全文获取类型
收费全文 | 3049篇 |
免费 | 253篇 |
出版年
2023年 | 10篇 |
2022年 | 6篇 |
2021年 | 44篇 |
2020年 | 33篇 |
2019年 | 46篇 |
2018年 | 52篇 |
2017年 | 37篇 |
2016年 | 67篇 |
2015年 | 139篇 |
2014年 | 174篇 |
2013年 | 176篇 |
2012年 | 245篇 |
2011年 | 230篇 |
2010年 | 122篇 |
2009年 | 122篇 |
2008年 | 178篇 |
2007年 | 187篇 |
2006年 | 160篇 |
2005年 | 160篇 |
2004年 | 173篇 |
2003年 | 160篇 |
2002年 | 149篇 |
2001年 | 43篇 |
2000年 | 27篇 |
1999年 | 39篇 |
1998年 | 51篇 |
1997年 | 47篇 |
1996年 | 35篇 |
1995年 | 34篇 |
1994年 | 25篇 |
1993年 | 34篇 |
1992年 | 22篇 |
1991年 | 21篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 19篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 8篇 |
排序方式: 共有3302条查询结果,搜索用时 46 毫秒
991.
Annette Schmidt Michael Scherer Horst Thiermann Dirk Steinritz 《Chemico-biological interactions》2013
The effect of sulfur mustard (SM) to the direct injured tissues of the skin, eyes and airways is well investigated. Little is known about the effect of SM to mesenchymal stem cells (MSC). However, this is an interesting aspect. Comparing the clinical picture of SM it is known today that MSC play an important role e.g. in chronic impaired wound healing. Therefore we wanted to get an understanding about how SM affects MSC and if these findings might become useful to get a better understanding of the effect of sulfur mustard gas with respect to skin wounds. 相似文献
992.
Lesca M. Holdt Annette von Delft Alexandros Nicolaou Sven Baumann Markus Kostrzewa Joachim Thiery Daniel Teupser 《Genetics》2013,193(2):601-608
A current challenge in the era of genome-wide studies is to determine the responsible genes and mechanisms underlying newly identified loci. Screening of the plasma proteome by high-throughput mass spectrometry (MALDI-TOF MS) is considered a promising approach for identification of metabolic and disease processes. Therefore, plasma proteome screening might be particularly useful for identifying responsible genes when combined with analysis of variation in the genome. Here, we describe a proteomic quantitative trait locus (pQTL) study of plasma proteome screens in an F2 intercross of 455 mice mapped with 177 genetic markers across the genome. A total of 69 of 176 peptides revealed significant LOD scores (≥5.35) demonstrating strong genetic regulation of distinct components of the plasma proteome. Analyses were confirmed by mechanistic studies and MALDI-TOF/TOF, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses of the two strongest pQTLs: A pQTL for mass-to-charge ratio (m/z) 3494 (LOD 24.9, D11Mit151) was identified as the N-terminal 35 amino acids of hemoglobin subunit A (Hba) and caused by genetic variation in Hba. Another pQTL for m/z 8713 (LOD 36.4; D1Mit111) was caused by variation in apolipoprotein A2 (Apoa2) and cosegregated with HDL cholesterol. Taken together, we show that genome-wide plasma proteome profiling in combination with genome-wide genetic screening aids in the identification of causal genetic variants affecting abundance of plasma proteins. 相似文献
993.
994.
Kathrin Helena Nowak Andreas Nehring Rüdiger Tiemann Annette Upmeier zu Belzen 《Journal of biological education》2013,47(3):182-188
The aim of the study was to describe, categorise and analyse students’ (aged 14–16) processes of scientific inquiry in biology and chemistry education. Therefore, a theoretical structure for scientific inquiry for both biology and chemistry, the VerE model, was developed. This model consists of nine epistemological acts, which combine processes of scientific thinking and inquiry methods. Based on the theoretical structure, a paper-and-pencil test was developed to investigate the students’ abilities in the acts of scientific inquiry. Each of the nine acts was operationalised to generate multiple-choice items. For each act, ten items were constructed. In total, ninety items per subject were tested in a field study to evaluate their psychometric quality. The article focuses on the outcomes for testing in biology. In biology, 537 students were tested with a paper-and-pencil test, following a multi-matrix design in which each student solved twenty-seven items. Data from 260 students have been analysed so far. Seventy-five items showed satisfactory item characteristics. The distribution of the items’ difficulties fits the students’ abilities appropriately. We conclude that theory-driven epistemological acts can be operationalised in tasks that assess students’ abilities in scientific inquiry. 相似文献
995.
