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   1210篇
  免费   31篇
  国内免费   5篇
化学   859篇
晶体学   18篇
力学   21篇
数学   50篇
物理学   298篇
  2022年   6篇
  2021年   8篇
  2020年   10篇
  2019年   9篇
  2018年   14篇
  2017年   10篇
  2016年   25篇
  2015年   18篇
  2014年   20篇
  2013年   40篇
  2012年   57篇
  2011年   69篇
  2010年   40篇
  2009年   41篇
  2008年   74篇
  2007年   54篇
  2006年   68篇
  2005年   66篇
  2004年   61篇
  2003年   56篇
  2002年   60篇
  2001年   21篇
  2000年   29篇
  1999年   15篇
  1998年   9篇
  1997年   11篇
  1996年   15篇
  1995年   11篇
  1994年   15篇
  1993年   12篇
  1992年   19篇
  1991年   11篇
  1990年   19篇
  1989年   11篇
  1988年   9篇
  1987年   15篇
  1986年   15篇
  1985年   20篇
  1984年   22篇
  1983年   15篇
  1982年   13篇
  1981年   13篇
  1980年   12篇
  1979年   11篇
  1978年   17篇
  1977年   9篇
  1976年   13篇
  1975年   7篇
  1974年   16篇
  1973年   7篇
排序方式: 共有1246条查询结果,搜索用时 15 毫秒
51.
Optical Review - To quantify the changes in optical properties of in vivo rat liver tissue, we applied diffuse reflectance spectroscopy (DRS) system using single-reflectance fiber probe during...  相似文献   
52.
Optical Review - A precise and fast method for controlling the reference-beam angle of an angular-multiplexed holographic data storage system (HDSS)—to achieve larger capacity and faster...  相似文献   
53.
Optical Review - To evaluate multi-spectral images of the absorption and scattering properties in the cerebral cortex of rat brain, we investigated spectral reflectance images estimated by the...  相似文献   
54.
55.
UDP‐glucose:glycoprotein glucosyltransferase (UGGT) plays a key role in recognizing folded and misfolded glycoproteins in the glycoprotein quality control system of the endoplasmic reticulum. UGGT detects misfolded glycoproteins and re‐glucosylates them as a tag for misfolded glycoproteins. A flexible model to reproduce in vitro folding of a glycoprotein in the presence of UGGT in a mixture containing correctly folded, folding intermediates, and misfolded glycoproteins is described. The data demonstrates that UGGT can re‐glucosylate all intermediates in the in vitro folding experiments, thus indicating that UGGT inspects not only final folded products, but also the glycoprotein folding intermediates.  相似文献   
56.
1,1-Dimethyldibenzo[bc,fg][1,4]silathiapentalene ( 1a ) was prepared by treatment of 1,9-bis(methyl-sulfinyl)dibenzothiophene with EtMgBr or of dibenzothiophene with n-butyllithium, and then with dimethyl dichlorosilane. The structure of 4,4-dimethyl-dibenzo[bc,fg][1,4]silathiapentalene 1-oxide ( 2 ), obtained by oxidation of compound 1a with mCPBA, was determined by X-ray crystallographic analysis. The structure of compound 2 determined experimentally was compared to the structure obtained by semiempirical molecular orbital calculations (AM1). The MO calculations of compound 1a and its phenyl analog 1b were also performed by AM1 to evaluate their structures. © 1996 John Wiley & Sons, Inc.  相似文献   
57.
Wide distribution of relaxation times is taken into consideration in determination of the activation energy of the molecular motion associated with the motional narrowings of line widths of magnetic resonance spectra. The molecular motion of rotational vibration around the chain axis of polyethylene in urea-polyethylene inclusion complex is examined. Relaxation spectra can be obtained from the data of the motional narrowings of EPR and NMR by assuming the activation energy as a parameter. Also, the representative relaxation times corresponding to EPR and NMR observations can be estimated. These relaxation times give us an activation energy since EPR and NMR observations correspond to different time constants of observations. The activation energy estimated from the data of the representative correlation times is identical with the activation energy obtained as a parameter in determination of the identical relaxation spectrum from the data of motional narrowings of EPR and NMR observations.  相似文献   
58.
Anemia is a major complication of chronic renal failure. To treat this anemia, prolylhydroxylase domain enzyme (PHD) inhibitors as well as erythropoiesis-stimulating agents (ESAs) have been used. Although PHD inhibitors rapidly stimulate erythropoietin (Epo) production, the precise sites of Epo production following the administration of these drugs have not been identified. We developed a novel method for the detection of the Epo protein that employs deglycosylation-coupled Western blotting. With protein deglycosylation, tissue Epo contents can be quantified over an extremely wide range. Using this method, we examined the effects of the PHD inhibitor, Roxadustat (ROX), and severe hypoxia on Epo production in various tissues in rats. We observed that ROX increased Epo mRNA expression in both the kidneys and liver. However, Epo protein was detected in the kidneys but not in the liver. Epo protein was also detected in the salivary glands, spleen, epididymis and ovaries. However, both PHD inhibitors (ROX) and severe hypoxia increased the Epo protein abundance only in the kidneys. These data show that, while Epo is produced in many tissues, PHD inhibitors as well as severe hypoxia regulate Epo production only in the kidneys.  相似文献   
59.
This review article underlines the importance of gas chromatography (GC), high-performance liquid chromatography (HPLC) and their hyphenated techniques using mass spectrometry (MS) for the determination of natural steroids, especially in human biological fluids. Steroids are divided into eight categories based on their structures and functions, and recent references using the above methodologies for the analysis of these steroids are cited. GC and GC-MS are commonly used for the determination of volatile steroids. Although HPLC is a widely used analytical method for the determination of steroids including the conjugated type in biological fluids, LC-MS is considered to be the most promising one for this purpose because of its sensitivity, specificity and versatility.  相似文献   
60.
Herein we report a Ni-catalyzed formal hydroboration of olefins, which afforded anti-Markovnikov-type alkylboranes with B2pin2 and a stoichiometric amount of water. Formal hydrosilylation using air- and moisture-sensitive silylboranes also proceeded under optimized conditions. The reaction with trans-stilbene and D2O resulted in 1,2-H migration, which suggested that the reaction proceeded via β-hydride elimination and reinsertion mechanisms.  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