全文获取类型
收费全文 | 1667篇 |
免费 | 220篇 |
国内免费 | 562篇 |
出版年
2024年 | 13篇 |
2023年 | 32篇 |
2022年 | 49篇 |
2021年 | 81篇 |
2020年 | 67篇 |
2019年 | 79篇 |
2018年 | 52篇 |
2017年 | 58篇 |
2016年 | 46篇 |
2015年 | 88篇 |
2014年 | 110篇 |
2013年 | 101篇 |
2012年 | 170篇 |
2011年 | 142篇 |
2010年 | 98篇 |
2009年 | 113篇 |
2008年 | 134篇 |
2007年 | 124篇 |
2006年 | 113篇 |
2005年 | 93篇 |
2004年 | 82篇 |
2003年 | 70篇 |
2002年 | 70篇 |
2001年 | 63篇 |
2000年 | 60篇 |
1999年 | 39篇 |
1998年 | 32篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 23篇 |
1991年 | 30篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 14篇 |
1987年 | 20篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 5篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有2449条查询结果,搜索用时 299 毫秒
21.
Jens Chr. Madsen Ole Winneche Sørensen Poul Sørensen Flemming M. Poulsen 《Journal of biomolecular NMR》1993,3(2):239-244
Summary NMR pulse sequences for measuring coupling constants in 13C, 15N-labeled proteins are presented. These pulse sequences represent improvements over earlier experiments with respect to resolution and number of radiofrequency pulses. The experiments are useful for measuring JNH
, JNCO, JNC
, JH
N
CO and JH
N
H
. Applications to chymotrypsin inhibitor 2 (CI-2) are shown. 相似文献
22.
Etlingera kenyalang is described from southern Sarawak. Ecological notes are given including a possible pollinator and seed dispersers. The Iban ethnobotany of the species is discussed; the shoots and fruits are edible and the leaves are used ritually during the Gawai Kenyalang (Hornbill Festival). 相似文献
23.
24.
The use of bulk segregant analysis to identify a RAPD marker linked to leaf rust resistance in barley 总被引:4,自引:0,他引:4
D. M. E. Poulsen R. J. Henry R. P. Johnston J. A. G. Irwin R. G. Rees 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(2):270-273
An F2 population from a cross between barley accession Q21861 and the Australian barley variety Galleon was used to develop RAPD markers for resistance to barley leaf rust (Puccinia hordei). Resistant and susceptible DNA bulks were constructed following the classification of F2 plants by leaf rust infection type. Bulked segregant analysis was then used to identify a 2.7-kb marker, designated OU022700 and located approximately 12cM from RphQ, a leaf rust resistance gene in Q21861. The marker was generated by PCR with the oligonucleotide primer OPU-02 (Operon). Infection types of F3 progeny were used to confirm assignment of F2 genotypes. OU022700 was shown, retrospectively, to be useful in the identification of individual F2 plants that had been originally misclassified as having susceptible infection types. Both the RAPD marker and RphQ will be potentially useful in the development of new barley cultivars. 相似文献
25.
J J Holst J Fahrenkrug S Knuhtsen S L Jensen S S Poulsen O V Nielsen 《Regulatory peptides》1984,8(3):245-259
Vasoactive intestinal polypeptide (VIP) in the pig pancreas is localized to nerves, many of which travel along the pancreatic ducts. VIP stimulates pancreatic fluid and bicarbonate secretion like secretin. Electrical vagal stimulation in the pig causes an atropine-resistant profuse secretion of bicarbonate-rich pancreatic juice. In an isolated perfused preparation of the pig pancreas with intact vagal nerve supply, electrical vagal stimulation caused an atropine-resistant release of VIP, which accurately parallelled the exocrine secretion of juice and bicarbonate. Perfusion of the pancreas with a potent VIP-antiserum inhibited the effect of vagal stimulation on the exocrine secretion. It is concluded, that VIP is responsible for (at least part of) the neurally controlled fluid and bicarbonate secretion from the pig pancreas. 相似文献
26.
D T Minkel K Poulsen S Wielgus C F Shaw rd D H Petering 《The Biochemical journal》1980,191(2):475-485
It is demonstrated that the distribution of metals among the Sephadex G-75 fractions of rat liver and horse kidney supernatant is altered by exposure to oxidizing conditions. In particular, the metals bound to metallothionein are displaced into high-molecular-weight fractions and, to a lesser extent, into the low-molecular-weight forms, under aerobic conditions. In this process, metallothionein zinc is much more labile than cadmium. An appreciable proportion of the thionein is also found in the high-molecular-weight fractions and can be recovered along with the metals by treatment with mercaptoethanol. This result shows that the distributions obtained aerobically with large cadmium content in the high-molecular-weight fractions are an artefact due to metallothionein oxidation and suggests that 'spillage' of metals such as cadmium may be due in large part to oxidative processes rather than saturation effects. Evidence is presented that disulphide-bond formation occurs as thionein becomes bound in the high-molecular-weight region and that chemical reduction is necessary to restore its normal elution behaviour. Mercaptoethanol added to the homogenates maintains the reducing conditions normally found in the cellular milieu and prevents the oxidation of the metallothionein redistribution of the metals during isolation. Under these conditions the rat liver metallothionein isolated from animals exposed to chronic low concentrations of cadmium in drinking water contains appreciable quantities of copper as well as zinc and contains much of the zinc that is present in horse kidney supernatants. Metallothionein can also be extracted from a 40 000g pellet after sonication of the pellet. Thus careful analytical studies of the sites of cadmium deposition in rat liver indicate that greater than 95% is bound to metallothionein. 相似文献
27.
