全文获取类型
收费全文 | 45162篇 |
免费 | 5769篇 |
国内免费 | 4773篇 |
专业分类
化学 | 21826篇 |
晶体学 | 333篇 |
力学 | 1976篇 |
综合类 | 209篇 |
数学 | 3537篇 |
物理学 | 11422篇 |
综合类 | 16401篇 |
出版年
2024年 | 156篇 |
2023年 | 822篇 |
2022年 | 1258篇 |
2021年 | 1449篇 |
2020年 | 1438篇 |
2019年 | 1352篇 |
2018年 | 1180篇 |
2017年 | 1171篇 |
2016年 | 1775篇 |
2015年 | 1838篇 |
2014年 | 2414篇 |
2013年 | 2825篇 |
2012年 | 3392篇 |
2011年 | 3427篇 |
2010年 | 2568篇 |
2009年 | 2634篇 |
2008年 | 2802篇 |
2007年 | 2514篇 |
2006年 | 2234篇 |
2005年 | 2006篇 |
2004年 | 1545篇 |
2003年 | 1309篇 |
2002年 | 1379篇 |
2001年 | 1222篇 |
2000年 | 1087篇 |
1999年 | 1331篇 |
1998年 | 1115篇 |
1997年 | 1033篇 |
1996年 | 1019篇 |
1995年 | 915篇 |
1994年 | 769篇 |
1993年 | 660篇 |
1992年 | 567篇 |
1991年 | 536篇 |
1990年 | 479篇 |
1989年 | 405篇 |
1988年 | 348篇 |
1987年 | 222篇 |
1986年 | 152篇 |
1985年 | 112篇 |
1984年 | 65篇 |
1983年 | 44篇 |
1982年 | 39篇 |
1981年 | 27篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1972年 | 5篇 |
1957年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
Yuanbo Gao Tingting Yang Xueli Wang Jizong Chen Yong He 《Journal of polymer science. Part A, Polymer chemistry》2022,60(10):1610-1623
Two series of novel alternating copolyoxamides (PAnT-alt-n2 and PAn2-alt-62) are synthesized via solution/solid-state polycondensation (SSP). The alternating structures are analyzed carefully with 1H NMR and 13C NMR spectra. The melting behaviors, thermal stabilities, crystal structures and crystallinities are systematically evaluated by DSC, TGA and WAXD. The results reveal that these alternating copolyoxamides possess almost perfect alternating chain structures and have high melting temperature (Tm > 270 °C), high crystallinity (Xc > 32%) and high decomposition temperature (T5 > 405 °C) as well as low saturated water absorption (<3.5 wt%), which suggests that they have high potential as engineering plastic of high heat resistant. 相似文献
2.
Nonlinear Dynamics - The perovskite solar cell (PSC) is one of the most promising photovoltaic candidates along with the highly increasing demand for green electricity. One of the main concerns... 相似文献
3.
Yujie Gao Zhiye Qiu Lei Liu Mengmeng Li Bingjie Xu Dan Yu Dongming Qi Jindan Wu 《Journal of polymer science. Part A, Polymer chemistry》2022,60(15):2191-2212
Refractory wounds have always been an important issue to healthcare systems, whose healing process is always delayed by multiple factors, including bacterial infections, chronic inflammation, and excessive exudates, etc. Employing multifunctional wound dressings is recognized as an effective strategy to deal with refractory wounds, which has yielded promising outcomes in recent years. Among these advanced wound dressings, fibrous dressings have gained growing attention due to their unique merits. Such wound dressings have demonstrated great potential in delivering theranostic agents, such as antibacterial agents, anti-inflammatory drugs, growth factors, and diagnostic probes, etc., for the purposes of accelerating wound healing. This paper reviews the development of multifunctional fibrous dressings and their applications in treating refractory wounds. The construction approaches of novel fibrous dressing with capabilities of antibacterial, anti-inflammation, exudate management and diagnosis were also introduced. Furthermore, the existing problems and challenges are also discussed briefly. 相似文献
4.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
5.
Experimental Mechanics - Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients... 相似文献
6.
7.
Journal of Visualization - Forecast calibration methods based on historical similar atmospheric state are effective means weather forecast accuracy. Conventional approaches search similar forecasts... 相似文献
8.
为了构建共享自动驾驶汽车(shared autonomous vehicles,SAV) 的使用意愿模型并分析其影响因素,通过使用时机和使用频率来体现公众对SAV的使用意愿;采用验证性因子分析将态度潜变量转化为潜变量得分,以此将态度潜变量引入传统的有序Logit模型;提出SAV使用意愿的有序Logit模型构建方法,并建立基于个人属性、通勤特征、态度潜变量的SAV使用意愿模型.研究发现:是否使用过滴滴拼车、工作单位停车费、自动驾驶态度对使用时机和3种价格(1,2,3元/km) 下的使用频率有显著影响;使用过滴滴拼车、工作单位收取停车费、支持自动驾驶的群体倾向于频繁地、更早地使用SAV出行;公众期望以1元/km或 2元/km即不超过目前滴滴拼车的价格使用SAV. 相似文献
9.
Li Jun Zheng Dayong Wei Ning Sun Yunfeng Liu Li Yuan Yuan Jiang Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3).... 相似文献
10.
Nonlinear Dynamics - The nonlinear modes of a non-conservative nonlinear system are sometimes referred to as damped nonlinear normal modes (dNNMs). Because of the non-conservative... 相似文献