全文获取类型
收费全文 | 1319篇 |
免费 | 204篇 |
出版年
2021年 | 16篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 19篇 |
2015年 | 43篇 |
2014年 | 62篇 |
2013年 | 54篇 |
2012年 | 83篇 |
2011年 | 58篇 |
2010年 | 39篇 |
2009年 | 55篇 |
2008年 | 83篇 |
2007年 | 57篇 |
2006年 | 57篇 |
2005年 | 74篇 |
2004年 | 69篇 |
2003年 | 60篇 |
2002年 | 58篇 |
2001年 | 24篇 |
2000年 | 23篇 |
1999年 | 34篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 23篇 |
1993年 | 26篇 |
1992年 | 34篇 |
1991年 | 49篇 |
1990年 | 29篇 |
1989年 | 19篇 |
1988年 | 30篇 |
1987年 | 18篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 10篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 11篇 |
1973年 | 7篇 |
1972年 | 7篇 |
排序方式: 共有1523条查询结果,搜索用时 15 毫秒
1.
2.
Elisabeth Hansson Ingemar Jacobson Richard Venema Åke Sellström 《Journal of neurochemistry》1980,34(3):569-573
Abstract: The lipophilic cation [3 H]triphenylrnethylphosphonium bromide ([3 H]TPMP+ ) was investigated as a measure of the membrane potential of synaptosomes. Conditions under which [3 H]TPMP+ achieved an equilibrium distribution were tested. The toxicity of TPMP has been studied relative to its inhibitory effects on [3 H]y-aminobutyric acid ([3 H]GABA) transport. In some experiments the distribution of 86 RbZ+ and [3 H]TPMP+ was changed upon incubation in the presence of elevated levels of K+ , ouabain, or KCN, or at 0°C in a way that would be expected from the membrane potential. In normal incubation conditions a membrane potential of ∼−60 mv was calculated. 相似文献
3.
Heterologous gene expression in Lactococcus lactis subsp. lactis: synthesis, secretion, and processing of the Bacillus subtilis neutral protease 总被引:1,自引:0,他引:1
M van de Guchte J Kodde J M van der Vossen J Kok G Venema 《Applied and environmental microbiology》1990,56(9):2606-2611
The Bacillus subtilis nprE gene lacking its own promoter sequence was inserted in the lactococcal expression vector pMG36e. Upon introduction of the recombinant plasmid into Lactococcus lactis subsp. lactis strain MG1363, neutral protease activity could be visualized by the appearance of large clearing zones around colonies grown on milk agar plates. By measuring the activities of the neutral protease and the intracellular enzyme lactate dehydrogenase in culture supernatants and cell fractions, it was demonstrated that the neutral protease was actively secreted into the growth medium. This was corroborated by using the Western blot (immunoblot) technique, which showed the presence of the mature form of the neutral protease in the culture supernatant. On the basis of these results, it is concluded that the B. subtilis neutral protease gene was expressed in L. lactis and that the gene product was secreted into the growth medium and was apparently correctly processed to produced a biologically active protein. The secretion of this particular enzyme may be helpful in achieving accelerated cheese ripening. 相似文献
4.
Automated determinations of 5-hydroxytryptamine and its main metabolite, 5-hydroxyindoleacetic acid, have been described (Technicon autoanalyzer). The determinations are based on an extraction procedure from deproteinized tissue extracts or cerebrospinal fluid by means of butanolheptane mixtures. The indoles are transferred from the organic phase to a water phase and determined fluormetrically with the cysteine-o-phthaldialdehyde method. The method is highly sensitive: solutions containing 1 ng/ml can be reproducibly determined. Twenty samples per hour can be passed through the system. The determination of both 5-hydroxyindoles is performed with the same manifold. 相似文献
5.