Summary A large family is reported in which mental retardation associated with the fragile site at Xq28 was found. Three normal males seemed to have transmitted the trait through their daughters to affected grandchildren.A total of 19 family members were investigated cytogenetically. Mentally retarded males showed macroorchidism and the fragile X. Three mentally retarded females were found, with the fragile X in a high percentage of cells; in contrast, the obligate carriers showed no or only few cells with the fragile X. 相似文献
28.
正常大鼠肾脏细胞溶酶体膜的构成蛋白 总被引:1,自引:0,他引:1
溶酶体是细胞内对其吞噬之物质溶解及消化之主要场所,同时也是细胞自噬作用的主要细胞器。为了进一步了解此细胞器的功能与结构,我们采用免疫荧光标记法,通过5种针对大鼠肝细胞溶酶体膜蛋白的特异性单克隆抗体,对大鼠正常肾脏细胞溶酶体膜蛋白进行了标记,并通过NH_4Cl溶液对溶酶体作了膜膨胀处理,结果显示:(1)细胞内溶酶体膜蛋白是由多种蛋白所构成,其各种蛋白的含量是不同的;(2)所有溶酶体膜蛋白均表达于该细胞器之表面;(3)NH_4Cl溶液能有效地使溶酶体扩张,这将有和于进一步研究溶酶体的结构。 相似文献
29.
The chromosomal location of the porcine gene for glucose phosphate isomerase (GPI) was previously mapped to 6p 12----6q21 in the pig karyotype. The replication patterns and morphology of this chromosome are very similar to those of chromosome 14 in the rabbit karyotype. With combined in situ hybridization and RBG-band induction it was demonstrated that the porcine GPI-probe hybridized most frequently to 14p11----14q12 in the rabbit karyotype, indicating a close relationship between morphology, replication pattern and gene location. 相似文献
30.
Refinement of the three-dimensional solution structure of barley serine proteinase inhibitor 2 and comparison with the structures in crystals. 总被引:6,自引:0,他引:6
S Ludvigsen H Y Shen M Kjaer J C Madsen F M Poulsen 《Journal of molecular biology》1991,222(3):621-635
The three-dimensional structure of barley serine proteinase inhibitor, CI-2, has been determined using nuclear magnetic resonance spectroscopy. The present structure determination is a refinement of the structure previously determined by us, using in the present case stereo-specific assignments, and a virtually complete set of assignments of the two-dimensional nuclear Overhauser spectrum. The structure determination is based on the identification of more than 1300 nuclear Overhauser effects, of which 961 were used in the structure calculation as distance restraints, and on 94 dihedral angle restraints, of which 31 are for chi 1 angles in defined chiral centers. These have been used to calculate a series of 20 three-dimensional structures using a combination of distance geometry, simulated annealing and restrained molecular dynamics. Each of the 20 structures was in agreement within less than 0.5 A of each of the distance restraints and with all dihedral angle restraints. When compared to the geometric average structure of the 20 refined structures the root-mean-square differences for the backbone atoms were 0.8 (+/- 0.2) A and for all atoms were 1.6 (+/- 0.2) A. By comparison, the values obtained for the structures determined previously were 1.4 (+/- 0.2) A and 2.1 (+/- 0.1) A, respectively. The structures were also compared to the structure determined in the crystalline state by X-ray diffraction showing root-mean-square differences of 1.6 (+/- 0.2) A and 2.8 (+/- 0.2) A for the backbone and all atoms, respectively. Common features of the solution structure and the two crystal structures are the four-stranded beta-structure, composed of a pair of parallel strands, and three pairs of antiparallel beta-strands flanked on one side by a 12-residue alpha-helix and on the other side by a loop containing the serine proteinase binding site. The new analysis of the structure has revealed an additional pair of antiparallel beta-strands, consisting of residues 65 to 67 and 81 to 83, that was not seen in either of the crystal structures or the previous solution structure. Identification of this was based on nuclear magnetic resonance evidence for the hydrogen bond (67HN to 81CO) not reported previously. Also the presence of a bifurcated hydrogen bond involving Phe69 CO and HN atoms of Ala77 and Gln78 was observed in solution but not in crystals. Minor differences between the two structures were observed in the phi-angles of residues Met59 and Glu60 in the inhibitory site. 相似文献