全文获取类型
收费全文 | 2611篇 |
免费 | 153篇 |
国内免费 | 1篇 |
专业分类
2765篇 |
出版年
2022年 | 19篇 |
2021年 | 25篇 |
2020年 | 15篇 |
2019年 | 16篇 |
2018年 | 27篇 |
2017年 | 34篇 |
2016年 | 48篇 |
2015年 | 82篇 |
2014年 | 126篇 |
2013年 | 184篇 |
2012年 | 155篇 |
2011年 | 152篇 |
2010年 | 105篇 |
2009年 | 88篇 |
2008年 | 133篇 |
2007年 | 184篇 |
2006年 | 162篇 |
2005年 | 140篇 |
2004年 | 185篇 |
2003年 | 156篇 |
2002年 | 173篇 |
2001年 | 38篇 |
2000年 | 42篇 |
1999年 | 37篇 |
1998年 | 44篇 |
1997年 | 34篇 |
1996年 | 27篇 |
1995年 | 29篇 |
1994年 | 28篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 16篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1975年 | 8篇 |
1973年 | 4篇 |
1966年 | 4篇 |
1965年 | 7篇 |
排序方式: 共有2765条查询结果,搜索用时 0 毫秒
1.
A low-pressure microwave-induced helium plasma serves as an excitation source for metal chlorides, nitrates, and sulfates vaporized from a filament, resulting in fractional vaporization and differential sensitivities of detection of the elements depending on the vapor pressures of their salts. The shapes of the single emission peaks, which are simple in the presence of potassium chloride, become complex and may double in number. 相似文献
2.
Summary Localization of kallikrein in the human kidney was investigated by two markers: kallikrein-like activity and kallikrein antigenicity. Kallikrein-like activity was demonstrated enzyme-histochemically by using a synthetic substrate for kallikrein, pro-phe-arg-naphthyl-ester. Kallikrein antigenicity was demonstrated by the unlabelled antibody peroxidase-antiperoxidase method using an antiserum against human urinary kallikrein. The kallikrein-like activity was localized in the proximal tubular cells without any corresponding kallikrein antigenicity. Neither kallikrein-like activity nor kallikrein antigenicity was noticed in any other tubular cell. These results are contrary to those in the ductal cells of the human parotid gland where the kallikrein-like activity and the kallikrein antigenicity were identical in their locations. The peroxidase-antiperoxidase method revealed, for the first time, kallikrein antigenicity both in the interstitium and in the basement membrane region of Bowman's capsule and of all the tubules, possibly representing circulating glandular kallikreins deposited in the renal tissue. Thus, the present findings are consistent with the hypothesis that the urinary (renal) kallikreins are derived from circulating glandular kallikreins. 相似文献
3.
Takashi Ariizumi Naomi Moriya Hideho Uchiyama Makoto Asashima 《Development genes and evolution》1991,200(4):230-233
Summary Human recombinant activin A, which is identical with erythroid differentiation factor (EDF), was tested for its mesoderm-inducing activity in concentrations from 0.3–50 ng/ml, using ectoderm of Xenopus late blastula (Stage 9) as the responding tissue. At a low concentration of activin A, blood-like cells, mesenchyme, and coelomic epithelium were induced; at a moderate concentration muscle and neural tissue, and at a high concentration notochord. Activin A thus induced all mesodermal tissues in a dose-dependent manner, such that a low dose induced ventral structures and a high dose induced dorsal structures. Activin may act as an intrinsic inducing molecule responsible for establishing the dorso-ventral axis in early Xenopus development.
Offprint requests to: M. Asashima 相似文献
4.
Takashi Saitoh Jun Osawa Toshikazu Takanishi Shintaro Hayakashi Masaaki Ohmori Toshio Morita Shigeru Uemura Jon Olav Vik Nils Chr. Stenseth Koji Maekawa 《Population Ecology》2007,49(3):249-256
The effects of the abundance of acorns of the oak, Quercus crispula, on the population dynamics of three rodent species (Apodemus speciosus, A. argenteus, and Clethrionomys rufocanus) were analyzed using time series data (1992–2006). The data were obtained in a forest in northern Hokkaido, Japan, by live
trapping rodents and directly counting acorns on the ground. Apodemus speciosus generally increased in abundance following acorn masting. However, the clear effect of acorn abundance was not detected for
the other two rodent species. Acorns of Q. crispula contain tannins, which potentially have detrimental effects on herbivores. Apodemus speciosus may reduce the damage caused by acorn tannins with tannin-binding salivary proteins and tannase-producing bacteria, whereas
such physiological tolerance to tannins is not known in the other two rodent species. The differences in the effects of acorns
between the three species may be due to differences in their physiological tolerance to tannins. 相似文献
5.
6.
