首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   202244篇
  免费   1958篇
  国内免费   501篇
化学   110525篇
晶体学   3647篇
力学   7996篇
综合类   11篇
数学   19200篇
物理学   63324篇
  2020年   1724篇
  2019年   1917篇
  2018年   2236篇
  2017年   2355篇
  2016年   3515篇
  2015年   2190篇
  2014年   3546篇
  2013年   9078篇
  2012年   6504篇
  2011年   8008篇
  2010年   5696篇
  2009年   5654篇
  2008年   7154篇
  2007年   7066篇
  2006年   6693篇
  2005年   6050篇
  2004年   5519篇
  2003年   5099篇
  2002年   4867篇
  2001年   6141篇
  2000年   4622篇
  1999年   3518篇
  1998年   2745篇
  1997年   2702篇
  1996年   2591篇
  1995年   2440篇
  1994年   2330篇
  1993年   2165篇
  1992年   2826篇
  1991年   2730篇
  1990年   2672篇
  1989年   2690篇
  1988年   2713篇
  1987年   2721篇
  1986年   2591篇
  1985年   3303篇
  1984年   3313篇
  1983年   2598篇
  1982年   2709篇
  1981年   2763篇
  1980年   2533篇
  1979年   2875篇
  1978年   2861篇
  1977年   2980篇
  1976年   2816篇
  1975年   2553篇
  1974年   2509篇
  1973年   2465篇
  1972年   1702篇
  1968年   1703篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The joint production of ? mesons andπ ±,π 0,p, \(\bar p\) ,K s 0 andK ± is investigated using a sample of 600,000 inclusive ? meson events obtained in hadron Be interactions with incidentπ ±,p, \(\bar p\) andK ± beams. Evidence is presented for the joint production of ? mesons and strange particles produced with non-strange incident beams. With incidentK ± beam the number of additional strange particles is suppressed. The results are found to be in agreement with the qualitative predictions of a parton fusion model. The comparison with the Lund model for lowp T processes is fair.  相似文献   
992.
Properties of secondaries associated with a high-p T charged trigger particle (3<p T <5 GeV/c) were studied for αp and αα interactions at c.m. energies \(\sqrt s = 88\) GeV and 125 GeV, respectively. Thep T distributions of secondaries in the away-jet and trigger-jet regions were compared with those for high-p T pp interactions. No statistically significant differences were seen, except at lowp T . Momentum and angular distributions of spectator and leading protons were studied as a function of charge and rapidity of the trigger hadron. The observed correlations between trigger charge and number of spectator protons provide evidence of valence quark contributions to the trigger jet.  相似文献   
993.
Results on inclusive ? production inK ? p interactions at 110 GeV/c are presented. The production cross section is found to be larger than in πp andpp interactions at similar energies, suggesting OZI allowed \(s\bar s\) fusion to be the dominant mechanism in ? production. Thex distributions of ? and \(\bar K^{*0} \) are found to be similar to each other over the entirex range suggesting an overall strangeness suppression factor of 0.20±0.04 in the sea to be the dominant source of the difference in the cross section for ? and \(\bar K^{*0} \) . There is no evidence of a narrowφπ ? state around 2.1 GeV/c2 as suggested byK + experiments, but there is some excess of events in the region 1.94?1.98 GeV/c2 consistent with theF-meson mass as observed ine + e ? experiments.  相似文献   
994.
Production rates and signals for coloroctet leptonsl 8 atep machines like Hera and a \(\sqrt s = 2\) TeV collider are presented. In case of very heavy leptogluons:m 8≈0(100 GeV) we argue that rates based on direct electron-gluon fusion are possibly strongly overestimated in the literature. In composite models the appearance of leptogluons always implies the existence of color exotic vectorbosons. Therefore we considerl 8 production in electron-quark scatterings. We find that even at HERA energies such reactions should be detectable if there is nearby compositeness (Λ H ~ several TeV) and the mass of the coloroctet neutrinom v8<180 GeV. From such events it would be possible to extract information on the deeper structure of the preon model.  相似文献   
995.
