全文获取类型
收费全文 | 4115篇 |
免费 | 386篇 |
国内免费 | 1篇 |
出版年
2022年 | 31篇 |
2021年 | 66篇 |
2020年 | 37篇 |
2019年 | 35篇 |
2018年 | 70篇 |
2017年 | 44篇 |
2016年 | 103篇 |
2015年 | 177篇 |
2014年 | 200篇 |
2013年 | 241篇 |
2012年 | 322篇 |
2011年 | 309篇 |
2010年 | 202篇 |
2009年 | 170篇 |
2008年 | 242篇 |
2007年 | 239篇 |
2006年 | 192篇 |
2005年 | 188篇 |
2004年 | 188篇 |
2003年 | 168篇 |
2002年 | 160篇 |
2001年 | 93篇 |
2000年 | 66篇 |
1999年 | 55篇 |
1998年 | 58篇 |
1997年 | 47篇 |
1996年 | 29篇 |
1995年 | 37篇 |
1994年 | 33篇 |
1993年 | 31篇 |
1992年 | 39篇 |
1991年 | 32篇 |
1990年 | 27篇 |
1989年 | 24篇 |
1988年 | 25篇 |
1987年 | 32篇 |
1986年 | 22篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 31篇 |
1982年 | 27篇 |
1981年 | 23篇 |
1980年 | 18篇 |
1979年 | 20篇 |
1978年 | 18篇 |
1975年 | 23篇 |
1974年 | 18篇 |
1973年 | 19篇 |
1971年 | 24篇 |
1969年 | 23篇 |
排序方式: 共有4502条查询结果,搜索用时 31 毫秒
41.
Dietrich Neumann 《Hydrobiologia》1961,17(1-2):133-151
Zusammenfassung Die Arbeitsweise und die Leistungen der Rhipidoglossenradula von Theodoxus fluviatilis werden durch die kräftigen 4. Zwischenzähne und die Randbürstenzähne bestimmt. Die 4. Zwischenzähne lockern im wesentlichen die dem Fre\grund anhaftenden oder aufliegenden ein- bis wenigzelligen Algen (Diatomeen, chlorococcale und konjugate Grünalgen), die Randzähne fegen das gelockerte Nahrungsgut quantitativ zusammen. Fädige Grünalgen (z. B. Cladophorales) und Gewebeteile höherer Pflanzen werden nicht abgebissen bzw. abgeschabt.Die Diatomeen werden nur verdaut, wenn die Kieselschalen bereits bei der Nahrungsaufnahme mechanisch zerkleinert werden. Diese Zerkleinerung erfolgt allein auf einem Substrat mit rauher Oberfläche; sie wird durch die während des Bisses zwischen 4. Zwischenzähnen und Substrat auftretenden Reibungskräfte erzielt.
Theodoxus wurde bei refiner Diatomeenernährung über mehrere Generationen gezüchtet. Tierisches Eiwei\ ist als Zusatzkost nicht erforderlich. Mit besonderen Hilfsma\nahmen kann Theodoxus im Laboratorium auch mit Cyanophyceen oder besonders mit Flagellaten (Chlamydomonas), die den Schnecken an den im Freiland besiedelten Standorten nicht zur Verfügung stehen, ernährt werden.Sämtliche Grünalgen mit stärkerer Cellulosewandung (Chlorococcales, Conjugatae) sind unverdaulich. Die Unverdaulichlichkeit beruht vermutlich auf einem Fehlen von Cellulasen im Verdauungstraktus. Die Zellmembranen und extrazellularen Scheiden der Cyanophyceen, die aus Hemicellulosen und Pektinen aufgebaut sind, werden im Magen aufgelöst.
Theodoxus ist ein reiner Diatomeenfresser. Die ökologische Einnischung in die litorale Steinregion ist vorwiegend ernährungs-physiologisch begründet und erklärt das Vorkommen in Flie\gewassern und an Brandungsufern stehender Sü\gewässer sowie der Ostsee. 相似文献
42.
The fine structure of Azotobacter vinelandii has been studied by means of electron microscopy of ultrathin sections made of the encysting and germinating cells. The organisms were fixed with KMnO4 and embedded in epoxy resin. On an encystment medium the rod-shaped bacteria begin to assume an almost spherical form and then bark-like exine appears in 1½ to 2 days. The exine thickens and an electron permeable intine forms between it and the shrinking cell body. In 5 days the intine makes up more than half of the cyst volume and begins to show a definite two-layered structure. Meanwhile the peripheral bodies, which may be extensions of the cell membrane of the vegetative cell, disappear as the encystment progresses. The cell wall and membrane of the vegetative cell remain demonstrable as the confining structure of the shrinking central body of the mature cyst. In this central body lipoidal globules appear together with aggregations of nuclear material. Cyst germination begins with an increase in the size of the central body at the expense of the intine. The nuclear aggregations become more diffuse and the lipoidal globules disappear. The exine may be pushed outward and the bark-like fragments separate as the emerging vegetative cell develops. Invagination of the cell wall and membrane may occur at this stage leading to cell division. Empty exines remain as horseshoe-shaped structures. 相似文献
43.
44.
Dr. Dietrich Neumann 《Zoomorphology》1959,48(4):349-411
Ohne ZusammenfassungMit Unterstützung der Deutschen Forschungsgemeineshaft. 相似文献
45.
