全文获取类型
收费全文 | 3101篇 |
免费 | 140篇 |
出版年
2018年 | 22篇 |
2017年 | 32篇 |
2016年 | 47篇 |
2015年 | 73篇 |
2014年 | 66篇 |
2013年 | 118篇 |
2012年 | 129篇 |
2011年 | 129篇 |
2010年 | 90篇 |
2009年 | 52篇 |
2008年 | 127篇 |
2007年 | 110篇 |
2006年 | 107篇 |
2005年 | 116篇 |
2004年 | 118篇 |
2003年 | 108篇 |
2002年 | 110篇 |
2001年 | 58篇 |
2000年 | 56篇 |
1999年 | 60篇 |
1998年 | 25篇 |
1997年 | 23篇 |
1996年 | 32篇 |
1995年 | 44篇 |
1994年 | 38篇 |
1993年 | 32篇 |
1992年 | 61篇 |
1991年 | 66篇 |
1990年 | 62篇 |
1989年 | 60篇 |
1988年 | 48篇 |
1987年 | 45篇 |
1986年 | 46篇 |
1985年 | 59篇 |
1984年 | 55篇 |
1983年 | 39篇 |
1982年 | 41篇 |
1981年 | 41篇 |
1980年 | 27篇 |
1979年 | 36篇 |
1978年 | 33篇 |
1977年 | 39篇 |
1976年 | 19篇 |
1975年 | 29篇 |
1974年 | 29篇 |
1973年 | 26篇 |
1971年 | 17篇 |
1970年 | 13篇 |
1969年 | 13篇 |
1968年 | 12篇 |
排序方式: 共有3241条查询结果,搜索用时 140 毫秒
61.
Frank Thévenod Martine Dehlinger-Kremer Thomas P. Kemmer Anna-Luise Christian Barry V. L. Potter Irene Schulz 《The Journal of membrane biology》1989,109(2):173-186
Summary We have measured Ca2+ uptake and Ca2+ release in isolated permeabilized pancreatic acinar cells and in isolated membrane vesicles of endoplasmic reticulum prepared from these cells. Ca2+ uptake into cells was monitored with a Ca2+ electrode, whereas Ca2+ uptake into membrane vesicles was measured with45Ca2+. Using inhibitors of known action, such as the H+ ATPase inhibitors NBD-Cl and NEM, the Ca2+ ATPase inhibitor vanadate as well as the second messenger inositol 1,4,5-trisphosphate (IP3) and its analog inositol 1,4,5-trisphosphorothioate (IPS3), we could functionally differentiate two non-mitochondrial Ca2+ pools. Ca2+ uptake into the IP3-sensitive Ca2+ pool (IsCaP) occurs by a MgATP-dependent Ca2+ uptake mechanism that exchanges Ca2+ for H+ ions. In the absence of ATP Ca2+ uptake can occur to some extent at the expense of an H+ gradient that is established by a vacuolar-type MgATP-dependent H+ pump present in the same organelle. The other Ca2+ pool takes up Ca2+ by a vanadate-sensitive Ca2+ ATPase and is insensitive to IP3 (IisCaP). The IsCaP is filled at higher Ca2+ concentrations (10–6 mol/liter) which may occur during stimulation. The low steady-state [Ca2+] of 10–7 mol/liter is adjusted by the IisCaP.It is speculated that both Ca2+ pools can communicate with each other, the possible mechanism of which, however, is at present unknown. 相似文献
62.
Magali A. Théveniau John R. Raymond Geneviève N. Rougon 《The Journal of membrane biology》1989,111(2):141-153
Summary We developed site-directed rabbit antisera against synthetic peptides selected from the deduced amino acid sequence of the hamster lung 2-adrenergic receptor (amino acids 16–31 and 174–189, respectively). All antisera directed against peptide 1 (four of four rabbits) as well as two antisera directed against peptide 2 (two of four rabbits) recognized the purified 2-adrenergic receptor in immunoblot conditions when used at a dilution of 1500. Antisera directed against peptide 1 as well as peptide 2 were able to immunoprecipitate iodinated as well as125I-cyanopindolol tabeled 2-adrenergic receptor. This last result implies that the recognized epitopes do not contain the125I-cyanopindolol binding domain of the 2-adrenergic receptor. Immunoblot experiments performed on membrane fractions from hamster lung tissue showed that immunoreactive bands at 64,000, 57,000, 47,000, 44,000 and 38,000 daltons were specifically detected. When purified 2-adrenergic receptor was iodinated and submitted to glycolytic and/or tryptic treatments, species with similar molecular weights could be recovered. Then, the immunoreactive bands probably correspond to native 2-adrenergic receptor and to degradative or nonglycosylated species of this molecule. The antisera were also able to detect immunoreactive molecules in murine and human cell lines, suggesting conservation of the probed sequences between these species. Enzymatic linked immunosorbent assay tests on intact cells and immunofluorescence studies confirmed that the amino-terminus and putative first extracellular loop are extracellularly located. Immunofluorescence studies on mouse brain primary cultures showed that cells expressing 2-adrenergic receptor-like molecules exhibited a neuronal phenotype. 相似文献
63.
