全文获取类型
收费全文 | 6194篇 |
免费 | 272篇 |
国内免费 | 655篇 |
专业分类
系统科学 | 404篇 |
丛书文集 | 174篇 |
教育与普及 | 66篇 |
理论与方法论 | 41篇 |
现状及发展 | 297篇 |
研究方法 | 1篇 |
综合类 | 6104篇 |
自然研究 | 34篇 |
出版年
2024年 | 10篇 |
2023年 | 41篇 |
2022年 | 108篇 |
2021年 | 120篇 |
2020年 | 119篇 |
2019年 | 105篇 |
2018年 | 77篇 |
2017年 | 133篇 |
2016年 | 109篇 |
2015年 | 168篇 |
2014年 | 265篇 |
2013年 | 238篇 |
2012年 | 357篇 |
2011年 | 366篇 |
2010年 | 294篇 |
2009年 | 410篇 |
2008年 | 402篇 |
2007年 | 477篇 |
2006年 | 459篇 |
2005年 | 421篇 |
2004年 | 389篇 |
2003年 | 347篇 |
2002年 | 336篇 |
2001年 | 252篇 |
2000年 | 198篇 |
1999年 | 167篇 |
1998年 | 151篇 |
1997年 | 84篇 |
1996年 | 95篇 |
1995年 | 83篇 |
1994年 | 70篇 |
1993年 | 45篇 |
1992年 | 44篇 |
1991年 | 44篇 |
1990年 | 38篇 |
1989年 | 35篇 |
1988年 | 20篇 |
1987年 | 10篇 |
1986年 | 16篇 |
1985年 | 10篇 |
1984年 | 1篇 |
1981年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有7121条查询结果,搜索用时 656 毫秒
11.
12.
构建T7噬菌体展示禽流感病毒抗原变异性基因片段文库. 首先, 从Gene Bank中查找筛选禽流感病毒抗原变异性基因, 将其截短、 修饰、 简并后得到禽流感病毒抗原变异性基因微阵列. 其次, 将合成的禽流感病毒抗原变异性基因片段文库扩增、 酶切, 链接到双酶切后的T7噬菌体载体基因上, 构成重组噬菌体DNA. 最后, 重组噬菌体DNA经体外包装和扩增, 得到T7噬菌体展示文库, 并进行T7噬菌体展示文库滴度、 重组率和免疫活性测定. 实验结果表明, 从Gene Bank中查找、 筛选、 剪切和修饰共获得96 258条序列构建T7噬菌体展示文库, 原始文库滴度为3.6×107个菌落/mL, 重组率大于90%. 用禽流感病毒H5N1抗体进行捕获, 经聚合酶链式反应(PCR)鉴定, 得到理想目的条带, 证明噬菌体表面展示蛋白具有抗原活性, 可用于禽流感病毒感染患者的快速检测及抗原表位筛选. 相似文献
13.
《科学通报(英文版)》2008,(19)
The purposes of this research were to study the stable expression of exogenous gene encoding therapeutic protein in attenuated Salmonella typhimurium, observe the metabolism of oral gene vaccine carried by attenuated Salmonella typhimurium in BALB/c mouse, and investigate the feasibility of prevention and treatment of tumors by the recombinant bacteria. Recombinant plasmid pcDNA3.1 VEGFR2(n1-7) was transformed into competent attenuated Salmonella typhimurium SL3261 to develop oral DNA vaccine SL3261-pcDNA3.1 VEGFR2(n1-7). To observe whether the exogenous gene can be expressed in the recombinant bacteria, PCR was performed to amplify the CMV promoter of the eukaryotic expression vector as the proof of stable expression of exogenous protein; transmission elec- tron microscopy (TEM) was applied to observe the morphology of the recombinant bacteria to confirm that the exogenous gene has no impact on the growth of the bacteria, and then BALB/c mice were immunized with the gene vaccine. After inoculation of the gene vaccine, the recombinant bacteria SL3261 could be detected in the tissues such as small intestine, colon, liver and spleen. And then, mice in each group were challenged with tumor cells. The results of animal experiment showed that tumor growth of the mice in experimental group was inhibited and survival time of immunized mice was prolonged compared with control groups. A higher lymphocyte infiltration in tumors from animals treated with DNA vaccine was observed. Immunohistochemical analysis of tumor samples revealed an en- hanced accumulation of CD8 cytotoxic T lymphocytes, as well as an increase in CD4 cells in the tumors of animals treated with the oral gene vaccine compared to tumors from control group mice. Ultrastructure of the tumor tissue showed that tumor cells in the samples of the immunized mice were well-differentiated. Our research confirmed that the exogenous gene can be stably expressed in the attenuated Salmonella typhimurium and has no impact on the growth of the recombinant bacteria; the exogenous gene can de delivered to the host by attenuated Salmonella typhimurium to produce anti-tumor effect with no obvious cytotoxity to the host. In this study, it is established that attenuated Salmonella typhimurium could be used as a vector for oral gene vaccine, and our study provided a theoretical basis for the body distribution and the metabolism of the recombinant bacteria. This strategy may provide a simple, safe and effective way for the prevention and treatment of tumors. 相似文献
14.
