全文获取类型
收费全文 | 22957篇 |
免费 | 3335篇 |
国内免费 | 2451篇 |
专业分类
化学 | 16147篇 |
晶体学 | 276篇 |
力学 | 1353篇 |
综合类 | 187篇 |
数学 | 2297篇 |
物理学 | 8483篇 |
出版年
2024年 | 67篇 |
2023年 | 425篇 |
2022年 | 741篇 |
2021年 | 846篇 |
2020年 | 851篇 |
2019年 | 835篇 |
2018年 | 712篇 |
2017年 | 737篇 |
2016年 | 1016篇 |
2015年 | 1038篇 |
2014年 | 1175篇 |
2013年 | 1610篇 |
2012年 | 1869篇 |
2011年 | 1990篇 |
2010年 | 1297篇 |
2009年 | 1267篇 |
2008年 | 1466篇 |
2007年 | 1351篇 |
2006年 | 1222篇 |
2005年 | 973篇 |
2004年 | 778篇 |
2003年 | 660篇 |
2002年 | 632篇 |
2001年 | 461篇 |
2000年 | 455篇 |
1999年 | 482篇 |
1998年 | 422篇 |
1997年 | 423篇 |
1996年 | 463篇 |
1995年 | 365篇 |
1994年 | 381篇 |
1993年 | 272篇 |
1992年 | 254篇 |
1991年 | 233篇 |
1990年 | 167篇 |
1989年 | 129篇 |
1988年 | 117篇 |
1987年 | 97篇 |
1986年 | 95篇 |
1985年 | 85篇 |
1984年 | 58篇 |
1983年 | 49篇 |
1982年 | 38篇 |
1981年 | 28篇 |
1980年 | 31篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
用比较力场分析研究了N-亚硝基化合物的结构与致癌活性的关系,考察了网络结构和探针原子对结果的影响.结果表明,立体效应和静电作用场是描述其致癌活性和进行结构性能关系研究的最重要的结构参数。 相似文献
132.
Simple and sensitive electrochemical method for the determination of metronidazole, based on a nanostructured film coated glassy carbon electrode (GCE), is described. Multi-walled carbon nanotubes (MWNT) was dispersed into water in the presence of a hydrophobic surfactant to give very stable and homogeneous MWNT suspension, and a MWNT-film coated GCE was achieved via evaporating solvent. Metronidazole yields a well-defined reduction peak whose potential is −0.71 V at the MWNT-film coated GCE in pH 9.0 Britton-Robinson buffer. Compared with bare GCE, the MWNT-film modified GCE significantly enhances the reduction peak current of metronidazole. All the experimental parameters were optimized for the determination of metronidazole. The detection limit is 6×10−9 mol/l at 2 min accumulation. This method has been successfully used to determine metronidazole in the drugs. Furthermore, results obtained by the proposed method have been compared with spectrophotometric method. 相似文献
133.
134.
135.
TheA
1
–X
1
+ system of SnO is studied by laser- induced fluorescence excitation spectroscopy using isotopically enriched tin Sn116. The rotational structure analysis has been carried out for 6-0, 5-0, 2-0 bands. All these spectra were well resolved only with few perturbed lines in 2-0 band. Rotational constantsB
2,B
5,B
6 and henceB
e
,
e
e
have been obtained for the Sn116O molecule. An extension of perturbation study on 4-0 band has been made showing the maximum perturbation occurs at different J values for different isotopes. 相似文献
136.
Two-dimensional protein database of human pancreas 总被引:7,自引:0,他引:7
We report here the two-dimensional protein database of human pancreas. The proteins were analyzed by two-dimensional electrophoresis followed by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). Totally, 302 proteins were identified, of which about 27% were enzymes with a broad range of catalytic activities. Several of these are specifically expressed in pancreas, such as pancreatic amylase, pancreatic stone protein, pancreatitis-associated protein, pancreatic lipase, pancreatic elastase, etc. Structural and cytoskeletal proteins are also strongly represented on the gels. Thus, the pancreatic proteome reflects the organ's function. This work paves the way for further studies on pancreatic protein expression in health and disease, such as diabetes and pancreatic cancer. 相似文献
137.
138.
在所有电极过程中研究最多的是析氢反应,其重要性一直为化学界所关注。提高电极活性的各种方法中,普遍采用电沉积法,它价廉简便、效果明显。但涂层不够牢固,在使用过程中易脱落,使用寿命短。为了克服上述缺点,作者将电沉积和离子注入技术联合使用,即在Ni、W镀层上注入Mo离子,利用Mo离子的能量将Ni、W打入表面内层,进行离子束混合。这既 相似文献
139.
140.
There are many organic pollutants in the environment, such as polychlorinated biphenyl, polycyclic aromatic hydrocarbons, dichlorodiphenyl-trichloroethane (DDT), and polychlorinated naphthalene. These organic pollutants are persistent,liposoluble and easily cumulated in organism; consequently, the potential toxicity will be high. Risk assessment of industrial chemicals is currently carried out using scanty experimental data, because many of these chemicals have very little or no test data. S… 相似文献