全文获取类型
收费全文 | 196篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学 | 104篇 |
数学 | 44篇 |
物理学 | 49篇 |
出版年
2021年 | 5篇 |
2020年 | 11篇 |
2019年 | 2篇 |
2016年 | 2篇 |
2013年 | 4篇 |
2012年 | 6篇 |
2011年 | 2篇 |
2010年 | 2篇 |
2009年 | 3篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 10篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 12篇 |
2000年 | 4篇 |
1998年 | 2篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 9篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1968年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1958年 | 1篇 |
1955年 | 2篇 |
1933年 | 2篇 |
1901年 | 1篇 |
1890年 | 1篇 |
排序方式: 共有197条查询结果,搜索用时 359 毫秒
11.
Water-like lattice gases on the triangular and body-centered cubic lattices are investigated. Molecules may reside on the lattice sites in either of two possible orientations, a hydrogen bond being formed between molecules on neighboring sites if they have the proper orientation with respect to one another. For a range of chemical potential at sufficiently low temperatures, the models are shown to have an ordered phase consisting of an open, hydrogen-bonded, icelike structure. The models are shown to be transitionfree at sufficiently high temperature, indicating the existence of a critical point.Research supported in part by the U.S. National Science Foundation, Grant CHE-7726177, and by The Robert A. Welch Foundation, Grant P-446. 相似文献
12.
13.
14.
F. Heilmann 《Fresenius' Journal of Analytical Chemistry》1933,92(3-4):106-107
Ohne Zusammenfassung 相似文献
15.
16.
Jerald K. Rasmussen Steven M. Heilmann Larry R. Krepski Howell K. Smith Alan R. Katritzky Kumars Sakizadeh 《Journal of polymer science. Part A, Polymer chemistry》1986,24(11):2739-2747
The reaction of bisazlactones (2-oxazolin-5-ones) with primary diamines containing additional secondary or tertiary amine functionality (e.g., diethylenetriamine, triethylenetetramine, or N-methyliminobispropylamine) readily produces polyamides which serve as precursors to a new class of heterocyclic polymers. Thermal cyclodehydration takes place under relatively mild conditions (180–200°C) to produce water-soluble polymers containing the 2-imidazolin-5-one heterocycle. Model reactions have been studied to verify this mode of cyclization and confirm the proposed polymer structure. 相似文献
17.
The dienylic chlorides 1–5 react with isobutene in the presence of zinc chloride/ether in dichloromethane to give the acyclic adducts 6–10 in 64–91% yield. The orientation effects are in contrast to the predictions of perturbational molecular orbital theory and can be explained on the basis of steric effects. 相似文献
18.
19.
Background
Pentachloronitrobenzene (PCNB) and hexachlorobenzene (HCB) are highly toxic and widespread in every environmental compartment. Some of metabolic products such as amino/nitro containing chlorinated aromatic compounds can be determined by gas chromatography coupled with electron capture detector (GC-ECD). However, it is difficult to identify some of chlorophenolic and chloroquinolic intermediates produced from PCNB and HCB by the above mentioned technique. Therefore, for analysis of these compounds and their metabolites, we have developed a high performance liquid chromatography (HPLC) based method.Results
The extraction of PCNB and HCB from soil and minimal salt medium was carried out with ethyl acetate and hexane respectively with good recoveries (98% for PCNB and 97% for HCB). The validation of the proposed extraction and HPLC method was done by analysis of PCNB and HCB biodegradation and their metabolites identification from anaerobic enriched soil samples.Conclusion
A rapid, sensitive and simple HPLC based analytical method was developed for the analysis of PCNB, HCB and their possible intermediates. 相似文献20.
K. Böckmann H.G. Heilmann U. Idschok P. Kobe F. Selonke V. Blobel H. Fesefeldt B. Hellwig D. Mönkemeyer H. Franz P. Freund W. Schrankel 《Nuclear Physics B》1974,81(1):45-60
The reaction pp → nucleon + nucleon + pion at 12 and 24 GeV/c is analyzed in terms of the isospin amplitudes for the production of the (Nπ) system. The energy dependence of the amplitude is weak, while the contribution shows the strong energy dependence known from meson exchange reactions. The slope parameter B of the dσ/dt′ distributions of the contribution is a strong function of the (Nπ) mass, decreasing sharply from about 12 GeV?2 at threshold to about 4 GeV?2 above 1700 MeV. Comparing our results for the cross section with those of similar investigations in πp and Kp reactions, we find that factorisation is valid within experimental errors. The results support the conclusion that the contribution is dominated by diffraction dissociation of the proton. 相似文献