全文获取类型
收费全文 | 100796篇 |
免费 | 6366篇 |
国内免费 | 5953篇 |
专业分类
化学 | 57713篇 |
晶体学 | 1399篇 |
力学 | 5767篇 |
综合类 | 549篇 |
数学 | 12390篇 |
物理学 | 35297篇 |
出版年
2023年 | 744篇 |
2022年 | 1325篇 |
2021年 | 1967篇 |
2020年 | 2416篇 |
2019年 | 2584篇 |
2018年 | 2951篇 |
2017年 | 2951篇 |
2016年 | 3571篇 |
2015年 | 2541篇 |
2014年 | 3662篇 |
2013年 | 5178篇 |
2012年 | 5338篇 |
2011年 | 5687篇 |
2010年 | 4605篇 |
2009年 | 4630篇 |
2008年 | 4872篇 |
2007年 | 4544篇 |
2006年 | 4165篇 |
2005年 | 3719篇 |
2004年 | 3240篇 |
2003年 | 2853篇 |
2002年 | 2803篇 |
2001年 | 2669篇 |
2000年 | 2101篇 |
1999年 | 1644篇 |
1998年 | 1537篇 |
1997年 | 1345篇 |
1996年 | 1283篇 |
1995年 | 1111篇 |
1994年 | 1190篇 |
1993年 | 1125篇 |
1992年 | 1077篇 |
1991年 | 1154篇 |
1990年 | 1127篇 |
1989年 | 1049篇 |
1988年 | 915篇 |
1987年 | 918篇 |
1986年 | 885篇 |
1985年 | 914篇 |
1984年 | 913篇 |
1983年 | 817篇 |
1982年 | 797篇 |
1979年 | 801篇 |
1978年 | 810篇 |
1977年 | 805篇 |
1976年 | 917篇 |
1975年 | 811篇 |
1974年 | 839篇 |
1973年 | 844篇 |
1972年 | 751篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
Gaineev A. M. Galkina I. V. Davletshin R. R. Davletshina N. V. Kuznetsov N. O. Grishaev D. Yu. Shulayeva M. P. Pozdeev O. K. 《Russian Journal of General Chemistry》2022,92(7):1208-1213
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a... 相似文献
42.
Pasyukov D. V. Chernenko A. Yu. Lavrentev I. V. Baydikova V. A. Minyaev M. E. Starovoytova O. A. Chernyshev V. M. 《Russian Chemical Bulletin》2022,71(5):993-1008
Russian Chemical Bulletin - The reaction of 1,4-disubstituted thiosemicarbazides with N,N-dimethylformamide dimethyl acetal afforded 1,4-disubstituted 1,2,4-triazolium-3-thiolates. Heating of the... 相似文献
43.
44.
以陶瓷基功能材料载体为研究对象,按照其生产工艺配方,研究了纤维种类(莫来石、氧化铝、氧化锆)及其添加量对陶瓷基功能材料载体性能的影响.在相同实验条件且不影响其功能化参数前提下,将其与未添加纤维的空白试样力学性能进行对比.结果表明,试样经1200℃烧成后,相比莫来石与氧化铝纤维增强的陶瓷基功能材料载体,氧化锆纤维的增强效果最好.当氧化锆纤维的添加量为0.8 wt;时,试样的吸水率和气孔率均较低,分别为2.0;、4.0;,相比空白对比试样抗折强度增强了42.4;. 相似文献
45.
Complex Study of the Spearhead Superficial Crust from Burial Mound no. 1 near Novosvobodnaya Village
Loboda A. Yu. Kolobylina N. N. Veligzhanin A. A. Zubavitchus Y. V. Tereshchenko E. Yu. Shishlina N. I. Yatsishina E. B. Kashkarov P. K. 《Crystallography Reports》2018,63(2):295-301
A complex study of a spearhead dated back to IV mill. BC from burial mound no. 1 near Novosvobodnaya village (collection of the State Historical Museum) and, in particular, the material of spearhead superficial crust has been performed. The elemental and phase composition of the metal of spearhead and the superficial crust on its surface have been determined by scanning electron microscopy, jointly with energydispersive X-ray microanalysis and X-ray phase analysis. A comparative analysis of the results of studying the spearhead superficial crust and similar crusts on other artifacts from the mounds near Novosvobodnaya village suggest natural origin of the crust on copper?arsenic artifacts.
相似文献46.
对硫化镉反蛋白石结构光子晶体薄膜进行了可控合成,用巯基乙酸修饰的纳米晶和P(St-MMA-SPMAP)高分子小球共组装,成功地构筑了反蛋白石结构并用于可见光光解水产氢。结果表明,在可见光(λ≥420 nm)照射下,Cd S-310反蛋白石结构薄膜的光解水产氢性能比硫化镉纳米颗粒提高了一倍。这主要是因为等级孔结构反蛋白石光子晶体特性对催化剂的光催化性能的提升:首先,反蛋白石的周期性结构增加了光子在材料中的传播,提高了催化剂对太阳光的利用率;同时,大孔孔壁是由纳米颗粒堆积而成的,在反应中提供了更多的反应活性位点;此外,孔结构有利于物质的传输和分子的吸附。 相似文献
47.
Dr. Zhoulong Fan Katherine L. Bay Dr. Xiangyang Chen Zhe Zhuang Han Seul Park Dr. Kap-Sun Yeung Prof. Dr. K. N. Houk Prof. Dr. Jin-Quan Yu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(12):4800-4807
A simple and efficient nitrile-directed meta-C−H olefination, acetoxylation, and iodination of biaryl compounds is reported. Compared to the previous approach of installing a complex U-shaped template to achieve a molecular U-turn and assemble the large-sized cyclophane transition state for the remote C−H activation, a synthetically useful phenyl nitrile functional group could also direct remote meta-C−H activation. This reaction provides a useful method for the modification of biaryl compounds because the nitrile group can be readily converted to amines, acids, amides, or other heterocycles. Notably, the remote meta-selectivity of biphenylnitriles could not be expected from previous results with a macrocyclophane nitrile template. DFT computational studies show that a ligand-containing Pd–Ag heterodimeric transition state (TS) favors the desired remote meta-selectivity. Control experiments demonstrate the directing effect of the nitrile group and exclude the possibility of non-directed meta-C−H activation. Substituted 2-pyridone ligands were found to be key in assisting the cleavage of the meta-C−H bond in the concerted metalation–deprotonation (CMD) process. 相似文献
48.
M. S. Fedoseev V. Yu. Gusev L. F. Derzhavinskaya V. E. Antipin R. V. Tsvetkov 《Polymer Science Series D》2018,11(1):39-46
The interaction of UP-643 epoxy-novolac resin with isomethyltetrahydrophthalic anhydride in the presence of the catalysts (azo-compounds of different structure) is studied. Latency of the catalysts is found. The possibility is shown of creating epoxy binders with a long lifetime (10–40 days) at room temperatures, cured at increased temperature up to heat-resistant polymers. 相似文献
49.
50.
Nonlinear Dynamics - Global dynamics of a flexible asymmetrical rotor resting on vibrating supports is investigated. Hamilton’s principle is used to derive the partial differential governing... 相似文献