全文获取类型
收费全文 | 5147篇 |
免费 | 196篇 |
国内免费 | 13篇 |
专业分类
化学 | 4157篇 |
晶体学 | 43篇 |
力学 | 51篇 |
数学 | 251篇 |
物理学 | 854篇 |
出版年
2023年 | 30篇 |
2022年 | 34篇 |
2021年 | 53篇 |
2020年 | 74篇 |
2019年 | 94篇 |
2018年 | 60篇 |
2017年 | 47篇 |
2016年 | 114篇 |
2015年 | 99篇 |
2014年 | 155篇 |
2013年 | 244篇 |
2012年 | 268篇 |
2011年 | 337篇 |
2010年 | 134篇 |
2009年 | 151篇 |
2008年 | 313篇 |
2007年 | 310篇 |
2006年 | 294篇 |
2005年 | 305篇 |
2004年 | 252篇 |
2003年 | 189篇 |
2002年 | 196篇 |
2001年 | 128篇 |
2000年 | 145篇 |
1999年 | 61篇 |
1998年 | 53篇 |
1997年 | 49篇 |
1996年 | 67篇 |
1995年 | 45篇 |
1994年 | 61篇 |
1993年 | 40篇 |
1992年 | 59篇 |
1991年 | 49篇 |
1990年 | 47篇 |
1989年 | 47篇 |
1988年 | 53篇 |
1987年 | 44篇 |
1986年 | 65篇 |
1985年 | 58篇 |
1984年 | 58篇 |
1983年 | 35篇 |
1982年 | 42篇 |
1981年 | 38篇 |
1980年 | 34篇 |
1979年 | 37篇 |
1978年 | 33篇 |
1977年 | 28篇 |
1976年 | 27篇 |
1975年 | 34篇 |
1974年 | 31篇 |
排序方式: 共有5356条查询结果,搜索用时 15 毫秒
51.
52.
An antiviral nucleoside or virazole was synthesized efficiently and regioselectively starting with benzyl cyanoformate. 相似文献
53.
T Tatee K Narita S Kurashige S Ito H Miyazaki H Yamanaka M Mizugaki T Sakamoto H Fukuda 《Chemical & pharmaceutical bulletin》1986,34(4):1643-1655
54.
The adsorbability of pertechnetate ion (TcO
4
–
) reached 96% for an active carbon at the 0.1 g/50 ml concentration level, increasing with diminution of acid and its salt concentrations, and depending on the type of anions present. With constant anion concentration, TcO
4
–
adsorbability rose with decreasing pH in the acidic region, followed in the region around neutrality by a plateau, and in the basic region by an appreciable decline of TcO
4
–
adsorbability. In the acidic region, part of once-adsorbed TcO
4
–
appeared to be displaced by other anions. Reversibility was noted between the adsorption and desorption of TcO
4
–
. 相似文献
55.
Separation of salidroside from Rhodiola crenulata by high-speed counter-current chromatography 总被引:3,自引:0,他引:3
High-speed counter-current chromatography (HSCCC) was used to purify salidroside from an extract of Rhodiola crenulata with two steps using a two-phase solvent system composed of ethyl acetate-n-butanol-water (1:4:5, v/v) in the first run and chloroform-methanol-isopropanol-water (5:6:1:4) in the second run. The method yielded 21.9 mg of salidroside from 1.216 g of the crude sample at 98% purity determined by HPLC analyses. Identification was performed by 1H NMR, 13C NMR, and MS. 相似文献
56.
To sophisticate the nuclear fuel recycling processes, the transfer percentages for Pd, Mo, Te, and Sb should be determined. Each element solution containing NaNO3 or HNO3 was fed consistently into the thin film evaporator regulated in vac and at 50 °C. The analyte percentages in the inside of the lid, in the condenser, and in the distillate were 10-1%/m2, 10-3%/m2, and 10-3% (DF = 105), respectively. The Mo percentage in the condenser was lower by a factor of 10 than those of other elements investigated. The NO3
- percentages were nearly constant despite increasing HNO3 concentrations, however, the ratios decreased with increasing NaNO3 concentrations. 相似文献
57.
M Sugiyama T Sakamoto K Tabata K Endo K Ito M Kobayashi H Fukumi 《Chemical & pharmaceutical bulletin》1989,37(8):2122-2131
Thiazolo[3,2-a]thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (6, 11 and 16), and polymethylene condensed thieno[3,2-d]-, [3,4-d]- and [2,3-d]pyrimidin-5-one derivatives (19-21), in which the oxygen atom of the oxazolidine moiety in 3 was replaced by a sulfur atom or methylene groups, were synthesized and evaluated for gastric antisecretory activity in pylorus-ligated rats. The structure-activity relationships of these compounds are discussed. 相似文献
58.
I. Kunugiyama N. Ito T. Ishida S. Suzuki Y. Katoh Y. Furukawa 《Journal of Radioanalytical and Nuclear Chemistry》1992,165(5):309-317
Bromine and chlorine concentrations in some tissues (liver, spleen, thymus) of healthy mice (normal group) and lymphomatous mice (lymphoma group) were determined by neutron activation analysis. There were significant differences in the Br concentrations of the tissues between the normal and lymphomatous group, while the Cl concentrations were found relatively constant in all the tissues. As a result, the Br/Cl ratios in the tissues of the lymphomatous group were significantly higher than those of the normal group. It was difficult to conclude that Br was absorbed into the bodies of lymphomatous mice more easily than was Cl. It is suggested that Br excretion from the body is suppressed. 相似文献
59.
Fumio Hamada Kyoko Ishikawa Riko Ito Hisanori Shibuya Sanyo Hamai Iwao Suzuki Tetsuo Osa Akihiko Ueno 《Journal of inclusion phenomena and macrocyclic chemistry》1994,20(1):43-51
-Cyclodextrin with two sodium anthranilate moieties (1) has been prepared as a sensor for detecting organic compounds including terpenoids and steroids. Compound1 shows a pure monomer fluorescence whose intensity is increased or decreased upon addition of the guest species examined. In this system, the sodium anthranilate moieties act either as a spacer, which enables the cyclodextrin to form a 1:1 host-guest complex by narrowing the -cyclodextrin cavity, or as a hydrophobic cap.1 recognizes steroids with much higher sensitivity than terpenoids, in which the appended moieties act as a hydrophobic cap for terpenoids and a spacer for steroids, respectively. 相似文献
60.
Y Nishioka S Kyotani M Okamura M Miyazaki Y Sakamoto M Morita K Okazaki S Ohnishi Y Yamamoto K Ito 《Chemical & pharmaceutical bulletin》1992,40(1):267-268
Hepatic artery of dogs was embolized with cisplatin (CDDP) albumin microspheres containing chitin and chitosan to investigate the in vivo CDDP release kinetics from CDDP albumin microspheres, the CDDP cumulative characteristics in the liver, and the influence of microsphere administration on hepatic tissue. Results showed that changes in blood CDDP content were dependent on CDDP albumin microsphere type and that release kinetics were better sustained when chitin was added to the microspheres or when the microspheres were treated with chitosan. In particular, the administration of CDDP in the chitin-containing CDDP chitosan albumin microspheres showed a blood CDDP content of approximately 0.26 micrograms Pt/ml 14 d after administration. The administration of chitin-containing or chitosan treated CDDP microspheres showed a CDDP content in the hepatic tissue of 0.14 to 0.23 micrograms Pt/g 28 d after administration. They also showed better control of CDDP release than those without chitin or chitosan treatment. No CDDP influence on hepatic tissue was observed. We conclude that, even in vivo, chitin and chitosan are effective embolic materials. 相似文献