全文获取类型
收费全文 | 30535篇 |
免费 | 2811篇 |
国内免费 | 1919篇 |
专业分类
化学 | 17111篇 |
晶体学 | 531篇 |
力学 | 1739篇 |
综合类 | 100篇 |
数学 | 2809篇 |
物理学 | 12975篇 |
出版年
2024年 | 30篇 |
2023年 | 329篇 |
2022年 | 614篇 |
2021年 | 652篇 |
2020年 | 721篇 |
2019年 | 734篇 |
2018年 | 737篇 |
2017年 | 628篇 |
2016年 | 1020篇 |
2015年 | 894篇 |
2014年 | 1169篇 |
2013年 | 1848篇 |
2012年 | 2203篇 |
2011年 | 2450篇 |
2010年 | 1727篇 |
2009年 | 1713篇 |
2008年 | 1940篇 |
2007年 | 1828篇 |
2006年 | 1763篇 |
2005年 | 1480篇 |
2004年 | 1256篇 |
2003年 | 1024篇 |
2002年 | 1048篇 |
2001年 | 1288篇 |
2000年 | 888篇 |
1999年 | 795篇 |
1998年 | 576篇 |
1997年 | 560篇 |
1996年 | 456篇 |
1995年 | 377篇 |
1994年 | 346篇 |
1993年 | 270篇 |
1992年 | 284篇 |
1991年 | 258篇 |
1990年 | 213篇 |
1989年 | 176篇 |
1988年 | 136篇 |
1987年 | 117篇 |
1986年 | 105篇 |
1985年 | 111篇 |
1984年 | 76篇 |
1983年 | 53篇 |
1982年 | 41篇 |
1981年 | 45篇 |
1980年 | 26篇 |
1978年 | 19篇 |
1976年 | 31篇 |
1975年 | 33篇 |
1974年 | 27篇 |
1973年 | 24篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
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
152.
We propose general variational inclusion problems which are slightly different from corresponding problems considered in several recent papers in the literature and show that they are advantageous. Sufficient conditions for the solution existence are established. As applications we derive consequences for several special cases of variational inclusion problems, quasioptimization problems, equilibrium problems and implicit variational inequalities and show that they improve the results of some recent existing papers. 相似文献
153.
Dong Hwan Choi Yoshio Katakura Rieko Matsuda Yuzuru Hayashi Masato Hirobe Yasuhiro Goda Kazuaki Ninomiya Suteaki Shioya 《Analytical sciences》2007,23(2):215-218
The mathematical model for predicting the precision, limit of detection (LOD) and range of quantitation (ROQ) in a competitive enzyme-linked immunosorbent assay (ELISA) proposed by Hayashi et al. (Anal. Chem., 2004, 76, 1295) was validated. The model describes the relative standard deviation (RSD) of concentration estimates by the RSDs of pipetting volumes of analyte, enzyme-conjugated antigen, antibody and substrate solutions, and the standard deviation (SD) of inherent absorbances between the wells in an ELISA plate. For 6 kinds of direct competitive ELISA kits, the LOD and ROQ predicted by the model agreed well with those obtained by experiments with real samples. It was also confirmed that the model is applicable to the prediction of uncertainty that depends on the pipetting error of the viscous antiserum solution. The model was demonstrated to be useful for estimating the LOD and ROQ of competitive ELISA. 相似文献
154.
155.
The present report describes a method suitable for the indirect assay of hydroxyl radical (OH.), which is likely to be produced during reperfusion of ischemic myocardium. Isolated rat heart perfused by the Langendorff technique was subjected to 30 min of ischemia, followed by 30 min of reperfusion. Salicylic acid (2 mM) was added to the perfusion circuit to trap any OH. radical generated during the experiment. 2,5- and 2,3-dihydroxybenzoic acids (hydroxylated products of salicylic acid) were identified by authentic standards as well as by pure OH.-generating system using high-performance liquid chromatography with electrochemical detection. In addition to serving as a chemical trap for the detection of OH., salicylate attenuated myocardial reperfusion injury as evidenced by reduced formation of creatine kinase, decreased lipid peroxidation, and improved myocardial contractile functions during reperfusion. These results thus provide direct evidence for the presence of OH. in heart and link it to the myocardial reperfusion injury. 相似文献
156.
Z.J. Liu H.H. Long W.C. Ye X.X. Zou Z.L. Qin E.P. Li J.S. Chen 《Journal of magnetism and magnetic materials》2006
In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated. 相似文献
157.
The general relation between the standard expansion coefficients and the beta function for the QCD coupling is exactly derived in a mathematically strict way. It is accordingly found that an infinite number of logarithmic terms are lost in the standard expansion with a finite order, and these lost terms can be given in a closed form. Numerical calculations, by a new matching-invariant coupling with the corresponding beta function to four-loop level, show that the new expansion converges much faster. 相似文献
158.
159.
Yunshan Dong 《Applied Surface Science》2006,252(14):5057-5062
A series of Zr-Si-N composite films with different Si contents were synthesized in an Ar and N2 mixture atmosphere by the bi-target reactive magnetron sputtering method. These films’ composition, microstructure and mechanical properties were characterized by energy dispersive spectroscopy, X-ray diffraction, scanning electron microscopy, atomic force microscopy and nanoindentation. Experimental results revealed that after the addition of silicon, Si3N4 interfacial phase formed on the surface of ZrN grains and prevented them from growing up. Zr-Si-N composite films were strengthened at low Si content with the hardness and elastic modulus reaching their maximum values of 29.8 and 352 GPa at 6.2 at% Si, respectively. With a further increase of Si content, the crystalline Zr-Si-N films gradually transformed into amorphous, accompanied with a remarkable fall of films’ mechanical properties. This limited enhancement of mechanical properties in the Zr-Si-N films may be due to the low wettability of Si3N4 on the surface of ZrN grains. 相似文献
160.
Wengu Chen Yixin Lai 《分析论及其应用》2006,22(2):195-200
Let μ be a Borel measure on Rd which may be non doubling. The only condition that μ must satisfy is μ(Q) ≤ col(Q)n for any cube Q () Rd with sides parallel to the coordinate axes and for some fixed n with 0 < n ≤ d. The purpose of this paper is to obtain a boundedness property of fractional integrals in Hardy spaces H1 (μ). 相似文献