全文获取类型
收费全文 | 43927篇 |
免费 | 244篇 |
国内免费 | 538篇 |
专业分类
系统科学 | 1213篇 |
丛书文集 | 82篇 |
教育与普及 | 277篇 |
理论与方法论 | 509篇 |
现状及发展 | 29061篇 |
研究方法 | 6篇 |
综合类 | 11373篇 |
自然研究 | 2188篇 |
出版年
2014年 | 392篇 |
2013年 | 800篇 |
2011年 | 2360篇 |
2009年 | 591篇 |
2008年 | 589篇 |
2007年 | 624篇 |
2006年 | 744篇 |
2005年 | 917篇 |
2004年 | 2041篇 |
2003年 | 1658篇 |
2002年 | 1314篇 |
2001年 | 888篇 |
2000年 | 421篇 |
1999年 | 670篇 |
1998年 | 639篇 |
1997年 | 770篇 |
1996年 | 527篇 |
1995年 | 396篇 |
1994年 | 679篇 |
1993年 | 691篇 |
1992年 | 641篇 |
1991年 | 582篇 |
1990年 | 636篇 |
1989年 | 465篇 |
1988年 | 448篇 |
1987年 | 441篇 |
1986年 | 539篇 |
1985年 | 640篇 |
1984年 | 611篇 |
1983年 | 528篇 |
1982年 | 704篇 |
1981年 | 751篇 |
1980年 | 811篇 |
1979年 | 1042篇 |
1978年 | 997篇 |
1977年 | 1006篇 |
1976年 | 909篇 |
1975年 | 870篇 |
1974年 | 595篇 |
1973年 | 938篇 |
1972年 | 1011篇 |
1971年 | 943篇 |
1970年 | 907篇 |
1969年 | 900篇 |
1968年 | 863篇 |
1967年 | 722篇 |
1966年 | 578篇 |
1965年 | 503篇 |
1964年 | 450篇 |
1963年 | 414篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
991.
正Published online:14 March 2014óScience China Press and Springer-Verlag Berlin Heidelberg 2014Erratum to:Chin.Sci.Bull.(2014)59(5–6):528–532DOI 10.1007/s11434-013-0060-1In the original publication of this paper,the first name and the last name of the first author has been documented 相似文献
992.
The purpose of the paper is to present a framework that enables action researchers to create quality action research projects within the organization development (OD) domain using the broad criteria of being rigorous, reflective and relevant and so contribute to the realm of practical knowing. What constitutes good quality action research within OD is a difficult question, given the broad range of approaches that operates in a wide variety of settings and with great diversity. It advances specific dimensions by which action researchers can create, review and assess quality in action research work. This integrative framework and criteria are practical tools to enable action researchers to create quality action research in OD. 相似文献
993.
Rike Wallbrecher Wouter P. R. Verdurmen Samuel Schmidt Petra H. Bovee-Geurts Felix Broecker Anika Reinhardt Toin H. van Kuppevelt Peter H. Seeberger Roland Brock 《Cellular and molecular life sciences : CMLS》2014,71(14):2717-2729
Binding to negatively charged heparan sulfates (HS) at the cell surface is considered the first step in the internalization of cationic cell-penetrating peptides (CPPs). However, little is known about the relation of the characteristics of the HS-CPP interaction such as affinity, stoichiometry, and clustering with uptake. In this study, we investigated a collection of mutants of a cyclic CPP derived from human lactoferrin with respect to HS binding and uptake. The thermodynamic parameters of HS binding were determined by isothermal titration calorimetry, clustering of HS was investigated by dynamic light scattering, and cellular uptake by flow cytometry and confocal microscopy. Whereas mutations of non-arginine amino acids that are conserved across lactoferrins of different mammalia only had a minor effect on uptake efficiency, changes in the number of arginine residues influenced the uptake significantly. In general, introduction of arginine residues and cyclization improved the HS affinity and the ability to cluster HS. In particular, there was a strong negative correlation between stoichiometry and uptake, indicating that crosslinking of HS is the driving force for the uptake of arginine-rich CPPs. Using glycan microarrays presenting a collection of synthetic HS, we show that a minimal chain length of HS is required for peptide binding. 相似文献
994.
