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   359436篇
  免费   4546篇
  国内免费   934篇
化学   181952篇
晶体学   4869篇
力学   16195篇
综合类   7篇
数学   43989篇
物理学   117904篇
  2021年   3352篇
  2020年   3738篇
  2019年   4032篇
  2018年   5563篇
  2017年   5793篇
  2016年   8192篇
  2015年   4838篇
  2014年   7823篇
  2013年   17690篇
  2012年   13710篇
  2011年   16401篇
  2010年   11867篇
  2009年   11595篇
  2008年   14761篇
  2007年   14681篇
  2006年   13469篇
  2005年   11676篇
  2004年   10738篇
  2003年   9434篇
  2002年   9406篇
  2001年   10938篇
  2000年   8161篇
  1999年   6320篇
  1998年   5299篇
  1997年   5125篇
  1996年   4910篇
  1995年   4250篇
  1994年   4239篇
  1993年   4199篇
  1992年   4497篇
  1991年   4593篇
  1990年   4393篇
  1989年   4189篇
  1988年   3968篇
  1987年   4126篇
  1986年   3869篇
  1985年   4977篇
  1984年   5012篇
  1983年   4190篇
  1982年   4291篇
  1981年   4021篇
  1980年   3934篇
  1979年   4196篇
  1978年   4230篇
  1977年   4219篇
  1976年   4155篇
  1975年   3930篇
  1974年   3862篇
  1973年   3909篇
  1972年   2701篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Russian Journal of General Chemistry - Thermogravimetry, differential scanning calorimetry, and flow methods were used to investigate thermal properties of a series of cobalt(II)...  相似文献   
142.
Russian Journal of General Chemistry - The technical legal acts that regulate the quality and safety parameters of mineral waters out were analyzed. Seven samples of mineral waters produced in...  相似文献   
143.
An innovative volatolomic approach employs the detection of biomarkers present in cerumen (earwax) to identify cattle intoxication by Stryphnodendron rotundifolium Mart., Fabaceae (popularly known as barbatimão). S. rotundifolium is a poisonous plant with the toxic compound undefined and widely distributed throughout the Brazilian territory. Cerumen samples from cattle of two local Brazilian breeds (‘Curraleiro Pé-Duro’ and ‘Pantaneiro’) were collected during an experimental intoxication protocol and analyzed using headspace (HS)/GC–MS followed by multivariate analysis (genetic algorithm for a partial least squares, cluster analysis, and classification and regression trees). A total of 106 volatile organic metabolites were identified in the cerumen samples of bovines. The intoxication by S. rotundifolium influenced the cerumen volatolomic profile of the bovines throughout the intoxication protocol. In this way, it was possible to detect biomarkers for cattle intoxication. Among the biomarkers, 2-octyldecanol and 9-tetradecen-1-ol were able to discriminate all samples between intoxicated and nonintoxicated bovines. The cattle intoxication diagnosis by S. rotundifolium was accomplished by applying the cerumen analysis using HS/GC–MS, in an easy, accurate, and noninvasive way. Thus, the proposed bioanalytical chromatography protocol is a useful tool in veterinary applications to determine this kind of intoxication.  相似文献   
144.
Research on Chemical Intermediates - A series of quinoxaline derivatives were efficiently synthesized by convenient and simple procedure in excellent yields using 1 wt.% of titanium silicate (TS-1)...  相似文献   
145.
Larotrectinib is a first-generation tropomyosin kinase inhibitor, approved for the treatment of solid tumors. In this paper, we present a validated dried blood spot (DBS) method for the quantitation of larotrectinib from mouse blood using HPLC–MS/MS, which was operated under multiple reaction monitoring mode. To the DBS disc cards, acidified methanol enriched with internal standard (IS; enasidenib) was added and extracted using tert-butyl methyl ether as an extraction solvent with sonication. Chromatographic separation of larotrectinib and the IS was achieved on an Atlantis dC18 column using 10 mm ammonium formate–acetonitrile (30:70, v/v) delivered at a flow-rate of 0.80 ml/min. Under these optimized conditions, the retention times of larotrectinib and the IS were ~0.93 and 1.37 min, respectively. The total run time was 2.50 min. Larotrectinib and the IS were analyzed using positive ion scan mode and parent–daughter mass to charge ion (m/z) transitions of 429.1 → 342.1 and 474.1 → 267.1, respectively, were used for the quantitation. The calibration range was 1.06–5,080 ng/ml. No matrix effect or carryover was observed. Hematocrit did not influence DBS larotrectinib concentrations. All of the validation parameters met the acceptance criteria. The applicability of the validated method was shown in a mouse pharmacokinetic study.  相似文献   
146.
Physics of Atomic Nuclei - Improved mechanical properties of oxide dispersion strengthened (ODS) steels, the advanced materials for the reactor core, are due to the high density of uniformly...  相似文献   
147.
148.
149.
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism.  相似文献   
150.
Sukhorukova  O. S.  Tarasenko  A. S.  Tarasenko  S. V.  Shavrov  V. G. 《JETP Letters》2020,112(7):420-427
JETP Letters - At the resonant passage of a plane elastic shear wave through an acoustically continuous heterostructure consisting of magnetic and nonmagnetic layers in a symmetric nonmagnetic...  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