injection (10 nmoles of a 100 μM FHQ pH 7 solution over 1-h period) as compared to corresponding vehicle injection. Production of •OH was induced by slow FHQ injection but not by rapid FHQ injection, probably as a result of in vivo abolition of iron-induced •OH formation by acid pH. Indeed, rapid injection of FAC pH 7 (ferric ammonium citrate, 5 mM in saline) was associated with •OH formation whereas rapid injection of FAC pH 3 did not. Our results identify the rate of iron delivery to cells as an important determinant of iron toxicity and do not support a major role for extracellular •OH in damage associated with intracerebral iron injection. 相似文献
73.
Saïd Azza Christian Cambillau Didier Raoult Marie Suzan-Monti 《BMC molecular biology》2009,10(1):39-8
Background
Acanthamoebae polyphaga Mimivirus (APM) is the largest known dsDNA virus. The viral particle has a nearly icosahedral structure with an internal capsid shell surrounded with a dense layer of fibrils. A Capsid protein sequence, D13L, was deduced from the APM L425 coding gene and was shown to be the most abundant protein found within the viral particle. However this protein remained poorly characterised until now. A revised protein sequence deposited in a database suggested an additional N-terminal stretch of 142 amino acids missing from the original deduced sequence. This result led us to investigate the L425 gene structure and the biochemical properties of the complete APM major Capsid protein. 相似文献74.
Bea Vuylsteke Gis��le Semd�� Lazare Sika Tania Crucitti Virginie Etti��gne Traor�� Anne Buv�� Marie Laga 《PloS one》2012,7(3)
Objective
To assess condom use and prevalence of STIs and HIV among female sex workers (FSWs), as part of a comprehensive monitoring and evaluation plan of a nationwide sex worker prevention project in Côte d''Ivoire.Design and Methods
Cross sectional surveys were conducted among FSWs attending five project clinics in Abidjan and San Pedro (2007), and in Yamoussoukro and Gagnoa (2009). A standardized questionnaire was administered in a face-to-face interview, which included questions on socio-demographic characteristics, sexual behaviour and condom use. After the interview, the participants were asked to provide samples for STI and HIV testing.Results
A total of 1110 FSWs participated in the surveys. There were large differences in socio-demographic and behavioural characteristics between FSW coming for the first time as compared to FSW coming on a routine visit. The prevalence of N. gonorrhoeae or C.trachomatis was 9.1%, 11.8% among first vs. 6.9% routine attendees (p = 0.004). The overall HIV prevalence was 26.6%, it was lower among first time attendees (17.5% as compared to 33.9% for routine attendees, p<0.001). The HIV prevalence among first attendees was also lower than the proportion of HIV positive tests from routine testing and counselling services in the same clinics.Conclusions
The results show a relatively high STI and HIV prevalence among FSWs in different cities in Côte d''Ivoire. In the light of these results, prevention efforts should continue to focus on FSWs in the country. 相似文献75.
Motivation
Biologists often wish to use their knowledge on a few experimental models of a given molecular system to identify homologs in genomic data. We developed a generic tool for this purpose.Results
Macromolecular System Finder (MacSyFinder) provides a flexible framework to model the properties of molecular systems (cellular machinery or pathway) including their components, evolutionary associations with other systems and genetic architecture. Modelled features also include functional analogs, and the multiple uses of a same component by different systems. Models are used to search for molecular systems in complete genomes or in unstructured data like metagenomes. The components of the systems are searched by sequence similarity using Hidden Markov model (HMM) protein profiles. The assignment of hits to a given system is decided based on compliance with the content and organization of the system model. A graphical interface, MacSyView, facilitates the analysis of the results by showing overviews of component content and genomic context. To exemplify the use of MacSyFinder we built models to detect and class CRISPR-Cas systems following a previously established classification. We show that MacSyFinder allows to easily define an accurate “Cas-finder” using publicly available protein profiles.Availability and Implementation
MacSyFinder is a standalone application implemented in Python. It requires Python 2.7, Hmmer and makeblastdb (version 2.2.28 or higher). It is freely available with its source code under a GPLv3 license at https://github.com/gem-pasteur/macsyfinder. It is compatible with all platforms supporting Python and Hmmer/makeblastdb. The “Cas-finder” (models and HMM profiles) is distributed as a compressed tarball archive as Supporting Information. 相似文献76.
Ryan J.H. West Yubing Lu Bruno Marie Fen-Biao Gao Sean T. Sweeney 《The Journal of cell biology》2015,208(7):931-947
Mutations in genes essential for protein homeostasis have been identified in frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) patients. Why mature neurons should be particularly sensitive to such perturbations is unclear. We identified mutations in Rab8 in a genetic screen for enhancement of an FTD phenotype associated with ESCRT-III dysfunction. Examination of Rab8 mutants or motor neurons expressing a mutant ESCRT-III subunit, CHMP2BIntron5, at the Drosophila melanogaster neuromuscular junction synapse revealed synaptic overgrowth and endosomal dysfunction. Expression of Rab8 rescued overgrowth phenotypes generated by CHMP2BIntron5. In Rab8 mutant synapses, c-Jun N-terminal kinase (JNK)/activator protein-1 and TGF-β signaling were overactivated and acted synergistically to potentiate synaptic growth. We identify novel roles for endosomal JNK-scaffold POSH (Plenty-of-SH3s) and a JNK kinase kinase, TAK1, in regulating growth activation in Rab8 mutants. Our data uncover Rab8, POSH, and TAK1 as regulators of synaptic growth responses and point to recycling endosome as a key compartment for synaptic growth regulation during neurodegenerative processes. 相似文献
77.
