全文获取类型
收费全文 | 307篇 |
免费 | 29篇 |
国内免费 | 72篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 15篇 |
2021年 | 22篇 |
2020年 | 25篇 |
2019年 | 17篇 |
2018年 | 24篇 |
2017年 | 29篇 |
2016年 | 20篇 |
2015年 | 22篇 |
2014年 | 29篇 |
2013年 | 20篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 12篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1992年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有408条查询结果,搜索用时 265 毫秒
101.
广西岩溶地区茶条木群落特征与人工造林研究初报 总被引:1,自引:0,他引:1
采用样方法调查分析了广西岩溶地区茶条木(Delavaya toxocarpa Franch.)的2个自然林群落(田阳县那满镇和那坡镇)和1个人工林群落(德保县隆桑镇)的基本特征,并对龙何示范区内不同生境中茶条木人工林的植株生长状况进行了分析.结果表明,不同茶条木群落的群落外貌、群落结构和种类组成等均存在较明显的差异,与群落位置、起源、存续时间和人为干扰强度等有关;自然林群落的种类组成比较复杂且层次不够分明,而人工林群落的种类组成则比较简单但结构较完整.茶条木具有耐瘠耐旱能力强、喜光、萌蘖力较强及林下更新能力较差等生态特性.在龙何示范区内,茶条木人工林具有造林成活率高、生长迅速及开花结实早等特点,且在不同生境中茶条木的造林效果差异比较明显;以光裸地上茶条木的生长最佳,灌草丛地茶条木的生长最差,初步显示出茶条木耐瘠耐旱能力强、适生于石漠化山区且速生早实等优良特性.研究结果显示,茶条木是一种适生于岩溶山地干旱瘠薄环境的乡土先锋树种,在桂西南岩溶山区荒山绿化尤其是石漠化地区植被恢复工程中值得进一步推广利用. 相似文献
102.
103.
Zekuan Lu Lei Zhai Hui Wang Qiaolin Che Duo Wang Feifei Feng Zongmao Zhao Haining Yu 《Biochimie》2010
Xizang plateau frog (Nanorana parkeri) captured in Lhasa, Tibet, China, solely lives in the subtropical plateau, where there is strong ultraviolet radiation and long duration of sunshine. Considering its harsh living environment, the frog's innate defense against microbes and environmental stress was investigated. In current study, three antimicrobial peptides (AMPs) were purified and characterized from the skin secretion of N. parkeri. The coding cDNA sequences were also cloned from the skin cDNA library of N. parkeri. By structural characterization, two peptides were identified belonging to Japonicin-1 family, and named as Japonicin-1Npa (FLLFPLMCKIQGKC) and Japonicin-1Npb (FVLPLVMCKILRKC). The third peptide isolated named Parkerin with a unique sequence of GWANTLKNVAGGLCKITGAA did not show similarity to any known amphibian AMPs. Multi-functions of three AMPs were examined (antioxidant, MCD, hemolytic etc). Their solution structures determined by CD and antimicrobial mechanisms investigated by SEM are very well consistent with their functional characters. Current result suggests that these novel multi-functional AMPs could play an important role in defending N. parkeri against environmental oxidative stress and pathogenic microorganisms, which may partially reveal the ecological adaptation of these plateau-living amphibians. 相似文献
104.
