全文获取类型
收费全文 | 53419篇 |
免费 | 1850篇 |
国内免费 | 366篇 |
专业分类
化学 | 37825篇 |
晶体学 | 455篇 |
力学 | 1049篇 |
综合类 | 2篇 |
数学 | 8859篇 |
物理学 | 7445篇 |
出版年
2022年 | 425篇 |
2021年 | 615篇 |
2020年 | 876篇 |
2019年 | 875篇 |
2018年 | 595篇 |
2017年 | 561篇 |
2016年 | 1323篇 |
2015年 | 1166篇 |
2014年 | 1430篇 |
2013年 | 2596篇 |
2012年 | 3093篇 |
2011年 | 3651篇 |
2010年 | 1911篇 |
2009年 | 1676篇 |
2008年 | 3220篇 |
2007年 | 3129篇 |
2006年 | 3120篇 |
2005年 | 2931篇 |
2004年 | 2512篇 |
2003年 | 2082篇 |
2002年 | 2015篇 |
2001年 | 726篇 |
2000年 | 710篇 |
1999年 | 625篇 |
1998年 | 605篇 |
1997年 | 660篇 |
1996年 | 722篇 |
1995年 | 533篇 |
1994年 | 570篇 |
1993年 | 569篇 |
1992年 | 496篇 |
1991年 | 453篇 |
1990年 | 395篇 |
1989年 | 349篇 |
1988年 | 346篇 |
1987年 | 375篇 |
1986年 | 312篇 |
1985年 | 569篇 |
1984年 | 568篇 |
1983年 | 455篇 |
1982年 | 556篇 |
1981年 | 513篇 |
1980年 | 463篇 |
1979年 | 414篇 |
1978年 | 435篇 |
1977年 | 371篇 |
1976年 | 361篇 |
1975年 | 334篇 |
1974年 | 320篇 |
1973年 | 261篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
1.
Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function... 相似文献
2.
3.
In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography. 相似文献
4.
Cavitation erosion is caused in solids exposed to strong pressure waves developing in an adjacent fluid field. The knowledge of the transient distribution of stresses in the solid is important to understand the cause of damaging by comparisons with breaking points of the material. The modeling of this problem requires the coupling of the models for the fluid and the solid. For this purpose, we use a strategy based on the solution of coupled Riemann problems that has been originally developed for the coupling of 2 fluids. This concept is exemplified for the coupling of a linear elastic structure with an ideal gas. The coupling procedure relies on the solution of a nonlinear equation. Existence and uniqueness of the solution is proven. The coupling conditions are validated by means of quasi‐1D problems for which an explicit solution can be determined. For a more realistic scenario, a 2D application is considered where in a compressible single fluid, a hot gas bubble at low pressure collapses in a cold gas at high pressure near an adjacent structure. 相似文献
5.
6.
7.
8.
Inside Cover: Ru‐Catalysed CH Arylation of Indoles and Pyrroles with Boronic Acids: Scope and Mechanistic Studies (Chem. Eur. J. 14/2015) 下载免费PDF全文
9.
Md. Zia Uddin Arkajyoti Paul Ahmed Rakib Saad Ahmed Sami Shafi Mahmud Md. Sohel Rana Shahadat Hossain Abu Montakim Tareq Mycal Dutta Talha Bin Emran Jesus Simal-Gandara 《Molecules (Basel, Switzerland)》2021,26(4)
The current study attempted, for the first time, to qualitatively and quantitatively determine the phytochemical components of Elatostema papillosum methanol extract and their biological activities. The present study represents an effort to correlate our previously reported biological activities with a computational study, including molecular docking, and ADME/T (absorption, distribution, metabolism, and excretion/toxicity) analyses, to identify the phytochemicals that are potentially responsible for the antioxidant, antidepressant, anxiolytic, analgesic, and anti-inflammatory activities of this plant. In the gas chromatography-mass spectroscopy analysis, a total of 24 compounds were identified, seven of which were documented as being bioactive based on their binding affinities. These seven were subjected to molecular docking studies that were correlated with the pharmacological outcomes. Additionally, the ADME/T properties of these compounds were evaluated to determine their drug-like properties and toxicity levels. The seven selected, isolated compounds displayed favorable binding affinities to potassium channels, human serotonin receptor, cyclooxygenase-1 (COX-1), COX-2, nuclear factor (NF)-κB, and human peroxiredoxin 5 receptor proteins. Phytol acetate, and terpene compounds identified in E. papillosum displayed strong predictive binding affinities towards the human serotonin receptor. Furthermore, 3-trifluoroacetoxypentadecane showed a significant binding affinity for the KcsA potassium channel. Eicosanal showed the highest predicted binding affinity towards the human peroxiredoxin 5 receptor. All of these findings support the observed in vivo antidepressant and anxiolytic effects and the in vitro antioxidant effects observed for this extract. The identified compounds from E. papillosum showed the lowest binding affinities towards COX-1, COX-2, and NF-κB receptors, which indicated the inconsequential impacts of this extract against the activities of these three proteins. Overall, E. papillosum appears to be bioactive and could represent a potential source for the development of alternative medicines; however, further analytical experiments remain necessary. 相似文献
10.
Daylight photodynamic therapy (DPDT) is an effective and patient preferred treatment for the management of field change actinic keratosis. An important factor in DPDT is light dosimetry, to ensure that patients receive sufficient daylight for effective treatment, and this is the focus of the contribution to this issue by (La Rochelle et al. [2019] Photochem. Photobiol., https://doi.org/10.1111/php.13170 ). In this work, the authors present an easy-to-use method for obtaining real-time information about patient received light dose during treatment and for determining indoor locations best suited to DPDT. 相似文献