鉴于构建流行病动力学模型、探索流行病传播规律对疫情防控具有十分重要的理论意义和实际应用价值,在已有的均匀混合模型基础上,针对个体接触关系异质化越发明显,且每个个体都处在不同的接触关系中,建立了兼顾个体状态与接触追踪的动态小世界网络模型。模拟了新冠病毒在社会中的传播过程。通过对比仿真结果,说明了所建模型的合理性。在此基础上,仿真计算了网络拓扑结构与接种免疫人数占比共同作用下对新冠病毒传播的影响,分析得到群体免疫临界值。说明所建传播模型合理,接种疫苗实现群体免疫可行。 相似文献
995.
Zhitao Xu X. G. Ming Wenyan Song Lina He Miao Li 《Systemic Practice and Action Research》2014,27(2):141-164
Quite often over the last decade, heavy equipment manufacturers are trying to improve their project management performance with the use of effective project management methods. However, the challenges encountered aren’t isolated problems and a systemic approach is required. This paper exemplifies how a systemic approach can be applied to heavy equipment manufacturing project (HEMP) management, through of a multifaceted vision. The findings present in the paper are based on a two-year case study in a metallurgic equipment manufacturing enterprise in China. Based on the analysis of HEMP management problems and the contributions on systemic approach application in project management, the paper enriches existing theory by: (1) interpreting the HEMP management system with the top-down disassembly method; (2) developing the collaborative project management approach with a systems view highlighting the project characteristics management and inter-departmental collaboration; (3) making suggestions for systemic approach application in project management. For practitioners and researchers, the findings are particularly meaningful for manufacturing project management and systemic approach application. 相似文献
996.
997.
998.
Understanding complex physical systems through the use of simulations often takes on a narrative character. That is, scientists using simulations seek an understanding of processes occurring in time by generating them from a dynamic model, thereby producing something like a historical narrative. This paper focuses on simulations of the Diels-Alder reaction, which is widely used in organic chemistry. It calls on several well-known works on historical narrative to draw out the ways in which use of these simulations mirrors aspects of narrative understanding: Gallie for “followability” and “contingency”; Mink for “synoptic judgment”; Ricoeur for “temporal dialectic”; and Hawthorn for a related dialectic of the “actual and the possible”. Through these reflections on narrative, the paper aims for a better grasp of the role that temporal development sometimes plays in understanding physical processes and of how considerations of possibility enhance that understanding. 相似文献
999.
Archive for History of Exact Sciences - Adolf Hurwitz’s estate contains a note from the early 1880s on the converse to Riemann’s proof of the functional equation for the zeta-function;... 相似文献
1000.
Yue Shi Guang Yang Jia Yu Lina Yu Ruth Westenbroek William A. Catterall Lisa Juntti-Berggren Per-Olof Berggren Shao-Nian Yang 《Cellular and molecular life sciences : CMLS》2014,71(7):1289-1303
Apolipoprotein CIII (ApoCIII) not only serves as an inhibitor of triglyceride hydrolysis but also participates in diabetes-related pathological events such as hyperactivation of voltage-gated Ca2+ (CaV) channels in the pancreatic β cell. However, nothing is known about the molecular mechanisms whereby ApoCIII hyperactivates β cell CaV channels. We now demonstrate that ApoCIII increased CaV1 channel open probability and density. ApoCIII enhanced whole-cell Ca2+ currents and the CaV1 channel blocker nimodipine completely abrogated this enhancement. The effect of ApoCIII was not influenced by individual inhibition of PKA, PKC, or Src. However, combined inhibition of PKA, PKC, and Src counteracted the effect of ApoCIII, similar results obtained by coinhibition of PKA and Src. Moreover, knockdown of β1 integrin or scavenger receptor class B type I (SR-BI) prevented ApoCIII from hyperactivating β cell CaV channels. These data reveal that ApoCIII hyperactivates β cell CaV1 channels through SR-BI/β1 integrin-dependent coactivation of PKA and Src. 相似文献