全文获取类型
收费全文 | 590124篇 |
免费 | 5149篇 |
国内免费 | 1826篇 |
专业分类
化学 | 315311篇 |
晶体学 | 8950篇 |
力学 | 26288篇 |
综合类 | 17篇 |
数学 | 67980篇 |
物理学 | 178553篇 |
出版年
2020年 | 4938篇 |
2019年 | 5483篇 |
2018年 | 7200篇 |
2017年 | 7090篇 |
2016年 | 10523篇 |
2015年 | 6458篇 |
2014年 | 10007篇 |
2013年 | 25771篇 |
2012年 | 19436篇 |
2011年 | 23658篇 |
2010年 | 16616篇 |
2009年 | 16575篇 |
2008年 | 22186篇 |
2007年 | 22307篇 |
2006年 | 21165篇 |
2005年 | 19112篇 |
2004年 | 17288篇 |
2003年 | 15582篇 |
2002年 | 15244篇 |
2001年 | 17564篇 |
2000年 | 13577篇 |
1999年 | 10459篇 |
1998年 | 8551篇 |
1997年 | 8631篇 |
1996年 | 7991篇 |
1995年 | 7248篇 |
1994年 | 7105篇 |
1993年 | 6788篇 |
1992年 | 7743篇 |
1991年 | 8010篇 |
1990年 | 7628篇 |
1989年 | 7386篇 |
1988年 | 7282篇 |
1987年 | 7233篇 |
1986年 | 6717篇 |
1985年 | 8948篇 |
1984年 | 9266篇 |
1983年 | 7519篇 |
1982年 | 8011篇 |
1981年 | 7642篇 |
1980年 | 7366篇 |
1979年 | 7909篇 |
1978年 | 8313篇 |
1977年 | 8146篇 |
1976年 | 8189篇 |
1975年 | 7698篇 |
1974年 | 7745篇 |
1973年 | 7977篇 |
1972年 | 5323篇 |
1971年 | 4467篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
J‐F. Masson Slaana Bundalo‐Perc Ana Delgado 《Journal of Polymer Science.Polymer Physics》2005,43(3):276-279
Differential scanning calorimetry (DSC) does not allow for easy determination of the glass‐transition temperature (Tg) of the polystyrene (PS) block in styrene–butadiene–styrene (SBS) block copolymers. Modulated DSC (MDSC), which deconvolutes the standard DSC signal into reversing and nonreversing signals, was used to determine the (Tg) of both the polybutadiene (PB) and PS blocks in SBS. The Tg of the PB block was sharp, at ?92 °C, but that for the PS blocks was extremely broad, from ?60 to 125 °C with a maximum at 68 °C because of blending with PB. PS blocks were found only to exist in a mixed PS–PB phase. This concurred with the results from dynamic mechanical analysis. Annealing did not allow for a segregation of the PS blocks into a pure phase, but allowed for the segregation of the mixed phase into two mixed phases, one that was PB‐rich and the other that was PS‐rich. It is concluded that three phases coexist in SBS: PB, PB‐rich, and PS‐rich phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 276–279, 2005 相似文献
162.
163.
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
164.
The classical (first integral) methods of studying restrictions on the possible motion of gravitationally interacting bodies are reviewed. The simple and flexible inequality method is extended to a similar approach to the relationship between possible forbidden motion and (asymptotic) symmetries in the relativistic few-body problem. This extended method is used to reproduce the standard results of bounded motion for a test particle in a Schwarzschild geometry. The existence of bounded motion is shown for the general relativistic few-body problem and the difficulties in determining such bounded motion is analysed. The use of this approach to obtaining a relativistic alternative to the classical Roche lobe analysis in contact binaries is discussed. 相似文献
165.
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
166.
Lerner E.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(2):259-263
A cosmological model is presented that produces He, C, O, D, Li, Be, and B in their observed abundances without a Big Bang. The elements are produced during the 1.5-Gy formation period of a galaxy, with C, O, and other heavy elements produced by stars of M >12 M3 , He by stars of 6 Ms<M <12 Ms, and D, Li, Be, and B by cosmic-ray reactions in a nearly pure H plasma halo. Thus, the model shows that the major elements used in astrophysical studies can be produced during galactic formation by exactly the same processes known to function today at much lower rates 相似文献
167.
We consider three one-dimensional quantum, charged and spinless particles interacting through delta potentials. We derive
sufficient conditions which guarantee the existence of at least one bound state. 相似文献
168.
Butyltins were analyzed in waters from California river and lake marinas and were detected at the part per trillion (ppt) level in most locations. The tributyltin:dibutyltin (TBT/DBT) ratios in the fresh waters were similar to those in their saline counterparts indicating like rates of degradation in the two salinity regimes. 相似文献
169.
We theoretically investigated the mass dependence of the sympathetic cooling rate of gas-phase ions trapped in a linear radio-frequency-quadrupole
ion trap. Using an a priori molecular dynamical calculation, tracing numerically with Newtonian equations of motion, we found
that ions with a mass greater than 0.54±0.04 times that of the laser-cooled ions are sympathetically cooled; otherwise, they
are heated. To understand the mass dependence obtained using the molecular-dynamical calculation, we made a heat-exchange
model of sympathetic cooling, which shows that the factor of 0.54±0.04 is a consequence of absence of micro-motion along the
axis of the linear ion trap.
Received: 10 December 2001 / Revised version: 28 January 2002 / Published online: 14 March 2002 相似文献
170.