全文获取类型
收费全文 | 1491篇 |
免费 | 74篇 |
国内免费 | 141篇 |
专业分类
化学 | 792篇 |
晶体学 | 36篇 |
力学 | 57篇 |
综合类 | 23篇 |
数学 | 121篇 |
物理学 | 677篇 |
出版年
2022年 | 30篇 |
2021年 | 31篇 |
2020年 | 42篇 |
2019年 | 41篇 |
2018年 | 50篇 |
2017年 | 56篇 |
2016年 | 42篇 |
2015年 | 41篇 |
2014年 | 56篇 |
2013年 | 57篇 |
2012年 | 64篇 |
2011年 | 81篇 |
2010年 | 82篇 |
2009年 | 72篇 |
2008年 | 94篇 |
2007年 | 96篇 |
2006年 | 96篇 |
2005年 | 63篇 |
2004年 | 61篇 |
2003年 | 46篇 |
2002年 | 47篇 |
2001年 | 49篇 |
2000年 | 38篇 |
1999年 | 25篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 19篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1984年 | 11篇 |
1983年 | 16篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1975年 | 9篇 |
1974年 | 19篇 |
1973年 | 12篇 |
1972年 | 12篇 |
1971年 | 24篇 |
1970年 | 10篇 |
1969年 | 11篇 |
1968年 | 9篇 |
1967年 | 6篇 |
排序方式: 共有1706条查询结果,搜索用时 109 毫秒
31.
32.
I. E. Baranov S. A. Demkin V. K. Zhivotov I. I. Nikolaev V. D. Rusanov N. G. Fedotov 《High Energy Chemistry》2004,38(3):191-195
A method for enhancing the hydrocarbon pyrolysis process by introducing atomic hydrogen into the reaction medium from an arcjet plasma source was considered. It was shown that hydrogen atoms could effectively be introduced by mixing under low pressure. The atomic hydrogen–stimulated methane pyrolysis process was experimentally studied in a continuous stirred reactor with a plasma plume. When hydrogen atoms were present in the plasma jet, the amount of the valuable product increased by a factor of two. 相似文献
33.
用(RCp)2MCl2和(RCp)TiCl3(R=H,Me;M=Ti,Zr)分别与具有生物活性的2-甲氧基-5-氟尿嘧啶、2-甲硫基-5-氟尿嘧啶在甲苯溶剂中110℃下反应,合成了20个未见报道的(RCp)·M(Opm)2Cl、(RCp)2M(OPm)Cl和(RCp)M(OPm)Cl2(OPm=2-甲氧基-5-氟尿嘧啶基,2-甲硫基-5-氟尿嘧啶基)型钛锆配合物,这些配合物均经元素分析、1HNMR、IR光谱鉴定.初步动物试验表明,配合物1、4、11、14对小白鼠移植性艾氏腹水场的抑制作用居首,而配合物2、3、5、6、12、13、15、16次之,其它锆配合物几乎没有抑制作用。 相似文献
34.
Novel approximate methods for calculating the vibrational structure of the electronic spectra of polyatomic molecules—a method
for the direct calculation of the overlap integrals of vibrational wave functions for the electronic states involved in a
transition and a variational method for the solution of the vibrational problem for the excited states—are discussed. The
methods are based on the consideration of the displacement and entanglement of normal coordinates, the quasiorthogonality
of the Dushinsky transformation, and the classification of the states by total vibrational quantum numbers. Matrix perturbation
theory is employed. It is shown that the accuracy of these methods compares well with the accuracy of the available “exact”
techniques (the errors are ∼1 cm−1 for frequency and 10% for relative intensity). At the same time, calculations by the new methods are performed more than
two orders of magnitude faster than by the previously known methods.
K. A. Timiryazev Agricultural Academy, Moscow. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 2, pp. 217–230, March–April, 1995.
Translated by I. Izvekova 相似文献
35.