Chris J. van Koppen Marcel W. Hermanussen Kiek N. Verrijp Jaap F. Rodrigues de Miranda Arie J. Beld Jan-Willem J. Lammers Cees A. M. van Ginneken 《Life sciences》1987,40(26):2561-2570
Specific binding of [125I]-(−)-cyanopindolol to human tracheal smooth muscle membranes was saturable, stereo-selective and of high affinity (Kd=5.3±0.9 pmol/l and RT=78±7fmol/g tissue). The β1-selective antagonists atenolol and LK 203-030 inhibited specific [125I]-(−)-cyanopindolol binding according to a one binding site model with low affinity in nearly all subjects, pointing to a homogeneous β2-adrenoceptor population. In one subject using LK 203-030 a small β-adrenoceptor subpopulation could be demonstrated. The beta-mimetics isoprenaline, fenoterol, salbutamol and terbutaline recognized high and low affinity agonist binding sites. Isoprenaline's pKH- and pKL- values for the high and low affinity sites were 8.0±0.2 and 5.9±0.3 respectively. In functional experiments isoprenaline relaxed tracheal smooth muscle strips having intrinsic tone with a pD2-value of 6.63±0.19. 相似文献
6.
Construction of a lactococcal expression vector: expression of hen egg white lysozyme in Lactococcus lactis subsp. lactis. 总被引:10,自引:5,他引:5 下载免费PDF全文
A pair of vectors for expression of heterologous genes in Lactococcus lactis was constructed. In addition to an origin of replication that has a broad host range, these vectors contain a multiple cloning site flanked by gene expression signals originating from L. lactis subsp. cremoris Wg2. The two vectors, about 3.7 kilobase pairs in size, differ only in the type of antibiotic resistance they confer to their hosts. pMG36 carries a kanamycin resistance marker, which was replaced by an erythromycin resistance marker in pMG36e. As an example of the use of these vectors, the hen egg white lysozyme-coding sequence was inserted. A fusion protein of the expected size was detected in a transformed L. lactis subsp. lactis strain by using Western blotting (immunoblotting). 相似文献
7.
Development of a beta-galactosidase alpha-complementation system for molecular cloning in Bacillus subtilis 总被引:7,自引:0,他引:7
A versatile beta-galactosidase alpha-complementation system for Bacillus subtilis was developed, which can be used for molecular cloning in this Gram+ organism. The cloning system, which is based on the highly efficient host-vector system 6GM-pHP13, offers several advantages over previously described systems: (1) convenient direct selection of recombinants; (2) the cloning of large heterologous DNA fragments with high efficiency; and (3) the availability of six unique target sites: SphI, NdeI, NheI, BamHI, SmaI and EcoRI. 相似文献
8.
J Kok D Hill A J Haandrikman M J de Reuver H Laan G Venema 《Applied and environmental microbiology》1988,54(1):239-244
9.
Cloning and characterization of the tetracycline resistance determinant of and several promoters from within the conjugative transposon Tn919 总被引:7,自引:0,他引:7
Tn919 is a 15- to 16-kilobase (kb) tetracycline resistance conjugative transposon that was originally isolated from Streptococcus sanguis FC1. The tetracycline resistance determinant (tet) was found on a 4.2-kb HindII fragment by in vitro deletion analysis. This fragment was subcloned to a pWV01 origin capable of directing replication in Escherichia coli, Bacillus subtilis, and Streptococcus lactis, and expression was observed in all three genera. In all cases, expression was weaker when only the 4.2-kb cloned fragment rather than the full transposon was present. The resistance gene is of the streptococcal tetM class and codes for a protein of approximately 70 kilodaltons. The restriction map resembles that of the tetM gene of Tn1545 (P. Martin, P. Trieu-Cuot, and P. Courvalin, Nucleic Acids Res. 14:7047-7058, 1986), which codes for a protein of 72.5 kilodaltons. A number of transposon-derived promoter-bearing fragments were also cloned and sequenced. These closely resemble the consensus sequence of E. coli and B. subtilis promoters. Fusion experiments with a truncated lacZ gene indicate the possibility of an open reading frame for one of the promoters. 相似文献
10.
Plasmid deletion formation in Bacillus subtilis 总被引:4,自引:0,他引:4