全文获取类型
收费全文 | 5942篇 |
免费 | 637篇 |
国内免费 | 6篇 |
出版年
2023年 | 35篇 |
2022年 | 65篇 |
2021年 | 159篇 |
2020年 | 85篇 |
2019年 | 110篇 |
2018年 | 125篇 |
2017年 | 116篇 |
2016年 | 195篇 |
2015年 | 286篇 |
2014年 | 296篇 |
2013年 | 317篇 |
2012年 | 416篇 |
2011年 | 428篇 |
2010年 | 279篇 |
2009年 | 242篇 |
2008年 | 366篇 |
2007年 | 326篇 |
2006年 | 315篇 |
2005年 | 287篇 |
2004年 | 255篇 |
2003年 | 249篇 |
2002年 | 219篇 |
2001年 | 106篇 |
2000年 | 72篇 |
1999年 | 93篇 |
1998年 | 60篇 |
1997年 | 44篇 |
1996年 | 60篇 |
1995年 | 57篇 |
1994年 | 39篇 |
1993年 | 31篇 |
1992年 | 61篇 |
1991年 | 43篇 |
1990年 | 52篇 |
1989年 | 52篇 |
1988年 | 50篇 |
1987年 | 27篇 |
1986年 | 34篇 |
1985年 | 40篇 |
1984年 | 42篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 33篇 |
1979年 | 19篇 |
1978年 | 29篇 |
1977年 | 31篇 |
1976年 | 21篇 |
1974年 | 26篇 |
1973年 | 22篇 |
排序方式: 共有6585条查询结果,搜索用时 31 毫秒
81.
The transport activities of two primary ATP-dependent organic-anion transporters in the tonoplast of isolated barley (Hordeum vulgare L. cv. Klaxon) vacuoles have been characterised with N-ethylmaleimide glutathione (NEM-SG) and taurocholate as substrates. The transporters showed different sensitivities to organic anions and a variety of transport inhibitors and drugs. The vacuolar uptake of NEM-SG was inhibited by carbonylcyanide 4-trifluoromethoxyphenylhydrazone, 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS), S-(2,4-dinitrophenyl)glutathione, alkyl-S-glutathione derivatives and taurocholate but stimulated by probenecid. The uptake of taurocholate was inhibited by vinblastine, DIDS and probenecid. Both transporters were unaffected by verapamil. The kinetic properties of the transporters indicate a general preference for amphiphilic anions with some substrate overlap. These characteristics of the transporters are similar to those displayed by the multidrug resistance protein of mammalian drug-resistant cells. We suggest that these vacuolar transporters be described as plant multispecific organic anion transporters (pMOATs).Abbreviations Bm-S
bimane S-glutathione
- DIDS
4,4-diisothiocyanatostilbene-2,2-disulfonic acid
- DNP-SG
S-(2,4-dinitrophenyl)glutathione
- FCCP
carbonylcyanide 4-trifluoromethoxyphenylhydrazone
- LTC4
cysteinyl leukotriene
- MDR
multidrug transporter
- MRP
multidrug resistance protein
- NEM-SG
N-ethylmaleimide glutathione
We thank Prof E. Martinoia for technical advice on the uptake experiments and Prof J. Palmer for helpful discussions and suggestions. M.B.-K. was partially sponsored by a grant from Stichting VSB Fonds, The Netherlands. IACR receives grant-aided support from the Biotechnology and Biological Science Research Council of the United Kingdom 相似文献
82.
