全文获取类型
收费全文 | 5660篇 |
免费 | 352篇 |
国内免费 | 2篇 |
出版年
2021年 | 62篇 |
2020年 | 33篇 |
2019年 | 69篇 |
2018年 | 46篇 |
2017年 | 71篇 |
2016年 | 104篇 |
2015年 | 165篇 |
2014年 | 205篇 |
2013年 | 307篇 |
2012年 | 322篇 |
2011年 | 333篇 |
2010年 | 186篇 |
2009年 | 214篇 |
2008年 | 314篇 |
2007年 | 307篇 |
2006年 | 268篇 |
2005年 | 271篇 |
2004年 | 268篇 |
2003年 | 295篇 |
2002年 | 254篇 |
2001年 | 155篇 |
2000年 | 152篇 |
1999年 | 121篇 |
1998年 | 80篇 |
1997年 | 59篇 |
1996年 | 65篇 |
1995年 | 63篇 |
1994年 | 50篇 |
1993年 | 51篇 |
1992年 | 96篇 |
1991年 | 94篇 |
1990年 | 88篇 |
1989年 | 64篇 |
1988年 | 62篇 |
1987年 | 64篇 |
1986年 | 51篇 |
1985年 | 34篇 |
1984年 | 56篇 |
1983年 | 34篇 |
1982年 | 34篇 |
1981年 | 31篇 |
1980年 | 27篇 |
1979年 | 38篇 |
1978年 | 35篇 |
1977年 | 31篇 |
1976年 | 32篇 |
1974年 | 33篇 |
1973年 | 31篇 |
1972年 | 29篇 |
1971年 | 28篇 |
排序方式: 共有6014条查询结果,搜索用时 15 毫秒
911.
Influence of body size on fecundity and sperm management in the parasitoid wasp Anisopteromalus calandrae
下载免费PDF全文
![点击此处可从《Physiological Entomology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A large body size is considered to be advantageous to the reproductive success of females as a result of several factors, such as the allocation of more resources to reproduction and the efficient management of sperm transferred by males. In the present study, the effects of female body size, female mating status and additional food availability on fecundity and the offspring sex ratio are investigated in the parasitoid wasp Anisopteromalus calandrae Howard (Hymenoptera: Pteromalidae). Because of haplodiploid sex determination, females must fertilize eggs to produce female offspring but not to produce male offspring. As predicted, female fecundity and the number of female offspring are positively correlated with body size. However, although the volume of the spermatheca increases with female body size, the amount of sperm stored in the spermatheca is relatively constant, irrespective of body size. Consequently, larger females produce a greater proportion of male offspring, especially at the end of the oviposition sequence, suggesting that larger females that possess more resources for reproduction and produce a larger number of offspring are more likely to suffer sperm depletion. The results of the present study also show that mated females have an increased fecundity compared with virgin females, although the opportunity to feed on honey along with host feeding has no impact upon fecundity or the sex ratio. 相似文献
912.
Hiroshi Abe Tadashi Morishita Masaaki Uchiyama Suguru Takatsuto Nobuo Ikekawa 《Bioscience, biotechnology, and biochemistry》2013,77(8):2171-2172
Microscopic and dynamic mechanical properties for mixed aqueous gels of agar and gelatin have been studied. The microscopic observation showed formation of micro granules in the gels under the phase-contrast visual field. The constituent was recognized as agar by metachroma tic staining using a microspectrophotometer. Dynamic moduli of the gels were measured from 0.01 to 200 Hz by phase difference and by resonance. A minimum E' value was obtained for the mixed gel at a volume fraction of agar of 0.6. E′ of all gels and E″ of mixed gels were frequency dependent above 30 Hz. 相似文献
913.
914.
H Kondo K Abe I Nishimura H Watanabe Y Emori S Arai 《The Journal of biological chemistry》1990,265(26):15832-15837
Oryzacystatin (oryzacystatin-I) is a proteinaceous cysteine proteinase inhibitor (cystatin) in rice seeds and is the first well defined cystatin of plant origin. In this study we isolated cDNA clones for a new type of cystatin (oryzacystatin-II) in rice seeds by screening with the oryzacystatin-I cDNA probe. The newly isolated cDNA clone encodes 107 amino acid residues whose sequence is similar to that of oryzacystatin-I (approximately 55% of identity). These oryzacystatins have no disulfide bonds, and so could be classified as family-I cystatins; however, the amino acid sequences resemble those of family-II members more than family-I members. Oryzacystatin-I and -II are remarkably distinct in two respects: 1) their specificities against cysteine proteinases; and 2) the expression patterns of their mRNAs in the ripening stage of rice seeds. Oryzacystatin-I inhibits papain more effectively (Ki 3.0 x 10(-8) M) than cathepsin H (Ki 0.79 x 10(-6) M), while oryzacystatin-II inhibits cathepsin H (Ki 1.0 x 10(-8) M) better than papain (Ki 0.83 x 10(-6) M). The mRNA for oryzacystatin-I is expressed maximally at 2 weeks after flowering and is not detected in mature seeds, whereas the mRNA for oryzacystatin-II is constantly expressed throughout the maturation stages and is clearly detected in mature seeds. Western blotting analysis using antibody to oryzacystatin-II showed that, as is the case with oryzacystatin-I, oryzacystatin-II occurs in mature rice seeds. Thus, these two oryzacystatin species are believed to be involved in the regulation of proteolysis caused by different proteinases. 相似文献
915.
