全文获取类型
收费全文 | 2192篇 |
免费 | 174篇 |
出版年
2023年 | 7篇 |
2022年 | 23篇 |
2021年 | 37篇 |
2020年 | 27篇 |
2019年 | 38篇 |
2018年 | 41篇 |
2017年 | 39篇 |
2016年 | 71篇 |
2015年 | 100篇 |
2014年 | 97篇 |
2013年 | 149篇 |
2012年 | 169篇 |
2011年 | 166篇 |
2010年 | 100篇 |
2009年 | 83篇 |
2008年 | 123篇 |
2007年 | 142篇 |
2006年 | 137篇 |
2005年 | 133篇 |
2004年 | 108篇 |
2003年 | 121篇 |
2002年 | 105篇 |
2001年 | 23篇 |
2000年 | 30篇 |
1999年 | 22篇 |
1998年 | 21篇 |
1997年 | 16篇 |
1996年 | 21篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1971年 | 4篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有2366条查询结果,搜索用时 15 毫秒
1.
Maria V. Sergeeva Vadim V. Mozhaev Joseph O. Rich Yuri L. Khmelnitsky 《Biotechnology letters》2000,22(17):1419-1422
A novel biocatalytic reaction of transamidation of non-activated amides with amines is reported. Among 45 different lipolytic and proteolytic enzymes tested, only the lipase from Candida antarcticawas able to catalyze this reaction. The reaction proceeded with up to ca. 80% conversion in anhydrous methyl tert-butyl ether and worked with both N-substituted and unsubstituted amides. The biocatalytic transamidation is an equilibrium process and, therefore, higher conversions to the desired amide were achieved by using increased concentrations of the amine nucleophile. 相似文献
2.
Seabirds are affected by changes in the marine ecosystem. The influence of climatic factors on marine food webs can be reflected in long-term seabird population changes. We modelled the survival and recruitment of the Mediterranean storm petrel (Hydrobates pelagicus melitensis) using a 21-year mark-recapture dataset involving almost 5000 birds. We demonstrated a strong influence of prebreeding climatic conditions on recruitment age and of rainfall and breeding period conditions on juvenile survival. The results suggest that the juvenile survival rate of the Mediterranean subspecies may not be negatively affected by the predicted features of climate change, i.e., warmer summers and lower rainfall. Based on considerations of winter conditions in different parts of the Mediterranean, we were able to draw inferences about the wintering areas of the species for the first time. 相似文献
3.
Yoko Yamauchi Hikari Kimoto Xianyu Yang Sergey Filkin Yuri Utkin Tai Kubo 《Bioscience, biotechnology, and biochemistry》2016,80(1):158-161
Three-finger toxins (3FTxs) are one of the major components in snake venoms. In this study, we isolated a cDNA encoding a short-chain 3FTx, Pr-SNTX, from Pseudechis rossignolii. The amino acid sequence of Pr-SNTX is nearly identical to that of its ortholog in Pseudechis australis. Pr-SNTX protein inhibited muscle-type (α2βδε), but not neuronal α7 nicotinic acetylcholine receptor (nAChR) activity. 相似文献
4.
5.
M V Reznikov R Fidler P M Rubtsov K G Skriabin P M Chumakov V S Prasolov A A Baev 《Molekuliarnaia biologiia》1989,23(6):1692-1699
The new system for the transfer and expression of foreign genes based on retroviral vectors pPS-neo, conferring neomycin resistance was constructed. The BALB/c mouse cell lines producing highly active human growth hormone (more than 7 micrograms/ml into culture medium) were constructed using these vectors. An antibody column was used to purify the growth hormone from cell culture medium. Possibilities of producers to be applied for gene therapy are discussed. 相似文献
6.
A L Semeykina V P Skulachev M L Verkhovskaya E S Bulygina K M Chumakov 《European journal of biochemistry》1989,183(3):671-678
An alkalo- and halo-tolerant aerobic microorganism has been isolated which, according to microbiological analysis data and the ribosomal 5S RNA sequence, is a Bacillus similar, but not identical, to B. licheniformis and B. subtilis. The microorganism, called Bacillus FTU, proved to be resistant to the protonophorous uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). The fast growth of Bacillus FTU in the presence of CCCP was shown to require a high Na+ concentration in the medium. A procedure was developed to exhaust endogenous respiratory substrates in Bacillus FTU cells so that fast oxygen consumption by the cells was observed only when an exogenous respiratory substrate was added. The exhausted cells were found to oxidize ascorbate in the presence of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) in a cyanide-sensitive fashion. The ascorbate oxidation was coupled to the uphill Na+ extrusion which was stimulated by CCCP and a penetrating weak base, diethylamine, as well as by valinomycin with or without diethylamine. Operation of the Bacillus FTU terminal oxidase resulted in the generation of a delta psi which, in the Na+ medium, was slightly decreased by CCCP and strongly decreased by CCCP + diethylamine. In the K+ medium, CCCP discharged delta psi even without diethylamine. Ascorbate oxidation was competent in ATP synthesis which was resistant to CCCP in the Na+ medium and sensitive to CCCP in the K+ medium as if Na+- and H+-coupled oxidative phosphorylations were operative in the Na+ and K+ media, respectively. Inside-out subcellular vesicles of Bacillus FTU were found to be competent in the Na+ uptake supported by oxidation of ascorbate + TMPD or diaminodurene. CCCP or valinomycin + K+ increased the Na+ uptake very strongly. The process was completely inhibited by cyanide or monensin, the former, but not the latter, being inhibitory for respiration. The data obtained indicate that in Bacillus FTU there is not only H+-motive but also Na+-motive terminal oxidase activity. 相似文献
7.
8.
An extensive analysis of genomic DNA preparations from a number of normal and malignant tissues revealed BglII site polymorphism of the human p53 gene. Approximately 10% of p53 gene alleles were found to contain an additional BglII site localized in a region of intron I. This allelic form of p53 gene was also responsible for p53 protein having altered electrophoretic mobility. Molecular cloning and sequencing of both the alleles of p53 gene revealed a base-pair change in codon 72 causing arginine → proline substitution in the allele with the additional BglII site. Both variants of the p53 gene may occur in homozygous state and are therefore functional. 相似文献
9.
10.
Summary High yields of protoplasts were obtained from leaves of aseptically grown plants and calli originated from different explants, in several cultivars of Cajanus cajan L. The protoplasts divided to form cell clusters in modified KM 8p medium and developed to protocolonies after dilution with liquid Caboche's medium within three to four weeks of culture. The protocolonies proliferated to form green calli on solid Caboche's medium. No shoots or plants were obtained.Abbreviations BAP
6-benzylaminopurine
- NAA
-napthaleneacetic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- Kin
kinetin
- Zea
zeatin
- Adn S
adenine sulphate
- GA 3
gibberellic acid 相似文献