全文获取类型
收费全文 | 2685篇 |
免费 | 127篇 |
国内免费 | 10篇 |
专业分类
化学 | 1253篇 |
晶体学 | 21篇 |
力学 | 98篇 |
数学 | 552篇 |
物理学 | 449篇 |
无线电 | 449篇 |
出版年
2023年 | 32篇 |
2022年 | 75篇 |
2021年 | 102篇 |
2020年 | 128篇 |
2019年 | 108篇 |
2018年 | 91篇 |
2017年 | 71篇 |
2016年 | 178篇 |
2015年 | 99篇 |
2014年 | 128篇 |
2013年 | 161篇 |
2012年 | 192篇 |
2011年 | 159篇 |
2010年 | 90篇 |
2009年 | 90篇 |
2008年 | 110篇 |
2007年 | 97篇 |
2006年 | 92篇 |
2005年 | 89篇 |
2004年 | 76篇 |
2003年 | 58篇 |
2002年 | 60篇 |
2001年 | 34篇 |
2000年 | 37篇 |
1999年 | 24篇 |
1998年 | 24篇 |
1997年 | 16篇 |
1996年 | 24篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1993年 | 22篇 |
1992年 | 21篇 |
1991年 | 18篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 37篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 19篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1975年 | 10篇 |
1974年 | 9篇 |
排序方式: 共有2822条查询结果,搜索用时 578 毫秒
991.
Nhat-Khuong Nguyen Pradip Singha Dr. Jun Zhang Dr. Hoang-Phuong Phan Prof. Nam-Trung Nguyen Dr. Chin Hong Ooi 《Chemphyschem》2021,22(1):99-105
Liquid marbles are a promising microreactor platform that recently attracts significant research interest owing to their ability to accommodate a wide range of micro reactions. However, the use of destructive and ex-situ methods to monitor reactions impairs the potential of liquid-marble-based microreactors. This paper proposes a non-destructive, in situ, and cost-effective digital-imaging-based colourimetric monitoring method for transparent liquid marbles, using the enzymatic hydrolysis of starch as an illustrative example. The colourimetric reaction between starch and iodine produces a complex that exhibits a dark blue colour. We found that the absorbance of red channel of digital images showed a linear relationship with starch concentration with high sensitivity and repeatability. This digital-imaging-based colourimetric method was used to study the hydrolysis of starch by α-amylase. The results show high accuracy and applicability of first-order kinetics for this reaction. The demonstration of digital-imaging-based colourimetry indicates the potential of liquid marble-based microreactors. 相似文献
992.
Thuy Bui Thi Phuong My Tran Thi Ai Hai Nguyen Thi Thanh Loan Huynh Thi Phuong Hieu Le Trung Hoa Tran Thai Bui Thanh Q. Tuong Ho Nhat Thuy Nguyen Thi Thu Dung Doan Kim Van Tat Pham Quy Phan Tu Nhung Nguyen Thi Ai 《Structural chemistry》2021,32(1):135-148
Structural Chemistry - Rice, well known as the most important staple food source worldwide, is highly susceptible to many infectious diseases, especially rice sheath blight caused by fungus... 相似文献
993.
Hee Jae Shin Cao Van Anh Duk-Yeon Cho Dong-Kug Choi Jong Soon Kang Phan Thi Hoai Trinh Byeoung-Kyu Choi Hwa-Sun Lee 《Molecules (Basel, Switzerland)》2021,26(4)
Three new polyene compounds, talacyanols A–C (1–3), along with two known compounds, ramulosin (4) and eurothiocin A (5), were isolated from the marine fungus Talaromyces cyanescens derived from a seaweed Caulerpa sp. Structures of 1–5 were established by one-dimensional and two-dimensional (1D/2D) NMR, HR-ESIMS, and the modified Mosher’s methods, as well as comparison with previously reported literature data. All the compounds (1–5) were tested for their in vitro cytotoxic and anti-neuroinflammatory activities. Among them, 1 showed moderate cytotoxic activity against a panel of cancer cell lines (HCT-15, NUGC-3, NCI-H23, ACHN, PC-3, and MDA-MB-231) with GI50 values ranging from 44.4 to 91.6 μM, whereas compounds 2 and 5 exhibited anti-neuroinflammatory effect without cytotoxicity against all the tested cell lines. 相似文献
994.