Masahiro Maruoka Panpan Zhang Hiromi Mori Eiichi Imanishi Daniel M. Packwood Hiroshi Harada Hidetaka Kosako Jun Suzuki 《Molecular cell》2021,81(7):1397-1410.e9
- Download : Download high-res image (162KB)
- Download : Download full-size image
916.
917.
On the morphology of antennular sensory and attachment organs in cypris larvae of the deep‐sea vent/seep barnacles,Ashinkailepas and Neoverruca
下载免费PDF全文
![点击此处可从《Journal of morphology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Takefumi Yorisue Benny K. K. Chan Ryusuke Kado Hiromi Watanabe Koji Inoue Shigeaki Kojima Jens T. Høeg 《Journal of morphology》2016,277(5):594-602
Barnacle cypris larvae show high morphological variation in the organs used in search of and attaching to a substratum. This variation may represent adaptation to the habitat of the species. Here, we studied SEM level morphologies of cypris antennular sensory and attachment organs in a deep‐sea vent endemic species (Neoverruca sp.) and a vent/seep inhabiting species (Ashinkailepas seepiophila). We compare them with three species from other environments. The antennular morphologies of Neoverruca sp. and A. seepiophila were similar, which is consistent with recent molecular studies showing a close relationship of the two species. The setation pattern of the antennules was very conservative among species from various environments. In contrast, striking differences were observed in the structure of the attachment organ (the third antennular segment). Neoverruca sp. and A. seepiophila had no velum or a skirt surrounding the attachment disc on the third segment, while other cirripede cyprids almost always have either of these structures. In addition, both cyprids of A. seepiophila and Neoverruca sp. had the attachment disc angled toward the substratum, whereas it faces distally in cyprids from hard bottom inhabiting barnacles. We suggest that both velum/skirt and the angle of the attachment disc play an important role, when the antennules are contacting the substratum during surface exploration. Differences in attachment organ structures may be highly adaptive, enabling cirripede species to enter new habitats during evolution. J. Morphol. 277:594–602, 2016. © 2016 Wiley Periodicals, Inc. 相似文献
918.
Vitamin D binding protein ( GC ) and serum protease inhibitor ( PI ) have been added to genetic markers in the Japanese quail. Both loci were controlled by autosomal codominant alleles named GCA, GCB and PIA , PIB , PIC , respectively. Close linkage between the loci for serum albumin ( ALB ) and GC protein is reported. Two recombinants were observed in 145 informative offspring of 14 families. The recombination frequency between the loci was estimated as 0.014±0.006. Thus, GC was assigned to linkage group II in the Japanese quail. No signs of linkage were observed among the loci for the ALB-GC complex, PI. serum prealbumin 2 ( PA2 ), phosphoglucose isomerase ( PG1 ), 6-phosphogluconate dehydrogenase ( PGD ) and esterase-D ( ESD ). 相似文献
919.
Yuki Kanase Takafumi Kitada Hidetsugu Tabata Kosho Makino Tetsuta Oshitari Hiromi Ohashi Takashi Yoshinaga Hideaki Natsugari Hideyo Takahashi 《Bioorganic & medicinal chemistry》2018,26(9):2508-2513
The physicochemical properties of 4-substituted carbamazepine derivatives were investigated. It was elucidated that the 4-substitution is not effective in reducing the rotations (E/Z) about the N—C1′ axes around the outer carbamoyl moiety. However, the atropisomers were isolated with high stereochemical stability, meaning that the 4-substitution reduced the butterfly motion of the tricyclic ring system efficiently. The Cl/CH3-substituted carbamazepine derivatives showed greater inhibitory effects on hNav1.2 channel currents compared with carbamazepine, although no difference in the activity between enantiomers was observed. 相似文献
920.
Herein we review commercial bovine lactoferrin quality issues by describing an example of industrial production, the current status of global quality standardization, and quality-activity concerns for further discussion. Morinaga Milk Industry has been industrially producing bovine lactoferrin in Milei GmbH, Germany, since 1989. We delineate its production and quality as an example of safe and high-quality manufacturing. Currently, global standardization in the quality of bovine lactoferrin is progressing through Novel Food and GRAS in the EU and USA, respectively. Novel Food was applied or notified to seven lactoferrin manufacturers and GRAS was notified to three manufacturers, two of which are for infant use and one is for adult use, by the end of 2017. The specifications of these regulations are relatively high, including more than 95% lactoferrin purity in protein, which means that such companies can supply relatively high-grade lactoferrin. There appear to be several concerns regarding lactoferrin quality affecting activities, including contamination of lipopolysaccharide (LPS) and angiogenin, purity, and degradation of lactoferrin sample. Although LPS is immunologically toxic when invading the body, it is distributed normally in foods and the gut. However, an industrial lactoferrin sample may contain LPS at a maximum LPS/lactoferrin molecule ratio?=?1/1724, which means 99.9% of the lactoferrin molecule is LPS-free. It is difficult to speculate that LPS contained in a lactoferrin sample affects its activities. Finally in order to achieve good and reproducible results, we make proposals to researchers a use of high-grade lactoferrin, careful storage, and indication the manufacturers’ names and specifications in the paper. 相似文献