全文获取类型
收费全文 | 810篇 |
免费 | 33篇 |
国内免费 | 1篇 |
专业分类
化学 | 628篇 |
晶体学 | 4篇 |
力学 | 16篇 |
数学 | 96篇 |
物理学 | 100篇 |
出版年
2023年 | 12篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 19篇 |
2019年 | 28篇 |
2018年 | 10篇 |
2017年 | 12篇 |
2016年 | 22篇 |
2015年 | 27篇 |
2014年 | 15篇 |
2013年 | 33篇 |
2012年 | 68篇 |
2011年 | 59篇 |
2010年 | 23篇 |
2009年 | 13篇 |
2008年 | 45篇 |
2007年 | 45篇 |
2006年 | 50篇 |
2005年 | 67篇 |
2004年 | 51篇 |
2003年 | 31篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1974年 | 5篇 |
1963年 | 3篇 |
1960年 | 2篇 |
1937年 | 2篇 |
1935年 | 2篇 |
1932年 | 2篇 |
1927年 | 3篇 |
1926年 | 2篇 |
1918年 | 2篇 |
1915年 | 2篇 |
排序方式: 共有844条查询结果,搜索用时 15 毫秒
61.
Results and new theory are presented for the uncoated and coated facet reflectivity of a shallowly buried waveguide, taking account of the diffracting corner present at the air–semiconductor interface. The corner effects are shown to be most significant in the case of coated facets. The analysis also predicts the asymmetry introduced into the radiation pattern. 相似文献
62.
63.
64.
Xiangrong Xu Lee Koetzner Jamie Boulet Harry Maselli Jessica Beyenhof Gary Grover 《Biomedical chromatography : BMC》2009,23(9):973-979
A simple and sensitive analytical method using liquid chromatography–tandem mass spectrometry (LC/MS/MS) for determination of acetylsalicylic acid (aspirin, ASA) and its major metabolite, salicylic acid (SA), in animal plasma has been developed and validated. Both ASA and SA in plasma samples containing potassium fluoride were extracted using acetonitrile (protein precipitation) with 0.1% formic acid in it. 6‐Methoxysalicylic acid was used as the internal standard (IS). The compounds were separated on a reversed‐phase column. The multiple reaction monitoring mode was used with ion transitions of m/z 178.9 → 136.8, 137.0 → 93.0 and 167.0 → 123.0 for ASA, SA and IS, respectively. The lower limits of quantification for ASA and SA were 3 and 30 ng/mL, respectively. The developed method was successfully applied for the evaluation of pharmacokinetics of ASA and SA after p.o. and i.v. administration of 1 mg/kg to rats. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
65.
P. A. Kendall N. J. Mason 《Journal of Electron Spectroscopy and Related Phenomena》2001,120(1-3):27-31
Electron energy loss spectroscopy (EELS) has been used to study the photo-absorption spectrum of trifluoromethyl sulphur pentafluoride (SF5CF3) for the first time. Comparison is made with the EELS spectrum of sulphur hexafluoride (SF6). The photolysis of the compound is discussed with relevance to estimated lifetimes in the atmosphere. It is estimated that the lifetime of SF5CF3 is of the order of 1000 years. 相似文献
66.
Jamie Hunter Scott Rice Robert Lowe Christopher M. Pask Stuart Warriner Visuvanathar Sridharan 《Tetrahedron letters》2017,58(46):4400-4402
2′-Hydroxyacetophenone was alkylated with a range of substituted benzyl and heteroaryl alcohols to afford the corresponding C-alkylated products in good yields under microwave irradiation. The C-alkylated products were reacted with bromoacetonitrile to afford 2-amino-3-benzyl 1,4-naphthoquinone derivatives in moderate yields. 相似文献
67.
Early detection of (pre-)cancerous changes improves prognosis, therefore in the UK patients at high risk of developing gastrointestinal cancers are enrolled on endoscopic surveillance programmes or the Bowel Cancer Screening Programme. The current gold standard technique for the detection of pre-cancerous changes in the gastrointestinal tract is histopathological analysis of biopsy tissue collected at endoscopy. This relies upon subjective assessment of morphological changes within the excised tissue samples and poor targeting of pre-malignant lesions. Raman spectroscopy offers a number of potential advantages for in vivo assessment of tissue at endoscopy. The performance of a custom built Raman probe as a biopsy targeting tool has been evaluated using excised biopsy material. Multivariate classification models have been used to demonstrate the likely ability of a miniature, confocal, fibre optic Raman probe to be used as an optical biopsy tool at endoscopy to provide spectral information in clinically practicable timescales. This technique could facilitate improved targeting of excisional biopsy with associated clinical benefits. 相似文献
68.
Horsnell J Stonelake P Christie-Brown J Shetty G Hutchings J Kendall C Stone N 《The Analyst》2010,135(12):3042-3047
Sentinel Lymph Node Biopsy has become the standard surgical procedure for the sampling of axillary lymph nodes in breast cancer. Intra operative node assessment is currently not offered to the majority of patients but would allow definitive axillary surgery to take place immediately. This would confer benefits both to the patient and to the healthcare system. Our experimental study aims to demonstrate that a Raman spectroscopy probe device could overcome many of the disadvantages of current intra-operative analysis techniques. 38 axillary lymph nodes, 25 negative and 13 positive from 20 patients undergoing breast surgery for invasive breast cancer were assessed using a commercially available Raman spectroscopy probe. Spectra were assessed using principal component fed linear discriminant analysis trained by the histopathology results. Leave one node out cross validation achieved a sensitivity of up to 92% and a specificity of up to 100% in differentiating between normal and metastatic lymph nodes. 相似文献
69.
70.
Jamie YuLing Han Timothy Thatt Yang Tan Joachim Say Chye Loo 《Journal of nanoparticle research》2011,13(8):3441-3454
The aim of this study was to investigate the feasibility of the inverse micelles (IM) technique in producing protein-loaded
calcium phosphate nanoparticles (CaP NPs), and to compare this technique with the conventional co-precipitation (co-ppt) technique.
In this study, bovine serum albumin and lysozyme were used as model proteins. The results show that CaP NPs produced by IM
were shown to be spherical and homogenous in size of ~50 nm. Protein loading efficiency of the IM technique was shown to be
much higher than CaP NPs synthesized through co-ppt technique. X-ray photoelectron spectroscopy shows that proteins were not adsorbed onto the surface of IM-synthesized CaP NPs, which suggested
that the proteins were entrapped within the particle matrix. Release studies show that protein release was more rapid at lower
pH conditions (pH 5 and 6) than at physiological pH of 7.4. A burst release was observed for co-ppt CaP NPs, while a continuous
release of protein was observed for IM-produced CaP NPs. This study shows the superiority of the IM technique in preparing
pH responsive CaP NPs as nano-carriers. 相似文献