全文获取类型
收费全文 | 18268篇 |
免费 | 1813篇 |
国内免费 | 2566篇 |
出版年
2024年 | 90篇 |
2023年 | 433篇 |
2022年 | 483篇 |
2021年 | 650篇 |
2020年 | 730篇 |
2019年 | 871篇 |
2018年 | 714篇 |
2017年 | 859篇 |
2016年 | 816篇 |
2015年 | 790篇 |
2014年 | 985篇 |
2013年 | 1448篇 |
2012年 | 794篇 |
2011年 | 998篇 |
2010年 | 828篇 |
2009年 | 1055篇 |
2008年 | 1153篇 |
2007年 | 1061篇 |
2006年 | 963篇 |
2005年 | 775篇 |
2004年 | 714篇 |
2003年 | 623篇 |
2002年 | 516篇 |
2001年 | 468篇 |
2000年 | 468篇 |
1999年 | 409篇 |
1998年 | 321篇 |
1997年 | 278篇 |
1996年 | 242篇 |
1995年 | 226篇 |
1994年 | 219篇 |
1993年 | 191篇 |
1992年 | 176篇 |
1991年 | 172篇 |
1990年 | 138篇 |
1989年 | 121篇 |
1988年 | 99篇 |
1987年 | 98篇 |
1986年 | 106篇 |
1985年 | 67篇 |
1984年 | 79篇 |
1983年 | 64篇 |
1982年 | 95篇 |
1981年 | 53篇 |
1980年 | 67篇 |
1979年 | 37篇 |
1978年 | 35篇 |
1977年 | 15篇 |
1976年 | 14篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Arnaud Di Franco Denis Baurain Gernot Glckner Michael Melkonian Herv Philippe 《Molecular biology and evolution》2022,39(1)
It is commonly assumed that increasing the number of characters has the potential to resolve evolutionary radiations. Here, we studied photosynthetic stramenopiles (Ochrophyta) using alignments of heterogeneous origin mitochondrion, plastid, and nucleus. Surprisingly while statistical support for the relationships between the six major Ochrophyta lineages increases when comparing the mitochondrion (6,762 sites) and plastid (21,692 sites) trees, it decreases in the nuclear (209,105 sites) tree. Statistical support is not simply related to the data set size but also to the quantity of phylogenetic signal available at each position and our ability to extract it. Here, we show that this ability for current phylogenetic methods is limited, because conflicting results were obtained when varying taxon sampling. Even though the use of a better fitting model improved signal extraction and reduced the observed conflicts, the plastid data set provided higher statistical support for the ochrophyte radiation than the larger nucleus data set. We propose that the higher support observed in the plastid tree is due to an acceleration of the evolutionary rate in one short deep internal branch, implying that more phylogenetic signal per position is available to resolve the Ochrophyta radiation in the plastid than in the nuclear data set. Our work therefore suggests that, in order to resolve radiations, beyond the obvious use of data sets with more positions, we need to continue developing models of sequence evolution that better extract the phylogenetic signal and design methods to search for genes/characters that contain more signal specifically for short internal branches. 相似文献
982.
With the development of mass spectrometry (MS)-based proteomics technologies, patient-derived xenograft (PDX), which is generated from the primary tumor of a patient, is widely used for the proteome-wide analysis of cancer mechanism and biomarker identification of a drug. However, the proteomics data interpretation is still challenging due to complex data deconvolution from the PDX sample that is a cross-species mixture of human cancerous tissues and immunodeficient mouse tissues. In this study, by using the lab-assembled mixture of human and mouse cells with different mixing ratios as a benchmark, we developed and evaluated a new method, SPA (shared peptide allocation), for protein quantitation by considering the unique and shared peptides of both species. The results showed that SPA could provide more convenient and accurate protein quantitation in human–mouse mixed samples. Further validation on a pair of gastric PDX samples (one bearing FGFR2 amplification while the other one not) showed that our new method not only significantly improved the overall protein identification, but also detected the differential phosphorylation of FGFR2 and its downstream mediators (such as RAS and ERK) exclusively. The tool pdxSPA is freely available at https://github.com/Li-Lab-Proteomics/pdxSPA. 相似文献
983.
