全文获取类型
收费全文 | 16281篇 |
免费 | 1423篇 |
国内免费 | 1423篇 |
专业分类
19127篇 |
出版年
2024年 | 53篇 |
2023年 | 252篇 |
2022年 | 498篇 |
2021年 | 810篇 |
2020年 | 671篇 |
2019年 | 748篇 |
2018年 | 730篇 |
2017年 | 529篇 |
2016年 | 711篇 |
2015年 | 1063篇 |
2014年 | 1270篇 |
2013年 | 1300篇 |
2012年 | 1501篇 |
2011年 | 1342篇 |
2010年 | 920篇 |
2009年 | 748篇 |
2008年 | 802篇 |
2007年 | 722篇 |
2006年 | 704篇 |
2005年 | 573篇 |
2004年 | 495篇 |
2003年 | 522篇 |
2002年 | 412篇 |
2001年 | 245篇 |
2000年 | 221篇 |
1999年 | 212篇 |
1998年 | 142篇 |
1997年 | 118篇 |
1996年 | 119篇 |
1995年 | 116篇 |
1994年 | 99篇 |
1993年 | 61篇 |
1992年 | 80篇 |
1991年 | 67篇 |
1990年 | 62篇 |
1989年 | 44篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 36篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1970年 | 1篇 |
1962年 | 2篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 97 毫秒
1.
2.
Xue-Yuan Dong Yun-Yan Li Xiao-Ang Yang Wei-Feng Chen 《Biochimie et biologie cellulaire》2004,82(5):577-582
In an effort to identify novel Cancer-Testis genes, we analyzed the sequence in the q26-28 region of human X chromosome by several on-line tools. The candidate sequences were then confirmed by experiments. We have obtained a novel Cancer-Testis gene, BJ-HCC-20. In vivo, it was found to have two isoforms. In samples of liver, colon, gastric and lung cancer tested, the expression frequency of BJ-HCC-20 is 25%, 17%, 21% and 15%, respectively. Full-length cDNAs of both BJ-HCC-20 isoforms were isolated and their gene structures and promoter regions were characterized. BJ-HCC-20 might have implications in theoretical and practical tumor biology. 相似文献
3.
Cheng Jianxin Xia Yuqing Zhou Cheng Li Xiaohao Liu Pengfei 《Marine biotechnology (New York, N.Y.)》2023,25(2):291-313
Marine Biotechnology - Takifugu rubripes is important commercially fish species in China and it is under serious threat from white spot disease (cyptocaryoniasis), which leads to heavy economic... 相似文献
4.
5.
Shin DH 《Protein and peptide letters》2008,15(6):630-632
The phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS) catalyzes the phosphorylation and transportation of its sugar substrates. A sugar-specific enzyme II complex involved in the PTS finally functions to translocate substrates across the membrane. A PTS EIIB(fruc) protein, a fructose specific EIIB subunit, from Escherichia coli has been cloned, expressed, refolded, purified, and crystallized. The synchrotron data were collected to 2.6 A from the crystal of a selenomethionine substitute PTS EIIB(fruc) protein. The crystal belongs to the primitive trigonal space group P3(1)21, with unit-cell parameters of a = 33.4 A, b = 33.4 A, c = 154.0 A, and beta = 120.0 degrees . A full structure determination is under way to provide insights into the structure-function relationships of this protein. 相似文献
6.
Jian Liu Shi-Chu Liang Feng-Hong Liu Ren-Qing Wang Ming Dong 《Diversity & distributions》2005,11(4):341-347
Plant invasions have been attracting increasing attention from ecologists because of their worldwide environmental impacts and huge economic costs. Research on the characteristics of the recipient regions is essential for understanding the process of plant invasion. However, few previous studies on invasibility of habitats include social factors, although human activities are critical in the process of plant invasion. China is a vast country with high plant species diversity and a long history of introduction of exotic plant species and is particularly vulnerable to invasive plant species. Alien plant species are widespread in the country. Therefore, the study of invasive plants in China is urgent in practice and theoretically important for developing invasion ecology. For the present study, 126 species were selected to represent the major invasive plant species in China. We then collected data on their species richness in 31 provincial administrative units of China and performed Spearman rank correlations between species richness and possible natural and socio‐economic factors. We found that socio‐economic factors, such as human density and GDP, correlated positively with the species richness of invasive plants in China. In conjunction with the natural and socio‐economic correlations in the study of regional distribution pattern of the major invasive plants, we discussed the factors influencing the regional distribution pattern of the major invasive plants in China. We suggest that native plant species richness was mainly determined by the natural conditions of the regions, while invasive species richness was influenced by natural conditions and human disturbance together. 相似文献
7.
