全文获取类型
收费全文 | 4778篇 |
免费 | 492篇 |
出版年
2023年 | 26篇 |
2022年 | 49篇 |
2021年 | 132篇 |
2020年 | 70篇 |
2019年 | 91篇 |
2018年 | 121篇 |
2017年 | 109篇 |
2016年 | 155篇 |
2015年 | 223篇 |
2014年 | 247篇 |
2013年 | 272篇 |
2012年 | 344篇 |
2011年 | 292篇 |
2010年 | 209篇 |
2009年 | 163篇 |
2008年 | 238篇 |
2007年 | 222篇 |
2006年 | 194篇 |
2005年 | 172篇 |
2004年 | 166篇 |
2003年 | 169篇 |
2002年 | 106篇 |
2001年 | 128篇 |
2000年 | 111篇 |
1999年 | 83篇 |
1998年 | 51篇 |
1997年 | 45篇 |
1996年 | 44篇 |
1995年 | 43篇 |
1994年 | 46篇 |
1993年 | 41篇 |
1992年 | 71篇 |
1991年 | 64篇 |
1990年 | 83篇 |
1989年 | 70篇 |
1988年 | 76篇 |
1987年 | 62篇 |
1986年 | 64篇 |
1985年 | 55篇 |
1984年 | 36篇 |
1983年 | 37篇 |
1982年 | 27篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 23篇 |
1978年 | 21篇 |
1977年 | 22篇 |
1976年 | 21篇 |
1974年 | 19篇 |
1973年 | 20篇 |
排序方式: 共有5270条查询结果,搜索用时 0 毫秒
61.
S Millar D C Hayward C A Read M J Browne R V Santelli F Garcia Vallejo M T Pueyo A Zaha D M Glover F J Lara 《Gene》1985,34(1):81-86
We have constructed a library of recombinant phage containing DNA from salivary gland chromosomes of Rhynchosciara americana. We have isolated phage from this library that carry sequences homologous to cDNA clones that hybridize in situ to the DNA puffs at the polytene chromosome regions C3 and C8. This has enabled us to demonstrate a 16-fold amplification of the genomic DNA sequences at these regions during DNA-puffing. At the C8 site there is a sequence element that has characteristics of 'scrambled' moderately repetitive DNA. This is located within 3 kb from the gene encoding a 1.95-kb mRNA. We have assayed restriction fragments from the two DNA puffs for Ars activity in yeast. The only strong Ars activity is associated with a part of the moderately repetitive DNA element from the C8 puff which is not present at this site in all animals. 相似文献
62.
Abstract Spore-forming sulfate-reducing bacteria (SRB) were enriched selectively from various kinds of aerobic soils with fatty acids as the sole carbon and energy source. A Gram-negative motile rod-shaped bacterium, which produced gas vacuoles during sporulation was isolated. It degraded alcohols, aromatic and n-fatty acids (up to C18 ) except for propionate, completely to CO2 . Sulfate, sulfite, thiosulfate or elemental sulfur served as electron acceptors. Because of its sensitivity to H2 S, the isolate never produced more than 8 mM dissolved sulfide at pH 7.0. G + C-content of the DNA was 48.0 mol %. The isolated strain Pato is described as a new species Desulfotomaculum sapomandens . 相似文献
63.
64.
O Kuchel R Garcia W Debinski K Racz N T Buu M Cantin J Genest 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1986,182(4):570-575
Conscious SHR and WKY rats were infused during 7 days with ANF (Arg 101-Tyr 126), 100 ng/hr/rat, by means of miniosmotic pumps and their basal blood pressure (BP), changes in sodium excretion and urinary catecholamines compared with those at the last day of the infusion. The SHR initial BP of 181 +/- 3 mmHg gradually declined to 137 +/- 5 mmHg. No significant change in blood pressure was observed in the ANF-infused WKY group. However, WKY rats exhibited an increased sodium excretion and urinary dopamine/norepinephrine ratio when compared to sham-infused rats. No such differences were observed in SHR. It is suggested that an ANF-induced withdrawal of the renal sympathetic tone permits the manifestation of its natriuretic action in WKY rats. When, however, a BP decrease predominates, as in SHR, this decrease results in a reflex sympathetic discharge with a renal sympathetic activity over-riding the ANF induced natriuresis seen in WKY rats. Secondary sympathetic responses to the ANF-induced BP decrease have to be thus taken into account when a dissociation between the hypotensive and natriuretic action of ANF is observed in vivo. 相似文献
65.
