全文获取类型
收费全文 | 282286篇 |
免费 | 24713篇 |
国内免费 | 265篇 |
专业分类
307264篇 |
出版年
2018年 | 3726篇 |
2017年 | 3525篇 |
2016年 | 4753篇 |
2015年 | 5426篇 |
2014年 | 6355篇 |
2013年 | 8931篇 |
2012年 | 9960篇 |
2011年 | 10416篇 |
2010年 | 6972篇 |
2009年 | 5983篇 |
2008年 | 8768篇 |
2007年 | 8950篇 |
2006年 | 8618篇 |
2005年 | 7949篇 |
2004年 | 7859篇 |
2003年 | 7539篇 |
2002年 | 7306篇 |
2001年 | 12903篇 |
2000年 | 12825篇 |
1999年 | 9832篇 |
1998年 | 2955篇 |
1997年 | 2932篇 |
1996年 | 2892篇 |
1995年 | 2682篇 |
1994年 | 2578篇 |
1993年 | 2448篇 |
1992年 | 7601篇 |
1991年 | 7340篇 |
1990年 | 7387篇 |
1989年 | 7182篇 |
1988年 | 6649篇 |
1987年 | 6300篇 |
1986年 | 5625篇 |
1985年 | 5931篇 |
1984年 | 4668篇 |
1983年 | 4050篇 |
1982年 | 2817篇 |
1981年 | 2618篇 |
1980年 | 2427篇 |
1979年 | 4343篇 |
1978年 | 3268篇 |
1977年 | 3008篇 |
1976年 | 2944篇 |
1975年 | 3403篇 |
1974年 | 3655篇 |
1973年 | 3680篇 |
1972年 | 3215篇 |
1971年 | 2990篇 |
1970年 | 2687篇 |
1969年 | 2453篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
971.
972.
973.
N C Tappen 《American journal of physical anthropology》1973,38(1):93-97
Close inspection of surface bone in skulls of Neanderthal man reveals weathering cracks extensive enough in one specimen, La Chapelle-aux-Saints, to allow preliminary analysis of major patterns of orientation and to make inferences about functional relationships of structures. The fine structure of the bone of the brow ridges is very different from the rest of the skull in the two adults examined, having a peculiar vermiculate surface pattern. Weathering cracks do not appear in this region. This indicates that Neanderthal brow ridges are not closely related to normal mechanical forces such as chewing exertion. It may, however, give further support to theories of Neanderthal brow ridges as protection for the eyes. The localized structure of bone often differs from region to region, and offers new possibilities for the analysis of both contemporary and fossil forms. 相似文献
974.
975.
976.
977.
978.
V N Gorbacheva N I Lebedev M V Miakinnikova T M Ovcharenko 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1982,(9):42-45
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
979.
N K Chenas I A Martsinkiavichene Iu Iu Kulis S A Usanov 《Biokhimii?a (Moscow, Russia)》1987,52(4):643-649
The reactions of NADPH oxidation by quinones and inorganic complexes catalyzed by NADPH: adrenodoxin reductase were studied. The catalytic constant for the enzyme at pH 7.0 is 20-25 s-1; the oxidative constants for the quinones vary from 5 X 10(5) to 1.1 X 10(3) M-1 s-1 and show an increase with a rise in the one-electron acceptor reduction potential. The mode of adrenodoxin reductase interaction with oxyquinones differs from that of the enzyme interaction with alkyl-substituted quinones and inorganic complexes. NADPH competitively inhibits electron acceptors, whereas NADP+ is a competitive inhibitor of NADPH and a uncompetitive inhibitor of electron acceptors. (Ki = 25 microM). The depth of FAD incorporation into the enzyme molecule as calculated according to the outer sphere electron transfer theory is 6.1 A. 相似文献
980.
V N Nikandrov N S Pyzhova V I Votiakov 《Biulleten' eksperimental'no? biologii i meditsiny》1987,104(7):49-51
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