全文获取类型
收费全文 | 17535篇 |
免费 | 142篇 |
国内免费 | 343篇 |
专业分类
系统科学 | 50篇 |
丛书文集 | 141篇 |
教育与普及 | 78篇 |
理论与方法论 | 7篇 |
现状及发展 | 201篇 |
研究方法 | 1篇 |
综合类 | 17535篇 |
自然研究 | 7篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 49篇 |
2021年 | 40篇 |
2020年 | 52篇 |
2019年 | 39篇 |
2018年 | 42篇 |
2017年 | 59篇 |
2016年 | 226篇 |
2015年 | 478篇 |
2014年 | 1168篇 |
2013年 | 528篇 |
2012年 | 912篇 |
2011年 | 1745篇 |
2010年 | 1523篇 |
2009年 | 1284篇 |
2008年 | 1765篇 |
2007年 | 2196篇 |
2006年 | 1481篇 |
2005年 | 1255篇 |
2004年 | 754篇 |
2003年 | 642篇 |
2002年 | 450篇 |
2001年 | 337篇 |
2000年 | 228篇 |
1999年 | 167篇 |
1998年 | 131篇 |
1997年 | 82篇 |
1996年 | 74篇 |
1995年 | 57篇 |
1994年 | 68篇 |
1993年 | 35篇 |
1992年 | 35篇 |
1991年 | 35篇 |
1990年 | 29篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
范文芳 《科技情报开发与经济》2008,18(7):94-95
介绍了高校图书馆开放时间的现状,分析了影响图书馆开放时间的因素,探讨了合理安排图书馆开放时间的措施。 相似文献
32.
介绍了CALIS分布式联合虚拟参考咨询系统CDCVRS,在调查排名前50位的大学图书馆使用CDCVRS的情况基础上,总结了CDCVRS使用过程中存在的问题,提出了相应的解决办法。 相似文献
33.
《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
34.
35.
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
36.
王滨 《科技情报开发与经济》2007,17(21):101-102
简述了素质教育的含义,分析了图书馆在素质教育中所处的地位和具备的优势,探讨了图书馆开展素质教育的有效途径。 相似文献
37.
浅谈网络环境下高校图书馆信息资源建设 总被引:1,自引:0,他引:1
王广东 《科技情报开发与经济》2007,17(33):29-30
阐述了网络环境下高校图书馆信息资源建设存在的主要问题,探讨了网络环境对信息资源建设的影响,提出了信息资源建设的具体措施。 相似文献
38.
黄琼霞 《科技情报开发与经济》2007,17(15):45-46
论述了图书馆联机联合编目的现状,探讨了联机联合编目与资源共享的意义,提出了新形势下实现联机联合编目与资源共享的若干对策。 相似文献
39.
徐惠萍 《科技情报开发与经济》2007,17(36):18-20
分析了大学生产生心理疾病的原因,探讨了"阅读治疗"对大学生心理健康的作用,提出了高校图书馆开展阅读治疗的措施。 相似文献
40.