全文获取类型
收费全文 | 9481篇 |
免费 | 1487篇 |
国内免费 | 1214篇 |
专业分类
化学 | 6790篇 |
晶体学 | 91篇 |
力学 | 414篇 |
综合类 | 102篇 |
数学 | 1046篇 |
物理学 | 3739篇 |
出版年
2024年 | 23篇 |
2023年 | 202篇 |
2022年 | 348篇 |
2021年 | 355篇 |
2020年 | 399篇 |
2019年 | 385篇 |
2018年 | 322篇 |
2017年 | 320篇 |
2016年 | 454篇 |
2015年 | 446篇 |
2014年 | 563篇 |
2013年 | 675篇 |
2012年 | 851篇 |
2011年 | 821篇 |
2010年 | 555篇 |
2009年 | 506篇 |
2008年 | 636篇 |
2007年 | 610篇 |
2006年 | 502篇 |
2005年 | 461篇 |
2004年 | 314篇 |
2003年 | 255篇 |
2002年 | 242篇 |
2001年 | 217篇 |
2000年 | 226篇 |
1999年 | 188篇 |
1998年 | 180篇 |
1997年 | 149篇 |
1996年 | 164篇 |
1995年 | 147篇 |
1994年 | 111篇 |
1993年 | 98篇 |
1992年 | 80篇 |
1991年 | 63篇 |
1990年 | 63篇 |
1989年 | 40篇 |
1988年 | 37篇 |
1987年 | 32篇 |
1986年 | 26篇 |
1985年 | 35篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1962年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
R. Bernabei P. Belli F. Cappella R. Cerulli C. J. Dai A. d’Angelo H. L. He A. Incicchitti H. H. Kuang X. H. Ma F. Montecchia F. Nozzoli D. Prosperi X. D. Sheng Z. P. Ye 《The European Physical Journal C - Particles and Fields》2009,62(2):327-332
In this paper a new search for non-Paulian nuclear processes, i.e. processes normally forbidden by the Pauli Exclusion Principle
(PEP), is presented. It has been carried out at the Gran Sasso National Laboratory of the INFN by means of the highly radiopure
DAMA/LIBRA set-up (sensitive mass of about 250 kg highly radiopure NaI(Tl)). In particular, a new improved upper limit for
the spontaneous non-Paulian emission rate of protons with energy E
p
≥ 10 MeV in 23Na and 127I has been obtained: 1.63 × 10−33 s−1 (90% C.L.). The corresponding limit on the relative strength (δ
2) for the searched non-Paulian transition is δ
2≲(3–4)×10−55 (90% C.L.). Moreover, PEP-violating electron transitions in iodine atoms have also been investigated. Lifetimes shorter than
4.7×1030 s are excluded at 90% C.L.; this allows us to derive the limit δ
e
2<1.28×10−47 (90% C.L.). This latter limit can also be related to a possible finite size of the electron in composite models of quarks
and leptons providing superficial violation of the PEP; the obtained upper limit on the electron size is r
0<5.7×10−18 cm (energy scale of E≳3.5 TeV). 相似文献
82.
In this study, the application of ultrasound-assisted extraction (UAE) method was shown to be more efficient in extracting anti-tumor bufadienolides (bufalin, cinobufagin and resibufogenin) from important animal medicine of ChanSu than the maceration extraction (ME) and soxhlet extraction (SE) method. The effects of ultrasonic variables including extraction solvent, solvent concentration, solvent to solid ratio, ultrasound power, temperature, extraction time and particle size on the yields of three bufadienolides were investigated. The optimum extraction conditions found were: 70% (v/v) methanol solution, solvent to solid ratio of 10ml/g, ultrasound power of 125W, temperature of 20°C, extraction time of 20min and particle size of 60-80 mesh. The extraction yields of bufalin, cinobufagin and resibufogenin were 43.17±0.85, 52.58±1.12, 137.70±2.65mg/g, respectively. In order to achieve a similar yield as UAE, soxhlet extraction required 6h and maceration extraction required much longer time of 18h. The results indicated that UAE is an alternative method for extracting bufadienolides from ChanSu. 相似文献
83.
The intensity and position of the coupling points in high birefringence(Hi-Bi)fibers can be detected effectively using distributed polarization coupling(DPC)detection.The detection sensitivity can decrease due to mechanical vibration disturbance and environment noise.Thus,a method based on empirical mode decomposition is proposed to detect weak mode coupling points.The simulation and experimental results illustrate that the proposed method can suppress the noise effectively and improve sensitivity significantly.The method can identify coupling points as weak as-60 dB embedded in noise automatically and effectively.The algorithm is applicable for DPC,and the experimental sensitivity is improved by 10 dB. 相似文献
84.
We present a theoretical calculation of the dependence of reflectivity Rpp of the improved fully leaky waveguide geometry,which comprises pyramid,matching fluid,and strongly anchored hybrid aligned nematic liquid crystal(NLC) cell on the internal angle.The calculation is based on the multi layer optical theory and the elastic theory of liquid crystals.For different sums of flexoelectric coefficients e11 and e33,the curve of Rpp moves a distance to the left or the right relative to the case of ignoring the flexoelectric effect and the distance of the movement varies with different flexoelectric coefficients.Consequently,the sum of flexoelectric coefficients can be explored by measuring the distance of the movement. 相似文献
85.
N. N. Koval Yu. F. Ivanov A. P. Laskovnev V. V. Uglov N. N. Cherenda Yu. A. Kolubaeva Ye. A. Markova A. D. Teresov P. V. Moskvin 《Russian Physics Journal》2012,54(9):1024-1033
A film/substrate system has been treated with a submillisecond high-intensity electron beam. Examinations have shown that
the electron-beam treatment of the film/substrate system resulted in alloying of the surface layer of the material throughout
the melt which was accompanied by the formation of nanodimensional phases. 相似文献
86.
87.
88.
Approximate solution for the Klein Gordon-Schrdinger equation by the homotopy analysis method 下载免费PDF全文
The Homotopy analysis method is applied to obtain the approximate solution of the Klein--Gordon--Schr?dinger equation. The Homotopy analysis solutions of the Klein--Gordon--Schr?dinger equation contain an auxiliary parameter which provides a convenient way to control the convergence region and rate of the series solutions. Through errors analysis and numerical simulation, we can see the approximate solution is very close to the exact solution. 相似文献
89.
The carrier-envelope phase of the pulse train emitted by a 10-fs mode-locked laser has been stabilized such that carrier-envelope phase coherence is maintained for at least 150 s (measurement limited). The phase coherence time was measured independently of the feedback loop. 相似文献
90.
Relationship between positron bulk lifetime and lattice constants-research on NaCl-type crystals 下载免费PDF全文
The positron lifetimes of some compounds with NaCl-type crystal structure are calculated with the method of atomic superposition approximation (ATSUP) based on the theories of local-density-approximation (LDA) and generalgradient-approximation (GGA).The systematical results are fitted to a curve as a function of lattice constants.The positron bulk lifetimes of some other compounds with NaCl-type crystal structure,which are deduced from the systematical results,are in agreement with the experimental results given in other literature. 相似文献