全文获取类型
收费全文 | 13753篇 |
免费 | 699篇 |
国内免费 | 8篇 |
专业分类
14460篇 |
出版年
2023年 | 27篇 |
2022年 | 65篇 |
2021年 | 113篇 |
2020年 | 58篇 |
2019年 | 85篇 |
2018年 | 139篇 |
2017年 | 145篇 |
2016年 | 245篇 |
2015年 | 376篇 |
2014年 | 433篇 |
2013年 | 1140篇 |
2012年 | 764篇 |
2011年 | 826篇 |
2010年 | 481篇 |
2009年 | 462篇 |
2008年 | 783篇 |
2007年 | 865篇 |
2006年 | 855篇 |
2005年 | 890篇 |
2004年 | 972篇 |
2003年 | 912篇 |
2002年 | 859篇 |
2001年 | 139篇 |
2000年 | 102篇 |
1999年 | 146篇 |
1998年 | 221篇 |
1997年 | 206篇 |
1996年 | 169篇 |
1995年 | 146篇 |
1994年 | 114篇 |
1993年 | 154篇 |
1992年 | 126篇 |
1991年 | 91篇 |
1990年 | 91篇 |
1989年 | 88篇 |
1988年 | 85篇 |
1987年 | 64篇 |
1986年 | 73篇 |
1985年 | 86篇 |
1984年 | 100篇 |
1983年 | 87篇 |
1982年 | 106篇 |
1981年 | 95篇 |
1980年 | 83篇 |
1979年 | 41篇 |
1978年 | 47篇 |
1977年 | 43篇 |
1976年 | 51篇 |
1974年 | 36篇 |
1973年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
The Level of Stromal ATP Regulates Translation of the D1 Protein in Isolated Chloroplasts 总被引:1,自引:0,他引:1
The synthesis of the D1 subunit of the reaction center of photosystemII is light-dependent in isolated chloroplasts. The mechanismof the regulation by light was analyzed using spinach chloroplasts.The light-regulated synthesis of the D1 protein was preventedby the addition of atrazine and the dependence on the concentrationof atrazine of the inhibition was practically identical withthat of the inhibition of photosynthetic electron transportin photosystem II, as measured by the photoreduction of 2,6-dichlorophenolindophenol. Inhibitors of photosynthetic phosphorylation, suchas phloridzin, nigericin and carbonyl cyanide m-chlorophenylhydrazone,also inhibited the light-dependent synthesis of the D1 protein.Determination of the levels of ATP in chloroplasts and the ratesof synthesis of D1 protein under the various degrees of inhibitioncaused by these reagents suggested that the level of ATP inthe soluble, stromal fraction can control the synthesis of theD1 protein. The level of stromal ATP in chloroplasts was furthermanipulated, either by modulating the intensity of actinic lightor by the addition of metabolites, such as glycerate, whichwas used to decrease the level of ATP in the light, and dihydroxyacetonephosphate/oxaloacetate, which was used to raise the level ofATP in the dark. The results definitely support the hypothesisthat the light-induced level of ATP is an essential determinantin the regulation of the synthesis of the D1 protein in isolatedchloroplasts. (Received July 25, 1991; Accepted October 22, 1991) 相似文献
112.
Hiroshi Ihobe 《Primates; journal of primatology》1992,33(2):247-250
Meat-eating behavior of wild bonobos (Pan paniscus) was witnessed on two occasions at Wamba, Republic of Zaire. Only flying squirrels were observed to be eaten by the bonobos.
Several bonobos gathered around the possessor of the meat and showed interest in the meat on all occasions. Begging behavior
was noted on one of the two occasions, but the possessor of the meat ignored it. No sharing of meat was seen on either occasion.
The exclusive targets of hunting by bonobos are apparently small mammals, such as flying squirrels and infant duikers, since
evidence of meat eating by wild bonobos, which have been studied for more than fifteen years, has been restricted to these
mammals. The bonobos at Wamba may have a specialized “prey image”, as in the case of the chimpanzees (Pan troglodytes) of the Tai forest, and certain medium-sized or small mammals may not conform to this image. 相似文献
113.
114.
Yasuko Kawamura-Konishi Kaori Chiba Hiroshi Kihara Haruo Suzuki 《European biophysics journal : EBJ》1992,21(2):85-92
Kinetics of the reconstitution of hemoglobin from semihemoglobins and with hemin dicyanide have been investigated using three kinds of stopped-flow technique (Soret absorption, fluorescence quenching of tryptophan, and Soret CD). The semihemoglobins and are occupied by heme in the and chains, respectively, the other chain being heme-free. Based on the kinetic results, the following scheme for the reconstitution is proposed; First, hemin dicyanide enters the pocket-like site of the apo chains. Second, in semihemoglobin , the CN-ligand in the fifth coordination position of iron is replaced by the imidazole ring of the proximal His immediately after the heme insertion. In contrast, semihemoglobin changes its conformation after the heme insertion, and this is followed by the ligand replacement. Finally, the partial structure changes induced by the ligand replacement propagate onto the whole molecule and the final conformation is attained. The results indicate that semihemoglobin retains a more rigid and organized structure, and more closely approaches its final structure than does semihemoglobin .
