全文获取类型
收费全文 | 25607篇 |
免费 | 1977篇 |
国内免费 | 13篇 |
专业分类
27597篇 |
出版年
2023年 | 96篇 |
2022年 | 215篇 |
2021年 | 399篇 |
2020年 | 256篇 |
2019年 | 352篇 |
2018年 | 423篇 |
2017年 | 395篇 |
2016年 | 625篇 |
2015年 | 1052篇 |
2014年 | 1181篇 |
2013年 | 1513篇 |
2012年 | 1748篇 |
2011年 | 1658篇 |
2010年 | 1103篇 |
2009年 | 1001篇 |
2008年 | 1342篇 |
2007年 | 1321篇 |
2006年 | 1343篇 |
2005年 | 1299篇 |
2004年 | 1258篇 |
2003年 | 1075篇 |
2002年 | 1163篇 |
2001年 | 361篇 |
2000年 | 294篇 |
1999年 | 333篇 |
1998年 | 350篇 |
1997年 | 277篇 |
1996年 | 292篇 |
1995年 | 262篇 |
1994年 | 282篇 |
1993年 | 280篇 |
1992年 | 275篇 |
1991年 | 213篇 |
1990年 | 189篇 |
1989年 | 203篇 |
1988年 | 192篇 |
1987年 | 155篇 |
1986年 | 137篇 |
1985年 | 177篇 |
1984年 | 219篇 |
1983年 | 158篇 |
1982年 | 202篇 |
1981年 | 159篇 |
1980年 | 167篇 |
1979年 | 134篇 |
1978年 | 135篇 |
1977年 | 124篇 |
1976年 | 99篇 |
1974年 | 98篇 |
1973年 | 97篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Summary Two dimensional gel electrophoresis of total cell protein extracts from not expanded, and primary leaves, petioles, and roots ofVicia faba resulted in four actin isoforms at 43 kDa with pI values from 5.9 to 6.05. In contrast to root extracts, in all leaf extracts an additional immunoreactive polypeptide with a molecular mass of 51 kDa and pI 5.75 was detected. This polypeptide was present in high amounts in protein extracts of purified chloroplasts, whereas no actin isoform at 43 kDa could be demonstrated. Compared to the tissue extracts, two actin isoforms at 43 kDa with pI values of 5.9 and 6.0 were enriched, when purified plasma membranes and the membranous fraction of vacuoles were analysed. In contrast, the soluble protein fraction of the plasma membrane preparation contained only two isoactins with pI values of 5.95 and 6.05 and a molecular mass of 43 kDa. These results indicate, that the four actin isoforms at 43 kDa detected in all examined tissues ofV. faba fulfill different functions at specific intracellular compartments, for example, the anchorage of actin microfilaments to membranes.Abbreviations BSA
bovine serum albumin
- BCIP
5-bromo-4-chloro-3-indolyl phosphate
- DDM
n-decyl -D-maltopyranoside
- EDTA
ethylenediamine-tetraacetic acid
- HG
n-hexyl -D-glucopyranoside
- IEF
isoelectrical focusing
- MES
morpholinoethanesulfonic acid
- 2-ME
2 mercaptoethanol
- NBT
nitro blue tetrazolium
- pCMB
p-chloromercuribenzoic acid
- PVP
polyvinylpyrrolidone
- Tris
tris (hydroxymethyl) aminomethane 相似文献
142.
Yeast Mutants Deficient in Er-Associated Degradation of the Z Variant of Alpha-1-Protease Inhibitor 总被引:2,自引:0,他引:2 下载免费PDF全文
A. A. McCracken I. V. Karpichey J. E. Ernaga E. D. Werner A. G. Dillin W. E. Courchesne 《Genetics》1996,144(4):1355-1362
Saccharomyces cerevisiae mutants deficient in degradation of alpha-1-proteinase inhibitor Z (A1PiZ) have been isolated and genetically characterized. Wild-type yeast expressing A1PiZ synthesize an ER form of this protein that is rapidly degraded by an intracellular proteolytic process known as ER-associated protein degradation (ERAD). The mutant strains were identified after treatment with EMS using a colony blot immunoassay to detect colonies that accumulated high levels of A1PiZ. A total of 120,000 colonies were screened and 30 putative mutants were identified. The level of A1PiZ accumulation in these mutants, measured by ELISA, ranged from two to 11 times that of A1PiZ in the parent strain. Further studies demonstrated that the increased levels of A1PiZ in most of the mutant strains was not the result of defective secretion or elevated A1PiZ mRNA. Pulse chase experiments indicated that A1PiZ was stabilized in several strains, evidence that these mutants are defective in ER-associated protein degradation. Genetic analyses revealed that most of the mutations were recessive, ~30% of the mutants characterized conformed to simple Mendelian inheritance, and at least seven complementation groups were identified. 相似文献
143.
