全文获取类型
收费全文 | 6239篇 |
免费 | 355篇 |
国内免费 | 3篇 |
专业分类
6597篇 |
出版年
2022年 | 28篇 |
2021年 | 79篇 |
2020年 | 42篇 |
2019年 | 57篇 |
2018年 | 64篇 |
2017年 | 71篇 |
2016年 | 100篇 |
2015年 | 171篇 |
2014年 | 202篇 |
2013年 | 395篇 |
2012年 | 285篇 |
2011年 | 310篇 |
2010年 | 180篇 |
2009年 | 172篇 |
2008年 | 278篇 |
2007年 | 278篇 |
2006年 | 292篇 |
2005年 | 289篇 |
2004年 | 291篇 |
2003年 | 282篇 |
2002年 | 271篇 |
2001年 | 221篇 |
2000年 | 230篇 |
1999年 | 181篇 |
1998年 | 76篇 |
1997年 | 67篇 |
1996年 | 62篇 |
1995年 | 68篇 |
1994年 | 64篇 |
1993年 | 67篇 |
1992年 | 143篇 |
1991年 | 112篇 |
1990年 | 115篇 |
1989年 | 127篇 |
1988年 | 100篇 |
1987年 | 105篇 |
1986年 | 80篇 |
1985年 | 73篇 |
1984年 | 67篇 |
1983年 | 57篇 |
1982年 | 38篇 |
1981年 | 39篇 |
1980年 | 26篇 |
1979年 | 54篇 |
1978年 | 26篇 |
1977年 | 39篇 |
1976年 | 21篇 |
1975年 | 22篇 |
1974年 | 29篇 |
1973年 | 21篇 |
排序方式: 共有6597条查询结果,搜索用时 12 毫秒
991.
Atsushi Hayakawa Kazuo Kuwata Seiichi Era Masaru Sogami Hiroyuki Shimonaka Michio Yamamoto Shuji Dohi Hajime Hirose 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1997,698(1-2)
Human serum albumin is a mixture of mercapt- (HMA, reduced form) and nonmercaptalbumin (HNA, oxidized form). We studied the mercapt↔nonmercapt conversion of human serum albumin, which reflects the redox state of the extracellular fluids, in cardiac and other common surgical patients using high-performance liquid chromatography. Mean values of [(HMA)/(HMA + HNA)] ± standard deviation [fHMA ± σ], for patients who received common surgery (group 1) and cardiac surgery (group 2) at the start of anesthesia were0.636±0.50(n=83) and 0.615±0.062(n=14), respectively. fHMA values were markedly lower than those for healthy male adults of 0.750±0.028(n=28). fHMA values increased at 24 h after the start of anesthesia and decreased on the 4th postoperative day in most of the patients. These postoperative changes were prominent in surgical cardiac patients. Although fHMA values after the 7th postoperative day recovered to those at the start of anesthesia in almost all of common surgical patients, those in cardiac surgical patients, never recovered even on the 21st postoperative day. 相似文献
992.
Julia-Laurence Culioli Joséphine Foata Christophe Mori Antoine Orsini Bernard Marchand 《Acta zoologica》2004,85(4):245-256
Spermiogenesis in Castrada cristatispina begins with the formation of a zone of differentiation containing two centrioles with associated striated rootlets and an intercentriolar body between them. The centrioles give rise to two parallel, free flagella of the Trepaxonemata 9 + '1' pattern, growing out in opposite directions. Spermatids undergo a latero-ventral rotation of the flagella and a subsequent disto-proximal rotation of centrioles, and a distal cytoplasmic projection appears. The former rotation involves the compression of a row of microtubules and allows the recognition of a ventral side and a dorsal side. At the end of the differentiation, the centrioles and cortical microtubules lie parallel to the sperm axis. The modifications of the intercentriolar body and the migration of the nucleus and the centrioles toward the distal projection are described. The mature spermatozoon of C. cristatispina is filiform, tapered at both ends and shares several features with the other Rhabdocoela gametes. Nevertheless, the posterior extremity is capped by an electron-dense material. A gradient between mitochondria and dense bodies exists along the sperm axis. This study has enable us a phylogenetic approach of the Rhabdocoela through a comparison of the ultrastructural features of C. cristatispina with the other Rhabdocoela taxa. We propose the disto-proximal rotation of centrioles as a synapomorphy of the Rhabdocoela. 相似文献
993.