Correspondence to: Y. Kawamura-Konishi 相似文献
115.
Nobuyuki Inagaki Hiroaki Nishimura Minoru Okada Hiroshi Mitsuhashi 《Plant cell reports》1991,9(9):484-487
Verbascoside was found to be produced in all calli derived from eleven species that contained the compound in their leaves. Cell suspension cultures were also established in three species, i.e., Leucosceptrum japonicum f. barbinerve, Syringa josikaea, and Sy. vulgaris, all of which were found to produce verbascoside at more than 1 g/l. Of the three species, suspension cultures of L. japonicum f. barbinerve showed rapid growth and the highest yield of verbascoside (1.89 g/l). In these cultures, the effects of major salt concentration in B5 medium on cell growth and verbascoside production were examined. Maximum cell growth and maximum verbascoside production were both achieved by reducing the major salt concentration to half that of the original medium. 相似文献
116.
117.
Masamitsu Honma Eiko Kataoka Kiyokata Ohnishi Tadao Ohno Masao Takeuchi Nobuo Nomura Hiroshi Mizusawa 《In vitro cellular & developmental biology. Animal》1992,28(1):24-28
Summary Using the polymorphic DNA probes, ChdTC-15, ChdTC-114, pYNH24, and λTM-18, a DNA profiling system was developed that verified
identities of individual cultured cell lines collected in the Japanese cell banks, JCRB, RCB, and IFO. These highly polymorphic
DNA probes include both VNTR (Variable Number of Tandem Repeats) sequences and substantial lengths of unique regions. In the
mixed probe system, several distinct bands from four to eight can be used for cell line identification. These bands were widely
spread in a range of molecular sizes, and were stable and reproducible under stringent conditions of Southern blot hybridization.
Because the DNA profile was specific for each individual human cell line, it is useful not only to authenticate many existing
cultured cell lines but also to monitor their identity during propagation in a laboratory, and to confirm newly established
lines as unique. 相似文献
118.
119.
Hiroshi Terayama Takehiko Koji Mariko Kontani Takeki Okumoto 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1982,720(2):188-192
Plasma membranes prepared from rat livers inhibited the in vitro growth of various mammalian cells including hepatoma cells in a concentration-dependent manner, showing an almost complete arrest of cell growth at 0.1 mg protein/ml. Some of these cells tested, i.e., leukemia (L1210 and P388) and myeloma (P3-NS-1/1-Ag4-1) cells, were labile in the presence of plasma membranes (losing the viability), and CHO (Chinese hamster ovary) cells became round without detaching from the substratum. The culture medium preincubated with liver plasma membranes no longer supported the growth of hepatoma cells (AH13 and AH66F). However, the ‘conditioned’ medium supplemented with l-arginine, supported the growth of the cells. Moreover, the addition of l-ornithine to the cultures containing plasma membranes markedly reduced the inhibitory effect of plasma membranes. The plasma membrane preparations were found to possess considerable arginase activity. These results seem to indicate the possible involvement of arginase in the inhibition of cell growth by liver plasma membranes. 相似文献
120.
Yoshiteru Harada Kunio Tanaka Yasushiro Uchida Akinori Ueno Sachiko Oh-ishi Yamashita Kowa Masataka Ishibashi Hiroshi Miyazaki Makoto Katori 《Prostaglandins & other lipid mediators》1982,23(6)
Injection of γ-carrageenin into t he pleural cavity of rats caused the accumulation of the pleural exudate. When levels of prostaglandins (PGs) and thromboxane (TX) B2 were quantified by gas chromatography-mass spectrometry as their methyl ester (ME)-dimethyllisopropylsilyl (DMiPS) ether or ME-methoxine-DMiPS ether derivatives, 6-keto-PGF1α reached the maximum at 1 hr after carrageenin, then PGE2 and TXB2 showed peaks at 3 hr and waned off before 9 hr. he PGF2α level was kept low, but PGD2, PGE1 and PGF1α were not detected. Aspirin (100 mg/kg, i.p.) significantly decreased the PG and TXB2 levels and suppressed the rate of plasma exudation until 5 hr, but did not at 7 hr, when it was measured by the amount of exuded pontamine sky blue injected intravenously. OKY-025 (300 mg/kg, i.p.), a selective TXA synthetase inhibitor, and tranylcypromine (20 mg/kg, i.p.), a PGI synthetase inhibitor, could not extensively inhibit the accumulation of the exudate. These results suggest that the cyclooxygenase products of arachidonic acid, particularly PGE2, definitely play an important role in the exudation during the first 5 hr. 相似文献