全文获取类型
收费全文 | 2526篇 |
免费 | 155篇 |
国内免费 | 2篇 |
出版年
2023年 | 5篇 |
2022年 | 11篇 |
2021年 | 31篇 |
2020年 | 15篇 |
2019年 | 22篇 |
2018年 | 63篇 |
2017年 | 27篇 |
2016年 | 42篇 |
2015年 | 75篇 |
2014年 | 99篇 |
2013年 | 168篇 |
2012年 | 171篇 |
2011年 | 153篇 |
2010年 | 129篇 |
2009年 | 114篇 |
2008年 | 154篇 |
2007年 | 191篇 |
2006年 | 179篇 |
2005年 | 145篇 |
2004年 | 155篇 |
2003年 | 138篇 |
2002年 | 166篇 |
2001年 | 28篇 |
2000年 | 23篇 |
1999年 | 33篇 |
1998年 | 42篇 |
1997年 | 30篇 |
1996年 | 29篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 21篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 12篇 |
1986年 | 4篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1975年 | 5篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
排序方式: 共有2683条查询结果,搜索用时 31 毫秒
31.
Shinya Arinaga Nobuya Karimine Masashi Adachi Hiroshi Inoue Shigeru Nanbara Tsukasa Asoh Hiroaki Ueo Tsuyoshi Akiyoshi 《Cancer immunology, immunotherapy : CII》1993,37(4):220-226
We previously found that the ability of peripheral blood mononuclear cells (PBM) of cancer patients to generate lymphokine-activated killer (LAK) cells became remarkably augmented after mitomycin C administration. On the basis of the clinical finding, we designed a treatment regimen comprised of 12 mg/m2 mitomycin C i. v. on day 1 and 700 U/m2 recombinant interleukin-2 (IL-2) i.v. every 12 h from day 4 through day 8. Of 25 patients with advanced carcinoma, 9 had a partial response and 3 had a minor response. Cytotoxic cell function, including natural killer activity, lymphokine-activated killer (LAK) activity, and the ability to generate LAK cells, and lymphocyte subsets in PBM was measured 1 day before and after either the first or second course of this therapy. The relationship between these parameters and the clinical antitumor response to this treatment was examined. Although the cytotoxic activities were significantly augmented after either the first or second treatment course, no positive correlation was observed between the changes in these cytotoxic activities and the clinical response to this therapy, when patients who either showed a partial response or whose disease remission was partial or minor were defined as responders. Further, phenotypic analysis showed a significant increase in CD2+, CD3+ CD4+ and CD4+Leu8– cells after the firs course, and CD25+ cells after either the first or second course of this treatment. The precentages of CD2+ and CD25+ cells were significantly elevated only in responders but not in nonresponders, suggesting the increase in these subsets was related to clinical response. 相似文献
32.
Dispersal propensity of green leafhoppers was compared between a tropical species, Nephotettix virescens, and a temperate species, N. cincticeps. The flight ability was measured with tethered flight technique under laboratory conditions (25°C, 16L-8D). The pre-flight period was shorter and the flight duration was longer in N. virescens than in N. cincticeps in both sexes. No significant correlations were found between the flight activity and morphometric characters for either of the two species. The results suggested that dispersal propensity of N. virescens is higher than that of N. cincticeps. 相似文献
33.
Ota Yoko; Ario Takeshi; Hayashi Koji; Nakagawa Tsuyoshi; Hattori Tsukaho; Maeshima Masayoshi; Asahi Tadashi 《Plant & cell physiology》1992,33(3):225-232
Catalases purified from endosperm glyoxysomes and non-specializedmicrobodies from hypocotyls of castor bean seedlings differedin their specific activity [90164 and 0.894.9kunits (mg protein)1, respectively] and in their constituentsubunits [two subunits of 54 and 56 kDa for the endosperm enzymeand only one of 56 kDa for the hypocotyl enzyme]. Immunoblotanalysis also showed that particulate fractions from the endospermsand from etiolated and green cotyledons contained two catalasesubunits of 54 and 56 kDa, whereas such fractions from the hypocotylsand roots contained only the 56-kDa subunit. Leaf peroxisomesfrom green leaves had two catalase subunits of around 55 kDaeach. Results of translation in vitro indicated that the 54-and 56-kDa subunits were translated from distinct mRNAs andlevels of both mRNAs increased in the endosperms during germination,prior to increases in levels of catalase proteins. In the hypocotyls,the 56-kDa subunit seemed to be synthesized constitutively.
1Present addresses: YO, Toyota Central Institute, 31-9 Musashizuka,Nagabuchi, Nagakute, Aichi 480-11, Japan 相似文献
34.
35.
