全文获取类型
收费全文 | 2194篇 |
免费 | 83篇 |
国内免费 | 15篇 |
专业分类
化学 | 1532篇 |
晶体学 | 2篇 |
力学 | 64篇 |
数学 | 269篇 |
物理学 | 425篇 |
出版年
2024年 | 7篇 |
2023年 | 23篇 |
2022年 | 70篇 |
2021年 | 75篇 |
2020年 | 79篇 |
2019年 | 76篇 |
2018年 | 46篇 |
2017年 | 45篇 |
2016年 | 102篇 |
2015年 | 80篇 |
2014年 | 87篇 |
2013年 | 127篇 |
2012年 | 140篇 |
2011年 | 165篇 |
2010年 | 85篇 |
2009年 | 118篇 |
2008年 | 144篇 |
2007年 | 135篇 |
2006年 | 131篇 |
2005年 | 115篇 |
2004年 | 71篇 |
2003年 | 56篇 |
2002年 | 74篇 |
2001年 | 17篇 |
2000年 | 31篇 |
1999年 | 22篇 |
1998年 | 12篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1974年 | 2篇 |
1971年 | 2篇 |
1933年 | 1篇 |
排序方式: 共有2292条查询结果,搜索用时 15 毫秒
51.
Julia Vallejo Alejandro Pascual‐Álvarez Dr. Joan Cano Dr. Isabel Castro Prof. Dr. Miguel Julve Prof. Dr. Francesc Lloret Dr. J. Krzystek Prof. Dr. Giovanni De Munno Dr. Donatella Armentano Prof. Dr. Wolfgang Wernsdorfer Dr. Rafael Ruiz‐García Dr. Emilio Pardo 《Angewandte Chemie (International ed. in English)》2013,52(52):14075-14079
52.
In this paper we present a-posteriori KAM results for existence of d-dimensional isotropic invariant tori for n-DOF Hamiltonian systems with additional independent first integrals in involution. We carry out a covariant formulation that does not require the use of action-angle variables nor symplectic reduction techniques. The main advantage is that we overcome the curse of dimensionality avoiding the practical shortcomings produced by the use of reduced coordinates, which may cause difficulties and underperformance when quantifying the hypotheses of the KAM theorem in such reduced coordinates. The results include ordinary and (generalized) iso-energetic KAM theorems. The approach is suitable to perform numerical computations and computer assisted proofs. 相似文献
53.
Electrochemical Sensing of Uric Acid Using Glassy Carbon Modified with Multiwall Carbon Nanotubes Dispersed in Polyethylenimine 下载免费PDF全文
Alejandro Gutiérrez Maria L. Lozano Laura Galicia Nancy F. Ferreyra Gustavo A. Rivas 《Electroanalysis》2014,26(10):2191-2196
This work reports the advantages of using glassy carbon electrodes modified with multiwall carbon nanotubes (MWCNT) dispersed in polyethylenimine (PEI). The presence of MWCNTs wrapped by PEI largely facilitated the strong adsorption of uric acid (UA) and allowed its highly sensitive and selective quantification even in the presence of high excess of ascorbic acid. The selected conditions for the electrochemical sensing were 5 s accumulation at ?0.300 V under stirring and quantification in a 0.050 M phosphate buffer solution pH 7.40 by differential pulse voltammetry adsorptive‐stripping after medium exchange. The platform allowed the successful application in the quantification of UA in urine. 相似文献
54.
55.
Flávia Mafra de Lima Regiane Albertini Yvana Dantas Antonio Luis Maia‐Filho Cristiano de Loura Santana Hugo Caire Castro‐Faria‐Neto Cristiane França Antonio Balbin Villaverde Flávio Aimbire 《Photochemistry and photobiology》2013,89(1):179-188
It remains unknown if the oxidative stress can be regulated by low‐level laser therapy (LLLT) in lung inflammation induced by intestinal reperfusion (i‐I/R). A study was developed in which rats were irradiated (660 nm, 30 mW, 5.4 J) on the skin over the bronchus and euthanized 2 h after the initial of intestinal reperfusion. Lung edema and bronchoalveolar lavage fluid neutrophils were measured by the Evans blue extravasation and myeloperoxidase (MPO) activity respectively. Lung histology was used for analyzing the injury score. Reactive oxygen species (ROS) was measured by fluorescence. Both expression intercellular adhesion molecule 1 (ICAM‐1) and peroxisome proliferator‐activated receptor‐y (PPARy) were measured by RT‐PCR. The lung immunohistochemical localization of ICAM‐1 was visualized as a brown stain. Both lung HSP70 and glutathione protein were evaluated by ELISA. LLLT reduced neatly the edema, neutrophils influx, MPO activity and ICAM‐1 mRNA expression. LLLT also reduced the ROS formation and oppositely increased GSH concentration in lung from i‐I/R groups. Both HSP70 and PPARy expression also were elevated after laser irradiation. Results indicate that laser effect in attenuating the acute lung inflammation is driven to restore the balance between the pro‐ and antioxidants mediators rising of PPARy expression and consequently the HSP70 production. 相似文献
56.
