全文获取类型
收费全文 | 5877篇 |
免费 | 305篇 |
国内免费 | 3篇 |
出版年
2022年 | 33篇 |
2021年 | 52篇 |
2020年 | 28篇 |
2019年 | 52篇 |
2018年 | 87篇 |
2017年 | 57篇 |
2016年 | 112篇 |
2015年 | 161篇 |
2014年 | 192篇 |
2013年 | 366篇 |
2012年 | 370篇 |
2011年 | 329篇 |
2010年 | 234篇 |
2009年 | 221篇 |
2008年 | 354篇 |
2007年 | 343篇 |
2006年 | 375篇 |
2005年 | 324篇 |
2004年 | 369篇 |
2003年 | 326篇 |
2002年 | 331篇 |
2001年 | 106篇 |
2000年 | 114篇 |
1999年 | 92篇 |
1998年 | 83篇 |
1997年 | 79篇 |
1996年 | 60篇 |
1995年 | 53篇 |
1994年 | 42篇 |
1993年 | 50篇 |
1992年 | 84篇 |
1991年 | 73篇 |
1990年 | 76篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 49篇 |
1986年 | 49篇 |
1985年 | 35篇 |
1984年 | 31篇 |
1983年 | 32篇 |
1982年 | 30篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 13篇 |
1976年 | 12篇 |
1975年 | 17篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1969年 | 13篇 |
排序方式: 共有6185条查询结果,搜索用时 15 毫秒
1.
S Imajoh H Kawasaki Y Emori K Suzuki 《Biochemical and biophysical research communications》1987,146(2):630-637
Endogenous inhibitors for calcium-activated neutral protease (CANP) were purified from rabbit erythrocytes and liver. The purified inhibitors showed single bands but with significantly different mobilities on sodium dodecylsulfate-polyacrylamide gel electrophoresis. Peptide mapping and sequencing analyses have revealed that the erythrocyte inhibitor (429 residues) retains the C-terminal three repetitive units of the liver inhibitor (639 residues), which contains four potential repetitive units for inhibition of CANP. The erythrocyte and liver inhibitors inhibited 3 and 4 moles of CANP on the basis of the molecular weights of 46,000 and 68,000, respectively. 相似文献
2.
Y Ishikawa K Kobayashi K Seki H Mizutani Y Kawasaki J Koike K Ijiri M Yamashita K Sugiura J Poynter T MacCallum G Anderson 《Biological Sciences in Space》1998,12(4):366-372
Several soluble components, peptidase and amino acids, and carbon isotopic ratio in the water retrieved from flight experiments of Autonomous Biological Systems (ABS) as well as ground control samples are analyzed to interpret the condition, dynamics, material balance of the ABS ecosystems. Organic carbons in flight samples were found to be more abundant compared with the control ones, which suggested the uniform ecosystems in low gravity might easily dissolve more soluble components. The Mir-1997 flight sample showed higher C/N ratio probably because of the dissolution of carbon-rich plant materials. 相似文献
3.
4.
Aminoglutethimide (AG: 750 mg/day) was administered to a patient with idiopathic hyperaldosteronism (IHA) and circadian rhythms in urinary excretion of sodium (UNaV), potassium (UKV), aldosterone (AER) and 17-OHCS were analyzed by the single cosinor method. Urine was collected every 4h for 24h on the day before and on the 1st, 3rd and 7th day of AG administration, and above variables in each sample were determined. Circadian rhythms of 14 patients with primary aldosteronism (PA) who served as controls were also analyzed. In the present case, circadian acrophases in UNaV and AER studied before AG administration occurred at 22(19) and 07(05), respectively. They were similar to those of preoperative PA-patients. Circadian acrophase in UNaV occurred earlier with AG administration and on the 7th day it was at 14(05), a value similar to that of postoperative PA-patients. Circadian mesor in AER decreased remarkably from 4.1 to 0.6 micrograms/4h with AG administration, as did circadian mesor in UKV, whereas circadian mesor and acrophase in 17-OHCS did not change. Thus, the circadian characteristics in urinary variables in the present IHA-case were pathophysiologically similar to those of PA. 相似文献
5.
