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   7264篇
  免费   753篇
  国内免费   3篇
  2022年   54篇
  2021年   112篇
  2020年   68篇
  2019年   84篇
  2018年   87篇
  2017年   93篇
  2016年   146篇
  2015年   258篇
  2014年   272篇
  2013年   344篇
  2012年   414篇
  2011年   458篇
  2010年   259篇
  2009年   230篇
  2008年   323篇
  2007年   305篇
  2006年   314篇
  2005年   308篇
  2004年   331篇
  2003年   292篇
  2002年   281篇
  2001年   133篇
  2000年   149篇
  1999年   130篇
  1998年   95篇
  1997年   89篇
  1996年   93篇
  1995年   72篇
  1994年   68篇
  1993年   90篇
  1992年   118篇
  1991年   100篇
  1990年   103篇
  1989年   85篇
  1988年   86篇
  1987年   102篇
  1986年   83篇
  1985年   92篇
  1984年   85篇
  1983年   67篇
  1982年   82篇
  1981年   69篇
  1980年   55篇
  1979年   63篇
  1976年   66篇
  1975年   62篇
  1974年   63篇
  1973年   56篇
  1972年   48篇
  1971年   48篇
排序方式: 共有8020条查询结果,搜索用时 31 毫秒
1.
2.
Chick embryo fibroblasts were treated with the monofunctional alkylating agent methylmethane sulfonate at various concentrations for 1 h at 42°C, rinsed and then incubated post-treatment at various temperatures at which the kinetics of alkali-labile bond disappearance was followed. Growth experiments showed that these cells grew similarly at temperatures of either 37°C or 42°C. Repair as assessed by removal of alkali-labile bond was also similar for postincubation in the temperature range 37–42°C for damage due to methylmethane sulfonate treatment at concentrations less than 1.5 mM. When the postincubation temperature was raised higher than 42.5–43°C, this type of repair was stopped. The normal internal body temperature of adult chickens is about 41.6°C. Hence the present finding indicates that chick cells are much more severely restricted in DNA repair at temperatures above normal than are mammalian cells, which can function in this respect for several deg. C above 37°C.  相似文献   
3.
Several unit-length minicircles from the kinetoplast DNA of Leishmania tarentolae were cloned into pBR322 and into M13 phage vectors. The complete nucleotide sequences of three different partially homologous minicircles were obtained. The molecules contained a region of approx. 80% sequence homology extending for 160–270 bp and a region unique to each minicircle. A 14-mer was found to be conserved in all kinetoplast minicircle sequences reported to date. The frequency distributions of various minicircle sequence classes in L. tarentolae were obtained by quantitative gel electrophoresis and by examination of the “T ladder” patterns of minicircles randomly cloned into M13 at several sites. By these methods we could assign approx. 50% of the total minicircle DNA into a minimum of five sequence classes. A sequence-dependent polyacrylamide gel migration abnormality was observed with several minicircle fragments both cloned and uncloned. The abnormality was dependent on the presence of a portion of the conserved region of the minicircle.  相似文献   
4.
5.
6.
7.
8.
The Multiskan spectrophotometric system and Coomassie brilliant blue G-250 protein-dye binding method have been used together to measure NaOH-solubilized protein in subcellular membrane fractions prepared from isolated rat adipose cells. Forty-eight samples can be read in duplicate within 1 min. Sucrose in concentrations up to 0.7 m interfere only moderately with the assay. A rapid and convenient method is, therefore, now available for multiple protein determinations following sucellular fractionation on sucrose gradients.  相似文献   
9.
10.
Segregation of resistance to Meloidogyne arenaria in six BC₅F₂ peanut breeding populations was examined in greenhouse tests. Chi-square analysis indicated that segregation of resistance was consistent with resistance being conditioned by a single gene in three breeding populations (TP259-3, TP262-3, and TP271-2), whereas two resistance genes may be present in the breeding populations TP259-2, TP263-2, and TP268-3. Nematode development in clonally propagated lines of resistant individuals of TP262-3 and TP263-2 was compared to that of the susceptible cultivar Florunner. Juvenile nematodes readily penetrated roots of all peanut genotypes, but rate of development was slower (P = 0.05) in the resistant genotypes than in Florunner. Host cell necrosis indicative of a hypersensitive response was not consistently observed in resistant genotypes of either population. Three RFLP loci linked to resistance at distances of 4.2 to 11.0 centiMorgans were identified. Resistant and susceptible alleles for RFLP loci R2430E and R2545E were quite distinct and are useful for identifying individuals homozygous for resistance in segregating populations.  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