全文获取类型
收费全文 | 3948篇 |
免费 | 411篇 |
国内免费 | 1篇 |
出版年
2022年 | 26篇 |
2021年 | 54篇 |
2019年 | 42篇 |
2018年 | 39篇 |
2017年 | 47篇 |
2016年 | 72篇 |
2015年 | 131篇 |
2014年 | 160篇 |
2013年 | 204篇 |
2012年 | 240篇 |
2011年 | 230篇 |
2010年 | 151篇 |
2009年 | 120篇 |
2008年 | 195篇 |
2007年 | 193篇 |
2006年 | 186篇 |
2005年 | 183篇 |
2004年 | 164篇 |
2003年 | 151篇 |
2002年 | 149篇 |
2001年 | 92篇 |
2000年 | 97篇 |
1999年 | 89篇 |
1998年 | 63篇 |
1997年 | 42篇 |
1996年 | 49篇 |
1995年 | 26篇 |
1994年 | 34篇 |
1993年 | 30篇 |
1992年 | 57篇 |
1991年 | 47篇 |
1990年 | 43篇 |
1989年 | 50篇 |
1988年 | 58篇 |
1987年 | 47篇 |
1986年 | 49篇 |
1985年 | 63篇 |
1984年 | 36篇 |
1983年 | 25篇 |
1982年 | 36篇 |
1981年 | 29篇 |
1980年 | 27篇 |
1979年 | 43篇 |
1978年 | 33篇 |
1977年 | 46篇 |
1976年 | 31篇 |
1974年 | 37篇 |
1973年 | 38篇 |
1972年 | 33篇 |
1970年 | 27篇 |
排序方式: 共有4360条查询结果,搜索用时 15 毫秒
121.
122.
The yeastSaccharomyces cerevisiae X2180-1A (wild) and its mutants X2180-1A-4 (mnn 1) and X2180-1A-5 (mnn 2) defective in mannan biosynthesis were used as enzyme sources to catalyzein vitro mannosyl transfer from GDP-[14C-U]-mannose to endogenous glycoproteins as well as to exogenous, low-molecular weight acceptors. While the enzyme preparation
from the wild strain exhibited all mannosyl transferase activities involved in mannan biosynthesis by catalyzing the synthesis
of characteristic mannoprotein, the enzyme frommnn 1 mutant failed to catalyze the synthesis of α(1→3) mannoside linkages both with endogenous as well as with exogenous acceptors.
The enzyme preparation from themnn 2 mutant catalyzed the formation of mannoprotein very similar to that obtained with the enzyme from the wild strain. The
most important difference was the formation of a higher number of unsubstituted mannosyl units in the α(1→ 6) linked mannan
backbone. The observed results support the hypothesis that in themnn 1 the mutation has altered the structural gene involved in biosynthesis of an α(1→3) mannosyl transferase catalyzing the addition
of α(1→3) linked mannosyl units to α(1→2) linked mannotrioses in the polysaccharide side chains and in the oligosaccharides
attached to serine and/or threonine in the protein part of mannan molecule. Themnn 2 mutant represents most probably a kind of regulatory mutation where the activity of an α(1→2) mannosyl transferase adding
the mannosyl units directly to α(1→6) linked backbone in the outer region of polysacoharide part of yeast mannan is repressedin vivo but becomes significantin vitro. 相似文献
123.
Effect of gibberellic Acid on crown gall tumor induction in aging primary pinto bean leaves 下载免费PDF全文
Gibberellic acid was tested for its effect on tumor induction by Agrobacterium tumefaciens in primary pinto bean (Phaseolus vulgaris) leaves in various stages of development. The hormone was found to promote tumor induction in partially aged leaves but did not effect tumor induction in very young leaves or in fully matured leaves. It is suggested that the natural loss of susceptibility to tumor induction in maturing pinto bean leaves is associated with a concomitant loss of endogenous gibberellins and/or a sensitivity to gibberellins. 相似文献
124.
125.
