全文获取类型
收费全文 | 1518篇 |
免费 | 116篇 |
国内免费 | 1篇 |
专业分类
1635篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 29篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 28篇 |
2017年 | 22篇 |
2016年 | 32篇 |
2015年 | 57篇 |
2014年 | 56篇 |
2013年 | 83篇 |
2012年 | 93篇 |
2011年 | 99篇 |
2010年 | 71篇 |
2009年 | 52篇 |
2008年 | 99篇 |
2007年 | 102篇 |
2006年 | 100篇 |
2005年 | 77篇 |
2004年 | 99篇 |
2003年 | 84篇 |
2002年 | 73篇 |
2001年 | 20篇 |
2000年 | 15篇 |
1999年 | 22篇 |
1998年 | 28篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 17篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 12篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1982年 | 4篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1973年 | 5篇 |
1969年 | 9篇 |
1965年 | 3篇 |
1963年 | 3篇 |
1924年 | 4篇 |
排序方式: 共有1635条查询结果,搜索用时 15 毫秒
91.
Constitutive activation of STAT3 is a common feature in many solid tumors including non-small cell lung carcinoma (NSCLC). While activation of STAT3 is commonly achieved by somatic mutations to JAK2 in hematologic malignancies, similar mutations are not often found in solid tumors. Previous work has instead suggested that STAT3 activation in solid tumors is more commonly induced by hyperactive growth factor receptors or autocrine cytokine signaling. The interplay between STAT3 activation and other well-characterized oncogenic "driver" mutations in NSCLC has not been fully characterized, though constitutive STAT3 activation has been proposed to play an important role in resistance to various small-molecule therapies that target these oncogenes. In this study we demonstrate that STAT3 is constitutively activated in human NSCLC samples and in a variety of NSCLC lines independent of activating KRAS or tyrosine kinase mutations. We further show that genetic or pharmacologic inhibition of the gp130/JAK2 signaling pathway disrupts activation of STAT3. Interestingly, treatment of NSCLC cells with the JAK1/2 inhibitor ruxolitinib has no effect on cell proliferation and viability in two-dimensional culture, but inhibits growth in soft agar and xenograft assays. These data demonstrate that JAK2/STAT3 signaling operates independent of known driver mutations in NSCLC and plays critical roles in tumor cell behavior that may not be effectively inhibited by drugs that selectively target these driver mutations. 相似文献
92.
93.
Schwarzenbacher R Jaroszewski L von Delft F Abdubek P Ambing E Biorac T Brinen LS Canaves JM Cambell J Chiu HJ Dai X Deacon AM DiDonato M Elsliger MA Eshagi S Floyd R Godzik A Grittini C Grzechnik SK Hampton E Karlak C Klock HE Koesema E Kovarik JS Kreusch A Kuhn P Lesley SA Levin I McMullan D McPhillips TM Miller MD Morse A Moy K Ouyang J Page R Quijano K Robb A Spraggon G Stevens RC van den Bedem H Velasquez J Vincent J Wang X West B Wolf G Xu Q Hodgson KO Wooley J Wilson IA 《Proteins》2004,55(3):759-763
94.
Xu Q Krishna SS McMullan D Schwarzenbacher R Miller MD Abdubek P Agarwalla S Ambing E Astakhova T Axelrod HL Canaves JM Carlton D Chiu HJ Clayton T DiDonato M Duan L Elsliger MA Feuerhelm J Grzechnik SK Hale J Hampton E Han GW Haugen J Jaroszewski L Jin KK Klock HE Knuth MW Koesema E Kreusch A Kuhn P Morse AT Nigoghossian E Okach L Oommachen S Paulsen J Quijano K Reyes R Rife CL Spraggon G Stevens RC van den Bedem H White A Wolf G Hodgson KO Wooley J Deacon AM Godzik A Lesley SA Wilson IA 《Proteins》2006,65(3):777-782
95.
