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   1439篇
  免费   56篇
  国内免费   6篇
化学   1139篇
晶体学   12篇
力学   19篇
数学   71篇
物理学   260篇
  2023年   7篇
  2021年   18篇
  2020年   20篇
  2019年   22篇
  2018年   17篇
  2017年   16篇
  2016年   29篇
  2015年   33篇
  2014年   39篇
  2013年   69篇
  2012年   78篇
  2011年   94篇
  2010年   48篇
  2009年   54篇
  2008年   87篇
  2007年   101篇
  2006年   95篇
  2005年   79篇
  2004年   72篇
  2003年   75篇
  2002年   55篇
  2001年   24篇
  2000年   19篇
  1999年   14篇
  1998年   13篇
  1997年   12篇
  1996年   18篇
  1995年   16篇
  1994年   12篇
  1993年   13篇
  1992年   6篇
  1991年   11篇
  1990年   7篇
  1989年   5篇
  1988年   6篇
  1987年   8篇
  1986年   13篇
  1985年   20篇
  1984年   12篇
  1983年   10篇
  1982年   14篇
  1981年   21篇
  1980年   26篇
  1979年   16篇
  1978年   10篇
  1977年   10篇
  1976年   9篇
  1975年   7篇
  1974年   11篇
  1973年   12篇
排序方式: 共有1501条查询结果,搜索用时 330 毫秒
1.
A. Beurling introduced harmonic functions attached to measurable functions satisfying suitable conditions and defined their spectral sets. The concept of spectral sets is closely related to approximations by trigonometric polynomials. In this paper we consider spectral sets of the harmonic functions attached to the Riemann zeta-function and its modification.  相似文献   
2.
Crosslinked poly(N-isopropylacrylamide) gel was tested on the feasibility for a preparative electrophoretic matrix. Horse heart myoglobin and bovine hemoglobin were well separated on the gel matrix electrophoretically by molecular sieving effect of the gel network. Relative mobilities of those proteins in the gel were larger than those in a crosslinked polyacrylamide gel of the same polymer concentration. After the separation, the protein-containing portion of the gel underwent swelling at 4°C and deswelling at 37°C, alternatively. As a result of the deswelling, each protein was recovered in a discharged solution out of the gel at almost 100% yield.  相似文献   
3.
4.
In this study, we attempted to control the timing of light-emission from bioluminescent bacteria, by changed cell numbers inoculated into medium. Luminous bacteria express bioluminescence when the number of cells reached a threshold. Inoculated cell density had an effect on the time of bioluminescence starting. Samples were prepared by varying cell density of inoculation. In the results, all the vials showed different luminescence profiles in the order of inoculated cell population.  相似文献   
5.
Experimental observations for possible presence of 4f quadrupolar Kondo effect in PrCu2Si2 are critically discussed. A comparison of the low temperature properties of the alloys, Pr x Y1–x Cu2Si2 (x=0.05, 0.2 and 0.4), seems to signal the existence of 4f electric quadrupolar glass phenomenon around 4K forx=0.2.  相似文献   
6.
7.
The regional cerebral blood flow (CBF) was determined on seventeen patients with brain tumors. Ring type single photon emission CT (SPECT) was used following intravenous injection of 133Xe. Case materials included eleven meningiomas and six malignant gliomas. Evaluation was performed with emphasis on the following points; Correlation of the flow data within tumors to the angiographic tumor stains, Influence of tumors on the cerebral blood flow of the normal brain tissue, Correlation between degree of peripheral edema and the flow data of the affected hemispheres. There was significant correlation between flow data within tumors and angiographic tumor stains in meningiomas. Influence of tumors on cerebral blood flow of the normal tissue was greater in meningiomas than in gliomas. There was negative correlation between the degree of peripheral edema and the flow data of the affected hemisphere. It has been concluded that the measurement of CBF in brain tumors is a valuable method in evaluation of brain tumors.  相似文献   
8.
9.
A poly(N-isopropylacrylamide) (PNIPAAm)-like biodegradable thermosensitive polydepsipeptide, poly[Glc-Asn(N-isopropyl)], was synthesized by introducing an isopropyl amide group into poly[Glc-Asn]. Poly[Glc-Asn(N-isopropyl)] was degraded in vitro by cleavage of the ester bonds in the main chain in water at room temperature. The non-toxic nature of the polymer and its degradation products, coupled with a cloud point at 29 degrees C in water, make this polymer attractive for biomedical implant applications.  相似文献   
10.
In order to clarify the mechanism of action for the antioxidative activity of fluvastatin sodium (FLV, (+/-)-sodium (3RS, 5RS, 6E)-7-[3-(4-fluorophenyl)-1-(1-methylethyl)-1H-indol-2-yl]-3, 5-dihydroxy-6-heptanoate) and its derivatives, reaction of the corresponding methyl ester of FLV with di-tert-butyl diperoxyoxalate was examined, and the corresponding keto derivative was isolated from the reaction mixture. On the basis of this result, it was concluded that the active site is the allylic carbon conjugated with the indole ring.  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