Stéphanie Rollero Audrey Bloem Anne Ortiz-Julien Florian F. Bauer Carole Camarasa Benoit Divol 《Environmental microbiology》2019,21(11):4076-4091
In grape must, nitrogen is available as a complex mixture of various compounds (ammonium and amino acids). Wine yeasts assimilate these multiple sources in order to suitably fulfil their anabolic requirements during alcoholic fermentation. Nevertheless, the order of uptake and the intracellular fate of these sources are likely to differ between strains and species. Using a two-pronged strategy of isotopic filiation and RNA sequencing, the metabolic network of nitrogen utilization and its regulation in Kluyveromyces marxianus were described, in comparison with those of Saccharomyces cerevisiae. The data highlighted differences in the assimilation of ammonium and arginine between the two species. The data also revealed that the metabolic fate of certain nitrogen sources differed, thereby resulting in the production of various amounts of key wine aroma compounds. These observations were corroborated by the gene expression analysis. 相似文献
126.
SMS 201-995: a very potent and selective octapeptide analogue of somatostatin with prolonged action 总被引:26,自引:0,他引:26
W Bauer U Briner W Doepfner R Haller R Huguenin P Marbach T J Petcher 《Life sciences》1982,31(11):1133-1140
Stepwise modification of a conformationally stabilised analogue of the fragment of somatostatin which had been thought to be essential biologically active moiety has enabled us to synthesise the analogue H-(D) Phe-Cys-Phe-(D) Trp-Lys-Thr-Cys-Thr(ol) code-named SMS 201-995, which in vitro is three times more potent than the native hormone in inhibiting the secretion of growth hormone, which is highly resistant to degradation by pure enzymes and by tissue homogenates, which in vivo in rat and rhesus monkey is (depending on test system) at least 20 times more active than somatostatin, which is much longer acting, and which moreover in both species is much more selective in inhibiting the secretion of growth hormone than that of insulin. The compound is active by several routes of administration including the oral, is well tolerated both in laboratory animals and in man, and is currently undergoing preliminary clinical trial. 相似文献
127.
Roman Bauer 《Biological cybernetics》1980,37(1):19-24
Responses from neurons of the vestibular nuclei were recorded in N2O-anaesthetized cats. Most neurons in the rostral parts of the nuclei responded to bimodal visual-vestibular stimulation, following a trapezoidal velocity profile. Both combinations of the two stimuli were tested: rotation of the animal with stationary visual field and rotation with overtaking visual field, i.e. the visual pattern running in the same direction as the turntable with twice the velocity. Some correlation of physiological data with results in corresponding psychophysical experiments were found. As a possible biological function of visual-vestibular convergence a phylogenetic solution for discrimination of body and outer world movement is discussed. 相似文献
128.
129.
130.
Katharina Gryksa Laura Mittmann Angelika Bauer Daniel Peterlik Peter J. Flor Nicole Uschold‐Schmidt Oliver J. Bosch 《Genes, Brain & Behavior》2020,19(1)
The group III metabotropic glutamate receptor subtype 7 (mGlu7) is an important regulator of glutamatergic and GABAergic neurotransmission and known to mediate emotionality and male social behavior. However, a possible regulatory role in maternal behavior remains unknown to date. Adequate expression of maternal behavior is essential for successful rearing and healthy development of the young. By understanding genetic and neural mechanisms underlying this important prosocial behavior, we gain valuable insights into possible dysregulations. Using genetic ablation as well as pharmacological modulation, we studied various parameters of maternal behavior in two different mouse strains under the influence of mGlu7. We can clearly show a regulatory role of mGlu7 in maternal behavior. Naïve virgin female C57BL/6 mGlu7 knockout mice showed more often nursing postures and less spontaneous maternal aggression compared to their heterozygous and wildtype littermates. In lactating C57BL/6 wildtype mice, acute central activation of mGlu7 by the selective agonist AMN082 reduced arched back nursing and accelerated pup retrieval without affecting maternal aggression. In addition, in lactating CD1 wildtype mice the selective mGlu7 antagonist XAP044 increased both pup retrieval and maternal aggression. With respect to receptor expression levels, mGlu7 mRNA expression was higher in lactating vs virgin C57BL/6 mice in the prefrontal cortex, but not hypothalamus or hippocampus. In conclusion, these findings highlight a significant role of the mGlu7 receptor subtype in mediating maternal behavior in mice. Region‐dependent studies are warranted to further extend our knowledge on the specific function of the brain glutamate system in maternal behavior. 相似文献