全文获取类型
收费全文 | 27284篇 |
免费 | 1609篇 |
国内免费 | 4265篇 |
专业分类
化学 | 26799篇 |
晶体学 | 549篇 |
力学 | 175篇 |
综合类 | 150篇 |
数学 | 1098篇 |
物理学 | 4387篇 |
出版年
2024年 | 36篇 |
2023年 | 230篇 |
2022年 | 537篇 |
2021年 | 514篇 |
2020年 | 590篇 |
2019年 | 1527篇 |
2018年 | 692篇 |
2017年 | 1506篇 |
2016年 | 938篇 |
2015年 | 846篇 |
2014年 | 1077篇 |
2013年 | 2314篇 |
2012年 | 1657篇 |
2011年 | 1773篇 |
2010年 | 1253篇 |
2009年 | 1514篇 |
2008年 | 1707篇 |
2007年 | 1786篇 |
2006年 | 1662篇 |
2005年 | 1484篇 |
2004年 | 1490篇 |
2003年 | 1193篇 |
2002年 | 1010篇 |
2001年 | 838篇 |
2000年 | 828篇 |
1999年 | 604篇 |
1998年 | 564篇 |
1997年 | 477篇 |
1996年 | 390篇 |
1995年 | 403篇 |
1994年 | 284篇 |
1993年 | 259篇 |
1992年 | 257篇 |
1991年 | 180篇 |
1990年 | 114篇 |
1989年 | 102篇 |
1988年 | 79篇 |
1987年 | 48篇 |
1986年 | 45篇 |
1985年 | 50篇 |
1984年 | 38篇 |
1983年 | 20篇 |
1982年 | 42篇 |
1981年 | 42篇 |
1980年 | 24篇 |
1979年 | 47篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
本文介绍了EltctronicWorkbench软件和计算机虚拟仪器系统,采用计算机模拟仿真技术对电子线路实验加以辅助设计和探索。 相似文献
32.
Magnetic Properties of the Cobaltates Na6CoS4, Na6CoSe4, and K6CoS4 The alkali metal cobalt chalcogenides Na6CoS4, Na6CoSe4, and K6CoS4 crystallize in the space group P63mc with Z = 4. The structure is characterized by isolated [CoX4]-tetrahedra. The magnetic susceptibilities show Curie-Weiss behaviour. The deviations at low temperatures are caused by antiferromagnetic interactions. The magnetic moments are discussed with regard to ligand-field parameters. 相似文献
33.
许多乙酰芳胺类化合物具有优异的生物活性,例如除草剂苯噻草胺,可抑制细胞生长和分裂,防除稻田中禾本科杂草[1];杀菌剂甲霜灵可防治作物霜霉病[2]。本文将具有多种生物活性的嘧啶基团引入到乙酰芳胺结构中[3],合成下列10个未见文献报道的标题化合物Ⅰ,通... 相似文献
34.
The response to Hg(II) of a thin all-solid-state Te-doped silver chalcogenide membrane, described by the general formula Ag2 + δSe1 − xTex, which has been electrochemically prepared following a previously proposed approach, has been investigated. The kinetics of formation of the membrane's secondary dynamic response to Hg(II) has been successfully combined with the precise timing and transient signal, typical for flow-injection (FI) measurements, in developing a sensitive and reliable mercury FI detector. Under optimized stream conditions it exhibits a linear Nernstian response, with a double slope of the calibration graph of 59 mV dec−1, over the mercury(II) concentration range 10−6 − 10−3 M, the typical sample throughput amounting to about 70 samples per hour. The observed chemical amplification of the signal is due to the specificity of the processes dominating the initial step in formation of the steady-state signal of the membrane to mercury. The analytical performance of the Hg(II) FI detector, as regards sensitivity, reproducibility, selectivity and long-term stability has been thoroughly investigated. The exact procedure for membrane electrodeposition is given and the potential of the proposed approach as a cost-effective way for preparing chalcogenides of unique structure and properties has been outlined in the above context. 相似文献
35.
36.
37.
38.
Yi-Shiue Lin 《Applied Surface Science》2006,252(16):5892-5899
Dissociative adsorption of CCl4 on TiO2 at 35 °C has been studied by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electron spin resonance. CCl4 decompose to form CO, CO2, and CO3 on the surface, at such a low temperature, in which CO2 formation is not from CO oxidation on TiO2, but CO3 can be produced by CO and CO2 adsorption. The Cl generated from CCl4 decomposition is left on the surface and bonded to titanium ions. Mineralization of CCl4 on TiO2 involves the lattice oxygens. Thermodynamical driving force and possible reaction routes for CO and CO2 formation in the CCl4 decomposition on TiO2 are discussed. 相似文献
39.
40.
V. N. Sorokoumov S. N. Morozkina I. A. Balova 《Chemistry of Heterocyclic Compounds》2006,42(5):615-624
An investigation of the reaction of 1-lithio-1,3-diynes, generated in situ, with nitriles has been carried out. In the case
of aromatic nitriles 1-arylalk-1-ene-3,5-diynylamines are formed, which undergo dimerization and cyclization on isolation,
giving 3-(alka-1,3-diynyl)-4-(alk-2-ynyl)-2,6-diarylpyridines. The effect of the nature of the substituent in the benzonitrile
molecule on the selectivity of the reaction and the yield of the products has been determined. A scheme is proposed for the
conversions and the structures of the intermediates have been established.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 701–710, May, 2006. 相似文献