Miao Duo Mi Zhang Yan-Yeung Luk Dacheng Ren 《Applied microbiology and biotechnology》2010,85(5):1551-1563
Candida albicans is the most virulent Candida species of medical importance, which presents a great threat to immunocompromised individuals such as HIV patients. Currently,
there are only four classes of antifungal agents available for treating fungal infections: azoles, polyenes, pyrimidines,
and echinocandins. The fast spread of multidrug resistant C. albicans strains has increased the demand for new antifungal drugs. In this study, we demonstrate the antifungal activity of brominated
furanones on C. albicans. Studying the structure and activity of this class of furanones reveals that the exocyclic vinyl bromide conjugated with
the carbonyl group is the most important structural element for fungal inhibition. Furthermore, gene expression analysis using
DNA microarrays showed that 3 μg/mL of 4-bromo-5Z-(bromomethylene)-3-butylfuran-2-one (BF1) upregulated 32 C. albicans genes with functions of stress response, NADPH dehydrogenation, and small-molecule transport, and repressed 21 genes involved
mainly in cell-wall maintenance. Interestingly, only a small overlap is observed between the gene expression changes caused
by the representative brominated furanone (BF1) in this study and other antifungal drugs reported in literature. This result
suggests that brominated furanones and other antifungal drugs may target different fungal proteins or genes. The existence
of such new targets provides an opportunity for developing new agents to control fungal pathogens which are resistant to currently
available drugs. 相似文献
105.
非洲山毛豆叶片蛋白组双向电泳样品制备方法的建立 总被引:2,自引:0,他引:2
以非洲山毛豆叶片为材料,对非洲山毛豆总蛋白质3种提取方法(TCA/丙酮沉淀法、尿素/硫脲法和酚-甲醇/醋酸铵沉淀法)以及3种蛋白裂解液进行比较分析。结果表明,采用酚-甲醇/醋酸铵沉淀法提取非洲山毛豆叶片总蛋白,用蛋白裂解液(7mol/L尿素,2mol/L硫脲,4%CHAPS,40mmol/LTris-base,1%Bio-LytepH3.5-10,65mmol/LDTT)裂解蛋白1h,2-DE图谱分离到的蛋白点效果最好。此方法适合于色素、多酚及黄酮类次生代谢物含量较多的非洲山毛豆叶片总蛋白制备方法。 相似文献
106.
Goto A Takebayashi Y Liu D Li L Saiga T Mori T Yamadera A Fukumoto M 《Radiation research》2002,158(1):54-60
Thorotrast is a colloidal suspension of radioactive (232)ThO(2) that naturally emits alpha particles (90%), beta particles and gamma rays (10%). Thorotrast was used as a radiographic contrast agent in the 1930s-1950s; it caused liver cancer several decades after injection because of its life-long deposition and exposure. Determination of the amount and the distribution of radioactive thorium are essential for assessment of radiation risks. We visualized alpha particles on ordinary archival tissue sections using an imaging plate and a BAS5000 image analyzer. Furthermore, we confirmed that the imaging system is sensitive enough to detect alpha particles and accurate in measuring the total amount of thorium deposited in the organ from a single tissue section. This method revealed that the amount of thorium deposited in tumor tissue is correlated to that in non-tumor tissue. Thorotrast deposition was not associated with DNA damage determined by histochemistry. In combination with histological findings, it is suggested that radioactive thorium always migrates within the deposited organs by macrophages, and that the organs are evenly exposed to alpha particles. 相似文献
107.
Liang H Kays MB Sowinski KM 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2002,772(1):53-63
A selective, sensitive and accurate liquid chromatographic method with UV and fluorescence detection was developed, validated and applied for the determination of fluoroquinolones in human plasma. The effects of mobile phase composition, ion-pair and competing-base reagents, buffers, pH, and acetonitrile concentrations were investigated on the separation of six quinolones (cinoxacin, levofloxacin, ciprofloxacin, gatifloxacin, moxifloxacin and trovafloxacin). Sample preparation was carried out by adding internal standard and displacing agent and processing by ultrafiltration. This method uses ultraviolet and fluorescence detection and separation using a C(18) column. The recovery, selectivity, linearity, precision, and accuracy of the method were evaluated from spiked human plasma samples. The method was successfully applied to patient plasma samples in support of a levofloxacin pharmacokinetic study. 相似文献
108.
