全文获取类型
收费全文 | 2235篇 |
免费 | 175篇 |
国内免费 | 1篇 |
出版年
2022年 | 18篇 |
2021年 | 50篇 |
2020年 | 30篇 |
2019年 | 35篇 |
2018年 | 40篇 |
2017年 | 18篇 |
2016年 | 65篇 |
2015年 | 84篇 |
2014年 | 99篇 |
2013年 | 112篇 |
2012年 | 157篇 |
2011年 | 156篇 |
2010年 | 76篇 |
2009年 | 100篇 |
2008年 | 96篇 |
2007年 | 117篇 |
2006年 | 122篇 |
2005年 | 82篇 |
2004年 | 73篇 |
2003年 | 63篇 |
2002年 | 60篇 |
2001年 | 56篇 |
2000年 | 48篇 |
1999年 | 48篇 |
1998年 | 32篇 |
1997年 | 22篇 |
1996年 | 18篇 |
1995年 | 22篇 |
1994年 | 28篇 |
1993年 | 11篇 |
1992年 | 41篇 |
1991年 | 37篇 |
1990年 | 27篇 |
1989年 | 30篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 16篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1974年 | 17篇 |
1972年 | 11篇 |
1971年 | 7篇 |
1969年 | 10篇 |
排序方式: 共有2411条查询结果,搜索用时 609 毫秒
31.
When B10.D2 (H-2d) mice are immunized with lymphoid cells from C57B1/10 (H-2
d
) and their antisera tested against B10.A (H-2
a
) target cells, only antibodies to H-2.5 are measured. The same is true for immunization of DBA/2 (H-2
d
) mice when their antisera are absorbed with B10.D2 cells prior to testing. Irrespective of the dose of immunogen administered, the primary hemagglutinin response of B10.D2 mice is significantly lower than that of DBA/2 mice and (B10.D2 × DBA/2)F1 hybrids, but the secondary responses are similar. The low responsiveness of B10.D2 mice appears to be determined by a single dominant gene with incomplete penetrance; the gene is not linked to eitherH- 2, Hc, or the immunoglobulin allotype loci. In addition, the H-2.5 hemagglutinin response is susceptible to nongenetic influences. When antisera from B10.D2, devoid of H-2.5 hemagglutinins, were assayed in a complement-mediated cytotoxic test, they contained almost as much anti-H-2.5 activity as did the antisera from DBA/2 mice or (B10.D2 × DBA/2)F1 hybrids. The possibility is discussed that the locus responsible for the deficient primary hemagglutinin response of B 10.D2 may not be determinant-specific but may affect hemagglutinin responses in general. 相似文献
32.
33.
34.
35.
Photosynthesis and Chlorophyll Fluorescence Characteristics in Relationship to Changes in Pigment and Element Composition of Leaves of Platanus occidentalis L. during Autumnal Leaf Senescence 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The loss of chlorophyll and total leaf nitrogen during autumnal senescence of leaves from the deciduous tree Platanus occidentalis L. was accompanied by a marked decline in the photosynthetic capacity of O2 evolution on a leaf area basis. When expressed on a chlorophyll basis, however, the capacity for light-and CO2-saturated O2 evolution did not decline, but rather increased as leaf chlorophyll content decreased. The photon yield of O2 evolution in white light (400-700 nanometers) declined markedly with decreases in leaf chlorophyll content below 150 milligrams of chlorophyll per square meter on both an incident and an absorbed basis, due largely to the absorption of light by nonphotosynthetic pigments which were not degraded as rapidly as the chlorophylls. Photon yields measured in, and corrected for the absorptance of, red light (630-700 nanometers) exhibited little change with the loss of chlorophyll. Furthermore, PSII photochemical efficiency, as determined from chlorophyll fluorescence, remained high, and the chlorophyll a/b ratio exhibited no decline except in leaves with extremely low chlorophyll contents. These data indicate that the efficiency for photochemical energy conversion of the remaining functional components was maintained at a high level during the natural course of autumnal senescence, and are consistent with previous studies which have characterized leaf senescence as being a controlled process. The loss of chlorophyll during senescence was also accompanied by a decline in fluorescence emanating from PSI, whereas there was little change in PSII fluorescence (measured at 77 Kelvin), presumably due to decreased reabsorption of PSII fluorescence by chlorophyll. Nitrogen was the only element examined to exhibit a decline with senescence on a dry weight basis. However, on a leaf area basis, all elements (C, Ca, K, Mg, N, P, S) declined in senescent leaves, although the contents of sulfur and calcium, which are not easily retranslocated, decreased to the smallest extent. 相似文献
36.
