全文获取类型
收费全文 | 89976篇 |
免费 | 2390篇 |
国内免费 | 1574篇 |
专业分类
化学 | 33207篇 |
晶体学 | 922篇 |
力学 | 7287篇 |
综合类 | 92篇 |
数学 | 33109篇 |
物理学 | 19323篇 |
出版年
2023年 | 240篇 |
2022年 | 239篇 |
2021年 | 357篇 |
2020年 | 517篇 |
2019年 | 501篇 |
2018年 | 10740篇 |
2017年 | 10492篇 |
2016年 | 6650篇 |
2015年 | 1367篇 |
2014年 | 960篇 |
2013年 | 1215篇 |
2012年 | 4903篇 |
2011年 | 11574篇 |
2010年 | 6344篇 |
2009年 | 6763篇 |
2008年 | 7419篇 |
2007年 | 9508篇 |
2006年 | 933篇 |
2005年 | 1945篇 |
2004年 | 1955篇 |
2003年 | 2282篇 |
2002年 | 1370篇 |
2001年 | 566篇 |
2000年 | 537篇 |
1999年 | 401篇 |
1998年 | 386篇 |
1997年 | 309篇 |
1996年 | 362篇 |
1995年 | 293篇 |
1994年 | 246篇 |
1993年 | 210篇 |
1992年 | 149篇 |
1991年 | 172篇 |
1990年 | 149篇 |
1989年 | 121篇 |
1988年 | 115篇 |
1987年 | 104篇 |
1986年 | 103篇 |
1985年 | 96篇 |
1984年 | 71篇 |
1983年 | 51篇 |
1982年 | 64篇 |
1981年 | 57篇 |
1980年 | 53篇 |
1979年 | 51篇 |
1978年 | 44篇 |
1914年 | 45篇 |
1913年 | 41篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
101.
Scalable Synthesis of Piperazines Enabled by Visible‐Light Irradiation and Aluminum Organometallics 下载免费PDF全文
Dr. Samuel Suárez‐Pantiga Kilian Colas Dr. Magnus J. Johansson Dr. Abraham Mendoza 《Angewandte Chemie (International ed. in English)》2015,54(47):14094-14098
The development of more active C? H oxidation catalysts has inspired a rapid, scalable, and stereoselective assembly of multifunctional piperazines through a [3+3] coupling of azomethine ylides. A combination of visible‐light irradiation and aluminum organometallics is essential to promote this transformation, which introduces visible‐light photochemistry of main‐group organometallics and sets the basis for new and promising catalysts. 相似文献
102.
Pingping Hu Dr. Manfred Erwin Schuster Dr. Zhiwei Huang Fei Xu Dr. Shifeng Jin Yaxin Chen Prof. Weiming Hua Prof. Dang Sheng Su Prof. Xingfu Tang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9619-9623
The identification of catalytically active sites (CASs) in heterogeneous catalysis is of vital importance to design and develop improved catalysts, but remains a great challenge. The CASs have been identified in the low‐temperature selective catalytic reduction of nitrogen oxides by ammonia (SCR) over a hollandite manganese oxide (HMO) catalyst with a rod‐shaped morphology and one‐dimensional tunnels. Electron microscopy and synchrotron X‐ray diffraction determine the surface and crystal structures of the one‐dimensional HMO rods closed by {100} side facets and {001} top facets. A combination of X‐ray absorption spectra, molecular probes with potassium and nitric oxide, and catalytic tests reveals that the CASs are located on the {100} side facets of the HMO rods rather than on the top facets or in the tunnels, and hence semi‐tunnel structural motifs on the {100} facets are evidenced to be the CASs of the SCR reaction. This work paves the way to further investigate the intrinsic mechanisms of SCR reactions. 相似文献
103.
104.
Glycans are chains of carbohydrates attached to proteins (glycoproteins and proteoglycans) or lipids (glycolipids). Glycosylation is a post-translational modification and glycans have a wide range of functions in the human body including involvement in oncological diseases. Change in a glycan structure can not only indicate the presence of a pathological process but, more importantly, in some cases also its stage. Thus, a glycan analysis has the potential to be an effective and reliable tool in cancer diagnostics. Lectins are proteins responsible for natural biorecognition of glycans; even carbohydrate moieties still attached to proteins or whole cells can be recognised by lectins, which makes them an ideal candidate for designing label-free biosensors for glycan analysis. This review seeks to summarise evidence that the glycoprofiling of biomarkers by lectin-based biosensors can be of significant help in detecting prostate cancer. 相似文献
105.
106.
107.
In Situ Proteome Profiling and Bioimaging Applications of Small‐Molecule Affinity‐Based Probes Derived From DOT1L Inhibitors 下载免费PDF全文
Biwei Zhu Dr. Hailong Zhang Sijun Pan Chenyu Wang Dr. Jingyan Ge Prof. Dr. Jun‐Seok Lee Prof. Dr. Shao Q. Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(23):7824-7836
DOT1L is the sole protein methyltransferase that methylates histone H3 on lysine 79 (H3K79), and is a promising drug target against cancers. Small‐molecule inhibitors of DOT1L such as FED1 are potential anti‐cancer agents and useful tools to investigate the biological roles of DOT1L in human diseases. FED1 showed excellent in vitro inhibitory activity against DOT1L, but its cellular effect was relatively poor. In this study, we designed and synthesized photo‐reactive and “clickable” affinity‐based probes (AfBPs), P1 and P2 , which were cell‐permeable and structural mimics of FED1 . The binding and inhibitory effects of these two probes against DOT1L protein were extensively investigated in vitro and in live mammalian cells (in situ). The cellular uptake and sub‐cellular localization properties of the probes were subsequently studied in live‐cell imaging experiments, and our results revealed that, whereas both P1 and P2 readily entered mammalian cells, most of them were not able to reach the cell nucleus where functional DOT1L resides. This offers a plausible explanation for the poor cellular activity of FED1 . Finally with P1 / P2 , large‐scale cell‐based proteome profiling, followed by quantitative LC‐MS/MS, was carried out to identify potential cellular off‐targets of FED1 . Amongst the more than 100 candidate off‐targets identified, NOP2 (a putative ribosomal RNA methyltransferase) was further confirmed to be likely a genuine off‐target of FED1 by preliminary validation experiments including pull‐down/Western blotting (PD/WB) and cellular thermal shift assay (CETSA). 相似文献
108.
109.
110.
Prashanth Shivappa Adarakatti Pandurangappa Malingappa 《Journal of Solid State Electrochemistry》2016,20(12):3349-3358
Amino-calixarene-derivatized graphitic carbon electrode has been used in the simultaneous quantification of lead and cadmium ions at picomolar level. The graphitic carbon has been chemically modified using amino-calixarene as an indicator molecule through microwave irradiation, and it has been characterized by NMR, mass, and Fourier transform infrared spectroscopy (FTIR) techniques. The proposed sensor has shown linearity in the concentration range 10–120 pM with detection limits of 3.3 and 3.5 pM for lead and cadmium, respectively. The proposed sensor has been successfully applied to quantify lead and cadmium levels in battery effluents, alloy materials, and sewage water sample matrices. The results obtained by the proposed sensor are in agreement with the results of the standard protocols. 相似文献