全文获取类型
收费全文 | 880篇 |
免费 | 9篇 |
国内免费 | 2篇 |
专业分类
化学 | 565篇 |
晶体学 | 6篇 |
力学 | 25篇 |
数学 | 61篇 |
物理学 | 234篇 |
出版年
2021年 | 9篇 |
2020年 | 6篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2013年 | 38篇 |
2012年 | 28篇 |
2011年 | 35篇 |
2010年 | 17篇 |
2009年 | 12篇 |
2008年 | 29篇 |
2007年 | 26篇 |
2006年 | 22篇 |
2005年 | 25篇 |
2004年 | 26篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1996年 | 7篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 19篇 |
1992年 | 27篇 |
1991年 | 13篇 |
1990年 | 19篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 11篇 |
1974年 | 19篇 |
1973年 | 13篇 |
1972年 | 6篇 |
1913年 | 6篇 |
1911年 | 7篇 |
1906年 | 7篇 |
1899年 | 10篇 |
1898年 | 6篇 |
1894年 | 5篇 |
排序方式: 共有891条查询结果,搜索用时 46 毫秒
31.
32.
33.
34.
35.
36.
37.
LoSecco JM Bionta RM Biewitt G Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(21):2299-2301
38.
The reaction of hexakis(cyclohexylamino) cyclotriphosphazene [NP(CyNH)(2)](3), 1, with phosphorus trichloride yields [NP(CyN)(2)PCl](3), 2, which contains three four-membered phosphazane rings fused in spirocyclic fashion to a central six-membered phosphazene ring and constitutes the first structurally characterized compound that comprises both phosphazene and phosphazane rings. The peripheral P atoms feature stereoactive lone pairs, and, thus, 2 exists in isomeric C(3h) and C(s) forms. The spirocyclic phosphazene-phosphazane derivative 2 carries three reactive PCl functions in peripheral positions, promising an interesting precursor molecule for the synthesis of extended phosphorus nitrogen structures of high rigidity. Extension of the PN moiety can be achieved by reaction of 2 with a primary amine yielding [NP(CyN)(2)PN(H)(t)Bu](3), 3, which features a central scaffold of 6 phosphorus and 12 nitrogen centers and aggregates via N-H...P hydrogen bonds in the solid state. On the contrary, the reaction of 1 with SbCl(3) undergoes incomplete proton abstraction, resulting in the formation of the tricyclic compound N(3)P(3)(CyNH)(4)(CyNSbCl(2))(2), 4, which contains two four-coordinate Sb centers chelated by N(exo)-N(ring) sites of the phosphazene. 相似文献
39.
Enzyme--substrate interaction by nuclear magnetic resonance 总被引:2,自引:0,他引:2
40.
Santini Jr Richards AC Scheidt R Cima MJ Langer R 《Angewandte Chemie (International ed. in English)》2000,39(14):2396-2407
Controlled-release systems are common in a number of product areas, including foods, cosmetics, pesticides, and paper. Microencapsulated systems, for example, are used for the release of flavors and vitamins in foods, fragrances in perfumes, and inks in carbonless copy paper. Controlled-release systems for drug delivery first appeared in the 1960s and 1970s. In the past three decades, the number and variety of controlled release systems for drug-delivery applications has increased dramatically. Many of these use polymers having particular physical or chemical characteristics such as biodegradability, biocompatibility, or responsiveness to pH or temperature changes. However, recent advances in the field of microfabrication have created the possibility of a new class of controlled-release systems for drug delivery, namely, that of small, programmable devices. Their small size, potential for integration with microelectronics, and ability to store and release chemicals on demand could make controlled-release microchips useful in a number of areas, including medical diagnostics, analytical chemistry, chemical detection, industrial process monitoring and control, combinatorial chemistry, microbiology, and fragrance delivery. More importantly, drug-delivery microchips resulting from this convergence of controlled release and microfabrication technologies may provide new treatment options to clinicians in their fight against disease. 相似文献