全文获取类型
收费全文 | 16316篇 |
免费 | 1653篇 |
国内免费 | 4500篇 |
出版年
2024年 | 61篇 |
2023年 | 341篇 |
2022年 | 627篇 |
2021年 | 1002篇 |
2020年 | 804篇 |
2019年 | 915篇 |
2018年 | 698篇 |
2017年 | 579篇 |
2016年 | 711篇 |
2015年 | 1030篇 |
2014年 | 1351篇 |
2013年 | 1266篇 |
2012年 | 1606篇 |
2011年 | 1478篇 |
2010年 | 1029篇 |
2009年 | 933篇 |
2008年 | 1101篇 |
2007年 | 925篇 |
2006年 | 932篇 |
2005年 | 809篇 |
2004年 | 696篇 |
2003年 | 565篇 |
2002年 | 540篇 |
2001年 | 472篇 |
2000年 | 410篇 |
1999年 | 314篇 |
1998年 | 210篇 |
1997年 | 135篇 |
1996年 | 121篇 |
1995年 | 140篇 |
1994年 | 85篇 |
1993年 | 69篇 |
1992年 | 80篇 |
1991年 | 60篇 |
1990年 | 50篇 |
1989年 | 55篇 |
1988年 | 39篇 |
1987年 | 36篇 |
1986年 | 29篇 |
1985年 | 33篇 |
1984年 | 29篇 |
1983年 | 24篇 |
1982年 | 21篇 |
1981年 | 9篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1957年 | 8篇 |
1954年 | 4篇 |
1951年 | 6篇 |
1950年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
绝经后骨质疏松症(PMO)是一种多基因调控的遗传性疾病。雌激素受体β亚型基因是骨质疏松症的重要侯选基因。此文采用病例对照设计(78名股骨颈PMO病人和122名对照以及108名腰椎PMO病人和92名对照)研究中国人(汉族)雌激素受体β基因(ESR2)第5内含子CA重复序列多态性与PMO的相关性。以CA重复序列平均数22次为界将重复序列基因分为短基因(<22)和长基因(≥22),分别以S和L表示。股骨颈及腰椎(L2-4)部位,病例组中LL基因型和L等位基因者频率显著高于对照组(P<0.01),SL、LL及SL LL基因型者较SS基因型者患PMO风险显著增高(P<0.05);调整年龄、绝经时间、绝经年龄及体质指数后,Logistic回归分析显示ESR2(CA)n多态性仍然与股骨颈(OR4.923,95%CI1.986~12.203,P=0.001)及L2-4(OR2.267,95%CI1.121~4.598,P=0.023)PMO显著相关。结果显示:ESR2基因CA重复序列多态性与股骨颈和L2-4部位PMO独立关联,L等位基因显性影响PMO的发病风险。 相似文献
952.
利用cDNA芯片技术从含有2,952个克隆的杨树芯片中筛选出1,160个受杨盘二孢菌诱导的基因。功能分析表明,该1,160个基因分别属于11个功能类别,除了功能未知基因外,参与新陈代谢、防御反应、信号传导及转录调控的基因最多,这4大类基因约占基因总数的42%。1,160个差异表达基因中有926个基因被定位于19条染色体上,其中被定位于第Ⅱ条染色体上的差异基因最多,共102个(11.0%),其次是第Ⅰ条染色体,共93个(10%),被定位到第ⅩⅦ条染色体上的差异基因最少,仅有11个,基因在染色体上的分布则表现为在部分染色体的末端区域存在大量的聚集,在中间区段则相对较少和排列稀疏,基因的这种分布情况与植物抗病的关系有待进一步研究。 相似文献
953.
