全文获取类型
收费全文 | 17107篇 |
免费 | 2964篇 |
国内免费 | 2246篇 |
专业分类
化学 | 8065篇 |
晶体学 | 196篇 |
力学 | 743篇 |
综合类 | 155篇 |
数学 | 1482篇 |
物理学 | 4361篇 |
无线电 | 7315篇 |
出版年
2024年 | 66篇 |
2023年 | 354篇 |
2022年 | 579篇 |
2021年 | 613篇 |
2020年 | 704篇 |
2019年 | 660篇 |
2018年 | 588篇 |
2017年 | 604篇 |
2016年 | 721篇 |
2015年 | 993篇 |
2014年 | 1109篇 |
2013年 | 1354篇 |
2012年 | 1598篇 |
2011年 | 1579篇 |
2010年 | 1357篇 |
2009年 | 1334篇 |
2008年 | 1318篇 |
2007年 | 1185篇 |
2006年 | 1111篇 |
2005年 | 909篇 |
2004年 | 657篇 |
2003年 | 506篇 |
2002年 | 482篇 |
2001年 | 360篇 |
2000年 | 304篇 |
1999年 | 219篇 |
1998年 | 125篇 |
1997年 | 114篇 |
1996年 | 99篇 |
1995年 | 99篇 |
1994年 | 69篇 |
1993年 | 69篇 |
1992年 | 45篇 |
1991年 | 39篇 |
1990年 | 43篇 |
1989年 | 27篇 |
1988年 | 45篇 |
1987年 | 12篇 |
1986年 | 26篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1978年 | 21篇 |
1977年 | 9篇 |
1973年 | 9篇 |
1971年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Sannian Song Zhitang Song Bo Liu Liangcai Wu Songlin Feng 《Applied Physics A: Materials Science & Processing》2010,99(4):767-770
The phase-change characteristics of Ge2Sb2Te5 (GST) films for phase-change random access memory (PCM) devices were improved by incorporating HfO2 into GST film using cosputtering at room temperature. Phase separation (GST-rich nanocrystals were surrounded by HfO2-rich amorphous phase) has been observed in annealed GST-HfO2 composite films and the segregated domains exhibited a relatively uniform size. The reduced reset voltage of GST-HfO2 based cell was due to the reduced programming volume by incorporating HfO2 into GST. This work clearly reveals the highly promising potential of GST-HfO2 composite films for application in PCM. 相似文献
992.
We present an explicit expression of the anomaly formula for the Cappell-Miller holomorphic torsion for Khler manifolds. 相似文献
993.
This paper observes the parametric excitation on atom chip by measuring the trap loss when applying a parametric modulation. By modulating the current in chip wires, it modulates not only the trap frequency but also the trap position. It shows that the strongest resonance occurs when the modulation frequency equals to the trap frequency. The resonance amplitude increases exponentially with modulation depth. Because the Z-trap is an anharmonic trap, there exists energy selective excitation which would cause parametric cooling. We confirm this effect by observing the temperature of atom cloud dropping. 相似文献
994.
995.
Chunling Liu Yanping Yao Chunwu Wang Xin Gao Zhongliang Qiao Mei Li Yuxia Wang Baoxue Bo 《中国光学快报(英文版)》2008,6(3)
In order to improve the optical properties of the Ⅲ-Ⅴ laser diodes(LDs) by means of H2S plasma passivation technology,H2S plasma passivation treatment is performed on the GaAs(110) surface.The optimum passivation conditions obtained are 60-W radio frequency(RF)power and 20-min duration.So the laser cavity surfaces axe treated under the optimum passivation conditions.Consequently,compared with unpassivated lasers with only AR/HR-coatings,the catastrophic optical damage (COD) threshold value of the passivated lasers by H2S plasma treatment is increased by 33%,which is almost the same as that of (NH4)2Sx treatment.And the life-test experiment has demonstrated that this passivation method is more stable than(NH4)2Sx solution wet-passivated treatment. 相似文献
996.
Depolarization properties of cirrus clouds from polarization lidar measurements over Hefei in spring
A new polarization lidar has been developed for detecting depolarization characteristics of aerosol and cirrus over Hefei (31.90°N, 117.16°E), China. The fundamental principle of polarization lidar is briefly introduced. 相似文献
997.
A general version of the maximum pseudolikelihood estimate of parameters within the class of Gauss–Markov random fields is
stated in a rigorous way. Its asymptotic properties, namely the consistency, the asymptotic normality, and the relative asymptotic
efficiency are studied. Explicit formulas for the asymptotic covariance matrix are given, and a decrease of efficiency is
proved. A numerical example is added to show that the efficiency can be improved by enlarging the range of the conditional
distribution used in the estimator.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
998.
The uniqueness of classical semicontinuous viscosity solutions of the Cauchy problem for Hamilton–Jacobi equations is established for globally Lipschitz continuous and convex Hamiltonian H=H(Du), provided the discontinuous initial value function ?(x) is continuous outside a set Γ of measure zero and satisfies
(1)
We prove that the discontinuous solutions with almost everywhere continuous initial data satisfying () become Lipschitz continuous after finite time for locally strictly convex Hamiltonians. The L1-accessibility of initial data and a comparison principle for discontinuous solutions are shown for a general Hamiltonian. The equivalence of semicontinuous viscosity solutions, bi-lateral solutions, L-solutions, minimax solutions, and L∞-solutions is clarified. To cite this article: G.-Q. Chen, B. Su, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 113–118 相似文献
999.
1000.
Affolder T Akimoto H Akopian A Albrow MG Amaral P Amidei D Anikeev K Antos J Apollinari G Arisawa T Artikov A Asakawa T Ashmanskas W Azfar F Azzi-Bacchetta P Bacchetta N Bachacou H Bailey S de Barbaro P Barbaro-Galtieri A Barnes VE Barnett BA Baroiant S Barone M Battle C Bauer G Bedeschi F Belforte S Bell WH Bellettini G Bellinger J Benjamin D Bensinger J Beretvas A Berge JP Berryhill J Bhatti A Binkley M Bisello D Bishai M Blair RE Blocker C Bloom K Blumenfeld B Blusk SR Bocci A Bodek A 《Physical review letters》2002,88(7):071806
We present the first general search for new heavy particles, X, which decay via X --> WZ0 --> e(nu)+jj as a function of M(X) and Gamma(X) in pp collisions at square root[s] = 1.8 TeV. No evidence is found for production of X in 110 pb(-1) of data collected by the Collider Detector at Fermilab. General cross section limits are set at the 95% C.L. as a function of mass and width of the new particle. The results are further interpreted as mass limits on the production of new heavy charged vector bosons which decay via W' --> WZ0 in an extended gauge model as a function of the width, Gamma(W'), and mixing factor between the W' and the standard model W bosons. 相似文献