全文获取类型
收费全文 | 386000篇 |
免费 | 3186篇 |
国内免费 | 981篇 |
专业分类
化学 | 206900篇 |
晶体学 | 6063篇 |
力学 | 17165篇 |
综合类 | 12篇 |
数学 | 41645篇 |
物理学 | 118382篇 |
出版年
2020年 | 3019篇 |
2019年 | 3319篇 |
2018年 | 4386篇 |
2017年 | 4410篇 |
2016年 | 6495篇 |
2015年 | 3939篇 |
2014年 | 6169篇 |
2013年 | 15727篇 |
2012年 | 11911篇 |
2011年 | 14646篇 |
2010年 | 10442篇 |
2009年 | 10292篇 |
2008年 | 13895篇 |
2007年 | 13858篇 |
2006年 | 13176篇 |
2005年 | 11916篇 |
2004年 | 10928篇 |
2003年 | 10020篇 |
2002年 | 9866篇 |
2001年 | 11781篇 |
2000年 | 8887篇 |
1999年 | 6872篇 |
1998年 | 5511篇 |
1997年 | 5600篇 |
1996年 | 5269篇 |
1995年 | 4897篇 |
1994年 | 5045篇 |
1993年 | 4577篇 |
1992年 | 5468篇 |
1991年 | 5530篇 |
1990年 | 5345篇 |
1989年 | 5182篇 |
1988年 | 5273篇 |
1987年 | 5123篇 |
1986年 | 4815篇 |
1985年 | 6320篇 |
1984年 | 6573篇 |
1983年 | 5407篇 |
1982年 | 5525篇 |
1981年 | 5335篇 |
1980年 | 5291篇 |
1979年 | 5512篇 |
1978年 | 5897篇 |
1977年 | 5791篇 |
1976年 | 5762篇 |
1975年 | 5352篇 |
1974年 | 5429篇 |
1973年 | 5573篇 |
1972年 | 3878篇 |
1971年 | 3186篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The buffer extracts (3S) of sclerotia of Sclerotinia sclerotiorum IFO 9395 contained mitogenic substance(s) to murine splenocytes (Shinohara et al. Chem. Pharm. Bull., 38, 2219 (1990)). Although the native 3S was slightly mitogenic, heating of 3S induced significant mitogenic activity. To isolate the mitogen, we separated 3S by ion-exchange and gel filtration chromatographies. The isolated mitogen, named sclerogen, has a molecular mass of 32 kilodaltons (kDa) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the isoelectric point (pI) of 5.9 by chromatofocusing. Sclerogen was significantly mitogenic in vitro against murine splenocytes after heat denaturation, and also showed the augmentation of the primary mixed lymphocyte reaction (MLR) in vitro. However, sclerogen did not show the activation of an alternative pathway of complement and hemagglutination activity. These results suggest that sclerogen is a unique mitogen which differs from lectins and shows mitogenicity after heat denaturation. 相似文献
102.
A fast-frequency modulated (FM) diode laser has been optically narrowed using the technique of resonant optical feedback, to provide linewidths in each FM mode of ≈ 200 kHz peak-to-peak. With a drive frequency of 50 MHz and modulation index of 0.2, the FM laser has been used for the first time to obtain Doppler-free FM spectra of the Rb D1 line at 795 nm. The potential use of this system for laser frequency stabilisation is discussed. 相似文献
103.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
104.
105.
106.
We study matter-wave solitons in Bose-Einstein condensates of ultracold gaseous atoms with spin degrees of freedom and present a class of exact solutions based on the inverse scattering method. The one-soliton solutions are classified with respect to the spin states. We analyze collisional effects between solitons in the same or different spin state(s), which reveals a very interesting possibility: we can manipulate the spin dynamics by controlling the parameters of colliding solitons. 相似文献
107.
The first enantiospecific synthesis of allopupukeanones has been accomplished starting from 6-methylcarvone. A biogenetically patterned rearrangement of a pupukeanane to allopupukeanane was employed as the key step. 相似文献
108.
109.
The occurrence and formation of black spots areas in PolyLED devices has been studied by time-of-flight SIMS (TOFSIMS). The composition, shape and position of the black spots is visualised by three-dimensional (3D)-TOFSIMS depth-profiling. It has been established that the formation of non-emissive spots is due to the growth of aluminium oxide clusters at the AlBa/polymer interface. Electron injection in the black spots is lost by the resulting local increase of the resistivity of the cathode. 相似文献
110.
Photoisomerization of provitamin D 3 (7-dehydrocholesterol) in a nematic liquid crystal (ZLI-1695, Merck) is investigated in detail by UV absorption spectroscopy. It is found that dissolution of chiral molecules of provitamin D 3 induces the cholesteric phase in a nematic. The spectral kinetics of photoisomerization in this phase changes significantly from that in an ethanol solution. A sharp nonmonotonic dependence of the increase in accumulation of trans isomer tachysterol in a liquid crystal matrix with a decrease in the induced cholesteric pitch from 2200 to 25 μm is revealed. 相似文献