全文获取类型
收费全文 | 2730篇 |
免费 | 224篇 |
国内免费 | 136篇 |
专业分类
化学 | 1869篇 |
晶体学 | 34篇 |
力学 | 114篇 |
综合类 | 9篇 |
数学 | 399篇 |
物理学 | 665篇 |
出版年
2023年 | 38篇 |
2022年 | 37篇 |
2021年 | 79篇 |
2020年 | 97篇 |
2019年 | 100篇 |
2018年 | 90篇 |
2017年 | 70篇 |
2016年 | 143篇 |
2015年 | 105篇 |
2014年 | 139篇 |
2013年 | 198篇 |
2012年 | 188篇 |
2011年 | 220篇 |
2010年 | 129篇 |
2009年 | 116篇 |
2008年 | 144篇 |
2007年 | 141篇 |
2006年 | 148篇 |
2005年 | 115篇 |
2004年 | 85篇 |
2003年 | 58篇 |
2002年 | 69篇 |
2001年 | 51篇 |
2000年 | 56篇 |
1999年 | 35篇 |
1998年 | 27篇 |
1997年 | 25篇 |
1996年 | 28篇 |
1995年 | 35篇 |
1994年 | 24篇 |
1993年 | 23篇 |
1992年 | 26篇 |
1991年 | 27篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 21篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有3090条查询结果,搜索用时 46 毫秒
41.
42.
43.
44.
45.
Explicit formulas of minimum-variance linear unbiased estimators of the unknown mean are derived for homogeneous random fields with correlation functions observed on the set (a cross).Translated from Vychislitel'naya i Prikladnaya Matematika, No. 64, pp. 116–121, 1988. 相似文献
46.
H. S. Dang H. B. Desai D. D. Jaiswal S. R. Kayasth S. Somasundaram 《Journal of Radioanalytical and Nuclear Chemistry》1983,77(1):65-70
A simple separation scheme for the analysis of As, Mn, Mo, Cu and Zn using neutron activation is described. It has been checked
using three standard reference materials, A-11 milk powder (IAEA) and bovine liver and orchard leaves (USNBS) and found to
give acceptable results. This scheme was applied for determination of these trace elements in mature human milk samples. The
concentrations of As, Mn, Mo, Cu in samples obtained from two socio-economic groups—low and middle incomes—were not significantly
different. However, Zn levels in samples obtained from the poor income group were significantly lower than in those obtained
from the other group.
Work carried out under Research Contract No. 2598/RB of International Atomic Energy, Vienna.
Health Physics Division.
Analytical Chemistry Division. 相似文献
47.
文中报道两种新的含茂钛低钛物Cp_2Ti(Cl)-O-[-Ti(Cp)(O_2CCH_4CH-O)-O-]n-H(Ⅰ)与Cp_2Ti(Cl)-O-[-Ti(Cp)(O_2CCH_2CH)-O-]_u-H(Ⅰ)的制备并用元素分析和光谱(IR,1~H NMR,MS)对它们进行了鉴定。 相似文献
48.
[structure: see text] Platinum(II) terpyridyl acetylide complex (1) was incorporated into Nafion membranes as a photosensitizer, and the Nafion was immersed in an aqueous or organic solution of 7-dehydrocholesterol, alpha-pinene, or cyclopentadiene. This photosensitizer system can generate singlet oxygen ((1)O(2)) in high quantum yield to oxidize the alkenes in the solution outside the Nafion and can be easily removed from the reaction vessel at the end of the photooxidation. 相似文献
49.
Nishi K. Bhardwaj Viet Hoang Vinh Dang Kien L. Nguyen 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,290(1-3):222-228
A wide range of kraft pulps from radiata pine produced by low-temperature kraft pulping in flow-through reactors was assessed for carboxyl and hexenuronic acid (HexA) contents using the conductometric titrations and UV spectrophotometer, respectively. The Kappa number of pulps varied from 20.8 to 84.7 when using a cooking liquor of 1 M effective alkali as Na2O, 25% sulfidity, and cooking time of 100–250 min. The experimental results showed that the carboxyl groups (including HexA) and HexA groups dissolved and their residual values in the pulp samples correlate linearly with Kappa number and pulp yield. The dissolving rate of all carboxyl groups is much faster than the loss of HexA. The HexA/lignin ratio decreased non-linearly with Kappa number. 相似文献
50.