Establishment of two rabbit mammary epithelial cell lines with distinct oncogenic potential and differentiated phenotype after microinjection of transforming genes. 总被引:8,自引:0,他引:8
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
I Garcia B Sordat E Rauccio-Farinon M Dunand J P Kraehenbuhl H Diggelmann 《Molecular and cellular biology》1986,6(6):1974-1982
The goal of this work was to establish an assay for transformation of epithelial cells. Two epithelial cell lines were obtained after microinjecting transforming genes into primary rabbit mammary secretory cells. The cell lines were analyzed for their oncogenic potential and for the maintenance of a differentiated phenotype. A fully transformed cell line, which retained epithelial cell organization, was obtained by coinjecting simian virus 40 DNA and the activated human c-Ha-ras gene. The proliferation rate of these cells was high, with a doubling time of 16 h. Their growth was anchorage independent, and they had lost contact inhibition. The cells were tumorigenic in nude mice, but had no metastatic potential. Both microinjected DNAs were efficiently transcribed and translated, in contrast to the casein genes, which were expressed in primary cells but not in the transformed cell line. An immortalized cell line established after injection with simian virus 40 DNA alone was characterized by a moderate rate of proliferation with a doubling time of approximately 30 h. The growth of these cells was contact inhibited and anchorage dependent. The cells were not tumorigenic in nude mice. The viral DNA was expressed during early passages, as shown by the presence of the large T antigen in cell nuclei, but not at later passages. A high number of lactogenic hormone receptors were found associated with the cell surface. Despite the presence of these receptors, no induction of genes coding for milk proteins was observed after addition of prolactin. These data demonstrate that this assay system can be used to assess the immortalizing and transforming potential of candidate oncogenes in epithelial cells. 相似文献
66.
R Garcia G Constantopoulos J Gutkowska J Genest 《Canadian journal of physiology and pharmacology》1983,61(12):1473-1477
Chronic potassium deficiency in one-kidney one-clip hypertensive dogs significantly reduces blood pressure and plasma potassium, with a simultaneous increase in plasma renin activity. Tissue potassium concentration was decreased and tissue sodium concentration was increased in striated muscle and adrenal glands, which may suggest that the sodium-potassium pump was inhibited. In myocardium the sodium concentration was higher but the potassium concentration was not significantly lower than in control hypertensive dogs on normal diets. Arterial cation concentrations in the potassium-deficient group were not significantly different from those in the control group. Tissue norepinephrine concentration was higher in arteries from potassium-deficient animals, significantly so in the mesenteric and femoral arteries. The conclusion is that potassium deficiency may decrease blood pressure in the one-kidney one-clip hypertensive dogs by impairing the release of norepinephrine. 相似文献
67.
A.S.C. Wan T.L. Ngiam S.L. Leung M.L. Go P.W.S. Heng P.N. Natarajan A. Shafiee M. Vossoghi F. Savabi C.G. Francisco R. Freire R. Hernandez J.A. Salazar E. Suarez G.A.Garcia De La Mora Y.Grillasca R. O. Jimeno 《Steroids》1983,41(3):309-320
The synthesis of esters of norethisterone (17α-ethynyl-17β-hydroxy-estr-4-en-3-one) with acids containing a benzene ring is described, two methods of esterification being compared in terms of yield and convenience. The activities of these esters as long-acting contraceptive agents have been evaluated. 相似文献
68.
Reinvestigation of the shape and state of hydration of the skeletal myosin subfragment 1 monomer in solution 总被引:1,自引:0,他引:1
Hydrodynamic calculations lead to the conclusion that chymotryptic (or ethylenediaminetetraacetic acid) myosin S1 in solution (hydrated), at 1-5 degrees C, can be modeled as a prolate ellipsoid, with an axial ratio lying between p = 1.0 and 2.5 (major axis between 100.5 A, for p = 1.0, and 162.5 A, for p = 2.5). The degree of hydration is considerable (1.24 g/g for p = 2.5 and 2.02 g/g for p = 1.0). The dehydrated myosin head is pear-shaped under the electron microscope, and its narrowest part is located near the junction with the tail [Elliott, A., & Offer, G. (1978) J. Mol. Biol. 123, 505-519]. Mendelson & Kretzschmar [Mendelson, R. A., & Kretzschmar, K.M. (1980) Biochemistry 19, 4103-4108] have shown that the pear-shaped molecule does not predict the experimental X-ray scattering curve. Nor is this model able to predict the hydrodynamic values. The three-dimensional model for S1 used by Mendelson and Kretzschmar gives a rather good fit to the experimental X-ray scattering curve, but it does not predict the hydrodynamic values. In order to try to reconcile the three models and to fit the X-ray scattering curve and the hydrodynamic data, we suggest that, in solution, the S1 monomer has the shape of a prolate ellipsoid and that an inclusion of bound water exists at one extremity of the protein. The rest of bound water surrounds the protein. As first approximation, the dry protein and the hole are assumed to have the same shape as the hydrated molecule (prolate ellipsoid; p).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
69.
Teresa Garcia Pentti Tuohimaa Jan Mester Thierry Buchou Jack-Michel Renoir Etienne-Emile Baulieu 《Biochemical and biophysical research communications》1983,113(3):960-966
Preparations of the 90K and 110K components of the chick oviduct progesterone receptor (PR) purified to near homogeneity were tested for protein kinase activity. The 90K component was shown to incorporate radioactive phosphate from [γ-32P]-ATP in the presence of Ca2+ but not of Mg2+ ions, while the 110K component was phosphorylated in the presence of Mg2+, but not of Ca2+. The enzymatic activity of the 90K polypeptide appeared selective, since added proteins (histones) did not become phosphorylated. However, all proteins present in the 110K preparations were phosphorylated in the presence of Mg2+. These data suggest that components of the chick oviduct PR display protein kinase activity. 相似文献
70.
Herpes virus aotus: a latent herpesvirus from owl monkeys (Aotus trivirgatus) isolation and characterization 总被引:3,自引:0,他引:3