全文获取类型
收费全文 | 279470篇 |
免费 | 3723篇 |
国内免费 | 2021篇 |
专业分类
化学 | 150025篇 |
晶体学 | 4290篇 |
力学 | 12778篇 |
综合类 | 104篇 |
数学 | 30894篇 |
物理学 | 87123篇 |
出版年
2020年 | 2452篇 |
2019年 | 2644篇 |
2018年 | 3431篇 |
2017年 | 3412篇 |
2016年 | 4940篇 |
2015年 | 3109篇 |
2014年 | 4862篇 |
2013年 | 11469篇 |
2012年 | 8941篇 |
2011年 | 10830篇 |
2010年 | 7713篇 |
2009年 | 7565篇 |
2008年 | 10036篇 |
2007年 | 10186篇 |
2006年 | 9531篇 |
2005年 | 8674篇 |
2004年 | 7896篇 |
2003年 | 7109篇 |
2002年 | 6988篇 |
2001年 | 7624篇 |
2000年 | 5931篇 |
1999年 | 4661篇 |
1998年 | 4173篇 |
1997年 | 4101篇 |
1996年 | 3843篇 |
1995年 | 3553篇 |
1994年 | 3726篇 |
1993年 | 3348篇 |
1992年 | 3807篇 |
1991年 | 3792篇 |
1990年 | 3735篇 |
1989年 | 3539篇 |
1988年 | 3648篇 |
1987年 | 3546篇 |
1986年 | 3366篇 |
1985年 | 4430篇 |
1984年 | 4678篇 |
1983年 | 3905篇 |
1982年 | 4036篇 |
1981年 | 3953篇 |
1980年 | 3928篇 |
1979年 | 3890篇 |
1978年 | 4204篇 |
1977年 | 4113篇 |
1976年 | 4179篇 |
1975年 | 3854篇 |
1974年 | 3895篇 |
1973年 | 4060篇 |
1972年 | 2855篇 |
1971年 | 2380篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Development of an LC‐MS/MS method for determining the pharmacokinetics of clonidine following oral administration of Zhenju antihypertensive compound 下载免费PDF全文
Jing Qin Limin Wang Lihong Wu Jun Chen Teng Shen Yongji Li Limei Han Jianxin Wang 《Biomedical chromatography : BMC》2015,29(7):1068-1075
Zhenju antihypertensive compound (ZJAHC) is a combined Chinese–Western medicine formula including clonidine (CLO), hydrochlorothiazide (HCT), rutin, Chrysanthemum indicum extract and pearl powder. Compared with CLO preparations, ZJAHC shows improved activities and decreased adverse effects. It is believed that the side effects of CLO are caused by its high peak plasma concentration. Hence, study of the influence of ZJAHC on the pharmacokinetic behaviors of clonidine seems essential. In present study, the plasma concentrations of CLO were determined with a liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method. The MS/MS transitions monitored for clonidine and internal standard were 230.2 → 213.1 and 152.2 → 110.2, respectively. The analyte was quantified in a single run within 3 min. The pharmacokinetic study showed that the area under the plasma concentration–time curve of CLO in ZJAHC (60 µg/kg CLO) was similar to that of CLO‐HCT‐high (120 µg/kg CLO) but the peak concentration was much lower than that in CLO‐HCT‐high. ZJAHC could enhance the bioavailability without greatly increasing peak concentration of clonidine. This comprehensive effect of enhancing the bioavailability and avoiding the high peak plasma concentration for CLO might mainly result from the co‐contribution of Western medicine and traditional Chinese medicine (TCM), while the effect of TCM was stronger than that of Western medicine. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
43.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
44.
N. I. Golovina G. N. Nechiporenko G. G. Nemtsev G. P. Dolganova V. P. Roshchupkin D. B. Lempert G. B. Manelis 《Russian Journal of Applied Chemistry》2007,80(1):24-30
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined. 相似文献
45.
Demixing during film casting of blends of polystyrene, polymethylmethacrylate, and a symmetric diblock copolymer of styrene and methylmethacrylate is discussed. The concentration fluctuations in the homogeneous solutions were calculated in mean field approximation. The structures in the homogeneous and demixed solutions and in the dry films were measured by small-angle x-ray scattering, and the morphologies of the dry films were characterized by transmission electron microscopy. The structure of the dry blends is evidently already pre-formed in solution. 相似文献
46.
The lidar equation for the vibrational backscattering of neodymium laser radiation and its harmonics by hydrogen molecules
is solved numerically. Inclined paths in the atmosphere are investigated with the aim of selecting the transmitter wavelength
for detecting the lowest concentrations of hydrogen.
Zh. Tekh. Fiz. 68, 20–22 (January 1998) 相似文献
47.
G. Ch. Shushkevich 《Technical Physics》1998,43(7):743-748
The electrostatic problem for a thin, unclosed spherical shell and a torus is reduced to paired summation equations in the
Legendre polynomials by means of formulas relating the spherical and toroidal harmonic functions. The paired equations are
transformed to a Fredholm integral equation of the second kind. Formulas are obtained for computing the charges of the conductors
in the form of a series in a small parameter. The capacitance is computed for certain geometrical parameters of the conductors.
Zh. Tekh. Fiz. 68, 1–6 (July 1998) 相似文献
48.
We report on the first observation and studies of a weak delocalizing logarithmic temperature dependence of the conductivity,
which causes the conductivity of the 2D metal to increase as T decreases down to 16 mK. The prefactor of the logarithmic dependence is found to decrease gradually with density, to vanish
at a critical density n
c
, 2∼2×1012 cm−2, and then to have the opposite sign at n>n
c
,2. The second critical density sets the upper limit on the existence region of the 2D metal, whereas the conductivity at the
critical point, G
c
,2∼120e
2/h, sets an upper (low-temperature) limit on its conductivity.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 6, 497–501 (25 September 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
49.
50.