全文获取类型
收费全文 | 2375篇 |
免费 | 176篇 |
国内免费 | 14篇 |
专业分类
化学 | 1732篇 |
晶体学 | 6篇 |
力学 | 66篇 |
数学 | 419篇 |
物理学 | 342篇 |
出版年
2024年 | 4篇 |
2023年 | 48篇 |
2022年 | 44篇 |
2021年 | 61篇 |
2020年 | 123篇 |
2019年 | 137篇 |
2018年 | 61篇 |
2017年 | 38篇 |
2016年 | 138篇 |
2015年 | 127篇 |
2014年 | 117篇 |
2013年 | 152篇 |
2012年 | 225篇 |
2011年 | 234篇 |
2010年 | 120篇 |
2009年 | 83篇 |
2008年 | 152篇 |
2007年 | 118篇 |
2006年 | 96篇 |
2005年 | 121篇 |
2004年 | 73篇 |
2003年 | 60篇 |
2002年 | 30篇 |
2001年 | 22篇 |
2000年 | 20篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 5篇 |
1991年 | 4篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1975年 | 6篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1963年 | 5篇 |
1956年 | 3篇 |
1905年 | 2篇 |
1904年 | 2篇 |
排序方式: 共有2565条查询结果,搜索用时 0 毫秒
31.
Alberto García‐Peas Yu Wang Alexandra Muoz‐Bonilla Marta Fernndez‐García Florian J. Stadler 《Journal of Polymer Science.Polymer Physics》2019,57(20):1386-1393
The effect of the molecular weight on the lower critical solution temperature (LCST) has been discussed extensively, where LCST increased with molar mass, decreased or kept constant, which leads to confusion. This work is focused on the preparation of poly(N‐isopropyl acrylamide) homopolymers, obtained in a wide molecular weights range. The LCST behavior is analyzed by calorimetry and rheology, and a deep study of molecular features is carried out for a better knowledge of the influence of various parameters involved on LCST. Finally, the molecular weight trend is observed, and its influence on LCST is compared with the effect of other parameters as polymer concentration in water, end‐group effect, and tacticity. It is observed that other parameters such tacticity and end‐group effect will affect the LCST behavior over molecular weight, if this one is not high enough. Furthermore, the study of the LCST ranges will be a useful tool for analyzing the molecular weight trends. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1386–1393 相似文献
32.
The aim of this work is to derive an accurate model of two-dimensional switched control heating system from data generated by a Finite Element solver. The nonintrusive approach should be able to capture both temperature fields, dynamics and the underlying switching control rule. To achieve this goal, the algorithm proposed in this paper will make use of three main ingredients: proper orthogonal decomposition (POD), dynamic mode decomposition (DMD) and artificial neural networks (ANN). Some numerical results will be presented and compared to the high-fidelity numerical solutions to demonstrate the capability of the method to reproduce the dynamics. 相似文献
33.
34.
Summary We provide a general asymptotic formula which permits applications to sums like <InlineEquation ID=IE"1"><EquationSource Format="TEX"><![CDATA[<InlineEquation
ID=IE"2"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"3"><EquationSource Format="TEX"><![CDATA[<InlineEquation
ID=IE"4"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"5"><EquationSource Format="TEX"><![CDATA[<InlineEquation
ID=IE"6"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"7"><EquationSource Format="TEX"><![CDATA[<InlineEquation
ID=IE"8"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"9"><EquationSource Format="TEX"><![CDATA[$]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>$]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>
\sum_{x< n\le x+y} \big(d(n)\big)^2, \quad \sum_{x< n\le x+y} d(n^3),\quad \sum_{x< n\le x+y}\big(r(n)\big)^2, \quad \sum_{x<
n\le x+y}r(n^3), $$ where $d(n)$ and $r(n)$ are the usual arithmetic functions (number of divisors, sums of two squares),
and $y$ is small compared to~$x$. 相似文献
35.
If the Riemann–Christoffel tensor associated with a field of class of positive definite symmetric matrices of order three vanishes in a connected and simply connected open subset , then this field is the metric tensor field associated with a deformation of class of the set , uniquely determined up to isometries of . We establish here that the mapping defined in this fashion is continuous, for ad hoc metrizable topologies. To cite this article: P.G. Ciarlet, F. Laurent, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 489–493. 相似文献
36.
