全文获取类型
收费全文 | 1780篇 |
免费 | 110篇 |
国内免费 | 1篇 |
出版年
2022年 | 11篇 |
2021年 | 13篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 19篇 |
2016年 | 28篇 |
2015年 | 43篇 |
2014年 | 48篇 |
2013年 | 152篇 |
2012年 | 101篇 |
2011年 | 104篇 |
2010年 | 58篇 |
2009年 | 69篇 |
2008年 | 106篇 |
2007年 | 99篇 |
2006年 | 103篇 |
2005年 | 111篇 |
2004年 | 111篇 |
2003年 | 108篇 |
2002年 | 106篇 |
2001年 | 36篇 |
2000年 | 32篇 |
1999年 | 29篇 |
1998年 | 23篇 |
1997年 | 29篇 |
1996年 | 20篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 25篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 24篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1967年 | 5篇 |
1963年 | 4篇 |
排序方式: 共有1891条查询结果,搜索用时 31 毫秒
11.
K Yasui 《American journal of physical anthropology》1986,71(1):39-49
If the visual image and quantitative treatment of a form could be merged, the combination could become a powerful analytical method in morphology. A method is presented for creating an averaged outline. In this method, since the averaged outline is produced statistically, hypothesis testing can be performed on the visual image of the outlines. Intra- and intergroup variation of the outlines can then be assessed by taking allometry into account. This method is applied to the analysis of sexual differences in the midsagittal outline of recent (1880s-1920s) Japanese crania. The averaged outlines of both sexes showed subtle features that could not be detected by traditional measuring techniques. Because the roundness, flatness, or protrusion of specific aspects of the morphology are clearly apparent, sexual differences in this sample could be identified. Changes resulting from allometry did not seem to be present in either sex. The shape distance (DIR) introduced here matched well the visual impression derived from comparisons of the Japanese sample with a Jomon (Neolithic) male and the Broken Hill specimen. 相似文献
12.
Noritsugu Yabe Yutaka Matsuya Isao Yamane Mitsuru Takada 《In vitro cellular & developmental biology. Plant》1986,22(7):363-368
Summary A newly developed, serum-free medium (NYSF-404) selects for antibody-producing hybridomas after fusion of antigen-sensitized
mouse spleen cells with myeloma cell lines P3-X63-Ag8-U1 (P3-U1), P3-X63-Ag8-6.5.3 (Ag8.653), or P3-NSI/1-Ag4-1 (NS-1). Without
the need for hypoxanthine-aminopterinthymidine (HAT) selection of hybrid cells, frequency of hybridoma formation in medium
NYSF-404 is higher (twice) than that in serum- and HAT-containing medium. Colonies developed upon limiting dilution in the
presence of the mortal parent myeloma cells in medium NYSF-404 and pure culture of antibody-secreting cells could be subsequently
established. The results suggest that fusions can be done in serum-free medium and that the clonal growth of hybridomas is
dependent on factors produced by parent myeloma cells under serum-free culture conditions. Such factors seem deficient in
serum- and HAT-containing medium or are masked by serum. 相似文献
13.
Identification of a large interrupted helical domain of disulfide-bonded cartilage collagen 总被引:3,自引:0,他引:3
In order to characterize a larger form of disulfide-bonded cartilage collagen, explants of 17-day embryonic chick sterna were cultured in the presence of [3H] proline. Radioactive collagen chains and fragments that were synthesized and secreted into the culture medium were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. After limited pepsin digestion of the medium, two discrete disulfide-bonded collagen fragments were detected with Mr = 210,000 and 153,000. These fragments contained 28 and 17.5%, respectively, of the radioactivity in the alpha 1(II)-chains. The smaller fragment (called M) produced three components upon reduction (Mr = 104,000, 51,000, and 31,000) and seemed to represent the previously reported collagens, HMW and M1. The larger fragment (called N) has not been previously described and gave rise to three components upon reduction (Mr = 140,000, 69,000, and 49,000). Prolonged pepsin treatment resulted in the gradual decrease of N with a corresponding increase of M, suggesting the conversion of N to M. CNBr peptide mapping demonstrated that all M-derived peptides were present in N and that N contained extra peptides that account for its larger size. These observations suggest that N represents a larger more intact form of cartilage-derived disulfide-bonded collagen. 相似文献
14.
Transformation of L cells with virus thymidine kinase genes introduced by red cell-mediated microinjection 总被引:2,自引:0,他引:2
Takashi Iino Mitsuru Furusawa Iwao Furusawa Masuo Obinata 《Experimental cell research》1983,148(2):475-480
Fusion of red cell ghosts containing foreign materials with cells results in the introduction of the materials into the cells (red cell-mediated microinjection). Until now, 'two-step dialysis' has mainly been used for trapping proteins in the ghosts. Large-sized materials such as DNA, however, are rarely trapped in the ghosts, since the holes in the red cell membrane caused by osmotic shock are too small for such materials to pass through. In this study, we improved the trapping technique. Some of the Hind III fragments of lambda phage DNA as well as proteins could be trapped in the ghosts when the mixture of these materials and red cells were frozen at -80 degrees C for a short period followed by quick thawing. Red cell-mediated microinjection using ghosts containing plasmid pBR322 linked with a Herpes simplex viral thymidine kinase (tk) gene brought about transformation of tk-defective L cells, the efficiency of transformation was 1 out of 20 000-60 000 cells fused with the ghosts. 相似文献
15.
