全文获取类型
收费全文 | 5242篇 |
免费 | 387篇 |
国内免费 | 1篇 |
出版年
2022年 | 31篇 |
2021年 | 78篇 |
2020年 | 42篇 |
2019年 | 46篇 |
2018年 | 52篇 |
2017年 | 65篇 |
2016年 | 111篇 |
2015年 | 188篇 |
2014年 | 201篇 |
2013年 | 252篇 |
2012年 | 353篇 |
2011年 | 357篇 |
2010年 | 228篇 |
2009年 | 194篇 |
2008年 | 302篇 |
2007年 | 276篇 |
2006年 | 260篇 |
2005年 | 299篇 |
2004年 | 252篇 |
2003年 | 280篇 |
2002年 | 265篇 |
2001年 | 76篇 |
2000年 | 54篇 |
1999年 | 85篇 |
1998年 | 87篇 |
1997年 | 67篇 |
1996年 | 51篇 |
1995年 | 48篇 |
1994年 | 54篇 |
1993年 | 57篇 |
1992年 | 75篇 |
1991年 | 49篇 |
1990年 | 47篇 |
1989年 | 37篇 |
1988年 | 51篇 |
1987年 | 41篇 |
1986年 | 26篇 |
1985年 | 46篇 |
1984年 | 50篇 |
1983年 | 27篇 |
1982年 | 36篇 |
1981年 | 45篇 |
1980年 | 35篇 |
1979年 | 26篇 |
1978年 | 31篇 |
1977年 | 26篇 |
1976年 | 20篇 |
1974年 | 23篇 |
1973年 | 11篇 |
1961年 | 11篇 |
排序方式: 共有5630条查询结果,搜索用时 46 毫秒
131.
A new combination,Glandularia x hybrida, and a lectotype are proposed for the common Garden Vervain (Verbena xhybrida). The plant is of horticultural origin, but occurs widely in North America and Mexico as an adventive. 相似文献
132.
Ionactis caelestis Leary & Nesom is a new species known from a single population that occurs on the Aztec Sandstone near Bridge Mountain in the Spring Mountains of Clark County, Nevada. It is placed in the genus Ionactis (=Aster subg. Ianthe) on the basis of its crowded, multicipital crown, lack of persistent basal leaves and presence of densely arranged cauline ones, strongly carinate phyllaries, blue rays, disc style branches with linear-lanceolate appendages, asymmetric carpopodia, double pappus, and chromosome number of 2n = 9 II. A key to the four species of the genus emphasizes the distinction of the new species in its taproot, the abundant, large, glandular trichomes on its stems and leaves, and disc flowers with sterile ovaries. Ionactis is more similar to the goldenaster (Heterotheca) lineage than to Aster, with which it has been allied formerly. The core of the goldenaster genera differ from Ionactis primarily in their yellow-rayed heads, the crystal complement within cells of their disc corollas, and their primarily multinerved achenes. 相似文献
133.
134.
Leslie M. Loew Lawrence B. Cohen James Dix Eric N. Fluhler Valerie Montana Guy Salama Wu Jian-young 《The Journal of membrane biology》1992,130(1):1-10
The fast potentiometric indicator di-4-ANEPPS is examined in four different preparations: lipid vesicles, red blood cells, squid giant axon, and guinea pig heart. The dye gives consistent potentiometric responses in each of these systems, although some of the detailed behavior varies. In lipid vesicles, the dye displays an increase in fluorescence combined with a red shift of the excitation spectrum upon hyperpolarization. Similar behavior is found in red cells where a dual wavelength radiometric measurement is also demonstrated. The signal-to-noise ratio of the potentiometric fluorescence response is among the best ever recorded on the voltage-clamped squid axon. The dye is shown to be a faithful and persistent monitor of cardiac action potentials with no appreciable loss of signal or deterioration of cardiac activity for periods as long as 2 hr with intermittent illumination every 10 min. These results, together with previously published applications of the dye to a spherical lipid bilayer model and to cells in culture, demonstrate the versatility of di-4-ANEPPS as a fast indicator of membrane potential. 相似文献
135.
136.
137.
Association of 70-kilodalton heat-shock cognate proteins with acclimation to cold 总被引:11,自引:3,他引:8
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)
Neven LG Haskell DW Guy CL Denslow N Klein PA Green LG Silverman A 《Plant physiology》1992,99(4):1362-1369
138.
Sucrose phosphate synthase and sucrose accumulation at low temperature 总被引:26,自引:4,他引:22
The influence of growth temperature on the free sugar and sucrose phosphate synthase content and activity of spinach (Spinacia oleracea) leaf tissue was studied. When plants were grown at 25°C for 3 weeks and then transferred to a constant 5°C, sucrose, glucose, and fructose accumulated to high levels during a 14-d period. Predawn sugar levels increased from 14- to 20-fold over the levels present at the outset of the low-temperature treatment. Sucrose was the most abundant free sugar before, during, and after exposure to 5°C. Leaf sucrose phosphate synthase activity was significantly increased by the low-temperature treatment, whereas sucrose synthase and invertases were not. Synthesis of the sucrose phosphate synthase subunit was increased during and after low-temperature exposure and paralleled an increase in the steady-state level of the subunit. The increases in sucrose and its primary biosynthetic enzyme, sucrose phosphate synthase, are discussed in relation to adjustment of metabolism to low nonfreezing temperature and freezing stress tolerance. 相似文献
139.
Patricia Maurer Corinne Royer Bernard Mauchamp Patrick Porcheron Danile Debieu Guy Riba 《Archives of insect biochemistry and physiology》1991,16(1):1-9
The major ecdysteroids in large worker pupae of the leaf-cutting ant Acromyrmex octospinosus were characterized at the peak ecdysteroid concentration by using high-performance liquid chromatography, enzyme immunoassay, and mass spectrometry. In decreasing amounts, they were determined to be makisterone A, an unidentified C28 ecdysteroid bearing a molecular weight of 494, 20-hydroxyecdysone (ratio of 1 to 6 as compared to makisterone A), and putative but negligible ecdysone. The presence of both C28 and C27 ecdysteroids is discussed in relation to the content of 4-desmethylsterols determined by gas chromatography and mass spectrometry to be ergosta-5,7,24 (28)-trien-3β-ol, ergosterol, ergosta-5,7-dien-3β-ol and ergosta-7,24(28)-dien-3β-ol for the main sterols, and with a small amount of cholesterol. 相似文献
140.
Carl E. Hilliker Martine I. Darville Magdy S. Aly Mohamed Chikri Claude Szpirer Peter Marynen Guy G. Rousseau Jean-Jacques Cassiman 《Genomics》1991,10(4)
Two genes encoding 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase were localized in human and rat chromosomes. PFKFB1 (previously PFRX), which encodes the liver and muscle isozymes, was assigned to Xq22-q31 in the rat and to Xq27–q28 in the human by in situ hybridization using probes generated by the polymerase chain reaction. PFKFB2, which encodes the heart isozyme of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase, was assigned to chromosome 13 in the rat and to chromosome 1 in the human by hybridization of DNA from somatic cell hybrids. By in situ hybridization, this gene was localized to the regions 13q24–25 in the rat and 1q31 in the human. 相似文献