全文获取类型
收费全文 | 68625篇 |
免费 | 5823篇 |
国内免费 | 38篇 |
出版年
2023年 | 380篇 |
2022年 | 388篇 |
2021年 | 1456篇 |
2020年 | 1090篇 |
2019年 | 1237篇 |
2018年 | 1678篇 |
2017年 | 1487篇 |
2016年 | 2229篇 |
2015年 | 3133篇 |
2014年 | 3128篇 |
2013年 | 3931篇 |
2012年 | 4587篇 |
2011年 | 4264篇 |
2010年 | 2724篇 |
2009年 | 2477篇 |
2008年 | 2932篇 |
2007年 | 2871篇 |
2006年 | 2579篇 |
2005年 | 2837篇 |
2004年 | 2768篇 |
2003年 | 2340篇 |
2002年 | 1916篇 |
2001年 | 1714篇 |
2000年 | 1635篇 |
1999年 | 1440篇 |
1998年 | 648篇 |
1997年 | 634篇 |
1996年 | 661篇 |
1995年 | 520篇 |
1994年 | 539篇 |
1993年 | 514篇 |
1992年 | 1061篇 |
1991年 | 924篇 |
1990年 | 847篇 |
1989年 | 846篇 |
1988年 | 825篇 |
1987年 | 778篇 |
1986年 | 722篇 |
1985年 | 696篇 |
1984年 | 654篇 |
1983年 | 487篇 |
1982年 | 385篇 |
1981年 | 375篇 |
1980年 | 348篇 |
1979年 | 486篇 |
1978年 | 398篇 |
1977年 | 337篇 |
1975年 | 342篇 |
1974年 | 332篇 |
1973年 | 349篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
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
22.
23.
Extracts from the stems and leaves of Pitavia punctata Mol. were examined. The neutral fraction yielded β-sitosterol, daucosterin, quercetin, avicularin, and the previously undescribed quercetin 3-rhamnosylarabinoside. Braylin was co-extracted with the basic constituents, dictamnine, skimmianine and γ-fagarine. Acid hydrolysis of the leaves yielded cyanidin and delphinidin. 相似文献
24.
25.
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
26.
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
27.
The association between the red macroalga Jania adhaerens J. V. Lamour. and the sponge Haliclona caerulea is the most successful life‐form between 2 and 4 m depth in Mazatlán Bay (Mexican Pacific). J. adhaerens colonizes the rocky intertidal area and penetrates into deeper areas only when it lives in association with H. caerulea. The aposymbiotic form of the sponge has not been reported in the bay. To understand the ecological success of this association, we examined the capacity of J. adhaerens to acclimate in Mazatlán Bay using transplant experiments. The transplanted aposymbiotic J. adhaerens did not survive the first 2 weeks; however, J. adhaerens when living in association with H. caerulea, acclimated easily to depth, showing no sign of mortality during the 103 d of the experiment. We conclude that the ability of J. adhaerens to colonize in deeper areas in this hydrodynamic environment may in part rely on the protection provided by the sponge to the algal canopy. Both species contribute to the shape of the associated form. Nevertheless, the morphological variation in the association appears to be dominated by the variation in J. adhaerens canopy to regulate pigment self‐shading under light‐limited conditions and/or tissue resistance under high hydrodynamics. Consequently, our results are consistent with light as the abiotic controlling factor, which regulates the lower depth distribution of the association in Mazatlán Bay, through limiting the growth rate of J. adhaerens. Hydrodynamics may determine the upper limit of the association by imposing high mass losses. 相似文献
28.
29.
Lucas Henriques Viscardi Danilo Oliveira Imparato Maria Ctira Bortolini Rodrigo Juliani Siqueira Dalmolin 《Molecular biology and evolution》2021,38(3):735
The origin of nervous systems is a main theme in biology and its mechanisms are largely underlied by synaptic neurotransmission. One problem to explain synapse establishment is that synaptic orthologs are present in multiple aneural organisms. We questioned how the interactions among these elements evolved and to what extent it relates to our understanding of the nervous systems complexity. We identified the human neurotransmission gene network based on genes present in GABAergic, glutamatergic, serotonergic, dopaminergic, and cholinergic systems. The network comprises 321 human genes, 83 of which act exclusively in the nervous system. We reconstructed the evolutionary scenario of synapse emergence by looking for synaptic orthologs in 476 eukaryotes. The Human–Cnidaria common ancestor displayed a massive emergence of neuroexclusive genes, mainly ionotropic receptors, which might have been crucial to the evolution of synapses. Very few synaptic genes had their origin after the Human–Cnidaria common ancestor. We also identified a higher abundance of synaptic proteins in vertebrates, which suggests an increase in the synaptic network complexity of those organisms. 相似文献
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