全文获取类型
收费全文 | 2398篇 |
免费 | 108篇 |
国内免费 | 3篇 |
出版年
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 26篇 |
2015年 | 38篇 |
2014年 | 71篇 |
2013年 | 389篇 |
2012年 | 93篇 |
2011年 | 121篇 |
2010年 | 90篇 |
2009年 | 62篇 |
2008年 | 136篇 |
2007年 | 137篇 |
2006年 | 124篇 |
2005年 | 154篇 |
2004年 | 159篇 |
2003年 | 140篇 |
2002年 | 147篇 |
2001年 | 22篇 |
2000年 | 11篇 |
1999年 | 28篇 |
1998年 | 28篇 |
1997年 | 25篇 |
1996年 | 32篇 |
1995年 | 24篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 22篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 18篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 30篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1978年 | 16篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 6篇 |
排序方式: 共有2509条查询结果,搜索用时 93 毫秒
991.
Danilo B. Largo Kimio Fukami Toshitaka Nishijima Masao Ohno 《Journal of applied phycology》1995,7(6):539-543
The most common perception of unfavorable environmental factors causing the ice-ice disease in the farmed seaweeds, Kappaphycus and Eucheuma, was demonstrated in this study for the first time using stressful conditions of abiotic factors in a continuous culture system. Light intensity of less than 50 mol photon m–2 s–1 and salinity of 20% or less induced ice-ice whitening characterized by short segments at midbranches which were similar to those observed in the Philippine seaweed farms, while temperatures of up to 33–35 °C resulted in wide-scale whitening leading to complete damage of the branches. These effects were preceded by slow growth rates from an optimum of 3.7% d–1 to almost –2.0% d–1. Mechanical stress by wound injury did not result to ice-ice whitening similar to the above. Environmental factors observed to trigger ice-ice in the laboratory, although may not necessarily parallel those in the field, may act synergestically to produce similar effects. 相似文献
992.
In the region between the polyadenylation site of the rat skeletal muscle (SkM) Na-channel gene and the 5′ end of the growth hormone (GH) gene, a gene coding for B-cell-specific membrane protein B29/Ig-β was found and noted to have the same orientation as the Na-channel and GH genes. Rat B29/Ig-β gene was 3.1 kb in length with six exons and was separated by 3.3 and 9.3 kb from Na-channel and GH genes, respectively. Rat B29/Ig-β protein comprised 228 amino acids, and its amino acid sequence was 85 and 69% identical with the mouse and human counterparts, respectively. With the long-area PCR method, genomic DNA connecting human SkM Na-channel (SCN4A) and B29/Ig-β (CD79B) genes and CD79B and GH (GH1) genes was amplified, and the physical linkage of SCN4A/CD79B/GH1 genes in the human genome was established. The human CD79B gene was separated by 6.3 and 10.5 kb from the SCN4A and GH1 genes, respectively. 相似文献
993.
Masao S. Sasaki 《Mutation research》1996,358(2):159-213
Radioadaptive response provides a considerable impact on the risk assessment of low-dose and low dose-rate exposures to ionizing radiations. The cells previously exposed to low doses of radiations become resistant to the induction of mutations, chromosome aberrations and cell killing by the subsequent doses but more susceptible to malignant transformation. The reaction kinetics of radioadaptive response were incorporated into a modelling of biological consequences of protracted low dose-rate exposures to radiations. The model is also consistent with the low dose-rate effects on spermatogonial mutations and translocations in the experimental animals and inverse dose-rate effects of morphological transformation in cultured cells. 相似文献
994.
Calmodulin and Ca2+ - and Calmodulin-Dependent Protein Kinase in Rat Anterior Pituitary Gland 总被引:1,自引:0,他引:1
Yasuyuki Hatada Masahide Munemura Kohji Fukunaga Hideyuki Yamamoto Masao Maeyama Eishichi Miyamoto 《Journal of neurochemistry》1983,40(4):1082-1089
Calmodulin and Ca2+- and calmodulin-dependent protein kinase were identified in the rat anterior pituitary gland. The concentration of calmodulin was 1.18 +/- 0.11 microgram/mg protein (n = 7) in the cytosol fraction. The calmodulin of the anterior pituitary gland co-migrated with brain calmodulin on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Ka value of the partially purified enzyme for Ca2+ was 3.3 microM in the presence of 0.30 microM calmodulin. Trifluoperazine and chlorpromazine, calmodulin-interacting agents, inhibited enzyme activity, with Ki values of 1.3 and 2.6 X 10(-5) M, respectively. The enzyme was resolved into two peaks of activity, with sedimentation coefficients of 5.5 S and 16.5 S, by sucrose density gradient centrifugation. At least nine proteins were phosphorylated by the enzyme in a Ca2+- and calmodulin-dependent manner. In light of these results, the possibility that calmodulin and the calmodulin-activatable protein kinase system are involved in the mediation of the Ca2+ effect on hormone release from the anterior pituitary gland must be given consideration. 相似文献
995.
996.
997.
