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   3934篇
  免费   145篇
  国内免费   48篇
化学   2711篇
晶体学   31篇
力学   152篇
数学   354篇
物理学   879篇
  2023年   14篇
  2022年   36篇
  2021年   66篇
  2020年   72篇
  2019年   58篇
  2018年   46篇
  2017年   43篇
  2016年   100篇
  2015年   84篇
  2014年   140篇
  2013年   232篇
  2012年   245篇
  2011年   287篇
  2010年   180篇
  2009年   202篇
  2008年   240篇
  2007年   199篇
  2006年   191篇
  2005年   177篇
  2004年   171篇
  2003年   156篇
  2002年   164篇
  2001年   105篇
  2000年   112篇
  1999年   60篇
  1998年   55篇
  1997年   48篇
  1996年   62篇
  1995年   50篇
  1994年   45篇
  1993年   44篇
  1992年   29篇
  1991年   27篇
  1990年   24篇
  1989年   32篇
  1988年   16篇
  1987年   25篇
  1986年   26篇
  1985年   33篇
  1984年   28篇
  1983年   29篇
  1982年   19篇
  1981年   21篇
  1980年   12篇
  1979年   13篇
  1978年   12篇
  1977年   16篇
  1976年   20篇
  1975年   17篇
  1974年   10篇
排序方式: 共有4127条查询结果,搜索用时 0 毫秒
931.
Research on Chemical Intermediates - The purpose of this study was to reclaim squid pens for the production of chitosanases and biosorbents of food colorants and industrial dyes via Bacillus cereus...  相似文献   
932.
Ban E  Choi OK  Chung WY  Park CS  Yoo EA  Chung BC  Yoo YS 《Electrophoresis》2001,22(11):2173-2178
More efficient and faster separation conditions for qualitative as well as quantitative analysis of neuropeptides in human plasma using capillary zone electrophoresis (CZE) have been developed. The analysis method for neuropeptides has been improved specifically to study thyroid hormone related neuropetides for the regulation of thyroid disease. In this study, we investigated the pretreatment methods, composition of the running buffer and rinsing procedures between runs in order to obtain more sensitive and faster separation of trace neuropeptides in plasma by CZE. The tested neuropeptides were somatostatin (SOMA), vasopressin (VP), neurotensin (NT), and thyrotropin-releasing hormone (TRH). Plasma samples were pretreated by deproteinization and solid-phase extraction method. The fraction of neuropeptides was reconstituted in 40% acetonitrile followed by ultrafiltration, and then analyzed by CZE. Resolution and sensitivity was improved using the separation buffer composition with 100 mM Tris-phosphate buffer (pH 2.0) while the sensitivity was further improved via a stacking method using the sample buffer of 40% acetonitrile. These sample pretreatment methods and buffer condition permit quantitative analysis on tested neuropeptides at the 20 ng/mL level. The rinsing procedures between runs using 90% ethanol dramatically shortened the rinsing time to 30 min.  相似文献   
933.
以流动模式(flow mode)多极板之电流变阀(electrorheological valve) 进行避震器阻尼力特性的研究.由于电极板的大小直接影响到流体流动的剪力及避震器的阻尼力,因此使用多极板型式来探讨避震器的特性.设计有1~5个流道之并联及1~3个流道之串联多极板电流变阀的电流变避震器,并使用自制的电流变液进行实验.由研究结果显示,流动式并联极板之电流变避震器,一个流道之阻尼力最大,流道极板增加则阻尼力反而下降,而流动式串联多极板之电流变避震器之阻尼力则随极板数递增,故需要高阻尼力之避震器较适合使用串联多极板型式.  相似文献   
934.
 A novel alcohol-soluble polyorganosiloxane containing amino side groups, poly[3-(4-aminophenoxy)propylmethylsiloxane] (2), was first prepared by the reduction of nitro groups on 4-nitrophenoxypropyl side chains of poly[3-(4-nitrophenoxy)propylmethylsiloxane] (1). The reaction proceeded easily with nearly 100% conversion. The synthesized alcohol-soluble polymer 2, which has potential application as a precursor for preparing advanced functional polymers, was characterized by FTIR 1H-NMR, 13C-NMR, 29Si-NMR, VPO and GPC, respectively.  相似文献   
935.
