全文获取类型
收费全文 | 5802篇 |
免费 | 161篇 |
国内免费 | 30篇 |
专业分类
化学 | 4509篇 |
晶体学 | 53篇 |
力学 | 77篇 |
数学 | 348篇 |
物理学 | 1006篇 |
出版年
2023年 | 25篇 |
2022年 | 48篇 |
2021年 | 57篇 |
2020年 | 69篇 |
2019年 | 94篇 |
2018年 | 57篇 |
2017年 | 51篇 |
2016年 | 117篇 |
2015年 | 100篇 |
2014年 | 137篇 |
2013年 | 294篇 |
2012年 | 320篇 |
2011年 | 386篇 |
2010年 | 209篇 |
2009年 | 243篇 |
2008年 | 389篇 |
2007年 | 376篇 |
2006年 | 428篇 |
2005年 | 377篇 |
2004年 | 347篇 |
2003年 | 283篇 |
2002年 | 278篇 |
2001年 | 85篇 |
2000年 | 73篇 |
1999年 | 64篇 |
1998年 | 71篇 |
1997年 | 71篇 |
1996年 | 67篇 |
1995年 | 59篇 |
1994年 | 36篇 |
1993年 | 43篇 |
1992年 | 32篇 |
1991年 | 39篇 |
1990年 | 23篇 |
1989年 | 20篇 |
1988年 | 32篇 |
1987年 | 32篇 |
1986年 | 49篇 |
1985年 | 61篇 |
1984年 | 49篇 |
1983年 | 25篇 |
1982年 | 53篇 |
1981年 | 55篇 |
1980年 | 48篇 |
1979年 | 40篇 |
1978年 | 31篇 |
1977年 | 30篇 |
1976年 | 24篇 |
1974年 | 16篇 |
1973年 | 19篇 |
排序方式: 共有5993条查询结果,搜索用时 0 毫秒
21.
22.
Mana Ito Takashi Ishizone 《Journal of polymer science. Part A, Polymer chemistry》2006,44(16):4832-4845
Anionic polymerization of N‐methoxymethyl‐N‐isopropylacrylamide ( 1 ) was carried out with 1,1‐diphenyl‐3‐methylpentyllithium and diphenylmethyllithium, ‐potassium, and ‐cesium in THF at ?78 °C for 2 h in the presence of Et2Zn. The poly( 1 )s were quantitatively obtained and possessed the predicted molecular weights based on the feed molar ratios between monomer to initiators and narrow molecular weight distributions (Mw/Mn = 1.1). The living character of propagating carbanion of poly( 1 ) either at 0 or ?78 °C was confirmed by the quantitative efficiency of the sequential block copolymerization using N,N‐diethylacrylamide as a second monomer. The methoxymethyl group of the resulting poly( 1 ) was completely removed to give a well‐defined poly(N‐isopropylacrylamide), poly(NIPAM), via the acidic hydrolysis. The racemo diad contents in the poly(NIPAM)s could be widely changed from 15 to 83% by choosing the initiator systems for 1 . The poly(NIPAM)s obtained with Li+/Et2Zn initiator system possessed syndiotactic‐rich configurations (r = 75–83%), while either atactic (r = 50%) or isotactic poly(NIPAM) (r = 15–22%) was generated with K+/Et2Zn or Li+/LiCl initiator system, respectively. Atactic and syndiotactic poly(NIPAM)s (42 < r < 83%) were water‐soluble, whereas isotactic‐rich one (r < 31%) was insoluble in water. The cloud points of the aqueous solution of poly(NIPAM)s increased from 32 to 37 °C with the r‐contents. These indicated the significant effect of stereoregularity of the poly(NIPAM) on the water‐solubility and the cloud point in water © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4832–4845, 2006 相似文献
23.
24.
A note on unit and class number of real quadratic fields 总被引:1,自引:0,他引:1
Takashi Agoh 《数学学报(英文版)》1989,5(3):281-288
Letp be an odd prime withp1 (mod 4) andQ(p) be the real quadratic field. Also let andh denote the fundamental unit and the class number of Q(p), respectively. The main purpose of this paper is to study the explicit expressions of
h
and
2h
, and to discuss the problems related to the conjecture of Ankeny-Artin-Chowla. 相似文献
25.
Reaction of gem-difluorinated vinyloxiranes with RCu(X)Li allowed us to introduce the R group regioselectively at the fluorine-attached terminal carbon atom in an SN2′ manner to afford (E)-allylic alcohols exclusively, while homoallylic alcohols with anti stereochemical relationship were found to be obtained selectively from higher-ordered cuprates derived from CuCl and RMgBr in a ratio of 1:3. 相似文献
26.
Hiroyuki Nakazumi Takashi Endo Hikaru Sonoda Teijiro Kitao 《Journal of heterocyclic chemistry》1985,22(3):821-824
3-Substituted 2-phenyl-4H-1-benzothiopyran-4-ones (thioflavones) were prepared to test antimicrobial activity. It was found that 3-(phenyl)thiochromone derivatives (isothioflavones) were prepared by the Meerwein reaction of thiochromone with p-nitrobenzenediazonium ion. 3-(Formyl)thioflavone exhibits weak antimicrobial activity against Trichophytons and Candida. 相似文献
27.
28.
29.
Using Gawedzki and Kupiainen's rigorous block spin transformation method, we study critical phenomena in 4 spin systems in four dimensions. In Part I of this work we investigate in detail the renormalization group trajectory of the system not exactly at the critical point. 相似文献
30.