全文获取类型
收费全文 | 9867篇 |
免费 | 676篇 |
国内免费 | 9篇 |
专业分类
10552篇 |
出版年
2022年 | 45篇 |
2021年 | 96篇 |
2020年 | 54篇 |
2019年 | 68篇 |
2018年 | 130篇 |
2017年 | 95篇 |
2016年 | 144篇 |
2015年 | 206篇 |
2014年 | 281篇 |
2013年 | 503篇 |
2012年 | 438篇 |
2011年 | 480篇 |
2010年 | 265篇 |
2009年 | 280篇 |
2008年 | 483篇 |
2007年 | 436篇 |
2006年 | 426篇 |
2005年 | 418篇 |
2004年 | 432篇 |
2003年 | 400篇 |
2002年 | 415篇 |
2001年 | 367篇 |
2000年 | 373篇 |
1999年 | 306篇 |
1998年 | 144篇 |
1997年 | 107篇 |
1996年 | 114篇 |
1995年 | 113篇 |
1994年 | 86篇 |
1993年 | 70篇 |
1992年 | 229篇 |
1991年 | 239篇 |
1990年 | 200篇 |
1989年 | 208篇 |
1988年 | 160篇 |
1987年 | 141篇 |
1986年 | 122篇 |
1985年 | 132篇 |
1984年 | 112篇 |
1983年 | 115篇 |
1982年 | 94篇 |
1981年 | 72篇 |
1980年 | 54篇 |
1979年 | 79篇 |
1978年 | 86篇 |
1977年 | 59篇 |
1976年 | 73篇 |
1975年 | 54篇 |
1973年 | 59篇 |
1971年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Senotypes of Mycobacterium intracellulare of porcine origin 总被引:2,自引:0,他引:2
102.
Glyceraldehyde-3-phosphate dehydrogenase [ED 1.2.1.12] was purified from the horseshoe crab, a living fossil, and its properties were examined. 1 The purified enzyme was homogeneous as judged by various tests. The enzyme, like enzymes from other sources, was a tetramer with a subunit molecular weight of 36,000. The kinetic parameters and pH optimum were also similar to those of other enzymes, though the enzyme was more stable against heat and pH denaturations. 2 Analysis of SH groups showed that there were 4 SH groups per subunit, one of which was essential for the enzyme activity and was highly reactive. 3. CD spectra of the enzyme suggested that the enzyme had a very high content of beta-structure (ca. 45 per cent). 4. The horseshoe crab enzyme could form a hybrid in vitro with the rabbit muscle enzymes in concentrated salt solution at acidic pH. 5. There results indicate that the enzyme has overall structural similarity to other enzymes and that the enzyme is highly conserved during a long period of evolution. Some discussions on the structure and activity of the horseshoe crab enzyme are made in comparison with the enzymes from other sources. 相似文献
103.
Kezuka Y Kitazaki K Itoh Y Watanabe J Takaha O Watanabe T Nishizawa Y Nonaka T 《Protein and peptide letters》2004,11(4):401-405
We report here on crystallization and preliminary X-ray analysis of plant class I chitinase from rice (OsChia1b). Similar single crystals of full-length OsChia1b were obtained under two independent conditions. The crystals grown under these conditions diffracted up to 2.1 and 2.5 angstroms resolution, respectively, at a synchrotron beamline, and were found to belong to the tetragonal space group P4(3)2(1)2. 相似文献
104.
Shigeo Daikoku Tamio Takahashi Haruo Kojimoto Yuichi G. Watanabe 《Cell and tissue research》1973,136(2):207-214
Summary The freeze-etching technique was used in studies of cell surface phenomena during the release of secretory products from the adenohypophysis and from neurosecretory terminals of rats in which exocytosis had been stimulated by the administration of hypothalamic extracts (somatotrophs, thyrotrophs, gonadotrophs and mammotrophs) or severe hemorrhage (neurohypophysis). The observations suggest that secretory granules are extruded through an opening at the tip of a protrusion of the cellular surface. The protrusions seem to result from the abutting of secretory granules on the inner surface of the plasma membrane. These structural details revealed in freeze-etched preparations have not been seen previously in conventional micrographs of ultrathin sections and may provide a clue to the mechanism of secretion.Supported by grants from the Japanese Educational Ministry. — The technical assistance of Mr. Takeshi Fukunishi is acknowledged with gratitude. 相似文献
105.
