全文获取类型
收费全文 | 9819篇 |
免费 | 605篇 |
国内免费 | 6篇 |
专业分类
10430篇 |
出版年
2022年 | 39篇 |
2021年 | 84篇 |
2020年 | 43篇 |
2019年 | 62篇 |
2018年 | 100篇 |
2017年 | 99篇 |
2016年 | 131篇 |
2015年 | 208篇 |
2014年 | 249篇 |
2013年 | 600篇 |
2012年 | 470篇 |
2011年 | 479篇 |
2010年 | 298篇 |
2009年 | 302篇 |
2008年 | 459篇 |
2007年 | 517篇 |
2006年 | 464篇 |
2005年 | 470篇 |
2004年 | 461篇 |
2003年 | 440篇 |
2002年 | 440篇 |
2001年 | 355篇 |
2000年 | 361篇 |
1999年 | 305篇 |
1998年 | 157篇 |
1997年 | 142篇 |
1996年 | 101篇 |
1995年 | 107篇 |
1994年 | 93篇 |
1993年 | 97篇 |
1992年 | 230篇 |
1991年 | 180篇 |
1990年 | 168篇 |
1989年 | 187篇 |
1988年 | 171篇 |
1987年 | 130篇 |
1986年 | 133篇 |
1985年 | 123篇 |
1984年 | 109篇 |
1983年 | 86篇 |
1982年 | 55篇 |
1981年 | 57篇 |
1980年 | 69篇 |
1979年 | 64篇 |
1978年 | 66篇 |
1977年 | 56篇 |
1976年 | 46篇 |
1975年 | 45篇 |
1974年 | 53篇 |
1973年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Shiraishi Tomonori; Araki Miwa; Yoshioka Hirofumi; Kobayashi Issei; Yamada Tetsuji; Ichinose Yuki; Kunoh Hitoshi; Oku Hachiro 《Plant & cell physiology》1991,32(7):1067-1075
A pathogenic fungus of pea, Mycosphaerella pinodes, secretesa so-called "suppressor" in its pycnospore germination fluid.The suppressor blocks the defense responses and induces localsusceptibility (accessibility) in pea plants to agents thatare not pathogenic in pea. The suppressor nonspecifically inhibitsthe ATPase activity in plasma membranes prepared from pea, soybean,kidney bean, cowpea and barley plants. However, cytochemicalstudies by electron microscopy indicate that the suppressorspecifically inhibits the ATPase in pea cell membranes, butnot in those of four other plant species tested. That is, thespecificity of the suppressor appears at the cell and/or tissuelevel, but is not evident in vitro. Furthermore, the inhibitoryeffect of the suppressor is temporary because the ATPase activityrecovers 9 h after the treatment. A similar effect was observedafter inoculation with M. pinodes but not with a nonpathogenof pea, M. ligulicola. The role of the suppressor in host-parasitespecificity is discussed. (Received April 9, 1991; Accepted August 6, 1991) 相似文献
62.
Summary We have developed a bioreactor system for aerobic fermentation, using a new ceramic carrier APHROCELL which has a suitable shape for liquid and gas passage. In acetic acid fermentation byAcetobacter cells from ethanol, as a typical example of aerobic fermentation, a productivity of 17.25 g/l h was attained at continuous production of 23 g-acetic acid/l; at an acetic acid concentration around 53 g/l, the productivity was 6.4 g/l h. Thus a marketable vinegar can be obtained continuously by this bioreactor system. Because of the simplicity of the APHROCELL reactor, scale up should be relatively easy. 相似文献
63.
K Tateishi Y Miura T Madarame T Yoshida K Suzuki N Takeichi H Kobayashi Y Matsuoka S Sato 《Regulatory peptides》1991,35(2):95-101
Levels of cholecystokinin (CCK) immunoreactivity and distribution of CCK immunoreactive cells were studied in the cerebral cortex of LEC (Long Evans Cinnamon) rats with hepatic encephalopathy. CCK immunoreactivity in water extract of cerebral cortex of LEC rats with hepatic encephalopathy (n = 7) was 41.5 +/- 2.6 (mean +/- S.E.M. pmol/g wet wt.) and that of LEC rats without encephalopathy (n = 8) was 67.1 +/- 6.9, the difference being significant (P less than 0.01). CCK immunoreactive cells assessed by immunohistochemistry were also markedly decreased in the cortex of LEC rats with hepatic encephalopathy of stage IV. Thus, CCK reduction was observed in the cerebral cortex of LEC rats with hepatic encephalopathy which are provided as a model for analysis of the pathogenesis of acute hepatic encephalopathy. 相似文献
64.
