全文获取类型
收费全文 | 27652篇 |
免费 | 15732篇 |
国内免费 | 2篇 |
出版年
2023年 | 27篇 |
2022年 | 127篇 |
2021年 | 449篇 |
2020年 | 2229篇 |
2019年 | 3763篇 |
2018年 | 3870篇 |
2017年 | 4145篇 |
2016年 | 4151篇 |
2015年 | 4077篇 |
2014年 | 3750篇 |
2013年 | 4194篇 |
2012年 | 1907篇 |
2011年 | 1631篇 |
2010年 | 3074篇 |
2009年 | 1847篇 |
2008年 | 750篇 |
2007年 | 370篇 |
2006年 | 346篇 |
2005年 | 384篇 |
2004年 | 347篇 |
2003年 | 337篇 |
2002年 | 330篇 |
2001年 | 322篇 |
2000年 | 250篇 |
1999年 | 193篇 |
1998年 | 43篇 |
1997年 | 39篇 |
1996年 | 30篇 |
1995年 | 31篇 |
1994年 | 34篇 |
1993年 | 22篇 |
1992年 | 28篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 30篇 |
1988年 | 15篇 |
1987年 | 15篇 |
1986年 | 21篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 14篇 |
1975年 | 7篇 |
1972年 | 11篇 |
1969年 | 7篇 |
1967年 | 7篇 |
1966年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
161.
Conjugational transfer of recombinant DNA in cultures and in soils: host range of Pseudomonas putida TOL plasmids. 总被引:7,自引:3,他引:4
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Recombinant TOL plasmid pWWO-EB62 allows Pseudomonas putida to grow on p-ethylbenzoate. This plasmid can be transferred to other microorganisms, and its catabolic functions for the metabolism of alkylbenzoates are expressed in a limited number of gram-negative bacteria, including members of pseudomonad rRNA group I and Escherichia coli. Transfer of the recombinant plasmid to Erwinia chrysanthemi was observed, but transconjugants failed to grow on alkylbenzoates because they lost catabolic functions. Pseudomonads belonging to rRNA groups II, III, and IV, Acinetobacter calcoaceticus, and Alcaligenes sp. could not act as recipients for TOL, either because the plasmid was not transferred or because it was not stably maintained. The frequency of transfer of pWWO-EB62 from P. putida as a donor to pseudomonads belonging to rRNA group I was on the order of 1 to 10(-2) transconjugant per recipient, while the frequency of intergeneric transfer ranged from 10(-3) to 10(-7) transconjugant per recipient. The profile of potential hosts was conserved when the donor bacterium was Escherichia coli or Erwinia chrysanthemi instead of P. putida. No intergeneric gene transfer of the recombinant TOL plasmid was observed in soils; however, intraspecies transfer did take place. Intraspecies transfer of TOL in soils was affected by the type of soil used, the initial inoculum size, and the presence of chemicals that could affect the survival of the donor or recipient bacteria. 相似文献
162.
163.
To assess the possibility that vasoactive intestinal polypeptide (VIP) plays a role in naturally occurring changes in prolactin secretion in ring doves, we used immunohistochemical techniques to measure VIP-like immunoreactivity in the brain as a function of stage of the reproductive cycle. Differences between parental and nonparental birds in VIP profiles were detected in the ventral portion of the infundibular region. More specifically, there is an increase in cell size and staining intensity in the ventral infundibulum of breeding birds compared to simultaneously processed tissue taken from control animals. In both sexes, an increase in size of VIP-like immunoreactive cells is detectable during courtship and early incubation, anticipating the increase in plasma prolactin levels. VIP cell size remains elevated from about Incubation Day 14 to Brooding Day 14, and a steady decrease is observed during the remaining posthatching period, as squab begin to feed independently. Compared to parents rearing one squab, those with two young have a prolonged interval of increased infundibular VIP immunoreactivity. Furthermore, doves with no previous experience of a breeding cycle exhibit prolonged VIP-like immunoreactivity compared to experienced parents, paralleling previously described differences between these groups in parental behavior. 相似文献
164.