PENG JunPing ZHANG XiaoBing YANG E WANG Jing YANG Jian SHAO ZhuJun & JIN Qi 《中国科学:生命科学英文版》2007,50(1):1-6
Neisseria meningitidis is a major cause of bacterial meningitis and septicemia worldwide. In China, serogroup A strains were responsible for over 95% of the cases, while serogroup B strains were mainly the cause of localized outbreaks and sporadic cases. Before 2003, serogroup C strains were only re-covered from a few sporadic cases. However, a sudden increase in the number of cases due to sero-group C strains occurred during 2003—2005 in Anhui Province, China. Many cases were found in other provinces at the same time. Multilocus sequence typing (MLST) results indicated that the unique se-quence type 4821 clone meningococci, a new hyper-virulent lineage, was responsible for the serogroup C meningitis outbreaks. We have completed the project of sequencing the whole genome of the Chi-nese N. meningitidis serogroup C representative isolate 053442. We fabricated a whole-genome mi-croarray of N. meningitidis isolate 053442 and analyzed the genome composition differences among 81 serogroup C isolates which were isolated from 14 provinces of China during 1966—2005. The com-parative genomic hybridization (CGH) result shows that the genome compositions of nearly all sero-group C isolates are similar to that of 053442. The products of many absent open reading frames (ORFs) are conserved hypothetical proteins. The results will provide a valuable resource from which one can analyze the genome composition and genetic background of serogroup C meningococci in China. 相似文献
954.
Li Yang LingLing Wang JunPing Peng Lu Yu Tao Liu WenChuan Leng Jian Yang LiHong Chen WenLiang Zhang Qian Zhang YiPeng Qi Qi Jin 《中国科学:生命科学英文版》2007,50(3):377-384
Trichophyton rubrum is a dominating superficial dermatophyte, whose conidial germination is correlated to pathopoiesis and a highly important
developmental process. To investigate the changes of physiology, biochemistry and cytology during the germination, we selected
3364 function identified ESTs from T. rubrum cDNA library to construct cDNA microarrays, and compared the gene expression levels of conidia and germinating phase. Data
analysis indicated that 335 genes were up-regulated during the germination, which mainly encoded translated, modified proteins
and structural proteins. The constituents of cell wall and cell membrane were synthetized abundantly, suggesting that they
are the foundation of cell morphogenesis. The ingredients of the two-component signal transduction system were up-regulated,
presuming that they were important for the conidial germination. Genes of various metabolic pathways were expressed prosperously,
especially the genes that participated in glycolysis and oxidative phosphorylation were up-regulated on the whole, demonstrating
that in the environment with sufficient oxygen and glucose, conidia obtained energy through aerobic respiration. This paper
provides important clues which are helpful to understanding the changes in gene expression, signal conduction and metabolism
characteristics during T. rubrum conidial germination, and possess significant meaning to the study of other superficial dermatophytes.
Supported by the National High Technology Research and Development Program of China (Grant No. 2001AA223021) and National
Key Technologies R&D Programme (Grant No. 2002BA711A14) 相似文献
955.
SUN QiangLing LIU YinKun LU WenJing CHENG Gang ZHOU HaiJun ZHOU XinWen WEI LiMing DAI Zhi GUO Kun LU HaoJie
《中国科学:生命科学英文版》2007,50(3):403-411
《中国科学:生命科学英文版》2007,50(3):403-411
In order to establish the novel high throughput, high efficiency and Iow cost technological platform for the research of N-glycoproteomics, to resolve the significance of characteristic expression profile of glycoprotein and to find the proteins with biological functional importance, the glycoproteins with high-mannose core and the two antennary types were purified and enriched by the Con A affinity chromatography. Con A affinity protein expression profiles of normal human liver tissue were generated by using SDS-PAGE, two-dimensional electrophoresis (2-DE) followed by fast fluorescence staining based on multiplexed proteomics (MP) technology. 301 visible protein spots on the gel were detected and 85 of glycoproteins were further successfully identified via peptide mass fingerprinting (PMF) by a matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS/MS) and annotated to IPI databases. Identified glycoproteins definitely take part in the regulation of cell cycle and metabolic processes. The glycosylation sites were predicted with NetNGlyc 1.0 and NetOGlyc 3.1 software, meanwhile they were classified according to the geneontology methods. The construction of Con A affinity glycoprotein database of normal human liver tissue would contribute to the subsequent research. 相似文献
956.
