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   262398篇
  免费   18952篇
  国内免费   60篇
  281410篇
  2021年   2412篇
  2019年   2192篇
  2018年   3794篇
  2017年   3633篇
  2016年   4672篇
  2015年   4857篇
  2014年   6247篇
  2013年   8572篇
  2012年   10297篇
  2011年   10720篇
  2010年   7504篇
  2009年   6435篇
  2008年   9353篇
  2007年   9655篇
  2006年   9231篇
  2005年   8525篇
  2004年   8663篇
  2003年   8200篇
  2002年   8133篇
  2001年   9875篇
  2000年   9528篇
  1999年   7568篇
  1998年   2535篇
  1997年   2288篇
  1996年   2136篇
  1995年   1995篇
  1992年   5867篇
  1991年   6015篇
  1990年   5972篇
  1989年   5966篇
  1988年   5558篇
  1987年   5182篇
  1986年   4701篇
  1985年   4959篇
  1984年   3987篇
  1983年   3280篇
  1982年   2264篇
  1981年   1946篇
  1979年   3543篇
  1978年   2751篇
  1977年   2553篇
  1976年   2505篇
  1975年   3016篇
  1974年   3275篇
  1973年   3243篇
  1972年   2881篇
  1971年   2726篇
  1970年   2327篇
  1969年   2271篇
  1968年   2117篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
The data presented in this work indicate that specific antisera to P. aeruginosa and Proteus antigens can be produced by using extracts from these microorganisms, destroyed by ultrasonic treatment or by multiple freezing and thawing, for the immunization of rabbits. Blood serum samples from patients with purulent septic complications were studied for the presence of P. aeruginosa and Proteus antigens in ELISA with the use of peroxidase-labeled antibodies from antisera to P. aeruginosa and Proteus. This investigation revealed that during the first 3 days from the beginning of the clinical manifestations of the complications P. aeruginosa and Proteus antigens were detected in 86.4% and 83.4% of the patients, respectively. In the subsequent bacteriological study of wound discharge from these patients the corresponding microflora was detected.  相似文献   
994.
995.
996.
Clinical, bacteriological, serological and epidemiological studies of ozena morbidity among the population of Minsk were carried out in 1970-1980. On January 1, 1981, the ozena morbidity rate among the inhabitants of Minsk was 26.72%. Ozena was found to affect mainly children and women. A wide spread of the family foci of this disease (31.68%) was revealed. The results of this study indicate that the source of K. ozaenae is a sick person who begins to excrete the bacteria in the prodromal period of the disease and may continue to excrete them for many years. The transfer of K. ozaenae occurs probably by droplet or contact infection. The droplet infection is less active in the absence of symptoms (coughing, sneezing) facilitating excretion of the infective agent into the air and in cases of the low susceptibility of persons to ozena. The main measures for controlling ozena are the timely detection and sanitation of the sources of ozena, as well as the current disinfection of the infection foci in apartments.  相似文献   
997.
998.
The relationship between delayed hypersensitivity (DH) to S. aureus surface antigens and the intensity of the infectious process induced by the sublethal infection of guinea pigs with S. aureus was studied. The protective effect, manifested by a decrease in the staphylococcal contamination of the spleen tissue and by an increase in the level of the activation of lymphocytes, was shown to correlate with DH induced by inactivated staphylococcal cells. In infected guinea pigs having DH to different staphylococcal antigens the disease either took a more severe course (in cases of DH to cell wall or peptidoglycan) than in the animals subjected only to infection, or no aggravation of the disease was observed (in cases of DH to protein A).  相似文献   
999.
The previously described, iodine-labeled alkylating stable nitroxyl radicals located at different distances between the N-O. group and the iodine atom were used for a comparative study of the structure of microsomal cytochromes P-450 and P-448 active centers. The radicals were shown to change the optical spectra of Fe3+ located in the active site of the enzyme that are similar to those induced by cytochrome P-450 substrates. Some differences in the type of the radicals binding to control, phenobarbital- and 3-methylcholanthrene-induced microsomes were revealed. The alkylating radical substrate analogs covalently bound to microsomal cytochrome P-450 in the vicinity of the active center, resulting in the inhibition of oxidation of type I and II substrates (e. g., aniline and naphthalene). The value of the spectral binding constant (Ks) for naphthalene in the presence of the radical covalently bound to the cytochrome P-450 active center showed a tendency to increase. Using the ESR technique, the interaction between Fe3+ and the radical localized in the active site of cytochrome P-450 was demonstrated. The contribution of Fe3+ to the relaxation of the radicals covalently bound to cytochrome P-450 was evaluated from the values of the spin label ESR spectra saturation curves at 77K. The distances between the N-O. group of these radicals and Fe3+ in the enzyme active center for the three types of microsomes were determined. The data obtained point to structural peculiarities of the active center of cytochrome P-450, depending on the microsomal type.  相似文献   
1000.
The addition of ATP or 3,5-AMP (but not UTP, GTP, CTP, AMP, 2,3-AMP, ADP, inorganic pyrophosphate) at a final concentration of 10(-1) M into streptokinase solution, pH 7.0 or 9.5, causes a dramatic inhibition of streptokinase-induced fibrinolysis. The specificity of ATP effect is fully lost at pH 3.0, when all nucleotides completely inhibit the activating function of streptokinase. Ribose-5-phosphate causes a similar effect at pH 3.0. The character of nucleotide action on the activating function of streptokinase considerably differs from their influence on proteolytic reactions.  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