全文获取类型
收费全文 | 2532篇 |
免费 | 144篇 |
出版年
2023年 | 6篇 |
2022年 | 18篇 |
2021年 | 47篇 |
2020年 | 22篇 |
2019年 | 32篇 |
2018年 | 56篇 |
2017年 | 42篇 |
2016年 | 64篇 |
2015年 | 91篇 |
2014年 | 106篇 |
2013年 | 183篇 |
2012年 | 167篇 |
2011年 | 179篇 |
2010年 | 108篇 |
2009年 | 84篇 |
2008年 | 174篇 |
2007年 | 157篇 |
2006年 | 125篇 |
2005年 | 130篇 |
2004年 | 118篇 |
2003年 | 107篇 |
2002年 | 94篇 |
2001年 | 36篇 |
2000年 | 43篇 |
1999年 | 37篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 30篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 22篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 27篇 |
1988年 | 24篇 |
1987年 | 25篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 3篇 |
排序方式: 共有2676条查询结果,搜索用时 31 毫秒
21.
Guinea pig peritoneal exudate macrophages actively incorporated [3H]thymidine into trichloroacetic acid-insoluble fraction in vitro. The incorporation of [3H]thymidine was almost completely inhibited by aphidicolin, an inhibitor of DNA polymerase alpha and an autoradiograph showed heavy labeling in nuclei of 15% of macrophage populations. These results indicate that the observed thymidine incorporation was due to a nuclear DNA synthesis. The [3H]thymidine incorporation was markedly suppressed when macrophages were activated by immunoadjuvants such as muramyl dipeptide (MDP) or bacterial lipopolysaccharide (LPS). The suppression of [3H]thymidine incorporation by MDP was neither due to the decrease in thymidine transport through the cell membrane, nor due to dilution by newly synthesized "cold" thymidine. An autoradiograph revealed that MDP markedly decreased the number of macrophages the nuclei of which were labeled by [3H]thymidine. These results suggest that the suppression of [3H]thymidine incorporation by the immunoadjuvants reflects a true inhibition of DNA synthesis. The inhibition of DNA synthesis by MDP was also observed in vivo. Further, it was strongly suggested that the inhibition was not caused by some mediators, such as prostaglandin E2, released from macrophages stimulated by the immunoadjuvants but caused by a direct triggering of the adjuvants at least at the early stage of activation. Cyclic AMP appears to be involved in the inhibitory reaction. 相似文献
22.
Long-term follow-up study of rostral mesencephalic reticulotomy for pain relief--report of 34 cases 总被引:1,自引:0,他引:1
K Amano H Kawamura T Tanikawa H Kawabatake M Notani H Iseki T Shiwaku T Nagao Y Iwata T Taira 《Applied neurophysiology》1986,49(3):105-111
A long-term follow-up study of rostral mesencephalic reticulotomy (RMR) for pain relief is presented. 34 patients (24 males and 10 females) were operated. Ages ranged from 18 to 65 years. The follow-up period was 1-70 months. The overall effectiveness of RMR showed good relief of pain in 23 patients (67%). The study of effectiveness of RMR according to type of pain showed good relief of pain in 5 out of 6 patients (83%) with nondenervation pain, whereas satisfactory pain relief was obtained in 18 out of 28 patients (64%) with denervation pain. 相似文献
23.
Keisuke Kohmoto Kazuya Akimitsu Tetsuyuki Kohguchi Hiroshi Otani John M. Gardner 《Plant cell reports》1986,5(1):54-56
Amberlite XAD-7, a nonionic polyacrylate adsorbent, was found to be a very effective protectant for isolating mitochondria from tissues rich in oils and phenolics. Physiologically active, well-coupled mitochondria were successfully prepared from young green leaf tissues of citrus, apple, pear and tobacco.Abbreviations DNP
2,4-dinitrophenol
- CCCP
carbonyl cyanide m-chlorophenylhydrazone
- BSA
bovine serum albumin
- PVP
polyvinylpyrrolidone 相似文献
24.
