全文获取类型
收费全文 | 5699篇 |
免费 | 648篇 |
国内免费 | 2篇 |
出版年
2021年 | 83篇 |
2020年 | 69篇 |
2019年 | 79篇 |
2018年 | 84篇 |
2017年 | 65篇 |
2016年 | 135篇 |
2015年 | 212篇 |
2014年 | 233篇 |
2013年 | 277篇 |
2012年 | 387篇 |
2011年 | 370篇 |
2010年 | 195篇 |
2009年 | 202篇 |
2008年 | 300篇 |
2007年 | 292篇 |
2006年 | 290篇 |
2005年 | 269篇 |
2004年 | 281篇 |
2003年 | 263篇 |
2002年 | 255篇 |
2001年 | 100篇 |
2000年 | 94篇 |
1999年 | 101篇 |
1998年 | 89篇 |
1997年 | 66篇 |
1996年 | 64篇 |
1995年 | 62篇 |
1994年 | 52篇 |
1993年 | 66篇 |
1992年 | 76篇 |
1991年 | 59篇 |
1990年 | 83篇 |
1989年 | 85篇 |
1988年 | 60篇 |
1987年 | 65篇 |
1986年 | 55篇 |
1985年 | 64篇 |
1984年 | 51篇 |
1983年 | 54篇 |
1982年 | 47篇 |
1981年 | 57篇 |
1980年 | 28篇 |
1979年 | 31篇 |
1978年 | 49篇 |
1977年 | 39篇 |
1976年 | 38篇 |
1975年 | 28篇 |
1974年 | 31篇 |
1973年 | 26篇 |
1972年 | 24篇 |
排序方式: 共有6349条查询结果,搜索用时 234 毫秒
1.
2.
In C4 plants phosphoenolpyruvate (PEP) of the C4 cycle may betransported on a chloroplast transporter which also transports3-phosphoglycerate (3-PGA) and triosephosphates. In C3 plantsPEP is not considered to be effectively transported on the chloroplastphosphate translocator. The influences of certain organic phosphates,having a similar structure to either PEP or triose-phosphates,on 3-PGA dependent O2 evolution by C4 (Digitaria sanquinalisL. Scop.) and C3 (Hordeum vulgare L.) mesophyll chloroplastswere investigated. In the C4 mesophyll chloroplasts phosphoglycolatewas a competitive inhibitor (Ki = 2.1 mM) of 3-PGA dependentO2 evolution, and was as effective as previously reported forPEP. 2-Phosphoglycerate was also a competitive inhibitor (Kt= 8.6 mM) of O2 evolution in the C4 mesophyll chloroplasts with3-PGA as substrate, while phospholactate was a weak inhibitorand glyphosate had no effect. Neither PEP, phosphoglycolatenor 2-phosphoglycerate were effective inhibitors of 3- PGA dependentO2 evolution in the C3 chloroplasts. Phosphohydroxypyruvatewas a competitive inhibitor of 3-PGA dependent O22 evolutionin both chloroplast types. The selectivity in inhibition ofO2 evolution with 3-PGA as substrate suggests that the C4 mesophyllchloroplasts can recognize certain organic phosphates with thephosphate in the C-2 or C-3 position but that the C4 mesophyllchloroplasts can only effectively recognize certain organicphosphates with the phosphate in the C-3 position. The resultsalso support the view that 3-PGA and PEP are transported onthe same phosphate translocator in C4 mesophyll chloroplasts.
1 Current address: Department of Horticulture, 2001 Fyffe Court,The Ohio State University, Columbus, Ohio 43210-1096. (Received March 24, 1987; Accepted April 16, 1987) 相似文献
3.
4.
Howard Marsh 《BMJ (Clinical research ed.)》1888,2(1450):805-807
5.
6.
7.
8.
Theo J. Visser Ellen Van Overmeeren-Kaptein 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,631(2):246-252
A radioimmunoassay for 3′-iodothyronine has been developed. All iodothyronine analogues (except 3,3′-diiodothyronine) showed very little (0.02% at most) cross-reactivity, and the assay was sensitive to 1 pg 3′-iodothyronine/ tube. We have studied the 5′-deiodination of 3′,5′-diiodothyronine by rat liver microsomal fraction in the presence of dithiothreitol. Production of 3′-iodothyronine at 37°C was found to be linear with time of incubation up to 30 min and with concentration of microsomal protein up to 100 μg/ml. The reaction rate reached a limit on increasing 3′,5′-diiodothyronine concentration to 10 μM. The effect of pH on 3′-iodothyronine production was found to depend on 3′,5′-diiodothyronine concentration. Increasing 3′,5′-diiodothyronine concentration from 0.1 to 10 μM resulted in a shift of the pH optimum from 6–6.5 to 7.5. Similar effects on the 5′-deiodination of 3,3′,5′-triiodothyronine were observed, supporting the hypothesis that these reactions are catalysed by a single enzyme (iodothyronine 5′-deiodinase). 相似文献
9.
10.
D J Marsh 《Federation proceedings》1983,42(8):2398-2404
The history of mathematical modeling of renal countercurrent systems is briefly outlined. Several examples are cited and discussed. These include efforts at parameter estimation and experimental design with models. The goal of this work was the evaluation of hypotheses of hypertonic urine formation. The argument is made that computer simulation with reasonably isomorphic models can be used in a variety of ways, but that one indispensable role for this approach is to provide a test of the quantitative sufficiency of hypotheses. Hypotheses of hypertonic urine formation that do not consider active transport in thin ascending limbs do not pass this test. A new proposal is suggested in which the energy for NaCl reabsorption from thin ascending limbs is derived from dissipation of a urea gradient via an antiport. 相似文献