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991.
992.
The replicative lifespan of normal somatic cells is restricted by the erosion of telomeres, which are protective caps at the
ends of linear chromosomes. The loss of telomeres induces antiproliferative signals that eventually lead to cellular senescence.
The enzyme complex telomerase can maintain telomeres, but its expression is confined to highly proliferative cells such as
stem cells and tumor cells. The immense regenerative capacity of the hematopoietic system is provided by a distinct type of
adult stem cell: hematopoietic stem cells (HSCs). Although blood cells have to be produced continuously throughout life, the
HSC pool seems not to be spared by aging processes. Indeed, limited expression of telomerase is not sufficient to prevent
telomere shortening in these cells, which is thought ultimately to limit their proliferative capacity. In this review, we
discuss the relevance of telomere maintenance for the hematopoietic stem cell compartment and consider potential functions
of telomerase in this context. We also present possible clinical applications of telomere manipulation in HSCs and new insights
affecting the aging of the hematopoietic stem cell pool and replicative exhaustion.
This work was supported by European Community Grant LSHC-CT-2004-502943 (MOL CANCER MED). 相似文献
993.
Panyu Yang Yanyan Yang Pin Sun Yu Tian Fang Gao Chen Wang Tingyu Zong Min Li Ying Zhang Tao Yu Zhirong Jiang 《International journal of biological sciences》2021,17(1):32
βII spectrin, the most common isoform of non-erythrocyte spectrin, is a cytoskeleton protein present in all nucleated cells. Interestingly, βII spectrin is essential for the development of various organs such as nerve, epithelium, inner ear, liver and heart. The functions of βII spectrin include not only establishing and maintaining the cell structure but also regulating a variety of cellular functions, such as cell apoptosis, cell adhesion, cell spreading and cell cycle regulation. Notably, βII spectrin dysfunction is associated with embryonic lethality and the DNA damage response. More recently, the detection of altered βII spectrin expression in tumors indicated that βII spectrin might be involved in the development and progression of cancer. Its mutations and disorders could result in developmental disabilities and various diseases. The versatile roles of βII spectrin in disease have been examined in an increasing number of studies; nonetheless, the exact mechanisms of βII spectrin are still poorly understood. Thus, we summarize the structural features and biological roles of βII spectrin and discuss its molecular mechanisms and functions in development, homeostasis, regeneration and differentiation. This review highlight the potential effects of βII spectrin dysfunction in cancer and other diseases, outstanding questions for the future investigation of therapeutic targets. The investigation of the regulatory mechanism of βII spectrin signal inactivation and recovery may bring hope for future therapy of related diseases. 相似文献
994.
从云南轮马热泉下游淤泥中筛选得到了一株产耐热普鲁兰酶菌株LM14-2.根据形态特征及16S rRNA序列同源性分析,初步判定为Anoxybacillus sp.LM14-2.该菌株发酵上清液中有耐热普鲁兰酶积累,其反应最适pH值为6.0,最适温度为70℃.利用染色体步移技术获得了完整的普鲁兰酶编码基因(HQ660582),经序列相似性进一步分析,确定该蛋白与Ⅰ型普鲁兰酶保守区b相吻合.通常的普鲁兰酶在高温下很快失活,难以满足淀粉加工,洗涤剂等相关工业的需求,而该新型的耐热普鲁兰醇的作用温度广泛,热稳定性较好,65℃保温55 h后达到其半衰期,具有广阔的开发应用前景. 相似文献
995.
Mingzhang Guo Qi Bao Siyuan Chen Xingtian Cui Wentao Xu Xiaoyun He Yunbo Luo Xiaozhe Qi Kunlun Huang 《World journal of microbiology & biotechnology》2016,32(3):43
Rabbit neutrophils peptide-1 (NP-1) is a type of defensin that possesses a broad spectrum of antimicrobial activity. Chlorella ellipsoidea is a new eukaryotic expression system for exogenously producing NP-1. The NP-1 transgenic C. ellipsoidea can be directly added into feed as antimicrobial agent without any purification procedure for the NP-1 peptide. However, the effects of C. ellipsoidea and NP-1 on the host gut microbiota should be explored before application. In this study, diets containing different concentrations (1.25, 2.5, and 5 %) of C. ellipsoidea and NP-1 transgenic C. ellipsoidea were administered to male Sprague–Dawley rats. Compared with the chow diet control group, none of the experimental groups showed any significant differences in their growth indices, and no histopathological damage was observed. The phylotypes of gut microbiota in the control group, the 5 % C. ellipsoidea diet group and the 5 % NP-1 transgenic C. ellipsoidea diet group were determined by 16S rRNA sequencing. The results showed that both 5 % experimental groups had shifted community memberships of gut microbiota. In particular, the 5 % NP-1 transgenic C. ellipsoidea diet exhibited an increased abundance of most Gram-positive bacterial taxa and a reduced abundance of most Gram-negative bacterial taxa, and it promoted the growth of some lactic acid bacterial genera. Lactic acid bacteria, especially the Bifidobacterium and Lactobacillus, have been widely reported to be benefic effects on the host. Thus NP-1 transgenic C. ellipsoidea is promising feed additive and gut regulator, as it have the potential to increase the abundance of Bifidobacterium and Lactobacillus in gut microbiota of animal. 相似文献
996.
