全文获取类型
收费全文 | 1345篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
化学 | 686篇 |
晶体学 | 14篇 |
力学 | 81篇 |
数学 | 115篇 |
物理学 | 477篇 |
出版年
2023年 | 9篇 |
2022年 | 16篇 |
2021年 | 17篇 |
2020年 | 21篇 |
2019年 | 19篇 |
2018年 | 15篇 |
2017年 | 21篇 |
2016年 | 27篇 |
2015年 | 18篇 |
2014年 | 41篇 |
2013年 | 81篇 |
2012年 | 70篇 |
2011年 | 71篇 |
2010年 | 46篇 |
2009年 | 56篇 |
2008年 | 60篇 |
2007年 | 54篇 |
2006年 | 42篇 |
2005年 | 44篇 |
2004年 | 36篇 |
2003年 | 28篇 |
2002年 | 16篇 |
2001年 | 17篇 |
2000年 | 17篇 |
1999年 | 15篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 20篇 |
1990年 | 13篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 17篇 |
1980年 | 15篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1976年 | 20篇 |
1975年 | 12篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1936年 | 13篇 |
排序方式: 共有1373条查询结果,搜索用时 15 毫秒
81.
A new phenanthroindolizidine alkaloid, 3-O-demethyl tylophorinidine (VI), was isolated from the aerial (leaves and stem) parts of Tylophora indica and characterized using different spectral techniques. Gel chromatography and reverse phase preparative HPLC were used for sample purification. The new alkaloid, VI, was screened for anticancer activity against a panel of different cancer cell lines and it showed significant anticancer activity with IC50 value in the range of 0.89?C1.40 ??M. 相似文献
82.
The minimal supersymmetric standard model with soft breaking has a large landscape of supersymmetric particle mass hierarchies. This number is reduced significantly in well-motivated scenarios such as minimal supergravity and alternatives. We carry out an analysis of the landscape for the first four lightest particles and identify at least 16 mass patterns, and provide benchmarks for each. We study the signature space for the patterns at the CERN Large Hadron Collider by analyzing the lepton+ (jet> or =2) + missing P{T} signals with 0, 1, 2, and 3 leptons. Correlations in missing P{T} are also analyzed. It is found that even with 10 fb{-1} of data a significant discrimination among patterns emerges. 相似文献
83.
84.
Francescone David Akula Sujeet Altunkaynak Baris Nath Pran 《Journal of High Energy Physics》2015,2015(1):1-48
Journal of High Energy Physics - We consider the AdS 2 /CFT 1 holographic correspondence near the horizon of rotating five-dimensional black holes preserving four supersymmetries in $$... 相似文献
85.
Chandran Rankan Prabhakaran Santhi Marimuthu Keshri Nath Tiwari 《Journal of heterocyclic chemistry》2020,57(6):2628-2633
A greener, rapid and regioselective “on water” synthesis of spirooxindole-oxazoline by the reaction of isatin and isocyanoacetate at room temperature is described. The developed protocol has the advantage of being atom-economical, eco-friendly, and benign reaction conditions. Broader substrate scope, experimentally simple procedures, and easy purification of products with high yield further make this method attractive. The synthesized compounds have been fully characterized with spectral analysis. 相似文献
86.
Neha Batra Vinoth Rajendran Ishan Wadi Ankit Lathwal Roshan Kumar Dutta Prahlad C. Ghosh Rinkoo D. Gupta Mahendra Nath 《Journal of heterocyclic chemistry》2020,57(4):1625-1636
A series of benzenesulfonamide-appended [1,2,3]-triazole hybrids was synthesized by using [3 + 2] cycloaddition of primary, secondary, and tertiary sulfonamide azides with various phenoxymethylacetylenes under click reaction conditions. After structural characterization, the compounds were subjected to in-silico absorption, distribution, metabolism, excretion and toxicity (ADMET) screening to evaluate their drug-likeness and other pharmacokinetic parameters. Furthermore, their in vitro antiplasmodial potential was assessed against Plasmodium falciparum (3D7) strain, and some of the synthesized compounds displayed promising antimalarial potency. On cytotoxicity evaluation using MTT cell viability assay, the most active candidate N-(4,6-dimethylpyridin-2-yl)-4-(4-(4-nitrophenoxy)methyl)-1H-[1,2,3]-triazol-1-yl)benzenesulfonamide ( 14 ; IC50 6.2 μg/mL) demonstrated CC50 7.5 μg/mL against human hepatocarcinoma (HUH-7) cells. 相似文献
87.
The excellent properties of Methyl Ammonium Lead Iodide (MAPI) have already created an extensive research interest in photovoltaic applications. However, their utility in thermoelectric application is still not realized thoroughly by researchers. By continuing this interest, we have explored the formation of low dimensional CH3NH3PbI3 (MAPI) perovskite in presence of Polyaniline (PANI) and Multi-Walled Carbon Nanotubes (MWCNT) and its thermoelectric performance. For this purpose, a two stage, in-situ synthesis method was developed to prepare various composites such as MAPI-PANI, MWCNT-MAPI and MWCNT-PANI-MAPI. The as-formed MWCNT-PANI-MAPI composite revealed p-type conductivity with enhanced ZT (up to ~20,000 times) and power factor (3000 times) at room temperature as compared to pristine MAPI sample. Finally, we have demonstrated a proto-type thermoelectric power generator (TE device) fabricated using the best performing composite sample and measured its power output and efficiency at varied δT. 相似文献
88.
89.
S. S. Nath D. Chakdar G. Gope A. Talukdar D. K. Avasthi 《Journal of Dispersion Science and Technology》2013,34(7):1111-1113
We report synthesis of ZnS quantum dots by chemical method at room temperature. In this technique, ZnS quantum dots are produced by simple chemical reactions where zeolite, acts as matrix, plays the key role in controlling particle growth during synthesis. Quantum dots exhibit luminescence properties such as Zn2+ related emission, efficient low voltage electroluminescence, and super linear voltage-brightness EL characteristics. This study demonstrates the technological importance of semiconductor nanosystems prepared by low cost chemical route. 相似文献
90.
S. K. Deb?Nath Hironori Tohmyoh M. A. Salam?Akanda 《Applied Physics A: Materials Science & Processing》2011,103(2):493-496
A testing methodology to determine the elastic-plastic properties of thin metallic wires is reported. A small-scaled bending
test of Pt thin wire and the corresponding finite element analysis are performed. By fitting the load-displacement relationship
obtained by finite element analysis to the experimental one, the elastic, elastic-plastic properties of Pt wire are successfully
determined. 相似文献