Chao Huang Steven M. Santana He Liu Neil H. Bander Benjamin G. Hawkins Brian J. Kirby 《Electrophoresis》2013,34(20-21):2970-2979
The capture of circulating tumor cells (CTCs) from cancer patient blood enables early clinical assessment as well as genetic and pharmacological evaluation of cancer and metastasis. Although there have been many microfluidic immunocapture and electrokinetic techniques developed for isolating rare cancer cells, these techniques are often limited by a capture performance tradeoff between high efficiency and high purity. We present the characterization of shear‐dependent cancer cell capture in a novel hybrid DEP–immunocapture system consisting of interdigitated electrodes fabricated in a Hele‐Shaw flow cell that was functionalized with a monoclonal antibody, J591, which is highly specific to prostate‐specific membrane antigen expressing prostate cancer cells. We measured the positive and negative DEP response of a prostate cancer cell line, LNCaP, as a function of applied electric field frequency, and showed that DEP can control capture performance by promoting or preventing cell interactions with immunocapture surfaces, depending on the sign and magnitude of the applied DEP force, as well as on the local shear stress experienced by cells flowing in the device. This work demonstrates that DEP and immunocapture techniques can work synergistically to improve cell capture performance, and it will aid in the design of future hybrid DEP–immunocapture systems for high‐efficiency CTC capture with enhanced purity. 相似文献
57.
A review of thermodynamic and flow liquid crystal models is presented and applied to a wide range of biological liquid crystals (BLCs), including helicoidal plywoods, biopolymer solutions and in vivo liquid crystals. The key characteristics of liquid crystals (self-assembly, packing, defects, functionalities, processability) are discussed in relation to biological materials and the strong correspondence between different synthetic and biological materials is discussed. Viscoelastic models for nematic and chiral nematics are reviewed and discussed in terms of key parameters that facilitate understanding and quantitative information from experimental measurements. The range and consistency of the predictions demonstrates that the use of mesoscopic liquid crystal models is an efficient tool to develop the science and biomimetic applications of mesogenic biological materials. 相似文献
58.
M. Carmen Pérez Morales Dr. Julieta V. Catalán Dr. Victoriano Domingo Prof. Martín Jaraíz Dr. M. Mar Herrador Dr. José F. Quílez del Moral Prof. José‐Luis López‐Pérez Prof. Alejandro F. Barrero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6598-6612
Treatment of germacrone ( 1 ) with different electrophiles, and of its epoxy derivatives germacrone‐4,5‐epoxide ( 2 ), germacrone‐1,10‐epoxide ( 3 ) and isogermacrone‐4,5‐epoxide ( 4 ) with Brönsted/Lewis acids and TiIII, gives rise to a great structural diversity. Thus, by using a maximum of two steps, the production of more than 40 compounds corresponding to 14 skeletons is described. Computational calculations rationalizing the structural divergence produced are also described. Finally, since some of the compounds generated are bioactive natural sesquiterpenes, the mechanisms of formation of these substances will provide new insights in their biosynthesis. 相似文献
59.
Angel Rentería-Gómez Alejandro Islas-JácomeJ. Oscar C. Jiménez-Halla Rocío Gámez-Montaño 《Tetrahedron letters》2014
A series of twelve novel 1-acetamide-5-methoxy-2-oxindoles were prepared in moderate to good yields (30–88%) by an Ugi-SN2 one pot process with a xanthate mediated free radical cyclization. Additionally, Density Functional Theory (DFT) based calculations were performed at UB3LYP/6-311G(d) level in order to rationalize the energy profile of the xanthate mediated free radical cyclization because the benzo-fused γ-lactams (ortho products) were obtained as sole regioisomers over the spiro β-lactams (ipso products). 相似文献
60.
Amanda S. Santana Diego B. Carvalho Nadla S. Cassemiro Luiz H. Viana Gabriela R. Hurtado Marcos S. Amaral Najla M. Kassab Palimécio G. Guerrero Jr. Sandro L. Barbosa Miguel J. Dabdoub Adriano C.M. Baroni 《Tetrahedron letters》2014
A simple synthesis of 3-iodothiophenes was demonstrated using a wide range of (Z)-thioenynes. The key step in the iodocyclofunctionalization was the selective reduction of the triple bond in (Z)-thioenynes by the addition of iodine as an electrophilic agent. The 3-iodothiophenes were obtained in good to excellent yields of 61–92%. The 3-iodothiophenes were used as substrates in Sonogashira cross-coupling reactions to obtain thiophene acetylenes. 相似文献