N Sakai J Tamaoki K Kobayashi T Kanemura K Isono K Takeyama S Takeuchi T Takizawa 《Regulatory peptides》1991,34(1):33-41
We studied the effect of vasoactive intestinal peptide (VIP) on ciliary activity in rabbit cultured tracheal epithelium by a photoelectric method in vitro. Administration of VIP (10(-7) M) elicited an increase in ciliary beat frequency (CBF) from the baseline values of 970 +/- 52 to 1139 +/- 75 beats/min (mean +/- S.E., P less than 0.01). This ciliostimulatory effect was dose-dependent, with the maximal increase and EC50 value being 17.4 +/- 1.0% (P less than 0.05) and 6.10(-11) M, respectively. The VIP-induced increase in CBF was abolished by pretreatment of cells with [4-Cl-D-Phe6, Leu17]-VIP, a VIP receptor antagonist. The neutral endopeptidase inhibitor phosphoramidon (10(-5) M) potentiated the effect of VIP, so that the CBF dose-response curve for VIP was shifted to lower concentrations by 0.5 log U. The administration of VIP increased cyclic AMP levels in epithelial cells, an effect that was also potentiated by phosphoramidon. These results suggest that VIP may interact with its specific receptors and stimulate airway ciliary activity probably through the activation of adenylate cyclase, and that neutral endopeptidase may play a role in modulating this effect of VIP. 相似文献
65.
Requirement of c-kit for development of intestinal pacemaker system. 总被引:65,自引:0,他引:65
H Maeda A Yamagata S Nishikawa K Yoshinaga S Kobayashi K Nishi S Nishikawa 《Development (Cambridge, England)》1992,116(2):369-375
A discovery that the protooncogene encoding the receptor tyrosine kinase, c-kit, is allelic with the Dominant white spotting (W) locus establishes that c-kit plays a functional role in the development of three cell lineages, melanocyte, germ cell, and hematopoietic cell which are defective in W mutant mice. Recent analyses of c-kit expression in various tissues of mouse, however, have demonstrated that c-kit is expressed in more diverse tissues which are phenotypically normal in W mutant mice. Thus, whether or not c-kit expressed outside the three known cell lineages plays a functional role is one of the important questions needing answering in order to fully elucidate the role of c-kit in the development of the mouse. Here, we report that some of the cells in smooth muscle layers of developing intestine express c-kit. Blockade of its function for a few days postnatally by an antagonistic anti-c-kit monoclonal antibody (mAb) results in a severe anomaly of gut movement, which in BALB/c mice produces a lethal paralytic ileus. Physiological analysis indicates that the mechanisms required for the autonomic pacing of contraction in an isolated gut segment are defective in the anti-c-kit mAb-treated mice, W/Wv mice and even W/+ mice. These findings suggest that c-kit plays a crucial role in the development of a component of the pacemaker system that is required for the generation of autonomic gut motility. 相似文献
66.
N. Maruo Y. Kobayashi H. Horiuchi M. Kondo S. Fujita 《Histochemistry and cell biology》1992,97(2):141-145
Summary A microcytofluorometrical DNA measurement was basically studied and was applied to single megakaryocytes previously identified on a Wright-Giemsa stained smear. The smear was first photographed and the location of each megakaryocyte was recorded on a cell map. The smear was then bleached with 50% acid ethanol and absolute methanol, and re-stained with 4,6-diamidino-2-phenylindole (DAPI) reagent (pH 7.4) at 4° C. Nuclear blue fluorescence was observed and the intensity of this fluorescence was proportional to the amount of DNA with the coefficient of variation (CV) of 3.6% when stained for 30 min. After 30 min DAPI staining, the DNA measurement was microcytofluorometrically performed in single megakaryocytes which had been morphologically classified into 4 groups on the basis of cytoplasmic maturation, Bessis' classification, assessed on Wright-Giemsa-stained bone-marrow smears from normal human beings. The histograms of the cells did not show any difference in DNA ploidy distribution among the classes: that is, the DNA histograms disclosed ploidy distribution from 4 N to 64 N with the largest population of 16 N. These findings suggest that nuclear DNA synthesis is completed before platelet production starts. This method is useful for comparing the morphological features and DNA content of single megakaryocytes. 相似文献
67.
