全文获取类型
收费全文 | 368084篇 |
免费 | 4625篇 |
国内免费 | 2040篇 |
专业分类
化学 | 178888篇 |
晶体学 | 5519篇 |
力学 | 19343篇 |
综合类 | 97篇 |
数学 | 54123篇 |
物理学 | 116779篇 |
出版年
2020年 | 2585篇 |
2019年 | 2751篇 |
2018年 | 11517篇 |
2017年 | 12242篇 |
2016年 | 8759篇 |
2015年 | 4008篇 |
2014年 | 5071篇 |
2013年 | 11699篇 |
2012年 | 13090篇 |
2011年 | 22262篇 |
2010年 | 14347篇 |
2009年 | 14170篇 |
2008年 | 19644篇 |
2007年 | 22936篇 |
2006年 | 9718篇 |
2005年 | 14460篇 |
2004年 | 10844篇 |
2003年 | 10205篇 |
2002年 | 8245篇 |
2001年 | 7729篇 |
2000年 | 6186篇 |
1999年 | 4669篇 |
1998年 | 4152篇 |
1997年 | 4047篇 |
1996年 | 3962篇 |
1995年 | 3643篇 |
1994年 | 3761篇 |
1993年 | 3420篇 |
1992年 | 3857篇 |
1991年 | 3876篇 |
1990年 | 3812篇 |
1989年 | 3644篇 |
1988年 | 3744篇 |
1987年 | 3618篇 |
1986年 | 3418篇 |
1985年 | 4506篇 |
1984年 | 4757篇 |
1983年 | 3992篇 |
1982年 | 4115篇 |
1981年 | 4035篇 |
1980年 | 4003篇 |
1979年 | 3985篇 |
1978年 | 4301篇 |
1977年 | 4149篇 |
1976年 | 4233篇 |
1975年 | 3901篇 |
1974年 | 3944篇 |
1973年 | 4135篇 |
1972年 | 2886篇 |
1971年 | 2402篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
A modernized conception of hierarchical structure of reality is proposed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 3–6, December, 1980. 相似文献
952.
After a discussion of a space of test functions and the corresponding space of distributions, a family of Banach spaces (B, ∥ ∥B) in standard situation is described. These are spaces of distributions having a pointwise module structure and also a module structure with respect to convolution. The main results concern relations between the different spaces associated to B established by means of well-known methods from the theory of Banach modules, among them B0 and , the closure of the test functions in B and the weak relative completion of B, respectively. The latter is shown to be always a dual Banach space. The main diagram, given in Theorem 4.7, gives full information concerning inclusions between these spaces, showing also a complete symmetry. A great number of corresponding formulas is established. How they can be applied is indicated by selected examples, in particular by certain Segal algebras and the Ap-algebras of Herz. Various further applications are to be given elsewhere. 相似文献
953.
954.
Pál Sohár Gábor Bernáth Géza Stájer Angela E. Szabo 《Magnetic resonance in chemistry : MRC》1989,27(9):872-876
Pentacyclic isoxazolines were obtained by the cycloaddition of benzonitrile oxide to norbornene-azetidinone-fused 3,1-oxazines. The constitutions of two of the isomers obtained, and the configurations and conformations of all products, were determined by means of 1H and 13C NMR spectroscopy and DNOE experiments. 相似文献
955.
956.
Roger M. Hill 《The Journal of the Operational Research Society》1989,40(11):983-992
The context is that of a retail chain where stock is purchased into a central warehouse from which branch stocks are replenished. This paper considers possible methods of allocating limited warehouse stock to branches, and uses simulation to quantify the resulting benefits. 相似文献
957.
958.
959.
Population balance equations combined with a three-dimensional two-fluid model are employed to predict subcooled boiling flow at low pressure in a vertical annular channel. The MUSIG (MUltiple-SIze-Group) model implemented in the computer code CFX4.4 is further developed to accommodate the wall nucleation at the heated wall and condensation in the subcooled boiling regime. Comparison of model predictions against local measurements is made for the void fraction, bubble Sauter mean diameter and gas and liquid velocities covering a range of different mass and heat fluxes and inlet subcooling temperatures. Additional comparison using empirical relationships for the active nucelation site density and local bubble diameter is also investigated. Good agreement is achieved with the local radial void fraction, bubble Sauter diameter and liquid velocity profiles against measurements. However, significant weakness of the model is evidenced in the prediction of the vapour velocity. Work is in progress to circumvent the deficiency through the consideration of additional momentum equations or developing an algebraic slip model to account for bubble separation. 相似文献
960.
The possibilities of controlling the laser beam properties by a deformable mirror introduced into the laser optical cavity
were studied theoretically and experimentally. The experiments were performed under conditions of an industrial high power
transverse flow cw CO2 laser operating with a stable resonator of a folded configuration. A deformable bimorph mirror of a surface profile controlled
by the voltage applied to the mirror electrodes is implemented to the laser system as a back cavity mirror or as a one of
the inner folding mirrors. The near-and far-field characteristics of the laser beam versus the resonator configuration controlled
by the changes of the focal length of the deformable mirror are discussed in the paper. The analysis reveals that the resonator
with an inner deformable mirror is much more sensitive to the mirror curvature variations than the resonator in which the
deformable mirror is used as a back cavity mirror. The presented results show that dynamic and controllable changes in the
resonator properties result in the controlled modification and optimisation of the laser output power and spatial parameters
of the laser radiation. 相似文献