Jun Yoshinaga Jia-Zhen Li Tsuguyoshi Suzuki Kanae Karita Masao Abe Hitoshi Fujii Jun Mishina Masatoshi Morita 《Biological trace element research》1991,31(2):159-170
Multielement analysis was performed on human milk collected on 5-9-d postpartum from 51 Japanese females using inductively coupled plasma (ICP) mass spectrometry (MS), ICP atomic emission spectrometry (ICP-AES) and fluorometry. Thirty-one elements were detected by these analytical methods in milk. Twelve elements (Na, Mg, P, S, K, Ca, Cu, Zn, Se, Sr, Rb, and Mo) were detected in all of the samples. Al, Cs, and Ba were the elements detected by ICP-MS in more than half of the samples. Multiple regression analysis extracted biological attributes of mother and infant, such as maternal stature, maternal wt, or infant's birth wt, as statistically significant factors contributing to the variation in elemental concentration in milk. However, the rates of contribution were small in all cases. It was concluded that the biological attributes of mother and infant examined in this study were not the major factors that contribute to elemental variation in human milk. 相似文献
998.
Roles of Sucrose-Metabolizing Enzymes in Growth of Seedlings. Purification of Acid Invertase from Growing Hypocotyls of Mung Bean Seedlings 总被引:1,自引:0,他引:1
Changes in activities of acid invertase and sucrose synthaseduring growth of mung bean seedlings were examined and the correlationbetween the activity of acid invertase and growth was confirmed.Acid invertase was purified from hypocotyls of etiolated seedlingsand separated into two fractions (A and B) by chromatographyon hydroxylapatite. Acid invertase in fraction B consisted oftwo polypeptides of 30 kDa and 38 kDa, but that in fractionA was 70 kDa in size. Antibodies raised against the 30-kDa polypeptideimmunoprecipitated enzymatic activity but those raised againstthe 38-kDa polypeptide did not. The concanavalin A-binding siteof acid invertase was contained in the 38-kDa polypeptide andnot in the 30-kDa polypeptide. However, when acid invertasewas bound to and eluted from concanavalin A-Sepharose, the 30-kDapolypeptide was found together with the 38-kDa polypeptide inthe eluate. Acid invertase in hypocotyls of mung bean seedlingsappears to be present in two forms: a monomer of 70 kDa anda hetero-dimer of 30-kDa and 38-kDa polypeptides. The monomerwas not converted to the heterodimer during incubation of acrude extract and was present together with the heterodimerin very young hypocotyls. In older hypocotyls, the heterodimerwas present but the monomer was barely detectable. We concludethat the two forms of acid invertase are present within cells,but the relationship between the two forms is unknown at present. (Received July 18, 1991; Accepted October 9, 1991) 相似文献
999.
Mitsukazu Saito Takashi Shinbo Tomohiro Saito Hiroshi Kato Haruyo Otagiri Yoshiaki Karaki Kenji Tazawa Masao Fujimaki 《In vitro cellular & developmental biology. Plant》1990,26(2):181-186
Summary As basic studies of hyperthermia and hypothermia on malignant tumor, the kinetics of proliferative activity, the morphologic
changes in the two cell lines, SGF-3 and SGF-5, established in our department after the change of culture temperature were
examined. The results obtained were: a) A significant difference was found in the sensitivity to temperatures between the
two cell lines originated from human esophageal squamous cell carcinoma. The temperature range allowing cultured cell to proliferate
were from 31° to 39° C in SGF-3 and from 29° to 41° C in SGF-5. b) Minor difference occurred in the results between the two
cell lines examined during the recovery of proliferative activity, but no proliferative activity was discovered after the
cells were exposed to 42° C for 72 h. Two cell lines resumed their proliferation after having been exposed to 27° or 28° C
for 72 h. c) Morphologic changes of the cell lines cultured at high temperature were cytoplasmic vacuolation and cell aggregation
by phase contrast microscope and the increase of heterochromatin, the decrease of granular formation in nucleoli, and nucleolar
vacuolation by transmission electron microscopy (TEM). At low temperatures the changes observed included cytoplasmic ballooning
and circumnuclear halo formation by phase contrast microscope, and the increase of heterochromatin, nucleolar segregation,
swelling of mitochondria, and dilatation of rough endoplasmic reticulum (rER) by TEM. 相似文献
1000.
Kaoru Miyamoto Yoshihisa Hasegawa Takashi Minegishi Mitsuo Nomura Yoshitaka Takahashi Masao Igarashi Kenji Kangawa Hisayuki Matsuo 《Biochemical and biophysical research communications》1982,107(3):820-827
A peptide having gonadotropin-releasing activity was isolated in a yield of 2.5 μg from an extract of 2,000 chicken hypothalami. The biopotency was monitored using rat anterior pituitary cell culture system. The peptide differs from mammalian Luteinizing Hormone-Releasing Hormone (LH-RH) in its behavior during chromatographic separation (ionexchange and high performance liquid chromatography) and in its reaction towards anti-LH-RH antiserum directed against the C-terminal region of the LH-RH molecule. The peptide (chicken LH-RH) stimulates secretion of both LH and FSH from rat anterior pituitary cells. The biological potency of this peptide was about 4 % of that of the authentic decapeptide estimated in the rat anterior pituitary system. The amino acid composition is (Ser, Pro, Glx2, Gly2, Leu, Tyr, His, Trp), which differs from mammalian LH-RH only in that one Arg residue is replaced by a Glx residue. Based on the behavior on CM cellulose chromatography and the reaction towards anti-LH-RH antiserum, one possible structural candidate for this peptide (chicken LH-RH) is [Gln8]-LH-RH. 相似文献