全文获取类型
收费全文 | 563篇 |
免费 | 21篇 |
国内免费 | 2篇 |
专业分类
化学 | 364篇 |
晶体学 | 8篇 |
力学 | 9篇 |
数学 | 75篇 |
物理学 | 130篇 |
出版年
2023年 | 3篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 25篇 |
2012年 | 26篇 |
2011年 | 38篇 |
2010年 | 23篇 |
2009年 | 24篇 |
2008年 | 31篇 |
2007年 | 30篇 |
2006年 | 38篇 |
2005年 | 27篇 |
2004年 | 34篇 |
2003年 | 15篇 |
2002年 | 21篇 |
2001年 | 16篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 11篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1963年 | 1篇 |
排序方式: 共有586条查询结果,搜索用时 937 毫秒
151.
Kawaguchi M Ito R Endo N Okanouchi N Sakui N Saito K Nakazawa H 《Journal of chromatography. A》2006,1110(1-2):1-5
A new method that involves liquid phase microextraction (LPME) with in situ derivatization and gas chromatography-mass spectrometry (GC-MS) is described for the determination of trace amounts of bisphenol A (BPA) in river water samples. The LPME conditions, such as the type of extraction solvent and the extraction time, are investigated. Then, the extract is directly injected into GC-MS. The detection limit and the quantification limit of BPA in river water sample are 2 and 10pgml(-1) (ppt), respectively. The calibration curve for BPA is linear with a correlation coefficient of >0.999 in the range of 10-10,000pgml(-1). The average recoveries of BPA in river water samples spiked with 100 and 1000pgml(-1) BPA are 104.1 (RSD: 8.9%) and 98.3 (RSD: 3.2%), respectively, with correction using the added surrogate standard, bisphenol A-(13)C(12). This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of BPA in liquid samples. 相似文献
152.
The interaction forces between poly(N-isopropylacrylamide) (PNIPAAm)-grafted surfaces and colloidal particles in an aqueous solution were investigated using an atomic force microscope. Measurements were conducted between smooth silicon wafers on which PNIPAAm was terminally grafted and silica particles hydrophobized with a silanating reagent in an aqueous electrolyte solution under controlled temperature. Below the lower critical solution temperature (LCST) of PNIPAAm, there were large repulsive forces between the surfaces, both on approach and separation of the surfaces. On the other hand, above LCST, attractive forces were observed both in approaching and in separating force curves. When surface hydrophobicity of the particles increased, the maximum attractive force tended to increase. The changes of hydration state of the grafted PNIPAAm chains depending on temperature are considered to greatly alter the interaction force properties. The role of the intermolecular interaction between the PNIPAAm chains and the hydrophobic particles in the interaction forces is discussed. 相似文献
153.
Let G be a graph and f be a mapping from V(G) to the positive integers. A subgraph T of G is called an f‐tree if T forms a tree and dT(x)≤f(x) for any x∈V(T). We propose a conjecture on the existence of a spanning f‐tree, and give a partial solution to it. © 2009 Wiley Periodicals, Inc. J Graph Theory 65: 173–184, 2010 相似文献
154.
Kamino S Horio Y Komeda S Minoura K Ichikawa H Horigome J Tatsumi A Kaji S Yamaguchi T Usami Y Hirota S Enomoto S Fujita Y 《Chemical communications (Cambridge, England)》2010,46(47):9013-9015
A new class of rhodamine luminophores, 3',3'-bis(oxospiroisobenzofuran)-3,7-bis(dialkylamino)benzopyrano-xanthene derivatives (ABPX), have been successfully developed. The emission behavior of ABPX series is directly opposite to the concentration quenching of conventional rhodamine dyes. ABPX series exhibit aggregation-induced emission enhancement (AIEE). 相似文献
155.
Video-Assisted Rigid Endoscopic Laryngosurgery: Application to Cases with Difficult Laryngeal Exposure 总被引:8,自引:0,他引:8
In some cases of microlaryngosurgery, laryngeal exposure with a direct laryngoscope is difficult because of a variety of reasons. In such cases, we now use a long rigid endoscope inserted into the side tube of the direct laryngoscope together with a video system. The lesion can be removed while the phonosurgeon observes the magnified images of the larynx on the video monitor. We describe the surgical procedure together with the preoperative and postoperative evaluation of vocal function in 13 patients with benign laryngeal lesions. A good surgical and vocal outcome was achieved in all cases. The method appeared to be useful for treating dysphonia in patients in whom it was difficult to expose the larynx with a direct laryngoscope. 相似文献
156.
157.
Yoshimi Egawa Hikoe Enomoto Ralph J. Faudree Hao Li Ingo Schiermeyer 《Journal of Graph Theory》2003,43(3):188-198
It is shown that if G is a graph of order n with minimum degree δ(G), then for any set of k specified vertices {v1,v2,…,vk} ? V(G), there is a 2‐factor of G with precisely k cycles {C1,C2,…,Ck} such that vi ∈ V(Ci) for (1 ≤ i ≤ k) if or 3k + 1 ≤ n ≤ 4k, or 4k ≤ n ≤ 6k ? 3,δ(G) ≥ 3k ? 1 or n ≥ 6k ? 3, . Examples are described that indicate this result is sharp. © 2003 Wiley Periodicals, Inc. J Graph Theory 43: 188–198, 2003 相似文献
158.
Sakamoto M Iwamoto T Nono N Ando M Arai W Mino T Fujita T 《The Journal of organic chemistry》2003,68(3):942-946
Asymmetric synthesis using frozen chirality generated by spontaneous crystallization was performed. Achiral asymmetrically substituted imide with a tetrahydronaphthyl group on the nitrogen atom crystallized in a chiral fashion, with space group P2(1)2(1)2(1). The molecular chirality generated by spontaneous crystallization was retained in cold THF. The half-life determined on the basis of decreasing optical activity followed by CD spectrometer was 7.8, 33.1, and 150.0 min at -20, -30, -40 degrees C, respectively. The energy barrier (DeltaG()) of racemization was calculated with the temperature dependence of the kinetic constant to be 18.24-18.36 kcal mol(-)(1) at 233-253 K. The memorized frozen chirality was transferred to permanent optically active alcohols by nucleophilic addition with n-buthyllithium. 相似文献
159.
160.
Nomura E Katsuta K Ueda T Toriyama M Mori T Inagaki N 《Journal of mass spectrometry : JMS》2004,39(2):202-207
Mass spectrometry (MS) together with genome database searches serves as a powerful tool for the identification of proteins. In proteome analysis, mixtures of cellular proteins are usually separated by sodium dodecyl sulfate (SDS) polyacrylamide gel-based two-dimensional gel electrophoresis (2-DE) or one-dimensional gel electrophoresis (1-DE), and in-gel digested by a specific protease. In-gel protein digestion is one of the critical steps for sensitive protein identification by these procedures. Efficient protein digestion is required for obtaining peptide peaks necessary for protein identification by MS. This paper reports a remarkable improvement of protein digestion in SDS polyacrylamide gels using an acid-labile surfactant, sodium 3-[(2-methyl-2-undecyl-1,3-dioxolan-4-yl)methoxy]-1-propanesulfonate (ALS). Pretreatment of gel pieces containing protein spots separated by 2-DE with a small amount of ALS prior to trypsin digestion led to increases in the digested peptides eluted from the gels. Consistently, treatment of gel pieces containing silver-stained standard proteins and those separated from tissue extracts resulted in the detection of increased numbers of peptide peaks in spectra obtained by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOFMS). Hence the present protocol with ALS provides a useful strategy for sensitive protein identification by MS. 相似文献