全文获取类型
收费全文 | 2009篇 |
免费 | 55篇 |
国内免费 | 16篇 |
专业分类
化学 | 1413篇 |
晶体学 | 62篇 |
力学 | 23篇 |
数学 | 74篇 |
物理学 | 508篇 |
出版年
2021年 | 9篇 |
2020年 | 18篇 |
2019年 | 24篇 |
2018年 | 20篇 |
2017年 | 12篇 |
2016年 | 30篇 |
2015年 | 34篇 |
2014年 | 37篇 |
2013年 | 96篇 |
2012年 | 116篇 |
2011年 | 140篇 |
2010年 | 75篇 |
2009年 | 69篇 |
2008年 | 110篇 |
2007年 | 144篇 |
2006年 | 93篇 |
2005年 | 103篇 |
2004年 | 116篇 |
2003年 | 81篇 |
2002年 | 64篇 |
2001年 | 55篇 |
2000年 | 37篇 |
1999年 | 41篇 |
1998年 | 22篇 |
1997年 | 25篇 |
1996年 | 24篇 |
1995年 | 34篇 |
1994年 | 27篇 |
1993年 | 36篇 |
1992年 | 42篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 13篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1976年 | 10篇 |
1975年 | 12篇 |
1974年 | 16篇 |
1973年 | 11篇 |
1968年 | 10篇 |
1967年 | 11篇 |
排序方式: 共有2080条查询结果,搜索用时 46 毫秒
41.
A gas chromatographic-mass spectrometric procedure has been developed for the quantitation of the benzodiazepine antagonist flumazenil in human plasma. The assay utilizes an extraction at alkaline pH with benzene-dichloroethane (80:20), selective ion monitoring, isobutane positive-ion chemical ionization mass spectrometry and stable isotope dilution. The method has been used to measure plasma concentrations of flumazenil in over 1500 clinical samples over a range of 0.5-200 ng/ml (using 2 ml of plasma). 相似文献
42.
We give a lower bound for the number of vertices of a generald-dimensional polytope with a given numberm ofi-faces for eachi = 0,..., d/2 – 1. The tightness of those bounds is proved using McMullen's conditions. Form greater than a small constant, those lower bounds are attained by simpliciali-neighbourly polytopes. 相似文献
43.
F. Kokai Y. Koga Y. Kakudate M. Kawaguchi S. Fujiwara M. Kubota K. Fukuda 《Applied Physics A: Materials Science & Processing》1994,59(3):299-304
Laser-ionization Time-Of-Flight (TOF) mass-spectrometric studies have been carried out on the 532 nm and 1064 nm laser ablation products from a nitrogen-rich polymer. The polymer used had an elemental composition of C6.0N8.9H3.4 and consisted of C=N, C-N, and N-H chemical bonds. The TOF mass spectra observed were composed of various peaks (150 amu) depending on the ablation laser wavelength. The primary peaks were assigned to C+, CN+, CHnN+
2 (n=1–3) and C2H2N+
3 for 532 nm ablation, and C+, C+
3, HCN+, HCCN+, CH2NH+, HNCN+, H3NCN+, and C4H4N+
7 for 1064 nm ablation. The flight velocity distributions with peak velocities ranging from 8.6×103 cm/s to 3.8×104 cm/s were measured for these products. The distinct velocity distributions observed between small and large products indicate the presence of two origins in the fragment ejection process from the polymer for both 532 nm and 1064 nm ablation. Furthermore, we suggest an importance of the translational energy of the fragments for the product generation in the laser plume. 相似文献
44.
S. Momota Y. Nojiri M. -B. Tanaka T. Yanagisawa M. Fukuda K. Matsuta T. Minamisono 《Hyperfine Interactions》1993,80(1-4):1275-1279
To disclose the basic mechanisms of nuclear polarization creation realized by the tilted foil technique, hyperfine quantum beats of the nuclear polarization of the short-lived beta-emitter8Li(I
=2+,T
1/2=840 ms) were measured as a function of the distance between two tilted foils. From the observed beats of the8Li nuclear polarization, it was found that the Fermi-contact interaction of the8Li nucleus with the ground 1s-electron in LiIII plays a main role in the final stage of polarization transfer from polarized orbital electrons to the8Li nucleus. 相似文献
45.
T. Minamisono S. Fukuda T. Ohtsubo M. Tanigaki A. Kitagawa M. Fukuda K. Matsuta Y. Nojiri S. Takeda 《Hyperfine Interactions》1993,78(1-4):191-194
Quadrupole effects in -NMR spectra of41Sc(I
=7/2–,T
1/2=0.596 s) implanted in a TiO2 single crystal were detected by use of a modified -NMR technique. Using the field gradient in the crystal determined by the pulsed-Fourier-transformed NMR of45Sc in TiO2, the quadrupole moment of41Sc has been determined as |Q(41Sc; 7/2–)|=166±8 mb. 相似文献
46.
S. Momota Y. Nojiri M. -B. Tanaka T. Yanagisawa M. -Y. Tanaka M. Fukuda K. Matsuta T. Minamisono 《Hyperfine Interactions》1993,80(1-4):1281-1286
In order to study the basic mechanism of polarization enhancement realized by the multitilted foil technique, nuclear polarization of short-lived beta-emitter8B(T1/2=769 ms,I
=2+) was induced. Utilizing up to ten tilted foils, the polarization enhancement was measured as a function of the foil numbers. The observed enhancement for8B was combined with the previous results for12B(I
=1+,T
1/2=20 ms) which has the same atomic configurations but different nuclear spin. Analyzing these results in the framework of the classical vector model, the essential features of the enhancement depending on the nuclear spin was disclosed. 相似文献
47.
Isozaki T Fujikawa T Takezoe H Fukuda A Hagiwara T Suzuki Y Kawamura I 《Physical review. B, Condensed matter》1993,48(18):13439-13450
48.
It is known that for simple arrangements in thed-dimensional Euclidean spaceR
d
The average number ofj-dimensional subfaces of ak-dimensional face is less than
. In this paper, we show that this is also true for all arrangements inR
d
and for all oriented matroids, and we give combinatorial proofs. 相似文献
49.
Four possible diastereomers of pentenocin B were synthesized in a stereocontrolled manner, and the first total synthesis of a natural enantiomer of (+)-pentenocin B unequivocally established the absolute stereochemistry to be 4S,5R,6R. 相似文献
50.
4-Fluorinated UDP-MurNAc pentapeptide, 2, has been synthesized. In our previous study, UDP-MurNAc pentapeptide analogue 1 was found to be incorporated into the bacterial cell wall through biosynthesis. Compound 2 showed growth-inhibition activity against Gram-positive bacteria when it was added to growth media at 0.01 mg/mL. [structure--see text] 相似文献