Exposure to BPS induced glycerophospholipid fatty acid remodeling, which might be useful in toxicity evaluation for bisphenols-induced hepatic diseases.  相似文献   
936.
Protein–ligand docking is a useful tool for providing atomic-level understanding of protein functions in nature and design principles for artificial ligands or proteins with desired properties. The ability to identify the true binding pose of a ligand to a target protein among numerous possible candidate poses is an essential requirement for successful protein–ligand docking. Many previously developed docking scoring functions were trained to reproduce experimental binding affinities and were also used for scoring binding poses. However, in this study, we developed a new docking scoring function, called GalaxyDock BP2 Score, by directly training the scoring power of binding poses. This function is a hybrid of physics-based, empirical, and knowledge-based score terms that are balanced to strengthen the advantages of each component. The performance of the new scoring function exhibits significant improvement over existing scoring functions in decoy pose discrimination tests. In addition, when the score is used with the GalaxyDock2 protein–ligand docking program, it outperformed other state-of-the-art docking programs in docking tests on the Astex diverse set, the Cross2009 benchmark set, and the Astex non-native set. GalaxyDock BP2 Score and GalaxyDock2 with this score are freely available at http://galaxy.seoklab.org/softwares/galaxydock.html.  相似文献   
937.
938.
We report the synthesis of linear‐ and brush‐type poly(?‐caprolactone) (PCL) networks and investigate their thermal, mechanical, and shape memory behavior. Brush‐PCLs are prepared by ring‐opening metathesis polymerization (ROMP) of a norbornenyl‐functionalized ?‐caprolactone macromonomer (MM‐PCL) of different molecular weights. The linear analog, diacrylate end‐functionalized PCL (linear‐PCL), having comparable molecular weight of side chain of brush‐PCL is also synthesized. These polymers are thermally cured by a radical initiator in the presence of poly(ethylene glycol) diacrylate crosslinker. Thermal and linear viscoelastic properties as well as shape memory performance of the resulting PCL networks are investigated, and are significantly impacted by the PCL architecture. Therefore, our work highlights that tailoring macromolecular architecture is useful strategy to manipulate thermal, mechanical, and resulting shape memory properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3424–3433  相似文献   
939.
Environmental samples of beach sand taken at northern Taiwan have been monitored using a coincident gamma-ray spectrometer. The concentration of134Cs, under intense interference from natural and other artificial radioactivity, is determined as low as 0.2 Bq/kg dry. The accumulation of trace levels of134Cs originates from the discharge of nuclear power plants nearby.  相似文献   
940.
Liquids' contact angle hysteresis and critical retention volumes on five commonly used plastics with surface structures were studied. The chevron‐like groove structures, which are orthogonally arranged, make the liquid–solid contact line elongated while the droplet found staying in the Wenzel state. Various dimensions of surface structures were represented by contact length ratio σ. Advancing and receding contact angles of liquids on polymer surfaces with various conditions were reported. Reduced hysteresis H, which links between advancing and receding contact angles, was also studied and found to extend its availability on structured surfaces. The research found that surface structures have linear effects on liquids' advancing contact angles in the range of σ = 1.0 to 1.42. Linear regression analysis was hence proposed to predict advancing contact angles, and the results indicate that approximate 80% of data points have less than 6% error. An empirical model, which adopts liquid–solid surface tension as the source of liquids' retention force, was proposed to estimate liquids' critical retention volumes on inclined surfaces. The proposed model found good agreements with existing experiment data and demonstrated its superiority over previous ones. The present model provides an approach to predict liquids' storage/repellency on structured surfaces when the advancing contact angles are predictable. Copyright © 2016 John Wiley & Sons, Ltd.  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