Allen M. Schoffstall Robert J. Barto David L. Ramos 《Origins of life and evolution of the biosphere》1982,12(2):143-151
Nucleosides or deoxynucleosides were converted to a number of phosphorylated nucleotide and deoxynucleotide derivatives by ammonium or alkali dihydrogen phosphates in formamide. Conversions were smaller and slower at room temperature and greater and faster at elevated temperatures. Nucleotides afforded product mixtures similar to those obtained for nucleosides under the same conditions, indicating the occurrence of transphosphorylation processes. Products of reaction at elevated temperatures were cyclic nucleotides, nucleoside monophosphates, nucleoside diphosphates and cyclic nucleotide phosphates. The relative amounts of products formed were quite temperature dependent. Cyclic nucleotides were found to be in greatest abudance for reactions run at 125° or above. Relative yields of 2, 3 and 5 nucleotides and 3 and 5 deoxynucleotides from several experiments are reported. 5-Monophosphates were generally found to be present in larger quantities than 2 or 3 monophosphates. 2-Deoxyadenosine showed a preference for phosphorylation at the 3 position. Conclusions reached from mechanistic studies are that the phosphorylations are a series of equilibrium reactions, with cyclic nucleotides being formed irreversibly.Presented in part at the 3rd Northwest and 5th Rocky Mountain Joint Regional ACS Meeting of the American Chemical Society, Salt Lake City, Utah, June, 1980. 相似文献
165.
Two asparagine synthetases in Saccharomyces cerevisiae 总被引:3,自引:0,他引:3
In Saccharomyces cerevisiae L-asparagine auxotrophy, resulting from a lack of L-asparagine synthesis, needs simultaneous defects in two genes. This unusual situation is shown to result from the occurrence of two L-asparagine synthetases. The meaning of this duplication remains obscure. The properties of the two enzymes are remarkably similar: both have a molecular weight of 150,000 and they exhibit a slight repression and a similar inhibition by asparagine. Neither one is located in mitochondria and both are probably cytosolic. Their identification so far lies only in their behaviour on ion-exchange chromatography and in the encoding genes. 相似文献
166.
167.
During the process of degradation of the cell wall of the yeast form of Pullularia pullulans by the lytic system of Micromonospora chalcea samples were withdrawn at different times and observed under phase contrast and electron microscope. The progressive lysis of the walls reveals a fibrillar component inside the apparently amorphous wall. Freeze etched preparations of cells during the formation and regeneration of protoplasts show that the cellular membrane is split and this method allows the smooth external face of the membrane and other internal face covered by particles to be seen. The fact that the smooth face of the membrane is only visible during the preparation or the regeneration of protoplasts and very rarely when intact cells are fractured, suggests a strong adherence between cell wall and this external layer of the membrane. During the regeneration which takes place as in most of the yeasts and moulds, a special study of the extension of the cell wall is made and a possible mechanism for this extension of the regenerated cell wall is proposed. 相似文献
168.
ZAKβ antagonizes and ameliorates the cardiac hypertrophic and apoptotic effects induced by ZAKα
下载免费PDF全文
![点击此处可从《Cell biochemistry and function》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chien‐Yao Fu Wei‐Wen Kuo Tsung‐Jung Ho Su‐Ying Wen Ling‐Chun Lin Yan‐Shen Tseng Hui‐Chuan Hung Vijaya Padma Viswanadha Chih‐Yang Huang 《Cell biochemistry and function》2016,34(8):606-612
ZAK (sterile alpha motif and leucine zipper containing kinase AZK), a serine/threonine kinase with multiple biochemical functions, has been associated with various cell processes, including cell proliferation, cell differentiation, and cardiac hypertrophy. In our previous reports, we found that the activation of ZAKα signaling was critical for cardiac hypertrophy. In this study, we show that the expression of ZAKα activated apoptosis through both a FAS‐dependent pathway and a mitochondria‐dependent pathway by subsequently inducing caspase‐3. ZAKβ, an isoform of ZAKα, is dramatically expressed during cardiac hypertrophy and apoptosis. The interaction between ZAKα and ZAKβ was demonstrated here using immunoprecipitation. The results show that ZAKβ has the ability to diminish the expression level of ZAKα. These findings reveal an inherent regulatory role of ZAKβ to antagonize ZAKα and to subsequently downregulate the cardiac hypertrophy and apoptosis induced by ZAKα. 相似文献
169.
170.