6.
J K Steele H Kawasaki V K Kuchroo M Minami J G Levy M E Dorf 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(8):2629-2634
A monoclonal antibody (mAb), B16G, was raised from BALB/c mice immunized with affinity-purified T suppressor factors (TsF) specific for the murine mastocytoma P815. This mAb was found to bind to polyclonal TsF isolated from the spleens of tumor-bearing animals, and to the TsF released from a P815-specific T cell hybridoma. In this study, B16G was tested for its reactivity with TsF produced in the 4-hydroxy-3-nitrophenyl acetyl hapten system. The factors from three types of suppressor T cell hybridomas, each representing the immortalized analogues of the inducer T suppressor cell (Ts1), transducer suppressor cell (Ts2), and effector suppressor cell (Ts3) network populations, were tested. B16G was found to be reactive with two sources of TsF1 as assayed by enzyme-linked immunosorbent assay and delayed-type hypersensitivity bioassay. By contrast, TsF2 and TsF3 were nonreactive with B16G. These results indicate that B16G recognizes class-specific suppressor factor determinants, and that the transducer/effector factors of the network are apparently serologically distinct. Because the B16G mAb fails to recognize 4-hydroxy-3-nitro-phenyl acetyl-specific TsF3 that share idiotype-related determinants with TsF1 yet binds to TsF1 molecules that have interacted with antigen, the binding is apparently independent of the site of antigen recognition. Additionally, the results show that the tumor-specific TsF1 raised in one suppressor system share serologic determinants with anti-hapten TsF1 raised in another. 相似文献
7.
8.
The medium of 12-day-old culturs of tobacco cells (Nicotianatabacum L., var Xanthi; line XD-6S) contain c.a. 160mg/literof protein, of which 14% of the constituent ami no acids werefound to be hydroxyproline. By sequential column chromatographiesand CsCl density-gradient centrifugation, a basic hydroxyproline-richglycoprotein was purified from the medium and found to havean amino acid composition typical of extensin; with a high levelof hydroxyproline (33mole%), tyrosine (13%), and lysine (14%).The glycoprotein contained 42% (w/w) of sugars, among whicharabinose was the major component (85%). The proportion of thisextensin in the proteins in the culture medium was estimatedto be much higher than that of arabino-galactan protein (about5 times higher) on a protein basis, with extensin comprisingbetween 25% and 41%, and probably about 37% of the proteinsin the medium. (Received September 19, 1988; Accepted December 26, 1988) 相似文献
9.
10.
Went's classical experiment on the diffusion of auxin activity from unilaterally illuminated oat coleoptile tips (Went 1928), was repeated as precisely as possible. In agreement with Went's data with theAvena curvature assay, the agar blocks from the illuminated side of oat (Avena sativa L. cv. Victory) coleoptile tips had, on an average, 38% of the auxin activity of those from the shaded side. However, determination of the absolute amounts of indole-3-acetic acid (IAA) in the agar blocks, using a physicochemical assay following purification, showed that the IAA was evenly distributed in the blocks from the illuminated and shaded sides. In the blocks from the shaded and dark-control halves the amounts of IAA were 2.5 times higher than the auxin activity measured by theAvena curvature test, and in those from the illuminated half even 7 times higher. Chromatography of the diffusates prior to theAvena curvature test demonstrated that the amounts of two growth inhibitors, especially of the more polar one, were significantly higher in the agar blocks from the illuminated side than in those from the shaded side and the dark control. These results show that the basic experiment from which the Cholodny-Went theory was derived, does not justify this theory. The data rather indicate that phototropism is caused by the light-induced, local accumulation of growth inhibitors against a background of even auxin distribution, the diffusion of auxin being unaffected.Abbreviation IAA
indole-3-acetic acid 相似文献