全文获取类型
收费全文 | 20735篇 |
免费 | 1715篇 |
国内免费 | 2篇 |
出版年
2023年 | 172篇 |
2022年 | 160篇 |
2021年 | 415篇 |
2020年 | 314篇 |
2019年 | 368篇 |
2018年 | 721篇 |
2017年 | 602篇 |
2016年 | 742篇 |
2015年 | 776篇 |
2014年 | 801篇 |
2013年 | 1315篇 |
2012年 | 1630篇 |
2011年 | 1802篇 |
2010年 | 1019篇 |
2009年 | 774篇 |
2008年 | 1287篇 |
2007年 | 1259篇 |
2006年 | 1158篇 |
2005年 | 951篇 |
2004年 | 969篇 |
2003年 | 908篇 |
2002年 | 793篇 |
2001年 | 502篇 |
2000年 | 598篇 |
1999年 | 361篇 |
1998年 | 211篇 |
1997年 | 165篇 |
1996年 | 149篇 |
1995年 | 115篇 |
1994年 | 113篇 |
1993年 | 105篇 |
1992年 | 118篇 |
1991年 | 117篇 |
1990年 | 93篇 |
1989年 | 70篇 |
1988年 | 76篇 |
1987年 | 51篇 |
1986年 | 33篇 |
1985年 | 70篇 |
1984年 | 57篇 |
1983年 | 40篇 |
1982年 | 47篇 |
1981年 | 36篇 |
1980年 | 30篇 |
1979年 | 39篇 |
1978年 | 34篇 |
1977年 | 25篇 |
1976年 | 29篇 |
1974年 | 26篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
92.
93.
Alicia Mimbrera Luis Rivas Faustino Mollinedo Emilio Muñoz Vicente Larraga 《Molecular and cellular biochemistry》1983,56(1):73-80
Summary The combined use of proteolytic digestion and lactoperoxidase catalyzed labelling with [125I] applied to membrane-bound or soluble pure F1-ATPase from Micrococcus lysodeikticus has allowed us to establish the topography of its , , and subunits within the protein molecule and with respect to the plane of the membrane.The subunit is most externally located to the membrane bilayer looking towards the cytoplasmic face, a position consistent with its proposed catalytic role. The and subunits lie in an intermediate layer between the subunits and the membrane, in which the subunit occupies a central position within the F1-ATPase molecule in contact with the subunit. The subunit appears to be tightly bound to the F0 component of the ATPase complex, probably buried in the membrane bilayer. A molecular arrangement of M. lysodeikticus ATPase is proposed that, taking into account the subunit stoichiometry 3 3 2 2 (MW 420 000), accommodates the role assigned to each subunit and most, if not all, the known properties of this bacterial energy-transducing protein. 相似文献
94.
G. M. Besser Lynne Parke C. R. W. Edwards Isabel A. Forsyth A. S. McNeilly 《BMJ (Clinical research ed.)》1972,3(5828):669-672
In five patients with inappropriate lactation and amenorrhoea or impotence brom-ergocryptine was found to suppress the lactation and to diminish the raised plasma prolactin levels. The responses to treatment suggest that there may be an inverse relationship between prolactin secretion and gonadotrophin secretion in man. 相似文献
95.
96.
97.
J. C. Stockeri M. E. Fern ndez-g mez J. F. Lopez-s ez 《Biotechnic & histochemistry》1969,44(5):239-242
The kind of fixative and duration of fixation modify the affinity of plant cell structures, as shown by a 10-15 hr impregnation at 70 C in 2% aqueous AgNO2, and a 1-2 hr reduction at room temperature by a 1:1 mixture of 10% formalin and 1% hydroquinone. Cytoplasmic staining was enhanced by fixing in salts of heavy metals, in buffered 6.5% glutaraldehyde, and in 0.5% picric acid. Nuclear staining was prominent after mixtures of glutaraldehyde and hydroquinone, after formalin and pyrogallol, and after acetone, propylene glycol or ether. Nucleolar staining was favored by fixing in 10% formalin, in 5% formalin containing 0.5% hydroquinone, in 50% ethanol containing 0.5% pyrogallol, or in ethylene glycol. Chromosome staining was favored by fixation in 50% acetic or propionic acid, in 2% trichloroacetic acid, and in methanol or ethanol. The best morphological preservations were seen after 50% acetic acid, 6.5% glutaraldehyde, or the 5% formalin-0.5% hydroquinone mixture. 相似文献
98.
Resumen Se presentan 15 casos de aspergilosis recolectados en diferentes ciudades del país. Doce fueron casos autopsiados. Los tres restantes se refieren a pacientes en quienes se efectuó una lobectomía pulmonar superior derecha por aspergiloma gigante intracavitario. En los doce primeros existía una enfermedad básica que había alterado seriamente el estado general del paciente; once de ellos habían recibido antibióticos, cinco habían recibido esteroides, y dos, agentes citotóxicos. Se cree que, tanto el estado general del paciente, como la administración de dichas drogas, favorecieron la infección micótica. De los tres casos con aspergiloma intracavitario gigante, se cree que, en uno, la micosis se implantó en una caverna tuberculosa cicatrizada. En los otros dos, la cavidad era un bronquio localmente dilatado y se consideró que no existía una infección tuberculosa.ElAspergillus posee un amplio espectro de patogenicidad. Se le puede observar en lesiones que van desde una localización intrabronquial, acompañada de mínima o nula reacción inflamatoria, hasta casos en los cuales existen lesiones pulmonares necrotizantes con diseminación hematógena a otros órganos (sistema nervioso central, hígado, riñón). 相似文献
99.
Summary The study of the cell division cycle by means of caffeine labelling inAllium roots, at 15° C, employing intact root and decapitated roots at several levels (0.5, 1.0, 1.5, 2.0, and 2.5 mm) has shown that the number of cycles developed by the cells is constant at each meristem level. This number and the durations of the cycles are not affected by the decapitation. It is suggested that the cell cycle is controlled in the meristematic cells by an intracellular programme which would be developed throughout the meristem.However, the larger the region decapitated is, the more decreases the growth rate of the roots. The removal of the root cap (about 0.5 mm) did not modify the rate of root growth, although it blocked the geotropic response. The quiescent center is proposed as a source of auxin controlling cell elongation. 相似文献
100.
Protoplast-like structures have been formed by digestion of the cell walls ofFusarium culmorum conidia by lytic enzyme preparations ofMicromonospora AS. Under the test conditions extrusion of the protoplasts was not observed. It seems that digestion of the cell wall occurs in different stages. Digestion of the septa preceded the formation of protoplasts of the individual cells of the multicellularF. culmorum conidia. A few protoplasts survived the lytic enzyme treatment. “Protoplasts” obtained from conidia are much more stable than those obtained from young hyphae and were able to germinate with the formation of normal mycelium. Lysis of some of the protoplast bodies led to the formation of a membranous structure. The protoplasts derived from each of the constituent cells of the conidia could be isolated with the micromanipulator. No differences were found in the ability of the isolated cells to germinate. 相似文献