It has been shown that 1,3-thiazolidine-2,4-dione and 1,3-oxazolidine-2,4-dione react with hydrazine with a rearrangement of the ring to form a triazolinone ring. In each case, the reaction begins with the formation of an ionic adduct of hydrazine with the azolidinedione. On heating, the adduct undergoes decyclization (water catalyzes the process). The further course of the reaction is governed by the temperature and pH of the medium, which determine whether dehydration of the intermediate product with the formation of a triazolinone ring (in acid media) or rearrangement into a 1-acylsemicarbazide (at elevated temperatures) predominates. The influence of substituents in the thiazolidinone ring on the course of the reaction has been studied.For Communication I, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 991–996, July, 1970. 相似文献
36.
本文运用PM3算法计算得到氯酚(CPs)的分子结构参数,并结合光解速率进行PLS分析,建立了速率与量子化参数之间的关系模型,模型的Q2cum分别为0.8776和0.9545(>0.5),具有良好的预测能力。研究结果表明,参数Ehomo、Elumo Ehomo、Elumo、N、Mw、Elumo-Ehomo、(Elumo-Ehomo)2是决定CPs光解速率的主要因素;CPs的光解速率随Ehomo、Elumo Ehomo、Elumo、Elumo-Ehomo、(Elumo-Ehomo)2的增大而增大,随N、Mw的增大而减小。 相似文献
37.
The force fields, in-plane vibrations, and relative intensities of Raman spectra have been calculated and analyzed for the N1H and N3H tautomers of imidazole, imidazolium cation, and their model structures. The results obtained for the isolated state of imidazole correspond to the intramolecular mechanism of proton transfer. 相似文献
38.
万古霉素和替考拉宁都属于糖肽类的大环抗生素,具有立体的环状结构和多个手性中心,是两种常见的手性识别材料,广泛应用于对映体的色谱手性分离分析。该文以万古霉素和替考拉宁为手性选择剂,哌嗪为单体,4,4'-二苯基甲烷二异氰酸酯(MDI)、1,6-己二异氰酸酯(HDI)和2,4-甲苯二异氰酸酯(TDI)为交联剂,通过界面聚合反应形成网状层包裹硅胶载体的方法制得6种高效液相色谱手性固定相,用于分离外消旋化合物,并与MDI直接交联万古霉素和替考拉宁在硅胶表面所得固定相进行了比较。结果表明,利用"网包法"和直接交联法制备的手性柱与商品万古霉素和替考拉宁柱之间具有互补性,均对不同的外消旋体有不同程度的拆分。 相似文献
39.
G. V. Pavlinsky A. Yu. Dukhanin E. O. Baranov A. Yu. Portnoy 《Journal of Analytical Chemistry》2006,61(7):654-661
The theory of X-ray fluorescence generation in elements with a low atomic number Z is extended to the case of host matrices with high Z. The total contribution of the selective excitation effects is estimated with regard to the cascade K-L transitions. The influence of the elemental composition of the matrix and the excitation conditions on the X-ray fluorescence intensity of the elements in study is assessed. The accuracy of the model of X-ray fluorescence generation in the low-atomic-number elements is confirmed by the agreement of the experimental and calculated intensities of carbon in various carbon-containing compounds. 相似文献
40.
D. S. Baranov N. Y. Chabrov V. A. Filipov A. A. Ivanilov P. V. Ivanov V. I. Konyushko V. M. Korablev V. A. Korotkov V. A. Krupnov V. V. Makeev A. G. Myagkov A. Yu. Polyarush A. A. Sokolov E. P. Kuznetsov H. -J. Grabosch H. H. Kaufmann U. Krecker R. Nahnhauer S. Nowak H. Vogt 《Zeitschrift fur Physik C Particles and Fields》1984,21(3):189-196
We present data on the multiplicity structure of inclusive charged hadron production in charged current neutrino and antineutrino freon interactions in the energy range 3–30 GeV resulting from an experiment with the bubble chamber SKAT. Average multiplicities, dispersions and correlation coefficients are investigated. Furthermore, KNO-scaling is studied and average net charges are calculated in different kinematical regions. Our data are compared with results from \(\begin{array}{*{20}c} {( - )} \\ v \\ \end{array} \) -interactions on an isoscalar target of “free” nucleons to study the influence of nuclear effects. 相似文献