全文获取类型
收费全文 | 2905篇 |
免费 | 60篇 |
国内免费 | 29篇 |
专业分类
化学 | 649篇 |
晶体学 | 8篇 |
力学 | 14篇 |
综合类 | 8篇 |
数学 | 66篇 |
物理学 | 84篇 |
综合类 | 2165篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 19篇 |
2020年 | 19篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 28篇 |
2015年 | 42篇 |
2014年 | 113篇 |
2013年 | 105篇 |
2012年 | 193篇 |
2011年 | 178篇 |
2010年 | 144篇 |
2009年 | 189篇 |
2008年 | 161篇 |
2007年 | 171篇 |
2006年 | 173篇 |
2005年 | 124篇 |
2004年 | 119篇 |
2003年 | 103篇 |
2002年 | 85篇 |
2001年 | 79篇 |
2000年 | 54篇 |
1999年 | 26篇 |
1998年 | 13篇 |
1997年 | 16篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1985年 | 51篇 |
1984年 | 29篇 |
1983年 | 29篇 |
1982年 | 24篇 |
1981年 | 129篇 |
1980年 | 104篇 |
1979年 | 24篇 |
1978年 | 63篇 |
1977年 | 50篇 |
1976年 | 39篇 |
1975年 | 50篇 |
1974年 | 38篇 |
1973年 | 25篇 |
1968年 | 18篇 |
1962年 | 5篇 |
1949年 | 4篇 |
排序方式: 共有2994条查询结果,搜索用时 718 毫秒
191.
谭春霞 《文山师范高等专科学校学报》2002,14(1):91-95
通过问卷调查的访谈,从七个方面调查了文山师专女大学生的现状,并针对女大学生贫困面大,学习基础较差,学习缺乏主动性等情况,提出了减轻经济压力,树立学习目标,加强思想政治教育和开设性别教育课程以发掘女性潜能,全方位促进女大学生成才的对策思考。 相似文献
192.
针对当前中小学体育教育的现状,同一些发达国家教育情况相比较,为适应新世纪中小学体育发展的需要,应加强中小学的体育师资队伍建设.文章探讨了新型体育教师的培养规格和对策,提出了适应未来社会发展的我国中小学体育教育专业培养目标的实现途径. 相似文献
193.
M. Aguilar 《Solid State Communications》1984,50(9):837-840
A study by means of the Electron-Paramagnetic-Resonance (EPR) technique of the valence states of the cobalt ion in oxidized and reduced BaTiO3 is presented. As a result, the identification of high-spin Co+ in reduced crystals was possible. The Co2+ centre is also discussed. 相似文献
194.
孙毅 《信阳师范学院学报(自然科学版)》1993,6(4):436-439
本文论述了综合进化论的形成和发展的几个主要阶段.着重介绍了综合进化论的发展现状和面临的挑战,并对其研究趋势进行了探讨. 相似文献
195.
Myron H. Miller DeLyle Eastwood Martha Schulz Hendrick 《Spectrochimica Acta Part B: Atomic Spectroscopy》1984,39(1):13-56
Experimental data and theoretical criteria are used to critically review existing models for analyte emission enhancement in the 3-electrode d.c. plasma (DCP). The analytical zone is characterized as a non-optically thin recombining plasma in partial thermodynamic equilibrium (PTE). Spectrochemical excitation the authors ascribe largely to: (1) argon resonance line radiative transport; (2) inversion of optically pumped argon states; (3) inversion of analyte populations by Franck-Condon collisions with argon; (4) energy cascading in analytes via a multitude of channels. Adding an easily ionized element (EIE): (1) induces additional resonance line radiative transfer; (2) raises electron densities in cooler, analyte-rich plasma margins; (3) locally increases argon optical absorption cross sections via Stark broadening; (4) redistributes ohmic heating. Coupling between the proposed mechanisms is non-linear. Relationships between radiative transfer and collisional redistribution and (1) background suppression by EIE and (2) analyte emission enhancement by helium are also examined. Similarities between DCP and inductively coupled plasma (ICP) excitation mechanisms are noted and practical implications are addressed. 相似文献
196.
The low temperature (1.3–20.0 K) heat capacity of the weak itinerant electron ferromagnet Sc3In was measured in magnetic fields up to ~ 10 T. The heat capacity peak observed around Tc = 6.0 K in zero field becomes smaller with increasing fields and at 9.98 T its magnetic entropy is ≈ 18% of the zero field value. Above Tc, the spin fluctuation contribution to the heat capacity, which is enhanced by the magnetic field at lower fields (?5 T), is quenched at higher fields (?5 T). This depression of the spin fluctuation contibution to the heat capacity by the high magnetic fields occurs at lower magnetic fields than had been considered possible heretofore. Our results suggest that the itinerant ferromagnetism is Sc3In is completely quenched at 12 T. 相似文献
197.
Doubly differential cross sections, in energy and angle, are reported for the electron transfer reaction between potassium and nitrogen dioxide in a crossed beam apparatus at relative collision energies between 2.7 and 30.8 eV. The formation of NO?2 in its ground 1A1 and excited 3B1 state has been observed. Theoretical consideration of these processes indicates that bond bending during the collision has a stronger influence on ion-pair formation than bond stretching. At the lower collision energies most of the excess energy is converted into internal energy of NO?2. 相似文献
198.
199.
M. Jaros 《Solid State Communications》1978,25(12):1071-1074
It is argued that the recent quantitative results concerning localized defects in semiconductors (e.g. GaAs) are consistent with the possibility of large Auger-type cross sections associated with recombination at these centers.It is proposed that many of the capture cross sections reported to be in the range 10?13–10?16cm2, which exhibit only weak temperature dependence, and which do not depend on carrier concentration, might be explained by this mechanism. 相似文献
200.
The crystal structure of bicyclo [3.3.3]undecane-1,5-diol has been determined. It is monoclinic, P21/c, a = 12.99(2), b = 14.16(2), c = 12.50(1)A,β = 112.42(2)°, with two independent molecules in the asymmetric unit. One of these is disordered, but the other has almost exact C3h symmetry and its conformation and precise molecular geometry agree well with previous calculations by molecular mechanics. The molecule shows considerable angle strain, having bridge angles in the range 118–121° 相似文献