全文获取类型
收费全文 | 4406篇 |
免费 | 158篇 |
国内免费 | 16篇 |
专业分类
化学 | 3006篇 |
晶体学 | 9篇 |
力学 | 74篇 |
数学 | 621篇 |
物理学 | 870篇 |
出版年
2023年 | 34篇 |
2022年 | 39篇 |
2021年 | 62篇 |
2020年 | 66篇 |
2019年 | 87篇 |
2018年 | 49篇 |
2017年 | 39篇 |
2016年 | 113篇 |
2015年 | 130篇 |
2014年 | 132篇 |
2013年 | 210篇 |
2012年 | 300篇 |
2011年 | 328篇 |
2010年 | 176篇 |
2009年 | 168篇 |
2008年 | 218篇 |
2007年 | 256篇 |
2006年 | 257篇 |
2005年 | 223篇 |
2004年 | 218篇 |
2003年 | 176篇 |
2002年 | 153篇 |
2001年 | 94篇 |
2000年 | 68篇 |
1999年 | 53篇 |
1998年 | 48篇 |
1997年 | 49篇 |
1996年 | 53篇 |
1995年 | 60篇 |
1994年 | 47篇 |
1993年 | 37篇 |
1992年 | 39篇 |
1991年 | 36篇 |
1990年 | 34篇 |
1989年 | 30篇 |
1988年 | 20篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1979年 | 37篇 |
1978年 | 36篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1974年 | 18篇 |
1973年 | 26篇 |
1969年 | 17篇 |
排序方式: 共有4580条查询结果,搜索用时 15 毫秒
101.
In Baak et al. (J Math Anal Appl 314(1):150–161, 2006) the authors considered the functional equation where \(d,\ell \in \mathbb {N}\), \(1<\ell <d/2\) and \(r\in \mathbb {Q}{\setminus }\{0\}\). The authors determined all odd solutions \(f:X\rightarrow Y\) for vector spaces X, Y over \(\mathbb {Q}\). In Oubbi (Can Math Bull 60:173–183, 2017) the author considered the same equation but now for arbitrary real \(r\not =0\) and real vector spaces X, Y. Generalizing similar results from (J Math Anal Appl 314(1):150–161, 2006) he additionally investigates certain stability questions for the equation above, but as for that equation itself for odd approximate solutions only. The present paper deals with the general solution of the equation and the corresponding stability inequality. In particular it is shown that under certain circumstances non-odd solutions of the equation exist.
相似文献
$$\begin{aligned} r f\left( \frac{1}{r}\,\sum _{j=1}^{d}x_j\right)+ & {} \sum _{i(j)\in \{0,1\} \atop \sum _{1\le j\le d} i(j)=\ell }r f\left( \frac{1}{r}\,\sum _{j=1}^d (-1)^{i(j)}x_j\right) \\= & {} \left( {d-1\atopwithdelims ()\ell }-{d-1\atopwithdelims ()\ell -1} +1\right) \sum _{j=1}^{d} f(x_j) \end{aligned}$$
102.
Adriano Almeida Gonçalves Siqueira Rodrigo Nicoletti Nicklas Norrick Kátia Lucchesi Cavalca Helio Fiori de Castro Jens Bauer Fadi Dohnal 《Journal of sound and vibration》2012,331(10):2220-2232
Linear parameter varying (LPV) control is a model-based control technique that takes into account time-varying parameters of the plant. In the case of rotating systems supported by lubricated bearings, the dynamic characteristics of the bearings change in time as a function of the rotating speed. Hence, LPV control can tackle the problem of run-up and run-down operational conditions when dynamic characteristics of the rotating system change significantly in time due to the bearings and high vibration levels occur. In this work, the LPV control design for a flexible shaft supported by plain journal bearings is presented. The model used in the LPV control design is updated from unbalance response experimental results and dynamic coefficients for the entire range of rotating speeds are obtained by numerical optimization. Experimental implementation of the designed LPV control resulted in strong reduction of vibration amplitudes when crossing the critical speed, without affecting system behavior in sub- or super-critical speeds. 相似文献
103.
We provide a general procedure for characterizing radical-like functions of skew polynomial and skew Laurent polynomial rings under grading hypotheses. In particular, we are able to completely characterize the Wedderburn and Levitzki radicals of skew polynomial and skew Laurent polynomial rings in terms of ideals in the coefficient ring. We also introduce the T-nilpotent radideals, and perform similar characterizations. 相似文献
104.
We argue that the starting point of Kaluzas idea of unifying electrodynamics and gravity was the analogy between gravitation and electromagnetism which was pointed out by Einstein and Thirring. It seems that Kaluzas attention was turned to this point by the three papers on the Lense–Thirring effect and the analogy between gravitation and electromagnetism which were published a short time before Kaluzas paper was submitted. We provide here also an English translation of the third of these papers (Phys. Zeits. 19: 204, 1918). 相似文献
105.
Bearden IG Beavis D Besliu C Blyakhman Y Budick B Bøggild H Chasman C Christensen CH Christiansen P Cibor J Debbe R Enger E Gaardhøje JJ Germinario M Hagel K Hansen O Holm A Holme AK Ito H Jakobsen E Jipa A Jundt F Jørdre JI Jørgensen CE Karabowicz R Keutgen T Kim EJ Kozik T Larsen TM Lee JH Lee YK Løvhøiden G Majka Z Makeev A McBreen B Mikelsen M Murray M Natowitz J Nielsen BS Norris J Olchanski K Olness J Ouerdane D Płaneta R Rami F Ristea C Röhrich D Samset BH Sandberg D Sanders SJ 《Physical review letters》2003,90(10):102301
We present ratios of the numbers of charged antihadrons to hadrons (pions, kaons, and protons) in Au+Au collisions at sqrt[s(NN)]=200 GeV as a function of rapidity in the range y=0-3. While the ratios at midrapidity are approaching unity, the K(-)/K(+) and p;/p ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from mu(B) approximately 130 MeV at y=3 to mu(B) approximately 25 MeV at y=0. 相似文献
106.
107.
108.
Investigating the associativity equation for formal power series in two variables we show that the transcendental associative formal power series are of order one or two and that they can be represented by an invertible formal power series in one variable. We also discuss the convergence of associative formal power series. 相似文献
109.
A full-phase measurement of low-energy femtosecond UV pulses is presented. The method relies on phase retrieval of measured sonogram traces and is greatly simplified by a two-dimensional shaper-assisted cross correlation setup. As all required pulses are generated by the pulse shaper, the method is free of external references and additional tunable filter setups. 相似文献
110.
We consider a stochastic control problem over an infinite horizon where the state process is influenced by an unobservable
environment process. In particular, the Hidden-Markov-model and the Bayesian model are included. This model under partial
information is transformed into an equivalent one with complete information by using the well-known filter technique. In particular,
the optimal controls and the value functions of the original and the transformed problem are the same. An explicit representation
of the filter process which is a piecewise-deterministic process, is also given. Then we propose two solution techniques for
the transformed model. First, a generalized verification technique (with a generalized Hamilton–Jacobi–Bellman equation) is
formulated where the strict differentiability of the value function is weaken to local Lipschitz continuity. Second, we present
a discrete-time Markovian decision model by which we are able to compute an optimal control of our given problem. In this
context we are also able to state a general existence result for optimal controls. The power of both solution techniques is
finally demonstrated for a parallel queueing model with unknown service rates. In particular, the filter process is discussed
in detail, the value function is explicitly computed and the optimal control is completely characterized in the symmetric
case. 相似文献