Wehrman ME Fike KE Kojima FN Bergfeld EG Cupp AS Mariscal V Sanchez T Kinder JE 《Theriogenology》1996,45(3):593-610
The synchronization of estrus with synthetic progestins or progesterone (P(4)) results in the development of a large, persistent ovarian follicle. The objectives of the present study were to determine if development of a persistent ovarian follicle during synchronization of estrus suppresses recruitment of additional follicles during FSH treatment. On Day 5 of the estrous cycle (estrus = Day 0), beef cows were treated with 0.5 or 2.0 P(4) releasing intravaginal devices (PRIDs) for 8 d (Experiment 1, n = 20), 5 or 2 d (Experiment 2, n = 44) before initiation of FSH treatment. Prostaglandin F(2alpha) (25 mg) was administered on Days 5 and 6. Superovulation was induced with 24 mg of recombinant bovine FSH (rbFSH, Experiment 1) or 28 mg of FSH-P (Experiment 2) over a 3- or 4-d period, respectively. The PRIDs were removed concurrently with the 5th injection of rbFSH or FSH-P. There was a treatment-by-day interaction (P < 0.001) for the concentration of 17beta-estradiol in cows treated for 8, 5 or 2 d before FSH treatment. In Experiment 1, FSH treatment initiated 8 d after insertion of a 0.5 PRID did not affect the number of CL (6.9 +/- 1.4 vs 6.7 +/- 1.6), ova/embryos (3.7 +/-1.3 vs 3.0 +/- 1.3) and transferable embryos (2.4 +/- 0.9 vs 3.0 +/- 0.9) compared with that of the 2.0 PRIDs. In Experiment 2, FSH treatment initiated 5 d after insertion of a 0.5 PRID decreased the number of CL (4.0 +/- 0.5 vs 8.3 +/- 0.8; P < 0.001), ova/embryos (3.0 +/- 0.6 vs 5.9 +/- 1.2; P < 0.03) and transferable embryos (2.3 +/- 0.6 vs 5.1 +/- 1.0; P < 0.03) compared with that of a 2.0 PRID, respectively. Initiation of FSH treatment 2 d after insertion of a 0.5 PRID compared with a 2.0 PRID had no affect on the number of CL (8.0 +/- 2.1 vs 8.7 +/- 1.2), total ova (4.8 +/- 1.4 vs 6.9 +/- 1.4) and transferable embryos (2.9 +/- 1.2 vs 6.1 +/- 1.7). In conclusion, treatment with low doses of P(4) (0.5 PRID) for 5 d but not for 2 or 8 d before initiation of FSH treatment results in the development of a dominant ovarian follicle, which reduces recruitment of ovarian follicles, and the number of CL, total ova and transferable embryos. 相似文献
83.
The SWISS-2DPAGE database of two-dimensional polyacrylamide gel electrophoresis, its status in 1995. 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R D Appel J C Sanchez A Bairoch O Golaz F Ravier C Pasquali G J Hughes D F Hochstrasser 《Nucleic acids research》1996,24(1):180-181
SWISS-2DPAGE is a database of proteins identified on two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The current release contains 343 entries of human, yeast (Saccharomyces cerevisiae) and Escherichia coli origin, as well as virtual entries for each of the protein sequences in the SWISS-PROT database. 相似文献
84.
Felicity Z. Watts Neil Butt Philip Layfield Jesse Machuka Julian F. Burke Anthony L. Moore 《Plant molecular biology》1994,26(1):445-451
An Arabidopsis thaliana gene (UBC6) encoding a homologue to ubiquitin-conjugating enzymes has been isolated which is capable of encoding a protein of 183 amino acids of ca. 21 kDa. Northern analysis indicates that the gene is expressed in flowers, seeds and, to a somewhat lesser extent, in 10-day seedlings but not in mature leaves, callus and pre-flowering plants. This pattern of expression is confirmed using transgenic Arabidopsis plants containing a UBC6 promoter-GUS gene fusion construct. These plants displey GUS activity in mature anthers prior to dehiscence, in developing embryos, sepals and the style after pollination. 相似文献
85.