Yasuro Yoshimura Takayuki Kawano Mitsuru Kuroi Masaaki Morishita Masahiko Mori Kensaku Kawakatsu 《Histochemistry and cell biology》1970,22(4):337-346
Summary Analysis of lactate and malate dehydrogenase zymograms of rodent salivary glands showed species and organ specific patterns.Lactate dehydrogenase isoenzyme patterns occupied the middle positions in relation to those of skeletal and heart muscle. Activities of the major salivary glands were in the order submaxillary gland>parotid>sublingual gland. Zymogram of the mouse and rat showed LDH4 and LDH5 high activity patterns, while that of the rabbit was the fast moving active one. Hamster salivary gland exhibited a neutral type of the former and the latter.Malate dehydrogenase isoenzyme exhibited very similar patterns for the mouse, rat and hamster. Malate dehydrogenase zymogram of rabbit showed 3 active bands, which was different from the other rodents. 相似文献
16.
Effect of Ethanol on the Sodium and Potassium Conductances of the Squid Axon Membrane 总被引:8,自引:6,他引:2
下载免费PDF全文
![点击此处可从《The Journal of general physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The effects of ethanol on squid giant axons were studied by means of the sucrose-gap technique. The membrane action potential height is moderately reduced and the duration sometimes shortened by ethanol in sea water. Voltage clamp experiments showed that ethanol in sea water reduced the maximum membrane conductances for sodium (g'Na) and potassium (g'K). In experiments with multiple application of ethyl alcohol to the same spot of membrane, a reduction of g'Na to 82 per cent and of g'K to 80 per cent of their value in sea water was brought about by 3 per cent ethanol (by volume) while 6 per cent caused a decrease of g'Na to 59 per cent and of g'K to 69 per cent. Ethanol has no significant effect on the steady-state inactivation of gNa (as a function of conditioning membrane potential) or on such kinetic parameters as τh or the time course of turning on gi gNa and gK. It is concluded that ethanol mainly reduces gNa and gK in the Hodgkin-Huxley terminology. 相似文献
17.
K Osanai K Takahashi S Sato K Iwabuchi K Ohtake M Sata S Yasui 《Journal of applied physiology》1991,70(3):1300-1308
We investigated whether alveolar surface force increased and participated in the lung pressure-volume relationship in bleomycin-induced pulmonary fibrosis in hamsters and, if so, whether lung surfactant was hampered in the lungs. On the air-filled pressure-volume curve, decreases of lung volume from control level were significantly higher at 3-8 cmH2O pressure on day 10 than on day 30. Because the change of lung tissue elasticity evaluated from the saline-filled pressure-volume curve was equal for the 2 days, the higher decrease of air volume on day 10 was due primarily to contribution of alveolar surface force. Pressure differences between deflation limbs of air-filled and saline-filled pressure-volume curves, which represented net alveolar surface force, were significantly higher at any lung volume between 50 and 90% total lung capacity on day 10, but almost no significance was observed on day 30. Phospholipid concentration in bronchoalveolar lavage fluid significantly decreased on day 10 but had improved by day 30. Analysis of phospholipid species in purified lung surfactant showed decreased fractions of disaturated phosphatidylcholine and phosphatidylglycerol on day 10. Surface-active properties of the surfactant, measured by a modified Wilhelmy balance, were remarkably hampered on day 10, but most of them had improved by day 30. We consider that the quantitative and functional abnormalities of lung surfactant have a part in the aggravation of lung mechanics in the acute phase of pulmonary fibrosis. 相似文献
18.
19.
20.
Mitsuru Iwata Shoko Iwata Mark A. Everett Bryan B. Fuller 《In vitro cellular & developmental biology. Plant》1990,26(6):554-560
Summary A human foreskin organ culture system has been developed to study the response of human skin to hormonal stimulation. Foreskins
are maintained in culture on floating plastic supports which allows the epidermal surface to be exposed to air while the dermis
is bathed in nutrient medium. Both black and white human foreskins can be maintained in organ culture for at least 1 wk with
no change in the tissue structure or cell viability as determined by histochemical staining and by dopa reaction staining.
Tyrosinase activity in both black and white human foreskin cultures decays markedly during the first 2 d of culture to a new
steady state level which remains stable throughout the culture period. Both black and white foreskin cultures consistently
demonstrate 2- to 10-fold increases in tyrosinase activity when treated with theophylline (1 mM). Approximately 90% of all skin cultures examined showed an increase in enzyme activity when treated with this phosphodiesterase
inhibitor. Dibutyryl cAMP (0.1 mM) and [Nle4, D-phe7]-alpha MSH (10−8
M), were also found to markedly stimulate tyrosinase activity in some skin cultures, whereas alpha-MSH and prostaglandin E1 produced only an inconsistent and small increase in the activity of the enzyme. Histamine (1 μM), vitamin D3 (1 μM), and retinoic acid (1μM) failed to stimulate tyrosinase activity in either white or black foreskin cultures. This hormone-responsive organ culture
system can be utilized to characterize the molecular processes responsible for the regulation of tyrosinase and pigmentation
in human skin.
This work was supported by a research contract from the Oklahoma Center for the Advancement of Science and Technology (OCAST)
and by a research grant from the Presbyterian Health Foundation. 相似文献