全文获取类型
收费全文 | 6825篇 |
免费 | 483篇 |
国内免费 | 1篇 |
出版年
2024年 | 6篇 |
2023年 | 40篇 |
2022年 | 115篇 |
2021年 | 181篇 |
2020年 | 138篇 |
2019年 | 163篇 |
2018年 | 209篇 |
2017年 | 160篇 |
2016年 | 281篇 |
2015年 | 449篇 |
2014年 | 437篇 |
2013年 | 571篇 |
2012年 | 650篇 |
2011年 | 623篇 |
2010年 | 340篇 |
2009年 | 310篇 |
2008年 | 389篇 |
2007年 | 369篇 |
2006年 | 333篇 |
2005年 | 301篇 |
2004年 | 257篇 |
2003年 | 211篇 |
2002年 | 234篇 |
2001年 | 41篇 |
2000年 | 28篇 |
1999年 | 40篇 |
1998年 | 53篇 |
1997年 | 28篇 |
1996年 | 34篇 |
1995年 | 23篇 |
1994年 | 28篇 |
1993年 | 22篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 5篇 |
1974年 | 6篇 |
1973年 | 14篇 |
排序方式: 共有7309条查询结果,搜索用时 15 毫秒
141.
Marta Mariotti Lippi 《Plant biosystems》2013,147(2):205-211
ABSTRACT Palynological investigations in the garden of the “Casa delle Nozze di Ercole ed Ebe“ in Pompeii revealed the presence of Vitis and Citrus. Citrus has often been said to be cultivated in Roman times, but no plant remains have ever confirmed this hypothesis as regards Pompeii. In this paper, we give evidence for an early cultivation of this plant in a garden. Analyses revealed that, as already observed in other gardens, the ground was covered by herbs which were the same as those found in ancient and contemporary meadows of the Vesuvian area. 相似文献
142.
Paul R. J. Ames Tommaso Bucci Mira Merashli Marta Amaral Alessia Arcaro Fabrizio Gentile 《Free radical research》2013,47(10):1063-1082
AbstractSystemic sclerosis (SSc) is a multisystem autoimmune disease: characterised from the clinical side by progressive vasculopathy and fibrosis of the skin and different organs and from the biochemical side by fibroblast deregulation with excessive production of collagen and increased expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). The latter contributes to an overproduction of reactive oxygen species that through an autocrine loop maintains NOX4 in a state of activation. Reactive oxygen and nitrogen species are implicated in the origin and perpetuation of several clinical manifestations of SSc having vascular damage in common; attempts to dampen oxidative and nitrative stress through different agents with antioxidant properties have not translated into a sustained clinical benefit. Objective of this narrative review is to describe the origin and clinical implications of oxidative and nitrative stress in SSc, with particular focus on the central role of NOX4 and its interactions, to re-evaluate the antioxidant approaches so far used to limit disease progression, to appraise the complexity of antioxidant treatment and to touch on novel pathways elements of which may represent specific treatment targets in the not so distant future. 相似文献
143.
Vanessa Pitozzi Stefania Pallotta Manuela Balzi Marta Bucciolini Aldo Becciolini Piero Dolara 《Free radical research》2013,47(11):1149-1154
We used X-rays from a linear accelerator and from a low energy therapeutic source to calibrate the single cell gel electrophoresis (comet assay), a widely used method to measure DNA damage. γ-Rays from 60Co, with known efficiency in inducing DNA breakage, were used as reference. Human lymphocytes and one murine tumour cell line, F10-M3 cells, were irradiated under different experimental conditions. A similar relationship between radiation dose and induced DNA damage was obtained with γ- and X-rays. A calibration curve was constructed to convert the comet assay raw data into break frequency. The median levels of DNA breaks and oxidative damage in circulating lymphocytes from healthy volunteers were calculated to be 0.76 and 0.80 breaks/109 Da, respectively, (0.50 and 0.52 breaks/106 bp). The values of oxidative DNA damage were in the same order of magnitude as those found by others with HPLC methods. 相似文献
144.
Nikos Papakonstantinou Stavroula Ntoufa Elisavet Chartomatsidou Giorgio Papadopoulos Artemis Hatzigeorgiou Achiles Anagnostopoulos Katerina Chlichlia Paolo Ghia Marta Muzio Chrysoula Belessi Kostas Stamatopoulos 《Molecular medicine (Cambridge, Mass.)》2013,19(1):115-123
Critical processes of B-cell physiology, including immune signaling through the B-cell receptor (BcR) and/or Toll-like receptors (TLRs), are targeted by microRNAs. With this in mind and also given the important role of BcR and TLR signaling and microRNAs in chronic lymphocytic leukemia (CLL), we investigated whether microRNAs could be implicated in shaping the behavior of CLL clones with distinct BcR and TLR molecular and functional profiles. To this end, we examined 79 CLL cases for the expression of 33 microRNAs, selected on the following criteria: (a) deregulated in CLL versus normal B-cells; (b) differentially expressed in CLL subgroups with distinct clinicobiological features; and, (c) if meeting (a) + (b), having predicted targets in the immune signaling pathways. Significant upregulation of miR-150, miR-29c, miR-143 and miR-223 and downregulation of miR-15a was found in mutated versus unmutated CLL, with miR-15a showing the highest fold difference. Comparison of two major subsets with distinct stereotyped BcRs and signaling signatures, namely subset 1 [IGHV1/5/7-IGKV1(D)-39, unmutated, bad prognosis] versus subset 4 [IGHV4-34/IGKV2-30, mutated, good prognosis] revealed differences in the expression of miR-150, miR-29b, miR-29c and miR-101, all down-regulated in subset 1. We were also able to link these distinct microRNA profiles with cellular phenotypes, importantly showing that, in subset 1, miR-101 downregulation is associated with overexpression of the enhancer of zeste homolog 2 (EZH2) protein, which has been associated with clinical aggressiveness in other B-cell lymphomas. In conclusion, specific miRNAs differentially expressed among CLL subgroups with distinct BcR and/or TLR signaling may modulate the biological and clinical behavior of the CLL clones. 相似文献
145.