We have analysed the viability of cellular clones induced by mitotic recombination in Drosophila melanogaster/D. simulans hybrid females during larval growth. These clones contain a portion of either melanogaster or simulans genomes in homozygosity. Analysis has been carried out for the X and the second chromosomes, as well as for the 3L chromosome arm. Clones were not found in certain structures, and in others they appeared in a very low frequency. Only in abdominal tergites was a significant number of clones observed, although their frequency was lower than in melanogaster abdomens. The bigger the portion of the genome that is homozygous, the less viable is the recombinant melano-gaster/simulans hybrid clone. The few clones that appeared may represent cases in which mitotic recombination took place in distal chromosome intervals, so that the clones contained a small portion of either melanogaster or simulans chromosomes in homozygosity. Moreover, Lhr, a gene of D. simulans that suppresses the lethality of male and female melanogaster/simulans hybrids, does not suppress the lethality of the recombinant melanogaster/simulans clones. Thus, it appears that there is not just a single gene, but at least one per tested chromosome arm (and maybe more) that cause hybrid lethality. Therefore, the two species, D. melanogaster and D. simulans, have diverged to such a degree that the absence of part of the genome of one species cannot be substituted by the corresponding part of the genome of the other, probably due to the formation of co-adapted gene complexes in both species following their divergent evolution after speciation. The disruption of those coadapted gene complexes would cause the lethality of the recombinant hybrid clones. 相似文献
86.
Inactivation of bleomycin by an N-acetyltransferase in the bleomycin-producing strain Streptomyces verticillus 总被引:1,自引:0,他引:1
Masanori Sugiyama Takanori Kumagai Mitsuhiko Shionoya Eiichi Kimura Julian E. Davies 《FEMS microbiology letters》1994,121(1):81-85
Abstract Bleomycin-producing Streptomyces verticillus ATCC15003 possesses a bleomycin acetyltransferase which inactivates the drug in the presence of acetyl coenzyme A. The site of acylation in enzymically prepared acetylbleomycin A2 was determined by nuclear magnetic resonance analysis; the primary amino group of the β-aminoalanine moiety of bleomycin was acetylated. Acetylbleomycin A2 had no detectable antibacterial activity and did not induce in vitro DNA degradation. 相似文献
87.
F. León-Velarde J. Sanchez A. X. Bigard A. Brunet C. Lesty C. Monge-C 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(1):52-58
Capillarity, fibre types, fibre area and enzyme activities of different skeletal muscles (pectoralis, extensor digitorum longus), tibialis anterior, plantaris and the myocardium were compared in Andean coot (Fulica americana peruviana) native to high altitude (Junín, Perú, 4200 m) and the same species nesting at sea level. Numbers of capillaries per square millimeter were higher in all high-altitude muscles when compared with sea-level muscles (P<0.0001). Moreover, values for capillaries per fibre and capillaries in contact with each fibre were higher in digitorum and tibialis high-altitude muscles. Muscle fibres were classified as Type I, Type IIA or Type IIB on the basis of their myofibrillar ATPase pH lability. Pectoralis muscle of high-altitude and sea-level coots presented only fibres of Type IIA. In contrast, all the leg muscles studied showed a mosaic pattern of the three fibre types. Fibre areas were determined using a Leitz Texture Analysis System. Significant differences in fibre area were observed (P<0.01) between high-altitude and sea-level muscles. Mean muscle fibre diameters were also lower in the high-altitude group than in the sea-level group. The enzyme activities studied were hexokinase, lactate dehydrogenase, citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. The oxidative capacity, as reflected by citrate synthetase and hydroxyacyl-CoA-dehydrogenase activities, was greater for myocardial and pectoralis than for leg muscles. However, analysis of maximal enzyme activities showed that there were no significant differences between the glycolytic and oxidative enzyme activities of high-altitude and sea-level coots. These results suggest that in Andean coots genetically adapted to high altitude, changes in muscle capillarity and fibre size, in addition to high haemoglobin O2 affinity and low haemoglobin concentration, are sufficient to allow adequate energy production without increases in enzymatic activities.Abbreviations BSA
bovine serum albumin
- C:F ratio
Capillaries per fibre
- CAF
Capillaries in contact with each fibre
- CD
capillary density (mm-2)
- CS
citrate synthetase
- EDL
muscularis digitorum longus
- fra
fraction reduction area
- HA
high altitude
- HAD
hydroxyacyl-CoA-dehydrogenase
- HK
hexokinase
- LDH
lactate dehydrogenase
-
P
50
PO2 at which hemoglobin is half saturated with O2
-
P
aO2
arterial partial pressure of oxygen
- PAS
periodic acid-schiff
- PEC
muscularis pectoralis
- PLA
muscularis planaris
-
P
tO2
mean tissue oxygen pressure
-
P
vO2
mixed venous partial pressure of oxygen
- SD
standard deviation
- SL
sea level
- TA
muscularis tibialis anterior
- TAS
texture analysis system 相似文献
88.