Thi-Bich-Ngoc Dao Truong-Minh-Tri Nguyen Van-Quy Nguyen Thi-Minh-Dinh Tran Nguyen-Minh-An Tran Chuong Hoang Nguyen Thi-Hoai-Thu Nguyen Huu-Hung Nguyen Jirapast Sichaem Cong-Luan Tran Thuc-Huy Duong 《Molecules (Basel, Switzerland)》2021,26(9)
Combretum quadrangulare Kurz is widely used in folk medicine in Eastern Asia and is associated with various ethnopharmacological properties including hepatoprotective, antipyretic, analgesic, antidysenteric, and anthelmintic activities. Previous phytochemical investigations reported the presence of numerous triterpenes (mostly cycloartanes, ursanes, lupanes, and oleananes) along with dozens of flavonoids. However, the extracts of C. quadrangulare and isolated flavonoids have not been evaluated for their alpha-glucosidase inhibition. In the frame of our efforts dedicated to the chemical investigation of Vietnamese medicinal plants and their biological activities, a phytochemical study of the MeOH extract of the leaves of C. quadrangulare using bioactive guided isolation was undertaken. In this paper, the isolation and structure elucidation of twelve known compounds, 5-hydroxy-3,7,4′-trimethoxyflavone (1), ayanin (2), kumatakenin (3), rhamnocitrin (4), ombuin (5), myricetin-3,7,3′,5′-tetramethyl ether (6), gardenin D (7), luteolin (12), apigenin (13), mearnsetin (14), isoorientin (15), and vitexin (16) were reported. Bromination was applied to compounds 2 and 3 to provide four new synthetic analogues 8–11. All isolated and synthesized compounds were evaluated for alpha-glucosidase inhibition and antibacterial activity. Compounds 4 and 5 showed moderate antibacterial activity against methicillin-resistant Staphylococcus aureus while others were inactive. All compounds failed to reveal any activity toward extended spectrum beta-lactamase-producing Escherichia coli. Compounds 2, 4, 6–9, and 11–14 showed good alpha-glucosidase inhibition with IC50 values in the range of 30.5–282.0 µM. The kinetic of enzyme inhibition showed that 8 and 11 were noncompetitive type inhibition against alpha-glucosidase. In silico molecular docking model indicated that compounds 8 and 11 were potential inhibitors against enzyme α-glucosidase. 相似文献
995.
Minh-Tri Le Viet-Nham Hoang Dac-Nhan Nguyen Thi-Hoang-Linh Bui Thien-Vy Phan Phuong Nguyen-Hoai Huynh Thanh-Dao Tran Khac-Minh Thai 《Molecules (Basel, Switzerland)》2021,26(11)
ABCG2 is an ABC membrane protein reverse transport pump, which removes toxic substances such as medicines out of cells. As a result, drug bioavailability is an unexpected change and negatively influences the ADMET (absorption, distribution, metabolism, excretion, and toxicity), leading to multi-drug resistance (MDR). Currently, in spite of promising studies, screening for ABCG2 inhibitors showed modest results. The aim of this study was to search for small molecules that could inhibit the ABCG2 pump. We first used the WISS MODEL automatic server to build up ABCG2 homology protein from 655 amino acids. Pharmacophore models, which were con-structed based on strong ABCG2 inhibitors (IC50 < 1 μM), consist of two hydrophobic (Hyd) groups, two hydrogen bonding acceptors (Acc2), and an aromatic or conjugated ring (Aro|PiR). Using molecular docking method, 714 substances from the DrugBank and 837 substances from the TCM with potential to inhibit the ABCG2 were obtained. These chemicals maybe favor synthesized or extracted and bioactivity testing. 相似文献
996.
Mizushima Takanori Thach Tran Thi Cam Wen Woo Jie Ohkita Hironobu 《Plasma Chemistry and Plasma Processing》2021,41(2):607-617
Plasma Chemistry and Plasma Processing - A porous membrane-like alumina (MA) tube was employed as a catalyst to improve the energy efficiency of the oxidative decomposition of low-concentrated... 相似文献
997.
