全文获取类型
收费全文 | 521篇 |
免费 | 14篇 |
专业分类
化学 | 416篇 |
晶体学 | 4篇 |
力学 | 5篇 |
数学 | 23篇 |
物理学 | 87篇 |
出版年
2023年 | 4篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 29篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 27篇 |
2007年 | 37篇 |
2006年 | 19篇 |
2005年 | 17篇 |
2004年 | 27篇 |
2003年 | 27篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 10篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 14篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1969年 | 4篇 |
1956年 | 3篇 |
1954年 | 3篇 |
排序方式: 共有535条查询结果,搜索用时 15 毫秒
31.
The C-S stretching vibrations of 28 aliphatic sulfides including one thiol are summarized, and all of the C-S stretching bands are classified into several groups. An extraordinarily low frequency associated with the ethyl group is discussed briefly. 相似文献
32.
33.
Sukontason K Sukontason KL Piangjai S Chaiwong T Boonchu N Kurahashi H Vogtsberger RC 《Micron (Oxford, England : 1993)》2003,34(8):359-364
Ultrastructure of all larval instars of Parasarcophaga dux (Thomson), a common flesh fly species in Thailand, is presented using scanning electron microscopy. Special attention is given to the structure of anterior and posterior spiracles since these are important features used to differentiate between other sarcophagids. Each anterior spiracle in second and third instars has a single row of papillae varying in number from 14 to 17. The posterior spiracular discs have incomplete peritremes, with a prominent inner arc. Three long, narrow spiracular slits are oriented more or less vertically in each spiracular disc of third instar. Posterior spiracular hairs lack extensive branching and emanate approximately midway down the length of each slit. Microscopic morphology of the mouthhooks markedly differs between the first and second instars. The structure of these mouthhooks supports this fly species as being necrophagous or capable of producing myiasis. 相似文献
34.
Koike R Motoyoshiya J Takaguchi Y Aoyama H 《Chemical communications (Cambridge, England)》2003,(6):794-795
A kinetic study of peroxyoxalate chemiluminescence reactions employing 2,4,6-trichlorophenyl N-aryl-N-tosyloxamates supports the 1,2-dioxetanones still bearing the eliminating group as the key intermediates that interact with the fluorophores rather than 1,2-dioxetanedione. 相似文献
35.
An optical technique for precise, non-contact, and real time measurement of silicon wafer temperature that uses the polarized reflectivity ratio Rp/Rs is described. The proposed method is based on temperature dependence of the optical functions of silicon. Expected strong temperature sensitivity is obtained near band gap. Simultaneous monitoring of temperature and oxide layer thickness is discussed using measurements at four wavelength 365 nm, 405 nm, 546 nm, and 820 nm. 相似文献
36.
37.
38.
Midori Nishide Yutaka Yoshikawa Eriko U Yoshikawa Kinuyo Matsumoto Hiromu Sakurai Naemi M Kajiwara 《Chemical & pharmaceutical bulletin》2008,56(8):1181-1183
We prepared 4 new Zn(II) complexes with Zn(O4), Zn(N(2)O(2)), and Zn(S2O2) coordination modes and evaluated their insulinomimetic activities in an in vitro study. The insulinomimetic activities of bis(pyrrole-2-carboxylato)zinc (Zn(pc)2), bis(alpha-furonic acidato)zinc (Zn(fa)2), bis(thiophene-2-carboxylato)zinc (Zn(tc)2), and bis(thiophene-2-acetato)zinc (Zn(ta)2) complexes were found to be higher than that of zinc sulfate (ZnSO4). Zn(ta)2 showed the highest insulinomimetic activity among the Zn(II) complexes because of its high lipophilicity. 相似文献
39.
This study investigated the variations in human plasma fluoride concentrations ([F]) and sought to determine the causes. Five subjects (27-33 years old) received a low-F diet during the 5 days of the study. Plasma samples and urine were collected every 3 h from 8 a.m. to 8 p.m. F, PTH, Ca and P were analyzed with the electrode, by chemiluminescence, AAS and colorimetry, respectively. A trend for the plasma [F] was found. The peak [F], 0.55 ± 0.11 μmol L−1, occurred at 11 a.m. and the lowest [F], 0.50 ± 0.06 μmol L−1 occurred between 5 and 8 p.m. Plasma [F] were positively correlated with urinary F excretion rates and with serum PTH levels, but not with the Ca or P levels. Serum PTH levels were positively correlated with urinary F excretion rates and negatively correlated with plasma Ca. The results suggest that the renal system seems to control the daily fluctuations in plasma [F]. 相似文献
40.
Asanuma H Toda T Murayama K Liang X Kashida H 《Journal of the American Chemical Society》2010,132(42):14702-14703
A new foldamer, acyclic threoninol nucleic acid (aTNA), has been synthesized by tethering each of the genetic nucleobases A, G, C, and T to d-threoninol molecules, which were then incorporated as building blocks into a scaffold bearing phosphodiester linkages. We found that with its fully complementary strand in an antiparallel fashion, the aTNA oligomer forms an exceptionally stable duplex that is far more stable than corresponding DNA or RNA duplexes, even though single-stranded aTNA is rather flexible and thus does not take a preorganized structure. 相似文献