全文获取类型
收费全文 | 8363篇 |
免费 | 314篇 |
国内免费 | 25篇 |
专业分类
化学 | 5867篇 |
晶体学 | 29篇 |
力学 | 134篇 |
数学 | 1190篇 |
物理学 | 1482篇 |
出版年
2022年 | 67篇 |
2021年 | 119篇 |
2020年 | 156篇 |
2019年 | 153篇 |
2018年 | 101篇 |
2017年 | 94篇 |
2016年 | 264篇 |
2015年 | 202篇 |
2014年 | 226篇 |
2013年 | 353篇 |
2012年 | 461篇 |
2011年 | 576篇 |
2010年 | 292篇 |
2009年 | 228篇 |
2008年 | 420篇 |
2007年 | 442篇 |
2006年 | 415篇 |
2005年 | 401篇 |
2004年 | 301篇 |
2003年 | 221篇 |
2002年 | 232篇 |
2001年 | 106篇 |
2000年 | 103篇 |
1999年 | 93篇 |
1998年 | 87篇 |
1997年 | 74篇 |
1996年 | 92篇 |
1995年 | 109篇 |
1994年 | 88篇 |
1993年 | 97篇 |
1992年 | 84篇 |
1991年 | 58篇 |
1990年 | 69篇 |
1989年 | 95篇 |
1988年 | 60篇 |
1987年 | 74篇 |
1986年 | 77篇 |
1985年 | 103篇 |
1984年 | 78篇 |
1983年 | 69篇 |
1982年 | 81篇 |
1981年 | 67篇 |
1980年 | 77篇 |
1979年 | 91篇 |
1978年 | 91篇 |
1977年 | 99篇 |
1976年 | 77篇 |
1975年 | 59篇 |
1974年 | 61篇 |
1973年 | 81篇 |
排序方式: 共有8702条查询结果,搜索用时 15 毫秒
1.
Timm Bergholz Dr. Benjamin Oelkers Dr. Benedikt Huber Prof. Bernhard Roling Prof. Dr. Jörg Sundermeyer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2613-2620
New salts based on imidazolium, pyrrolidinium, phosphonium, guanidinium, and ammonium cations together with the 5‐cyanotetrazolide anion [C2N5]? are reported. Depending on the nature of cation–anion interactions, characterized by XRD, the ionic liquids (ILs) have a low viscosity and are liquid at room temperature or have higher melting temperatures. Thermogravimetric analysis, cyclic voltammetry, viscosimetry, and impedance spectroscopy display a thermal stability up to 230 °C, an electrochemical window of 4.5 V, a viscosity of 25 mPa s at 20 °C, and an ionic conductivity of 5.4 mS cm?1 at 20 °C for the IL 1‐butyl‐1‐methylpyrrolidinium 5‐cyanotetrazolide [BMPyr][C2N5]. On the basis of these results, the synthesized compounds are promising electrolytes for lithium‐ion batteries. 相似文献
2.
Archiv der Mathematik - Motivated by recent results on the minimal base of a permutation group, we introduce a new local invariant attached to arbitrary finite groups. More precisely, a subset... 相似文献
3.
4.
Daniel Heinz Annette Meister Hazrat Hussain Karsten Busse Jörg Kressler 《Journal of polymer science. Part A, Polymer chemistry》2020,58(23):3322-3335
Adding perfluoroalkyl (PF) segments to amphiphilic copolymers yields triphilic copolymers with new application profiles. Usually, PF segments are attached as terminal blocks via Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC). The purpose of the current study is to design new triphilic architectures with a PF segment in central position. The PF segment bearing bifunctional atom transfer radical polymerization (ATRP) initiator is employed for the fabrication of triphilic poly(propylene oxide)-b-poly(glycerol monomethacrylate)-b-PF-b-poly(glycerol monomethacrylate)-b-poly(propylene oxide) PPO-b-PGMA-b-PF-b-PGMA-b-PPO pentablock copolymers by a combined ATRP and CuAAC reaction approach. Differential scanning calorimetry indicates the PF-initiator to undergo a solid–solid phase transition at 63°C before the final crystal melting at 95°C. This is further corroborated by polarized optical microscopy and X-ray diffraction studies. The PF-initiator could successfully polymerize solketal methacrylate (SMA) under typical ATRP conditions producing well-defined Br-PSMA-b-PF-b-PSMA-Br triblock copolymers that are then converted into PPO-b-PSMA-b-PF-b-PSMA-b-PPO pentablock copolymer via CuAAC reaction. Subsequently, acid hydrolysis of the PSMA blocks afforded water soluble well-defined triphilic pentablock copolymers PPO-b-PGMA-b-PF-b-PGMA-b-PPO with fluorophilic central segment, hydrophilic middle blocks, and lipophilic outer blocks. The triphilic block copolymers could self-assemble, depending upon the preparatory protocol, into spherical and filament-like phase-separated nanostructures as revealed by transmission electron microscopy. 相似文献
5.
6.
7.
In complex biological systems, entities that are conceptually distinct but empirically related—such as sunlight and plant growth or antigene and immune response—are being explicitly linked through the identification of highly specific uninterrupted interaction sequences that take place between their macromolecular system components. These uninterrupted sequences of causation include common elements that are shared by the empirically related but conceptually distinct entities. Through the identification of specific shared elements, “conceptual continuity” is established between these entities. Examples are introduced to suggest that in sociopolitical systems, an analogous conceptual continuity can be established between distinct sociopolitical entities. The identification of specific shared elements, essential for the well being of each of the entities, can play a significant role in resolving conflicts between those separated by seemingly insurmountable obstacles such as race or religion or ideology. © 2006 Wiley Periodicals, Inc. Complexity 11:20–24, 2006 相似文献
8.
Benjamin J. K. Evans Susan M. Scott Antony C. Searle 《General Relativity and Gravitation》2002,34(10):1675-1684
We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time. 相似文献
9.
10.
Benjamin E. Blass Anil Srivastava Amy L. Faulkner James M. Ridgeway 《Tetrahedron letters》2004,45(6):1275-1277
The solid-phase synthesis of a series of imidazo[1,2-b]pyrazol-2-ones, an interesting 5,5-fused ring system, based on diverse set of hydrazine acids and malanonitriles is described. The method involves formation of 5-aminopyrazoles on solid support and subsequent cyclizative cleavage off the resin. Compounds were obtained in acceptable to excellent yields and are suitable for biological evaluation without further purification. 相似文献