Sabine Kölle Fred Sinowatz Gudrun Boie Ines Totzauer Werner Amselgruber Johnna Plendl 《The Histochemical journal》1996,28(6):441-447
Summary The mRNA of the zona pellucida glycoprotein ZP3 was localized in frozen sections of pig ovaries, isolated oocytes and early embryos byin situ hybridization using biotinylated oligonucleotide probes. In follicles, the distribution of mRNA for ZP3 was correlated with the developmental stage: in primordial and primary follicles, the mRNA was shown to be predominantly localized in the oocyte. In secondary follicles, mRNA was found in both the oocyte and follicle cells. In tertiary and preovulatory follicles, the follicle cells showed distinct staining, whereas the oocyte was labelled weakly. In the early embryo, i.e. 2 days after fertilization, mRNA for ZP3 could not be demonstrated. Our results suggest that, in the pig, the zona pellucida protein ZP3 is synthesized by the oocyte and the follicle cells in sequence. After fertilization, synthesis of ZP3 is terminated. 相似文献
144.
Populations ofLuzula multiflora s.l. in Ireland were examined karyologically. Plants from 14 populations were invariably tetraploid with 2n=24. Chromosomes of the tetraploid are of AL type (true tetraploidy). Meiosis of the tetraploids is of the same type as described for otherLuzula taxa in the literature. In meiosis, 12 bivalents are regularly formed. A hypothesis based on the morphological and allozyme data, that the tetraploids are of alloploid origin, is supported by the present results. Meiosis in an artificial hybrid between the presumed parental taxa,L. campestris andL. pallidula, was studied; a certain tendency towards chromosome doubling was observed. The geographical distribution of theL. multiflora cytotypes is also discussed. 相似文献
145.
Jan Lepš 《Folia Geobotanica》1995,30(4):455-459
Variance deficit in the number of species per sampling unit, as compared to a null model with species occurring independently of each other has been considered by various authors to be evidence for niche limitation. I show that simpler mechanisms could explain this phenomenon. Of those, the competition of individuals for space limits the number of individuals per sampling unit, resulting in decrease of variance in species richness. Testing the proportions of species belonging to various guilds seems to be more ecologically interesting, although here also the variance deficit can hardly be taken as reliable evidence for niche limitation. 相似文献
146.
Jan Nešvera Jitka Hochmannová Miroslav Pátek Alena Šroglová Věra Bečvářová 《Applied microbiology and biotechnology》1994,40(6):864-866
Gram-positive facultative methylotrophic coryneform bacterium Brevibacterium methylicum was efficiently transformed with various plasmids using electroporation of intact cells. In addition to the plasmid vectors pEC71 and pZ6-1 constructed on the basis of cryptic plasmids from coryneform bacteria, broad-host-range plasmids pLS5 (derivative of plasmid pMV158 from Streptococcus agalactiae) and RSF1010 belonging to the incompatibility group IncQ from Gram-negative bacteria were found to be present as autonomous structurally unchanged DNA molecules in B. methylicum transformants. With the exception of pZ6-1, all these plasmids were stably maintained in B. methylicum cells grown under non-selective conditions. When plasmid DNAs isolated from B. methylicum were used, the highest efficiency of transformation (105 transformants/g DNA) was achieved.
Correspondence to: J. Nevera 相似文献
147.
148.
149.
Stratigraphy of cladoceran remains in the upper 18 cm of a sediment core from the Lake Černé was studied. The successive disappearance
of Bosmina longispina, Daphnia longispina and Ceriodaphnia quadrangula from the upper layers of the sediment corresponds with our knowledge concerning the disappearance of these species from the
open water. 相似文献
150.
Changes in basin geomorphology after implementation of the Oosterschelde estuary project 总被引:8,自引:8,他引:0
The completion in 1986/87 of an open storm-surge barrier in the inlet and of secondary dams in the landward parts of the Oosterschelde tidal basin (SW Netherlands) has had and will continue to have a significant impact on geomorphological developments. An analysis of historic data, and of recent detailed bathymetric and morphodynamic process data, indicates that former trends have reversed. At present the Oosterschelde is a sedimentation basin with a degrading intertidal area and silting up of channels. The continuing reduction in intertidal area, the decreasing geomorphological gradients, the increasing fine sediment content of channel deposits, combined with a general reduction in hydrodynamics, imply significant ecological effects. 相似文献