全文获取类型
收费全文 | 18667篇 |
免费 | 1198篇 |
国内免费 | 1106篇 |
专业分类
化学 | 1471篇 |
晶体学 | 32篇 |
力学 | 327篇 |
综合类 | 208篇 |
数学 | 2748篇 |
物理学 | 2061篇 |
综合类 | 14124篇 |
出版年
2024年 | 55篇 |
2023年 | 178篇 |
2022年 | 345篇 |
2021年 | 435篇 |
2020年 | 362篇 |
2019年 | 369篇 |
2018年 | 412篇 |
2017年 | 495篇 |
2016年 | 504篇 |
2015年 | 570篇 |
2014年 | 1005篇 |
2013年 | 948篇 |
2012年 | 952篇 |
2011年 | 1063篇 |
2010年 | 822篇 |
2009年 | 922篇 |
2008年 | 1013篇 |
2007年 | 1367篇 |
2006年 | 1283篇 |
2005年 | 1204篇 |
2004年 | 1100篇 |
2003年 | 915篇 |
2002年 | 800篇 |
2001年 | 613篇 |
2000年 | 508篇 |
1999年 | 439篇 |
1998年 | 332篇 |
1997年 | 288篇 |
1996年 | 247篇 |
1995年 | 249篇 |
1994年 | 195篇 |
1993年 | 172篇 |
1992年 | 146篇 |
1991年 | 129篇 |
1990年 | 119篇 |
1989年 | 101篇 |
1988年 | 79篇 |
1987年 | 75篇 |
1986年 | 50篇 |
1985年 | 17篇 |
1984年 | 26篇 |
1983年 | 7篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1973年 | 4篇 |
1955年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
For the purpose of testing the spherical uniformity based on i.i.d. directional data (unit vectors) zi, i=1,…,n, Anderson and Stephens (Biometrika 59 (1972) 613–621) proposed testing procedures based on the statistics Smax=maxu S(u) and Smin=minu S(u), where u is a unit vector and nS(u) is the sum of squares of u′zi's. In this paper, we also consider another test statistic Srange=Smax−Smin. We provide formulas for the P-values of Smax, Smin, Srange by approximating tail probabilities of the limiting null distributions by means of the tube method, an integral-geometric approach for evaluating tail probability of the maximum of a Gaussian random field. Monte Carlo simulations for examining the accuracy of the approximation and for the power comparison of the statistics are given. 相似文献
132.
Francis J. Narcowich Joseph D. Ward Holger Wendland. 《Mathematics of Computation》2005,74(250):743-763
In this paper we discuss Sobolev bounds on functions that vanish at scattered points in a bounded, Lipschitz domain that satisfies a uniform interior cone condition. The Sobolev spaces involved may have fractional as well as integer order. We then apply these results to obtain estimates for continuous and discrete least squares surface fits via radial basis functions (RBFs). These estimates include situations in which the target function does not belong to the native space of the RBF.
133.
Hiroshi Sakamoto 《Journal of Discrete Algorithms》2005,3(2-4):416-430
A linear-time approximation algorithm for the grammar-based compression is presented. This is an optimization problem to minimize the size of a context-free grammar deriving a given string. For each string of length n, the algorithm guarantees approximation ratio without suffix tree construction. 相似文献
134.
We use methods of nonequilibrium statistical thermodynamics to investigate two dissipative processes in solids. We find the electron energy losses of a particle moving in a planar channeling regime and the sound absorption coefficient in metals under electron impurity scattering. The oscillator model is used to analyze the contribution from the effect of electron entrainment by a moving scattering center to the total dissipated energy. We investigate the frequency and temperature dependence of energy losses and also the dependence of the absorption coefficient on the sound wave vector. 相似文献
135.
Ryo Ikehata 《Journal of Mathematical Analysis and Applications》2003,288(2):803-818
We generalize a previous result of Ikehata (Math. Methods Appl. Sci., in press), which studies the critical exponent problem of a semilinear damped wave equation in the one-dimensional half space, to the general N-dimensional half space case. That is to say, one can show the small data global existence of solutions of a mixed problem for the equation utt−Δu+ut=|u|p with the power p satisfying p∗(N)=1+2/(N+1)<p?N/[N−2]+ if we deal with the problem in the N-dimensional half space. 相似文献
136.
We study a system of quasilinear equations describing one-dimensional flow of a viscous compressible heat-conducting medium with a nonmonotone state function and mass force. The large-time behavior of solutions is considered for arbitrarily large initial data. In spite of possible nonuniqueness and discontinuity of the stationary solution, we prove L2-stabilization for the stress and heat flux as t → ∞ along with corresponding global energy estimates for them. The new method of proof utilizes a combination of energy type equalities for the stress and heat flux. Consequently, H1-stabilization of the velocity and temperature along with global estimates for their derivatives are valid as well. 相似文献
137.
1 Results The photosynthetic bacterial reaction center (RC) is a membrane protein complex.The RC is composed of three protein subunits and redox components such as bacteriochlorophylls, bacteriopheophytins,and quinones.The RC performs the photochemical electron transfer from the bacteriochlorophyll dimer through a series of electron donor and acceptor molecules to a secondary quinone,QB.QB accepts electrons from a primary quinone,QA,in two sequential electron transfer reactions.The second electron trans... 相似文献
138.
随着教育改革的不断深入,利用多媒体手段进行教学、科研已是大势所趋。然而,如何充分挖掘和开发多媒体教室设备的各项功能,最大限度的发挥多媒体教室使用效率,以满足教学的最大需要,是一个普遍问题。因此,结合我校的实际情况,探讨我校多媒体教室设备配置问题,使多媒体设备更趋于完善,从而提高使用效率和教学效果。 相似文献
139.
叶海玲 《漳州师范学院学报》2007,20(3):138-140
树立高等学校资料室个性化服务的管理理念,在读者与管理者之间建立良好的桥梁.管理者尽其可能地为读者提供最优质的服务,真正做到人尽其才,物尽其用. 相似文献
140.
K. Vinay Kumar Reddy B. Sreenivasa Reddy M. Sreenath Reddy Ch. Gopal Reddy P. Yadagiri Reddy K. Rama Reddy 《Radiation measurements》2003,36(1-6):419-423
Studies conducted by Atomic Minerals Directorate of Exploration and Research (AMD) of Hyderabad, India had established the presence of higher concentrations of uranium in Lambapur and Peddagattu areas of Nalgonda district, AP, India and it was estimated that it could be a viable source for commercial extraction. The envisaged extraction process involves dispersion of radioactive particulate matter into atmosphere. Environmental radioactive studies in and around proposed mining areas at this point of time will be extremely useful for establishing base line data before a large scale uranium extraction process comes into existence. To this end, Solid State Nuclear Track Detectors were installed to evaluate indoor radon and thoron concentration levels in the dwellings of the area. The geometric means of radon and thoron concentration levels were found to be (7.1±0.2)×101 and (6.7±0.3)×101 Bq/m3, respectively. Simultaneously, natural background radiation measurements were also made and these levels are found to vary from 770 to 3995 μGy/y in the spatial distribution. 相似文献