全文获取类型
收费全文 | 10896篇 |
免费 | 918篇 |
出版年
2022年 | 89篇 |
2021年 | 163篇 |
2020年 | 119篇 |
2019年 | 158篇 |
2018年 | 202篇 |
2017年 | 171篇 |
2016年 | 271篇 |
2015年 | 441篇 |
2014年 | 449篇 |
2013年 | 643篇 |
2012年 | 736篇 |
2011年 | 692篇 |
2010年 | 477篇 |
2009年 | 437篇 |
2008年 | 594篇 |
2007年 | 639篇 |
2006年 | 565篇 |
2005年 | 565篇 |
2004年 | 567篇 |
2003年 | 567篇 |
2002年 | 637篇 |
2001年 | 134篇 |
2000年 | 98篇 |
1999年 | 141篇 |
1998年 | 159篇 |
1997年 | 144篇 |
1996年 | 130篇 |
1995年 | 110篇 |
1994年 | 100篇 |
1993年 | 103篇 |
1992年 | 109篇 |
1991年 | 86篇 |
1990年 | 77篇 |
1989年 | 68篇 |
1988年 | 58篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 57篇 |
1984年 | 73篇 |
1983年 | 60篇 |
1982年 | 101篇 |
1981年 | 89篇 |
1980年 | 65篇 |
1979年 | 59篇 |
1978年 | 59篇 |
1977年 | 57篇 |
1976年 | 58篇 |
1975年 | 41篇 |
1974年 | 35篇 |
1973年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
201.
Pierre Setif Suzanne Acker Bernard Lagoutte Jacques Duranton 《Photosynthesis research》1980,1(1):17-27
Under precise conditions, SDS PAGE allows purification of a photoactive P700-chla-protein complex from eucaryotic cells. The yield of P700 recovery is close to 100%. A total protein content equivalent to about 140 kD for one mole of P700 has been estimated by chemical analysis, and electrophoresis revealed the presence of two peptidic chains with MWs close to 65 kD. Photochemical and structural properties of this complex are given and compared with those of other complexes previously isolated. 相似文献
202.
Na+-ATPase of high-K+ and low-K+ sheep red cells was examined with respect to the sidedness of Na+ and K+ effects, using inside-out membrane vesicles and very low ATP concentrations (?2 μM). With varying amounts of Na+ in the medium, i.e., at the cytoplasmic surface, Nacyt+, the activation curves show that high-K+ Na+-ATPase has a higher affinity for Nacyt+ compared to low-K+. The apparent affinity for Nacyt+ is also increased by increasing the ATP concentrations in high-K+ but not low-K+. With Nacyt+ present, Na+-ATPase is stimulated by intravesicular Na+, i.e., Na+ at the originally external surface, Naext+, to a greater extent in low-K+ than high-K+. Intravesicular K+ (Kext+) activates Na+-ATPase in high-K+ but not in low-K+ vesicles and extravesicular K+ (Kcyt+) inhibits low-K+ but not high-K+ Na+-ATPase. Thus, the genetic difference between high-K+ and low-K+ is expressed as differences in apparent affinities for both Na+ and K+ and these differences are evident at both cytoplasmic and external membrane surfaces. 相似文献
203.
Odile Gateau Maria Rocha de Morillo Pierre Louisot Renée Morelis 《生物化学与生物物理学报:生物膜》1980,595(1):157-160
A sialyl transferase activity is found in purified mitochondria. It is not due to residual contamination and this enzymatic system is located in the outer mitochondrial membrane. This proves mitochondrial autonomy in regard to glycoconjugate sialylation. 相似文献
204.
Two endonucleases specific for DNA-containing apurinic or apyrimidinic sites (AP-endonucleases A and B) have been isolated from Micrococcus luteus and highly purified. These enzymes have no exonuclease activity. Both AP-endonucleases hydrolyze DNA-containing apurinic or apyrimidinic sites at the 5' end of the lesion, thus generating 3'-hydroxyl and 5'-phosphoryl end groups. DNA-containing pyrimidine dimers, introduced at low doses of UV, are not hydrolyzed, whereas DNA-containing lesions, introduced at high doses of UV or by gamma irradiation are nicked by either AP-endonuclease. During hydrolysis of apurinic DNA, neither of the AP-endonucleases acts as a processive enzyme. 相似文献
205.
