全文获取类型
收费全文 | 24336篇 |
免费 | 4134篇 |
国内免费 | 3589篇 |
专业分类
化学 | 18533篇 |
晶体学 | 359篇 |
力学 | 1174篇 |
综合类 | 237篇 |
数学 | 2504篇 |
物理学 | 9252篇 |
出版年
2024年 | 74篇 |
2023年 | 468篇 |
2022年 | 916篇 |
2021年 | 935篇 |
2020年 | 1034篇 |
2019年 | 980篇 |
2018年 | 867篇 |
2017年 | 900篇 |
2016年 | 1267篇 |
2015年 | 1332篇 |
2014年 | 1581篇 |
2013年 | 1973篇 |
2012年 | 2440篇 |
2011年 | 2427篇 |
2010年 | 1767篇 |
2009年 | 1628篇 |
2008年 | 1778篇 |
2007年 | 1527篇 |
2006年 | 1459篇 |
2005年 | 1070篇 |
2004年 | 797篇 |
2003年 | 634篇 |
2002年 | 633篇 |
2001年 | 557篇 |
2000年 | 432篇 |
1999年 | 451篇 |
1998年 | 316篇 |
1997年 | 266篇 |
1996年 | 232篇 |
1995年 | 207篇 |
1994年 | 165篇 |
1993年 | 159篇 |
1992年 | 132篇 |
1991年 | 119篇 |
1990年 | 70篇 |
1989年 | 75篇 |
1988年 | 57篇 |
1987年 | 60篇 |
1986年 | 50篇 |
1985年 | 34篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 8篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
This article concerns the existence of global smooth solution for scalar conservation laws with degenerate viscosity in 2-dimensional space. The analysis is based on successive approximation and maximum principle. 相似文献
92.
Least-squares finite difference (LSFD) method, one of mesh-free methods, is used to solve slider air bearings problem through discritizing the generalized Reynolds equation into nonlinear systems of algebraic equations. Two approximation schemes for the linearization of these equations are presented and compared. And, some new techniques to search supporting points for the reference node in the mesh-free method were proposed and explored. Therefore, these improvements eliminate some potential limitation of the LSFD method previously published and further facilitate its employment in complex slider models. Advanced step slider as an example of negative pressure sliders is simulated and verified using the improved LSFD mesh-free method in head disk systems. 相似文献
93.
This paper is concerned with a class of nonlinear delay partial difference equations with variable coefficients, which may
change sign. By making use of frequency measures, some new oscillatory criteria are established. This is the first time oscillation
of these partial difference equations is discussed by employing frequency measures.
相似文献
94.
This paper presents a connection between the defining basis presented by Beilinson-Lusztig-MacPherson [1] in their geometric setting for quantum GLn and the isomorphism classes of linear quiver representations. More precisely, the positive part of the basis in [1] identifies with the defining basis for the relevant Ringel-Hall algebra; hence, it is a PBW basis in the sense of quantum groups. This approach extends to q-Schur algebras, yielding a monomial basis property with respect to the Drinfeld-Jimbo type presentation for the positive (or negative) part of the q-Schur algebra. Finally, the paper establishes an explicit connection between the canonical basis for the positive part of quantum GLn and the Kazhdan-Lusztig basis for q-Schur algebras. 相似文献
95.
96.
采用气相色谱-质谱(GC-MS)选择离子监测法(SIM),建立了准确可靠、灵敏度高、快速简便的测定维生素C泡腾片中甜蜜素含量的新方法.样品中的甜蜜素衍生后用有机试剂提取,在选择离子模式下进行测定,以保留时间和特征离子比例进行定性,单离子定量.甜蜜素的线性范围为0.05-10mg/L,检出限为0.6mg/kg,回收率为90.5%-96.9%,相对标准偏差小于4.4%.方法分析所用时间短,结果准确可靠,选择性好,适用于维生素C泡腾片中甜蜜素含量的检验. 相似文献
97.
98.
After the laser was invented in 1960, a phase conjugation mirror has been respected to be the most fantastic one for the laser
resonator composition because it can compensate any distortions of the laser beams occurred by the many inhomogenuities of
the laser media and optical components. Among the many phase conjugation configurations, the stimulated Brillouin scattering
phase conjugation mirror is the most simple one and many researchers have tried to utilize it to develop high power/energy
laser systems. For realizing a high energy/power laser system the thermal problem is the most difficult to solve, and some
researchers suggested a beam combination technique to reduce the thermal load of the big laser media to many small sized ones.
To accomplish the beam combination using stimulated Brillouin scattering phase conjugation mirrors (SBS-PCMs), it is necessary
to lock/control the phases of the SBS-PCMs. And some researchers have developed several ways for it, but they can lock the
phases of a limited number of beams overlapped at the foci less than 5, or lock the phases by back-seeding technique but it
loses the phase conjugation characteristics. For realization of the laser fusion driver, it is necessary to combine more than
10 or 100 beams. And the authors have developed recently a new phase controlling/locking technique which is isolated and independent
totally from other beams and it can be applied to an unlimited number of beams in principle. 相似文献
99.
Phenylene vinylene‐based electroluminescent polymers with electron transport block in the main chain
Honghao Sun Chongyu Mei Quanguo Zhou Ze Liu Dongge Ma Lixiang Wang Xiabin Jing Fosong Wang 《Journal of polymer science. Part A, Polymer chemistry》2006,44(11):3469-3478
We report a new route for the design of soluble phenylene vinylene (PV) based electroluminescent polymers bearing electron‐deficient oxadizole (OXD) and triazole (TZ) moieties in the main chains with the aryloxy linkage. Both series of the PV‐based polymers were prepared by Wittig reaction. By properly adjusting the OXD and/or TZ content through copolymerization, we can achieve an enhanced balance of hole‐ and electron injections, such that the device efficiency is significantly improved. Light‐emitting diodes fabricated from P1, P2, P3, P4, P5, P6, and P7 with the configuration of Indium–Tin Oxide (ITO)/Poly (styrene sulfonic acid) doped poly (ethylenedioxythiophene) (PEDOT)/polymer/Ca/Al, emit bright green light with the maximum peak around 500 nm. For the device using the optimal polymer (P4) as emitting layer, a maximum brightness of 1300 cd/m2 at 20 V and a maximum luminance efficiency of 0.325 cd/A can be obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3469–3478, 2006 相似文献
100.
Peng Xu Haitao Wang Rui Lv Qiangguo Du Wei Zhong Yuliang Yang 《Journal of polymer science. Part A, Polymer chemistry》2006,44(12):3911-3920
A novel microphase‐inversion method was proposed for the preparation of TiO2–SiO2/poly(methyl methacrylate) core–shell nanocomposite particles. The inorganic–polymer nanocomposites were first synthesized via a free‐radical copolymerization in a tetrahydrofuran solution, and the poor solvent was added slowly to induce the microphase separation of the nanocomposite and result in the formation of nanoparticles. The average particle sizes of the microspheres ranged from 70 to 1000 nm, depending on the reaction conditions. Transmission electron microscopy and scanning electron microscopy indicated a core–shell morphology for the obtained microspheres. Thermogravimetric analysis and X‐ray photoelectron spectroscopy measurements confirmed that the surface of the nanocomposite microspheres was polymer‐rich, and this was consistent with the core–shell morphology. The influence of the synthetic conditions, such as the inorganic composition and the content of the crosslinking monomer, on the particle properties was studied in detail. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3911–3920, 2006 相似文献