Larvae of genus Pieris in the northern part of Kyoto City are parasitized by two tachinid flies:Epicampocera succincta, a specialist on genus Pieris, and Compsilura concinnata, a generalist with very wide host-range. We surveyed the parasitism rates of Pieris by both flies for two years at six study areas. In these study areas, there lived three host species in the genus Pieris: P. rapae, P. melete, and P. napi, but neither tachinid parasitized P. napi to any significant extent. In the mountainous district, P. rapae and P. melete coexisted and their populations were relatively continuous, while in the lowland, only P. rapae larvae were abundant in spring and autumn, but even they disappeared in summer. Parasitisms by E. succincta occurred mainly in mountainous district and never in the lowland. C. concinnata parasitized Pieris in all the areas, but its parasitisms occurred mainly in autumn. We analyzed the factors affecting the spatial and temporal patterns of parasitism rates and presumed that the temporal discontinuity of host population restricted the distribution of the specialist parasitoid. 相似文献
25.
Hohzoh Kiyohara Toshiro Watanabe Junko Imai Noboru Takizawa Takashi Hatta Kazutaka Nagao Akira Yamamoto 《Applied microbiology and biotechnology》1990,33(6):671-676
Summary To breed industrially useful strains of a slow-growing, red-pigment-producing strain ofMonascus anka, protoplasts ofM. anka MAK1 (arg) andAspergillus oryzae AOK1 (met, thr) were fused. A mixture of protoplasts prepared from mycelia ofM. anka MAK1 treated with 2% Usukizyme and ofA. oryzae AOK1 treated with 2% Usukizyme and 0.2% NovoZym 234 was incubated with 30% (w/v) polyethylene glycol no. 6000. Heterokaryon fusants complementing the auxotrophies of both mutants were isolated on minimal medium, but segregated into red (MAK1) and white (AOK1) sectors after being cultured on a complete medium. After irradiation with UV light, the fusants gave stable heterozygous diploids that formed long white hyphae. These diploids, which had twice as much DNA in the nucleus as their parents, grew more rapidly than the parent strain YZT1, and produced ethanol earlier than the parents. Production of amylase, protease, and kojic acid by the fusants was intermediate in amount between that of the two parents. 相似文献
26.
Peter R. LaFayette Ronald T. Nagao Kevin O'Grady Elizabeth Vierling Joe L. Key 《Plant molecular biology》1996,30(1):159-169
Three cDNA clones (GmHSP23.9, GmHSP22.3, and GmHSP22.5) representing three different members of the low-molecular-weight (LMW) heat shock protein (HSP) gene superfamily were isolated and characterized. A fourth cDNA clone, pFS2033, was partially characterized previously as a full-length genomic clone GmHSP22.0. The deduced amino acid sequences of all four cDNA clones have the conserved carboxyl-terminal LMW HSP domain. Sequence and hydropathy analyses of GmHSP22, GmHSP22.3, and GmHSP22.5, representing HSPs in the 20 to 24 kDa range, indicate they contain amino-terminal signal peptides. The mRNAs from GmHSP22, GmHSP22.3, and GmHSP22.5 were preferentially associated in vivo with endoplasmic reticulum (ER)-bound polysomes. GmHSP22 and GmHSP22.5 encode strikingly similar proteins; they are 78% identical and 90% conserved at the amino acid sequence level, and both possess the C-terminal tetrapeptide KQEL which is similar to the consensus ER retention motif KDEL; the encoded polypeptides can be clearly resolved from each other by two-dimensional gel analysis of their hybrid-arrest translation products. GmHSP22.3 is less closely related to GmHSP22 (48% identical and 70% conserved) and GmHSP22.5 (47% identical and 65% conserved). The fourth cDNA clone, GmHSP23.9, encodes a HSP of ca. 24kDa with an amino terminus that has characteristics of some mitochondrial transit sequences, and in contrast to GmHSP22, GmHSP22.3, and GmHSP22.5, the corresponding mRNA is preferentially associated in vivo with free polysomes. It is proposed that the LMW HSP gene superfamily be expanded to at least six classes to include a mitochondrial class and an additional endomembrane class of LMW HSPs. 相似文献
27.