A G DiLella A Hawkins R J Craig S L Schreiber C A Griffin 《Biochemical and biophysical research communications》1992,189(2):819-823
Human FKBP12 and FKBP13 are encoded by distinct genes designated FKBP1 and FKBP2, respectively. Human FKBP1 was previously characterized. The characterization of human FKBP2 is described. FKBP2 is three kb in length and contains six exons. Fluorescence in situ hybridization of FKBP1 and FKBP2 genomic probes to metaphase chromosomes localized FKBP1 to human chromosome 20 band p13 and FKBP2 to human chromosome 11 band q13.1-q13.3. 相似文献
37.
38.
Ma Victoria Amores Paloma Hortelano Leticia García-Salguero José A. Lupiáñez 《Molecular and cellular biochemistry》1994,137(2):117-125
We have studied the effects of the diuretics mersalyl, furosemide and ethacrynic acid on renal gluconeogenesis in isolated rat-kidney tubules and on the activities of the most important gluconeogenic and glycolytic enzymes in both fed and fasted rats. Mersalyl (15 mg.kg–1 animal weight) significantly decreased the rate of gluconeogenesis in well-fed rats (68%) as well as in 24 and 48-h fasted ones (33 and 37% respectively). This inhibition occurred when lactate, pyruvate, glycerol or fructose were used as substrates. Ethacrynic acid at a dose of 50 mg.kg–1 animal weight provoked a transient inhibition of renal glucose production by almost 20% but only in fed rats with lactate as substrate, whereas the same dose of furosemide did not affect this metabolic pathway.Parallel to these changes, mersalyl caused a significant inhibition in the maximum activity of the most important gluconeogenic enzymes, phosphoenolpyruvate carboxykinase, fructose 1,6-bisphosphatase and glucose 6-phosphatase, in both fed and fasted rats. Neither ethacrynic acid nor furosemide produced any variations in the activities of these enzymes. The activity of the glycolytic enzymes phosphofructokinase and pyruvate kinase was not modified by these diuretics. Nevertheless, the activity of the thiol-enzyme glyceraldehyde 3-phosphate dehydrogenase was severely inhibited by mersalyl and to a lesser extent by the other diuretics. This inhibition was higher in fasted than fed rats. Hence, we conclude that the inhibitory effect of mersalyl on renal gluconeogenesis is due, at least partly, to a decrease in the flux through the gluconeogenic enzymes. Blood glucose was not modified after diuretic treatment in fed animals whereas mersalyl decreased the levels of blood glucose in 24-h fasted rats. Thein vivo effects of diuretics on gluconeogenesis correlate well with the previously observedin vitro effects, although ethacrynic acid was less potent as an inhibitorin vivo, probably because of its rapid clearance.Abbreviations EDTA
ethylenediaminetetraacetic acid
- EGTA
ethyleneglycolbis (-aminoethylether) N,N,N,N-tetraacetic acid
- DTT
dithiothreitol
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- TRIS
2-amino-2-hydroxymethyl-1,3-propanediol
Publication No. 166 from Drogas, Tóxicos Ambientales y Metabolismo Celular Research Group, Department of Biochemistry and Molecular Biology, University of Granada, Granada, Spain 相似文献
39.
Yosepha Shahak Christof Klughammer Ulrich Schreiber Etana Padan Inge Herrman Günter Hauska 《Photosynthesis research》1994,39(2):175-181
The reduction by sulfide of exogenous ubiquinone is compared to the reduction of cytochromes in chromatophores of Rhodobacter capsulatus. From titrations with sulfide values for Vmax of 300 and 10 moles reduced/mg bacteriochlorophyll a·h, and for Km of 5 and 3 M were estimated, for decyl-ubiquinone-and cytochrome c-reduction, respectively. Both reactions are sensitive to KCN, as has been found for sulfide-quinone reductase (SQR) in Oscillatoria limnetica, which is a flavoprotein. Effects of inhibitors interfering with quinone binding sites suggest that at least part of the electron transport from sulfide in R. capsulatus employs the cytochrome bc
1-complex via the ubiquinone pool.Abbreviations BChl a
bacteriochlorophyll a
- DAD
diaminodurene
- decyl-UQ
decyl-ubiquinone
- LED
light emitting diode
- NQNO
2-n-nonyl-4-hydroxyquinoline-N-oxide
- PQ-1
plastoquinone 1
- SQR
sulfide-quinone reductase (E.C. 1.8.5.'.)
- UQ
ubiquinone 10
- Qc
the quinone reduction site on the cytochrome b
6
f/bc
1, complex (also termed Qi or Qr or Qn)
- Qs
the quinone reduction site on SQR
- Qz
quinol oxidation site on the b
6
f/bc
1, complex (also termed Qo or Qp) 相似文献
40.