【背景】番茄黄化曲叶病毒(TYLCV)是由媒介昆虫烟粉虱传播的一种双生病毒,对蔬菜及烟草等经济作物造成严重危害。前人资料表明,该病毒于2006年传人我国南方地区,2007年传人山东省,2008年后在山东各地逐渐蔓延扩散。【方法】为了考证TYLcV传人山东省的时间,本研究利用mtCOI基因对于2005和2006年7—8月份在山东省不同地区作物上共采集的15份烟粉虱样品进行了生物型鉴定,并进一步检测了烟粉虱携带TYLCV情况,同时对PCR扩增产物进行了测序分析。【结果】2005年的4份样品烟粉虱生物型均为B型,均不携带TYLCV。2006年的11份烟粉虱样品为B型与Q型混合样品,其中,2份烟粉虱样品检测到TYLCV,进一步证实该病毒为TYLCV。【结论与意义】本研究首次证实了TYLCV早在2006年就已经传入山东省。研究结果不仅对于防控该病毒具有重要指导意义,而且对于其入侵生物学研究也具有重要参考价值。 相似文献
8.
We describe here a protocol for the detection of epithelial cells in effusions combined with quantification of apoptosis by flow cytometry (FCM). The procedure described consists of the following stages: culturing and induction of apoptosis by staurosporine in control ovarian carcinoma cell lines (SKOV-3 and OVCAR-8); preparation of effusion specimens and cell lines for staining; staining of cancer cells in effusions and cell lines for cell surface markers (Ber-EP4, EpCAM and CD45) and intracellular/nuclear markers of apoptosis (cleaved caspase-3 and caspase-8, and incorporated deoxyuridine triphosphates); and FCM analysis of stained cell lines and effusions. This protocol identifies a specific cell population in cytologically heterogeneous clinical specimens and applies two methods to measure different aspects of apoptosis in the cell population of interest. The cleaved caspase and deoxyuridine triphosphate incorporation FCM assays are run in parallel and require (including sample preparation, staining, instrument adjustment and data acquisition) 8 h. The culturing of cell lines requires 2-3 days and induction of apoptosis requires 16 h. 相似文献
9.
Jin Yan Dong Xing Ping Li Lei Li Guo Hong Li Ya Jun Liu Ke Qin Zhang 《Annals of microbiology》2006,56(2):163-166
One hundred and eighty one fungal species that were isolated from the fresh fruiting bodies collected in the Mountains of Pu Er County of Yunnan Province, China were tested on the pine wood nematode,Bursaphelenchus xylophilus in vitro. Each fungal species was grown in Czapek broth and potato dextrose broth (PDB). Fifteen filtrates fromAmauroderma austrosinense, Amauroderma macer, Filoboletus sp.,Laccaria tortilis, Lactarius gerardii, Lentinula edodes, Oudemansiella longipes, Oudemansiella mucida, Peziza sp.,Pleurotus sp.,Sinotermitomyces carnosus (two strains),Strobilomyces floccopus, Termitomyces albuminosus, Tylopilus striatulus grown on PDB were found to be pathogenic to the tested nematodes. Eleven filtrates fromAmanita junguillea, Amanita sp.,Daedalea sepiaria, Fistulina hepatica, Omphalotus olearius, Oudemansiella mucida, Peziza sp.,Pleurotus pulmatus, Ramaria sp.,Tricholoma conglobatum, Tylopilus striatulus grown on Czapek broth were also pathogenic to the nematodes. When screening for nematicidal potential of fungi, it is important to study the growth medium conditions necessary to obtain the optimal nematicidal effect as fungal filtrates growing on different liquid media showed a very inconsistent toxicity towards nematodes. 相似文献
10.
Recombinant adeno-associated virus(rAAV) has proven to be a promising gene delivery vector for human gene therapy. However, its application has been limited by difficulty in obtaining enough quantities of high-titer vector stocks. In this paper, a novel and highly efficient production system for rAAV is described. A recombinant herpes simplex virus type 1(rHSV-1) designated HSV1-rc/△UL2, which expressed adeno-associated virus type2(AAV-2) Rep and Cap proteins, was constructed previously. The data confirmed that its functions were to support rAAV replication and packaging, and the generated rAAV was infectious. Meanwhile, an rAAV proviral cell line designated BHK/SG2, which carried the green fluorescent protein(GFP) gene expression cassette, was established by transfecting BHK-21 cells with rAAV vector plasmid pSNAV-2-GFP. Infecting BHK/SG2 with HSV1-rc/△UL2 at an MOI of 0.1 resulted in the optimal yields of rAAV, reaching 250 transducing unit(TU) or 4.28×104 particles per cell. Therefore, compared with the conventional transfection method, the yield of rAAV using this "one proviral cell line, one helper virus" strategy was increased by two orders of magnitude. Large-scale production of rAAV can be easily achieved using this strategy and might meet the demands for clinical trials of rAAV-mediated gene therapy. 相似文献