全文获取类型
收费全文 | 113244篇 |
免费 | 19107篇 |
国内免费 | 10973篇 |
专业分类
化学 | 76928篇 |
晶体学 | 1308篇 |
力学 | 7310篇 |
综合类 | 635篇 |
数学 | 13033篇 |
物理学 | 44110篇 |
出版年
2024年 | 383篇 |
2023年 | 2241篇 |
2022年 | 3852篇 |
2021年 | 4169篇 |
2020年 | 4504篇 |
2019年 | 4379篇 |
2018年 | 3763篇 |
2017年 | 3519篇 |
2016年 | 5533篇 |
2015年 | 5278篇 |
2014年 | 6445篇 |
2013年 | 8364篇 |
2012年 | 10158篇 |
2011年 | 10464篇 |
2010年 | 6943篇 |
2009年 | 6604篇 |
2008年 | 7031篇 |
2007年 | 6434篇 |
2006年 | 5848篇 |
2005年 | 4915篇 |
2004年 | 3709篇 |
2003年 | 2949篇 |
2002年 | 2717篇 |
2001年 | 2231篇 |
2000年 | 1919篇 |
1999年 | 2264篇 |
1998年 | 1969篇 |
1997年 | 1804篇 |
1996年 | 1994篇 |
1995年 | 1584篇 |
1994年 | 1540篇 |
1993年 | 1245篇 |
1992年 | 1134篇 |
1991年 | 1048篇 |
1990年 | 831篇 |
1989年 | 610篇 |
1988年 | 493篇 |
1987年 | 409篇 |
1986年 | 402篇 |
1985年 | 348篇 |
1984年 | 252篇 |
1983年 | 159篇 |
1982年 | 150篇 |
1981年 | 113篇 |
1980年 | 83篇 |
1979年 | 49篇 |
1978年 | 39篇 |
1976年 | 40篇 |
1974年 | 47篇 |
1957年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Feng Liu Si Guo Yuan Xiao Li Wang A.E Polikarpov A.A. Shunkevich 《中国化学快报》2007,18(5):588-590
A fibrous sorbent possessing abundant micropore structure was firstly prepared via post-crosslinking reaction on the PP-ST-DVB original fiber. Its micromorphology and sorptive properties were investigated, and the results demonstrated that the novel fibrous hypererosslinked sorbent has narrow pore-size distribution, small average porous radius (1.90 nm), high specific surface area (362.31 m^2/g), and fine sorptive properties for small organic molecules. 相似文献
992.
993.
Katritzky AR Wang Z Hall CD Akhmedov NG Shestopalov AA Steel PJ 《The Journal of organic chemistry》2003,68(23):9093-9099
Reactions of oximes 9, 17, and 19 with electrophiles 15a-f and 24 in the presence of anhydrous potassium carbonate or triethylamine give 2-substituted condensed ring oxazoles 10, 16a-c, 18a-d, 20a-c, and 25 in a new general route to these compounds. 相似文献
994.
[reaction: see text] A 30-member library of small molecules based on the vinyl sulfone scaffold was prepared on rink amide resin, using solid phase-based reactions such as oxidation and Horner-Wadsworth-Emmons reaction. The library was designed such that three points of diversity were readily introduced in the library to accommodate the S(1)', S(1), and S(2) binding pockets of different cysteine proteases, making the strategy suitable for high-throughput generation of potential cysteine protease inhibitors. 相似文献
995.
An enantioselective total synthesis of hamacanthin B (1) is described. This synthesis is based on the asymmetric synthesis of (S)-2-azido-(indol-3-yl)ethylamine 7, which is coupled with the 3-indolyl-alpha-oxoacetyl chloride 8 and subsequently used in a successful intramolecular Staudinger-aza Wittig cyclization to form the central dihydropyrazinone ring. The stereochemistry of naturally isolated hamacanthin B is revealed as the (S)-configuration. 相似文献
996.