15.
The study of candidate genes over the past three decades has yielded notable successes in common-disease genetics. During
this time, however, interpretation of genetic association studies has been hampered by the use of clinical cohorts of inadequate
power and insufficient information on genetic variation in candidate genes. The unavailability of highthroughput and low-cost
genotyping technologies has also limited the scope of complex-disease genetic studies. More recently, however, the sequencing
and characterization of variation within the human genome has revolutionized genetic studies and enabled full genome-wide
scans for genes associated with disease. The identification of disease-associated (causative) genes has illuminated disease
mechanisms. The translation of this knowledge into direct clinical benefit in diagnosis, prognosis and therapy for an individual’s
disease still remains a challenge.
Received 11 September 2006; received after revision 17 December 2006; accepted 18 January 2007 相似文献
16.
17.
Finding finer functions for partially characterized proteins by protein-protein interaction networks
LI YanHui GUO Zheng MA WenCai YANG Da WANG Dong ZHANG Min ZHU ding ZHONG GuoCai LI YongJin YAO Chen WANG Jing 《科学通报(英文版)》2007,52(24):3363-3370
Based on high-throughput data, numerous algorithms have been designed to find functions of novel proteins. However, the effectiveness of such algorithms is currently limited by some fundamental factors, including (1) the low a-priori probability of novel proteins participating in a detailed function; (2) the huge false data present in high-throughput datasets; (3) the incomplete data coverage of functional classes; (4) the abundant but heterogeneous negative samples for training the algorithms; and (5) the lack of detailed functional knowledge for training algorithms. Here, for partially characterized proteins, we suggest an approach to finding their finer functions based on protein interaction sub-networks or gene expression patterns, defined in function-specific subspaces. The proposed approach can lessen the above-mentioned problems by properly defining the prediction range and functionally filtering the noisy data, and thus can efficiently find proteins’ novel functions. For thousands of yeast and human proteins partially characterized, it is able to reliably find their finer functions (e.g., the translational functions) with more than 90% precision. The predicted finer functions are highly valuable both for guiding the follow-up wet-lab validation and for providing the necessary data for training algorithms to learn other proteins. 相似文献
18.
季文媚 《合肥学院学报(自然科学版)》2008,18(2):69-71
中国传统建筑文化内涵丰富,其各种建筑活动几乎无不受到所谓风水理念的深刻影响.从通俗和专业两个不同角度对“风水”这一概念进行了解释,并分析了中国源远流长的风水理念对传统建筑选址和布局的影响,从而总结出在风水理念影响下的中国传统建筑空间构成特征——重重封闭的内向性空间. 相似文献
19.
小麦群体连续选择效应的综合分析 总被引:1,自引:1,他引:0
本试验对由信谷核不育基因构成的异效群体内4个性状进行连续两轮歧化选择,并将所得数据进行群体综合分析。结果表明:整个群体的平均表现和变异程度未发明显变化;但群体分布状况有一定改变,尤其是每穗粒数的分布数化较为明显;株高和千粒重的有效因子数估计基本符合小麦遗传实际表现,每穗粒数的有效有效因子数估计略低,说明此性状遗传背景较为简单。 相似文献
20.
重组人CNB高表达大肠杆菌已由本室构建成功,摇瓶发酵液表达量可达100mg·L-1. 通过改进培养基配方及摇瓶表达工艺,使CNB在摇瓶发酵液中表达量达到500mg*L-1以上.在高表达量的基础上,又进行了产业化改进,以蒸馏水添加无机盐取代了原配方中的自来水,并提高了表达量. 相似文献