全文获取类型
收费全文 | 1358090篇 |
免费 | 25789篇 |
国内免费 | 7705篇 |
专业分类
化学 | 682620篇 |
晶体学 | 20079篇 |
力学 | 74686篇 |
综合类 | 104篇 |
数学 | 242357篇 |
物理学 | 371738篇 |
出版年
2021年 | 13511篇 |
2020年 | 15925篇 |
2019年 | 16060篇 |
2016年 | 27522篇 |
2015年 | 20717篇 |
2014年 | 30479篇 |
2013年 | 74506篇 |
2012年 | 39169篇 |
2011年 | 36010篇 |
2010年 | 36732篇 |
2009年 | 38886篇 |
2008年 | 35284篇 |
2007年 | 30811篇 |
2006年 | 38325篇 |
2005年 | 29608篇 |
2004年 | 31143篇 |
2003年 | 29300篇 |
2002年 | 30550篇 |
2001年 | 30116篇 |
2000年 | 25831篇 |
1999年 | 23040篇 |
1998年 | 21284篇 |
1997年 | 21205篇 |
1996年 | 21199篇 |
1995年 | 19250篇 |
1994年 | 18680篇 |
1993年 | 18235篇 |
1992年 | 18377篇 |
1991年 | 18623篇 |
1990年 | 17823篇 |
1989年 | 17843篇 |
1988年 | 17437篇 |
1987年 | 17314篇 |
1986年 | 16321篇 |
1985年 | 22713篇 |
1984年 | 23895篇 |
1983年 | 20049篇 |
1982年 | 21759篇 |
1981年 | 20957篇 |
1980年 | 20280篇 |
1979年 | 20508篇 |
1978年 | 21796篇 |
1977年 | 21396篇 |
1976年 | 21146篇 |
1975年 | 19873篇 |
1974年 | 19576篇 |
1973年 | 20040篇 |
1972年 | 14512篇 |
1968年 | 12344篇 |
1967年 | 12671篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
281.
The present paper analyzes the properties of structural phase transitions under the extremal conditions of high pressures. In the context of the theory of density functional (TDF), the pressures of the B1–B2 transitions are calculated for small alkali-halide crystals as functions of the crystal size. The size effect of the B1–B2 transition – an increase in the transition pressure with the decreasing crystal grain radius – has been established for all investigated halides except lithium fluoride for which the dependence is reverse. 相似文献
282.
Nikolaos V. Tsekos Michael Garwood Kmil Ugurbil 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(2):187
A new technique is presented for generating myocardial tagging using the signal intensity minima of the transition zones between the bands of 0° and 360° rotations, induced by a tandem of two adiabatic delays alternating with nutations for tailored excitation (DANTE) inversion sequences. With this approach, the underlying matrix corresponds to magnetization that has experienced 0° or 360° rotations. The DANTE sequences were implemented from adiabatic parent pulses for insensitivity of the underlying matrix to B1 inhomogeneity. The performance of the proposed tagging technique is demonstrated theoretically with computer simulations and experimentally on phantom and on the canine heart, using a surface coil for both RF transmission and signal reception. The simulations and the experimental data demonstrated uniform grid contrast and sharp tagging profiles over a twofold variation of the B1 field magnitude. 相似文献
283.
We calculate the leading and next-to-leading logarithmic resummed distribution for the jet broadening in deep inelastic scattering,
as well as the power correction for both the distribution and mean value. A truncation of the answer at NLL accuracy, as is
standard, leads to unphysical divergences. We discuss their origin and show how the problem can be resolved. We then examine
DIS specific procedures for matching to fixed order calculations and compare our results to the data. One of the tools developed
for the comparison is an NLO parton distribution evolution code. When compared to PDF sets from MRST and CTEQ it reveals limited
discrepancies in both.
Received: 16 October 2001 / Published online: 12 April 2002 相似文献
284.
285.
Sanzharov N. A. Yarovoi A. T. Bekhtereva E. S. Ulenikov O. N. 《Russian Physics Journal》2002,45(10):1024-1031
Analytical formulas are derived that describe the dependences of the transition probabilities in vibrational-rotational spectra of XY3-type molecules with C
3v
symmetry on the rotational quantum numbers. 相似文献
286.
Most of the novel highly potent drugs, developed on the basis of modern molecular medicine, taking into account cell surface recognition techniques, show poor water solubility. A chemical modification of the drug substance enhancing the solubility often decreases the pharmacological activity. Thus, as an alternative an increase of the solubility can be obtained by the reduction of the size of the drug particles. Unfortunately, it is often difficult to obtain micro or nanosized drug particles by classical or more advanced crystallization using supercritical gases or by milling techniques. In addition, nanosized particles are often not physically stable and need to be stabilized in an appropriate matrix. Thus, it may be of interest to manufacture directly nanosized drug particles stabilized in an inert hydrophilic matrix, i.e. nanostructured and nanocomposite systems. Solid solutions and solid dispersions represent nanostructured and nanocomposite systems. In this context, the use of the vacuum-fluidized-bed technique for the spray-drying of a low water soluble drug cosolubilized with a hydrophilic excipient in a polar organic solvent is discussed. In order to avoid the use of organic solvents, a special spray-freeze-drying technique working at atmospheric pressure is presented. This process is very suitable for temperature and otherwise sensitive drugs such as pharmaproteins. 相似文献
287.
A detailed analysis is made within perturbative QCD of the decays into gluon jets of P-wave and S-wave quarkonia (JPC = 0++, 1++, 2++, 1+? and 0?+, 1??). For all those states we compute to leading non-trivial order in αs the conventional fraction f(?, δ) of the jet-like hadronic final states, characterized by the back-to-back cone of half angle δ, in which all but a small fraction ? of the total energy is emitted. To the same order we give also the average values of thrust momenta and spherocity distributions. 相似文献
288.
Inventiones mathematicae - 相似文献
289.
Electrical resistivity of U3Tein4, U2Te3 (cubic) and UTe3 has been measured over temperature range 4.2–300 K. The two former compounds appear to be semimetallic conductors while the last one has semiconducting character. The results are discussed in the terms of available magnetic data. 相似文献
290.