György Barabás Rafael D’Andrea Rosalyn Rael Géza Meszéna Annette Ostling 《Oikos》2013,122(11):1565-1572
Emergent neutrality is the idea in community ecology that species interactions may drive a system in a direction where some species become so similar that this similarity will be the primary cause for their coexistence instead of niche differentiation. A recent, widely cited model of emergent neutrality is by Scheffer and van Nes, later applied to species abundance distribution patterns by Vergnon et al. We take issue with the ecological interpretation of this model, demonstrating that it in fact presupposes important differences between superficially similar‐looking species. We argue that the temptation to interpret the model as one of emergent neutrality stems from the fact that these differences are unmodeled and therefore hidden, obscuring the underlying coexistence mechanisms. We therefore claim that the model is actually one of hidden niches, and present several alternative ways to make its hidden portions more explicit. These alterations to the model also make its proper interpretation as one of hidden niches more transparent. We also polemize with the claim of Vergnon et al. that multimodality in species abundance distributions is support for their emergent neutrality model: we demonstrate that appropriate stochastic versions of classical resource partitioning or even neutral models can lead to such patterns in a robust way. Observation of these patterns is therefore inconclusive as to the underlying mechanisms that generate them. 相似文献
996.
Ibtissem Ben Fekih Sonia Boukhris-Bouhachem Mohamed Bechir Allagui Annette Bruun Jensen Jørgen Eilenberg 《法国昆虫学会纪事》2013,49(2):140-144
Summary. The natural occurrence of fungal pathogens of aphids and their ecological host range was investigated in Tunisia from 2009 to 2012. The survey focused on aphid infesting different crops and weeds and included 10 different aphid species. Samples were collected from eight agricultural crops sites belonging to three different bioclimatic zones. Four pathogens from the phylum Entomophthoromycota were found to occur naturally in Tunisian ecosystems: Pandora neoaphidis (Entomophthorales: Entomophthoraceae), Entomophthora planchoniana (Entomophthorales: Entomophthoraceae), Conidiobolus obscurus (Entomophthorales: Ancylistaceae) and Neozygites fresenii (Neozygitales: Neozygitaceae). The occurrence of entomophthoralean fungi depended on the sampling area, the bioclimatic zone, and aphid species. P. neoaphidis and E. planchoniana were the predominant pathogens infecting a wide range of aphid species whereas C. obscurus and N. fresenii were sporadically present on a limited number of aphid species. This study is the first survey on ecological host range of entomophthoralean fungi in Tunisia, and the first documentation of C. obscurus and N. fresenii to occur in Tunisia and Maghreb Region. 相似文献
997.
