全文获取类型
收费全文 | 5532篇 |
免费 | 511篇 |
国内免费 | 534篇 |
专业分类
化学 | 2356篇 |
晶体学 | 150篇 |
力学 | 794篇 |
综合类 | 55篇 |
数学 | 1035篇 |
物理学 | 2187篇 |
出版年
2024年 | 9篇 |
2023年 | 41篇 |
2022年 | 85篇 |
2021年 | 87篇 |
2020年 | 123篇 |
2019年 | 96篇 |
2018年 | 97篇 |
2017年 | 136篇 |
2016年 | 158篇 |
2015年 | 123篇 |
2014年 | 251篇 |
2013年 | 348篇 |
2012年 | 289篇 |
2011年 | 332篇 |
2010年 | 293篇 |
2009年 | 363篇 |
2008年 | 379篇 |
2007年 | 379篇 |
2006年 | 294篇 |
2005年 | 342篇 |
2004年 | 321篇 |
2003年 | 223篇 |
2002年 | 214篇 |
2001年 | 171篇 |
2000年 | 157篇 |
1999年 | 175篇 |
1998年 | 148篇 |
1997年 | 139篇 |
1996年 | 92篇 |
1995年 | 96篇 |
1994年 | 75篇 |
1993年 | 69篇 |
1992年 | 77篇 |
1991年 | 47篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 37篇 |
1987年 | 38篇 |
1986年 | 34篇 |
1985年 | 12篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 22篇 |
1980年 | 9篇 |
1979年 | 25篇 |
1978年 | 19篇 |
1977年 | 11篇 |
1976年 | 16篇 |
1975年 | 5篇 |
排序方式: 共有6577条查询结果,搜索用时 0 毫秒
61.
Delenclos S. Kolinsky C. Longuemart S. Hadj Sahraoui A. Buisine J. M. 《Journal of Thermal Analysis and Calorimetry》2002,70(2):549-558
The photopyroelectric (PPE) method is proposed as a sensitive technique to study a binary mixture of liquid crystals in a
contact preparation. The photothermal signal is generated while scanning the contact preparation. The crystal-smectic A, smectic
A-nematic, and nematic-isotropic interphase boundaries are detected. The displacement of these boundaries due to the variation
of the temperature is monitored. The study of these displacements allows us to draw the complete temperature-concentration
phase diagram of a binary mixtures.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
62.
An explicit expression for the analytical first derivative of the Z-averaged perturbation theory taken to second order energy, due to Lee and Jayatilaka, is presented for application to high-spin
systems described by a restricted open-shell Hartree–Fock wavefunction. The use of frozen core orbitals is incorporated into
the derivation.
Received: 23 April 2001 / Accepted: 31 August 2001 / Published online: 9 January 2002 相似文献
63.
I. Kuselman 《Accreditation and quality assurance》1998,3(3):131-133
It is argued that results of uncertainty calculations in chemical analysis should be taken into consideration with some caution
owing to their limited generality. The issue of the uncertainty in uncertainty estimation is discussed in two aspects. The
first is due to the differences between procedure-oriented and result-oriented uncertainty assessments, and the second is
due to the differences between the theoretical calculation of uncertainty and its quantication using the validation (experimental)
data. It is shown that the uncertainty calculation for instrumental analytical methods using a regression calibration curve
is result-oriented and meaningful only until the next calibration. A scheme for evaluation of the uncertainty in uncertainty
calculation by statistical analysis of experimental data is given and illustrated with examples from the author's practice.
Some recommendations for the design of corresponding experiments are formulated. 相似文献
64.
E. L. Anderson M. M. Thomason H. T. Mayfield W. Bertsch 《Journal of separation science》1979,2(6):335-342
A versatile two-dimensional gas chromatograph is described, consisting of 2 separate ovens, one intermediate trap, an auxiliary inlet, and the necessary hardware to effect off-line switching according to the principle of Deans. The unit has been designed for use with high resolution glass capillary columns. The performance of individual instrumental components was critically evaluated. Results showed that low dead volume glass to metal connections were required in the manifold and detector lines to minimize extra-column effects. The mass of the intermediate trap must be low to allow rapid heating. Operational parameters are discussed and examples of some applications are shown. 相似文献
65.
碘溴化银乳剂薄片颗粒的潜影分散与碘离子在颗粒中的分布有关。本文用交叉光楔曝光技术测定了由次潜影造成的潜影分散,并根据所测出的潜影分散度和乳剂的表面感光度,对内、表敏的分布作了分析。结果表明,碘离子分布在颗粒边缘的乳剂,其表面潜影分散度要比碘离子均匀分布的颗粒更甚,后者且表现出内、表敏度竞争的现象。 相似文献
66.
A delayed coincidence method, time-interval analysis (TIA), has been applied to successive – decay events on the millisecond time-scale. Such decay events are part of the 220Rn216Po (T1/2 145 ms) (Th-series) and 219Rn215Po (T1/2 1.78 ms) (Ac-series). By using TIA in addition to measurement of 226Ra (U-series) from -spectrometry by liquid scintillation counting (LSC), two natural decay series could be identified and separated. The TIA detection efficiency was improved by using the pulse-shape discrimination technique (PSD) to reject -pulses, by solvent extraction of Ra combined with simple chemical separation, and by purging the scintillation solution with dry N2 gas. The U- and Th-series together with the Ac-series were determined, respectively, from alpha spectra and TIA carried out immediately after Ra-extraction. Using the 221Fr217At (T1/2 32.3 ms) decay process as a tracer, overall yields were estimated from application of TIA to the 225Ra (Np-decay series) at the time of maximum growth. The present method has proven useful for simultaneous determination of three radioactive decay series in environmental samples. 相似文献
67.
68.
Per Hyltoft Petersen 《Accreditation and quality assurance》2002,7(11):488-493
The validity of any model depends on its ability to imagine the situation or problem to which it is applied. Further, the
assumptions made in relation to the model are determining for the actual outcome. Within the field of clinical biochemistry
a lot of models for analytical quality specifications, based on a variety of concepts and ’clinical settings’, have been proposed.
A hierarchical structure for application of these approaches and models has been agreed on at several occasions in 1999. In
this hierarchy, the highest rank is given to evaluation of analytical quality specifications based on ’clinical settings’/’clinical
outcome’ models, followed by specifications based on biological variation and on ’clinicians opinions’. This contribution,
deals with the problems of combining random and systematic errors and the implications of application of different models
to a variety of clinical settings.
Received: 1 June, 2002 Accepted: 17 July 2002
Presented at the European Conference on Quality in the Spotlight in Medical Laboratories, 7–9 October 2001, Antwerp, Belgium 相似文献
69.
F. C. Adams 《Accreditation and quality assurance》1998,3(8):308-316
The basic concepts of traceability as they are defined by the Comité Consultatif pour la Cluantité de Matière are contrasted
with the practical exploitation in chemical analysis. The applicability of traceability concepts are tested for their practical
applicability on four different analytical methodologies, neutron activation analysis, plasma mass spectrometry, beam microscopical
analysis and speciation analysis of organometallic compounds.
Received: 31 March 1998 · Accepted: 6 June 1998 相似文献
70.
研究了高效液相色谱-火焰原子吸收光谱联用系统分析信号处理方法,比较了各种处理方法的优缺点,用积分与适应平滑法综合处理色谱峰分析信号,不仅能有效地消除噪声,而且能使分析信号得到加强,以测定镍为例,经积分与适应平滑法综合处理后,检出限改善了2.7倍。 相似文献