全文获取类型
收费全文 | 46310篇 |
免费 | 1540篇 |
国内免费 | 12篇 |
专业分类
化学 | 28216篇 |
晶体学 | 238篇 |
力学 | 761篇 |
综合类 | 1篇 |
数学 | 8781篇 |
物理学 | 9865篇 |
出版年
2023年 | 343篇 |
2022年 | 294篇 |
2021年 | 466篇 |
2020年 | 674篇 |
2019年 | 613篇 |
2018年 | 964篇 |
2017年 | 886篇 |
2016年 | 1699篇 |
2015年 | 1395篇 |
2014年 | 1347篇 |
2013年 | 3047篇 |
2012年 | 2874篇 |
2011年 | 2699篇 |
2010年 | 1799篇 |
2009年 | 1501篇 |
2008年 | 2365篇 |
2007年 | 2151篇 |
2006年 | 1910篇 |
2005年 | 1971篇 |
2004年 | 1702篇 |
2003年 | 1420篇 |
2002年 | 1227篇 |
2001年 | 949篇 |
2000年 | 951篇 |
1999年 | 660篇 |
1998年 | 510篇 |
1997年 | 431篇 |
1996年 | 577篇 |
1995年 | 409篇 |
1994年 | 483篇 |
1993年 | 440篇 |
1992年 | 468篇 |
1991年 | 394篇 |
1990年 | 444篇 |
1989年 | 360篇 |
1988年 | 367篇 |
1987年 | 329篇 |
1986年 | 320篇 |
1985年 | 446篇 |
1984年 | 410篇 |
1983年 | 324篇 |
1982年 | 325篇 |
1981年 | 342篇 |
1980年 | 278篇 |
1979年 | 272篇 |
1978年 | 270篇 |
1977年 | 260篇 |
1976年 | 277篇 |
1974年 | 250篇 |
1973年 | 263篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
41.
P. Kolář 《Czechoslovak Journal of Physics》1989,39(11):1317-1320
Conclusions The sets (3) and (4) of condensates have been compared using the QCD sum rules (2) with indefinite weight functions. A bad matching between both sets of condensates and experimental data has been obtained. The standard values (3) appear to be closer to data but some increase ofQ is necessary to improve the agreement. Only higher values ofm
0
2
could change the results of this analysis. It is interesting that negative values ofm
0
2
considerably improve the agreement with data; note that this quantity cannot be determined with a sufficient accuracy. We conclude that the QCD sum rules (2) cannot definitely determine a privileged set of condensates.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday. 相似文献
42.
Time structure of iodine laser pulse in the free running mode of operation was studied using the power amplifier of laser system PERUN as the laser oscillator. Two characteristic shapes of laser pulse correspond to different regimes of laser operation, the existence of which is ascribed to the critical concentration of I2 molecules. Simultaneously an additional chemical pumping was proved at least in the initial phase of photodissociation and in a late-time lasing after the end of flashlamps pumping light. 相似文献
43.
Zvonko Čerin 《Central European Journal of Mathematics》2005,3(1):1-13
We consider alternating sums of squares of odd and even terms of the Lucas sequence and alternating sums of their products.
These alternating sums have nice representations as products of appropriate Fibonacci and Lucas numbers. 相似文献
44.
Thermodynamic fluctuations in systems that are in nonequilibrium steady states are always spatially long ranged, in contrast to fluctuations in thermodynamic equilibrium. In the present paper we consider a fluid subjected to a stationary temperature gradient. Two different physical mechanisms have been identified by which the temperature gradient causes long-ranged fluctuations. One cause is the presence of couplings between fluctuating fields. Secondly, spatial variation of the strength of random forces, resulting from the local version of the fluctuation-dissipation theorem, has also been shown to generate long-ranged fluctuations. We evaluate the contributions to the long-ranged temperature fluctuations due to both mechanisms. While the inhomogeneously correlated Langevin noise does lead to long-ranged fluctuations, in practice, they turn out to be negligible as compared to nonequilibrium temperature fluctuations resulting from the coupling between temperature and velocity fluctuations. 相似文献
45.
46.
A. Baeza M. Fernández M. Herranz F. Legarda C. Miró A. Salas 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):321-326
We studied the effectiveness of potable water treatment processes that consist of the stages of coagulation-flocculation-decantation,
using iron-based coagulants, in eliminating gamma-emitting man-made radioisotopes of cesium, strontium, and americium from
two natural waters with different degrees of mineralization. The resulting decontamination was found to depend on the chemical
behavior of each of the radionuclides considered, on the pH at which the process of coagulation is carried out, and on the
concentration of the other stable cations present.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
47.
Sándor G?r?g 《Analytical sciences》2004,20(5):767-782
The development during the last 15 years and the state-of-the-art in the analysis of bulk steroid hormone drugs and hormone-like structures and pharmaceutical formulations made thereof are summarized. Other steroids (sterols, bile acids, cardiac glycosides, vitamins D) as well as biological-clinical aspects and pharmacokinetic and metabolic studies are excluded from this review. The state-of-the-art is summarized based on comparisons of monographs in the latest editions of the European Pharmacopoeia, United States Pharmacopoeia and the Japanese Pharmacopoeia. This is followed by sections dealing with new developments in the methodology for the fields of spectroscopic and spectrophotometric, chromatographic, electrophoretic and hyphenated techniques as well electroanalytical methods. The review is terminated by two problem-oriented sections: examples on impurity and degradation profiling as well as enantiomeric analysis. 相似文献
48.
49.
The influence of the sample orientation on the effective value of the hydrostatic piezoelectric coefficients d
h
(i)
of Sn2P2S6 crystals has been studied. The hydrostatic piezoelectric coefficients d
h
(1)
and d′
h
(3)
, were measured, d
h
(1)
=(244±3) pC/N and d′
h
(3)
=(92±1) pC/N. The hydrostatic piezoelectric coefficient d
h
(3)
for orthogonal axis system was calculated to be d
h
(3)
=(87±2) pC/N. The, optimal orientation of the sample has been found as (Xy l)−20°-cut. Maximal value of the effective hydrostatic piezoelectric coefficient d
h
(1)
equals 260 pC/N. Double rotated samples were also studied. The orientation of the samples insensitive to the pressure has
been found. The theoretical mean value of hydrostatic piezoelectric coefficient (d
h
)
mean
corresponding to randomly oriented Sn2P2S6 grains in a poled composite has been calculated to be (d
h
)
mean
=136 pC/N. 相似文献
50.
Máté Matolcsi 《Acta Mathematica Hungarica》2005,108(1-2):129-136
Summary He present work deals with estimations of the n-th linear polarization constant c(H)n of an n-dimensional real Hilbert space H. We provide some new lower bounds on the value of sup║y║=1 │1,y> ... n,y>│, where x1, ... ,xn are unit vectors in H. In particular, the results improve an earlier estimate of Marcus. However, the intriguing conjecture c(H) n= nn/2 remains open. 相似文献