全文获取类型
收费全文 | 536155篇 |
免费 | 56983篇 |
国内免费 | 409篇 |
出版年
2018年 | 5246篇 |
2017年 | 4975篇 |
2016年 | 6954篇 |
2015年 | 8804篇 |
2014年 | 10597篇 |
2013年 | 14614篇 |
2012年 | 16517篇 |
2011年 | 17231篇 |
2010年 | 11544篇 |
2009年 | 10668篇 |
2008年 | 15094篇 |
2007年 | 15389篇 |
2006年 | 14821篇 |
2005年 | 14095篇 |
2004年 | 13872篇 |
2003年 | 13392篇 |
2002年 | 13087篇 |
2001年 | 26850篇 |
2000年 | 27039篇 |
1999年 | 20857篇 |
1998年 | 6518篇 |
1997年 | 6736篇 |
1996年 | 6398篇 |
1995年 | 5868篇 |
1994年 | 5768篇 |
1993年 | 5764篇 |
1992年 | 16452篇 |
1991年 | 16233篇 |
1990年 | 15790篇 |
1989年 | 15507篇 |
1988年 | 14514篇 |
1987年 | 13602篇 |
1986年 | 12228篇 |
1985年 | 12378篇 |
1984年 | 9863篇 |
1983年 | 8619篇 |
1982年 | 6179篇 |
1981年 | 5579篇 |
1980年 | 5248篇 |
1979年 | 9053篇 |
1978年 | 7017篇 |
1977年 | 6432篇 |
1976年 | 5982篇 |
1975年 | 6820篇 |
1974年 | 7243篇 |
1973年 | 7175篇 |
1972年 | 6293篇 |
1971年 | 5863篇 |
1970年 | 5222篇 |
1969年 | 4918篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A A Gureeva A V Sanin V O Rybin N S Barteneva I A Lapaeva 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1986,(5):63-66
Effect of B. pertussis lymphocytosis-promoting factor (LPF) on the lympho-hematopoietic system of mice was studied. The injection of LPF was shown to sharply enhance endogenous colony formation and to induce a severe depletion of thymus cells, reaching its maximum of day 4. Thymocytes obtained on day 2 or 3 after the injection of LPF produced a suppressive effect on endogenous colony formation. The proliferative activity of hematopoietic stem cells sharply increased under the influence of LPF, though it had no radioprotective action. On the following day after the injection of LPF a steep rise in the number of hematopoietic stem cells was observed in the blood of mice: their content increased 20-fold in comparison with the control level. These data may be important for the evaluation of the side effects of pertussis vaccine on the lympho-hematopoietic system. 相似文献
92.
S K Litvinov A V Lobanov A N Peregudov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1986,(11):78-84
The Expanded Programme on Immunization (EPI) whose goal is to reduce morbidity and mortality by providing children with immunizations against diphtheria, pertussis, tetanus, poliomyelitis, measles, and tuberculosis continually faces the problem of documenting immunization coverage rates. Therefore the EPI seeks simple, effective, and inexpensive methods of evaluation which could be implemented in different countries. An example of such a method is a simplified cluster sampling technique of estimation of immunization coverage through the examination of 210 children, selected randomly as 30 groups of 7 children each. In 1978-1984 more than 1000 immunization coverage surveys were performed all over the world, mainly in developing countries. In a modified way this method is also used to collect data on morbidity and mortality of certain EPI target diseases as well as diarrhoeal diseases. 相似文献
93.
Keratinocyte growth-promoting activity from human placenta 总被引:4,自引:0,他引:4
Extracts of term human placenta were tested for enhancement of proliferative growth of primary cultures of human keratinocytes. Saline extracts or supernatants from homogenates were dialyzed extensively, lyophilized, and tested in subcultures of keratinocytes in MCDB 153 medium with 0.1 mM Ca++ containing only defined supplements (insulin, hydrocortisone, transferrin, ethanolamine, phosphoethanolamine). Cells plated in the absence of EGF at moderately high densities (1000-3000 cells per cm2) formed colonies and grew in the presence of placental extract at 25-500 micrograms/ml. Extracts of cord serum or maternal serum were inactive, suggesting that the activity is derived from placental tissue. The activity is not EGF, since the activity in the placental extract, unlike EGF, did not promote growth at low cell density, was synergistic with EGF under some conditions, and did not produce changes in colonial morphology which occurred in the presence of EGF. Unlike keratinocyte growth-promoting activity in bovine hypothalamic extract, the activity is non-dialyzable and is destroyed at 100 degrees C. Placental extract could not replace any of the defined components of the medium and is therefore distinct from them. The presence of activity in the placenta with distinctive properties suggests that this is a previously undescribed material with growth-promoting properties for epithelium. 相似文献
94.
95.
96.
97.
98.
99.
100.
The ability of human uterine endometrium to aromatize androstenedione to estrogens was investigated using 10 normal and neoplastic tissues. Normal and neoplastic endometrial homogenates were incubated with [6,7-3H]androstenedione (A) and NADPH. Estrone (E1) and estradiol (E2) were subsequently isolated in amounts ranging from 0-17600 fmol/h/g and 0-377 fmol/h/g, respectively, from the incubates after purifications by using Bio-Rad AG1-X2 column, thin layer chromatographies and co-crystallization. The conversion of A to E1 and E2 was significantly higher in neoplastic tissues. 相似文献