全文获取类型
收费全文 | 17616篇 |
免费 | 1826篇 |
国内免费 | 3382篇 |
专业分类
化学 | 19457篇 |
晶体学 | 330篇 |
力学 | 394篇 |
综合类 | 99篇 |
数学 | 383篇 |
物理学 | 2161篇 |
出版年
2024年 | 45篇 |
2023年 | 150篇 |
2022年 | 312篇 |
2021年 | 536篇 |
2020年 | 730篇 |
2019年 | 692篇 |
2018年 | 548篇 |
2017年 | 779篇 |
2016年 | 910篇 |
2015年 | 820篇 |
2014年 | 955篇 |
2013年 | 1658篇 |
2012年 | 1332篇 |
2011年 | 1073篇 |
2010年 | 903篇 |
2009年 | 996篇 |
2008年 | 1037篇 |
2007年 | 1057篇 |
2006年 | 975篇 |
2005年 | 952篇 |
2004年 | 861篇 |
2003年 | 732篇 |
2002年 | 608篇 |
2001年 | 500篇 |
2000年 | 509篇 |
1999年 | 441篇 |
1998年 | 399篇 |
1997年 | 384篇 |
1996年 | 355篇 |
1995年 | 317篇 |
1994年 | 294篇 |
1993年 | 238篇 |
1992年 | 188篇 |
1991年 | 118篇 |
1990年 | 90篇 |
1989年 | 69篇 |
1988年 | 54篇 |
1987年 | 34篇 |
1986年 | 35篇 |
1985年 | 32篇 |
1984年 | 30篇 |
1983年 | 13篇 |
1982年 | 30篇 |
1981年 | 13篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Yu. A. Dobrovolsky P. Jannasch B. Lafitte N. M. Belomoina A. L. Rusanov D. Yu. Likhachev 《Russian Journal of Electrochemistry》2007,43(5):489-501
The 2000–2006 achievements in the field of synthesis, property examination, and application of proton-exchange membranes are reviewed on the basis of more than 120 papers. 相似文献
92.
S. V. Lindeman Yu. T. Struchkov I. A. Khotina V. N. Mikhailov A. L. Rusanov 《Russian Chemical Bulletin》1994,43(11):1873-1879
The crystal structure of 1,3,5-tris[4-(phenylethynyl)phenyl]benzene (1) has been investigated. Compound1 represents a model of the repeating unit of the most typical polyphenylene, which contains 1,3,5-trisubstituted benzene rings (chain centers) and acetylenic groups (complex-forming and cross-linking centers) in the main chain. The acetylene groups of neighboring molecules have a tendency to close mutual arrangement, which is favorable for their topochemical interaction. However, the relative conformational rigidity of molecules1 restricts not only the possibility of the optimal adjustment of the reactive sites of neighboring molecules to one another, but also hampers the close packing of molecules in the crystal, which contains channels filled by the solvent molecules (chloroform).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1986–1992, November, 1994.The work was carried out with the financial support of the International Science Foundation and the American Crystallographic Association. 相似文献
93.
Sokolova T. N. Grishin Yu. K. Timofeev I. V. Kartashov V. R. 《Russian Chemical Bulletin》1994,43(6):1044-1047
Regiochemistry and stereochemistry of the addition of mercury salts to benzobarrelene and tetrafluorobenzobarrelene have been studied in acetic acid and methanol. The effect of the substrate structure on the regiochemistry of the reaction is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1994. 相似文献
94.
S. S. Batsanov 《Russian Chemical Bulletin》1994,43(2):199-201
Experimental data are used to determine the atomic volumes and radii of the elements of subgroups IV–VIIA in the structures of metallic phases at high pressures. Metallic radii of nonmetals are compared with values based on Pauling and Goldschmidt calculations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 220–222, February, 1994. 相似文献
95.
96.
The rheological behavior of a mixture of two liquid-crystal polymers, hydroxypropyl cellulose and ethyl cellulose, in acetone solution is studied. The total polymer concentration in the solvent is held constant (40%) as the ratio of the two polymers is varied. The mixtures are anisotropic, isotropic, or biphasic (isotropic/anisotropic), depending on the concentration. Curves of viscosity vs shear rate for all the mixtures studied show three regions of viscosity, as described by Onogi and Asada for liquid-crystal polymers. The viscosity as a function of the weight ratio of the two polymers at constant shear rate exhibits deviations from additivity of viscosities of the two components at all concentrations. In mixtures of two polymers in the melt, deviations are also observed; the negative ones are attributed to phase separation and the positive ones to homogenous mixing (comparison with the phase diagram). All the mixtures studied (anisotropic, isotropic, or biphasic), show ranges of shear rates where the first normal-stress difference is negative, as is generally observed for anisotropic liquid-crystal polymers. It is concluded that the isotropic solutions become anisotropic under shear, as they are not far from the critical concentration. © 1994 John Wiley & Sons, Inc. 相似文献
97.
微分脉冲溶出伏安法同时测定食品中的锌铁锰 总被引:7,自引:4,他引:3
在1%乙二胺-0.1mol/L酒石酸钠-pH11.82 Britton—Robinson缓冲溶液体系中用微分脉冲溶出伏安法同时测定锌、铁、锰三种微量元素。它们的峰电位分别为-1184,-1392和-1456mV(vs.Ag/AgCl);线性范围分别为:0.001—0.015,0.005—0.05和0.04—0.7μg/mL,最低检出浓度分别为0.0007,0.0014和0.0193μg/mL。本法操作简便、准确、灵敏度较高,用于食品中这三种元素的分析,结果令人满意。 相似文献
98.
99.
100.
Huseyin Bekir Yildiz Jaime Castillo Dmitrii A. Guschin Levent Toppare Wolfgang Schuhmann 《Mikrochimica acta》2007,159(1-2):27-34
An amperometric biosensor for the detection of phenolic compounds was developed based on the immobilization of tyrosinase
within an Os-complex functionalized electrodeposition polymer. Integration of tyrosinase within the redox polymer assures
efficient catechol recycling between the enzyme and the polymer bound redox sites. The non-manual immobilization procedure
improves the reproducibility of fabrication process, greatly reduces the desorption of the enzyme from the immobilization
layer, and, most importantly prevents fast inactivation of the enzyme by its substrate due to fast redox cycling.
A two-layer sensor architecture was developed involving ascorbic acid oxidase entrapped within an electrodeposition polymer
in a second layer on top of the redox polymer/tyrosinase layer. Using this sensor architecture it was possible to eliminate
the current interference arising from direct ascorbate oxidation up to a concentration of 630 μM ascorbic acid. The effects
of the polymer thickness, the enzyme/polymer ratio, and the applied potential were evaluated with respect to optimal sensor
properties. The sensitivity of the optimized sensors for catechol was 6.1 nA μM−1 with a detection limit of 10 nM, and for phenol 0.15 nA μM−1 with a detection limit of 100 nM. 相似文献