Seiichiro NAGAI Tadashi MABUCHI Shuji HIRATA Tomoko SHODA Tsuyoshi KASAI Sadaki YOKOTA Hiroshi SHITARA Hiromichi YONEKAWA Kazuhiko HOSHI 《Human cell》2004,17(4):195-202
Abstract Mitochondria play a central role to provide ATP for fertilization and preimplantation embryo development in the ooplasm. The mitochondrial dysfunction of oocyte has been proposed as one of the causes of high levels of developmental retardation and arrest that occur in preimplantation embryos generated using Assisted Reproductive Technology. Cytoplasmic transfer (CT) from a donor to a recipient oocyte has been applied to infertility due to dysfunctional ooplasm, with resulting pregnancies and births. However, neither the efficacy nor safety of this procedure has been appropriately investigated. In order to improve embryogenesis, we observed the mitochondrial distribution in ooplasma under the several conditions using mitochondrial GFP-transgenic mice (mtGFP-tg mice) in which the mitochondria are visualized by GFP. In this report, we will present our research about the mitochondrial distribution in ooplasm during early embryogenesis and the fate of injected donor mitochondria after CT using mtGFP-tg mice. The mitochondria in ooplasm from the germinal vesicle stage to the morula stage were accumulated in the perinuclear region. The mitochondria of the mtGFP-tg mouse oocyte transferred into the wild type mouse embryo could be observed until the blastocysts stage, suggesting that the mtGFP-tg mice oocyte is very useful for visual observation of the mitochondrial distribution in the oocyte, and that the aberrant early developmental competences due to the oocyte mitochondrial dysfunction may be overcome by transferring the "normal" mitochondria. 相似文献
994.
Shuji KANEKO 《Entomological Science》2004,7(4):331-339
Within‐shoot vertical distributions of the scale insect Nipponaclerda biwakoensis, five species of gregarious parasitoid wasps attacking the scale, and successful multiparasitism (emergence of multiple parasitoid species from a single host) by the parasitoids on the common reed were investigated. Each reed shoot collected was longer than 2.0 m, and was divided into pieces of 0.5 m each from the base of the shoot. The mean number of adult female scales per 0.5 m of shoot increased with height, but the mean rate of overall parasitism of the female scales decreased with height. The five parasitoids showed species‐specific within‐shoot distribution patterns, with respect to the rate of parasitism: Astymachus japonicus, Boucekiella depressa and Encyrtidae sp. 2 showed the greatest rates of parasitism at heights of 0–0.5, 0.5–1.0 and 1.0–1.5 m, respectively. The parasitism rate by Aprostocetus sp. was higher at the lower half of the shoots, whereas that by Encyrtidae sp. 1 was higher at the central positions. The distribution of the five parasitoids largely overlapped with each other at the level of scale aggregations. Nevertheless, successful multiparasitism occurred frequently only in several types of species combinations that involved two parasitoid species showing similar within‐shoot distribution patterns. The rate of successful multiparasitism by B. depressa with A. japonicus or Aprostocetus sp., and that by Encyrtidae sp. 2 with Encyrtidae sp. 1 was constantly high at different vertical positions on the shoots. This may be because B. depressa and Encyrtidae sp. 2 preferentially oviposit into scales previously parasitized by these other species. 相似文献
995.
996.
997.
Reinhard Pinontoan Takashi Yuasa† ‡ Marinela I. Anderca Takashi Matsuoka Nobuyuki Uozumi Hitoshi Mori Shoshi Muto 《Journal of phycology》2000,36(3):545-552
A cDNA clone encoding a Ca2 +-dependent protein kinase (DtCPK1) with a calculated molecular mass of 65,746 Da was isolated by sequential immuno- and hybridization-screening from a cDNA library of the halotolerant green alga, Dunaliella tertiolecta Butcher (Chlorophyceae). Primary structure analysis of DtCPK1 revealed a long variable domain preceding a catalytic domain, an autoinhibitory junction domain, and a C-terminal calmodulin-like domain containing 4 EF-hand motifs. Database searches showed that DtCPK1 has a high similarity to CCK1 , a CDPK from the green alga, Chlamydomonas eugamentos Moewus . The N-terminal long variable domain of DtCPK1 contains neither the N-myristoylation motif, which is found in many CDPKs, nor the PEST motif, which is associated with rapid protein turnover and found in one CDPK subfamily. However, a putative Ca2 +-dependent lipid binding domain that might be responsible for the association of cytosolic DtCPK1 with the cell membrane was identified in the variable domain. Three CDPKs, with molecular masses of 62, 54, and 47 kDa respectively, were observed in an in-gel protein kinase assay of D. tertiolecta cells extract. No change in the activities of these CDPKs were observed for up to 30 min after D. tertiolecta cells had been subjected to a hypoosmotic shock. An antibody raised against a CDPK purified from D. tertiolecta and used to isolate the DtCPK1 cDNA clone cross-reacted strongly with the 62-kDa CDPK but weakly with the 54-kDa CDPK in a Western blot, indicating that the 62-kDa CDPK is identical to DtCPK1. There was no change in the intensity of these bands after hypoosmotic shock, implying that the cellular level of the enzyme protein is not associated with hypoosmotic shock. These results indicate that CDPK is activated only by the increase in cytosolic-free Ca2 + concentration in vivo . 相似文献
998.