A wheat basic protein (WBP) was purified to homogeneity from wheat germ by a protocol involving extraction, centrifugation, batchwise elution from carboxymethylcellulose (CM-52), acidification with trifluoroacetic acid, neutralization and HPLC on a SP5PW cation exchange column. WBP is a 10 kDa protein and is phosphorylated on serine residues by wheat germ Ca(2+)-dependent protein kinase (CDPK). [32P]phosphoWBP exactly comigrates with WBP on SDS-PAGE. WBP does not inhibit either wheat germ CDPK or calmodulin-dependent myosin light chain kinase. Apart from histone H1, WBP is the best endogenous substrate yet found for wheat embryo CDPK. A 12 kDa pine basic protein (PBP) was purified to homogeneity from seeds of stone pine (Pinus pinea L.) by a simple procedure involving batchwise elution from carboxymethylcellulose and cation exchange HPLC. PBP is also a good substrate for CDPK and is phosphorylated on Ser residues. N-terminal sequencing of WBP and PBP revealed that these proteins are homologous to a family of small basic plant proteins having a phospholipid transfer function. 相似文献
46.
U. Gartenbach-Scharrer S. Habib K. -H. Neumann 《Plant Cell, Tissue and Organ Culture》1990,22(1):27-35
Freshly isolated explants of the secondary phloem of carrot roots were exposed to 14C-leucine for various periods from t0—to 18 h and the 14C labelling of protein was studied by 2-dimensional PAGE followed by fluorograph. The labelling pattern of proteins indicated a sequential activation of synthesis of about 130 proteins during the 18 h experimental period prior to the onset of cell division activity.Abbreviations IAA
indole acetic acid
- 2iP
2-isopentenyladenine
- PVP
polyvinylpyrrolidone
- CBB
Coomassie brilliant blue
- RuBPCase
ribulosebisphosphate carboxylase
- LSC
liquid scintillation counter
- spec.act.
specific radioactivity
- u.l.
uniformly labelled 相似文献
47.
48.
Yvonne E. G. Eskildsen-Helmond Han A. A. Van Heugten Jos M. J. Lamers 《Molecular and cellular biochemistry》1996,157(1-2):39-48
There is now clear evidence that receptor-dependent phospholipase D is present in myocardium. This novel signal transduction pathway provides an alternative source of 1,2-diacylglycerol, which activates isoforms of protein kinase C. The members of the protein kinase C family respond differently to various combinations of Ca2+, phosphatidylserine, molecular species of 1,2-diacylglycerol and other membrane phospholipid metabolites including free fatty acids. Protein kinase C isozymes are responsible for phosphorylation of specific cardiac substrate proteins that may be involved in regulation of cardiac contractility, hypertrophic growth, gene expression, ischemic preconditioning and electrophysiological changes. The initial product of phospholipase D, phosphatidic acid, may also have a second messenger role. As in other tissues, the question how the activity of phospholipase D is controlled by agonists in myocardium is controversial. Agonists, such as endothelin-1, atrial natriuretic factor and angiotensin 11 that are shown to activate phospholipase D, also potently stimulate phospholipase C- in myocardium. PMA stimulation of protein kinase C inactivates phospholipase C and strongly activates phospholipase D and this is probably a major mechanism by which agonists that promote phosphatidyl-4,5-bisphosphate hydrolysis secondary activate phosphatidylcholine-hydrolysis. On the other hand, one group has postulated that formation of phosphatidic acid secondary activates phosphatidyl-4,5-bisphosphate hydrolysis in cardiomyocytes. Whether GTP-binding proteins directly control phospholipase D is not clearly established in myocardium. Phospholipase D activation may also be mediated by an increase in cytosolic free Ca2+ or by tyrosine-phosphorylation. 相似文献
49.
Abnormal bone growth and selective translational regulation in basic fibroblast growth factor (FGF-2) transgenic mice. 总被引:15,自引:2,他引:13
下载免费PDF全文
![点击此处可从《Molecular biology of the cell》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J D Coffin R Z Florkiewicz J Neumann T Mort-Hopkins G W Dorn nd P Lightfoot R German P N Howles A Kier B A O'Toole et al. 《Molecular biology of the cell》1995,6(12):1861-1873
Basic fibroblast growth factor (FGF-2) is a pleiotropic growth factor detected in many different cells and tissues. Normally synthesized at low levels, FGF-2 is elevated in various pathologies, most notably in cancer and injury repair. To investigate the effects of elevated FGF-2, the human full-length cDNA was expressed in transgenic mice under control of a phosphoglycerate kinase promoter. Overexpression of FGF-2 caused a variety of skeletal malformations including shortening and flattening of long bones and moderate macrocephaly. Comparison by Western blot of FGF-2 transgenic mice to nontransgenic littermates showed expression of human FGF-2 protein in all major organs and tissues examined including brain, heart, lung, liver, kidney, spleen, and skeletal muscle; however, different molar ratios of FGF-2 protein isoforms were observed between different organs and tissues. Some tissues preferentially synthesize larger isoforms of FGF-2 while other tissues produce predominantly smaller 18-kDa FGF-2. Translation of the high molecular weight isoforms initiates from unconventional CUG codons and translation of the 18-kDa isoform initiates from an AUG codon in the FGF-2 mRNA. Thus the Western blot data from the FGF-2 transgenic mice suggest that tissue-specific expression of FGF-2 isoforms is regulated translationally. 相似文献
50.
C Kaltschmidt B Kaltschmidt H Neumann H Wekerle P A Baeuerle 《Molecular and cellular biology》1994,14(6):3981-3992