Duo Shan Jiangping Sun Anna Yakusik Zhongdan Chen Jianhua Yuan Tao Li Jeannia Fu Kaveh Khoshnood Xing Yang Mei Wei Song Duan Marc Bulterys Michael Sante Runhua Ye Lifen Xiang Yuecheng Yang 《PloS one》2013,8(6)
Objective
We assessed HIV/AIDS expenditures in Dehong Prefecture, Yunnan Province, one of the highest prevalence regions in China, and describe funding sources and spending for different categories of HIV-related interventions and at-risk populations.Methods
2010 HIV/AIDS expenditures in Dehong Prefecture were evaluated based on UNAIDS’ National AIDS Spending Assessment methodology.Results
Nearly 93% of total expenditures for HIV/AIDS was contributed by public sources. Of total expenditures, 52.7% was allocated to treatment and care, 24.5% to program management and administration and 19.8% to prevention. Spending on treatment and care was primarily allocated to the treatment of opportunistic infections. Most (40.4%) prevention spending was concentrated on most-at-risk populations, injection drug users (IDUs), sex workers, and men who have sex with men (MSM), with 5.5% allocated to voluntary counseling and testing. Prevention funding allocated for MSM, partners of people living with HIV and prisoners and other confined populations was low compared to the disproportionate burden of HIV/AIDS in these populations. Overall, people living with HIV accounted for 57.57% of total expenditures, while most-at-risk populations accounted for only 7.99%.Conclusions
Our study demonstrated the applicability of NASA for tracking and assessing HIV expenditure in the context of China, it proved to be a useful tool in understanding national HIV/AIDS response from financial aspect, and to assess the extent to which HIV expenditure matches epidemic patterns. Limited funding for primary prevention and prevention for MSM, prisoners and partners of people living with HIV, signal that resource allocation to these key areas must be strengthened. Comprehensive analyses of regional and national funding strategies are needed to inform more equitable, effective and cost-effective HIV/AIDS resource allocation. 相似文献997.
Plant communities around natural CO2 springs have been exposed to elevated CO2 levels over many generations and give us a unique opportunity to investigate the effects of long-term elevated CO2 levels on wild plants. We searched for natural CO2 springs in cool temperate climate regions in Japan and found three springs that were suitable for studying long-term responses
of plants to elevated levels of CO2: Ryuzin-numa, Yuno-kawa and Nyuu. At these CO2 springs, the surrounding air was at high CO2 concentration with no toxic gas emissions throughout the growth season, and there was natural vegetation around the springs.
At each site, high-CO2 (HC) and low-CO2 (LC) plots were established, and three dominant species at the shrub layers were used for physiological analyses. Although
the microenvironments were different among the springs, dicotyledonous species growing at the HC plots tended to have more
starch and less nitrogen per unit dry mass in the leaves than those growing at the LC plots. In contrast, monocotyledonous
species growing in the HC and LC plots had similar starch and nitrogen concentrations. Photosynthetic rates at the mean growth
CO2 concentration were higher in HC plants than LC plants, but photosynthetic rates at a common CO2 concentration were lower in HC plants. Efficiency of water and nitrogen use of leaves at growth CO2 concentration was greatly increased in HC plants. These results suggest that natural plants growing in elevated CO2 levels under cool temperate climate conditions have down-regulated their photosynthetic capacity but that they increased
photosynthetic rates and resource use efficiencies due to the direct effect of elevated CO2 concentration. 相似文献
998.
Background
Three types of cell lines have been established from mouse blastocysts: embryonic stem (ES) cells, trophoblast stem (TS) cells, and extra-embryonic endoderm (XEN) cells, which have the potential to differentiate into their respective cognate lineages. ES cells can differentiate in vitro not only into somatic cell lineages but into extra-embryonic lineages, including trophectoderm and extra-embryonic endoderm (ExEn) as well. TS cells can be established from ES cells by the artificial repression of Oct3/4 or the upregulation of Cdx2 in the presence of FGF4 on feeder cells. The relationship between these embryo-derived XEN cells and ES cell-derived ExEn cell lines remains unclear, although we have previously reported that overexpression of Gata4 or Gata6 induces differentiation of mouse ES cells into extra-embryonic endoderm in vitro. 相似文献999.
Andrew C. Huang John E. Elliott Kimberly M. Cheng Kermit Ritland Carol E. Ritland Sarah K. Thomsen Sofi Hindmarch Kathy Martin 《Conservation Genetics》2016,17(2):357-367
The barn owl (Tyto alba) is a non-migratory species widely distributed across much of North America in areas with extensive old-field and grassland habitat and without extensive winter snow cover. We investigated the genetic diversity and phylogeographic patterns of barn owl populations in western North America, ranging from British Columbia (BC) to southern California, and one eastern population from Pennsylvania. We also determined the genetic distinctiveness of a population off the coast of southern California, Santa Barbara Island, as management plans to control the local owl population are being considered to decrease predation rate on the now threatened Scripps’s Murrelet (Synthliboramphus scrippsi). Using 8 polymorphic microsatellite markers (N = 126) and ND2 mitochondrial sequences (N = 37), we found little to no genetic structure among all sampled regions, with the exception of Santa Barbara Island. The BC mainland population, despite its northwestern geographically peripheral location and ongoing habitat degradation, is not genetically depauperate. However, individuals from Vancouver Island, likewise a peripheral population in BC, exhibited the lowest genetic diversity of all sampled locations. The low global FST value (0.028) estimated from our study suggests that old-field agricultural habitats are well connected in North America. Since the BC population has declined by about 50 % within the last three decades, it is vital to focus on preserving the remaining barn owl habitats in BC to allow successful establishment from neighbouring populations. Additionally, our microsatellite data revealed that the population on Santa Barbara Island showed genetic divergence from its continental counterpart. Mitochondrial data, however, demonstrated that this island population is not a monophyletic lineage containing unique haplotypes, and hence cannot be designated as an Evolutionarily Significant Unit. 相似文献
1000.