Nobuhiko Watanabe Hiroshi Nakagawa Shuji Kitajima Enqi Liu Masatoshi Morimoto Teruo Watanabe Jianglin Fan 《Experimental Animals》2005,54(4):353-357
In the present study, embryo transfer was performed using frozen-thawed embryos to establish a SPF colony of human apolipoprotein (a) (apo(a)) transgenic rabbits. Apo(a) transgenic rabbits were kept under conventional condition and were infected with Bordetella bronchiseptica. Embryos at the morula stage were collected and stored in liquid nitrogen. After thawing, the in vitro survival rate was 84.6%, and 125 morphologically normal embryos were transferred to 6 SPF recipient rabbits. Four rabbits became pregnant and 23 live pups were born. PCR and Western blot analyses revealed that 9 of 23 pups were transgenic and expressed apo(a) protein. Microbiological tests showed all rabbits were free from infections. We succeeded in establishing a SPF colony of apo(a) transgenic rabbits. These rabbits are now maintained under a barrier system and are available for medical research. 相似文献
999.
Celina M Haraguchi Tadashi Mabuchi Shuji Hirata Tomoko Shoda Kazuhiko Hoshi Kenji Akasaki Sadaki Yokota 《The journal of histochemistry and cytochemistry》2005,53(4):455-465
We investigated the localization of several markers for lysosomes and aggresomes in the chromatoid bodies (CBs) by immunoelectron microscopy. We found so-called aggresomal markers such as Hsp70 and ubiquitin in the core of the CBs and vimentin and proteasome subunit around the CBs. Ubiquitin-conjugating enzyme (E2) was also found in the CBs. In tubulovesicular structures surrounding the CBs, lysosomal markers were detected but an endoplasmic reticulum retention signal (KDEL) was not. Moreover, proteins located in each subcellular compartment, including the cytosol, mitochondria, and nucleus, were detected in the CBs. Signals for cytochrome oxidase I (COXI) coded on mitochondrial DNA were also found in the CBs. Quantitative analysis of labeling density showed that all proteins examined were concentrated in the CBs to some extent. These results show that the CBs have some aggresomal features, suggesting that they are not a synthetic site as proposed previously but a degradation site where unnecessary DNA, RNA, and proteins are digested. 相似文献
1000.
Tomo Inomata Hiroyoshi Ninomiya Tomoyuki Mizutani Yuko Mori Naomi Kashiwazaki Akio Kiuchi Tetsushi Nagai 《Experimental Animals》2005,54(2):117-122
A simple method of ileocolostomy was performed in rats. The colon near the cecum was ligated, including its arteries and veins. Main artery and vein of the cecum were ligated. Then, the cecum was cut out. A longitudinal incision was made on the anti-mesenteric side of the proximal end of the colon, approximately 7-8 mm long. A 21-G needle was inserted toward the incision 2 cm away from the proximal end of the anti-mesenteric side of the colon. A nylon suture was knotted once to the distal end of the ileum and was introduced into the tip of the needle which had previously been passed through the colon. Then, the needle was removed. The suture was pulled to introduce the distal end of the ileum into the colonic lumen. Then, the suture was knotted once on the colon again to fix the ileum to the colon. The incision in the proximal end of the colon was not closed. At the 2nd week after the operation, X-ray examinations demonstrated that the ileocolonic passages with no leakage at the anastomotic site were quite satisfactory. At the 4th week after the operation, there were no macroscopic or microscopic complications at the anastomotic site. The mucosal and serosal epithelia of the ileum and colon continued smoothly. This simple method may be very effective in preparing anastomosis in the gastrointestinal tract, especially in small laboratory animals for nutritional and surgical experiments. 相似文献