全文获取类型
收费全文 | 305565篇 |
免费 | 7587篇 |
国内免费 | 3802篇 |
专业分类
化学 | 144811篇 |
晶体学 | 4167篇 |
力学 | 16403篇 |
综合类 | 142篇 |
数学 | 47594篇 |
物理学 | 103837篇 |
出版年
2021年 | 2437篇 |
2020年 | 2819篇 |
2019年 | 2973篇 |
2018年 | 11836篇 |
2017年 | 12597篇 |
2016年 | 8873篇 |
2015年 | 4317篇 |
2014年 | 5349篇 |
2013年 | 10607篇 |
2012年 | 13223篇 |
2011年 | 22421篇 |
2010年 | 14375篇 |
2009年 | 14349篇 |
2008年 | 19352篇 |
2007年 | 22417篇 |
2006年 | 8534篇 |
2005年 | 13822篇 |
2004年 | 9878篇 |
2003年 | 9047篇 |
2002年 | 6935篇 |
2001年 | 6664篇 |
2000年 | 5124篇 |
1999年 | 4002篇 |
1998年 | 3295篇 |
1997年 | 3116篇 |
1996年 | 2903篇 |
1995年 | 2757篇 |
1994年 | 2651篇 |
1993年 | 2435篇 |
1992年 | 2706篇 |
1991年 | 2597篇 |
1990年 | 2514篇 |
1989年 | 2380篇 |
1988年 | 2318篇 |
1987年 | 2298篇 |
1986年 | 2206篇 |
1985年 | 2819篇 |
1984年 | 2819篇 |
1983年 | 2486篇 |
1982年 | 2580篇 |
1981年 | 2386篇 |
1980年 | 2348篇 |
1979年 | 2518篇 |
1978年 | 2557篇 |
1977年 | 2418篇 |
1976年 | 2517篇 |
1975年 | 2419篇 |
1974年 | 2378篇 |
1973年 | 2588篇 |
1972年 | 1650篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
Zhihong Zhao Bin Wang Rui Tan Wenjing Liu Minghui Zhang 《Magnetic resonance in chemistry : MRC》2022,60(4):427-433
In this study, the transverse relaxation time (T2) of activated carbon (AC) in different relative environment humidity was detected firstly by low-field nuclear magnetic resonance (LFNMR). The pore size (diameter) of AC distributions was calculated by the relationship between T2 and surface relaxation rate (ρ), where ρ was obtained by the detection of nine porous materials with known pore size. The results showed that the pore size distributions of AC calculated by ρ < 0.19 nm/ms were in good agreement with that obtained by nitrogen adsorption method and proved that LFNMR as a new detection method was feasible for characterizing AC pore size distribution. 相似文献
2.
Zhang Bing Yang Jie-qin Liu Ying Hu Bin Yang Yang Zhao Li Lu Qiang 《Cellulose (London, England)》2022,29(12):6565-6578
Cellulose - Heating is essential in various biomass pre-treatments and thermal conversion processes. It is of practical significance to study the characteristics of cellulose-lignin and... 相似文献
3.
Dan Chen Kaixin Du Xiaochen Niu Hongwei Zhang Xue Zhang Yu Tang Jianchun Zhao 《Biomedical chromatography : BMC》2022,36(3):e5288
Amlexanox, an anti-inflammatory and anti-allergic agent, has been widely used clinically for the treatment of canker sores, asthma, and allergic rhinitis. Recently, amlexanox has received considerable attention in curing nonalcoholic fatty liver diseases and hepatitis virus infection. Herein, we first established a sensitive high-performance liquid chromatography-tandem mass spectrum (LC–MS/MS) method for the determination of amlexanox in rat plasma. Propranolol was used as the internal standard (IS). Using a simple protein precipitation method, the amlexanox and IS were separated with Capcell Pak C18 column (2.0 × 50 mm, 5 μm) and eluted with water and acetonitrile each containing 0.1% formic acid using gradient elution condition at a flow rate of 0.4 mL·min−1. Amlexanox and IS were detected by a triple quadrupole mass in multiple reactive monitoring (MRM) under the transitions of m/z 299.2 → 281.2 and m/z 259.9 → 116.1 with positive electrospray ionization, respectively. The calibration curves of amlexanox were established with the range of 50 to 2000 ng·mL−1 (r2 > 0.99). The validation method consisted of selectivity, accuracy, precision, carryover effect, matrix effect, recovery, dilution effect, and stability. The fully validated method was successfully applied to the pharmacokinetic study of amlexanox in Wistar rats. 相似文献
4.
Kinetics and Catalysis - The results of studies in the field of synthesis and characterization of layered double hydroxides (LDHs) obtained using solid-phase reactions are summarized. The effect of... 相似文献
5.
Petrov P. A. Filippova E. A. Kompankov N. B. Sukhikh T. S. Sokolov M. N. 《Journal of Structural Chemistry》2022,63(3):470-475
Journal of Structural Chemistry - A new polymorph of the [ReCl3(MeCN)(PPh3)2] complex is synthesized and characterized by single crystal X-ray diffraction (XRD). Its recrystallization from the... 相似文献
6.
Cellulose - In this research, the production of levoglucosan (LG) and levoglucosenone (LGO) was improved from acid-impregnated cellulose via fast pyrolysis. Thermogravimetric and kinetic analysis... 相似文献
7.
Tsyganova S. I. Fetisova O. Yu. Mazurova E. N. Taran O. P. Kuznetsov B. N. 《Russian Journal of Applied Chemistry》2022,95(3):408-416
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed.... 相似文献
8.
Roopa K. P. Keshavamurthy K. Mahesh B. Veena K. P. Shankara B. S. Basavaiah K. 《Journal of Applied Spectroscopy》2022,89(4):809-818
Journal of Applied Spectroscopy - Three simple, sensitive, precise, and rapid spectrophotometric methods are developed and optimized for the assay of vardenafil in pharmaceutical formulations. The... 相似文献
9.
Varfolomeev S. D. Panin A. A. Semenova N. A. Ublinskiy M. V. Akhadov T. A. Bykov V. I. Tsybenova S. B. 《Russian Chemical Bulletin》2022,71(3):591-594
A kinetic study of the effect of thermoheliox (inhalation of a helium and oxygen mixture, 70 °C) on the functional hemodynamics of the human brain by functional magnetic resonance imaging was carried out. The dynamic responses of the BOLD signal were found to be biphasic. An empirical equation describing the first phase of the hemodynamic response to visual stimulus was proposed. It was shown that preliminary inhalation of thermoheliox stimulates the hemodynamic responses by slowing down the vasoconstriction.
相似文献10.
Edward G. Sheetz Zhao Zhang Alyssa Marogil Minwei Che Dr. Maren Pink Dr. Veronica Carta Prof. Dr. Krishnan Raghavachari Prof. Dr. Amar H. Flood 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201584
The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3−). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3−, by cyanostar macrocycles that are size-complementary to the inorganic BF4− progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K+ salts of R−BF3− anions. 相似文献