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   1675篇
  免费   115篇
  2022年   8篇
  2021年   12篇
  2020年   13篇
  2019年   15篇
  2018年   18篇
  2017年   15篇
  2016年   18篇
  2015年   42篇
  2014年   57篇
  2013年   128篇
  2012年   83篇
  2011年   80篇
  2010年   41篇
  2009年   33篇
  2008年   70篇
  2007年   66篇
  2006年   61篇
  2005年   68篇
  2004年   66篇
  2003年   71篇
  2002年   67篇
  2001年   70篇
  2000年   80篇
  1999年   52篇
  1998年   18篇
  1997年   16篇
  1996年   19篇
  1995年   17篇
  1994年   6篇
  1993年   16篇
  1992年   53篇
  1991年   42篇
  1990年   36篇
  1989年   46篇
  1988年   29篇
  1987年   23篇
  1986年   25篇
  1985年   38篇
  1984年   20篇
  1983年   18篇
  1982年   12篇
  1981年   15篇
  1980年   8篇
  1979年   13篇
  1978年   7篇
  1977年   11篇
  1976年   8篇
  1975年   14篇
  1974年   6篇
  1973年   11篇
排序方式: 共有1790条查询结果,搜索用时 15 毫秒
101.
Biological availability of 23 alcohols, 16 aldehydes and 2 ketones was compared by the mini-test with chicks. Chicks can utilize methanol and ethanol, but not the alcohols of carbon chain from 3 to 9. Lauryl and myristyl alcohols were well utilized but those of higher carbon chain than 14 were not, mainly due to low digestibility. Glycerol and D-sorbitol were well utilized but not 4 other poly alcohols tested. Aldehydes and ketones with free carbonyl group showed low availability or even toxicity, but their derivatives with masked group showed no detrimental effect. Acetaldehyde, acetal and aldehydes of carbon chain longer than 9 were partially utilized.  相似文献   
102.
A polyuronide, main component of the water extract of achine of Ficus awkeotsang MAKINO (on-gyo-tye), was purified by ion-exchange chromatography on DEAE-cellulose. The polyuronide (Fraction IB) is homogeneous electrophoretically and consists mainly of galacturonic acid. Optical rotation of Fraction IB is and content of methoxyl group is trace. In periodate oxidation of Fraction IB, molar ratio of galacturonic acid residue and periodate consumption was 1, and formic acid formation was very small. Periodate oxidation product of Fraction IB was oxidized further with bromine and the resulted substance was hydrolyzed. In the hydrolyzate, presence of large amount of tartaric and glyoxylic acids and small amount of tartronic acid were detected by paper chromatography. Reduced viscosity of aquous solution of Fraction IB increased with decreasing of the concentration of Fraction IB solution. From these results, it was deduced that Fraction IB has a linear structure of 1→4 linkage of d-galacturonic acid, probably α-linkage.  相似文献   
103.
Nodakenetin and marmesin were synthesized from β-resorcylaldehyde through 2-(α-hy-droxyisopropyl)-6-hydroxycoumaran.  相似文献   
104.
105.
A Streptomyces-pepsin inhibitor (S-PI or Pepstatin Ac), and DAN-insensitive carboxyl proteinase was found in a still culture filtrate of Lentinus edodes. The new carboxyl proteinase was purified, and about 9 mg purified enzyme was obtained from 19 liters of culture filtrate, with 11% recovery. The enzyme showed a single band on polyacrylamide gel electrophoresis. The molecular weight and isoelectric point were 40,000 and pH 4.2, respectively. The enzyme did not contain histidine and was composed of 387 amino acid residues. The enzyme was most active between pH 2.7 ~ 2.9, and stable over a pH of 3.2 ~ 5.2 for 3 hr at 37°C. The enzyme was not inhibited by S-PI or synthetic pepsin inhibitors such as DAN and EPNP. The physicochemical and enzymological properties were very similar to those of Scytalidium lignicolum carboxyl proteinase A, which was reported to be an S-PI-, and DAN-insensitive carboxyl proteinase.  相似文献   
106.
Addition of γ-aminobutyric acid (GABA) and angiotensin converting enzyme (ACE)-inhibitory peptides to the pickles was studied in order to develop a new type of pickles that reduce blood pressure. Based on the outcome of these studies, a new type of fermentation bed composed of rice bran and white miso has been successfully developed. The advantage of such pickles is that they not only contain both GABA and ACE-inhibitory peptides, but also that their taste and flavor are excellent, with colors close to the original ones. The new type of pickles could temporarily reduce blood pressure in two types of rats, spontaneously hypertensive rats and NaCl-sensitive model rats. Thus, the newly developed pickles appear to be beneficial for pickle business.  相似文献   
107.
108.
109.
The cell wall of the tip‐growing cells of the giant‐cellular xanthophycean alga Vaucheria frigida is mainly composed of cellulose microfibrils (CMFs) arranged in random directions and the major matrix component into which the CMFs are embedded throughout the cell. The mechanical properties of a cell‐wall fragment isolated from the tip‐growing region, which was inflated by artificially applied pressure, were measured after enzymatic removal of the matrix component by using a protease; the results showed that the matrix component is involved in the maintenance of cell wall strength. Since glucose and uronic acid are present in the matrix component of Vaucheria cell walls, we measured the mechanical properties of the cell wall after treatment with endo‐1,3‐ß‐glucanase and observed the fine structures of its surfaces by atomic force microscopy. The major matrix component was partially removed from the cell wall by glucanase, and the enzyme treatment significantly weakened the cell wall strength without affecting the pH dependence of cell wall extensibility. The enzymatic removal of the major matrix component by using a protease released polysaccharide containing glucose and glucuronic acid. This suggests that the major matrix component of the algal cell walls contains both proteins (or polypeptides) and polysaccharides consisting of glucose and glucuronic acid as the main constituents.  相似文献   
110.
We studied the effects of chronic treatment with a novel angiotensin converting enzyme inhibitor, alpha-[(2S,6R)-6-[(1S)-1-ethoxycarbonyl-3-phenylpropyl]amino-5-oxo-2- (2-thienyl)perhydro-1,4-thiazepin-4-yl]acetic acid.HCl (CS622), and a vasodilator, hydralazine, on plasma atrial natriuretic factor (ANF) levels and kidney ANF receptors in spontaneously hypertensive rats (SHR). Plasma ANF level was decreased and cardiac hypertrophy reduced in CS622 treated SHR, but not in hydralazine treated SHR, although blood pressure was lowered similarly in both SHR groups. The binding capacity of kidney ANF receptors increased and the affinity decreased in CS622 treated SHR compared to untreated SHR. These results suggest that decrease of plasma ANF results from decreased cardiac load but not from lowered blood pressure, and that changes in ANF receptors result from increased plasma ANF.  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