全文获取类型
收费全文 | 10720篇 |
免费 | 836篇 |
国内免费 | 2篇 |
出版年
2023年 | 67篇 |
2022年 | 52篇 |
2021年 | 134篇 |
2020年 | 121篇 |
2019年 | 133篇 |
2018年 | 303篇 |
2017年 | 291篇 |
2016年 | 387篇 |
2015年 | 540篇 |
2014年 | 547篇 |
2013年 | 711篇 |
2012年 | 874篇 |
2011年 | 818篇 |
2010年 | 524篇 |
2009年 | 396篇 |
2008年 | 591篇 |
2007年 | 597篇 |
2006年 | 476篇 |
2005年 | 459篇 |
2004年 | 454篇 |
2003年 | 415篇 |
2002年 | 424篇 |
2001年 | 269篇 |
2000年 | 298篇 |
1999年 | 220篇 |
1998年 | 91篇 |
1997年 | 63篇 |
1996年 | 78篇 |
1995年 | 56篇 |
1994年 | 40篇 |
1993年 | 46篇 |
1992年 | 113篇 |
1991年 | 91篇 |
1990年 | 94篇 |
1989年 | 68篇 |
1988年 | 69篇 |
1987年 | 63篇 |
1986年 | 78篇 |
1985年 | 56篇 |
1984年 | 52篇 |
1983年 | 52篇 |
1982年 | 52篇 |
1981年 | 31篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 28篇 |
1976年 | 14篇 |
1975年 | 16篇 |
1974年 | 20篇 |
1973年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
91.
Dissection of functional domains in phage fd adsorption protein. Discrimination between attachment and penetration sites 总被引:10,自引:0,他引:10
We constructed a set of deletion mutants in the attachment protein of phage fd. These mutants lack sequences coding for sections in the amino-terminal half. All the mutants that comprise a leader sequence are incorporated into phage particles. Our data strongly suggest a bipartite organization of the amino-terminal domain with (1) a region for receptor recognition and (2) a region that is necessary for penetration of the DNA into the host cell. These regions were mapped. Some evidence suggesting different roles for gene 3 protein in penetration of the outer and inner membrane are discussed. We demonstrate that the phenotypes caused by gene 3 protein in host cells can be subdivided into two groups with different sequence requirements: (1) phenotypes related to outer membrane disturbance; and (2) phenotypes related to the tolQRA transport system. 相似文献
92.
Subcellular localization of the major pneumococcal autolysin: a peculiar mechanism of secretion in Escherichia coli 总被引:9,自引:0,他引:9
E Díaz E García C Ascaso E Méndez R López J L García 《The Journal of biological chemistry》1989,264(2):1238-1244
The major pneumococcal autolysin (N-acetylmuramoyl-L-alanine amidase) has been localized in the cellular envelope of Streptococcus pneumoniae and Escherichia coli by using immunocytochemical labeling on ultrathin sections and whole-mounted cells. Cell fractionation experiments in E. coli confirmed the peripheral localization of the pneumococcal amidase and suggested that this enzyme is weakly bound to the outer face of the cytoplasmic membrane. This interaction does not depend on the presence of choline but represents an intrinsic property of the amidase. The autolysin, that is synthesized without any N-terminal signal sequence (García, P., García, J. L., García, E., and López, R. (1986) Gene (Amst.) 43, 265-272) was not processed during translocation. A new regulatory mechanism that might be specific for bacterial autolysins is discussed. 相似文献
93.
M García P Augereau P Briozzo F Capony V Cavailles G Freiss T Maudelonde P Montcourrier F Vignon H Rochefort 《Revista Espanola de Fisiología》1990,46(1):39-41
The lysosomal protease, pro-cathepsin D, is overexpressed and secreted by human breast cancers. In estrogen-responsive breast cancer cell lines, estrogens and growth factors stimulate cathepsin D expression through distinct mechanisms. Clinical studies indicate that high cathepsin D concentration in primary breast cancers is correlated with an increased risk of metastasis and particularly useful to orientate node-negative tumors towards an adjuvant therapy. 相似文献
94.
J. L. Molina-Cano L. F. García del Moral J. M. Ramos M. B. García del Moral P. Jiménez-Tejada I. Romagosa F. Roca de Togores 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,80(6):762-768
Summary Three mutants induced in the two-rowed barley variety Beka and their three binary recombinants have been used in an attempt to define an ideotype suitable for Mediterranean agroclimatic conditions. Physiological methods (classical plant growth analysis) together with the study of genotype x environment interaction for grain yield were used to characterize the genotypes. That characterization brought out the huge phenotypical variation produced by only three mutant genes, suggesting that single Mendelian genes may alone explain the quantitative variation, including grain yield, without the necessity of using the polygenic concept. The genotype best adapted to the environments studied is later in heading and has shorter straw and denser spikes than Beka; it also has higher inverse of leaf area rate and grain: leaf area ratio, a lower rate of leaf senescence, and a shorter grain filling period than the original variety. 相似文献
95.