An interior point method for monotone linear complementarity problems acting in a wide neighborhood of the central path is
presented. The method has
-iteration complexity and is superlinearly convergent even when the problem does not possess a strictly complementary solution.
Mathematics Subject Classification (2000): 49M15, 65K05, 90C33
Work supported by the National Science Foundation under Grant No. 0139701.
An erratum to this article is available at. 相似文献
37.
Flight gate scheduling with respect to a reference schedule 总被引:1,自引:0,他引:1
Ulrich?Dorndorf Florian?Jaehn Erwin?PeschEmail author 《Annals of Operations Research》2012,194(1):177-187
This paper considers the problem of assigning flights to airport gates. We examine the general case in which an aircraft serving
a flight may be assigned to different gates for arrival and departure processing and for optional intermediate parking. Restrictions
to this assignment include gate closures and shadow restrictions, i.e., the situation where certain gate assignments may cause
blocking of neighboring gates. The objectives include maximization of the total assignment preference score, a minimal number
of unassigned flights during overload periods, minimization of the number of tows, maximization of a robustness measure as
well as a minimal deviation from a given reference schedule. We show that in case of a one period time horizon this objective
can easily be integrated into our existing model based on the Clique Partitioning Problem. Furthermore we present a heuristic
algorithm to solve the problem for multiple periods. 相似文献
38.
Ayalvadi Ganesh Sarah Lilienthal D. Manjunath Alexandre Proutiere Florian Simatos 《Queueing Systems》2012,71(3):321-345
In this paper, we analyze the performance of random load resampling and migration strategies in parallel server systems. Clients initially attach themselves to an arbitrary server, but may switch servers independently at random instants of time in an attempt to improve their service rate. This approach to load balancing contrasts with traditional approaches where clients make smart server selections upon arrival (e.g., Join-the-Shortest-Queue policy and variants thereof). Load resampling is particularly relevant in scenarios where clients cannot predict the load of a server before being actually attached to it. An important example is in wireless spectrum sharing where clients try to share a set of frequency bands in a distributed manner. We first analyze the natural Random Local Search (RLS) strategy. Under this strategy, after sampling a new server randomly, clients only switch to it if their service rate is improved. In closed systems, where the client population is fixed, we derive tight estimates of the time it takes under RLS strategy to balance the load across servers. We then study open systems where clients arrive according to a random process and leave the system upon service completion. In this scenario, we analyze how client migrations within the system interact with the system dynamics induced by client arrivals and departures. We compare the load-aware RLS strategy to a load-oblivious strategy in which clients just randomly switch server without accounting for the server loads. Surprisingly, we show that both load-oblivious and load-aware strategies stabilize the system whenever this is at all possible. We use large-system asymptotics to characterize system performance, and augment this with simulations, which suggest that the average client sojourn time under the load-oblivious strategy is not considerably reduced when clients apply smarter load-aware strategies. 相似文献
39.
Florian A. Potra 《Mathematical Programming》2001,91(1):99-115
Sufficient conditions are given for the Q-superlinear convergence of the iterates produced by primal-dual interior-point methods
for linear complementarity problems. It is shown that those conditions are satisfied by several well known interior-point
methods. In particular it is shown that the iteration sequences produced by the simplified predictor–corrector method of Gonzaga
and Tapia, the simplified largest step method of Gonzaga and Bonnans, the LPF+ algorithm of Wright, the higher order methods
of Wright and Zhang, Potra and Sheng, and Stoer, Wechs and Mizuno are Q-superlinearly convergent.
Received: February 9, 2000 / Accepted: February 20, 2001?Published online May 3, 2001 相似文献
40.
Florian Enescu 《Proceedings of the American Mathematical Society》2003,131(11):3379-3386
The notion of stability of the highest local cohomology module with respect to the Frobenius functor originates in the work of R. Hartshorne and R. Speiser. R. Fedder and K.-i. Watanabe examined this concept for isolated singularities by relating it to -rationality. The purpose of this note is to study what happens in the case of non-isolated singularities and to show how this stability concept encapsulates a few of the subtleties of tight closure theory. Our study can be seen as a generalization of the work by Fedder and Watanabe. We introduce two new ring invariants, the -stability number and the set of -stable primes. We associate to every ideal generated by a system of parameters and an ideal of multipliers denoted and obtain a family of ideals . The set is independent of and consists of finitely many prime ideals. It also equals prime ideal such that is -stable. The maximal height of such primes defines the -stability number.