206.
Summary RP4-prime plasmids containing chromosomal fragments of either Escherichia coli or Rhizobium meliloti were constructed in vitro. When introduced into E. coli or R. meliloti respectively, they promoted a polarized transfer of the chromosome as demonstrated either by the gradient of transfer of various markers or by the study of the genetic constitution of recombinants. In E. coli, mobilization was shown to be dependent upon the presence of a functional rec A system. Inheritance of markers was due to their integration into the chromosome of the recipient as shown by the need for a functional rec A system in the recipient E. coli or by mobilization of recessive markers in R. meliloti. The system described could be applied to genetic mapping in any Gram negative bacteria. 相似文献
207.
Axel Kahn Joelle Marie Juan Luis Vives-Corrons Pierre Maigret Albert Najman 《Human genetics》1981,57(2):172-175
Summary Anomalies of the mutant pyruvate kinase variants and clinical symptoms have been compared in 22 unrelated patients with congenital red cell pyruvate kinase deficiency. This study suggests that some characteristics of the mutant enzymes could play a role in the intensity of haemolysis, namely residual activity, affinity for the substrate phosphoenolpyruvate and for the allosteric activator fructose 1,6 diphosphate and inhibition by ATP. 相似文献
208.
Microbial ecologists attempting to describe community structures through the use of synthetic parameters face enormous difficulties.
These stem in part from the necessity of using standard taxonomic reference levels in a field where the species level is poorly
defined. This paper presents an attempt to obviate this problem. A “functional evenness” index (E) is defined using information measures; it is based directly on the characteristics of the bacteria, as determined, for example,
with the API 20B method. Comparisons of this index with classic structure indices, such as taxonomic evenness (Pielou) or
systematic dominance (Hulburt), show that it behaves like an evenness index, while bypassing the taxonomic study required
before computation of the classic indices. Its use is illustrated with samples of aerobic heterotrophic bacteria obtained
from brackish lagoon sediments.
We are grateful to our statistician colleagues, Dr. Yves Lepage from Université de Montréal and Dr. André Plante from Université
du Québec à Montréal. Both have contributed important elements to the discussion presented in this Appendix. 相似文献
209.
Using a number of intrafamilial PLTs raised against identical HLA haplotypes it has been possible to construct a model in an informative family defining the HLA-D region as a genetic system. This system consists of at least two regions separated by a recombination between HLA-D and GLO. In relation to the site of recombination, a minimum of one centromeric and three telomeric components can be identified per haplotype.—Fourteen PLTs raised and defined within the family were subsequently tested in a Caucasian population (n=84) and in 13 unrelated, complete families.—It is concluded that the hypothetical model proposed for the HLA-D region as a genetic system of linked loci, coding at the cell surface for associated but distinct components (at least four per haplotype), allows for typing of the components of the HLA-D system of any given haplotype. Serological typing of HLA-D components should, in the near future, provide a more convenient way of establishing component phenotypes than the present use of primed lymphocyte typing reagents. Among the components isolated, some have a high association with the classic alleles defined either by homozygous typing cells or DR serology. Others form the basis of cross-reactivity but their presence does not interfere with standard typing. Others, however, seem by their mere presence to be responsible for false assignments.—The concept of HLA-D as a genetic system clarifies many of the inconsistencies observed with a one-locus system.Research scientists from INSERM.Research Fellow from the Danish Medical Research Council.Central Blood Bank — Marseille 相似文献
210.
Debaryomyces phaffii inulinase was immobilized by adsorption on DEAE-cellulose. The immobilization caused a drop in optimum pH, a slight increase in optimum temperature and an important increase in the thermal stability of the system. The activity yield of immobilized inulinase was 75%.A continuous reactor operation was carried out. The utilization of this system permited the production of fructose syrup from inulin. 相似文献