Sasado T Morinaga C Niwa K Shinomiya A Yasuoka A Suwa H Hirose Y Yoda H Henrich T Deguchi T Iwanami N Watanabe T Kunimatsu S Osakada M Okamoto Y Kota Y Yamanaka T Tanaka M Kondoh H Furutani-Seiki M 《Mechanisms of development》2004,121(7-8):817-828
The development of germ cells has been intensively studied in Medaka (Oryzias latipes). We have undertaken a large-scale screen to identify mutations affecting the development of primordial germ cells (PGCs) in Medaka. Embryos derived from mutagenized founder fish were screened for an abnormal distribution or number of PGCs at embryonic stage 27 by RNA in situ hybridization for the Medaka vasa homologue (olvas). At this stage, PGCs coalesce into two bilateral vasa-expressing foci in the ventrolateral regions of the trunk after their migration and group organization. Nineteen mutations were identified from a screen corresponding to 450 mutagenized haploid genomes. Eleven of the mutations caused altered PGC distribution. Most of these alterations were associated with morphological abnormalities and could be grouped into four phenotypic classes: Class 1, PGCs dispersed into bilateral lines; Class 2, PGCs dispersed in a region more medial than that in Class 1; Class 3, PGCs scattered laterally and over the yolk sac area; and Class 4, PGCs clustered in a single median focus. Eight mutations caused a decrease in the number of PGCs. This decrease was observed in the offspring of heterozygous mothers, indicating the contribution of a maternal factor in determining PGC abundance. Taken together, these mutations should prove useful in identifying molecular mechanisms underlying the early PGC development and migration. 相似文献
106.
107.
Yoshikazu Arai Jun Ohgane Shuh‐hei Fujishiro Kazuaki Nakano Hitomi Matsunari Masahito Watanabe Kazuhiro Umeyama Dai Azuma Naomi Uchida Nozomu Sakamoto Tomohiro Makino Shintaro Yagi Kunio Shiota Yutaka Hanazono Hiroshi Nagashima 《Genesis (New York, N.Y. : 2000)》2013,51(11):763-776
Porcine induced pluripotent stem cells (iPSCs) provide useful information for translational research. The quality of iPSCs can be assessed by their ability to differentiate into various cell types after chimera formation. However, analysis of chimera formation in pigs is a labor‐intensive and costly process, necessitating a simple evaluation method for porcine iPSCs. Our previous study identified mouse embryonic stem cell (ESC)‐specific hypomethylated loci (EShypo‐T‐DMRs), and, in this study, 36 genes selected from these were used to evaluate porcine iPSC lines. Based on the methylation profiles of the 36 genes, the iPSC line, Porco Rosso‐4, was found closest to mouse pluripotent stem cells among 5 porcine iPSCs. Moreover, Porco Rosso‐4 more efficiently contributed to the inner cell mass (ICM) of blastocysts than the iPSC line showing the lowest reprogramming of the 36 genes (Porco Rosso‐622‐14), indicating that the DNA methylation profile correlates with efficiency of ICM contribution. Furthermore, factors known to enhance iPSC quality (serum‐free medium with PD0325901 and CHIR99021) improved the methylation status at the 36 genes. Thus, the DNA methylation profile of these 36 genes is a viable index for evaluation of porcine iPSCs. genesis 51:763–776. © 2013 Wiley Periodicals, Inc. 相似文献
108.
109.
Watanabe S Kobayashi T Saito M Sato M Nimura-Matsune K Chibazakura T Taketani S Nakamoto H Yoshikawa H 《Biochemical and biophysical research communications》2007,352(1):36-41
In cyanobacterium Synechococcus elongatus PCC 7942, we observed that htpG-overexpression caused remarkable growth inhibition. In addition, subcellular fractionation experiments showed that HtpG was localized in the membrane fraction. To understand its function in cyanobacteria, we carried out yeast two-hybrid screening to identify specific proteins interacting with HtpG, and found out, HemE, uroporphyrinogen decarboxylase. When compared to the wild-type strain, the htpG-null mutant and -overexpressing strains exhibited higher and lower cytosolic HemE activity, based on the coproporphyrin production, respectively. These results strongly suggest that HtpG is involved in the regulation of tetrapyrrole biosynthesis through interacting with HemE protein. 相似文献
110.
Toshio Okazaki Masakazu Watanabe Kenya Mizuguchi Kazumi Hosoya 《Ichthyological Research》1991,38(2):133-140
Two types of the dark chub,Zacco temmincki, collected from 10 river systems in Japan were genetically characterized at 27 protein coding loci using starch-gel electrophoresis. They were fixed for different alleles at 13 loci. No hybrid individuals were observed, even in specimens collected in stations where both types appear sympatrically, indicating that each type of the dark chub represents a distinct species. 相似文献