全文获取类型
收费全文 | 15507篇 |
免费 | 1765篇 |
国内免费 | 1464篇 |
专业分类
化学 | 3544篇 |
晶体学 | 229篇 |
力学 | 1929篇 |
综合类 | 248篇 |
数学 | 9270篇 |
物理学 | 3516篇 |
出版年
2024年 | 31篇 |
2023年 | 142篇 |
2022年 | 164篇 |
2021年 | 269篇 |
2020年 | 404篇 |
2019年 | 350篇 |
2018年 | 334篇 |
2017年 | 405篇 |
2016年 | 446篇 |
2015年 | 327篇 |
2014年 | 649篇 |
2013年 | 1085篇 |
2012年 | 805篇 |
2011年 | 957篇 |
2010年 | 946篇 |
2009年 | 991篇 |
2008年 | 1078篇 |
2007年 | 1150篇 |
2006年 | 953篇 |
2005年 | 869篇 |
2004年 | 786篇 |
2003年 | 819篇 |
2002年 | 699篇 |
2001年 | 556篇 |
2000年 | 501篇 |
1999年 | 446篇 |
1998年 | 413篇 |
1997年 | 339篇 |
1996年 | 275篇 |
1995年 | 250篇 |
1994年 | 210篇 |
1993年 | 146篇 |
1992年 | 138篇 |
1991年 | 107篇 |
1990年 | 95篇 |
1989年 | 71篇 |
1988年 | 69篇 |
1987年 | 54篇 |
1986年 | 58篇 |
1985年 | 61篇 |
1984年 | 49篇 |
1983年 | 24篇 |
1982年 | 55篇 |
1981年 | 43篇 |
1980年 | 29篇 |
1979年 | 23篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 317 毫秒
141.
Summary Hydroxypropyl methyl cellulose (HPMC) and polyethylene glycol 400 (PEG 400) content in HypoTears™ Daily Dose ophthalmic solution
are determined simultaneously by size exclusion chromatography. The retention times of HPMC and PEG 400 are 10.6 and 15.4
minutes, respectively. The method requires minimal sample pretreatment and is accurate and reproducible. The peak area response
from a refractive index detector versus HPMC and PEG 400 concentration is linear over the range of 50–150 % of their label
claims of 2.5 mg/mL and 10 mg/mL, respectively. The mean absolute recoveries of HPMC and PEG 400 at their label claim using
the described method are 98.9±1.3 % and 100.4±1.2 % (mean±SD, n=12), respectively. 相似文献
142.
AClassofCauchyProblemforQuasilinearHyperbolicSystemswiththeWeaklyDissipativeTerms¥LiuFagui;YangQiao(NorthChinaInstituteofWate... 相似文献
143.
Yi Zhan 《应用数学学报(英文版)》1997,13(3):235-242
In [1] we construct a unique bounded Hölder continuous viscosity solution for the nonlinear PDEs with the evolutionp-Laplacian equation and its anisotropic version as typical examples. In this part, we investigate the Lipschitz continuity of the free boundary of viscosity solution and its asymptotic spherical symmetricity, however, this result does not include the anisotropic case.This research is supported by the National Natural Sciences Foundation of China. 相似文献
144.
本文利用Liapunov-Schmidt方法获得了高维自治系统在共振情况下决定周期解个数的分支函数,并通过计算分支函数的主项,分析分支函数的零点,研究了具两对共轭特征根的四维系统多个周期解的共振分支问题. 相似文献
145.
146.
J. M. Speight 《Theoretical and Mathematical Physics》2007,152(1):1043-1055
We study the dynamics of magnetic bubble solitons in a two-dimensional isotropic antiferromagnetic spin lattice in the case
where the exchange integral J(x, y) is position dependent. In the near-continuum regime, this system is described by the relativistic
O(3) sigma model on a space-time with a spatially inhomogeneous metric determined by J. We use the geodesic approximation
to describe the low-energy soliton dynamics in this system: the n-soliton motion is approximated by geodesic motion in the
moduli space M
n
of static n-solitons equipped with the L
2 metric γ. We obtain explicit formulas for γ for various natural choices of J(x, y). Based on these, we show that single soliton
trajectories are refracted with J−1 being analogous to the refractive index and that this refraction effect allows constructing simple bubble lenses and bubble
guides. We consider the case where J has a disk inhomogeneity (with the value J
+ outside a disk and J
− < J
+ inside) in detail. We argue that for sufficiently large J
+/J
−, this type of antiferromagnet supports approximate quasibreathers: two or more coincident bubbles confined within the disk
spin internally while their shape oscillates with a generically incommensurate period.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 1, pp. 191–208, July, 2007. 相似文献
147.
G. N. Merrill 《Journal of Physical Organic Chemistry》2007,20(1):19-29
Ab initio molecular orbital calculations were carried out on epibromohydrin (EBH) and epichlorohydrin (ECH) in an attempt to elucidate their reactivity with respect to a hard nucleophile, hydroxide. These systems were modeled in both the gas phase and a polar solvent under basic conditions. In the gas phase, it was determined that a direct displacement mechanism (nucleophilic attack at the C1 position) was operative for EBH, while an indirect pathway (nucleophilic attack at the C3 position and subsequent intramolecular displacement) was followed for ECH. In an acetone solution, only the indirect displacement mechanism was found to occur. An electrostatic argument is advanced to account for this behavior in polar solution. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
148.
A systematic study of the upper semicontinuity and the lower semicontinuity of the solution map in parametric affine variational
inequalities is given in this paper. Several examples are constructed to analyze the results.
This work was supported by Korea Research Foundation Grant (KRF 2001-015-DP0049), the APEC Postdoctoral Fellowships Program,
and the KOSEF Brain Pool Program. 相似文献
149.
This paper seeks to solve the difficult nonlinear problem in financial markets on the complex system theory and the nonlinear
dynamics principle, with the data-model-concept-practice issue-oriented reconstruction of the phase space by the high frequency
trade data. In theory, we have achieved the differentiable manifold geometry configuration, discovered the Yang-Mills functional
in financial markets, obtained a meaningful conserved quantity through corresponding space-time non-Abel localization gauge
symmetry transformation, and derived the financial solitons, which shows that there is a strict symmetry between manifold
fiber bundle and guage field in financial markets. In practical applications of financial markets, we have repeatedly carried
out experimental tests in a fluctuant evolvement, directly simulating and validating the existence of solitons by researching
the price fluctuations (society phenomena) using the same methods and criterion as in natural science and in actual trade
to test the stock Guangzhou Proprietary and the futures Fuel Oil in China. The results demonstrate that the financial solitons
discovered indicates that there is a kind of new substance and form of energy existing in financial trade markets, which likely
indicates a new science paradigm in the economy and society domains beyond physics.
相似文献
150.
对带有一般实参数第三类Painlevé方程,已有γ<0,δ>0时,解的有界性以及振荡渐近解的表达形式的结论.在本文中,我们给出当δ=0或γ=0时其振荡渐近解的表达形式. 相似文献