Russell B. Lingham Keith C. Silverman Gerald F. Bills Carmen Cascales Manual Sanchez Rosalind G. Jenkins Suzanne E. Gartner Isabel Martin Maria T. Diez Fernando Peláez Sagrario Mochales Yu-Lin Kong Richard W. Burg Maria S. Meinz Leeyuan Huang Mary Nallin-Omstead Scott D. Mosser Michael D. Schaber Charles A. Omer David L. Pompliano Jackson B. Gibbs Sheo B. Singh 《Applied microbiology and biotechnology》1993,40(2-3):370-374
Chaetomellic acids A and B, isolated from Chaetomella acutiseta, are specific inhibitors of farnesyl-protein transferase that do not inhibit geranylgeranyl transferase type 1 or squalene synthase. Chaetomellic acids A and B are reversible inhibitors, resemble farnesyl diphosphate and probably inhibit FPTase by substituting for farnesyl diphosphate. Chaetomellic acid production appears to be widespread within the genus Chaetomella.
Correspondence to: R. B. Lingham 相似文献
89.
Genetic evidence for a functional relationship between Hsp104 and Hsp70. 总被引:12,自引:2,他引:10
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Y Sanchez D A Parsell J Taulien J L Vogel E A Craig S Lindquist 《Journal of bacteriology》1993,175(20):6484-6491
The phenotypes of single Hsp104 and Hsp70 mutants of the budding yeast Saccharomyces cerevisiae provide no clue that these proteins are functionally related. Mutation of the HSP104 gene severely reduces the ability of cells to survive short exposures to extreme temperatures (thermotolerance) but has no effect on growth rates. On the other hand, mutations in the genes that encode Hsp70 proteins have significant effects on growth rates but do not reduce thermotolerance. The absence of a thermotolerance defect in S. cerevisiae Hsp70 mutants is puzzling, since the protein clearly plays an important role in thermotolerance in a variety of other organisms. In this report, examination of the phenotypes of combined Hsp104 and Hsp70 mutants uncovers similarities in the functions of Hsp104 and Hsp70 not previously apparent. In the absence of the Hsp104 protein, Hsp70 is very important for thermotolerance in S. cerevisiae, particularly at very early times after a temperature upshift. Similarly, Hsp104 plays a substantial role in vegetative growth under conditions of decreased Hsp70 protein levels. These results suggest a close functional relationship between Hsp104 and Hsp70. 相似文献
90.
Patricia Colunga-Garcíamarín Julian Coello-Coello Lida Espejo-Peniche Lilia Fuente-Moreno 《Economic botany》1993,47(3):328-334
Recent ethnobotanical exploration of henequen (Agave fourcroydes) in the Peninsula of Yucatan, Mexico, finds that inflorescence peduncles are used as emergency food and in the preparation of a fermented drink. Bromatological analysis and determination of total carbohydrates were made for the two length classes (ca. 3.30 m and ca. 0.60 m) which are consumed. The analysis of both the cultivated plant and its putative wild ancestor (Agave angustifolia) suggests that utilization of the inflorescence peduncles as food may have been involved in the initial stages of the history of its evolution under artificial selection, because the wild and the cultivated plants have similar palatability. The subsequent agricultural prevalence of annual crop species in the region was possibly responsible for the abandonment of henequen in the local diet. No significant differences are observed between the bromatological and total carbohydrate values of domesticated and wild plants. The preference for small inflorescence peduncles as a vegetable is a consequence of its significantly minor content of raw fiber and its larger content of total carbohydrates. As a fermented drink, longer peduncles are preferred because they provide more substrate material and because fiber can be eliminated by filtering. This agricultural byproduct, almost totally wasted, has potential value as a source of carbohydrates and raw fiber. 相似文献