首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   196131篇
  免费   20981篇
  国内免费   11850篇
化学   133299篇
晶体学   2214篇
力学   10561篇
综合类   824篇
数学   22022篇
物理学   60042篇
  2023年   1969篇
  2022年   3787篇
  2021年   4426篇
  2020年   5465篇
  2019年   6666篇
  2018年   5654篇
  2017年   5192篇
  2016年   8949篇
  2015年   8083篇
  2014年   9644篇
  2013年   12843篇
  2012年   13000篇
  2011年   12791篇
  2010年   10449篇
  2009年   10425篇
  2008年   10429篇
  2007年   9166篇
  2006年   8407篇
  2005年   7632篇
  2004年   6533篇
  2003年   5633篇
  2002年   6231篇
  2001年   5211篇
  2000年   4515篇
  1999年   3423篇
  1998年   2863篇
  1997年   2513篇
  1996年   2506篇
  1995年   2137篇
  1994年   2163篇
  1993年   1965篇
  1992年   1823篇
  1991年   1779篇
  1990年   1661篇
  1989年   1535篇
  1988年   1285篇
  1987年   1279篇
  1986年   1196篇
  1985年   1243篇
  1984年   1140篇
  1983年   1023篇
  1982年   958篇
  1981年   833篇
  1979年   862篇
  1978年   876篇
  1977年   873篇
  1976年   989篇
  1975年   886篇
  1974年   902篇
  1973年   912篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991.  相似文献   
92.
93.
5‐Amino‐4‐methyl‐2‐phenyl‐6‐substitutedfuro[2,3‐d]pyrimidines ( 2a‐c ) were reacted with 2,5‐dimethoxytetrahydrfuran to afford the pyrrolyl derivatives 3a‐c . Compound 3a was chosen as intermediate for the synthesis of poly fused heterocycles incorporated furopyrimidines moiety 4–11 . Some of the synthesized compounds were screened for their antibacterial and antifungal activities.  相似文献   
94.
An amphiphilic poly(ethylene oxide)‐block‐poly(dimethylsiloxane) (PEO–PDMS) diblock copolymer was used to template a bisphenol A type epoxy resin (ER); nanostructured thermoset blends of ER and PEO–PDMS were prepared with 4,4′‐methylenedianiline (MDA) as the curing agent. The phase behavior, crystallization, hydrogen‐bonding interactions, and nanoscale structures were investigated with differential scanning calorimetry, Fourier transform infrared spectroscopy, transmission electron microscopy, and small‐angle X‐ray scattering. The uncured ER was miscible with the poly(ethylene oxide) block of PEO–PDMS, and the uncured blends were not macroscopically phase‐separated. Macroscopic phase separation took place in the MDA‐cured ER/PEO–PDMS blends containing 60–80 wt % PEO–PDMS diblock copolymer. However, the composition‐dependent nanostructures were formed in the cured blends with 10–50 wt % PEO–PDMS, which did not show macroscopic phase separation. The poly(dimethylsiloxane) microdomains with sizes of 10–20 nm were dispersed in a continuous ER‐rich phase; the average distance between the neighboring microdomains was in the range of 20–50 nm. The miscibility between the cured ER and the poly(ethylene oxide) block of PEO–PDMS was ascribed to the favorable hydrogen‐bonding interaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3042–3052, 2006  相似文献   
95.
The excitation of eigen surface waves by tubular electron beams in cylindrical discharge devices is studied. The influence of the wave‐field azimuthal structure on the excitation efficiency and nonlinear stage of the plasmabeam instability is investigated both numerically and analytically. Analytical expressions for the saturation amplitude and excitation efficiency of the wave under study are derived. They are found to agree well with results obtained by numerical modelling of the plasma‐beam interaction presented in this paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
96.
97.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991.  相似文献   
98.
Translated from Chislennye Metody Resheniya Obratnykh Zadach Matematicheskoi Fiziki, pp. 119–127.  相似文献   
99.
成功地在六路高功率Nd玻璃激光装置上建立了2660紫外激光探针和适合紫外波段的Normaski干涉仪,首次将可见波长的连续激光应用于紫外干涉仪中靶成像调整和光路准直。利用该紫外光干涉仪,在铜柱状靶(φ500μm)上测量了厚等离子体中高达0.6n。的电子密度。  相似文献   
100.
Yu V Sharvin 《Pramana》1987,28(5):592-592
Investigation of the galvanomagnetic properties of disordered metals in weak magnetic fields [r(H)?l, wherer(H) is the electron trajectory radius andl, the electron free path], proved to be one of the effective experimental methods of studying disordered metals. The phase difference between the interfering electron waves is affected by the presence of magnetic flux in the sample. One of the observable effects is the oscillatory magnetoresistanceK(H) of multiconnected samples predicted by Altshuleret al (1981). The period ofK(H) oscillations for the hollow cylinders, networks or chains with orifices cross-sections areasS isΔH=φ 0/2S [whereφ 0=hc/e]. The amplitude and the phase of the oscillations depend on the spin orbit interaction, the intensity of superconductive fluctuation etc. It should be noted that in small “mesoscopic” single loops the oscillations with the periodΔH?φ 0/S were also observed recently (see also Altshuleret al 1987 included in this issue).  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号