全文获取类型
收费全文 | 306959篇 |
免费 | 12640篇 |
国内免费 | 2276篇 |
专业分类
化学 | 187120篇 |
晶体学 | 4097篇 |
力学 | 10987篇 |
综合类 | 2篇 |
数学 | 34633篇 |
物理学 | 85036篇 |
出版年
2021年 | 1948篇 |
2020年 | 3400篇 |
2019年 | 4766篇 |
2018年 | 3776篇 |
2017年 | 3362篇 |
2016年 | 7780篇 |
2015年 | 6548篇 |
2014年 | 7879篇 |
2013年 | 16635篇 |
2012年 | 12027篇 |
2011年 | 13544篇 |
2010年 | 9983篇 |
2009年 | 9718篇 |
2008年 | 12740篇 |
2007年 | 12225篇 |
2006年 | 11059篇 |
2005年 | 10540篇 |
2004年 | 9284篇 |
2003年 | 8248篇 |
2002年 | 8781篇 |
2001年 | 9050篇 |
2000年 | 7122篇 |
1999年 | 4943篇 |
1998年 | 3943篇 |
1997年 | 3945篇 |
1996年 | 3762篇 |
1995年 | 3543篇 |
1994年 | 3426篇 |
1993年 | 3538篇 |
1992年 | 3753篇 |
1991年 | 3651篇 |
1990年 | 3468篇 |
1989年 | 3416篇 |
1988年 | 3461篇 |
1987年 | 3327篇 |
1986年 | 3205篇 |
1985年 | 4401篇 |
1984年 | 4558篇 |
1983年 | 3779篇 |
1982年 | 4106篇 |
1981年 | 4026篇 |
1980年 | 3880篇 |
1979年 | 3882篇 |
1978年 | 4138篇 |
1977年 | 3939篇 |
1976年 | 4096篇 |
1975年 | 3671篇 |
1974年 | 3795篇 |
1973年 | 4114篇 |
1972年 | 2465篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Yeong‐Tarng Shieh Pei‐Yu Tai Chih‐Chia Cheng 《Journal of polymer science. Part A, Polymer chemistry》2019,57(21):2149-2156
Poly(methyl methacrylate) (PMMA) nanoparticles with a sensitive CO2‐responsive hydrophilic/hydrophobic surface that confers controlled dispersion and aggregation in water were prepared by emulsion polymerization at 50 °C under CO2 bubbling using amphiphilic diblock copolymers of 2‐dimethylaminoethyl methacrylate (DMAEMA) and N‐isopropyl acrylamide (NIPAAm) as an emulsifier. The amphiphilicity of the hydrophobic–hydrophilic diblock copolymer at 50 °C was triggered by CO2 bubbling in water and enabled the copolymer to serve as an emulsifier. The resulting PMMA nanoparticles were spherical, approximately 100 nm in diameter and exhibited sensitive CO2/N2‐responsive dispersion/aggregation in water. Using copolymers with a longer PNIPAAm block length as an emulsifier resulted in smaller particles. A higher concentration of copolymer emulsifier led to particles with a stickier surface. Given its simple preparation and reversible CO2‐triggered amphiphilic behavior, this newly developed block copolymer emulsifier offers a highly efficient route toward the fabrication of sensitive CO2‐stimuli responsive polymeric nanoparticle dispersions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2149–2156 相似文献
92.
K.M.J. Rocha R.G. Leitão E.G. Oliveira-Barros M.A. Oliveira C.G.L. Canellas M.J. Anjos L.E. Nasciutti R.T. Lopes 《X射线光谱测定》2019,48(5):476-481
Prostate cancer is a highly prevalent disease and ranks second among malignant neoplasms that affect men around the world, behind lung cancer alone. Trace elements are very important and are involved in many cellular processes. The X-ray microfluorescence technique is an advanced tool of high spatial resolution, sensitivity, multielemental analysis, and nondestructiveness for trace element study. This study aimed to investigate the elemental distribution in spheroids obtained through the following human prostate cell lines using synchrotron X-ray microfluorescence: tumor cell line androgen independent (DU145), tumor cell line androgen dependent (LNCaP), and normal cell line (RWPE-1). The measurements were performed with a standard geometry of 45° of incidence, excited by a white beam using a pixel of 25 μm and an acquisition time of 300 ms/pixel at the X-ray fluorescence beamline at the Synchrotron Light National Laboratory (Campinas, Brazil). The synchrotron X-ray microfluorescence results showed differences between groups in all elements analyzed and suggested that further studies should be performed to understand the relationship of these trace elements with the progression and development of the disease. 相似文献
93.
94.
95.
Ivanov K. A. Gubaidullin A. R. Morozov K. M. Sasin M. E. Kaliteevskii M. A. 《Optics and Spectroscopy》2019,126(6):787-787
Optics and Spectroscopy - 10.1134/S0030400X17050095 相似文献
96.
97.
98.
99.
100.
Brian R. Holder Colleen A. McNaney David Luchetti Eric Schaeffer Dieter M. Drexler 《Biomedical chromatography : BMC》2015,29(9):1375-1379
Acetyl‐l ‐carnitine (ALCAR) is a potential biomarker for the modulation of brain neurotransmitter activity, but is also present in cerebrospinal fluid (CSF). Recent studies have utilized hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC‐MS/MS) based assays to detect and quantify ALCAR within biofluids such as urine, plasma and serum, using various sample pretreatment procedures. In order to address the need to quantify ALCAR in CSF on a high‐throughput scale, a new and simple HILIC‐MS/MS assay has been successfully developed and validated. For rapid analysis, CSF sample pretreatment was performed via ‘dilute and shoot’ directly onto an advanced HILIC column prior to MS/MS detection. This newly developed HILIC‐MS/MS assay shows good recoveries of ALCAR without the need for chemical derivatization and multistep sample extraction procedures. The employment of this assay is suitable for the high‐throughput bioanalysis and quantification of ALCAR within the CSF of various animal models and human clinical studies. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献