全文获取类型
收费全文 | 3403篇 |
免费 | 140篇 |
国内免费 | 2篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 45篇 |
2020年 | 28篇 |
2019年 | 40篇 |
2018年 | 66篇 |
2017年 | 52篇 |
2016年 | 56篇 |
2015年 | 134篇 |
2014年 | 148篇 |
2013年 | 249篇 |
2012年 | 219篇 |
2011年 | 256篇 |
2010年 | 131篇 |
2009年 | 144篇 |
2008年 | 214篇 |
2007年 | 200篇 |
2006年 | 179篇 |
2005年 | 201篇 |
2004年 | 213篇 |
2003年 | 185篇 |
2002年 | 156篇 |
2001年 | 44篇 |
2000年 | 36篇 |
1999年 | 37篇 |
1998年 | 48篇 |
1997年 | 40篇 |
1996年 | 24篇 |
1995年 | 23篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 36篇 |
1991年 | 31篇 |
1990年 | 26篇 |
1989年 | 31篇 |
1988年 | 15篇 |
1987年 | 27篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1969年 | 5篇 |
排序方式: 共有3545条查询结果,搜索用时 704 毫秒
991.
The biotransformation of foreign substrates with suspension cells of Nicotiana tabacum was tested with (4R)-(?)- and (4S)-(+)-carvones, ( 相似文献
992.
Takayuki Iriyama Kohsuke Takeda Hiromi Nakamura Yoshifumi Morimoto Takumi Kuroiwa Junya Mizukami Tsuyoshi Umeda Takuya Noguchi Isao Naguro Hideki Nishitoh Kaoru Saegusa Kei Tobiume Toshiki Homma Yutaka Shimada Hitoshi Tsuda Satoshi Aiko Issei Imoto Johji Inazawa Kazuhiro Chida Yoshimasa Kamei Shiro Kozuma Yuji Taketani Atsushi Matsuzawa Hidenori Ichijo 《The EMBO journal》2009,28(7):843-853
Apoptosis and inflammation generally exert opposite effects on tumorigenesis: apoptosis serves as a barrier to tumour initiation, whereas inflammation promotes tumorigenesis. Although both events are induced by various common stressors, relatively little is known about the stress‐induced signalling pathways regulating these events in tumorigenesis. Here, we show that stress‐activated MAP3Ks, ASK1 and ASK2, which are involved in cellular responses to various stressors such as reactive oxygen species, differentially regulate the initiation and promotion of tumorigenesis. ASK2 in cooperation with ASK1 functioned as a tumour suppressor by exerting proapoptotic activity in epithelial cells, which was consistent with the reduction in ASK2 expression in human cancer cells and tissues. In contrast, ASK1‐dependent cytokine production in inflammatory cells promoted tumorigenesis. Our findings suggest that ASK1 and ASK2 are critically involved in tumorigenesis by differentially regulating apoptosis and inflammation. 相似文献
993.
Saneyoshi?UenoEmail author Suzuki?Setsuko Takayuki?Kawahara Hiroshi?Yoshimaru 《Conservation Genetics》2005,6(4):563-574
Genetic diversity and differentiation were analyzed in 11 populations of Magnolia stellata (Sieb. and Zucc.) Maxim. (Magnoliaceae) in the Tokai district, Japan. Variation at four nuclear microsatellite (nSSR) loci
was examined, three chloroplast microsatellite (cpSSR) markers were developed and 13 haplotypes identified. The 11 populations
were divided into three groups (A, B and C). Each population within the group was separated less than 40 km. Group B harbored
the highest gene diversity (H) and allelic richness (Ar) for nSSR (H=0.74 and Ar=8.02). Group C had the highest diversity of chloroplast haplotypes (H=0.79 and Ar=6.8): 2.5 times more haplotypes than the other groups. Each population contributed differently to the total diversity, with
respect to nSSR and cpSSR. AMOVA revealed that 58% of haplotypic and 15% of nSSR variation was partitioned among populations
within groups. A Mantel test revealed significant correlations between population pairwise geographic ln(distance) and FST/(1−FST) for both nSSR (r=0.479; P=0.001) and cpSSR (r=0.230; P=0.040). Dendrograms of populations for nSSR, based on Nei’s genetic distance, were constructed using UPGMA and the neighbor-joining
method. These results suggest that populations in group C have diverged from the other populations, while those in group B
are similar to each other. For group B, fragmentation between populations should be avoided in order to maintain gene flow.
For group C, the uniqueness of each population should be given the highest priority when planning genetic conservation measures
for the species. 相似文献
994.
An indispensable role for STAT1 in IL-27-induced T-bet expression but not proliferation of naive CD4+ T cells 总被引:7,自引:0,他引:7
Kamiya S Owaki T Morishima N Fukai F Mizuguchi J Yoshimoto T 《Journal of immunology (Baltimore, Md. : 1950)》2004,173(6):3871-3877
IL-27 is a novel IL-12 family member that plays a role in the early regulation of Th1 initiation, induces proliferation of naive CD4+ T cells, and synergizes with IL-12 in IFN-gamma production. It has been recently reported that IL-27 induces T-bet and IL-12Rbeta2 expression through JAK1/STAT1 activation. In the present study, we further investigated the JAK/STAT signaling molecules activated by IL-27 and also the role of STAT1 in IL-27-mediated responses using STAT1-deficient mice. In addition to JAK1 and STAT1, IL-27-activated JAK2, tyrosine kinase-2, and STAT2, -3, and -5 in naive CD4+ T cells. The activation of STAT2 and STAT5, but not of STAT3, was greatly diminished in STAT1-deficient naive CD4+ T cells. Comparable proliferative response to IL-27 was observed between STAT1-deficient and wild-type naive CD4+ T cells. In contrast, IL-27 hardly induced T-bet and subsequent IL-12Rbeta2 expression, and synergistic IFN-gamma production by IL-27 and IL-12 was impaired in STAT1-deficient naive CD4+ T cells. Moreover, IL-27 augmented the expression of MHC class I on naive CD4+ T cells in a STAT1-dependent manner. These results suggest that IL-27 activates JAK1 and -2, tyrosine kinase-2, STAT1, -2, -3, and -5 in naive CD4+ T cells and that STAT1 plays an indispensable role in IL-27-induced T-bet and subsequent IL-12Rbeta2 expression and MHC class I expression as well but not proliferation, while STAT3 presumably plays an important role in IL-27-induced proliferation. 相似文献
995.
