全文获取类型
收费全文 | 32547篇 |
免费 | 1337篇 |
国内免费 | 1105篇 |
专业分类
化学 | 26692篇 |
晶体学 | 255篇 |
力学 | 288篇 |
综合类 | 166篇 |
数学 | 6040篇 |
物理学 | 1548篇 |
出版年
2023年 | 265篇 |
2022年 | 434篇 |
2021年 | 392篇 |
2020年 | 510篇 |
2019年 | 690篇 |
2018年 | 682篇 |
2017年 | 829篇 |
2016年 | 909篇 |
2015年 | 877篇 |
2014年 | 912篇 |
2013年 | 1531篇 |
2012年 | 1680篇 |
2011年 | 1835篇 |
2010年 | 1616篇 |
2009年 | 1948篇 |
2008年 | 1522篇 |
2007年 | 1773篇 |
2006年 | 1516篇 |
2005年 | 1411篇 |
2004年 | 1249篇 |
2003年 | 988篇 |
2002年 | 1055篇 |
2001年 | 701篇 |
2000年 | 783篇 |
1999年 | 712篇 |
1998年 | 653篇 |
1997年 | 642篇 |
1996年 | 632篇 |
1995年 | 657篇 |
1994年 | 567篇 |
1993年 | 455篇 |
1992年 | 360篇 |
1991年 | 386篇 |
1990年 | 358篇 |
1989年 | 304篇 |
1988年 | 395篇 |
1987年 | 391篇 |
1986年 | 302篇 |
1985年 | 321篇 |
1984年 | 326篇 |
1983年 | 180篇 |
1982年 | 290篇 |
1981年 | 261篇 |
1980年 | 210篇 |
1979年 | 179篇 |
1978年 | 67篇 |
1977年 | 46篇 |
1976年 | 46篇 |
1975年 | 26篇 |
1974年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Summary Hydroxypropyl methyl cellulose (HPMC) and polyethylene glycol 400 (PEG 400) content in HypoTears™ Daily Dose ophthalmic solution
are determined simultaneously by size exclusion chromatography. The retention times of HPMC and PEG 400 are 10.6 and 15.4
minutes, respectively. The method requires minimal sample pretreatment and is accurate and reproducible. The peak area response
from a refractive index detector versus HPMC and PEG 400 concentration is linear over the range of 50–150 % of their label
claims of 2.5 mg/mL and 10 mg/mL, respectively. The mean absolute recoveries of HPMC and PEG 400 at their label claim using
the described method are 98.9±1.3 % and 100.4±1.2 % (mean±SD, n=12), respectively. 相似文献
102.
本文研究并比较了分别以8-羟基喹啉和巯基苯骈噻唑为萃取剂,以活性硅胶为载体的柱式萃取色谱法对环境水中Zn、Cu、Pb、Cd、Fe、Co、Ni和Mn的最佳富集和洗脱条件。实验证明,后者明显优于前者。以巯基苯骈噻唑为萃取剂的色谱柱对金属元素的吸附具有快速、完全、寿命长和重现性好等特点。在pH=7~8之间回收率可达98%以上,富集倍数为200倍。 相似文献
103.
104.
105.
The principle of concentrating a substance from a mixture flow in a stationary sorbent layer of infinite length that was previously
developed for gas chromatography is extended to liquid chromatography.
Translated fromIzevestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1063–1065, May, 1997. 相似文献
106.
Marcel Erné 《Order》1991,8(2):159-173
We introduce a special type of order-preserving maps between quasiordered sets, the so-called cut-stable maps. These form the largest morphism class such that the corresponding category of quasiordered sets contains the category of complete lattices and complete homomorphisms as a full reflective subcategory, the reflector being given by the Dedekind-MacNeille completion (alias normal completion or completion by cuts). Suitable restriction of the object class leads to the category of separated quasiordered sets and its full reflective subcategory of completely distributive lattices. Similar reflections are obtained for continuous lattices, algebraic lattices, etc. 相似文献
107.
We answer some questions posed in [L. Grunenfelder, M. Mastnak, On bimeasurings, J. Pure Appl. Algebra 204 (2006) 258-269] concerning the universal bimeasuring bialgebra via a construction of suitable subcoalgebras of the universal measuring coalgebra. 相似文献
108.
In this article, we generalize the theory of motivic integration on formal schemes topologically of finite type and the notion
of motivic Serre invariant, to a relative point of view. We compute the relative motivic Serre invariant for curves defined
over the field of fractions of a complete discrete valuation ring R of equicharacteristic zero. One aim of this study is to understand the behavior of motivic Serre invariants under ramified
extension of the ring R. Thanks to our constructions, we obtain, in particular, an expression for the generating power series, whose coefficients
are the motivic Serre invariant associated to a curve, computed on a tower of ramified extensions of R. We give an interpretation of this series in terms of the motivic zeta function of Denef and Loeser. 相似文献
109.
The early evolution of gas chromatography in the former German Democratic Republic (GDR) is surveyed and instrument development is outlined, describing the most important models manufactured in the GDR. The organization of the Arbeitsgemeinschaft für Gas-Chromatographie (Working Group for GC) is chronicled and its activities are discussed. Subsequent parts of this article will deal with the six symposia organized by the Arbeitsgemeinschaft between 1958 and 1968. 相似文献
110.
Liquid chromatography-electrospray ionisation mass spectrometry was evaluated in the high-throughput analysis of microcystins and nodularins, cyanobacterial peptide hepatotoxins. Extracts originating from cyanobacterial strains and field material were separated on a 30 mm × 4 mm I.D. Merck Purospher STAR RP-18e column using a rapid gradient of aqueous formic acid and acetonitrile, ionised by electrospray technique and analysed on a Micromass Quattro II triple-quadrupole mass spectrometer operated in the selected ion recording (SIR) mode. The total analysis time per sample was 2.8 min corresponding to 514 samples a day. The system showed good robustness during a series of 320 repetitive injections of a field sample containing three major microcystins. 相似文献