全文获取类型
收费全文 | 552篇 |
免费 | 15篇 |
国内免费 | 6篇 |
专业分类
化学 | 378篇 |
晶体学 | 4篇 |
力学 | 10篇 |
数学 | 98篇 |
物理学 | 38篇 |
无线电 | 45篇 |
出版年
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 30篇 |
2012年 | 32篇 |
2011年 | 36篇 |
2010年 | 23篇 |
2009年 | 9篇 |
2008年 | 33篇 |
2007年 | 40篇 |
2006年 | 30篇 |
2005年 | 46篇 |
2004年 | 38篇 |
2003年 | 22篇 |
2002年 | 16篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1982年 | 5篇 |
1980年 | 11篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1968年 | 3篇 |
1967年 | 1篇 |
排序方式: 共有573条查询结果,搜索用时 318 毫秒
71.
John R. Quist Pamela J. Gordon 《今日电子》2006,(7):47-47
很不幸,我们在生活中经常会碰到这样的场景:在电子产品制造公司里,当人们第一次提出要贯彻从产品中消除有害物质的规定时,却无法说服管理层下决心拿出公司的资源来做这件事。相反,他们倒是听到了“这件事与我无关”的几个不同说法。 相似文献
72.
In this paper we consider generalized convexity and concavity properties of the optimal value functionf
* for the general parametric optimization problemP(ε) of the form min
x
f(x, ε) s.t.x∈R(ε). Many results on convexity and concavity characterizations off
* were presented by the authors in a previous paper. Such properties off
* and the solution set mapS
* form an important part of the theoretical basis for sensitivity, stability and parametric analysis in mathematical optimization.
We give sufficient conditions for several types of generalized convexity and concavity off
*, in terms of respective generalized convexity and concavity assumptions onf and convexity and concavity assumptions on the feasible region point-to-set mapR. Specializations of these results to the parametric inequality-equality constrained nonlinear programming problem are provided.
Research supported by Grant ECS-8619859, National Science Foundation and Contract N00014-86-K-0052, Office of Naval Research. 相似文献
73.
We construct interpolating Balschke products whose radial cluster sets at a given point of the unit circle can be prescribed
to be one of the following: the closed unit disk; an arbitrary closed arc on the unit circle; an arbitrary interval of the
form [x, y], wherexy ≠ 0 and −1≤1x≤y≤1. We also show that there does not exist an interpolating Blaschke product having [0,y] or [x, 0] as a radial cluster set. On the other hand, there do exist finite products of interpolating Blaschke products that have
[0, 1] as a radial cluster set.
Research supported by the RIP-program Oberwolfach, 2002/2003. 相似文献
74.
In this paper we explore two teachers' views on the role(s) of parents, the local community and children's home lives in the learning of mathematics in primary school. We use Moll and Greenberg's concept of ‘funds of knowledge’ and apply it to the case studies of two teachers working in the UK context. Issues of teachers' professional experience, ethnicity, class and gender emerge as significant in examining similarities and differences in the teachers' beliefs, understandings and practices in the area of linking home and school. We end with a discussion of some implications for teacher education and professional development. 相似文献
75.
Previous research has shown that a region of the midbrain, the periaqueductal gray matter (PAG), is critical for vocalization. In this review, we describe the results of previous investigations in which we sought to find out how PAG neurons integrate the activity and precise timing of respiratory, laryngeal, and oral muscle activity for natural-sounding vocalization using the technique of excitatory amino acid microinjections in cats. In these studies, all surgical procedures were carried out under deep anaesthesia. In the precollicular decerebrate cat two general types of vocalization, classified as voiced and unvoiced, could be evoked by exciting neurons in the lateral part of the intermediate part of the PAG. The patterns of evoked electromyographic activity were strikingly similar to previously reported patterns of human muscle activity. Coordinated patterns of activity were evoked with just-threshold excitation leading to the conclusion that patterned muscle activity corresponding to the major categories of voiced and voiceless sound production are represented in the PAG. In a parallel series of human and animal experiments, we also determined that the speech and vocalization respiratory patterns are integrated and coordinated with afferent signals related to lung volume. These data have led to the proposal of a new hypothesis for the neural control of vocalization: that the PAG is a crucial brain site for mammalian voice production, not only in the production of emotional or involuntary sounds, but also as a generator of specific respiratory and laryngeal motor patterns essential for human speech and song 相似文献
76.
Realini M Colombo C Sansonetti A Rampazzi L Colombini MP Bonaduce I Zanardini E Abbruscato P 《Annali di chimica》2005,95(3-4):217-226
The analytical studies carried out during two different diagnostic surveys, respectively in 1983 and 2003, offered the opportunity to control decay phenomena development on stones facing Certosa of Pavia (Italy). Calcium oxalate films and red stains, present on Carrara marble surface, have been particularly focused; these are the only decay phenomena which apparently have remained unchanged during a period of twenty years. More sensitive and in-depth analytical studies (FTIR equipped with diamond cell, GC-MS, SEM-EDS and optical microscopy) achieved a better knowledge about their composition. Results allowed a critical evaluation of the role of oxalate films on the external marble surface and to suggest new hypotheses about the formation of red stains. 相似文献
77.
A Blaschke product B with zero-sequence (an) is called almostinterpolating if the inequality lim infn(1 |an|2)|B'(an)| 相似文献
78.
Communication in Crisis: Theory, Curricula, and Power 总被引:1,自引:0,他引:1
Pamela J. Shoemaker 《The Journal of communication》1993,43(4):146-153
79.
80.
Hunt CE Pasetto P Ansell RJ Haupt K 《Chemical communications (Cambridge, England)》2006,(16):1754-1756
The first pseudo-immunoassay which employs a molecularly imprinted receptor and a fluorescent probe, and quantifies the bound analyte directly using the fluorescence anisotropy of the polymer-probe-analyte suspension, is described. 相似文献