Masato Terasawa Masayuki Inui Yasukazu Uchida Miki Kobayashi Yasurou Kurusu Hideaki Yukawa 《Applied microbiology and biotechnology》1991,34(5):623-627
Summary The application of an inducible regulation system using the trytophanase operon promoter (TPase promoter; Ptna) was examined for its high expression of the tryptophan synthase (TS) gene in Escherichia coli. The main problem in the application of Ptna for industrial purposes is catabolite repression by glucose, since glucose is the most abundant carbon source. However, this problem could be avoided by changing glucose to an organic acid, such as succinate, fumarate, malate and acetate, in the course of cultivation after glucose initially added was completely consumed. Under these conditions, l-tryptophan was also used to induce tryptophan synthase. Thus, the specific activity of TS in E. coli strain no. 168 harbouring pBR322F-PtnaTS was increased 500-fold compared to that of the cultured host strain. About 1 mol l-tryptophan/l reaction mixture was formed from indole and l-serine at 37° C for 3.5 h.
Offprint requests to: H. Yukawa 相似文献
68.
S X Zhang T Kobayashi T Okada E García del Saz H Seguchi 《Histology and histopathology》1991,6(3):309-315
The cerium-based method was used to demonstrate cytochemically the ultrastructural localization of alkaline phosphatase (ALPase), 5'-nucleotidase (5'-Nase) and magnesium-dependent adenosine triphosphatase (Mg-ATPase) on the transitional epithelium of the rat urinary bladder. The reaction product for ALPase was found on the plasma membrane of all epithelial cells, except the luminal surface of superficial cells. The activity of 5'-Nase appeared on the plasma membrane of all bladder transitional epithelial cells, including the free surface of superficial cells. The Mg-ATPase reaction product was seen on the plasma membrane of superficial, intermediate and basal cells, but never on the luminal surface of superficial cells and it was only occasionally seen on the basal surface. The possible functions of these phosphatases have been discussed, and it was emphasized that the 5'-Nase activity present on the luminal surface of superficial cells may play a special role in the membrane movement of these cells in the transitional epithelium. 相似文献
69.
Solution conformation of endothelin determined by means of 1H-NMR spectroscopy and distance geometry calculations 总被引:4,自引:0,他引:4
H Tamaoki Y Kobayashi S Nishimura T Ohkubo Y Kyogoku K Nakajima S Kumagaye T Kimura S Sakakibara 《Protein engineering》1991,4(5):509-518
The structure of endothelin-1 (ET-1), an endothelial cell-derived peptide with vasoconstricting activity, was determined in an aqueous solution by means of a combination of NMR and distance geometry calculations. The resulting structure is characterized by an alpha-helical conformation in the sequence region, Lys9-Cys15. Furthermore, an extended structure and a turn structure exist in the Cys1-Ser4 and Ser5-Asp8 regions respectively, and no preferred conformation was found for the C-terminal part of the peptide which was not uniquely constrained by the NMR data. These structural elements, the alpha-helical structure in the sequence portion, Cys-X-X-X-Cys, and the extended structure in Cys-X-Cys, are homologous to those found commonly in several neurotoxic peptides. 相似文献
70.
Tetsuo Kadota 《Cell and tissue research》1991,266(1):107-116
Summary Immunohistochemical techniques were used to study the distribution of serotonin in the central nervous system of the hagfish,Eptatretus burgeri, in order to produce a detailed map of serotonin-containing structures. In the hypothalamus, many serotonin-containing neurons contacted the cerebrospinal fluid. Most of the serotonin-containing cell bodies were located in the raphe region, where they were compactly distributed at the level of the nucleus motorius tegmenti pars anterior but more diffusely distributed at the level of the nucleus motorius tegmenti pars posterior. Serotonin-containing cell bodies and varicose fibers were widely distributed throughout the brain and upper spinal cord segments, but the distribution density was not even. On the basis of its abundance, serotonin can be judged to have an important function in the control of the hagfish central nervous system. From a phylogenetic point of view, serotonin-containing neurons in the raphe region appear to be a common property of all classes of vertebrates studied except the lampreys, whereas serotonin-containing cerebrospinal fluid-contacting neurons may be considered to be a primitive condition in all nonmammalian vertebrates. 相似文献