全文获取类型
收费全文 | 1628篇 |
免费 | 134篇 |
国内免费 | 2篇 |
专业分类
1764篇 |
出版年
2022年 | 15篇 |
2021年 | 23篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 24篇 |
2017年 | 22篇 |
2016年 | 41篇 |
2015年 | 71篇 |
2014年 | 69篇 |
2013年 | 88篇 |
2012年 | 130篇 |
2011年 | 107篇 |
2010年 | 82篇 |
2009年 | 71篇 |
2008年 | 123篇 |
2007年 | 101篇 |
2006年 | 106篇 |
2005年 | 102篇 |
2004年 | 98篇 |
2003年 | 90篇 |
2002年 | 77篇 |
2001年 | 34篇 |
2000年 | 13篇 |
1999年 | 25篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 14篇 |
1991年 | 11篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 8篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1968年 | 3篇 |
1965年 | 2篇 |
排序方式: 共有1764条查询结果,搜索用时 15 毫秒
31.
Mylenne Calciolari Pinheiro Silva Aline Fernandes Figueiredo Fernando Dini Andreote Elke Jurandy Bran Nogueira Cardoso 《World journal of microbiology & biotechnology》2013,29(1):163-171
Brachiaria brizantha is considered one of the preferred fodders among farmers for having high forage yield and large production of root mass. The association of beneficial bacteria with these grasses can be very valuable in the recovery of the pasture areas with nutritional deficiency. With the aim of studying this possibility, we carried out the sampling of soil and roots of B. brizantha in three areas (Nova Odessa-SP, S?o Carlos-SP and Campo Verde-MT, Brazil). Seventy-two bacterial strains were isolated and used in tests to evaluate their biotechnological potential. Almost all isolates presented at least one positive feature. Sixty-eight isolates produced analogues of indole-3-acetic acid, ten showed nitrogenase activity when subjected to the method of increasing the concentration of total nitrogen (total N) in the culture medium and sixty-five isolates showed nitrogenase activity when subjected to acetylene reduction technique. The partial sequencing of 16S rRNA of these isolates allowed the identification of seven main groups, with the prevalence of those affiliated to the genus Stenotrophomonas (69?%). At the end, this work elected the strains C4 (Pseudomonadaceae) and C7 (Rhodospirillaceae) as promising organisms for the development of inoculants due to their higher nitrogenase activity. 相似文献
32.
33.
34.
Carcass decomposition largely depends on vertebrate scavengers. However, how behavioral differences between vertebrate scavenger species, the dominance of certain species, and the diversity of the vertebrate scavenger community affect the speed of carcass decomposition is poorly understood. As scavenging is an overlooked trophic interaction, studying the different functional roles of vertebrate species in the scavenging process increases our understanding about the effect of the vertebrate scavenger community on carcass decomposition. We used motion‐triggered infrared camera trap footages to profile the behavior and activity of vertebrate scavengers visiting carcasses in Dutch nature areas. We grouped vertebrate scavengers with similar functional roles. We found a clear distinction between occasional scavengers and more specialized scavengers, and we found wild boar (Sus scrofa) to be the dominant scavenger species in our study system. We showed that these groups are functionally different within the scavenger community. We found that overall vertebrate scavenger diversity was positively correlated with carcass decomposition speed. With these findings, our study contributes to the understanding about the different functional roles scavengers can have in ecological communities. 相似文献
35.
Nevoigt E Pilger R Mast-Gerlach E Schmidt U Freihammer S Eschenbrenner M Garbe L Stahl U 《FEMS yeast research》2002,2(2):225-232
The GPD1 gene encoding the glycerol-3-phosphate dehydrogenase was overexpressed in an industrial lager brewing yeast (Saccharomyces cerevisiae ssp. carlsbergensis) to reduce the content of ethanol in beer. The amount of glycerol produced by the GPD1-overexpressing yeast in fermentation experiments simulating brewing conditions was increased 5.6 times and ethanol was decreased by 18% when compared to the wild-type. Overexpression of GPD1 does not affect the consumption of wort sugars. Only minor changes in the concentration of higher alcohols, esters and fatty acids could be observed in beer produced by the GPD1-overexpressing brewing yeast. However, the concentrations of several other by-products, particularly acetoin, diacetyl and acetaldehyde, were considerably increased. 相似文献
36.