Summary Clinical and cytogenetical findings are described in an infant with a de novo deletion of the long arm of chromosome 2. The boy's karyotype is 46,XY, rec(2)delq,t(2;7) (2pter2q34::7p217pter) (7qter7p21::2q362qter). He showed developmental retardation, low-set ears, micrognathia, short neck, abundant skin of the neck, tetralogy of Fallot, bipartite labialike scrotum, clitorislike penis, cryptorchism, and deformities of the hands and feet. 相似文献
64.
We have used a cell-free system derived from hamster brain to investigate protein synthesis during experimental phenylketonuria. In such a system the elongation inhibitor emetine impeded translation in extracts derived from both treated and control animals. On the other hand the initiation inhibitor aurintricarboxylic acid showed no effects on protein synthesis activity of treated hamsters, although it was severely inhibiting in controls. This suggests that initiation is the altered step in brain protein synthesis failure consecutive to phenylketonuria.Abbreviations ATA
aurintricarboxylic acid
- HPA
hyperphenylalaninaemia (hyperphenylalaninaemic)
- PHE
phenylalanine
- PKU
phenylketonuria (phenylketonuric)
- PR
polyribosome 相似文献
65.
City spore concentrations in the European Economic Community (EEC). VI. Poaceae (Grasses), 1982–1986
Frits Th. M. Spieksma Gennaro D'amato John Mullins Nicole Nolard Reinhard Wachter Eva R. Weeke 《Aerobiologia》1989,5(1):38-43
Summary Airborne grass-pollen concentrations in six cities in the EEC are compared, based on observations from five years, 1982–1986.
Results show that there are quantitative differences both between the monitoring stations and between the years. Very provisionally,
the average seasonal total of the European urban airborne grass-pollen concentration can be put at 4 to 5000 per m3 of air. Also qualitatively, regarding the seasonal fluctuations, there are differences between the stations, and between
the years. Generally, the results confirm that June is the most typical grass-pollen month in northwestern Europe, whereas
in mediterranean Europe May is the more prominent grass-pollen period. There seems to be little coherence between the starting
dates of the grass-pollen season even at relatively nearby stations in northwestern Europe, suggestive for a great influence
of the actual weather situation. 相似文献
66.
The use of monoclonal antibodies to localize the low density lipoprotein receptor-binding domain of apolipoprotein B 总被引:10,自引:0,他引:10
R Milne R Théolis R Maurice R J Pease P K Weech E Rassart J C Fruchart J Scott Y L Marcel 《The Journal of biological chemistry》1989,264(33):19754-19760
Human apolipoprotein (apo) B-100 is composed of 4536 amino acids. It is thought that the binding of apoB to the low density lipoprotein (LDL) receptor involves an interaction between basic amino acids of the ligand and acidic residues of the receptor. Three alternative models have been proposed to describe this interaction: 1) a single region of apoB is involved in receptor binding; 2) groups of basic amino acids from throughout the apoB primary structure act in concert in apoB receptor binding; and 3) apoB contains multiple independent binding regions. We have found that monoclonal antibodies (Mabs) specific for a region that spans a thrombin cleavage site at apoB residue 3249 (T2/T3 junction) totally blocked LDL binding to the LDL receptor. Mabs specific for epitopes outside this region had either no or partial ability to block LDL binding. In order to define the region of apoB directly involved in the interaction with the LDL receptor we have tested 22 different Mabs for their ability to bind to LDL already fixed to the receptor. A Mab specific for an epitope situated between residues 2835 and 2922 could bind to its epitope on LDL fixed to its receptor whereas a second epitope between residues 2980 and 3084 is inaccessible on receptor-bound LDL. A series of epitopes near residue 3500 of apoB is totally inaccessible, and another situated between residues 4027 and 4081 is poorly accessible on receptor-bound LDL. In contrast, an epitope that is situated between residues 4154 and 4189 is fully exposed. Mabs specific for epitopes upstream and downstream of the region 3000-4000 can bind to receptor-bound LDL with a stoichiometry close to unity. Our results strongly suggest that the unique region of apoB directly involved in the LDL-receptor interaction is that of the T2/T3 junction. 相似文献
67.
