全文获取类型
收费全文 | 2338篇 |
免费 | 165篇 |
国内免费 | 1篇 |
专业分类
2504篇 |
出版年
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 21篇 |
2020年 | 12篇 |
2019年 | 23篇 |
2018年 | 33篇 |
2017年 | 45篇 |
2016年 | 60篇 |
2015年 | 63篇 |
2014年 | 92篇 |
2013年 | 128篇 |
2012年 | 135篇 |
2011年 | 144篇 |
2010年 | 95篇 |
2009年 | 98篇 |
2008年 | 132篇 |
2007年 | 141篇 |
2006年 | 156篇 |
2005年 | 142篇 |
2004年 | 156篇 |
2003年 | 162篇 |
2002年 | 166篇 |
2001年 | 37篇 |
2000年 | 35篇 |
1999年 | 40篇 |
1998年 | 38篇 |
1997年 | 34篇 |
1996年 | 25篇 |
1995年 | 22篇 |
1994年 | 23篇 |
1993年 | 23篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1972年 | 7篇 |
排序方式: 共有2504条查询结果,搜索用时 0 毫秒
101.
Nakahara Y Watanabe M Fujita A Kanamori Y Tanaka D Iwata K Furuki T Sakurai M Kikawada T Okuda T 《Journal of insect physiology》2008,54(8):1220-1225
Strategies to combat desiccation are critical for organisms living in arid and semi-arid areas. Larvae of the Australian chironomid Paraborniella tonnoiri resist desiccation by reducing water loss. In contrast, larvae of the African species Polypedilum vanderplanki can withstand almost complete dehydration, referred to as anhydrobiosis. For successful anhydrobiosis, the dehydration rate of P. vanderplanki larvae has to be controlled. Here, we desiccated larvae by exposing them to different drying regimes, each progressing from high to low relative humidity, and examined survival after rehydration. In larvae of P. vanderplanki, reactions following desiccation can be categorized as follows: (I) no recovery at all (direct death), (II) dying by unrepairable damages after rehydration (delayed death), and (III) full recovery (successful anhydrobiosis). Initial conditions of desiccation severely affected survival following rehydration, i.e. P. vanderplanki preferred 100% relative humidity where body water content decreased slightly. In subsequent conditions, unfavorable dehydration rate, such as more than 0.7 mg water lost per day, resulted in markedly decreased survival rate of rehydrated larvae. Slow dehydration may be required for the synthesis and distribution of essential molecules for anhydrobiosis. Larvae desiccated at or above maximum tolerable rates sometimes showed temporary recovery but died soon after. 相似文献
102.
Harada N Himeno A Shigematsu K Sumikawa K Niwa M 《Cellular and molecular neurobiology》2002,22(2):207-226
1. Interaction in the recognition of endothelin-1 (ET-1), a typical bivalent ET receptor-ligand, between ETA and ETB receptors was investigated in the rat anterior pituitary gland, using our quantitative receptor autoradiographic method with tissue sections preserving the cell-membrane structure and ET receptor-related compounds.2. In saturation binding studies with increasing concentrations (0.77–200 pM) of 125I-ET-1 (nonselective bivalent radioligand), 125I-ET-1 binding to the rat anterior pituitary gland was saturable and single with a K
D of 71 pM and a B
max of 120 fmol mg–1. When 1.0 M BQ-123 (ETA antagonist) was added to the incubation buffer, binding parameters were 8.3 pM of K
D and 8.0 fmol mg–1 of B
max, whereas 10 nM sarafotoxin S6c (ETB agonist) exerted little change in these binding parameters (K
D, 72 pM; B
max, 110 fmol mg–1).3. Competition binding studies with a fixed amount (3.8 pM) of 125I-ET-1 revealed that when 1.0 M BQ-123 was present in the incubation buffer, ETB receptor-related compounds such as sarafotoxin S6c, ET-3, IRL1620 (ETB agonist), and BQ-788 (ETB antagonist) competitively inhibited 125I-ET-1 binding with K
is of 140, 18, 350 pM, and 14 nM, respectively, however, these compounds were not significant competitors for 125I-ET-1 binding in the case of absence of BQ-123.4. In cold-ligand saturation studies with a fixed amount (390 pM) of 125I-IRL 1620 (ETB radioligand), IRL1620 bound to a single population of the ETB receptor, and no change was observed in binding characteristics in the presence of 1.0 M BQ-123. 125I-IRL1620 binding was competitively inhibited by ET-1 and ET-3 in the absence of BQ-123, with K
is of 20 and 29 pM, respectively, the affinities being much the same as those of 29 nM, in the presence of 1.0 M BQ-123.5. Two nonbivalent ETA antagonists, BQ-123 and PD151242, were highly sensitive and full competitors for 125I-ET-1 binding (5.0 pM), in the presence of 10 nM sarafotoxin S6c.6. Taken together with the present finding that mRNAs encoding the rat ETA and the ETB receptors are expressed in the anterior pituitary gland, we tentatively conclude that although there are ETA and ETB receptors with a functional binding capability for ET receptor-ligands, the ETB receptor does not independently recognize ET-1 without the aid of the ETA receptor. If this thesis is tenable, then ET-1 can bridge between the two receptors to form an ETA–ETB receptor heterodimer. 相似文献
103.
