全文获取类型
收费全文 | 15089篇 |
免费 | 1090篇 |
国内免费 | 2篇 |
专业分类
16181篇 |
出版年
2022年 | 66篇 |
2021年 | 176篇 |
2020年 | 101篇 |
2019年 | 131篇 |
2018年 | 194篇 |
2017年 | 175篇 |
2016年 | 280篇 |
2015年 | 401篇 |
2014年 | 518篇 |
2013年 | 905篇 |
2012年 | 779篇 |
2011年 | 794篇 |
2010年 | 516篇 |
2009年 | 505篇 |
2008年 | 859篇 |
2007年 | 833篇 |
2006年 | 784篇 |
2005年 | 814篇 |
2004年 | 839篇 |
2003年 | 793篇 |
2002年 | 656篇 |
2001年 | 421篇 |
2000年 | 432篇 |
1999年 | 379篇 |
1998年 | 177篇 |
1997年 | 173篇 |
1996年 | 134篇 |
1995年 | 163篇 |
1994年 | 132篇 |
1993年 | 130篇 |
1992年 | 271篇 |
1991年 | 236篇 |
1990年 | 256篇 |
1989年 | 214篇 |
1988年 | 196篇 |
1987年 | 187篇 |
1986年 | 164篇 |
1985年 | 158篇 |
1984年 | 137篇 |
1983年 | 118篇 |
1982年 | 102篇 |
1981年 | 86篇 |
1980年 | 65篇 |
1979年 | 96篇 |
1978年 | 87篇 |
1977年 | 78篇 |
1976年 | 50篇 |
1974年 | 54篇 |
1973年 | 42篇 |
1972年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Kazumi Asai Satoshi Hachimura Terumasa Toraya Shuichi Kaminogawa 《Cytotechnology》2001,36(1-3):145-153
The response of splenic CD4 T cells from ovalbumin (OVA)-specific T cell receptor (TCR) transgenic mice after long-term feeding
of a diet containing this antigen was examined. These CD4 T cells exhibited a decreased response to OVA peptide stimulation,
in terms of proliferation, interleukin-2 secretion, and CD40 ligand expression, compared to those from mice fed a control
diet lacking OVA, demonstrating that oral tolerance of T cells had been induced through oral intake of the antigen. We investigated
the intracellular signaling pathways, which were Ca/CN cascade and Ras/MAPK cascade, of these tolerant CD4 T cells using phorbol-12-myristate-13-acetate
(PMA) and ionomycin, which are known to directly stimulate these pathways. In contrast to the decreased response to TCR stimulation
by OVA peptide, it was shown that the response of splenic CD4 T cells to these reagents in the state of oral tolerance was
stronger. These results suggest that splenic CD4 T cells in the state of oral tolerance have an impairment in signaling, in
which signals are not transmitted from the TCR to downstream signaling pathways, and have impairments in the vicinity of TCR.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
We present an algorithm for prediction of RNA secondary structures.The program consists of three parts: the first computes locationand free energy of every possible stemloop structure,the second computes probability of its formation, and the thirdlists the positions and free energies of all the stemloopsin the order of their probability sizes. The circular RNA moleculeof chrysanthemum stunt viroid was used as an input data fordemonstrating the operation of the program.
Received on March 14, 1985; accepted on March 18, 1985 相似文献
994.
Passive immunization of mice with monoclonal antibodies to glycoprotein gB of herpes simplex virus 总被引:2,自引:0,他引:2
To investigate the protective ability of monoclonal antibodies (MCAs) to viral glycoprotein in herpes simplex virus (HSV) infection, athymic nude mice were inoculated intracutaneously with HSV type-1 (HSV-1) in the midflank. Three hours after inoculation, one group of mice was passively immunized with one of a series of MCAs to glycoprotein gB of HSV-1, and a control group of mice was given phosphate buffered saline alone. The control mice died within 16 days after infection, whereas the mice passively immunized with any of the MCA showed suppressed development of skin lesions. Three of six mice given MCA failed to develop any visible lesions and no HSV could be isolated from the lumbar dorsal root ganglia of these mice 60 days after the challenge. BALB/c mice were also protected from infection with HSV type 2 by passive immunization with MCA to HSV-1 gB. 相似文献
995.
Yamauchi S Masuda T Sugahara T Kawaguchi Y Ohuchi M Someya T Akiyama J Tominaga S Yamawaki M Kishida T Akiyama K Maruyama M 《Bioscience, biotechnology, and biochemistry》2008,72(11):2981-2986
The antioxidant activity of butane-type lignans was evaluated. Secoisolariciresinol (SECO) and dihydroguaiaretic acid (DGA) showed higher radical scavenging activity than that of 7,7'-dioxodihydroguaiaretic acid (ODGA). SECO and DGA inhibited the oxidation of unsaturated fatty acid. Both enantiomers of DGA were also lipoxygenase inhibitors, but neither enantiomer of SECO inhibited the lipoxygenase activity. 相似文献
996.
Huen MS Huang J Yuan J Yamamoto M Akira S Ashley C Xiao W Chen J 《Molecular and cellular biology》2008,28(19):6104-6112
The E2 ubiquitin-conjugating enzyme UBC13 plays pivotal roles in diverse biological processes. Recent studies have elucidated that UBC13, in concert with the E3 ubiquitin ligase RNF8, propagates the DNA damage signal via a ubiquitylation-dependent signaling pathway. However, mechanistically how UBC13 mediates its role in promoting checkpoint protein assembly and its genetic requirement for E2 variants remain elusive. Here we provide evidence to support the idea that the E3 ubiquitin ligase complex RNF8-UBC13 functions independently of E2 variants and is sufficient in facilitating ubiquitin conjugations and accumulation of DNA damage mediator 53BP1 at DNA breaks. The RNF8 RING domain serves as the molecular platform to anchor UBC13 at the damaged chromatin, where localized ubiquitylation events allow sustained accumulation of checkpoint proteins. Intriguingly, we found that only a group of RING domains derived from E3 ubiquitin ligases, which have been shown to interact with UBC13, enabled UBC13-mediated FK2 and 53BP1 focus formation at DNA breaks. We propose that the RNF8 RING domain selects and loads a subset of UBC13 molecules, distinct from those that exist as heterodimers, onto sites of double-strand breaks, which facilitates the amplification of DNA damage signals. 相似文献
997.
