全文获取类型
收费全文 | 1576篇 |
免费 | 85篇 |
国内免费 | 11篇 |
专业分类
化学 | 1288篇 |
晶体学 | 14篇 |
力学 | 12篇 |
数学 | 59篇 |
物理学 | 299篇 |
出版年
2023年 | 11篇 |
2022年 | 15篇 |
2021年 | 17篇 |
2020年 | 21篇 |
2019年 | 27篇 |
2018年 | 20篇 |
2017年 | 12篇 |
2016年 | 56篇 |
2015年 | 32篇 |
2014年 | 57篇 |
2013年 | 82篇 |
2012年 | 114篇 |
2011年 | 114篇 |
2010年 | 42篇 |
2009年 | 62篇 |
2008年 | 115篇 |
2007年 | 104篇 |
2006年 | 125篇 |
2005年 | 118篇 |
2004年 | 77篇 |
2003年 | 76篇 |
2002年 | 69篇 |
2001年 | 23篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 19篇 |
1996年 | 14篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有1672条查询结果,搜索用时 31 毫秒
101.
102.
In this paper, we investigate a delayed HIV infection model that considers the homeostatic proliferation of CD4+ T cells. The existence and stability of uninfected equilibrium and infected equilibria(smaller and larger ones) are studied by analyzing the characteristic equation of the system. The intracellular delay does not affect the stability of uninfected equilibrium, but it can change the stability of larger positive equilibrium and Hopf bifurcation appears inducing stable limit c... 相似文献
103.
The fluorescence properties of novel 6-butyl-2,3-dicyano-7-methyl-6H-1,4-diazepine styryl dyes having mono-, di-, tri-, and tetra(ethyleneglycol) units were examined. The mono(ethylenglycol) derivative was solid at room temperature, whereas the di-, tri-, and tetra(ethylenglycol) derivatives were oily. The monoethyleneglycol derivative showed weak aggregation-induced emission enhancement with fluorescence maximum at 649 nm, which comes from J-aggregates. The fluorescence of oily di-, tri-, and tetra(ethyleneglycol) derivatives in neat form was very weak. No aggregation-induced emission enhancement was observed for the oily derivatives. 相似文献
104.
105.
Pulsed laser deposition of iron atoms on graphite substrates was performed to produce iron carbide films. Mössbauer spectra of the sample revealed that iron carbide was produced on the substrate surface and that an α-Fe layer was produced above the iron carbide layer. When the substrate temperature was maintained at 300 K, the iron carbide layer had a hyperfine magnetic distribution because it contained high density of defects. Laser deposition of Fe at 570 K produced cementite Fe3C with fewer defects due to enhancement of thermal reactions or annealing of the films. The orientation of hyperfine field of the Fe3C film was parallel to the substrate surface. 相似文献
106.
Sato S Komoto T Kanamaru Y Kawamoto N Okada T Kaiho T Mogi K Morimoto S Umehara N Koda T Miyashita A Sakamoto T Niino Y Oka T 《Chemical & pharmaceutical bulletin》2002,50(2):292-297
New muq-opioid receptor (MOR) agonists containing 4-hydroxypiperidine, piperidine and piperazine moieties were synthesized and evaluated to find a peripheral opioid analgesic. Among the synthesized compounds, 12-[1-[3-(N,N-dimethylcarbamoyl)-3,3-diphenylpropyl]-4-hydroxypiperidin-4-yl]phenoxy]acetic acid (8: SS620) having phenoxyacetic acid and 4-hydroxypiperidine moieties showed the highest agonist potency on the MOR in an isolated guinea-pig ileum preparation, and it also had selectivity to the human MOR expressed in Chinese hamster ovary (CHO)-K1 cells compared with the same types of delta- and kappa-opioid receptors (DOR and KOR). In addition, compound 8 showed a 10 times more potent MOR agonist activity than loperamide. Furthermore, compound 8 showed a peripheral analgesic activity in vivo screening on rat. 相似文献
107.
108.
109.
Itaru Hibino Minoru Okita Takayuki Inoue Yasuhiro Banno Masahiro Hoso 《Physical Therapy Research》2008,11(1):1-6
Immobilization is often associated with decreased muscle elasticity. This condition is known as muscle contracture; however, the mechanism remains unclear. The purpose of this study was to clarify the mechanism governing muscle contracture in rat soleus muscle by identifying changes in ankle joint mobility, insoluble collagen concentration and type I and type III collagen isoforms following 1- and 3-week immobilizations. Following a 1-week immobilization, range of motion (ROM) of dorsiflexion declined to 90% of the control value; additionally, ROM dropped to 67.5% of the control value after a 3-week immobilization. This finding suggested that ankle joint mobility decreases in conjunction with extended periods of immobilization. Insoluble collagen concentration in soleus muscles, which was unchanged after 1 week of immobilization, increased 3 weeks after immobilization. These results may be indicative of collagen fibers with strong intermolecular cross-links contained in the muscle was made increased relatively by 3 weeks of immobilization. Therefore, the change in intermolecular cross-links may be significant in terms of progress of muscle contracture with longer periods of immobilization. On the other hand, the ratio of type III to type I collagen isoforms in muscular tissue increased following a 1-week immobilization; moreover, this ratio remained constant after 3 weeks of immobilization. These data suggested that muscle immobilization may induce type III collagen isoform expression. The increase in the ratio of type III to type I collagen isoforms do not change in parallel with the increase in the limitation in ROM; however, this phenomenon probably is not closely related to the progress of muscle contracture. The change of collagen isoform in immobilized muscle may be involved in the mechanism governing the progression of muscle fibrosis. 相似文献
110.
Yasuhiro Gotoh 《Proceedings of the American Mathematical Society》1999,127(5):1443-1451
Let denote the space of all positive superharmonic functions on a domain . Lindqvist showed that is a bounded subset of . Using this, we give a characterization of finitely connected -dimensional uniform domains and remarks on Hölder domains.