Suppression of Quantum Yield of Photosystem II by Hyperosmotic Stress in Chlamydomonas reinhardtii 总被引:1,自引:0,他引:1
Addition of ethylene glycol (EG) or NaCl to cells of Chlamydomonasreinhardtii induced transient non-photochemical quenching ofChl fluorescence correlated with the inhibition of photosyntheticoxygen evolution. The induction of the quenching and subsequentrecovery proceeded not only in the light but also in the dark.The quenching was almost unaffected by the protonophore nigericin,suggesting the involvement of a type of non-photochemical quenchingattributable to a state 2 transition. Higher concentrationsof EG or NaCl caused a delay of the recovery of the maximumfluorescence yield (Fm'). Dark reduction rate of P700+ afterthe application of a flash light in the presence of DCMU wasenhanced by the hyperosmotic shock, suggesting a stimulatedreduction of the intersystem electron carriers. It is proposedthat the osmotic stress stimulates electron donation from stromalcomponents via the NAD(P)H dehydrogenase, which results in thereduction of the intersystem chain and triggering of a state2 transition leading to stimulated cyclic PSI activity. (Received May 16, 1995; Accepted July 26, 1995) 相似文献
36.
Michio Masuda Tsuyoshi Abe Shinji Sato Teruaki Suzuki Minoru Suzuki 《Journal of phycology》1997,33(2):196-208
Many morphologically similar, but chemically distinct, populations have been found in the marine red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) growing in Japan. Each chemical type is characterized by a specific end-product of halogenated secondaly metabolite synthesis: chamigrane-type sesquiterpenoids such as prepacifenol and halochamigrene epoxide and C15 bromoethers such as laurencin, laureatin, isoprelaurefucin, epilaurallene, and kumausallene. These seven types of secondary metabolite syntheses remained the same in the wild and under various culture conditions. Because bromoethers and terpenoids are probably synthesized by different metabolic pathways, it is virtually certain that different sets of enzymes participate in their synthesis. Prepacifenol- and laureatin-producing populations were selected as representatives of terpenoid and bromoether groups, respectively. F1 tetrasporophytes derived from crosses between reciprocal, female and male gametophytes of prepacifenol- and laureatin-producing strains bore both types of metabolites, suggesting that the genes Producing these enzyme systems are encoded by nuclear genomes. The F1 gametophytes resulting from the reciprocal crosses produced either prepacifenol or laureatin, and the four individuals derived from spore tetrads (a set of tetraspores derived from a single tetrasporangium) produced either prepacifenol or laureatin in a 1:1 ratio, indicating that genes participating in terpenoid synthsis and those participating in bromoether synthesis are on different loci of homologous chromosomes and are segregated at meiosis (tetrasporogenesis). One individual of this interpopulational F1 gamtophyte produced both parental types of metabolite, perhaps indicating the occurrence of a recombination type. Natural hybrid individuals, including such recombination-type gametophytes, were found in a sympatric locality at which these two chemical types occur. F1 tetrasporophytes derived from crosses between respective prepacifenol- and laureatin-producing strains and their F1 gametohytes produced only parental-type metabolite-producing plants. These results indicate that the diverse chemical types can be referred to as races (chemical races). 相似文献
37.
A case of transient hypothyroidism in the course of hypokalemic myopathy is reported. A 69-year-old woman had severe muscle weakness and marked potassium deficiency associated with alkalosis during treatment with thiazide diuretics. The cause of muscle weakness proved to be hypokalemic myopathy confirmed by clinical findings and muscle biopsy. After the episode of hypokalemic myopathy, serum levels of thyroid hormone were lowered (T4; 3.8 micrograms/dl, T3; 54 ng/dl) and that of TSH was elevated (25.1 microU/ml). Antithyroid microsomal antibody was positive (1:25600) and anti-thyroglobulin antibody was negative. About one month after potassium supplement, her thyroid functions returned to normal, along with normalization of serum potassium level. This is the first documented case report of hypokalemic myopathy accompanied by transient hypothyroidism in a patient with autoimmune thyroiditis. We suggest that this transient hypothyroidism might be induced by hypokalemia during the course of autoimmune thyroiditis. 相似文献
38.
(+)-Abscisic acid was isolated as the methyl ester from Pinus densiflora pollen and identified spectroscopically. 相似文献
39.
Solvent-extractable lipids in Pinus densiflora pollen were investigated. The cis- and trans-isomers of 1,16-dioxo-, 1-hydroxy-16-oxo- and 1, 16-dihydroxyhexadecan-7-yl p-coumarates were identified. 相似文献
40.
Erythrocyte ghosts containing a known number of molecules of purified fragment A of diphtheria toxin with a constant amount of FITC-BSA as a fluorescence marker were prepared by dialyzing a mixture of erythrocytes and these substances against hypotonic solution. These substances were then introduced into diphtheria toxin-resistant mouse L cells by virus-mediated cell fusion of the cells with the ghosts, and mononuclear recipients that had fused with only one erythrocyte ghost were separated in a fluorescence-activated cell sorter (FACS) on the basis of their cell size and fluorescence intensity. After separation, the viability of cells containing known numbers of fragment A was examined by measuring colony-forming ability. The results demonstrated that a single molecule of fragment A was sufficient to kill a cell.This fact was confirmed by introduction into cells of fragment A from an immunologically related mutant toxin, CRM 176 (fragment A-176); this has a completely functional fragment B region, but in cell extracts, the enzymic activity of its fragment A is about 10 fold less than that of wild toxin. The cytotoxicity of CRM 176 is about two hundredths of that of the wild-type (Uchida, Pappenheimer and Greany, 1973). As expected, about 100–200 fold excess of fragment A-176 was needed to kill the cells. 相似文献