全文获取类型
收费全文 | 2668篇 |
免费 | 84篇 |
国内免费 | 7篇 |
专业分类
化学 | 1951篇 |
晶体学 | 119篇 |
力学 | 68篇 |
数学 | 125篇 |
物理学 | 496篇 |
出版年
2023年 | 18篇 |
2022年 | 58篇 |
2021年 | 52篇 |
2020年 | 49篇 |
2019年 | 58篇 |
2018年 | 47篇 |
2017年 | 75篇 |
2016年 | 106篇 |
2015年 | 56篇 |
2014年 | 95篇 |
2013年 | 233篇 |
2012年 | 132篇 |
2011年 | 162篇 |
2010年 | 108篇 |
2009年 | 92篇 |
2008年 | 146篇 |
2007年 | 117篇 |
2006年 | 119篇 |
2005年 | 89篇 |
2004年 | 75篇 |
2003年 | 62篇 |
2002年 | 58篇 |
2001年 | 33篇 |
2000年 | 34篇 |
1999年 | 28篇 |
1998年 | 15篇 |
1997年 | 18篇 |
1996年 | 25篇 |
1995年 | 24篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 24篇 |
1991年 | 26篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 20篇 |
1987年 | 25篇 |
1986年 | 26篇 |
1985年 | 19篇 |
1984年 | 29篇 |
1983年 | 22篇 |
1982年 | 33篇 |
1981年 | 37篇 |
1980年 | 29篇 |
1979年 | 26篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 16篇 |
1975年 | 20篇 |
1973年 | 20篇 |
排序方式: 共有2759条查询结果,搜索用时 15 毫秒
91.
92.
Inhibition effect of imidazole derivative 1,7′-dimethyl-2′-propyl-1H,3′H-2,5′-bibenzo[d]imidazole (DPBI) against mild steel corrosion in 1 M HCl solutions was evaluated using the conventional mass loss method,
potentiodynamic polarization, linear polarization, and electrochemical impedance spectroscopy. The mass loss results showed
that DPBI is an excellent corrosion inhibitor; electrochemical polarizations data revealed the mixed mode of inhibition; and
the results of electrochemical impedance spectroscopy showed that the change in the impedance parameters, charge transfer
resistance, and double layer capacitance with the change in the concentration of the inhibitor is due to the adsorption of
the molecule leading to the formation of a protective layer on the surface of mild steel. The inhibition action of this compound
was assumed to occur via adsorption on the steel surface through the active centers of the molecule. 相似文献
93.
An unprecedented base promoted domino approach has been developed for the synthesis of pyridin-2-yl urea derivatives via the reaction of 2-aminopyridinium salts and arylamines. The developed strategy tolerated a wide range of functional groups and afforded pyridin-2-yl ureas in moderate to good yields. The reaction was postulated to involve tandem cyclization, intermolecular nucleophilic addition, ring opening, and demethylation. 相似文献
94.
A series of 2-[4-cyano-(3-trifluoromethyl)phenyl amino)]-4-(4-quinoline/coumarin-4-yloxy)-6-(fluoropiperazinyl)-s-triazines has been synthesized by a simple and efficient synthetic protocol. The antimicrobial activity of the compounds was studied against several bacteria (Staphylococcus aureus MTCC 96, Bacillus cereus MTCC 619, Escherichia coli MTCC 739, Pseudomonas aeruginosa MTCC 741, Klebsiella pneumoniae MTCC 109, Salmonella typhi MTCC 733, Proteus vulgaris MTCC 1771, Shigella flexneria MTCC 1457) and fungi (Aspergillus niger MTCC 282, Aspergillus fumigatus MTCC 343, Aspergillus clavatus MTCC 1323, Candida albicans MTCC 183) using paper disc diffusion technique and agar streak dilution method. Newly synthesized compounds were also tested for their in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv using BACTEC MGIT and Lowenstein-Jensen MIC method. 相似文献
95.
96.
Hasmukh S. Patel Ketan B. Patel 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):2443-2452
4-Amino-1,2,4-triazole (1) undergoes facile condensation with aromatic aldehydes to afford the corresponding 4-(arylidene-amino)-4H-[1,2,4]-triazole (2a–h) in good yield. Rearrangement of compounds (2a–h) with benzoyl isothiocyanate/4-chloro-benzoyl isothiocyanate/2,4-dichloro-benzoyl isothiocyanate yields corresponding 1,3,5-oxadiazine derivatives (3). Structural elucidation of these compounds was based on elementary analysis and spectral data studies. The newly synthesized compounds were evaluated for their antibacterial activities. 相似文献
97.
Escobar Jose M. Rane Kishore D. Cheryan Munir 《Applied biochemistry and biotechnology》2001,91(1-9):283-296
Pilot plant trials were conducted in a corn wet mill with a 7000-L membrane recycle bioreactor (MRB) that integrated ceramic
microfiltration membranes in a semi-closed loop configuration with a stirred-tank reactor. Residence times of 7.5–10 h with
ethanol outputs of 10–11.5% (v/v) were obtained when the cell concentration was 60–100 g/L drywt of yeast, equivalent to about
109−1010 cells/mL. The performance of the membrane was dependent on the startup mode and pressure management techniques. A steady
flux of 70 L/(m2·h) could be maintained for several days before cleaning was necessary. The benefits of the MRB include better productivity;
a clear productstream containing no particulates or yeast cells, which should improve subsequent stripping and distillation
operations; and substantially reduced stillage handling. The capital cost of the MRB is $21–$34/(m3·yr) ($0.08–$0.13/[gal·yr]) of ethanol capacity. Operating cost, including depreciation, energy, membrane replacement, maintenance,
labor, and cleaning, is $4.5–9/m3 ($0.017–$0.034/gal) of ethanol. 相似文献
98.
JPC – Journal of Planar Chromatography – Modern TLC - Gemcitabine belongs to a class of drugs known as antimetabolites (pyrimidine analog) used in various carcinomas, such as pancreatic... 相似文献
99.
The use of dimedone in green chemistry has been described for the synthesis of selective heterocyclic motifs which are both pharmacologically and industrially important. The objective of this review is to summarize some of the selected recent advances of dimedone in the synthesis of organic compounds utilizing green chemistry procedures. 相似文献
100.
In this paper, a modified sub-population teaching-learning-based optimization (MS-TLBO) algorithm is proposed to improve the exploration and exploitation capacities by including the concept of number of teachers, adaptive teaching factor, learning through tutorial, and self-motivated learning in the basic TLBO algorithm. The multiple frequency responses to the structural optimization problems are challenging due to its search space, which is implicit, nonconvex, nonlinear, and often leading to divergence. The viability and efficiency of the proposed method are tested by five structural benchmark problems of shape and size optimization with multiple natural frequency constraints on the planar and space trusses. The results reveal that MS-TLBO is more effective as compared to the original TLBO and other state-of-the-art algorithms. 相似文献