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   1361篇
  免费   68篇
  1429篇
  2022年   6篇
  2021年   16篇
  2019年   9篇
  2018年   14篇
  2017年   7篇
  2016年   16篇
  2015年   18篇
  2014年   30篇
  2013年   86篇
  2012年   68篇
  2011年   49篇
  2010年   36篇
  2009年   41篇
  2008年   59篇
  2007年   50篇
  2006年   74篇
  2005年   85篇
  2004年   92篇
  2003年   119篇
  2002年   93篇
  2001年   9篇
  2000年   14篇
  1999年   14篇
  1998年   32篇
  1997年   24篇
  1996年   28篇
  1995年   22篇
  1994年   12篇
  1993年   15篇
  1992年   16篇
  1991年   8篇
  1990年   10篇
  1989年   18篇
  1988年   10篇
  1987年   10篇
  1986年   12篇
  1985年   9篇
  1984年   15篇
  1983年   17篇
  1982年   24篇
  1981年   20篇
  1980年   19篇
  1979年   12篇
  1978年   7篇
  1977年   11篇
  1976年   18篇
  1975年   10篇
  1974年   9篇
  1973年   7篇
  1972年   5篇
排序方式: 共有1429条查询结果,搜索用时 7 毫秒
1.
2.
Purification of Protein Body-I of Rice Seed and its Polypeptide Composition   总被引:16,自引:0,他引:16  
Protein body type one (PB-I) was isolated and purified fromdeveloping rice grain by a combination of sucrose density gradientcentrifugation and treatment with pepsin. SDS-PAGE analysisshowed that isolated PB-I contains several polypeptide groups,the largest having an apparent molecular size of 13 kDa andtwo smaller ones of 10 kDa and 16 kDa. The 13-kDa group wasfound to be composed of two polypeptides of slightly differentmolecular sizes, 13a (larger component) and 13b (smaller component).Most of the 13a and 13b polypeptides were shown to be largelyprolamins, although there were also some salt- and alcohol-insolublepolypeptides with an apparent molecular size of 13 kDa. It wasconcluded that PB-I is the accumulation site of rice prolamin.It was further estimated that the protein amount in PB-I accountedfor about 20% of the total protein of rice endosperm. (Received March 20, 1987; Accepted September 8, 1987)  相似文献   
3.
4.
The effect of temperature on the content of the medullary depside divaricatic acid or the hymenial depsidone salazinic acid inRamalina subbrevisuscula was examined. The higher the contents of both lichen substances, the higher the annual mean temperature of the habitat. The plants growing on dark-colored rocks contained a larger amount of these lichen substances than those growing on the light-colored rocks in the same temperature zone. Thus, the temperature on or near the surface of the rock seems to control the contents of both medullary and hymenial compounds inR. subbreviuscula as well as the content of salazinic acid inR. siliquosa (Hamada, 1982b).  相似文献   
5.
Summary Using the polymorphic DNA probes, ChdTC-15, ChdTC-114, pYNH24, and λTM-18, a DNA profiling system was developed that verified identities of individual cultured cell lines collected in the Japanese cell banks, JCRB, RCB, and IFO. These highly polymorphic DNA probes include both VNTR (Variable Number of Tandem Repeats) sequences and substantial lengths of unique regions. In the mixed probe system, several distinct bands from four to eight can be used for cell line identification. These bands were widely spread in a range of molecular sizes, and were stable and reproducible under stringent conditions of Southern blot hybridization. Because the DNA profile was specific for each individual human cell line, it is useful not only to authenticate many existing cultured cell lines but also to monitor their identity during propagation in a laboratory, and to confirm newly established lines as unique.  相似文献   
6.
We demonstrated that each of various polyclonal lymphocyte activators (PLA) exhibits two types of adjuvant action to initiate the carrier-specific helper T-cell response to otherwise nonimmunogenic antigen. Type 1 action was characterized as that to initiate the T-cell response to subcutaneous injection of soluble bovine γ-globulin (BGG), and type 2 as that to initiate the response to intravenous injection of aggregated BGG. Each of various PLA showed these two types of adjuvant action in a dissociated fashion. The capsular polysaccharide of Klebsiella pneumoniae (CPS-K) showed both types of action to the highest degrees. Lipopolysaccharide of Escherichia coli exhibited type 2 action as markedly as CPS-K, but failed to show type 1 action. Concanavalin A showed definite type 1 action, but not type 2 action. Polyadenylic-uridylic acid showed definite type 2 action, but not type 1 action. Type 1 and type 2 actions of dextran sulfate were minimal. A hypothetical view is presented to consider that type 1 adjuvant action is directed to two mutually independent sites whereas type 2 action is directed to one site.  相似文献   
7.