The acute effects of a caffeine-containing supplement on strength, muscular endurance, and anaerobic capabilities 总被引:1,自引:0,他引:1
Beck TW Housh TJ Schmidt RJ Johnson GO Housh DJ Coburn JW Malek MH 《Journal of strength and conditioning research / National Strength & Conditioning Association》2006,20(3):506-510
The purpose of this study was to examine the acute effects of a caffeine-containing supplement on upper- and lower-body strength and muscular endurance as well as anaerobic capabilities. Thirty-seven resistance-trained men (mean +/- SD, age: 21 +/- 2 years) volunteered to participate in this study. On the first laboratory visit, the subjects performed 2 Wingate Anaerobic Tests (WAnTs) to determine peak power (PP) and mean power (MP), as well as tests for 1 repetition maximum (1RM), dynamic constant external resistance strength, and muscular endurance (TOTV; total volume of weight lifted during an endurance test with 80% of the 1RM) on the bilateral leg extension (LE) and free-weight bench press (BP) exercises. Following a minimum of 48 hours of rest, the subjects returned to the laboratory for the second testing session and were randomly assigned to 1 of 2 groups: a supplement group (SUPP; n = 17), which ingested a caffeine-containing supplement, or a placebo group (PLAC; n = 20), which ingested a cellulose placebo. One hour after ingesting either the caffeine-containing supplement or the placebo, the subjects performed 2 WAnTs and were tested for 1RM strength and muscular endurance on the LE and BP exercises. The results indicated that there was a significant (p < 0.05) increase in BP 1RM for the SUPP group, but not for the PLAC group. The caffeine-containing supplement had no effect, however, on LE 1RM, LE TOTV, BP TOTV, PP, and MP. Thus, the caffeine-containing supplement may be an effective supplement for increasing upper-body strength and, therefore, could be useful for competitive and recreational athletes who perform resistance training. 相似文献
96.
Characterization of the putative native and recombinant rat sterol transporter Niemann-Pick C1 Like 1 (NPC1L1) protein 总被引:3,自引:0,他引:3
Iyer SP Yao X Crona JH Hoos LM Tetzloff G Davis HR Graziano MP Altmann SW 《Biochimica et biophysica acta》2005,1722(3):282-292
The exact mechanistic pathway of cholesterol absorption in the jejunum of the small intestines is a poorly understood process. Recently, a relatively novel gene, Niemann-Pick C1 Like 1 (NPC1L1), was identified as being critical for intestinal sterol absorption in a pathway which is sensitive to sterol absorption inhibitors such as ezetimibe. NPC1L1 is a multi-transmembrane protein, with a putative sterol sensing domain. Very little else is known about the NPC1L1 protein. In this report, we characterize the native and recombinant rat NPC1L1 protein. We show that NPC1L1 is a 145 kDa membrane protein, enriched in the brush border membrane of the intestinal enterocyte and is highly glycosylated. In addition, sequential detergent extraction of enterocytes result in highly enriched preparations of NPC1L1. An engineered Flag epitope tagged rat NPC1L1 cDNA was expressed as recombinant protein in CHO cells and demonstrated cell surface expression, similar to the native rat protein. These biochemical data indicate that NPC1L1 exists as a predominantly cell surface membrane expressed protein, consistent with its proposed role as the putative intestinal sterol transporter. 相似文献
97.