A Otero M L García M C García B Moreno M S Bergdoll 《Applied and environmental microbiology》1990,56(2):555-559
Synthesis of enterotoxins C1 and C2 and thermonuclease throughout the growth cycle was investigated with Staphylococcus aureus type strains FRI137 and FRI361 and S. aureus isolates M5 (C1) and L2 (C2) of animal origin. Both enterotoxins were produced during the exponential growth phase or at the beginning of the stationary phase. The minimal incubation time (7 to 12 h) and the lowest population (10(7) to 2 x 10(9) CFU/ml) associated with detectable enterotoxin (1 to 6.5 ng/ml) were related to the total amount of toxin produced after 24 h. Thermonuclease was detected in all samples whenever enterotoxins were detected. Furthermore, strain FRI137 produced thermonuclease earlier and at lower cell populations than it did enterotoxin C1. Patterns of enterotoxin and thermonuclease synthesis did not correlate. The concentration of toxins increased throughout the growth cycle, while the concentration of thermonuclease remained constant during the last hours of the growth cycle. 相似文献
96.
R González-Cámpora G Mu?oz-Arias C Otal-Salaverri M Jorda-Heras E García-Alvarez A Gomez-Pascual A Garrido-Cintado A Hevia-Vázquez F Sánchez-Gallego H Galera-Davidson 《Acta cytologica》1992,36(6):905-917
We reviewed 98 cases of fine needle aspiration of soft tissue tumors with histologic confirmation performed during an eight-year period and propose a working morphologic classification based on the most prominent cytologic features. Six main tumor groups are recognized: myxoid, round cells, spindle cells, pleomorphic cells, polygonal cells and well differentiated. We believe that this classification allows recognition of the most common soft tissue tumors while helping with the differential diagnosis of other neoplasia, primary or secondary, with similar morphology and a similar presentation. 相似文献
97.
Reaction center-B875 pigment-protein complexes were purified from Rhodocyclus gelatinosus. The proteic components consist of 7–8 polypeptides among which some were identified by their apparent molecular weights: the light harvesting B875 polypeptides and of 8 and 6 kDa, reaction center L (23 kDa), M (28 kDa) and H (34 kDa), cytochrome c (43 kDa). Four c-type hemes were found per reaction center. Flash-induced absorbance changes showed the presence of both QA and QB in the complex. Charge recombination times were determined to be: 1.16±0.2 (n=30) for P+QAQB
- and 7–10 ms for P+QA
- in presence of herbicides. From quinone analysis on one hand and kinetics of charge recombination on the other hand, we proposed that in the reaction center of Rhodocyclus gelatinosus QA is menaquinone 8 and QB is ubiquinone 8. 相似文献
98.
A new spectrophotometric assay for dopachrome tautomerase 总被引:2,自引:0,他引:2
P Aroca F Solano J C García-Borrón J A Lozano 《Journal of biochemical and biophysical methods》1990,21(1):35-46
The existence of a new enzyme involved in mammalian melanogenesis has been recently reported. The names dopachrome oxidoreductase and dopachrome tautomerase have been proposed for the enzyme. So far, this enzyme has been assayed at 475 nm on the basis of its ability to catalyze dopachrome decoloration. This method presents two major problems, derived from the instability of the substrate (dopachrome): (1) dopachrome must be prepared immediately before use, and (2) the rate of dopachrome decoloration in the absence of the enzyme is not negligible, and, furthermore, is enhanced by non-enzymatic agents. In order to overcome these problems, we present a new procedure that combines: (1) a quantitative, fast and easy way to prepare dopachrome from L-dopa by sodium periodate oxidation; (2) a spectrophotometric method in the UV region, at 308 nm, based on following the absorbance increase due to the enzyme-specific tautomerization of dopachrome to 5,6-dihydroxyindole-2-carboxylic acid as opposed to the absorbance decrease due to the spontaneous decarboxylative transformation of dopachrome into 5,6-dihydroxyindole. The advantages of these methods as compared to the previously used procedures are discussed. 相似文献
99.
100.
A. García Diez L. Rivas Soriano F. de Pablo Dávila E. L. García Diez 《International journal of biometeorology》1996,39(3):148-150
In earlier papers a qualitative and quantitative model was developed for predicting the number of forest fires occurring per day. This model permits the forecast at 00.00 hours Universal Time Convention (UTC) of any day (d), the number of forest fires per day for a range of several days (d tod+5) over a particular region. Input data are the number of forest fires in the region during two preceding days (d–2 andd–1) and the type of day (real and evaluated from radiosonde ford–2,d–1,d and predicted from meteorological medium-range forecasts, i.e. of European Centre, ford+1,d+2,d+3,d+4 andd+5. As this model requires data obtained by radiosonde, particularly temperatures and geopotentials at 850 and 700 hPa and dew points (or specific humidity) at 850 hPa, this study investigates the spatial validity of the model in relation to the distance from the radiosonde station (RS). The highest quality forecast is obtained for the region immediately surrounding the RS, and diminishes with increasing distance from it, this being due to the data obtained from the RS not being representative of the atmospheric column over the region. Hence, the derivation of the critical distance for a particular quality level of measurement. Conversely, fixed quality level implies a specific separation between RS and the region for the prediction, with a higher predictive quality implying a shorter distance. 相似文献