Mitinokuidrilus excavatus n. g., n. sp. is described from shallow subtidal coarse sands in northern Japan (NW Pacific). The species is characterized by a unique mode of sexual reproduction. Each of the two types of mature worms represents the opposite sex: "male" worms have testes, seminal vesicles, male ducts and small spermathecae; "female" individuals possess clitellum, ovaries, ovisac, female ducts and fully developed spermathecae. No mature worms with intermediate sexual condition were collected. The taxonomic position and the possibility of consecutive hermaphroditism of the present species are discussed. 相似文献
104.
Boerkoel CF Takashima H Stankiewicz P Garcia CA Leber SM Rhee-Morris L Lupski JR 《American journal of human genetics》2001,68(2):325-333
The periaxin gene (PRX) encodes two PDZ-domain proteins, L- and S-periaxin, that are required for maintenance of peripheral nerve myelin. Prx(-/-) mice develop a severe demyelinating peripheral neuropathy, despite apparently normal initial formation of myelin sheaths. We hypothesized that mutations in PRX could cause human peripheral myelinopathies. In accordance with this, we identified three unrelated Dejerine-Sottas neuropathy patients with recessive PRX mutations-two with compound heterozygous nonsense and frameshift mutations, and one with a homozygous frameshift mutation. We mapped PRX to 19q13.13-13.2, a region recently associated with a severe autosomal recessive demyelinating neuropathy in a Lebanese family (Delague et al. 2000) and syntenic to the location of Prx on murine chromosome 7 (Gillespie et al. 1997). 相似文献
105.
Fukuda T Uchida H Takashima Y Uwajima T Kawabata T Suzuki M 《Biochemical and biophysical research communications》2001,284(3):704-706
Degradation of bisphenol A (BPA), an endocrine-disrupting chemical, was studied with a purified laccase from the basidiomycete Trametes villosa. SDS--polyacrylamide gel electrophoresis of the purified laccase gave one single band with a mobility corresponding to MW 65 kDa. The absorption spectrum showed the characteristics of a blue copper protein with a maximum peak at 600 nm. HPLC analysis revealed that 2.2 micromol BPA were degraded by incubation with 1.5 units of the purified laccase in a total volume of 1.0 ml at pH 6.0 and 60 degrees C for 3 h. The enzyme reaction proceeded rapidly without requirement of mediators for the electron transfer. Isolation and identification of several reaction products are in progress, in which one product was identified as 4-isopropenylphenol by a gas chromatography--mass spectrophotometer. 相似文献
106.
107.
Plant clonality may greatly reduce effective population size and influence management strategies of rare and endangered species. We examined genetic diversity and the extent of clonality in four populations of the monotypic herbaceous perennial Japonolirion osense, which is one of the most rare flowering plants in Japan. Allozyme analysis revealed moderate levels of genetic variation, and the proportion of polymorphic loci (P=66.7%) was higher than the value for species with similar life-history traits. With four polymorphic loci, 19 multilocus genotypes were observed among 433 aerial shoot samples and 10 (52%) were found only in single populations. The proportion of distinguishable genotypes (PD=0.10) and Simpson's index of diversity (D=0.52) also exhibited moderate levels of genotypic diversity compared to other clonal plants, with genotype frequencies at Hardy-Weinberg equilibrium. The distributions of genotypes were often localized and they were mostly found within a radius of 5 m. Spatial autocorrelation analysis showed that shoot samples located 4 m apart were expected to be genetically independent. The results suggest that the spatial extent of genets was relatively narrow and thus the clonality was not extensive. 相似文献
108.
109.
Inoue M Sato EF Nishikawa M Hiramoto K Kashiwagi A Utsumi K 《Redox report : communications in free radical research》2004,9(5):237-247
Reactive oxygen species (ROS) are the major factors that induce oxidative modification of DNA and gene mutation. ROS can elicit oxidative stress and affect a wide variety of physiological and pathological processes including embryonal development, maturation and aging. 相似文献
110.
Katsuda S Yoshida M Saarinen N Smeds A Nakae D Santti R Maekawa A 《Experimental biology and medicine (Maywood, N.J.)》2004,229(5):417-424
Hydroxymatairesinol (HMR), obtained from the heartwood of spruce (Picea abies), has been demonstrated to exert chemo-preventive effects on the development of mammary tumors in rats. To examine the influence of HMR on uterine carcinogenesis, adult Donryu rats were initiated with a single intrauterine treatment of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) at 11 weeks of age and fed thereafter 0, 200, or 600 ppm HMR mixed in the soy-containing diet until 15 months of age. Incidences of uterine adenocarcinoma in both 200 and 600 ppm HMR-dosed groups were significantly reduced to 11% and 15%, respectively, less than 50% of 0 ppm, at the end of the experiment (P < 0.05). A delay in the start of persistent estrus by HMR was observed at 8 months of age compared with controls given carcinogen alone. From urinalysis, HMR was metabolized mainly to enterolactone and hydroxyenterolactone. These findings suggest that HMR or its metabolites exert chemo-preventive effects in the rat ENNG-uterine carcinogenesis model. 相似文献