Phosphorylation of a Protein (pp56) is Related to the Regeneration of Rice Cultured Suspension Cells 总被引:3,自引:0,他引:3
Short-term cultured suspension cells of rice (Oryza sativa L.)are capable of regeneration, but not in long-term culture. Forclarification of the mechanism of regeneration, protein phosphorylationin short-term and long-term cultured suspension cells was comparedby two dimensional- polyacrylamide gel electrophoresis. A 56kDa protein having an isoelectric point of 4.5 was phosphorylatedin vitro in short-term cultured suspension cells, but was notphosphorylated after regeneration. This protein in longtermcultured suspension cells remained phosphorylated after transferto the regeneration medium. However, using an antibody raisedagainst this protein from short-term cultured suspension cells,it was always detected in long-term and short-term culturedsuspension cells after transfer to the regeneration medium.The partial amino acid sequence of the HPLC-purified proteinshowed homology to a calcium-binding protein from maize. Thephosphorylation of the 56 kDa protein (pp56) appears to be associatedwith the regeneration of cultured rice cells. (Received December 11, 1995; Accepted June 3, 1996) 相似文献
28.
Indoor climate was assessed in an apartment in Isehara City, Kanagawa Prefecture, Japan, by use of a fungal index. The index represents the environmental (climate) capacity to allow fungal growth; it is determined by measuring the growth rate of a biosensor fungus, Eurotium herbariorum J-183. Differences in climate among various parts of the apartment (microclimate) and its changes could be clarified by using the index. The index in the entire apartment was high in summer, low in winter, and intermediate in spring and autumn. According to the part of the apartment, the index was high in water-associated areas and cool areas. This high fungal index in cool areas was caused by the air at the same absolute humidity showing an increase in the relative humidity with a decrease in temperature. Fungal contamination rapidly progressed in areas with a high fungal index in this apartment. A correlation was observed between the fungal index and fungal contamination. Therefore, areas susceptible to fungal contamination can be estimated by use of the fungal index. 相似文献
29.
Keisuke Tsutsumi Masami Niwa Naoki Kitagawa Sei-ich Yamaga Takeo Anda †Akihiko Himeno ‡Takaya Sato Humayun Khalid Kohtaro Taniyama Shobu Shibata 《Journal of neurochemistry》1994,63(6):2240-2247
Abstract: We identified and characterized 125I-endothelin-1 (125I-ET-1) binding sites in tumor capillaries isolated from human glioblastomas, using the quantitative receptor autoradiographic technique with pellet sections. Quantification was done using the computerized radioluminographic imaging plate system. High-affinity ET receptors were localized in capillaries from glioblastomas and the surrounding brain tissues (KD = 4.7 ± 1.0 × 10?10 and 1.6 ± 0.3 × 10?10M, respectively; Bmax = 161 ± 38 and 140 ± 37 fmol/mg, respectively; mean ± SEM, n = 5). BQ-123, a selective antagonist for the ETA receptor, potently competed for 125I-ET-1 binding to sections of the microvessels with IC50 values of 5.1 ± 0.3 and 5.1 ± 1.5 nM, and 10?6M BQ-123 displaced 84 and 58% of ET binding to capillaries from tumors and brains, respectively. In addition, competition curves obtained in the presence of increasing concentrations of ET-3 showed two components (IC50 = 5.7 ± 2.5 × 10?10 and 1.4 ± 0.2 × 10?6M for tumor microvessels, 1.8 ± 0.6 × 10?10 and 1.1 ± 0.3 × 10?6M for brain microvessels, respectively). Our results indicate that (a) the method we used is simple and highly sensitive for detecting and characterizing various receptors in tumor capillaries, especially in the case of a sparse specimen, and (b) capillaries in glioblastomas express specific high-affinity ET binding sites, candidates for biologically active ET receptors, which predominantly belong to the ETA subtype. 相似文献
30.