全文获取类型
收费全文 | 58936篇 |
免费 | 4996篇 |
国内免费 | 39篇 |
出版年
2023年 | 264篇 |
2022年 | 444篇 |
2021年 | 1150篇 |
2020年 | 835篇 |
2019年 | 920篇 |
2018年 | 1288篇 |
2017年 | 1090篇 |
2016年 | 1779篇 |
2015年 | 2529篇 |
2014年 | 2500篇 |
2013年 | 3134篇 |
2012年 | 3708篇 |
2011年 | 3451篇 |
2010年 | 2105篇 |
2009年 | 2040篇 |
2008年 | 2505篇 |
2007年 | 2476篇 |
2006年 | 2240篇 |
2005年 | 2533篇 |
2004年 | 2506篇 |
2003年 | 2118篇 |
2002年 | 1729篇 |
2001年 | 1568篇 |
2000年 | 1477篇 |
1999年 | 1341篇 |
1998年 | 620篇 |
1997年 | 581篇 |
1996年 | 635篇 |
1995年 | 500篇 |
1994年 | 501篇 |
1993年 | 464篇 |
1992年 | 991篇 |
1991年 | 877篇 |
1990年 | 823篇 |
1989年 | 824篇 |
1988年 | 797篇 |
1987年 | 720篇 |
1986年 | 677篇 |
1985年 | 661篇 |
1984年 | 612篇 |
1983年 | 463篇 |
1982年 | 359篇 |
1981年 | 354篇 |
1980年 | 334篇 |
1979年 | 462篇 |
1978年 | 381篇 |
1977年 | 316篇 |
1975年 | 312篇 |
1974年 | 321篇 |
1973年 | 317篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
21.
Effects of antimicrotubular agents in cAMP production and in steroidogenic response of isolated rat Leydig cells 总被引:1,自引:0,他引:1
D Saltarelli M P De la Llosa-Hermier C Tertrin-Clary C Hermier 《Biology of the cell / under the auspices of the European Cell Biology Organization》1984,52(3):259-266
In dispersed rat Leydig cells, colchicine was found to stimulate basal cAMP production and testosterone secretion in a dose and time-dependent manner, but to a lesser extent than LH. However, these drugs are unable to stimulate adenylate cyclase activity in plasma membranes isolated from these cells. The amount of testosterone secreted at 150 min under the influence of colchicine and LH added simultaneously was not different from the amount produced during stimulation by LH alone. It is only after exposure of the cells for 1 hr to colchicine that the accumulation of cAMP in response to LH was inhibited; furthermore, both intracellular and medium testosterone accumulation in response to the hormone were reduced. Similar effects were observed with two other alkaloids, vinblastine and podophyllotoxin. The three drugs also inhibited the stimulation of testosterone secretion by 8-Br-cAMP or choleratoxin. These studies suggest that the state of microtubule polymerization and/or tubulin can influence the process of steroidogenesis in rat Leydig cells. 相似文献
22.
Morphological taxonomy of simple Hyphomycetes is complicated by the frequent occurrence of pleoanamorphism. In some groups
of yeast-like fungi, uncommon synanamorphs are diagnostic. Differences in conidiogenesis do not always delimit natural groups.
Some nomenclatural problems are mentioned, with an emphasis on the need of neotypification. Prospects are sketched for future
taxonomic research. 相似文献
23.
C Chong-Cerrillo M E Selsted E M Peterson L M de la Maza 《The journal of peptide research》2003,61(5):237-242
Four antimicrobial peptides, protegrin-1, RTD-1, cryptdin-4, and indolicidin, were tested for their ability to inhibit the in vitro growth of Chlamydia trachomatis serovars E, L2, and mouse pneumonitis (MoPn). In general, protegrin-1 was found to have the strongest anti-chlamydial activity. Overall, of the three serovars tested, L2 was the most susceptible while MoPn was the most resistant to these peptides. 相似文献
24.
25.
26.
M. de Kwaadsteniet C. A. van Reenen L. M. T. Dicks 《Probiotics and antimicrobial proteins》2010,2(2):61-65
The potential of nisin F as an antimicrobial agent in treating subcutaneous skin infections was tested in vivo by infecting C57BL/6 mice with a bioluminescent strain of Staphylococcus aureus (Xen 36). Strain Xen 36 has the luxABCDE operon located on a native plasmid. Mice were grouped into four groups: Infected with strain Xen 36 and treated with nisin F, infected with strain Xen 36 and treated with saline (placebo), not infected and treated with nisin (control) and not infected and not treated (control). The immune systems of the mice were suppressed with deksamethasone. Mice were treated with either nisin F or sterile physiological saline 24 and 48 h after infection with subcutaneously injected S. aureus Xen 36 (4 × 106 CFU). Histology and bioluminescent flux measurements revealed no significant difference between infected mice treated with nisin and saline, respectively. However, infected mice treated with nisin F had an increased number of polymorphonuclear cells when compared with infected mice treated with saline. Also, not infected mice treated with nisin F had an influx of polymorphonuclear cells. Nisin F is thus ineffective in combating deep dermal staphylococcal infections. The apparent immune modulation of nisin when subcutaneously injected has to be investigated. 相似文献
27.
Transcriptional regulatory network triggered by oxidative signals configures the early response mechanisms of japonica rice to chilling stress 总被引:3,自引:0,他引:3
28.
M. P. De Leon T. Yanagi M. Kikuchi J. Mu O. Ayau V. Matta M. Paz S. Juarez H. Kanbara I. Tada K. Hirayama 《International journal for parasitology》1998,28(12):1867-1874
Fifty fresh isolates of Trypanosoma cruzi from Triatoma dimidiata vectors and 31 from patients with Chagas disease were analysed for DNA polymorphisms within the 432-bp core region of the cruzipain gene which encodes the active site of cathepsin L-like cystein proteinase. The cruzipain gene showed signs of polymorphism consisting of four different DNA sequences in Central and South American isolates of T. cruzi. The PCR fragments of Guatemalan isolates could be divided into three groups, Groups 1, 2 and 3, based on different patterns of single-stranded DNA conformation polymorphism. All of the strains isolated from Brazil, Chile, and Paraguay, except for the CL strain, showed a Group 4 pattern. Two to four isolates from each group were analysed by cloning and sequencing. A silent mutation occurred between Groups 1 and 2, and five nucleotides and two aa substitutions were detected between Groups 1 and 3. The DNA sequence of Group 4 contained five nucleotides and one aa substitution from Group 1. All of the DNA sequences corresponded well with the single-stranded DNA conformation polymorphism. The Group 1 isolates, the majority in the Guatemalan population (70/81, 86.4%), were isolated from both triatomines and humans, but Group 3 were isolated only from humans. Moreover, the Group 2 isolates were detected only in triatomine vectors (9/50; 18%), but never in humans (0/32, P<0.05) suggesting that this group has an independent life-cycle in sylvatic animals and is maintained by reservoir hosts other than humans. 相似文献
29.
30.
Jin Wei Mia Madel Alfajaro Peter C. DeWeirdt Ruth E. Hanna William J. Lu-Culligan Wesley L. Cai Madison S. Strine Shang-Min Zhang Vincent R. Graziano Cameron O. Schmitz Jennifer S. Chen Madeleine C. Mankowski Renata B. Filler Neal G. Ravindra Victor Gasque Fernando J. de Miguel Ajinkya Patil Huacui Chen Craig B. Wilen 《Cell》2021,184(1):76-91.e13