全文获取类型
收费全文 | 62734篇 |
免费 | 6171篇 |
国内免费 | 22篇 |
专业分类
68927篇 |
出版年
2023年 | 253篇 |
2022年 | 518篇 |
2021年 | 1050篇 |
2020年 | 657篇 |
2019年 | 837篇 |
2018年 | 1024篇 |
2017年 | 907篇 |
2016年 | 1525篇 |
2015年 | 2554篇 |
2014年 | 2811篇 |
2013年 | 3292篇 |
2012年 | 4376篇 |
2011年 | 4225篇 |
2010年 | 2692篇 |
2009年 | 2454篇 |
2008年 | 3513篇 |
2007年 | 3537篇 |
2006年 | 3368篇 |
2005年 | 3208篇 |
2004年 | 3148篇 |
2003年 | 2863篇 |
2002年 | 2813篇 |
2001年 | 972篇 |
2000年 | 815篇 |
1999年 | 897篇 |
1998年 | 903篇 |
1997年 | 631篇 |
1996年 | 554篇 |
1995年 | 511篇 |
1994年 | 535篇 |
1993年 | 542篇 |
1992年 | 698篇 |
1991年 | 574篇 |
1990年 | 552篇 |
1989年 | 563篇 |
1988年 | 513篇 |
1987年 | 478篇 |
1986年 | 451篇 |
1985年 | 436篇 |
1984年 | 501篇 |
1983年 | 438篇 |
1982年 | 456篇 |
1981年 | 417篇 |
1980年 | 430篇 |
1979年 | 359篇 |
1978年 | 329篇 |
1977年 | 302篇 |
1976年 | 302篇 |
1975年 | 243篇 |
1974年 | 270篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Miranda Kleijn Harry O. Voorma Adri A. M. Thomas 《Journal of cellular biochemistry》1995,59(4):443-452
Mitogenic stimulation of protein synthesis is accompanied by an increase in elF-4E phosphorylation. The effect on protein synthesis by induction of differentiation is less well known. We treated P19 embryonal carcinoma cells with the differentiating agent retinoic acid and found that protein synthesis increased during the first hour of addition. However, the phosphorylation state, as well as the turnover of phosphate on elF-4E, remained unchanged. Apparently, the change in protein synthesis after RA addition is regulated by another mechanism than elF-4E phosphorylation. By using P19 cells overexpressing the EGF receptor, we show that the signal transduction pathway that leads to phosphorylation of elF-4E is present in P19 cells; the EGF-induced change in phosphorylation of elF-4E in these cells is likely to be regulated by a change in elF-4E phosphatase activity. These results suggest that the onset of retinoic acid-induced differentiation is triggered by a signal transduction pathway which involves changes in protein synthesis, but not elF-4E phosphorylation. © 1995 Wiley-Liss, Inc. 相似文献
62.
Thomas Scheper 《Journal of industrial microbiology & biotechnology》1992,9(3-4):163-172
Summary A short review about the biosensor research activities for bioprocess monitoring in the F.R.G. after its reunification is given. The principles of biosensor applications are presented. In situ sensors and sensors based on the principles of flow injection analysis are studied. Some applications of a four-channel enzyme thermistor, bio-field effect transistors, and immunoanalysis systems for real process monitoring are presented. 相似文献
63.
A food-producing role for cephalic exocrine glands has arisen independently in both taxa of highly eusocial bees, Apis and Meliponini. With several exceptions, there is little evidence that food is produced by glands of solitary bees or by most bees at lower levels of sociality. We suggest that this association with sociality is due to four adaptive features of these glands: (1) food from the glands allows feces from queens and larvae to have a small volume, (2) the queen's fecundity can be increased, (3) nutrient recovery via cannibalism can be facilitated, and (4) rearing of emergency replacement queens is accelerated. Acceleration of the rearing of other castes and of queens in the normal process of colony fission is not clearly an advantage ascribed to these glands. Trophic eggs produced by meliponine colony workers are analogous to the secretions from food-producing glands in Meliponini and Apis workers. 相似文献
64.
Utilizing horseradish peroxidase as a tracer protein, it is shown that trichogen and tormogen cells have a secretory function. Protein tracer from the haemolymph enters these cells by endocytosis and is transported to the sensillum liquor cavity by transport vacuoles and multivesicular bodies. It is also suggested that closely associated pigment cells may be involved in macromolecular transport. 相似文献
65.
66.
67.
68.
69.
Kasper Stovgaard Christian Andreetta Jesper Ferkinghoff-Borg Thomas Hamelryck 《BMC bioinformatics》2010,11(1):429
Background
Genome sequencing projects have expanded the gap between the amount of known protein sequences and structures. The limitations of current high resolution structure determination methods make it unlikely that this gap will disappear in the near future. Small angle X-ray scattering (SAXS) is an established low resolution method for routinely determining the structure of proteins in solution. The purpose of this study is to develop a method for the efficient calculation of accurate SAXS curves from coarse-grained protein models. Such a method can for example be used to construct a likelihood function, which is paramount for structure determination based on statistical inference. 相似文献70.
Effect of Phosphate on the Corrosion of Carbon Steel and on the Composition of Corrosion Products in Two-Stage Continuous Cultures of Desulfovibrio desulfuricans 总被引:9,自引:4,他引:5 下载免费PDF全文
Paul J. Weimer Margaret J. Van Kavelaar Charles B. Michel Thomas K. Ng 《Applied microbiology》1988,54(2):386-396
A field isolate of Desulfovibrio desulfuricans was grown in defined medium in a two-stage continuous culture apparatus with different concentrations of phosphate in the feed medium. The first state (V1) was operated as a conventional chemostat (D = 0.045 h−1) that was limited in energy source (lactate) or phosphate. The second stage (V2) received effluent from V1 but no additional nutrients, and contained a healthy population of transiently starved or resting cells. An increase in the concentration of phosphate in the medium fed to V1 resulted in increased corrosion rates of carbon steel in both V1 and V2. Despite the more rapid corrosion observed in growing cultures relative to that in resting cultures, corrosion products that were isolated under strictly anaerobic conditions from the two culture modes had similar bulk compositions which varied with the phosphate content of the medium. Crystalline mackinawite (Fe9S8), vivianite [Fe3(PO4)2 · 8H2O], and goethite [FeO(OH)] were detected in amounts which varied with the culture conditions. Chemical analyses indicated that the S in the corrosion product was almost exclusively in the form of sulfides, while the P was present both as phosphate and as unidentified components, possibly reduced P species. Some differential localization of S and P was observed in intact corrosion products. Cells from lactate-limited, but not from phosphate-limited, cultures contained intracellular granules that were enriched in P and Fe. The results are discussed in terms of several proposed mechanisms of microbiologically influenced corrosion. 相似文献