全文获取类型
收费全文 | 2718篇 |
免费 | 269篇 |
国内免费 | 89篇 |
专业分类
化学 | 865篇 |
力学 | 173篇 |
综合类 | 98篇 |
数学 | 1250篇 |
物理学 | 690篇 |
出版年
2024年 | 11篇 |
2023年 | 29篇 |
2022年 | 135篇 |
2021年 | 114篇 |
2020年 | 74篇 |
2019年 | 69篇 |
2018年 | 73篇 |
2017年 | 145篇 |
2016年 | 151篇 |
2015年 | 92篇 |
2014年 | 203篇 |
2013年 | 160篇 |
2012年 | 176篇 |
2011年 | 175篇 |
2010年 | 136篇 |
2009年 | 135篇 |
2008年 | 141篇 |
2007年 | 130篇 |
2006年 | 132篇 |
2005年 | 145篇 |
2004年 | 113篇 |
2003年 | 68篇 |
2002年 | 57篇 |
2001年 | 48篇 |
2000年 | 42篇 |
1999年 | 39篇 |
1998年 | 44篇 |
1997年 | 33篇 |
1996年 | 26篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 21篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有3076条查询结果,搜索用时 31 毫秒
991.
Olufemi O. Oguntade 《Fuzzy Sets and Systems》1981,6(2):119-143
A philosophical formalism of a new methodological aspect of humanistic systems design and evaluation is given. A requisite concept of context-dependency is highlighted, and some approaches to fuzzy sets and linguistics subsequently extended. It is consequently shown that a mathematical theory of pragmatic fuzzy subsets is not only conceptually possible but practically implementable in man-machine studies as well. Thus, the important context-dependent implication of the subjective nature of Zadeh's theory of fuzzy sets can be better exploited.As a pragmatic theory, the approach here is a seeming connection between pragmatism and ontology, concepts that are traditionally diametrically opposed to each other. The attitude adopted has been the equation of pragmatism and psychophysical measurements of ontological objects (noumena). Pragmatism is tacitly defined as a form of empiricism whereby linguistic constructs (i.e., linguistic-variable denotions) that represent any aspect(s) of a humanistic system are nothing more than an operational procedure used to achieve psychophysical measurements of the aspect(s). In this fashion, pragmatism would enable the contents of assertions, which are made through declarative propositions, about humanistic systems to be deciphered within relevant contexts. For pragmatism, direct sense experience provides both the meaning and the criterion of reality judgements. The context-dependent nature of the physical reality of ontological entities is, therefore, better understood pragmatically vis-a-vis the appropriate evaluative criteria and interpretative conventions.By emphasizing the distinction between a fuzzy system (naturally fuzzified) and a fuzzified mathematical structure (meta-mathematically fuzzified), the use of the standard fuzzy topologies is justified although it is conceptually possible to develop a yet more general topology or perhaps an alternative one especially in the case of a meta-mathematically fuzzified structure. However, for the express purpose of machine implementation, a naturally fuzzified system, such as a (complex) humanistic system, is more amenable to an initial test of the philosophy of pragmatic fuzzy subsets. Consequently, the fuzzy topology and spaces employed are intended to be devoid of extensive generalities, in this instance. 相似文献
992.
A microcomputer-controlled automatic potentiometric titrator withP controlled intelligent auto-sampler has been built for serial analysis. Controlling and evaluating programs have also been written. In order to use the most powerful evaluating method, a comparison was made between the methods. The data of the titration curves were obtained by the implicit relation characterizing the curve. The different evaluating methods were tested by using these data. The effects of random errors stemming from measurements were also investigated. The methods used were: two point differentiating formula, differentiation of interpolating and smoothing spline functions, the Gran method, and implicit regression with the Gauss-Newton-Marquardt method. Regression is outstanding among the methods, but it needs much more computing time compared with others. The second-best method is the differentiation with smoothing spline function with end point determination based on finding the sign reversal of the second derivative. This method is much faster than regression. 相似文献
993.
994.
995.
996.
Philippe Nain 《Statistical Inference for Stochastic Processes》2002,5(3):307-320
The impact of bursty traffic on queues is investigated in this paper. We consider a discrete-time single server queue with
an infinite storage room, that releases customers at the constant rate of c customers/slot. The queue is fed by an M/G/∞ process. The M/G/∞ process can be seen as a process resulting from the superposition
of infinitely many ‘sessions’: sessions become active according to a Poisson process; a station stays active for a random
time, with probability distribution G, after which it becomes inactive. The number of customers entering the queue in the time-interval [t, t + 1) is then defined as the number of active sessions at time t (t = 0,1, ...) or, equivalently, as the number of busy servers at time t in an M/G/∞ queue, thereby explaining the terminology. The M/G/∞ process enjoys several attractive features: First, it can
display various forms of dependencies, the extent of which being governed by the service time distribution G. The heavier the tail of G, the more bursty the M/G/∞ process. Second, this process arises naturally in teletraffic as the limiting case for the aggregation
of on/off sources [27]. Third, it has been shown to be a good model for various types of network traffic, including telnet/ftp
connections [37] and variable-bit-rate (VBR) video traffic [24]. Last but not least, it is amenable to queueing analysis due
to its very strong structural properties. In this paper, we compute an asymptotic lower bound for the tail distribution of
the queue length. This bound suggests that the queueing delays will dramatically increase as the burstiness of the M/G/∞ input
process increases. More specifically, if the tail of G is heavy, implying a bursty input process, then the tail of the queue length will also be heavy. This result is in sharp
contrast with the exponential decay rate of the tail distribution of the queue length in presence of ‘non-bursty’ traffic
(e.g. Poisson-like traffic).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
997.
线性加权评价与聚类分析理论及应用 总被引:1,自引:0,他引:1
针对当前大学生综合素质评价方法的弊端进行简单的探讨,提出了线性加权法和聚类分析法两种评价方法,并通过实例说明这两种方法的可行性,得到的结果也符合实际情况. 相似文献
998.
目的建立了电感耦合等离子体质谱法(ICP-MS)测定不同批次山绿茶降压胶囊内容物中无机元素的含量,从无机元素角度探讨山绿茶降压胶囊的质量控制方法。方法采用微波消解处理山绿茶降压胶囊内容物样品,用ICP-MS对样品中多种无机元素进行全定量测定。结果测定10个不同批次山绿茶降压胶囊内容物的22种无机元素,其中K、Mg、Ca、Zn等元素含量较高,且与药效相关性较强,Cu、As、Hg、Pb、Cd全部符合标准要求。结论本法灵敏度高,专属性好,适用于山绿茶降压胶囊内容物中无机元素测定,为山绿茶降压胶囊内容物重金属含有量及用药提供依据。 相似文献
999.
1000.
随着现代武器装备复杂化、综合化、智能化程度的不断提高,传统的故障诊断技术难以适应新的需求。为了满足信息化战争对武器装备作战效能和快捷、精准、持续保障的要求,20世纪90年代中期,PHM(故障预测与健康管理)技术应运而生。从发展概况、应用成效、PHM验证评价、典型案例分析以及发展规划5个方面总结了国外PHM技术发展的应用成效;并对国内PHM技术的基础理论、工程技术与应用方面的发展状况进行了总结;通过对比国内外PHM技术的发展应用现状,总结分析了目前国内PHM技术发展现状与国外先进水平之间的差距以及未来发展的借鉴启示。 相似文献