全文获取类型
收费全文 | 696篇 |
免费 | 64篇 |
专业分类
760篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 29篇 |
2015年 | 27篇 |
2014年 | 43篇 |
2013年 | 33篇 |
2012年 | 65篇 |
2011年 | 52篇 |
2010年 | 43篇 |
2009年 | 36篇 |
2008年 | 46篇 |
2007年 | 62篇 |
2006年 | 37篇 |
2005年 | 29篇 |
2004年 | 31篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1980年 | 1篇 |
1971年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有760条查询结果,搜索用时 0 毫秒
121.
122.
Noji Thomas T.; Bathmann Ulrich V.; Bodungen Bodo von; Voss Maren; Antia Avan; Krumbholz Manta; Klein Bert; Peeken Ilka; Noji Carola I.-M.; Rey Francisco 《Journal of plankton research》1997,19(7):863-875
Findings from experiments showed that the web-feeding euthecosomatouspteropod, Limacina retroversa, can produce rapidly sinking,mucous aggregates. It is suggested that, by adhesion, theseaggregates scavenged picoplankton-sized particles, which werethus effectively cleared from the medium. In contrast, Calanusfinmarchicus was not able to clear these particles in our experiments.Sedimentation velocities of 10 aggregates measured in vivo wereup to 1000 m day1, with an average of {small tilde}300m day1 (not including two aggegates with neutral buoyancy).Mean velocities measured for feces of C.finmarchicus, Calanushyperboreus and Thyssnoessa sp. were consider ably lower. Wesuggest that the sedimentation of L retroversa aggregates wasthe source of mucous flocs collected in sediment traps (Bathmannet al., Deep-Sea Res., 38,13411360,1991) and at the seafloor at 1200 m depth in the southern Norwegian Sea. This processmay be an important mediator of sedimentation to the deep sea,when these pteropods are present in surface waters in largeabundance. 相似文献
123.
Christian Kuberski Hartmut Scheibner Carola Steup Beate Diettrich Martin Luckner 《Phytochemistry》1984,23(7):1407-1412
Digitalis lanata strain VII from filament callus grew in small cell colonies in nutrient media with high auxin activity. Upon increasing the cytoki 相似文献
124.
When the acetogen Clostridium formicoaceticum was cultivated on mixtures of aromatic compounds (e.g., 4-hydroxybenzaldehyde plus vanillate), the oxidation of aromatic
aldehyde groups occurred more rapidly than did O-demethylation. Likewise, when fructose and 4-hydroxybenzaldehyde were simultaneously
provided as growth substrates, fructose was utilized only after the aromatic aldehyde group was oxidized to the carboxyl level.
Aromatic aldehyde oxidoreductase activity was constitutive (activities approximated 0.8 U mg–1), and when pulses of 4-hydroxybenzaldehyde were added during fructose-dependent growth, the rate at which fructose was utilized
decreased until 4-hydroxybenzaldehyde was consumed. Although 4-hydroxybenzaldehyde inhibited the capacity of cells to metabolize
fructose, lactate or gluconate were consumed simultaneously with 4-hydroxybenzaldehyde, and lactate or aromatic compounds
lacking an aldehyde group were utilized concomitantly with fructose. These results demonstrate that (1) aromatic aldehydes
can be utilized as cosubstrates and have negative effects on the homoacetogenic utilization of fructose by C. formicoaceticum, and (2) the consumption of certain substrates by this acetogen is not subject to catabolite repression by fructose.
Received: 14 May 1998 / Accepted: 7 August 1998 相似文献
125.
Henry W. Newman Carola Purdy Lowell Rantz F.C. Hill Jr. 《The Western journal of medicine》1958,89(6):387-389
Cultures on anaerobic medium were made of the spinal fluids of 27 patients with multiple sclerosis and 13 controls after the method described recently by Ichelson. Where Ichelson found organisms resembling spirochetes in 78 per cent of patients with multiple sclerosis, we found some form of what appeared to be a living micro-organism in 18.5 per cent. The control fluids were all sterile. The work requires confirmation and amplification. 相似文献
126.
127.
128.
Markus V. Heppt Thomas K. Eigentler Katharina C. Kähler Rudolf A. Herbst Daniela Göppner Thilo Gambichler Jens Ulrich Edgar Dippel Carmen Loquai Beatrice Schell Bastian Schilling Susanne G. Schäd Erwin S. Schultz Fanny Matheis Julia K. Tietze Carola Berking 《Cancer immunology, immunotherapy : CII》2016,65(8):951-959
129.
Evidence for Involvement of Gut-Associated Denitrifying Bacteria in Emission of Nitrous Oxide (N2O) by Earthworms Obtained from Garden and Forest Soils 下载免费PDF全文
Carola Matthies Anja Grießhammer Martina Schmittroth Harold L. Drake 《Applied microbiology》1999,65(8):3599-3604
Earthworms (Aporrectodea caliginosa, Lumbricus rubellus, and Octolasion lacteum) obtained from nitrous oxide (N2O)-emitting garden soils emitted 0.14 to 0.87 nmol of N2O h−1 g (fresh weight)−1 under in vivo conditions. L. rubellus obtained from N2O-emitting forest soil also emitted N2O, which confirmed previous observations (G. R. Karsten and H. L. Drake, Appl. Environ. Microbiol. 63:1878–1882, 1997). In contrast, commercially obtained Lumbricus terrestris did not emit N2O; however, such worms emitted N2O when they were fed (i.e., preincubated in) garden soils. A. caliginosa, L. rubellus, and O. lacteum substantially increased the rates of N2O emission of garden soil columns and microcosms. Extrapolation of the data to in situ conditions indicated that N2O emission by earthworms accounted for approximately 33% of the N2O emitted by garden soils. In vivo emission of N2O by earthworms obtained from both garden and forest soils was greatly stimulated when worms were moistened with sterile solutions of nitrate or nitrite; in contrast, ammonium did not stimulate in vivo emission of N2O. In the presence of nitrate, acetylene increased the N2O emission rates of earthworms; in contrast, in the presence of nitrite, acetylene had little or no effect on emission of N2O. In vivo emission of N2O decreased by 80% when earthworms were preincubated in soil supplemented with streptomycin and tetracycline. On a fresh weight basis, the rates of N2O emission of dissected earthworm gut sections were substantially higher than the rates of N2O emission of dissected worms lacking gut sections, indicating that N2O production occurred in the gut rather than on the worm surface. In contrast to living earthworms and gut sections that produced N2O under oxic conditions (i.e., in the presence of air), fresh casts (feces) from N2O-emitting earthworms produced N2O only under anoxic conditions. Collectively, these results indicate that gut-associated denitrifying bacteria are responsible for the in vivo emission of N2O by earthworms and contribute to the N2O that is emitted from certain terrestrial ecosystems. 相似文献
130.