C.L. Liu X.Y. Wang Z.M. Wang S.S. Li C.T. Xin H.F. Wang B. Li L. Jiang 《Journal of Radioanalytical and Nuclear Chemistry》2001,250(3):587-591
The migration of 99Tc in a weak loess aquifer was investigated in-situ with undisturbed aquifer medium columns. The columns were obtained horizontally at a depth of 3236 m in an Underground Research Facility (URF). Quartz containing 3H (HTO) and 99Tc (in the form of 99TcO4
-) was introduced into one end of the columns and the columns were covered tightly. Aquifer water was introduced into the columns directly from an experimental shaft in the UFR. Effluents from the columns were collected and the activity of 3H and 99Tc were determined with a liquid scintillation analyzer. The breakthrough curves of 3H and 99Tc indicate that 99Tc migrates a little faster than that 3H does in the aquifer. 相似文献
997.
Accumulation of five heavy metal ions by five species of wood-rotting basidiomycetes during a 9-day cultivation was studied. Contents of Cd, Cu, Pb, and Zn were measured using ICP-MS; the amount of mercury was determined directly in solid samples using the Advanced Mercury Analyser. A standard operation procedure for the sample preparation and determination of metal content was developed and validated. Presence of Cd, Cu, Hg, and Pb decreased the accumulation of zinc by the fungi. The basidiomycete Pycnoporus cinnabarinus exhibited the highest metal binding capacity of all fungi tested. 相似文献
998.
采用UVVis光谱法研究了茜素红S(ARS)与5′鸟苷酸(5′GMP)在pH4.80的弱酸性缓冲溶液中生成络合物的结合反应。与试剂比较,络合物的最大吸收峰红移92nm,测得络合物和表观摩尔吸光系数为ε=1.3×104L·mol-1·cm-1;最大结合数n=10;浓度线性范围0.2~16mg/L;检出限为6.1×10-8mol/L。研究了ARS与5′GMP是分子间作用力的结合反应,并对时间、温度、离子强度对结合反应的影响,以及无机物、生物物质对反应体系的干扰情况进行了初步研究。 相似文献
999.
A new high-performance liquid chromatographic (HPLC) method for measuring low molecular weight (LMW) thiol-containing compounds, including cysteine (CysH), glutathione (GSH), N-acetylcysteine (Nac), penicillamine (PA), and 2-mercaptoethanol (2-ME), has been developed by using 5-methyl-(2-(m-iodoacetylaminophenyl)benzoxazole (MIPBO) as fluorescence-labeling reagent. The derivatization and separation conditions have been investigated in detail. Detection limits ranging from 3.5 to 15.0 fmol were achieved for the thiols investigated in a 16 min separation with detection wavelengths 310 and 375 nm for the excitation and emission, respectively. The utility of the proposed method has been validated by measuring CysH in human urine samples. 相似文献
1000.
Poly(malachite green) film modified Nafion‐coated glassy carbon electrodes have been prepared by potentiodynamic cycling in malachite green solution. The pH of polymerisation solution has only minor effect on film formation. Electrochemical quartz crystal microbalance (EQCM) was used to monitor the growth of the poly(malachite green) film. Cyclic voltammogram of the poly(malachite green) film shows a redox couple with well‐defined peaks. The redox response of the modified electrode was found to be depending on the pH of the contacting solution. The peak potentials were shifted to a less positive region with increasing pH and the dependence of the peak potential was found to be 56 mV per pH unit. The electrocatalytic behavior of poly(malachite green) film modified Nafion‐coated glassy carbon electrodes was tested towards oxidation of NADH, dopamine, and ascorbic acid. The oxidation of dopamine and ascorbic acid occurred at less positive potential on poly(malachite green) film compared to bare glassy carbon electrode. In the case of NADH, the overpotential was reduced substantially on modified electrode. Finally, the feasibility of utilizing poly(malachite green) film electrode in analytical estimation of ascorbic acid was demonstrated in flow injection analysis. 相似文献