Changes in the antibiotic production by co-culture of Rhizopus peka P8 and Bacillus subtilis IFO3335
Tsubasa Fukuda Shintaro Yamamoto Hiroshi Morita 《World journal of microbiology & biotechnology》2008,24(9):1893-1899
The co-culture of Bacillus subtilis IFO 3335 with Rhizopus peka P8 or Rhizopus oligosporus P12 in liquid medium was found to increase production of antibiotic activity and to alter the spectrum of activity relative
to the pure cultures. However, a mixed culture of Rhizopus
arrhizus P7 and Rhizopus oryzae P17 did not produce antibiotic activity. The concentration, ratio, and time of addition of B. subtilis to the R. peka culture was found to influence antibiotic yields. Solid-state fermentations using mixed cultures of R. peka and B. subtilis were investigated. The growth of Escherichia coli IFO 3792 as a target bacterium was inhibited by the mixed culture. These results suggest the possibility of biopreservation
of fermented foods by novel co-culture systems. 相似文献
998.
A new genus, Versicolorisporium, is established for the coelomycetous fungus collected in Japan on dead culms of the bamboos Pleioblastus chino and Sasamorpha borealis. The type species of the genus, V. triseptatum, is characterized by the production of holoblastic, 3-septate, obovoid, versicolored conidia. Versicolorisporium is similar to Toxosporiella, Neohendersonia, Toxosporiopsis, and Scolicosporium in having versicolored conidia, but differs from these genera by the uniloculate pycnidial conidiomata with a periphysate
ostiole, lacking paraphyses, and the conidia without black-banded septa. A BLAST search using LSU nrDNA sequence indicates
that the new genus is a member of Pleosporales, Dothideomycetes. 相似文献
999.
Characteristic distribution of cathepsin E which immunologically cross-reacts with the 86-kDa acid proteinase from rat gastric mucosa 总被引:2,自引:0,他引:2
The antiserum raised against the high-molecular-weight acid proteinase from rat gastric mucosa, termed 86-kDa acid proteinase, has been shown to recognize rat cathepsin E, but not cathepsin D (Muto, N. et al. (1987) J. Biochem. 101, 1069-1075). Using this specific antiserum, characteristic distribution of cathepsin E in rats was demonstrated. The enzyme was detected in a limited number of tissues, such as stomach, thymus, spleen, bladder, and erythrocyte membranes. Among them, the highest activity was observed in the stomach. In contrast, cathepsin D immunoreactive with the antiserum specific to rat gastric cathepsin D was demonstrated in all the tissues examined. Cathepsin E-type enzymes partially purified from these five tissues were precipitated in the same manner by the specific antiserum, and they had the same molecular weight, electrophoretic mobility, and resistance against denaturation by 4 M urea. These results indicate that they could be exactly classified as cathepsin E. This type of enzyme was also detectable in mice and guinea pigs, but they showed relatively weak immunoreactivities with the antiserum. Thus, it is concluded that the distribution of cathepsin E is intrinsically different from ordinary cathepsin D, suggesting that it has a different physiological role from cathepsin D. 相似文献
1000.
Mitsuo Katano Hiroshi Yamamoto Tetsuro Mizoguchi Takeharu Hisatsugu 《Cancer immunology, immunotherapy : CII》1988,27(3):198-204
Summary A tumor growth inhibitory factor (TGIF) was induced in the culture supernatant from mixed culture of human peripheral blood mononuclear cells (PBMC) and a streptococcal preparation, OK-432, in vitro. The activity generated in the supernatant increased in a time-dependent fashion and first appeared 6 h after the initiation of culture, reaching its maximum around 48 h. The TGIF was cytostatic against seven of ten human tumor targets, but not against three murine tumor targets. Tumor cell growth was inhibited by a transient contact, i.e., 1 h, with TGIF. The TGIF was produced by lymphocytes but not by monocytes, because the activity was usually enhanced by elimination of plastic-adherent cells from the original PBMC fraction. The TGIF was relatively stable against heating at 56° C for 30 min, but the activity was totally destroyed after heating at 70° C for 5 min. The molecular weight of TGIF was estimated to be about 43×103 daltons by gel filtration. No interferon (IFN) activity was detected in the TGIF-positive fractions obtained by gel filtration, and the TGIF-positive fractions did not inhibit the growth of tumor necrosis factor (TNF)-sensitive mouse L929 cells. The TGIF activity was not significantly affected in neutralizing tests using specific antibodies against human IFN and TNF. The OK-432 was administered i.p. for management of cancer patients with malignant ascites. Ascites-derived mononuclear cells (ASMC) were obtained before and 3 to 5 days after OK-432 injection. The ASMC obtained after the injection produced TGIF in vitro in the absence of OK-432; the preinjection ASMC showed no such production. A positive correlation was found between TGIF-producing activity by ASMC and the effect of OK-432 injection on ascites volume. These results indicate that TGIF is induced in mononuclear cells by OK-432 not only in vitro but also in vivo and plays an important role in inhibition of tumor growth in cancer patients. 相似文献