全文获取类型
收费全文 | 12086篇 |
免费 | 806篇 |
国内免费 | 518篇 |
专业分类
化学 | 3994篇 |
晶体学 | 50篇 |
力学 | 994篇 |
综合类 | 75篇 |
数学 | 5809篇 |
物理学 | 2488篇 |
出版年
2024年 | 14篇 |
2023年 | 191篇 |
2022年 | 162篇 |
2021年 | 344篇 |
2020年 | 453篇 |
2019年 | 400篇 |
2018年 | 422篇 |
2017年 | 478篇 |
2016年 | 432篇 |
2015年 | 369篇 |
2014年 | 645篇 |
2013年 | 1606篇 |
2012年 | 866篇 |
2011年 | 685篇 |
2010年 | 515篇 |
2009年 | 790篇 |
2008年 | 790篇 |
2007年 | 633篇 |
2006年 | 517篇 |
2005年 | 499篇 |
2004年 | 379篇 |
2003年 | 274篇 |
2002年 | 238篇 |
2001年 | 164篇 |
2000年 | 204篇 |
1999年 | 197篇 |
1998年 | 168篇 |
1997年 | 151篇 |
1996年 | 112篇 |
1995年 | 89篇 |
1994年 | 82篇 |
1993年 | 61篇 |
1992年 | 50篇 |
1991年 | 36篇 |
1990年 | 27篇 |
1989年 | 31篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 18篇 |
1985年 | 47篇 |
1984年 | 60篇 |
1983年 | 21篇 |
1982年 | 33篇 |
1981年 | 27篇 |
1980年 | 18篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
951.
Preparation and properties of reversible hydrogels based on triblock poly(amino acid)s with tunable pH‐responsivity across a broad range 下载免费PDF全文
952.
953.
The nano-palpation technique,i.e.,nanometer-scale elastic and viscoelastic measurements based on atomic force microscope,is introduced.It is demonstrated to be very useful in analyzing nanometer-scale materials properties for the surfaces and interfaces of various types of soft materials.It enables us to obtain not only structural information but also mechanical information about a material at the same place and at the same time. 相似文献
954.
Eleven chiral derivatizing reagents (CDRs) were used for preparation of diastereomers of (R,S)‐mexiletine containing a primary amino group in close proximity to the stereogenic center. One anhydride, namely [(S,S)‐O,O'‐di‐p‐toluoyl tartaric acid anhydride] was synthesized and (S)‐naproxen was used as such as the chiral derivatizing reagent. The other nine CDRs were synthesized by substituting one of the fluorine atoms in 1,5‐difluoro‐2,4‐dinitrobenzene with six amino acid amides and three amino acids. The diastereomers were separated by reversed‐phase high‐performance liquid chromatography. The method was validated for linearity, accuracy, limit of detection and limit of quantification. The limit of detection was found in the range of 10–30 pmol. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
955.
This paper considers the treatment of fluid–solid interaction problems under shock wave loading, where the solid experiences large bulk Lagrangian displacements. This work addresses the issues associated with using a level set as a generalized interface for fluid–solid coupling where the fluid–solid interface is embedded in an unstructured fluid grid. We outline the formulation used for the edge‐based unstructured‐grid Euler solver. The identification of the fluid–solid interface on the unstructured fluid mesh uses a super‐sampled ??2 projection technique, which in conjunction with a Lagrangian interface position, permits fast identification of the interface and the concomitant imposition of boundary conditions. The use of a narrow‐band approach for the identification of the wetted interface is presented with the details of the construction of interface conditions. A series of two and three‐dimensional shock‐body computations are presented to demonstrate the validity of the current approach on problems with static and dynamic interfaces, including projectile/shock interaction simulations. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
956.
István Juhász 《Topology and its Applications》2011,158(18):2460-2462
In this short note I attempt to describe some of the most important contributions of Ken Kunen to set-theoretic topology together with some of the highlights of our personal relationship. 相似文献
957.
Fernando Cuenú Rodrigo Abonia Alberto Bolaños 《Journal of organometallic chemistry》2011,696(9):1834-1839
The synthesis of a novel palladium (II) complex Pd4Cl8(PzTB)2, where PzTB is a pyrazole Tröger’s base analogue ligand is reported. A complete structure elucidation of the complex was achieved by spectroscopic and crystallographic data, exhibiting a metallomacrocycle supramolecular structure and a planar-square geometry on each palladium atom. This complex exhibited also a high activity and selectivity toward a model Mizoroki-Heck C-C coupling reaction of styrene with some iodobenzene derivatives. 相似文献
958.
《Journal of Coordination Chemistry》2012,65(19):3391-3401
Two BiBr3 supramolecular complexes, [Bi(2-bpmp)Br2.06Cl0.94] (1) and [Bi(4-H2bpmp)Br4.29Cl0.71]·H2O (2) {2-bpmp = N,N′-bis(2-pyridylmethyl)piperazine and 4-bpmp = N,N′-bis(4-pyridylmethyl)piperazine}, were prepared by reaction of bismuth(III) chloride and potassium bromide with two nitrogen donor ligands under thermal gradient conditions using the branched tube method. Compounds 1 and 2 were structurally characterized by single-crystal X-ray diffraction. In monomeric 1, bismuth is coordinated by two pyridyl and piperazine nitrogens of 2-bpmp, and by three halides. Compound 2 is also monomeric but is bonded to only one pyridyl nitrogen. In both compounds, extensive hydrogen-bonding interactions lead to supramolecular networks; in 2, the hydrogen bonds are augmented by π–π stacking interactions. Thermal stabilities of both compounds were studied by thermal gravimetric and differential thermal analyses. Thermal decomposition of nanosized 1 and 2 in air produced BiOBr nanoparticles. 相似文献
959.
960.
This paper deals with the mechanics involved in a spinning wheel of which the pivot is not fixed as usual but is forced to rotate along the circumference of a circle on the horizontal plane. The usual Euler equations are extended so that, in addition to the three well-known rotations (Euler angles), they also include a fourth one related to the rotation of the motor that induces the forced precession. This study aims at offering a first insight in one of the renowned Laithwaite's experiments. The derived theoretical expressions are accompanied by computer simulation. 相似文献