Marta Cal Mariusz Jaremko Łukasz Jaremko Piotr Stefanowicz 《Journal of peptide science》2013,19(1):9-15
A novel resin designed for solid‐phase synthesis of peptide hydroxamic acids (PHA) combining the trityl linker with poly(ethylene glycol)‐based support, ChemMatrix® type, is described. The synthesis of PHA can be performed according to a standard protocol, providing products in excellent purity and reasonable yields. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
146.
Karolina Pulka Marta Slupska Anna Puszko Maria Misiak Marcin Wilczek Wiktor Kozminski Aleksandra Misicka 《Journal of peptide science》2013,19(7):433-440
The Pictet–Spengler (PS) reaction was performed with various types of substrates: H‐Trp‐OMe and dipeptides with N‐terminal Trp as arylethylamine components and Z‐protected amino aldehydes and peptidoaldehydes as carbonyl components. We found that the C‐terminal part of Trp derivatives did not have any influence on the stereoselectivity of the reaction and the results are the same for simple esters of Trp and dipeptides. On the contrary, the selectivity of the PS reaction with peptidoaldehydes with L configuration of the C‐terminus residue is totally different from that obtained with simple L‐amino aldehydes. It allows us to obtain cis stereoisomers, which cannot be isolated from the reaction with amino aldehydes. But the utility of the peptidoaldehydes as substrates for the PS reaction is reduced by the side formation of enamides which decrease the yield of cyclization. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
147.
148.
149.
Josep Peñuelas Jordi Sardans Marc Estiarte Romà Ogaya Jofre Carnicer Marta Coll Adria Barbeta Albert Rivas‐Ubach Joan Llusià Martin Garbulsky Iolanda Filella Alistair S. Jump 《Global Change Biology》2013,19(8):2303-2338
We review the evidence of how organisms and populations are currently responding to climate change through phenotypic plasticity, genotypic evolution, changes in distribution and, in some cases, local extinction. Organisms alter their gene expression and metabolism to increase the concentrations of several antistress compounds and to change their physiology, phenology, growth and reproduction in response to climate change. Rapid adaptation and microevolution occur at the population level. Together with these phenotypic and genotypic adaptations, the movement of organisms and the turnover of populations can lead to migration toward habitats with better conditions unless hindered by barriers. Both migration and local extinction of populations have occurred. However, many unknowns for all these processes remain. The roles of phenotypic plasticity and genotypic evolution and their possible trade‐offs and links with population structure warrant further research. The application of omic techniques to ecological studies will greatly favor this research. It remains poorly understood how climate change will result in asymmetrical responses of species and how it will interact with other increasing global impacts, such as N eutrophication, changes in environmental N : P ratios and species invasion, among many others. The biogeochemical and biophysical feedbacks on climate of all these changes in vegetation are also poorly understood. We here review the evidence of responses to climate change and discuss the perspectives for increasing our knowledge of the interactions between climate change and life. 相似文献
150.
María De La Fuente Ana M. González Antonio M. De Ron Marta Santalla 《Molecular breeding : new strategies in plant improvement》2013,31(3):501-516
Most studies on the genetic diversity of common bean (Phaseolus vulgaris L.) have focussed on accessions from the Mesoamerican gene pool compared to the Andean gene pool. A deeper knowledge of the genetic structure of Argentinian germplasm would enable researchers to determine how the Andean domestication event affected patterns of genetic diversity in domesticated beans and to identify candidates for genes targeted by selection during the evolution of the cultivated common bean. A collection of 116 wild and domesticated accessions representing the diversity of the Andean bean in Argentina was genotyped by means of 114 simple sequence repeat (SSR) markers. Forty-seven Mesoamerican bean accessions and 16 Andean bean accessions representing the diversity of Andean landraces and wild accessions were also included. Using the Bayesian algorithm implemented in the software STRUCTURE we identified five major groups that correspond to Mesoamerican and Argentinian wild accessions and landraces and a group that corresponds to accessions from different Andean and Mesoamerican countries. The neighbour-joining algorithm and principal coordinate clustering analysis confirmed the genetic relationships among accessions observed with the STRUCTURE analysis. Argentinian accessions showed a substantial genetic variation with a considerable number of unique haplotypes and private alleles, suggesting that they may have played an important role in the evolution of the species. The results of statistical analyses aimed at identifying genomic regions with consistent patterns of variation were significant for 35 loci (~20 % of the SSRs used in the Argentinian accessions). One of these loci mapped in or near the genomic region of the glutamate decarboxylase gene. Our data characterize the population structure of the Argentinian germplasm. This information on its diversity will be very valuable for use in introgressing Argentinian genes into commercial varieties because the majority of present-day common bean varieties are of Andean origin. 相似文献