寄生蜂毒液和卵巢蛋白在寄生过程中起着重要作用,蛋白成分和性质的研究日益深入.本文主要通过SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)试验,分析了腰带长体茧蜂毒液和卵巢蛋白的分子量组成.结果表明,腰带长体茧蜂毒液蛋白图谱显示约有7条蛋白带介于43~100 kDa之间,含量较高的三条带为97kDa、64kDa、45kDa;卵巢蛋白图谱显示约有12条蛋白带,位于30~200 kDa之间,含量较高的两条带为39kDa、43kDa.并对毒液和卵巢的生物学功能进行了探讨. 相似文献
957.
蔗糖是植物体内碳水化合物长距离转运的主要( 甚至唯一) 形式, 为植物生长发育提供碳架与能量。蔗糖转运蛋白(sucrose transporter, SUT)负责蔗糖的跨膜运输, 在韧皮部介导的源-库蔗糖运输, 以及库组织的蔗糖供给中起关键作用。自从菠菜中克隆到第一个SUT基因以来, 已先后有多个SUT基因的cDNA得到克隆与功能分析, 涉及34种双子叶与单子叶植物。每种植物都有一个中等规模
的SUT基因家族, 其不同成员之间具有较高的氨基酸序列同源性, 但在蔗糖吸收的动力学特性、转运底物的特异性和表达谱等方面存在差异。本文系统介绍国内外(主要是国外)在植物SUT基因的克隆、分类与进化、细胞定位与功能, 以及研究方法等方面的研究进展, 并简要介绍我们在橡胶树SUT基因研究上的初步结果。 相似文献
958.
John M. Boettcher Kevin L. Hartman Daniel T. Ladror Zhi Qi Wendy S. Woods Julia M. George Chad M. Rienstra 《Biomolecular NMR assignments》2007,1(2):167-169
13C, 15N, and 1H chemical shift assignments are presented for the cAMP-regulated phosphoprotein endosulfine-alpha in its free and micelle-bound
states. Secondary chemical shift analysis demonstrates formation of four helices in the micelle-bound state, which are not
present in the absence of detergent. 相似文献
959.
以富贵草(Pachysandra terminalis Sieb.et Zucc.)(以下简称PT)为实验材料,采用开放式浸杀法研究其植物原粉及提取物(PT-Ⅰ)对钉螺的杀灭效果和对鱼类的毒性作用。结果表明PT原粉浓度为17.5 mg/L时,钉螺72 h死亡率为93.4%,120 h死亡率达100.0%;其24、72、120、168 h的LC50分别为42.28、7.20、4.20、3.17 mg/L。PT原粉浓度为75.0 mg/L时,经168 h鱼死亡率为0。使用浓度为35.0、17.5、8.75、4.38 mg/L的PT原粉,分别浸泡1、2、18、42 h时,抑制钉螺上爬率均达到100%。原粉经提取分离得到PT-Ⅰ组分,以1.40 mg/L的PT-Ⅰ组分分别浸杀钉螺24、48、72、96、120 h,钉螺死亡率分别为36.7%、73.3%、96.7%、96.7%、100.0%。表明PT具有很好的杀灭钉螺、抑制钉螺上爬效果,且对鱼毒性较低,是一种较有研究价值的灭螺植物。 相似文献
960.
Mycobacterium bovis bacillus Calmette-Guérin (BCG) vaccine has been known for a long time to prevent tuberculosis (TB) worldwide since 1921. Nonetheless, we know little about BCG membrane proteome. In the present study, we utilized alkaline incubation and Triton X-114-based methods to enrich BCG membrane proteins and subsequently digested them using proteolytic enzyme. The recovered peptides were further separated by 2-D LC and identified by ESI-MS/MS. As a result, total 474 proteins were identified, including 78 integral membrane proteins (IMPs). Notably, 18 BCG IMPs were described for the first time in mycobacterium. Further analysis of the 78 IMPs indicated that the theoretical molecular mass distribution of them ranged from 8.06 to 167.86 kDa and pI scores ranged from 4.40 to 11.60. Functional classification revealed that a large proportion of the identified IMPs (67.9%, 53 out of 78) were involved in cell wall and cell processes functional group. In conclusion, here we reported a comprehensive profile of the BCG membrane subproteome. The present investigation may allow the identification of some valuable vaccine and drug target candidates and thus provide basement for future designing of preventive, diagnostic, and therapeutic strategies against TB. 相似文献