全文获取类型
收费全文 | 2623篇 |
免费 | 54篇 |
国内免费 | 11篇 |
专业分类
化学 | 1575篇 |
晶体学 | 17篇 |
力学 | 88篇 |
数学 | 594篇 |
物理学 | 414篇 |
出版年
2021年 | 31篇 |
2020年 | 23篇 |
2019年 | 30篇 |
2016年 | 42篇 |
2015年 | 54篇 |
2014年 | 42篇 |
2013年 | 107篇 |
2012年 | 85篇 |
2011年 | 101篇 |
2010年 | 58篇 |
2009年 | 55篇 |
2008年 | 99篇 |
2007年 | 75篇 |
2006年 | 63篇 |
2005年 | 56篇 |
2004年 | 50篇 |
2003年 | 37篇 |
2002年 | 51篇 |
2001年 | 26篇 |
2000年 | 41篇 |
1999年 | 45篇 |
1998年 | 32篇 |
1997年 | 38篇 |
1996年 | 29篇 |
1995年 | 38篇 |
1994年 | 26篇 |
1993年 | 28篇 |
1992年 | 36篇 |
1991年 | 23篇 |
1990年 | 22篇 |
1989年 | 21篇 |
1988年 | 32篇 |
1987年 | 33篇 |
1986年 | 28篇 |
1985年 | 47篇 |
1984年 | 34篇 |
1983年 | 24篇 |
1982年 | 29篇 |
1981年 | 34篇 |
1980年 | 39篇 |
1979年 | 36篇 |
1978年 | 24篇 |
1977年 | 43篇 |
1976年 | 32篇 |
1975年 | 25篇 |
1974年 | 21篇 |
1971年 | 20篇 |
1967年 | 18篇 |
1933年 | 20篇 |
1930年 | 21篇 |
排序方式: 共有2688条查询结果,搜索用时 31 毫秒
131.
132.
Lorenzo A. Picos‐Corrales Angel Licea‐Claveríe Karl‐Friedrich Arndt 《Journal of polymer science. Part A, Polymer chemistry》2012,50(20):4277-4287
A synthetic methodology is described for the preparation of core–shell nanogels by reversible addition‐fragmentation chain transfer. Well‐defined macro chain transfer agents (macro‐CTA's) were prepared in a first step using monomers that yield sensitive polymers. In the second step, a crosslinker alone or with the addition of a functionalized comonomer were used to form a crosslinked core. The ratio of crosslinker to macro‐CTA is crucial to yield nanogels. Furthermore, the polymerization time has an impact in the architecture of the nanomaterial obtained: it evolves from a core‐crosslinked star to a core–shell nanogel. Controlling the molecular weight of the macro‐CTA and the type of comonomer in the core forming step, core–shell nanogels with hydrodynamic diameters from 22 to 168 nm and a core that represents from 35 to 77% of the size, were prepared containing functional groups in the core which could be used as catalytic scaffolds. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012. 相似文献
133.
134.
135.
Comment on "Indispensable finite time corrections for Fokker-Planck equations from time series data"
Friedrich R Renner Ch Siefert M Peinke J 《Physical review letters》2002,89(14):149401; author reply 149402
136.
The proposed universality of small scale turbulence is investigated for a set of measurements in a cryogenic free jet with a variation of the Reynolds number (Re) from 8500 to 10(6) (max(R(lambda) approximately 1200). The traditional analysis of the statistics of velocity increments by means of structure functions or probability density functions is replaced by a new method which is based on the theory of Markov processes. It gives access to a more complete characterization by means of joint probabilities of finding velocity increments at several scales. Based on this more comprehensive method, our results are very far from a possible universal state, even for R(lambda) above 1000. 相似文献
137.
Seelig B Keiper S Stuhlmann F Jäschke A 《Angewandte Chemie (International ed. in English)》2000,39(24):4576-4579
138.
Real valued M-estimators
in a statistical model 1 with observations
are replaced by
-valued M-estimators
in a new model with observations
where
are regressors,
is a structural parameter and
a structural function of the new model. Sufficient conditions for the consistency of
are derived, motivated by the sufficiency conditions for the simpler parent estimator
The result is a general method of consistent estimation in a class of nonlinear (pseudolinear) statistical problems. If F
has a natural exponential density ex–b( x ) then our pseudolinear model with u = (g o )–1 reduces to the well known generalized linear model, provided () = db()/d and g is the so-called link function of the generalized linear model. General results are illustrated for special pairs and leading to some classical M-estimators of mathematical statistics, as well as to a new class of generalized -quantile estimators. 相似文献
139.
Friedrich Wehrung 《Proceedings of the American Mathematical Society》1999,127(2):363-370
The Congruence Lattice Problem asks whether every algebraic distributive lattice is isomorphic to the congruence lattice of a lattice. It was hoped that a positive solution would follow from E. T. Schmidt's construction or from the approach of P. Pudlák, M. Tischendorf, and J. Tuma. In a previous paper, we constructed a distributive algebraic lattice with compact elements that cannot be obtained by Schmidt's construction. In this paper, we show that the same lattice cannot be obtained using the Pudlák, Tischendorf, Tuma approach.
The basic idea is that every congruence lattice arising from either method satisfies the Uniform Refinement Property, that is not satisfied by our example. This yields, in turn, corresponding negative results about congruence lattices of sectionally complemented lattices and two-sided ideals of von Neumann regular rings.
140.
This paper describes some of the aspects necessary for the design and use of tube chain conveyors. It is based on the reports of experienced experts and recent tube chain conveyor experimental results. The aim of the research work is the formulation of general technical regulations for tube chain conveyors. Theoretical models were developed, which allow the calculation of the motion resistances in all parts of the conveyor by the use of empirical extracted correction factors. Specially designed measurement equipment enabled the measurement of the important chain tractive force from the closed tube system. The measurements show the influence of the major operational parameters and the bulk solid properties. 相似文献