Glutamate Dehydrogenase Is Not Essential for Glutamate Formation by Corynebacterium glutamicum 下载免费PDF全文
Elke R. Brmann-El Kholy Bernhard J. Eikmanns Marcella Gutmann Hermann Sahm 《Applied microbiology》1993,59(7):2329-2331
Two Corynebacterium glutamicum strains, one being glutamate dehydrogenase (GDH) negative and the other possessing 11-fold-higher specific GDH activity than the parental wild type, were constructed and used to analyze the role of GDH in C. glutamicum. The results indicate (i) that GDH is dispensable for glutamate synthesis required for growth and (ii) that although a high level of GDH increases the intracellular glutamate pool, the level of GDH has no influence on glutamate secretion. 相似文献
37.
Elke Genersch 《Applied microbiology and biotechnology》2010,87(1):87-97
Managed honey bees are the most important commercial pollinators of those crops which depend on animal pollination for reproduction
and which account for 35% of the global food production. Hence, they are vital for an economic, sustainable agriculture and
for food security. In addition, honey bees also pollinate a variety of wild flowers and, therefore, contribute to the biodiversity
of many ecosystems. Honey and other hive products are, at least economically and ecologically rather, by-products of beekeeping.
Due to this outstanding role of honey bees, severe and inexplicable honey bee colony losses, which have been reported recently
to be steadily increasing, have attracted much attention and stimulated many research activities. Although the phenomenon
“decline of honey bees” is far from being finally solved, consensus exists that pests and pathogens are the single most important
cause of otherwise inexplicable colony losses. This review will focus on selected bee pathogens and parasites which have been
demonstrated to be involved in colony losses in different regions of the world and which, therefore, are considered current
threats to honey bees and beekeeping. 相似文献
38.
Elke Rabbow Gerda Horneck Petra Rettberg Jobst-Ulrich Schott Corinna Panitz Andrea L’Afflitto Ralf von Heise-Rotenburg Reiner Willnecker Pietro Baglioni Jason Hatton Jan Dettmann René Demets Günther Reitz 《Origins of life and evolution of the biosphere》2009,39(6):581-598
Following an European Space Agency announcement of opportunity in 1996 for ”Externally mounted payloads for 1st utilization phase” on the International Space Station (ISS), scientists working in the fields of astrobiology proposed experiments aiming at long-term exposure of a variety of chemical compounds and extremely resistant microorganisms to the hostile space environment. The ESA exposure facility EXPOSE was built and an operations´ concept was prepared. The EXPOSE experiments were developed through an intensive pre-flight experiment verification test program. 12 years later, two sets of astrobiological experiments in two EXPOSE facilities have been successfully launched to the ISS for external exposure for up to 1.5 years. EXPOSE-E, now installed at the balcony of the European Columbus module, was launched in February 2008, while EXPOSE-R took off to the ISS in November 2008 and was installed on the external URM-D platform of the Russian Zvezda module in March 2009. 相似文献
39.
Changes of the hepatic proteome in murine models for toxically induced fibrogenesis and sclerosing cholangitis 总被引:1,自引:0,他引:1
Henkel C Roderfeld M Weiskirchen R Berres ML Hillebrandt S Lammert F Meyer HE Stühler K Graf J Roeb E 《Proteomics》2006,6(24):6538-6548
We investigated the changes in the hepatic proteome in murine models for toxic-induced fibrogenesis and sclerosing cholangitis. A comprehensive comparison of protein changes observed is made and the mechanistical basis of the expression changes is discussed. Hepatic fibrosis was induced by repetitive intraperitoneal CCl4 treatment of BALB/c mice or developed spontaneously in BALB/c-ATP-binding cassette, subfamily B, member 4 (Abcb4) knock out mice. Fibrosis was verified by a morphometric score and assessment of hydroxyproline content of liver tissue, respectively. The innovative difference in-gel electrophoresis (DIGE) technique was used to analyse protein expression levels of the mouse proteome. Results were confirmed by Western blotting and real-time RT-PCR. In CCl4-induced fibrosis 20 out of 40 and in BALB/c-Abcb4(-/-) mice 8 out of 28 differentially expressed proteins were identified utilizing DIGE. Only two proteins, selenium-binding protein (Sbp2) and carbonic anhydrase 3, have been unidirectionally expressed (i.e. down-regulated) in both models. Relevant differences in the pathogenesis of toxically induced liver fibrosis and sclerosing cholangitis exist. The only novel protein with regard to liver fibrosis depicting a unidirectional expression pattern in both animal models was Sbp2. An explicit protein function could not be clarified yet. 相似文献
40.
Noens EE Mersinias V Willemse J Traag BA Laing E Chater KF Smith CP Koerten HK van Wezel GP 《Molecular microbiology》2007,64(5):1244-1259