Bernd Ebner Stefan A. Lange Thomas Eckert Clementine Wischniowski Annette Ebner Rüdiger C. Braun-Dullaeus Christof Weinbrenner Carsten Wunderlich Gregor Simonis Ruth H. Strasser 《Molecular and cellular biochemistry》2013,373(1-2):115-123
Myocardial infarct size can be limited by pharmacological postconditioning (pPC) with cardioprotective agents. Cardioprotective effects of neuregulin-1β (NRG) via activation of protein kinase B (Akt) and downstream pathways like endothelial nitric oxide synthase (eNOS) have been postulated based on results from cell culture experiments. The purpose of this study was to investigate if eNOS may be involved in pPC with NRG. NRG application in an ex vivo mouse model (C57Bl6) of ischemia–reperfusion injury was analyzed. Unexpectedly, the infarct size increased when NRG was infused starting 5 min prior to reperfusion, even though protective Akt and GSK3β phosphorylation were enhanced. In eNOS deficient mice, however, NRG significantly reduced the infarct size. Co-infusion of NRG and l-arginine (Arg) lead to a reduction in infarct size in wild type animals. Electron paramagnetic resonance measurements revealed that NRG treatment prior to reperfusion leads to an enhanced release of reactive oxygen species compared to controls and this effect is blunted by co-infusion of Arg. This study documents the cardioprotective mechanisms of NRG signaling to be mediated by GSK3β inactivation. This is the first study to show that this protection fails in situations with dysfunctional eNOS. In eNOS deficient mice NRG exerts its protective effect via the GSK3β pathway, suggesting that the eNOS can limit cardioprotection. As dysfunctional eNOS has been described in cardiovascular risk factors like diabetes, hypertension, and hypercholesterolemia these findings can help to explain lack of postconditioning performance in models of cardiovascular co-morbidities. 相似文献
998.
Sebastian Reuther Martina Reiter Annette Raabe Ekkehard Dikomey 《Radiation and environmental biophysics》2013,52(4):463-469
The aim of this study was to determine the effects of ionizing radiation on gene expression by using for a first time a qPCR platform specifically established for the detection of 94 DNA repair genes but also to test the robustness of these results by using three analytical methods (global pattern recognition, ΔΔCq/Normfinder and ΔΔCq/Genorm). Study was focused on these genes because DNA repair is known primarily to determine the radiation response. Six strains of normal human fibroblasts were exposed to 2 Gy, and changes in gene expression were analyzed 24 h thereafter. A significant change in gene expression was found for only few genes, but the genes detected were mostly different for the three analytical methods used. For GPR, a significant change was found for four genes, in contrast to the eight or nine genes when applying ΔΔCq/Genorm or ΔΔCq/Normfinder, respectively. When using all three methods, a significant change in expression was only seen for GADD45A and PCNA. These data demonstrate that (1) the genes identified to show an altered expression upon irradiation strongly depend on the analytical method applied, and that (2) overall GADD45A and PCNA appear to play a central role in this response, while no significant change is induced for any of the other DNA repair genes tested. 相似文献
999.
1000.
Stella Tommasi Albert Zheng Annette Weninger Steven E. Bates Xuejun Arthur Li Xiwei Wu Monica Hollstein Ahmad Besaratinia 《Nucleic acids research》2013,41(1):182-195
Progression to malignancy requires that cells overcome senescence and switch to an immortal phenotype. Thus, exploring the genetic and epigenetic changes that occur during senescence/immortalization may help elucidate crucial events that lead to cell transformation. In the present study, we have globally profiled DNA methylation in relation to gene expression in primary, senescent and immortalized mouse embryonic fibroblasts. Using a high-resolution genome-wide mapping technique, followed by extensive locus-specific validation assays, we have identified 24 CpG islands that display significantly higher levels of CpG methylation in immortalized cell lines as compared to primary murine fibroblasts. Several of these hypermethylated CpG islands are associated with genes involved in the MEK–ERK pathway, one of the most frequently disrupted pathways in cancer. Approximately half of the hypermethylated targets are developmental regulators, and bind to the repressive Polycomb group (PcG) proteins, often in the context of bivalent chromatin in mouse embryonic stem cells. Because PcG-associated aberrant DNA methylation is a hallmark of several human malignancies, our methylation data suggest that epigenetic reprogramming of pluripotency genes may initiate cell immortalization. Consistent with methylome alterations, global gene expression analysis reveals that the vast majority of genes dysregulated during cell immortalization belongs to gene families that converge into the MEK–ERK pathway. Additionally, several dysregulated members of the MAP kinase network show concomitant hypermethylation of CpG islands. Unlocking alternative epigenetic routes for cell immortalization will be paramount for understanding crucial events leading to cell transformation. Unlike genetic alterations, epigenetic changes are reversible events, and as such, can be amenable to pharmacological interventions, which makes them appealing targets for cancer therapy when genetic approaches prove inadequate. 相似文献