全文获取类型
收费全文 | 1155篇 |
免费 | 26篇 |
国内免费 | 9篇 |
专业分类
化学 | 726篇 |
晶体学 | 9篇 |
力学 | 31篇 |
数学 | 134篇 |
物理学 | 290篇 |
出版年
2023年 | 10篇 |
2022年 | 15篇 |
2021年 | 22篇 |
2020年 | 39篇 |
2019年 | 22篇 |
2018年 | 20篇 |
2017年 | 16篇 |
2016年 | 43篇 |
2015年 | 19篇 |
2014年 | 40篇 |
2013年 | 110篇 |
2012年 | 56篇 |
2011年 | 59篇 |
2010年 | 54篇 |
2009年 | 36篇 |
2008年 | 56篇 |
2007年 | 56篇 |
2006年 | 63篇 |
2005年 | 50篇 |
2004年 | 30篇 |
2003年 | 26篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 18篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1973年 | 8篇 |
1970年 | 6篇 |
排序方式: 共有1190条查询结果,搜索用时 15 毫秒
991.
Mukund G. Kulkarni Saryu I. Davawala Mahadev P. Shinde Attrimuni P. Dhondge Ajit S. Borhade Sanjay W. Chavhan Dnyaneshwar D. Gaikwad 《Tetrahedron letters》2006,47(18):3027-3029
A Wittig olefination-Claisen rearrangement strategy has been applied to achieve one of the shortest and efficient synthesis of (±)-β-cuparenone. 相似文献
992.
993.
Neelesh A. Kulkarni 《Tetrahedron》2007,63(33):7816-7822
The nucleophilic allylation of various chiral auxiliaries derived glyoxylic oxime ethers was studied. The use of allyltributylstannane in the presence of a Lewis acid and triallylaluminum provided the corresponding homoallylic amines in high chemical yields (up to 89%) and excellent stereoselectivities (up to >99%). The stereochemical bias of the allylation is proposed. 相似文献
994.
N.G. Dhere A.A. Kadam S.S. Kulkarni D. Groß E. Umbach 《Journal of Physics and Chemistry of Solids》2005,66(11):1872-1875
This paper presents a spectroscopic analysis of the interface between a CuIn1−xGaxS2 (CIGS2) absorber and a CdS buffer layer on stainless steel foil by Auger electron spectroscopy (AES), inverse photoemission spectroscopy (IPES) and photoelectron spectroscopy (PES) such as X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). By combining these spectroscopic techniques, detailed information about the electronic and chemical properties of the CIGS2 surface and the CdS/CIGS2 interface can be obtained. The gallium concentration in CIGS2 films was found to increase continuously towards the Mo back contact. XPS analysis showed the presence of KCO3 on the surface of CdS, deposited on etched and un-oxidized samples indicating diffusion of potassium. No potassium was observed on oxidized as well as samples having thicker CdS (50 nm) indicating the effectiveness of oxidation and chemical bath deposition (CBD) process in cleaning the sample surface effectively. In addition, investigation of the electronic level alignment at the interface has been carried out by combining PES and IPES. Conduction band offset of −0.45 (±0.15) eV and a valence band offset of −1.06 (±0.15) eV were measured. These unfavorable conditions limit efficiency of CIGS2 thin film solar cells. 相似文献
995.
Lalla Jogender Hamrapurkar Purnima Kulkarni Dhanashri Mamania Hemant 《平面色谱法杂志一现代薄层色谱法》2003,16(6):465-468
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
996.