Copper-binding proteins were extracted from a copper-resistantstrain of Saccharomyces cerevisiae which was obtained by repeatedsubculturing in a copper-containing medium. They were separatedinto three types through purification steps such as salt fractionation,gel filtration and preparative polyacrylamide gel electrophoresis.They resembled each other in amino acid composition. Acidicamino acids, lysine, serine, glycine and half-cystine constituteda large part of the protein, with a small amount of hydrophobicamino acids. Aromatic amino acids and methionine were almostabsent. The molecular weight of the components was estimatedto be about 10,000 by Sephadex gel filtration and electrophoresison polyacrylamide gel (slope method). Absorption spectra ofthe components exhibited a broad band at 275 nm, but none inthe visible region, thus resembling that of copper-thionein.Moreover, the absorption band at 275 nm changed markedly onaddition of Ag+, Hg2+, CN or H2O2, which are well knownas thiol reagents. These components were abo produced in theparent cells, if they could grow in a copper-containing medium.Based the results of experiments using various culture conditionsand some other yeast species, a possible role of the componentsis discussed. (Received July 13, 1976; )  相似文献   
8.
Serum lipoproteins of the bullfrog, Rana catesbeiana, were studied during metamorphosis. Adult bullfrog has essentially one lipoprotein, designated β-lipoprotein. This β-lipoprotein migrates during electrophoresis to β-globulin region and it has a low hydrated density such that it exhibits floatation in a solvent of density 1.063. On the other hand, tadpole serum has one more lipoprotein, designated as α-lipoprotein, in addition to the β-lipoprotein. The α-lipoprotein migrates to the α-globulin region in zone electrophoresis and corresponds to the so called high density lipoprotein judging from ultracentrifugal behavior. Serum α-lipoprotein disappears and β-lipoprotein content decreases during metamorphosis.  相似文献   
9.
Steroidal allenes, stigmasta-5,24(28),28-trien-3β-ol (allene-I) and cholesta-5,23,24-trien-3β-ol (allene-II), were tested for their inhibitory effects on growth, development, and steroid metabolism in the silkworm, Bombyx mori. The allenic analogue (I) of stigmasta-5,24(28)-dien-3β-ol (2) was found to be a specific inhibitor for the conversion of stigmast-5-en-3β-ol (1) to stigmasta-5, 24(28)-dien-3β-ol (2) and/or stigmasta-5,24(28)-dien-3β-ol (2) to 24,28-epoxy-stigmast-5-en-3β-ol (3) This inhibitor held the larvae in the second instar for more than 20 days without developing to the third instar, when administered alone or with the dietary sterols of stigmast-5-en-3β-ol (1) or stigmasta-5,24(28)-dien-3β-ol (2). The second allene (II) with a similar structure to cholesta-5,24-dien-3β-ol (4) was also found to be an inhibitor for insect growth and development, but it appeared not to be acting via inhibition of sterol dealkylation.  相似文献   
10.
To examine the differences of the growth and reproduction of different-aged plants, 0-, 1-, and 2-year plants ofAmorphophalus konjac were investigated. RGR and daily net production per unit productive part, relative net-production rate (α′), of the 0-year plant were largest, although NAR was highest in the 2-year plant. This was due to the large LAR of the 0-year plant, owing to its large SLA. With increase in age, LAR decreased and NAR increased. Thus, it appeared that the age of plant exerts two opposite effects on dry-matter production. Since these effects cancel each other out, differences in RGR and α′ between the two older plants were not significant. We estimated that plant size appears to be primarily responsible for these effects. The 0-year plant showed the least distribution ratio of net production into reproductive (storage) organs, and the highest productivity of the reproductive part. The ratio of the production of corm to total reproductive-part production, the D-reproduction index, was independent of age, and critical size in vegetative propagation could not be detected.  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