78.
Catherine Marie Breton Daniela Farinelli Sarfraz Shafiq John Seymour Heslop-Harrison Margaret Sedgley André Jean Bervillé 《Tree Genetics & Genomes》2014,10(4):1055-1067
The self-incompatibility type is of key importance to understanding pollination in orchards, because most olive cultivars are partially self-incompatible and thus require pollinizers to ensure fruit set. The gametophytic model has been advocated to function in the olive, but no allele pair has been attributed to any variety. The GSI model failed in most combinations to explain fruit set. Olive growers must screen experimentally and empirically to look for inter-compatible pair-wise combinations of varieties for optimum pollination. The sporophytic model, with given dominance relationships for six S-alleles matches 98 % of the experimental data of the two sets investigated. We propose a method to analyze data from controlled crosses between olive cultivars applied to two experiments for varieties crossed in a diallel design. Furthermore, the dominance between the S-allele pair allows rational prediction of olive variety self-incompatibility levels. The S-allele pairs were unraveled for more than 60 cultivars. To go further, crosses between reference varieties—those in which the S-allele pair was unraveled—and varieties under experimentation (VarE) with an unknown S-allele pair will enable an increase in knowledge and the choice of the best pollinizers in silico. Nevertheless, we pose outstanding questions in orchards where open-pollination efficiency with varieties harboring the R2R3, R1R3, R1R5, or R3R5 pairs. These S-allele pairs require pollen grains without R2 or R3 , R1 or R3, and R3 or R5 determinants. Such pollinizer varieties are not abundant in France and Italy, and this questions whether their spread is sufficient for optimal pollination of main varieties. 相似文献
79.
Maiko Mori Marie Smedberg Maria Klaude Inga Tj?der ?ke Norberg Olav Rooyackers Jan Wernerman 《PloS one》2014,9(5)
Glutamine transport between tissues is important for the outcome of critically ill patients. Investigation of glutamine kinetics is, therefore, necessary to understand glutamine metabolism in these patients in order to improve future intervention studies. Endogenous glutamine production can be measured by continuous infusion of a glutamine tracer, which necessitates a minimum measurement time period. In order to reduce this problem, we used and validated a tracer bolus injection method. Furthermore, this method was used to measure the glutamine production in healthy volunteers in the post-absorptive state, with extra alanine and with glutamine supplementation and parenteral nutrition. Healthy volunteers received a bolus injection of [1-13C] glutamine, and blood was collected from the radial artery to measure tracer enrichment over 90 minutes. Endogenous rate of appearance (endoRa) of glutamine was calculated from the enrichment decay curve and corrected for the extra glutamine supplementation. The glutamine endoRa of healthy volunteers was 6.1±0.9 µmol/kg/min in the post-absorptive state, 6.9±1.0 µmol/kg/min with extra alanyl-glutamine (p = 0.29 versus control), 6.1±0.4 µmol/kg/min with extra alanine only (p = 0.32 versus control), and 7.5±0.9 µmol/kg/min with extra alanyl-glutamine and parenteral nutrition (p = 0.049 versus control). In conclusion, a tracer bolus injection method to measure glutamine endoRa showed good reproducibility and small variation at baseline as well as during parenteral nutrition. Additionally, we showed that parenteral nutrition including alanyl-glutamine increased glutamine endoRa in healthy volunteers, which was not attributable to the alanine part of the dipeptide. 相似文献
80.
Preparation and Enantioselectivity Binding Studies of a New Chiral Cobalt(II)porphyrin‐Tröger's Base Conjugate 下载免费PDF全文
Ameneh Tatar Martin Valík Jana Novotná Martin Havlík Bohumil Dolenský Vladimír Král Marie Urbanová 《Chirality》2014,26(8):361-367
A new bis[cobalt(II)porphyrin]‐Tröger's base conjugate was studied as a potential receptor for methyl esters of several amino acids. The conjugate was prepared as racemate, and then resolved via preparative high‐performance liquid chromatography (HPLC) on a chiral column. The high affinity to lysine, histidine, and proline methyl esters was found by complexation studies followed by UV‐Vis spectroscopy. The studies of pure enantiomers, followed by UV‐Vis and electronic circular dichroism spectroscopy, revealed the highest enantioselectivity for lysine methyl ester. Chirality 26:361–367, 2014. © 2014 Wiley Periodicals, Inc. 相似文献