Masatoshi Murayama Hirohito Hirata Makoto Shiraki Juan L. Iovanna Takayoshi Yamaza Toshio Kukita Toshihisa Komori Takeshi Moriishi Masaya Ueno Tadatsugu Morimoto Masaaki Mawatari Akiko Kukita 《Journal of cellular physiology》2023,238(3):566-581
Nuclear protein 1 (NUPR1) is a stress-induced protein activated by various stresses, such as inflammation and oxidative stress. We previously reported that Nupr1 deficiency increased bone volume by enhancing bone formation in 11-week-old mice. Analysis of differentially expressed genes between wild-type (WT) and Nupr1-knockout (Nupr1-KO) osteocytes revealed that high temperature requirement A 1 (HTRA1), a serine protease implicated in osteogenesis and transforming growth factor-β signaling was markedly downregulated in Nupr1-KO osteocytes. Nupr1 deficiency also markedly reduced HtrA1 expression, but enhanced SMAD1 signaling in in vitro-cultured primary osteoblasts. In contrast, Nupr1 overexpression enhanced HtrA1 expression in osteoblasts, suggesting that Nupr1 regulates HtrA1 expression, thereby suppressing osteoblastogenesis. Since HtrA1 is also involved in cellular senescence and age-related diseases, we analyzed aging-related bone loss in Nupr1-KO mice. Significant spine trabecular bone loss was noted in WT male and female mice during 6−19 months of age, whereas aging-related trabecular bone loss was attenuated, especially in Nupr1-KO male mice. Moreover, cellular senescence-related markers were upregulated in the osteocytes of 6−19-month-old WT male mice but markedly downregulated in the osteocytes of 19-month-old Nupr1-KO male mice. Oxidative stress-induced cellular senescence stimulated Nupr1 and HtrA1 expression in in vitro-cultured primary osteoblasts, and Nupr1 overexpression enhanced p16ink4a expression in osteoblasts. Finally, NUPR1 expression in osteocytes isolated from the bones of patients with osteoarthritis was correlated with age. Collectively, these results indicate that Nupr1 regulates HtrA1-mediated osteoblast differentiation and senescence. Our findings unveil a novel Nupr1/HtrA1 axis, which may play pivotal roles in bone formation and age-related bone loss. 相似文献
7.
The nymphal locomotion ability (walking distance) of the stenophagous bean bug Riptortus pedestris (Fabricius) was studied in each instar. We measured the walking distance using two systems. The walking distance in photophase was measured for 6 h using a tracking system with a charge coupled device (CCD) camera and computer software. The daily activity of nymphs was measured by an actograph system counting the number of infrared beam intercepts. The actograph data were converted to distance using a linear regression against the data of the tracking system. The longevity of nymphs without food was also studied to estimate the potential walking distance. Using both the tracking and actograph systems, it was determined that first instars walked less than the other instars (only 10.7 m within 6 h). The second to fifth instars could move 20-25 m within 6 h, and this distance did not differ among instar. This indicates that first instars seldom move after hatching in the field. The walking distance for 24 h varied and was greatest for the third instars (80.8 m). The potential longevity of nymphs was found to increase with instar age. Potential locomotion ability (walking distance for 24 hxpotential longevity) was high in the third to fifth instars (approximately 340 m). The potential locomotion ability for the second instars was relatively low compared with the elder instars (approximately 180 m). From these results, nymphs of R. pedestris seem to adapt by identifying feeding site locations after hatching and elder instars may be able to find a novel feeding site after the degradation of previous habitat. 相似文献
8.
Yoshinari Maeda Kiyoshi Yoshimura Hiroto Matsui Yoshitaro Shindo Takao Tamesa Yukio Tokumitsu Noriaki Hashimoto Yoshihiro Tokuhisa Kazuhiko Sakamoto Kouhei Sakai Yutaka Suehiro Yuji Hinoda Koji Tamada Shigefumi Yoshino Shoichi Hazama Masaaki Oka 《Cancer immunology, immunotherapy : CII》2015,64(8):1047-1056
9.
Naganawa A Matsui T Saito T Ima M Tatsumi T Yamamoto S Murota M Yamamoto H Maruyama T Ohuchida S Nakai H Kondo K Toda M 《Bioorganic & medicinal chemistry》2006,14(19):6628-6639
4-({2-[Isobutyl(phenylsulfonyl)amino]-5-(trifluoromethyl)phenoxy}methyl)benzoic acid (1) is a functional PGE2 antagonist selective for EP1 receptor subtype. Analogs of 1, in which the phenyl-sulfonyl moiety has been replaced with more hydrophilic heteroarylsulfonyl moieties, exhibited more optimized antagonist activity, while some of them showed in vivo antagonist activity. Structure-activity relationship (SAR) studies are also presented. 相似文献
10.
Takahide Hayano Yuki Yokota Kazuyoshi Hosomichi Hirofumi Nakaoka Kosuke Yoshihara Sosuke Adachi Katsunori Kashima Hitoshi Tsuda Takuya Moriya Kenichi Tanaka Takayuki Enomoto Ituro Inoue 《PloS one》2014,9(12)
High-grade serous ovarian cancer (HGSOC) is the most aggressive histological type of epithelial ovarian cancer, which is characterized by a high frequency of somatic TP53 mutations. We performed exome analyses of tumors and matched normal tissues of 34 Japanese patients with HGSOC and observed a substantial number of patients without TP53 mutation (24%, 8/34). Combined with the results of copy number variation analyses, we subdivided the 34 patients with HGSOC into subtypes designated ST1 and ST2. ST1 showed intact p53 pathway and was characterized by fewer somatic mutations and copy number alterations. In contrast, the p53 pathway was impaired in ST2, which is characterized by abundant somatic mutations and copy number alterations. Gene expression profiles combined with analyses using the Gene Ontology resource indicate the involvement of specific biological processes (mitosis and DNA helicase) that are relevant to genomic stability and cancer etiology. In particular we demonstrate the presence of a novel subtype of patients with HGSOC that is characterized by an intact p53 pathway, with limited genomic alterations and specific gene expression profiles. 相似文献