全文获取类型
收费全文 | 62521篇 |
免费 | 10390篇 |
国内免费 | 3936篇 |
专业分类
化学 | 57473篇 |
晶体学 | 688篇 |
力学 | 1801篇 |
综合类 | 245篇 |
数学 | 5382篇 |
物理学 | 11258篇 |
出版年
2023年 | 253篇 |
2022年 | 586篇 |
2021年 | 775篇 |
2020年 | 1765篇 |
2019年 | 3108篇 |
2018年 | 1577篇 |
2017年 | 1248篇 |
2016年 | 4172篇 |
2015年 | 4318篇 |
2014年 | 4404篇 |
2013年 | 5629篇 |
2012年 | 4579篇 |
2011年 | 3941篇 |
2010年 | 4101篇 |
2009年 | 4113篇 |
2008年 | 3857篇 |
2007年 | 3244篇 |
2006年 | 2826篇 |
2005年 | 2814篇 |
2004年 | 2540篇 |
2003年 | 2346篇 |
2002年 | 3157篇 |
2001年 | 2304篇 |
2000年 | 2011篇 |
1999年 | 964篇 |
1998年 | 466篇 |
1997年 | 373篇 |
1996年 | 378篇 |
1995年 | 360篇 |
1994年 | 327篇 |
1993年 | 288篇 |
1992年 | 237篇 |
1991年 | 243篇 |
1990年 | 247篇 |
1989年 | 208篇 |
1988年 | 178篇 |
1987年 | 165篇 |
1986年 | 155篇 |
1985年 | 255篇 |
1984年 | 251篇 |
1983年 | 173篇 |
1982年 | 194篇 |
1981年 | 160篇 |
1980年 | 163篇 |
1979年 | 147篇 |
1978年 | 122篇 |
1977年 | 186篇 |
1976年 | 153篇 |
1975年 | 124篇 |
1973年 | 120篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
Addition of functionalized zinc-copper reagents to the title complexes proceeds in a highly diastereoselective fashion to afford dienol complexes. The relative configurations of adducts 3d were determined by single X-ray diffraction analysis. 相似文献
4.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities. 相似文献
5.
Gang Wang Xiulin Zhu Zhenping Cheng Jian Zhu 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2912-2921
A series of (di)picolinic acids and their derivates are investigated as novel complexing tridentate or bidentate ligands in the iron‐mediated reverse atom transfer radical polymerization of methyl methacrylate in N,N‐dimethylformamide at 100 °C with 2,2′‐azobisisobutyrontrile as an initiator. The polymerization rates and polydispersity indices (1.32–1.8) of the resulting polymers are dependent on the structures of the ligands employed. Different iron complexes may be involved in iron‐mediated reverse atom transfer radical polymerization, depending on the type of acid used. 1H NMR spectroscopy has been used to study the structure of the resulting polymers. Chain‐extension reactions have been performed to further confirm the living nature of this catalytic system. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2912–2921, 2006 相似文献
6.
设函数f(w)为凸区域D内的单叶解析函数,对于2≤n≤8和所有w∈D,本文得到估计式|f(n)(w)/f'(w)|的精确上界.这个结果推广了一些已知的结论. 相似文献
7.
Wen Zhang Hui Huang Yu Ding Margherita Gavagnin Ernesto Mollo Guido Cimino Yue‐Wei Guo 《Helvetica chimica acta》2006,89(4):813-820
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds. 相似文献
8.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
9.
10.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献