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   576381篇
  免费   6099篇
  国内免费   1723篇
化学   304039篇
晶体学   8714篇
力学   26000篇
综合类   17篇
数学   68885篇
物理学   176548篇
  2021年   4858篇
  2020年   5353篇
  2019年   5843篇
  2018年   7614篇
  2017年   7447篇
  2016年   11298篇
  2015年   7125篇
  2014年   10989篇
  2013年   26732篇
  2012年   20555篇
  2011年   25087篇
  2010年   17486篇
  2009年   17281篇
  2008年   22765篇
  2007年   22836篇
  2006年   21278篇
  2005年   19068篇
  2004年   17681篇
  2003年   15653篇
  2002年   15417篇
  2001年   17390篇
  2000年   13280篇
  1999年   10391篇
  1998年   8569篇
  1997年   8381篇
  1996年   7965篇
  1995年   7295篇
  1994年   7082篇
  1993年   6862篇
  1992年   7709篇
  1991年   7793篇
  1990年   7446篇
  1989年   7104篇
  1988年   7167篇
  1987年   7102篇
  1986年   6675篇
  1985年   8699篇
  1984年   8979篇
  1983年   7181篇
  1982年   7419篇
  1981年   7404篇
  1980年   6884篇
  1979年   7359篇
  1978年   7646篇
  1977年   7500篇
  1976年   7491篇
  1975年   6937篇
  1974年   6880篇
  1973年   7017篇
  1972年   4795篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The EPR spectra evolution of Cs2Zn1?x Cux(ZrF6)2 · 6H2O (x=0.01, 0.6, 0.8, and 1.0) in the temperature range 4.2–330 K and the x-ray structure analysis of the compound with x=1.0 in the range 150–327 K show that the Jahn-Teller (JT) complex Cu(H2O)6 coordination sphere undergoes a plastic deformation. The observed effect is due to the combined influence of small lattice strains existing in the paraphase and a new one appearing as a result of a ferroelastic phase transition and increasing with decreasing temperature below T c . It is proved that both cooperative interactions between JT complexes and ferroelastic strain stabilize a certain JT configuration. The problem of instability of a JT configuration compressed at T ~ 265 K is discussed.  相似文献   
82.
Discharges with liquid nonmetallic electrodes of much interest for applications are investigated. It is found that a dc discharge between two streams of tap water in air at atmospheric pressure is stable at a currentof 40≤I≤100 mA. The discharge exists in the diffuse (volume) form with a relatively low current density (∼0.2 A/cm2) and a high (above one kilovolt) voltage drop across the air gap (∼1 cm) between the water electrodes. The current density and voltage depend only slightly on the discharge current. Probe measurements show that three regions can be distinguished in the discharge: two electrode regions (1–2 mm in length) and a discharge column with a constant electric field of ≈0.8 kV/cm (i.e., E/N≈20 Td, because the gas in the discharge is heated up to 1500–2000 K). The average electric field strength near the electrodes is E≈2–3×103 V/cm (E/N≈60–80 Td). The charged particle density in the column is n ∼ 1012 cm−3. The probe measurements of n agree with the previous microwave absorption measurements. The water vapor concentration in the column is also estimated from probe measurements.  相似文献   
83.
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   
84.
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   
85.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 1, pp. 46–50, January, 1991.  相似文献   
86.
In intonation research, prominence-lending pitch movements have either been described on a linear or on a logarithmic frequency scale. An experiment has been carried out to check whether pitch movements in speech intonation are perceived on one of these two scales or on a psychoacoustic scale representing the frequency selectivity of the auditory system. This last scale is intermediary between the other two scales. Subjects matched the excursion size of prominence-lending pitch movements in utterances resynthesized in different pitch registers. Their task was to adjust the excursion size in a comparison stimulus in such a way that it lent equal prominence to the corresponding syllable in a fixed test stimulus. The comparison stimulus and the test stimulus had pitches running parallel on either the logarithmic frequency scale, the psychoacoustic scale, or the linear frequency scale. In one-half of the experimental sessions, the test stimulus was presented in the low register, while the comparison stimulus was presented in the high register, and, conversely, for the other half of the sessions. The result is that, in all cases, stimuli are matched in such a way that the average excursion sizes in different registers are equal on the psychoacoustic scale.  相似文献   
87.
88.
89.
90.
On Quantum Team Games   总被引:2,自引:0,他引:2  
Recently Liu and Simaan (2004) convex static multi-team classical games have been introduced. Here they are generalized to both nonconvex, dynamic and quantum games. Puu's incomplete information dynamical systems are modified and applied to Cournot team game. The replicator dynamics of the quantum prisoner's dilemma game is also studied.  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