A Direct Screening Procedure for Gravitropism Mutants in Arabidopsis thaliana (L.) Heynh. 总被引:5,自引:5,他引:0 下载免费PDF全文
Bertha L. Bullen Thérèse R. Best Mary M. Gregg Sara-Ellen Barsel Kenneth L. Poff 《Plant physiology》1990,93(2):525-531
In order to isolate gravitropism mutants of Arabidopsis thaliana (L.) Heynh. var Estland for the genetic dissection of the gravitropism pathway, a direct screening procedure has been developed in which mutants are selected on the basis of their gravitropic response. Variability in hypocotyl curvature was dependent on the germination time of each seed stock, resulting in the incorrect identification of several lines as gravitropism mutants when a standard protocol for the potentiation of germination was used. When the protocol was adjusted to allow for differences in germination time, these lines were eliminated from the collection. Out of the 60,000 M2 seedlings screened, 0.3 to 0.4% exhibited altered gravitropism. In approximately 40% of these mutant lines, only gravitropism by the root or the hypocotyl was altered, while the response of the other organ was unaffected. These data support the hypothesis that root and hypocotyl gravitropism are genetically separable. 相似文献
68.
The currently accepted type species of the genusTrichosporon Behrend isT. beigelii. This species has formerly been regarded as identical toT. cutaneum. However, these fungi are now known to represent separate species with different ecology. The first species described inTrichosporon wasT. ovoides, an agent of human white piedra. A neotype strain is designated for this species, while a lectotype strain is indicated forT. cutaneum. The nameT. beigelii is considered as doubtful and consequently cannot be maintained. 相似文献
69.
K. Thórarinsson 《BioControl》1990,35(1):107-118
Measurements of body length of cottony-cushion scales,Icerya purchasi Maskell, are presented. Although length increased markedly with developmental stage, the length distributions of successive
stages were found to overlap, making length an imperfect indicator of stage andvice versa. The likelihood of parasitism by the fly,Cryptochaetum iceryae (Williston), was found to increase with increasing scale size when scales of different sizes were concurrently made available
to the parasites under field conditions. Also, parasite loads (no. of parasites per parasitized host) were found to increase
with host size. The size ofC. iceryae pupae was found to depend on the developmental stage of the scale host in which pupation took place — the more developed
(larger) the host, the larger the pupa. This result suggests that parasite growth is food limited in the smaller hosts, and
that therefore its apparent preference for larger hosts is to the parasite's advantage.
相似文献
70.
Kay Robinson-Beers Th. D. Sharkey R. F. Evert 《Plant biology (Stuttgart, Germany)》1990,103(4):424-429
Sink-to-source transition was studied in developing sugarcane (Saccharum interspecific variety L62–96) leaves. Fully-expanded, mature sugarcane leaves were fed 14CO2 for 20 minutes, incorporating about 617 Bq. After five hours the leaves of each plant were cut into 1-cm-length segments that were weighed and then placed in scintillation cocktail for counting. All leaves younger than the leaf fed 14CO2 imported labeled photoassimilate. Three to four leaves had both importing and non-importing regions within the blade and a distinct transition region between them. A transition region was observed in leaves which had expanded to between 30 and 90 % of final blade length. Radioactivity per gram fresh weight was calculated as a measure of sink strength. Sink strength was greatest in the youngest leaf and declined with leaf age. The results of this study indicate that 1) import of photosynthate by developing sugarcane leaves occurs over a longer span of developmental ages than in dicotyledonous leaves and 2) the actual tissue region undergoing transition within such a leaf can be resolved as narrow zone between the importing and non-importing regions. 相似文献