Quanzhi Li Wendy Hudson Duo Wang Erica Berven Fatih M. Uckun John H. Kersey 《Cancer immunology, immunotherapy : CII》1998,47(3):121-130
The comparative advantages and disadvantages of intact antibodies and single-chain Fv as immunotoxins and radioimmunoconjugates
have been widely discussed but not directly compared. In this study, the in vivo properties of anti-CD19 B43 monoclonal antibody
and its derived single-chain Fv (FVS191) were studied in athymic nude mice bearing CD19-positive human lymphomas. B43 mab
and FVS191 were labeled with iodine-125 using iodine-beads, and immunoreactivities were determined to be 57% and 72%, respectively.
Scatchard analysis showed a similar high affinity for both. The results of pharmacokinetic studies revealed that FVS191 had
a rapid biphasic clearance from the circulation (T1/2α = 2.5 min, T1/2β = 3.7 h); The T1/2α and T1/2β phases of B43 mab were
determined to be 0.72 h and 57 h respectively. Biodistribution studies compared the uptake of labeled antibodies by CD19-positive
and by CD19-negative tumors. The peak percentages of injected dose were 5.7% at 12 h for B43 and 2.45% at 1 h for FVS191.
Radiolocalization indices (RI) demonstrated tumor-specific uptake for both, but higher uptake for B43. The optimal RI was
seen at 15 min for FVS191 and 6 h for B43. FVS191 was unstable in vivo, approximately 50% of the injected dose being degraded
in blood in 100 min. Radioactivity detected in the urine was present mainly as the deiodinized form of FVS191. The results
suggest that B43 mab is favored over FVS191 in biodistribution properties and in vivo stability. Because B43 Mab showed early
tumor-specific uptake, high RI values, and favorable tissue-to-blood ratios, it is a potential candidate for radioimmunotherapy
and immunotoxin therapy of B-cell leukemia and lymphoma.
Received: 17 June 1997 / Accepted: 17 June 1998 相似文献
109.
XIA Jiahui ZHENG Duo TANG Dongsheng DAI Heping PAN Qian LONG Zhigao LIAO Xiaodong 《中国科学C辑(英文版)》2001,44(1)
By homologous EST searching and nested PCR a new human gene GJB5encoding gap junction protein b-5 was identified. GJB5 was genetically mapped to human chromosome 1p33-p35 by FISH. RT-PCR revealed that it was expressed in skin, placenta and fetal skin. DNA sequencing of GJB5 was carried out in 142 patients with sensorineural hearing impairment and probands of 36 families with genetic diseases, including erythrokeratodermia (5 families), Charcot-Marie-Tooth disease (13), ptosis (4), and retinitis pigmentosa and deafness (14). Two missense mutations (686A→G, H229R; 25C→T, L9F) were detected in two sensorineural hearing impairment families. A heterologous deletion of 18 bp within intron was found in 3 families with heredity hearing impairment, and in one of the 3 families, a missense mutation (R265P) was identified also. But the deletion and missense mutation seemed not segregating with hearing impairment in the family. No abnormal mRNA or mRNA expression was detected in deletion carriers by RT-PCR analysis in skin tissue. Mutation analysis in 199 unaffected individuals revealed that two of them were carriers with the same 18 bp deletion. 相似文献
110.
色彩是评价园艺植物观赏性状的重要指标,而植物色素是影响植物色彩表型的关键因子。植物色素及其代谢产物在植物观赏器官颜色形成、植株生长发育调节及对逆境胁迫的响应等方面发挥着重要的作用,是植物研究领域长期关注的热点问题。病毒诱导基因沉默(virus-induced gene silencing,VIGS)是利用植物同源依赖性防御机制,特异性降低宿主内源性基因表达的一种重要基因组学工具,能够通过快速诱导植物基因沉默表型的产生,表征基因的功能,为缺乏遗传转化体系的植物的基因功能鉴定提供高效可行的替代方案。本文综述了VIGS技术在植物色素的生物合成、降解和调控机制上的应用现状,并探讨了VIGS技术在探究色素调控机制上的潜力和未来前景,以期进一步完善对不同植物色素的代谢过程和调控机制的理解,为改良植物色彩性状提供参考依据。 相似文献