全文获取类型
收费全文 | 110439篇 |
免费 | 18969篇 |
国内免费 | 11篇 |
专业分类
129419篇 |
出版年
2023年 | 501篇 |
2022年 | 617篇 |
2021年 | 1544篇 |
2020年 | 3133篇 |
2019年 | 4646篇 |
2018年 | 5766篇 |
2017年 | 5627篇 |
2016年 | 6439篇 |
2015年 | 7304篇 |
2014年 | 7120篇 |
2013年 | 8698篇 |
2012年 | 7447篇 |
2011年 | 6551篇 |
2010年 | 6231篇 |
2009年 | 4275篇 |
2008年 | 4749篇 |
2007年 | 4142篇 |
2006年 | 4111篇 |
2005年 | 3529篇 |
2004年 | 3491篇 |
2003年 | 3133篇 |
2002年 | 2893篇 |
2001年 | 2360篇 |
2000年 | 2182篇 |
1999年 | 1681篇 |
1998年 | 726篇 |
1997年 | 537篇 |
1996年 | 576篇 |
1995年 | 506篇 |
1992年 | 960篇 |
1991年 | 871篇 |
1990年 | 840篇 |
1989年 | 923篇 |
1988年 | 756篇 |
1987年 | 780篇 |
1986年 | 709篇 |
1985年 | 760篇 |
1984年 | 639篇 |
1983年 | 566篇 |
1979年 | 680篇 |
1978年 | 495篇 |
1977年 | 497篇 |
1975年 | 592篇 |
1974年 | 629篇 |
1973年 | 601篇 |
1972年 | 563篇 |
1971年 | 502篇 |
1970年 | 539篇 |
1969年 | 618篇 |
1968年 | 580篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
931.
The purification of 3,3-dimethylallyl- and geranyl-transferase and of isopentenyl pyrophosphate isomerase from pig liver 总被引:8,自引:6,他引:2 下载免费PDF全文
The enzyme catalysing the synthesis of farnesyl pyrophosphate from dimethylallyl pyrophosphate and isopentenyl pyrophosphate, or from geranyl pyrophosphate and isopentenyl pyrophosphate, has been purified 100-fold from homogenates of pig liver. The enzyme has optimum pH 7.9 and requires Mg(2+) as activator in preference to Mn(2+); it is inhibited by iodoacetamide, N-ethylmaleimide, p-hydroxymercuribenzoate and phosphate ions in addition to the products of the reaction, inorganic pyrophosphate and farnesyl pyrophosphate. From product-inhibition studies of the geranyltransferase reaction, the order of addition of substrates to and release of products from the enzyme has been deduced: geranyl pyrophosphate combines with the enzyme first, followed by isopentenyl pyrophosphate. Farnesyl pyrophosphate dissociates from the enzyme before inorganic pyrophosphate. The existence of isopentenyl pyrophosphate isomerase in liver is confirmed. Methods for the preparation of the pyrophosphate esters of isopentenol, 3,3-dimethylallyl alcohol, geraniol and farnesol are also described. 相似文献
932.
Byl sledován vliv 6-benzylaminopurinu na dýchání pupen? jabloně odr?dy Boskooaké v pr?běhu 5 dn? po pod7#x00E1;ní kininu. Bylo zji?těno, ?e spot?eba kyslíku stanovovaná p?ímou metodou Warburgovou je vy??í ji? prvního dne po podání 6-benzylaminopurmu a stoupá stále výrazněji a? do pátého dne, kdy je spot?eba kyslíku u pupen? stimulovaných o 75% vy??í, ne? u pupen? kontrolních. 相似文献
933.
934.
Dagmar Vraná 《Folia microbiologica》1964,9(3):150-155
A modification of the synchronization method forChlorella pyrenoidosa was suggested, based on the mechanical separation of small and large cells by differential centrifugation and dilution of the population after division to a constant density (maximally 3×106 cells/ml.). Using this system, with a 16-hour day and eight hours' darkness, the ontogenetic cycle ofChlorella pyrenoidosa takes 24 hours and synchronous growth and development can be maintained for eight generations. 相似文献
935.
The use of induced primuline fluorescence led to the discovery of a new type of yeast scars (multiple scars) in the generaKloeckera, Saccharomycodes, Nadsonia andHanseniaspora. The structure and ultrastructure of their surface was studied by electron microscopy, using carbon replicas and isolated cell walls. 相似文献
936.
The strainCandida utilis T 20 adapted to a high concentration of ethionine, excretes considerable amounts of methionine in a synthetic medium, about 40 times as much as the original non-adapted strain. At the same time, the amount of methionine in yeast cells incrncreased, predominantly in the pool (9 times as much as in the control). This ability to produce greater amounts of methionine in the pool or to excrete it into the medium is not permanent, since after 5 passages on agar with ut ethionine the amount of methionine was practically not increased as compared with the original non-adapted strain. An increase in free methionine and of methionine excreted into the medium was found on cultivating the strain in a molasses-containing medium, too. 相似文献
937.
938.
Gábor Pálfi 《Planta》1967,78(2):196-199
Summary It has been established that in intact plants suffering from scarcity of water as well as in isolated withering leaves the amount of proline increases considerably. The main factor in the isolated leaves is thus the scarcity of water and not the injury due to the defoliation. The proline content of the leaves withering in the dark increases only for a few days and then decreases with the diminution of the carbohydrates. Of the active substances tested only 2,4-DNP inhibited the proline synthesis during the withering. It is very probable that in the course of withering the great amount of proline forms during the oxidation of carbohydrates via -ketoglutarate. The oxydative phosphorylation is uncoupled by 2,4-DNP. Kinetin, 2,4-D and antimetabolites applied do not inhibit the abnormal increase of proline. 相似文献
939.
Summary In monogenic, recessive chloroplast mutants of maize which contain chlorophylls, and lycopene or -carotene but no normal carotenoids, great variability in the size of plastids was associated with a number of ultrastructural abnormalities. In the mutant accumulating lycopene some plastids contain dense bundles of lamellae, whereas the chloroplasts of the -carotene mutant show poor thylakoid development. Neither of the mutants was able to form normal grana.A comparison of chlorophyll/carotenoid ratios in different chloroplast fractions of normal and mutant leaves showed that plastids of small size and delicate structure contain relatively less chlorophyll than fully differentiated chloroplasts. 相似文献
940.