Balachandran S Venkataraman T Fisher PB Barber GN 《Journal of immunology (Baltimore, Md. : 1950)》2007,178(4):2429-2439
The induction of type I (alphabeta) IFN following virus infection is necessary for the stimulation of effective antiviral host defense. In fibroblasts, a subset of primary genes (including those encoding IFN-beta and IFN-alpha4) are induced directly by intracellular dsRNA generated by the virus during its replication. These primary type I IFNs induce expression of IFN regulatory factor (IRF)-7, required for production of a second cascade of IFN-alpha subtypes and the further establishment of a complete antiviral state. Previously, we had reported on a role for Fas-associated death domain-containing protein (FADD) in the control of TLR-independent innate immune responses to virus infection. Our data in this study demonstrate that FADD is not only required for efficient primary gene induction, but is also essential for induction of Irf7 and effective expression of secondary IFN-alphas and other antiviral genes. Ectopic overexpression of IRF-7 partially rescued dsRNA responsiveness and IFN-alpha production, and a constitutively active variant of IRF-7 displayed normal activity in Fadd(-/-) murine embryonic fibroblasts. MC159, a FADD-interacting viral protein encoded by the molluscum contagiosum poxvirus was found to inhibit dsRNA-activated signaling events upstream of IRF-7. These data indicate that FADD's antiviral activity involves regulation of IRF-7-dependent production of IFN-alpha subtypes and consequent induction of secondary antiviral genes. 相似文献
98.
Eleni Larentzaki Glen Powell & Mike J. W. Copland 《Entomologia Experimentalis et Applicata》2007,124(2):143-151
This study investigated the effect of temperature on the development and overwintering potential of the predatory thrips Franklinothrips vespiformis (Crawford) (Thysanoptera: Aeolothripidae), a biological control agent used against glasshouse pests in continental Europe and Israel. Developmental rates increased linearly with rearing temperatures. It was estimated that 304.9 degree days, above a lower threshold temperature of 11.9 °C, were required for F. vespiformis to complete development from egg to adult eclosion. The effect of low temperatures (–5, 0, and 5 °C) was examined on adult female and larval survival. Subsequent reproductive and developmental attributes of survivors were also investigated. Lethal time experiments indicated that larval stages are more cold tolerant than adult F. vespiformis females. Surviving larvae increased their developmental times to adults with decreasing temperature and increasing exposure periods and second instars were significantly more successful than first instars in reaching adulthood. Surviving adult females decreased their oviposition rate with decreasing temperature and increasing exposure periods, and exposures to low temperatures affected the number of viable eggs produced. The results are discussed in the context of overwintering and establishment potential of F. vespiformis in the UK in the event of introducing the predatory thrips as a biological control agent against glasshouse pests. 相似文献
99.
100.
Validation of signature polarlipid fatty acid biomarkers for alkane-utilizing bacteria in soils and subsurface aquifer materials 总被引:3,自引:0,他引:3
David B. Ringelberg John D. Davis Glen A. Smith Susan M. Pfiffner Peter D. Nichols Janet S. Nickels J.Michael Henson John T. Wilson Marylynn Yates Donald H. Kampbell Harvey W. Read Thomas T. Stocksdale David C. White 《FEMS microbiology letters》1989,62(1):39-50
Abstract Extractable cell membrane-derived polarlipid ester-linked fatty acids (PLFA) obtained from aerated soils gassed with methane or propane and from methane- and propane-oxidizing bacteria isolated from the soils were analyzed by capillary gas chromatography/mass spectrometry. Exposure of aerated soils to methane resulted in the formation of a high proportion of an unusual 18-carbon mono-unsaturated PLFA, 18:lw8c. High proportions of this fatty acid biomarker are found in monocultures from this soil grown in minimal media with methane. This PLFA has been previously established as associated with authentic type II methane-oxidizing bacteria. The microbiota in aerated soils exposed to hydrocarbons containing propane, formed a suite of PLFA characterized by high proportions of a 16-carbon mono-unsaturated acid, 16:lw6c, and an 18-carbon saturated fatty acid with an additional methyl branch at the 10 position, 10 Me 18:0. This PLFA pattern has been detected in several monocultures enriched from the soil with propane-amended minimal media. The correspondence of high proportions of these unusual mono-unsaturated PLFA in the isolated monocultures and in situ in the soils after stimulation with the appropriate hydrocarbon is a strong validation of the utility of these biomarkers in defining the community structure of the surface soil microbial community. 相似文献