Kurosu K Weiden MD Takiguchi Y Rom WN Yumoto N Jaishree J Nakata K Kasahara Y Tanabe N Tatsumi K Mikata A Kuriyama T 《Journal of immunology (Baltimore, Md. : 1950)》2004,172(11):7116-7122
We used a PCR and sequence procedure to analyze the Ig V(H) gene and the mutations in the 5' regulatory regions of BCL-6 genes in pulmonary lymphoproliferative disorders (mucosa-associated lymphoid tissue (MALT) lymphoma, HIV-related, EBV-related, and virus-negative lymphocytic interstitial pneumonia (LIP)). Eight of 20 (40%) pulmonary MALT lymphoma and 10 of 20 LIP (5 of 5 (100%) HIV-related, 2 of 5 (40%) EBV-related, and 3 of 10 (30%) virus-negative LIP) cases showed BCL-6 gene mutations. Intraclonal heterogeneity of the BCL-6 mutations was observed only in pulmonary MALT lymphoma cases whose Ig V(H) genes also showed intraclonal heterogeneity. Ongoing BCL-6 mutations might reflect re-entry into a germinal center pathway to further mutations. BCL-6 mutations in pulmonary MALT lymphoma and HIV-negative LIP showed some features (high transition to transversion ratio, standard polarity, and RGYW/WRCY bias) of Ig V(H) gene hypermutation, leading to the view that pulmonary MALT lymphomas and HIV-negative LIP are under the influence of germinal center hypermutation mechanisms. Because BCL-6 mutations in HIV-related LIP cases did not demonstrate features of Ig V(H) gene hypermutation, immunological reactions in HIV-related LIP are the result of a process different from that found in HIV-negative pulmonary lymphoproliferative disorders. 相似文献
996.
997.
Fujishima T Kittaka A Kurihara M Saito N Honzawa S Kishimoto S Sugiura T Waku K Takayama H 《The Journal of steroid biochemistry and molecular biology》2004,(1-5):89-92
All four possible A-ring stereoisomers of 2,2-dimethyl-1,25-dihydroxyvitamin D(3) (4) were designed and convergently synthesized. Nine-step conversion of methyl hydroxypivalate 6 provided the desired A-ring enyne synthon (13a,b) in good overall yield. Cross-coupling reaction of the A-ring synthon 13a,b with the CD-ring portion in the presence of palladium catalyst, followed by deprotection, gave the vitamin analogues (4a-d). We also synthesized four stereoisomers of 2,2-ethano-1,25-dihydroxyvitamin D(3) (5), as novel spiro-ring analogues having cyclopropane fused at the C2 position. Biological potencies of the synthesized compounds were assessed in terms of the vitamin D receptor (VDR) binding affinity, as well as the HL-60 cell differentiation-inducing activity. The 2,2-ethano analogue 5a showed a comparable activity to the natural hormone 1, while the 2,2-dimethyl analogue 4a exhibited one-third of the activity of 1 in cell differentiation, with the reduced VDR binding affinity. 相似文献
998.
999.
Synthesis of an immunosuppressant SQAG9 and determination of the binding peptide by T7 phage display 总被引:1,自引:0,他引:1
Yamazaki T Aoki S Ohta K Hyuma S Sakaguchi K Sugawara F 《Bioorganic & medicinal chemistry letters》2004,14(16):4343-4346
SQAG9, a new class of immunosuppressive sulfoquinovosylacylglycerol, and its biotinylated derivatives have been synthesized. A T7 Phage library, composed of random cDNA fragments from Drosophila melanogaster, displayed a possible binding peptide of 14 amino acids. The immobilized synthetic peptide on a sensor chip showed a dissociation constant of K(D)=1.5 x 10(-6) against SQAG9 in a surface plasmon resonance experiment. 相似文献
1000.
Yasumoto F Negishi T Ishii Y Kyuwa S Kuroda Y Yoshikawa Y 《Cellular and molecular neurobiology》2004,24(6):877-882
1. Synchronous oscillation of intracellular Ca2+ in the central nervous system is essential for neural development. We previously reported that endogenous dopamine was involved with synchronous Ca2+ oscillation of primary cultured midbrain neurons, and that regulation of dopamine in synchronous oscillation was distinctly different through dopamine receptor 1 (D1R) and 2 (D2R): the action of dopamine through D1R or D2R was facilitative or suppressive, respectively, to the Ca2+ influx of synchronous oscillation.2. In the present study, we confirmed that the suppressive effects of D2R were mediated by the regulation of the L-type voltage-gated Ca2+ channel, not by the regulation of NMDA receptor on the Ca2+ influx in the midbrain neural network showing synchronous oscillation.3. This evidence promotes better understanding of the regulation of neural activity by endogenous dopamine in networked neurons. 相似文献