984.
I. Walker 《International Review of Hydrobiology》1988,73(2):229-234
WANGERSKY and WANGERSKY'S (1980, 1981, 1983) Manna models on algal patchiness and competition are essentially stochastic models. Analysis of their phase-spatial properties, however, reveals complementary, deterministic features: interspecific competition is relatively ineffective because of the high degree of compartmentalization of resource supply and consumption; the probability of consumption in a given place at a given time is largely independent of the rate of consumption in other places. 相似文献
985.
目的:建立皮质酮诱导的PC12细胞梯度应激损伤模型,为细胞应激水平的评估和细胞应激损伤调控研究提供实验基础和对象。方法:通过检测不同浓度皮质酮(0~1 000μmol/L)在经过不同干预时间(8~48 h)后PC12细胞活力,观察皮质酮对细胞活力的影响,筛选最佳干预条件的细胞模型。分光光度法和微量法检测细胞模型的关键应激指标(MDA、SOD、NADH、LDH),对模型进行评价。结果:当皮质酮浓度在200μmol/L以下且干预时间为12 h时,细胞活力在半数失活率以下,可减少各组由于细胞活力下降而产生的混杂因素。与空白对照组比较,皮质酮浓度依赖性地升高模型组的MDA、NADH和LDH水平,降低SOD水平(P<0.01),符合梯度应激模型的构建要求。结论:成功建立了PC12细胞梯度应激损伤模型,在干预时间为12 h的情况下,干预浓度为0μmol/L、25μmol/L、50μmol/L、100μmol/L、150μmol/L、200μmol/L,使得细胞模型应激损伤程度梯度增加,可作为开展细胞应激损伤评估及调控实验的基础和对象。 相似文献
986.
Alberto Fernando Oliveira Justo Claudia Kimie Suemoto 《Journal of cell communication and signaling》2022,16(2):155
The accumulation and propagation of misfolded proteins in the brain is a pathological hallmark shared by many neurodegenerative diseases, such as the depositions of β-amyloid and hyperphosphorylated tau proteins in Alzheimer''s disease. Initial evidence shows the role of nitric oxide synthases in the development of neurodegenerative diseases. A recent, in an exciting paper (Bourgognon et al. in Proc Natl Acad Sci USA 118, 1–11, 2021. 10.1073/pnas.2009579118) it was shown that the inducible nitric oxide synthase plays an important role in promoting oxidative and nitrergic stress leading to neuroinflammation and consequently neuronal function impairments and decline in synaptic strength in mouse prion disease. In this context, we reviewed the possible mechanisms of nitric oxide synthase in the generation of neurodegenerative diseases. 相似文献
987.
988.
989.
990.
Jinhu Lin Xiang Lai Xiaoping Liu Hua Yan Changwu Wu 《Journal of cellular and molecular medicine》2022,26(5):1579
Recent studies have shown that pyroptosis, an inflammatory form of cell death, has a dual role in tumorigenesis and tumour progression and affects the prognosis of patients; however, the role of pyroptosis in glioblastoma (GBM) is still unclear. In this study, based on GBM patients'' data from two independent cohorts, we performed a comprehensive analysis of the expression and prognostic value of 33 pyroptosis‐associated genes (PAGs) in GBM, as well as their role in the tumour immune microenvironment (TIME) of GBM. We identified 29 PAGs that were differentially expressed between GBM and normal brain tissue, 18 of which were upregulated in GBM tissue. Most of the 33 PAGs were strongly correlated with the levels of immune cell infiltration. Based on the 33 PAGs, the GBM samples can be divided into two clusters (C1‐C2), with C1 having a ‘hot’ but immunosuppressive TIME and C2 having a ‘cold’ TIME, suggesting different immunotherapeutic responses in the two clusters. In addition, we identified four PAGs that were strongly associated with GBM prognosis and constructed a risk model based on these four PAGs. This risk model is an independent prognostic factor for GBM patients, and there is a different immune status between high‐ and low‐risk groups. In conclusion, this study demonstrates that pyroptosis is closely associated with the prognosis and TIME of GBM and provides an important basis for further studies on the relationship between pyroptosis and GBM. 相似文献