全文获取类型
收费全文 | 201267篇 |
免费 | 2167篇 |
国内免费 | 612篇 |
专业分类
化学 | 112138篇 |
晶体学 | 2634篇 |
力学 | 8086篇 |
综合类 | 4篇 |
数学 | 19456篇 |
物理学 | 61728篇 |
出版年
2016年 | 2456篇 |
2015年 | 1758篇 |
2014年 | 2570篇 |
2013年 | 8041篇 |
2012年 | 5470篇 |
2011年 | 6838篇 |
2010年 | 4647篇 |
2009年 | 4573篇 |
2008年 | 6191篇 |
2007年 | 6363篇 |
2006年 | 6061篇 |
2005年 | 5542篇 |
2004年 | 5084篇 |
2003年 | 4561篇 |
2002年 | 4444篇 |
2001年 | 5887篇 |
2000年 | 4468篇 |
1999年 | 3577篇 |
1998年 | 2848篇 |
1997年 | 2882篇 |
1996年 | 2795篇 |
1995年 | 2626篇 |
1994年 | 2494篇 |
1993年 | 2388篇 |
1992年 | 2895篇 |
1991年 | 2791篇 |
1990年 | 2730篇 |
1989年 | 2713篇 |
1988年 | 2585篇 |
1987年 | 2620篇 |
1986年 | 2444篇 |
1985年 | 3315篇 |
1984年 | 3335篇 |
1983年 | 2751篇 |
1982年 | 2947篇 |
1981年 | 2904篇 |
1980年 | 2778篇 |
1979年 | 2978篇 |
1978年 | 3270篇 |
1977年 | 3140篇 |
1976年 | 3117篇 |
1975年 | 2887篇 |
1974年 | 2832篇 |
1973年 | 2868篇 |
1972年 | 1911篇 |
1971年 | 1583篇 |
1969年 | 1562篇 |
1968年 | 2044篇 |
1967年 | 2202篇 |
1966年 | 1990篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
91.
A. V. Anisimov A. A. Grishkyan Kh. A. Gaisina E. A. Viktorova 《Chemistry of Heterocyclic Compounds》1994,30(4):420-421
1-Allyloxy-2-allylthio-4-methylbenzene rearranges in NN-diethylaniline at 215°C with migration of allyloxy and allylthio groups to form 2,4-dimethyl-6-allyl-7-hydroxy-2,3dihydrobenzothiophene.M. V. Lomonosov State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 480–482, 1994. Original article submitted March 5, 1994. 相似文献
92.
By changing the conditions of the electrohydraulic treatment of aqueous plant heterodisperse systems comparatively high degradation
of the lignin component of plant tissue has been achieved. In addition to free monosaccharides, their reduced forms have been
detected in the aqueous phase.
Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89
14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 795–798, November–December, 1994. 相似文献
93.
Kh. T. Mirzaazimova S. D. Gusakova A. I. Glushenkova 《Chemistry of Natural Compounds》1994,30(5):555-558
The yields and fatty acid compositions of the free lipids and lipids weakly and strongly bound to proteins from seeds of cottonplant varieties resistant and susceptible to verticillium wilt have been determined and the changes in these indices in the seeds of the infected plants have been measured. It has been established that the seeds of healthy plants of the two varieties are similar in the qualitative compositions of the lipids and fatty acids but differ with respect the amounts of lipids in them bound with protein in different ways and with respect to the amounts of the individual fatty acids. The observed changes in the lipid and fatty-acid compositions depend on the degree of resistance of the variety to wilt. 相似文献
94.
G. N. Dalimova Kh. A. Abduazimov R. K. Rakhmanberdieva V. G. Gorokhova L. N. Petrushenko B. A. Babkin N. A. Koshilev 《Chemistry of Natural Compounds》1994,30(3):400-403
On the basis of the results of acid hydrolysis, chromatographic analysis of the hydrolysates, and a study of IR spectra, it has been established that the suspended particles liberated under the action of electrohydraulic shocks on heterodisperse water—plant systems consist of small fragments of the lignocarbohydrate complex of the plant tissue. 相似文献
95.
D. Kh. Khalikov M. G. Mukhiddinov M. G. Asoev V. A. Degtyarev 《Chemistry of Natural Compounds》1994,30(6):734-738
Some features of the kinetics of the hydrolysis of apple protopectin have been studied on the basis of an analysis of monosaccharide residues of the pectin substances and determinations of characteristic viscosity. It has been shown that the fine regulation of the physicochemical parameters of the hydrolysis of protopectin leads to the formation of pectin substances with different properties. 相似文献
96.
Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 891475.
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 679–680, September–October, 1994. 相似文献
97.
Literature information on the formation, chemical composition, and structural features of lignins of herbaceous plants for
1980–1992 is generalized and analyzed.
Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, Fax (3712) 62
73 48. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 160–177, March–April, 1994. 相似文献
98.
99.
Summary Experiments and simulations prove that correlation chromatography can greatly reduce the disadvantage of a non-linear response of the chromatographic column. A factor that has been accepted as being an important source of error in correlation or multiplex chromatography, has been shown not to be. Separations affected, improve dramatically when correlation chromatography is used, and a substantial amount of correlation noise only arises when there is a large difference in separation between a conventional chromatogram and a correlogram.A model has been developed for simulating these nonlinearities. It is shown that, especially for correlation chromatography, the simulation results match the practical measurements very well. 相似文献
100.
J. Escudi C. Couret H. Ranaivonjatovo J. Satge 《Coordination chemistry reviews》1994,130(1-2):427-480
During the last 10 years, several compounds of the type Ge=X (X = C, Ge, N, P, S) have been isolated as monomers. The stabilization of such derivatives, which are generally highly polymerizable, was achieved by using very bulky groups both on the germanium atom and on the heteroelement X. Conjugation (particularly in a few germenes and germaimines) and intramolecular or intermolecular coordination with oxygen or nitrogen, also contributes, in some cases, to the stabilization. The X-ray analyses of such compounds show a significant bond shortening of the double bond (8–10%) relative to the corresponding single bond and a planar or nearly planar germanium. These doubly bonded germanium derivatives are usually thermally stable but must be handled in an inert atmosphere because of their high sensitivity to oxygen and moisture; they are extremely reactive, much more than the corresponding carbon analogues. Nearly quantitative additions on the double bond have been observed with electrophiles and nucleophiles, and various types of cycloadditions also occur. Except in one case, a germylene behavior has not been observed, proving that such compounds retain their structural integrity in solution. 相似文献