全文获取类型
收费全文 | 1688篇 |
免费 | 152篇 |
国内免费 | 5篇 |
出版年
2023年 | 8篇 |
2022年 | 22篇 |
2021年 | 36篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2018年 | 41篇 |
2017年 | 20篇 |
2016年 | 37篇 |
2015年 | 84篇 |
2014年 | 80篇 |
2013年 | 111篇 |
2012年 | 117篇 |
2011年 | 110篇 |
2010年 | 73篇 |
2009年 | 84篇 |
2008年 | 106篇 |
2007年 | 85篇 |
2006年 | 81篇 |
2005年 | 86篇 |
2004年 | 88篇 |
2003年 | 89篇 |
2002年 | 75篇 |
2001年 | 11篇 |
1999年 | 13篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1978年 | 10篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1971年 | 10篇 |
1968年 | 11篇 |
1963年 | 7篇 |
1962年 | 8篇 |
1960年 | 6篇 |
排序方式: 共有1845条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Sheila Polakoff 《BMJ (Clinical research ed.)》1987,294(6578):1031-1032
5.
Isolation and expression of an anther-specific gene from tomato 总被引:31,自引:0,他引:31
David Twell Rod Wing Judy Yamaguchi Sheila McCormick 《Molecular & general genetics : MGG》1989,217(2-3):240-245
6.
Robert M. Levin Penelope A. Longhurst Sheila S. Levin Niels Haugaard Alan J. Wein 《Molecular and cellular biochemistry》1990,97(2):153-159
The urinary bladder depends on intracellular ATP for the support of a number of essential intracellular processes including contraction. The concentration of ATP is maintained constant primarily via the rapid transfer of a phosphate from creatine phosphate (CP) to ADP catalyzed by the enzyme creatine kinase (CK). Since muscular pathologies associated with diabetes are in part related to intracellular alterations in metabolism, we have characterized the CK activity in both skeletal muscle and urinary bladder from control and streptozotocin-diabetic rats.The following is a summary of the results: 1) Bladder tissue from control rats showed linear kinetics with a Vmax = 390 nmoles/mg protein/min, and a Km = 275 µM. 2) Urinary bladder tissue isolated from diabetic rats displayed biphasic kinetics with Vmax = 65 and 324 nmoles/mg protein/min, and Km's = 10 µM and 190 µM respectively. 3) Skeletal muscle isolated from control rats showed linear kinetics with an approximate Vmax of 800 nmoles/mg protein/min and a Km of 280 µM CP. 4) Homogenates of skeletal muscle from diabetic rats showed complex kinetics not separable into distict component forms. 5) The Km for ADP for both skeletal muscle and bladder was approximately 10 µM.These studies demonstrate that whereas bladders isolated from both control and diabetic rats possess a low-affinity isomer(s) of CK with similar maximum enzymatic activity, there is a high affinity isomer present within the urinary bladder muscle of diabetic rats that is not present in bladder tissue isolated from control rats. Skeletal muscle isolated from both diabetic and control rats exhibited a maximal activity 2 to 3 times higher than that of the bladder. 相似文献
7.
Sallie W. Chisholm Sheila L. Frankel Ralf Goericke Robert J. Olson Brian Palenik John B. Waterbury Lisa West-Johnsrud Erik R. Zettler 《Archives of microbiology》1992,157(3):297-300
Several years ago, prochlorophyte picoplankton were discovered in the N. Atlantic. They have since been found to be abundant within the euphotic zone of the world's tropical and temperate oceans. The cells are extremely small, lack phycobiliproteins, and contain divinyl chlorophyll a and b as their primary photosynthetic pigments. Phylogenies constructed from DNA sequence data indicate that these cells are more closely related to a cluster of marine cyanobacteria than to their prochlorophyte relatives Prochlorothrix and Prochloron. Several strains of this organism have recently been brought into culture, and herewith are given the name Prochlorococcus marinus. 相似文献
8.
Terry Ritchie Sheila A. Scully Jean de Vellis Ernest P. Noble 《Neurochemical research》1986,11(3):383-392
The enzymatic activities in post-mortem rat brain kept at 4°C and at 25°C were determined for a number of enzymes localized in specific cell types in the central nervous system. Choline acetyltransferase (CAT), glycerol-3-phosphate dehydrogenase (GPDH), glutamine synthetase (GS), lactate dehydrogenase (LDH) and 2,3-cyclic nucleotide phosphohydrolase (CNPase) were found to be very stable at both 4°C and 25°C with only slight, if any, losses of activity being seen even at periods as long as 72 hr. Glutamic acid decarboxylase (GAD) activity was less stable than that of the other enzymes. In brains kept at 4°C GAD activity was stable out to 24 hr after which it began to decline rapidly to 65% of control at 72 hr. In brains kept at 25°C, GAD activity was stable for 6–8 hr and then began to steadily decline to 58% of control at 24 hr and 29% of control at 72 hr. Assuming that these enzymes have similar stabilities in post-mortem human brain, the effect of post-mortem delay in processing tissues may be of lesser significance than other factors with regard to the measured enzyme activities in human brain samples. 相似文献
9.
Sheila McCormick Jeanne Niedermeyer Joyce Fry Arlene Barnason Robert Horsch Robert Fraley 《Plant cell reports》1986,5(2):81-84
The leaf disc transformation/regeneration system was modified for tomato (L. esculentum). Both leaf explants and cotyledon/hypocotyl sections can be used to regenerate transformed plants. We have obtained over 300 transgenic plants from eight tomato cultivars. We have evidence for both single and multi-copy insertions of the T-DNA, and have demonstrated inheritance of the T-DNA insert in the expected Mendelian ratios. Several heterologous promoters function in tomato. A reduced efficiency of transformation was observed with binary T-DNA vectors as compared to co-integrate T-DNA vectors. The ease of the leaf disc method makes tomato a premier experimental organism for plant biotechnology.Abbreviations BA
benzyl adenine
- IAA
indole acetic acid
- LB
Luria Broth 相似文献
10.
Clonal Analysis of Cell Division in the Bacillus subtilis div IV-B1 Minicell-Producing Mutant 总被引:8,自引:6,他引:2 下载免费PDF全文
Spores of the Bacillus subtilis minicell-producing mutant div IV-B1 were germinated and grown to microcolonies in chambers which facilitate continuous observation of the developing clones with a phase-contrast microscope. Time lapse photographs were taken of 46 clones, covering the period from the beginning of outgrowth until at least two rounds of cell division had been completed. Cell lineages were constructed from contour length measurements of the photographs. These data include cell lengths, division site locations, and cell numbers in clones of various ages. From these data we have determined that the probability of a minicell being produced at any division by the div IV-B1 mutant is 0.31. The location of the abnormal division site which generates the first minicell produced in the outgrowing clone appears to be random with respect to the existing cell poles. In contrast, the location of the second abnormal division site, and hence the second minicell, is not random but rather occurs preferentially in proximity to the first minicell. This clustering of abnormal events suggests that division site location is related to pole age (generations), although other influences on minicell clustering cannot be ruled out at present. 相似文献