全文获取类型
收费全文 | 1140篇 |
免费 | 57篇 |
国内免费 | 60篇 |
专业分类
系统科学 | 25篇 |
丛书文集 | 31篇 |
教育与普及 | 26篇 |
理论与方法论 | 10篇 |
现状及发展 | 29篇 |
综合类 | 1123篇 |
自然研究 | 13篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 19篇 |
2021年 | 23篇 |
2020年 | 33篇 |
2019年 | 29篇 |
2018年 | 12篇 |
2017年 | 37篇 |
2016年 | 33篇 |
2015年 | 47篇 |
2014年 | 52篇 |
2013年 | 51篇 |
2012年 | 76篇 |
2011年 | 88篇 |
2010年 | 44篇 |
2009年 | 69篇 |
2008年 | 51篇 |
2007年 | 81篇 |
2006年 | 51篇 |
2005年 | 61篇 |
2004年 | 62篇 |
2003年 | 44篇 |
2002年 | 39篇 |
2001年 | 23篇 |
2000年 | 33篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 14篇 |
1994年 | 21篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 10篇 |
1988年 | 3篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 2篇 |
排序方式: 共有1257条查询结果,搜索用时 109 毫秒
81.
82.
Immune responses to DNA vaccines 总被引:16,自引:0,他引:16
DNA vaccines, based on plasmid vectors expressing an antigen under the control of a strong promoter, have been shown to induce
protective immune responses to a number of pathogens, including viruses, bacteria and parasites. They have also displayed
efficacy in treatment or prevention of cancer, allergic diseases and autoimmunity. Immunologically, DNA vaccines induce a
full spectrum of immune responses that include cytolytic T cells, T helper cells and antibodies. The immune response to DNA
vaccines can be enhanced by genetic engineering of the antigen to facilitate its presentation to B and T cells. Furthermore,
the immune response can be modulated by genetic adjuvants in the form of vectors expressing biologically active determinants
or by more traditional adjuvants that facilitate uptake of DNA into cells. The ease of genetic manipulation of DNA vaccines
invites their use not only as vaccines but also as research tools for immunologists and microbiologists.
Received 26 October 1998; received after revision 3 December 1998; accepted 3 December 1998 相似文献
83.
本文分析了本世纪八十年代金衢盆地的气候变化趋势。与前三个年代(五十、六十、七十年代)比较,八十年代具有变冷,少光,洪涝灾害频繁的趋势特征。同时,春季“三寒”(倒春寒、种田寒、5月寒),晚春初夏异常高温危害,夏凉,冬暖等异常现象突出。着重分析了气候变化及灾害演变对农林环境的不利影响,讨论了九十年代气候变异趋势及其对策。 相似文献
84.
Peat record reflecting Holocene climatic change in the Zoigê Plateau and AMS radiocarbon dating 总被引:2,自引:0,他引:2
Weijian?ZhouEmail author Xuefeng?Lu Zhengkun?Wu Lin?Deng A.?J.?T.?Jull D.?Donahue W.?Beck 《科学通报(英文版)》2002,47(1):66-70
Through the use of reliable AMS dating of high resolution (15–30 years) peat and the establishment of monsoon climate proxies
sequence, we have been able to recognize several cold, dry events in the Tibetan Plateau during the Holocene. The more obvious
ones occurred around 12800, 11300, 10200, 9580, 8900, 6400, 4400, 3700, 2800 and 1500 cal. aBP. These events correlate well
with both ice rafting events recorded in high latitude North Atlantic Ocean sediment cores and cooling events in the low latitude
SST. Spectral analysis indicates high frequency climate variation on centennial-millennial time scale during the Holocene.
This further reflects Holocene climate instability and the existence of centennial-millenium scale rhythm in mid latitude
areas as well. 相似文献
85.
庐山旅游气候资源评价及深度开发 总被引:8,自引:0,他引:8
气候资源是旅游事业开发中极为重要的资源之一.通过分析庐山旅游气候资源优势,对庐山风景区的旅游气候优势及人体舒适指数进行了评价,指出深度开发和利用庐山旅游气候资源是庐山旅游业实现可持续发展的重要途径之一. 相似文献
86.
LIJianping CHOUJifan 《科学通报(英文版)》2003,48(10):1034-1039
The idea and main theoretical results of the global analysis theory of climate system are briefly summarized in this paper. A theorem on the global behavior of climate system is given, i.e. there exists a global attractor in the dynamical equations of climate, any state of climate system will be evolved into the global attractor as time increases,indicating the nonlinear adjustment process of climate system to external forcing. The different effects of external forcing, dissipation and nonlinearity on the long-term behavior of solutions are pointed out, and some main applications of the global analysis theory are also introduced. Especially, three applications, the adjustment and evolution processes of climate, the principle of numerical model design and the optimally numerical integration, are discussed. 相似文献
87.
WANG Weiming LIU Jinling & ZHOU Xiaodan . Nanjing Institute of Geology Palaeontology Chinese Academy of Sciences Nanjing China . Nanjing Geological Museum Nanjing China Correspondence should be addressed to Wang Weiming 《科学通报(英文版)》2003,48(18):2005-2009
Many related papers have been published since the first report on the discovery of Nanjing hominid crania by Mu et al.[1]. Mu et al.[1], Xu et al.[2—4], the Tangshan Ar-chaeological Team[5] and Dong[6] have successively stud-ied the Nanjing Homo erectus?symbiotic faunas. Mu et al. and Xu et al. considered that the nature of the fauna in the Tangshan area belongs to the Oriental Realm,and this region was usually occupied by Ailuropoda-Tapirus fauna in the Pleistocene. However, the typica… 相似文献
88.
从气候角度阐明了大同市干旱的分类特点、时空分布特征以及发生规律,对引起大同干旱的原因进行了分析,并提出了抗旱的对策和建议。 相似文献
89.
通过对朔州市2006年度气象要素、重大天气事件及灾害性天气的分析,探讨了天气气候对农业产量丰歉的影响。 相似文献
90.
架空线路应力控制气象条件的判定,需要考虑控制气象条件及弧垂限制等条件,一般采用临界档距判定法或试推比较法处理.本文建立了解决该问题的多目标优化数学模型,并采用罚函数法求解模型,算例证明了相对于传统方法的优越性. 相似文献