In this paper, we present analytical results for one-loop contributions to the decay processes \begin{document}$ H\rightarrow Z \nu_l\bar{\nu}_l $\end{document} ![]()
![]()
(for \begin{document}$ l = e, \mu, \tau $\end{document} ![]()
![]()
). The calculations are performed within the Standard Model framework in the 't Hooft-Veltman gauge. One-loop form factors are then written in terms of scalar one-loop functions in the standard notations of \begin{document}$ {\tt LoopTools}$\end{document} ![]()
![]()
. As a result, one-loop decay rates for the decay channels can be evaluated numerically by using the package. Furthermore, we analyze the signals of \begin{document}$ H\rightarrow Z \nu_l\bar{\nu}_l $\end{document} ![]()
![]()
via the production processes \begin{document}$ e^-e^+ \rightarrow ZH^* \rightarrow Z (H^* \rightarrow Z \nu_l\bar{\nu}_l) $\end{document} ![]()
![]()
, including the initial beam polarizations at future lepton colliders. The Standard Model backgrounds, such as the processes \begin{document}$ e^-e^+ \rightarrow \nu_l\bar{\nu}_l ZZ $\end{document} ![]()
![]()
, are also examined in this study. Numerical results indicate that one-loop corrections make contributions of approximately 10% to the decay rates. These are sizeable contributions and should be taken into account at future colliders. We show that the signals \begin{document}$ H\rightarrow Z\nu_l\bar{\nu}_l $\end{document} ![]()
![]()
are clearly visible at the center-of-mass energy \begin{document}$ \sqrt{s}=250 $\end{document} ![]()
![]()
GeV and are difficult to probe in higher-energy regions owing to the dominant backgrounds. 相似文献
998.
Duong Van-Hao Nguyen Thanh Duong Bui Loat Van Kim Thanh Tien Duong Thang Duc Hoang Duc Huu Musthafa M. Saiyad Nguyen Quyet Huu Kovacs Tibor Tran Hoai-Nam 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(2):805-814
Journal of Radioanalytical and Nuclear Chemistry - Understanding concentration and mobility behavior of radionuclides in soil and plant plays an important role and application. In this study,... 相似文献
999.
Nguyen Thi Thanh Chi Tran Thi Da Nguyen Van Ha 《Journal of Coordination Chemistry》2017,70(6):1008-1019
For the first time, eugenol, a natural bioactive allylphenol, was introduced into coordination with platinum(II) by replacement of ethylene from Zeise’s salt with eugenol (Eug). The obtained complex, K[PtCl3(Eug)] (1), was used as the key compound for preparation of the series of trans-[PtCl2(Eug)(Amine)] (2–11), [PtCl(Eug)(8-O-quinoline)] (12) and [PtCl(Eug)(2-O2C-quinoline)] (13). The synthesized complexes were characterized by elemental analyses, IR, 1H NMR, 13C NMR, HSQS, HMBC, NOESY, and MS spectra. In 1–13 eugenol coordinates with Pt(II) at ethylenic double bond of the allyl group, the donor N of the amines is in trans-position in comparison with the double bond. A display of the trans-effect on the chemical shift of 1H and 13C was remarked. Seven complexes were tested for cell in vitro cytotoxicity on human cancer cells. Complexes 3 and 12 exhibit high activities on Hep-G2 with IC50 = 3.12 and 5.29 μM; 12 gives high activity against KB, Lu and MCF-7 with IC50 = 0.43, 2.95 and 1.84 μM, respectively. Most of these IC50 are lower than those of cisplatin. 相似文献
1000.
In this paper, necessary optimality conditions in terms of upper and/or lower subdifferentials of both cost and constraint functions are derived for minimax optimization problems with inequality, equality and geometric constraints in the setting of non-differentiatiable and non-Lipschitz functions in Asplund spaces. Necessary optimality conditions in the fuzzy form are also presented. An application of the fuzzy necessary optimality condition is shown by considering minimax fractional programming problem. 相似文献