全文获取类型
收费全文 | 3360篇 |
免费 | 186篇 |
国内免费 | 1篇 |
出版年
2021年 | 18篇 |
2020年 | 19篇 |
2019年 | 32篇 |
2018年 | 34篇 |
2017年 | 30篇 |
2016年 | 52篇 |
2015年 | 86篇 |
2014年 | 80篇 |
2013年 | 297篇 |
2012年 | 198篇 |
2011年 | 200篇 |
2010年 | 106篇 |
2009年 | 143篇 |
2008年 | 195篇 |
2007年 | 180篇 |
2006年 | 174篇 |
2005年 | 179篇 |
2004年 | 197篇 |
2003年 | 181篇 |
2002年 | 191篇 |
2001年 | 62篇 |
2000年 | 72篇 |
1999年 | 68篇 |
1998年 | 44篇 |
1997年 | 43篇 |
1996年 | 39篇 |
1995年 | 41篇 |
1994年 | 37篇 |
1993年 | 42篇 |
1992年 | 41篇 |
1991年 | 32篇 |
1990年 | 23篇 |
1989年 | 27篇 |
1988年 | 29篇 |
1987年 | 31篇 |
1986年 | 19篇 |
1985年 | 21篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 30篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 15篇 |
1977年 | 19篇 |
1976年 | 21篇 |
1975年 | 12篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1968年 | 9篇 |
排序方式: 共有3547条查询结果,搜索用时 15 毫秒
31.
32.
33.
Summary The effect of competition pressure on the sequential pattern of adult emergence was studied by using the experimental population
of the azuki bean weevil. The density and pattern of emergence curves of the parental adult induced the changes in the shape
of emergence curve of the progeny as well as the number of progeny individuals. In order to explain these changes, a simple
mathematical model which has two independent variables, the population density and the capacity of environment, was introduced.
The model generated basically similar patterns of emergene curves as observed in the present experiments. This means that
the model displayed well the competition pressure which differentially acted upon early-born and late-born individuals in
the populations being at different densities and which were differentially received by individual progeny according to the
sequential distributions of parents. This different severity of competition pressure resulted in the difference of time when
the pressure compelled influences on the sequential distribution of adult emergence. Therefore, early developed individuals
may have good chance to survive, but the competition pressure works as a factor modifying their fundamental superiority, especially
in the scramble type of competition.
Intense crowding of the azuki bean weevil gave rise to the scramble type of competition in the relation between the numbers
of adults emerged in two successive generations. When parental emergence concentrated in a short term and at high density,
the competition becomes intense, resulting in the inferiority of early developed individuals, in the decrease in number at
the next generation and in the increase of duration for emergence. 相似文献
34.
35.
Power requirements in the agitation of non-Newtonian fermentation broths with and without aeration were measured by a strain gage-type dynamometer. Broth from the production of gluc-amylase by Endomyces species and carboxymethyl cellulose solutions were used as non-Newtonian fluids. In gas–liquid agitation systems, the correlation between Pg and P02 ND3/Q0.56 observed by Michel and Miller was found to be applicable to non-Newtonian fluids in laminar and transition regions. This was particularly true for fluids with apparent viscosities larger than 300 cp. The impeller diameter and impeller blade width had considerable effects on power consumption in a nongassed system. It was suggested, therefore, that Pg/P0 should be correlated by a dimensionless term involving some impeller-size factors. 相似文献
36.
Method for Obtaining Cleaned Putrefactive Anaerobe 3679 Spores 总被引:6,自引:1,他引:5
37.
We compared the removal by solution, the represented count-area method and the beating, for the purpose of estimating the number of the Cryptomeria red mite. Among them the solution procedure provided the smallest standard error as per cent of the mean. 0.25 per cent unheated solution of sodium hydroxide is used for the summer generation, and also 0.25 per cent boiling one for the winter eggs. The mean proportion removed±standard error for the summer eggs and the winter eggs were 0.8770±0.0316 and 0.7920±0.0281 respectively, while 0.9894±0.0050 for the mites. 相似文献
38.
Ariyuki Kagaya Yosuke Uchitomi Akira Kugaya Minoru Takebayashi Ikuo Nagaoka Mitsutaro Muraoka Norio Yokota Shigeto Yamawaki 《Journal of neurochemistry》1996,66(4):1483-1488
Abstract: We investigated the rapid and slow effects of NaF on intracellular signaling systems such as Ca2+ homeostasis and cyclic GMP (cGMP) generation in rat glioma C6 cells, using the Ca2+ -sensitive dye fura-2 and cGMP enzyme immunoassay. We found that the following: (a) NaF enhanced cGMP generation in a concentration-dependent manner. This enhancement was abolished by pretreatment with 100 µ M BAPTA tetraacetoxymethyl ester or in the presence of W-7 in a concentration-dependent manner. N G -Monomethyl- l -arginine (NMMA), a competitive inhibitor of nitric oxide synthase (NOS), also inhibited the NaF-induced generation of cGMP. These results suggest that NaF-induced cGMP generation occurs via a calcium/calmodulin- and NOS-dependent pathway. (b) The basal intracellular Ca2+ concentration ([Ca2+ ]i ) was transiently greater at 1 and 3 h after pretreatment with NaF. W-7 and W-13 antagonized the increase in [Ca2+ ]i , whereas NMMA had little effect. This suggests that the NaF-induced change in basal [Ca2+ ]i was mediated by a calmodulin-dependent pathway but was independent of a NOS-sensitive pathway. (c) The serotonin (5-HT)-induced intracellular mobilization of Ca2+ was reduced by pretreating the cells with NaF. The reduction in Ca2+ mobilization was antagonized by genistein, a tyrosine kinase inhibitor. W-7, W-5, and H-8 had no effect. Results suggest that NaF differentially regulates the cGMP generation, basal [Ca2+ ]i , and 5-HT2A receptor function in C6 glioma cells. 相似文献
39.
40.
Hiroyuki Yamaguchi Hitoshi Miura Kazuoki Ohsumi Takako Osaki Haruhiko Taguchi Tomoko Yamamoto Tomoko Hanawa Sachio Ogata Shigeru Kamiya 《Microbiology and immunology》1996,40(1):77-80
To determine amino acid sequences of the epitopes recognized by monoclonal antibodies (mAbs) 3C8 and 5C3 directed against Yersinia enterocolitica heat-shock protein (HSP60), a dot blot analysis was perfomed using synthesized peptides of Y. enterocolitica HSP60 such as peptides p316-342, p327-359, p340-366, p316-326, p316-321, p319-323, and p321-326 which represent positions of amino acids in Y. enterocolitica HSP60. The dot blot analysis revealed that 5C3 mAb reacted with p316-342, p316-326 and p321-326, and 3C8 mAb p316-342 and p316-326. These results indicate that the epitopes recognized by the mAbs were associated with eleven amino acids, Asp Leu Gly Gln Ala Lys Arg Val Val Ile Asn, of p316-326. The sequence homology between p316-326 of Y. enterocolitica HSP60 and the rest of the HSP60 family suggests that the five amino acids of Lys, Arg, Val, Ile and Asn, which are highly conserved in the HSP60 family, might be related with the epitope recognized by 3C8. In contrast, it was also demonstrated that three amino acids of Leu, Gly and Val, which are not well conserved in the HSP60 family, might be related to the epitope recognized by 5C3. 相似文献