Nitrogen ligands are an excellent alternative for the traditional P-ligands in the Pd catalyzed Mizoroki-Heck reaction. Pd complexes of dimethyl glyoxime, 8-hydroxyquinoline, salen, picolinic acid, DAB ligands gave high yields of the E-cinnamates and E-stilbenes. Acetophenone oxime N,N-dimethybenzyl amine and ferrocenyl oxime palladacycle were better catalysts and comparable yields, TON (95,000) and TOF's (2500 h−1) to P-ligand catalysts, were obtained. Aryl iodides, aryl bromides and in a few cases, aryl chlorides could be also be activated by these complexes by the use of Lewis acid and (C4H9)4NI as additive. DAB ligands gave good yields with electron rich aryl bromides and the use of ionic liquid improved the yield. These metal complexes can be readily synthesized and the N-ligands possess the advantage of easy functional group modifications and convenient synthetic methods compared to P-ligands. The degradation reactions associated with P-ligands is not observed in the N-ligands, with comparable high thermal, moisture and air stability and insensitivity. 相似文献
997.
998.
Gangaiah Mettela Summayya Kouser Chaitali Sow Prof. Sokrates T. Pantelides Prof. Giridhar U. Kulkarni 《Angewandte Chemie (International ed. in English)》2018,57(29):9018-9022
Conventional gold comprising the cubic lattice is universally known for its stability. However, well known to chemists and metallurgists, this nobility is challenged by reagents such as aqua regia, which dissolve gold to form a salt solution. Among metals, mercury blends with gold to form amalgam, otherwise transition metals such as copper tend to interact with gold surfaces in electrochemical media. Herein, we report a combined experimental and theoretical investigation of the stability of Au microcrystallites bearing unconventional crystal lattices that exhibit enhanced stability towards Hg and aqua regia and practically no interaction with Cu during electroless plating. The unconventional gold is undoubtedly nobler. 相似文献
999.
A Flexible Composite Mechanical Energy Harvester from a Ferroelectric Organoamino Phosphonium Salt
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Thangavel Vijayakanth Dr. Anant Kumar Srivastava Farsa Ram Priyangi Kulkarni Dr. Kadhiravan Shanmuganathan Dr. Balu Praveenkumar Prof. Dr. Ramamoorthy Boomishankar 《Angewandte Chemie (International ed. in English)》2018,57(29):9054-9058
A new binary organic salt diphenyl diisopropylamino phosphonium hexaflurophosphate (DPDP?PF6) was shown to exhibit a good ferroelectric response and employed for mechanical energy harvesting application. The phosphonium salt crystallizes in the monoclinic noncentrosymmetric space group Cc and exhibits an H‐bonded 1D chain structure due to N?H???F interactions. Ferroelectric measurements on the single crystals of DPDP?PF6 gave a well‐saturated rectangular hysteresis loop with a remnant (Pr) polarization value of 6 μC cm?2. Further, composite devices based on polydimethylsiloxane (PDMS) films for various weight percentages (3, 5, 7, 10 and 20 wt %) of DPDP?PF6 were prepared and examined for power generation by using an impact test setup. A maximum output peak‐to‐peak voltage (VPP) of 8.5 V and an output peak‐to‐peak current (IPP) of 0.5 μA was obtained for the non‐poled composite film with 10 wt % of DPDP?PF6. These results show the efficacy of organic ferroelectric substances as potential micropower generators. 相似文献
1000.
We prove relative versions of the symplectic capping theorem and sufficiency of Giroux’s criterion for Stein fillability and use these to study the 4-genus of knots. More precisely, suppose we have a symplectic 4-manifold X with convex boundary and a symplectic surface Σ in X such that ?Σ is a transverse knot in ?X. In this paper, we prove that there is a closed symplectic 4-manifold Y with a closed symplectic surface S such that (X,Σ) embeds into (Y,S) symplectically. As a consequence we obtain a relative version of the symplectic Thom conjecture. We also prove a relative version of the sufficiency part of Giroux’s criterion for Stein fillability, namely, we show that a fibered knot whose mondoromy is a product of positive Dehn twists bounds a symplectic surface in a Stein filling. We use this to study 4-genus of fibered knots in \(\mathbb {S}^{3} \). Further, we give a criterion for quasipositive fibered knots to be strongly quasipositive. 相似文献