全文获取类型
收费全文 | 3009篇 |
免费 | 217篇 |
专业分类
3226篇 |
出版年
2023年 | 11篇 |
2022年 | 22篇 |
2021年 | 45篇 |
2020年 | 22篇 |
2019年 | 35篇 |
2018年 | 49篇 |
2017年 | 27篇 |
2016年 | 63篇 |
2015年 | 131篇 |
2014年 | 127篇 |
2013年 | 155篇 |
2012年 | 201篇 |
2011年 | 200篇 |
2010年 | 113篇 |
2009年 | 108篇 |
2008年 | 157篇 |
2007年 | 175篇 |
2006年 | 144篇 |
2005年 | 128篇 |
2004年 | 138篇 |
2003年 | 157篇 |
2002年 | 138篇 |
2001年 | 70篇 |
2000年 | 48篇 |
1999年 | 50篇 |
1998年 | 49篇 |
1997年 | 37篇 |
1996年 | 23篇 |
1995年 | 27篇 |
1994年 | 28篇 |
1993年 | 35篇 |
1992年 | 46篇 |
1991年 | 35篇 |
1990年 | 31篇 |
1989年 | 38篇 |
1988年 | 27篇 |
1987年 | 23篇 |
1986年 | 24篇 |
1985年 | 27篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 13篇 |
1981年 | 16篇 |
1980年 | 10篇 |
1979年 | 21篇 |
1978年 | 19篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1971年 | 9篇 |
1968年 | 9篇 |
排序方式: 共有3226条查询结果,搜索用时 15 毫秒
11.
Delayed type hypersensitivity against antigens of Fasciola hepatica has been repeatedly documented in infected hosts. Evidence has been presented to suggest that the delayed reactivity may develop earlier in the regional lymph nodes of the parasitized organ than in other lymph nodes of the body (Soulsby 1971). 相似文献
12.
13.
The isolation and sequence of a cDNA clone encoding the complete mitochondrial malate dehydrogenase (mMDH) of watermelon cotyledons is presented. Taking advantage of the polymerase chain reaction technology partial cDNA clones from the central part, the 3 part and the 5 part of the mRNA were obtained with oligonucleotides based on directly determined amino acid sequences. Subsequently, two complete cDNA clones for mMDH were synthesized with a sense primer corresponding to the nucleotide sequence of the amino terminal end of pre-mMDH and two antisense primers corresponding to the major alternative adenylation sites found in the mRNA.The amino acid residues for substrate and cofactor binding identified by X-ray crystallography for pig heart cytoplasmic MDH are conserved in the 320 amino acid long mature higher-plant mMDH. A presequence of 27 amino acids is present at the amino terminal end of the precursor protein. 相似文献
14.
A S Kuznetsov N S Parfenova V T Lozovski? R Z Vavrin V A Noskin V G Omel'ianenko L V Olennikova I A Ole?nik A G Vinogradov I V Krivoruchenko 《Ukrainski? biokhimicheski? zhurnal》1990,62(3):48-53
It has been shown that low-density plasma lipoproteins in patients with ischemic heart disease and hypertriglyceridemia are heavier in density, smaller in size, more negatively charged and more inclined to peroxide modification and aggregation than in healthy persons. The protein in the composition of such lipoproteins deviates towards the water phase, which may result in the masking of the domen, recognized by the BE-receptor and may lead to hyperlipidemia of a retaining character. 相似文献
15.
The 8-methoxycarbonyloctyl glycosides of GlcNAc, Gal1-4Glc, Fuc1-2Fuc1-3GalNac and Fuc1-2Gal1-3[Fuc1-4]GlcNac were converted to primary amines by reaction with neat ethylenediamine and then coupled to bovine serum albumin (BSA) using diethyl squarate as the connector. The average degree of incorporation of the sugar onto the protein, as well as the molecular weight distribution, could be conveniently determined using matrix assisted laser desorption ionization/time of flight (MALDI-TOF) mass spectrometry thus avoiding cumbersome structure-dependent colour-tests or analysis of cleaved ligand. The present coupling method has the advantages of proceeding under very mild conditions, yielding controlled incorporation values and can reliably be used for the coupling of very small amounts (mg) of oligosaccharide.This paper is dedicated to Sen-itiroh Hakomori on the occasion of his 65th birthday 相似文献
16.
The variation pattern in the perennial Hordeum brachyantherum complex and in the annual H. depressum are described. The diploid form of H. brachyantherum s. lat., endemic to California in USA, previously recognized as a separate species is here treated as a subspecies ( H. brachyantherum ssp. californicum ). Despite its restricted distribution it shows a considerable variation and overlap in morphology with the tetraploid ssp. brachyantherum , and no unambiguous determination based on morphology between the two tax a is possible. The tetraploid cytotype has a large distribution area in western North America and easternmost Asia and a very wide morphological variation. It has also a small disjunct distribution area in easternmost Canada. A single hexaploid population from California is referred to ssp. brachyantherum . 相似文献
17.
Terje H. Larsen Henrik S. Huitfeldt Ole Myking Thorvald Sætersdal 《Cell and tissue research》1993,272(2):201-210
A close spatial relationship between specific granules containing atrial natriuretic factor (ANF) and microtubules was demonstrated in primary cultures of neonatal rat cardiac myocytes. For the detection of specific granules and microtubules, the myocytes were double immunolabelled with antibodies against -ANF and -tubulin and examined by conventional fluorescence or laser scanning confocal microscopy. In addition, the ultrastructural distribution of specific granules was demonstrated by electron microscopy. In the atrial myocytes, ANF was stored in numerous specific granules that were mainly localized in the perinuclear sarcoplasm. In the ventricular myocytes, however, a minority of the cells (10%) exhibited limited ANF immunoreactivity after 4 days in culture. Microtubules were present throughout the sarcoplasm of the myocytes. They were most densely packed in the perinuclear regions. Depolymerization of the microtubules with nocodazole was followed by dispersal of ANF immunostaining both in the atrial myocytes and in the ventricular myocytes exhibiting ANF immunoreactivity. When the microtubules were allowed to recover, the perinuclear distribution of specific granules, as seen in non-treated myocytes, reappeared. Measurements of secreted immunoreactive ANF by radioimmunoassay revealed that the secretion of ANF from atrial myocytes into the medium was significantly reduced following nocodazole treatment, whereas a similar decrease in secretion from ventricular myocytes was not observed. These findings indicate that ANF-containing specific granules are closely associated with microtubules within the myocytes. It is suggested that secretion of ANF from the atrial myocytes, in contrast to the ventricular myocytes, is microtubule-dependent. 相似文献
18.
19.
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
20.
Ole Munk 《Acta zoologica》1990,71(2):89-95
Ontogenetic changes in the visual cell layer of the duplex retina during growth of the eye of the deep-sea teleost Gempylus serpens, the snake mackerel, are illustrated by comparing the retina of a small specimen with that of a previously studied adult fish. The small specimen has tightly packed cones spanning the whole width of the visual cell layer and small rods situated in its vitread part. Over most of the retina the cone population consists of single cones arranged in a very regular hexagonal mosaic. The temporalmost retina has a cone population consisting mainly of twin cones arranged in meridional rows. Growth of the eye is associated with an increase in the thickness of the visual cell layer and the density of rods and a total elimination of the densely packed single cones, the retina of the adult fish possessing only a temporally located population of double cones. The radical differences between the retina of the small and adult snake mackerel are probably associated with the different light regimes encountered by small and large specimens. 相似文献