In composite models of quarks, leptons and weak bosons whereW-constituents are colored objects, color octet partners ofW ± andZ 0 are predicted. We study in detail the phenomenology of these particles. Independent of the specific model one expects a color octet isotriplet of vector bosons (W 8 ± ,Z 8 0 ) with mass in the range of 100–200 GeV, and a color octet isosinglet vector bosonV 8 0 with substantially larger mass, due to mixing with the gluon. Moreover, relatively light color octet excitations of the leptons appear, while the existence of “color exotic” partners of the quarks is model dependent. These particles decay mainly into a lepton (quark) and a gluon. We construct the couplings ofW 8 ± ,Z 8 0 andV 8 0 to ordinary and “color exotic” fermions. The signals of color octet weak bosons in low energy weak reactions are explored in detail. The production cross section ofW 8 ± (Z 8 0 ) in hadron-hadron collisions is calculated for \(0.54TeV \leqq \sqrt s \leqq 20TeV\) . Various decay modes of colored weak bosons are studied. The most prominent decay signatures ofW 8 ± andZ 8 0 are events of the type (l +-: charged lepton;j: hadronic jet; : missing transverse momentum). The present CERN \(p\bar p\) collider data on such events are discussed in the light ofW 8 ± andZ 8 0 decays. If colored weak bosons are not found with a mass less than ~250 GeV composite model building will be strongly restricted.  相似文献   
996.
We study the geometrical connection between the fundamental equations of the quasiclassical model proposed by Rodimov to explain the behavior of microparticles in atomic systems in his monograph Self-Oscillating Quantum Mechanics; the v and u equations. It is shown that the geometry of the spaces for the v and u equations is different, but the metrical coefficients are related by simple algebraic relations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 5, pp. 66–70, May, 1986.The author thanks Go I. Flesher for interest in the work and useful critical discussions and also I. L. Bukhbinder for fruitful discussions of the fundamental aspects of the work.  相似文献   
997.
Trap centers in the Si-SiO2 interface region of MOS structures doped by ion implantation of gold have been investigated using constant capacitance deep level transient spectroscopy (CC-DLTS). Gold doses of 1012–3 × 1013 cm–2 were implanted into the back surface of the wafers and were then redistributed during a diffusion anneal for 30 min at 1100° or 900° C. Three Au-related trap levels have been observed in the interface region, which were attributed to the Au-donor (E v +0.35 eV), the Au-acceptor (E v +0.53 eV), and the Au-Fe complex (E v +0.45 eV). The trap concentration profiles show that the Si-SiO2 interface affects the Au concentration in a depth range of 1 m from the interface and that gettering of Au occurs at the interface. The interface state density is independent of the Au concentration at the interface even for concentrations of 1015 cm–3.  相似文献   
998.
The ESR of the spin glassAgMn (2.7 and 9.6 at %) has been investigated below and aboveT g(0.1T g<T<5T g) at various microwave frequencies. The analysis yields:1) No explicit frequency dependence but strong magnetic field effects, inherent with ESR-experiments.2) Part of the excess line width is identified as critical spin fluctuations, following a power law. However, because of the presence of the applied field, the reduced temperaturet is not a good scaling variable. We choose the non-linear susceptibility X s divided byH 2, which scales as the order parameter susceptibility. The experiment yieldsW ex(X s /H 2) p ,p=0.42. From this we deduce z3.  相似文献   
999.
Amorphous alloys of Zr x Cu100–x (55x72) quenched from the melt are investigated by low temperature specific heat measurements. The influence of concentrationx, temperature of the melt before the quenching process and heat treatment on the electronic density of states, the Debye temperature and the superconducting transition temperature is examined. The latter one is the most affected value by structural relaxation while the specific heat in the normal conducting region remains nearly unchanged.  相似文献   
1000.
We have studied the enhanced ionic conductivity of thin films of LiI evaporated onto a planar sapphire surface carrying interdigital Au-electrodes. The interface conductivity parallel to the surface was measured in situ for increasing film thickness, up to 3,000 Å. The specific conductivity of LiI in the first 300 Å — adjacent to the sapphire — was found to exceed the bulk conductivity of LiI by nearly one order of magnitude. From our observations we conclude that the specific conductivity of LiI decreases exponentially with distance from the sapphire surface reaching the bulk LiI-value only at a distance of 3,000 Å. The conductivity of a 350 Å thick film varies with temperature (25°CT120°C) in accordance with an activation energy of 0.40±0.04 eV. This is in good agreement with the activation energy of bulk LiI in the extrinsic region.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号