全文获取类型
收费全文 | 2960篇 |
免费 | 320篇 |
专业分类
3280篇 |
出版年
2023年 | 11篇 |
2022年 | 34篇 |
2021年 | 52篇 |
2020年 | 47篇 |
2019年 | 57篇 |
2018年 | 69篇 |
2017年 | 56篇 |
2016年 | 101篇 |
2015年 | 129篇 |
2014年 | 139篇 |
2013年 | 164篇 |
2012年 | 192篇 |
2011年 | 198篇 |
2010年 | 119篇 |
2009年 | 123篇 |
2008年 | 128篇 |
2007年 | 133篇 |
2006年 | 138篇 |
2005年 | 104篇 |
2004年 | 103篇 |
2003年 | 107篇 |
2002年 | 89篇 |
2001年 | 89篇 |
2000年 | 84篇 |
1999年 | 85篇 |
1998年 | 32篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 23篇 |
1992年 | 50篇 |
1991年 | 58篇 |
1990年 | 54篇 |
1989年 | 56篇 |
1988年 | 39篇 |
1987年 | 32篇 |
1986年 | 35篇 |
1985年 | 29篇 |
1984年 | 24篇 |
1983年 | 29篇 |
1982年 | 23篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1978年 | 17篇 |
1977年 | 16篇 |
1976年 | 9篇 |
1974年 | 12篇 |
1971年 | 11篇 |
排序方式: 共有3280条查询结果,搜索用时 15 毫秒
11.
T T Herskovits P A Blake J A Gonzalez M G Hamilton J S Wall 《Comparative biochemistry and physiology. B, Comparative biochemistry》1989,94(2):415-421
1. The hemocyanins of the Melongenidae family of marine gastropods: Melongena corona, Busycon canaliculatum, B. carica, B. contrarium, and B. spiratum exist in solution as multi-decameric aggregates characterized by sedimentation coefficients of approximately 105 S, 130 S, 150 S, 170 S, and higher values, corresponding to di-, tri-, tetra-, penta-, and larger multi-decameric particles. 2. The hemocyanins of B. contrarium and B. carica seem to form the largest decameric aggregates with the tri- to penta-decamers respresenting the major constitutents. Scanning transmission electron microscopy (STEM), both of unstained, freeze-dried and negatively-stained specimens, shows the presence of discrete aggregates consisting of up to ten decameric units. 3. The particle masses as determined by STEM mass measurements for individual molecules gave integral multiples of from 4.2 x 10(6) to 4.4 x 10(6) daltons ranging from about 8.2 x 10(6) daltons for the typical di-decamer of B. canaliculatum hemocyanin to as high as about 39 x 10(6) and 43 x 10(6) for the nano-and deca-decamers of B. contrarium hemocyanin. 4. The appearance of the higher multi-decamers in both negatively-stained and freeze-dried specimens suggest that they are formed by the addition of decameric units to a single di-decameric unit "tail-wise" in both directions. The higher aggregates formed seem to terminate with a closed head or collar at both ends of the assembly. 相似文献
12.
D Gazis G Gonzalez M Mendlowitz 《Canadian journal of physiology and pharmacology》1989,67(12):1586-1590
Simultaneous blood pressure and uterine responses to norepinephrine infusions were recorded in urethane-anesthetized, pentolinium-indomethacin treated rats in natural estrus under conditions in which no blockers or blockers of alpha 1-, alpha 2-, and beta-adrenergic receptors or of "reuptake" of norepinephrine were present. The contributions of alpha 1- and alpha 2-adrenergic receptors to the blood pressure response were similar during the initial portion of the response. At later times, however, alpha 1-adrenergic receptors were responsible for the major portion of the response. The tachyphylaxis of the pressor response that occurs during norepinephrine infusion could be prevented by preventing norepinephrine "reuptake" with imipramine. In the uterus, the initial small alpha-adrenergic contractile response (seen only at the lowest infusion rate) was quickly overwhelmed by a beta-adrenergic relaxing component. Administration of the beta-adrenergic receptor blocker, propranolol, during norepinephrine infusion caused similar increases in blood pressure in control, yohimbine-, and prazosin-treated rats. Uterine contractions, in contrast, were only significantly elevated during beta-adrenergic receptor blockade when yohimbine or imipramine had also been administered. 相似文献
13.
Identification by flow cytometry of two distinct rhodamine-123-stained mitochondrial populations in rat liver 总被引:2,自引:0,他引:2
Isolated rat liver mitochondria were split into three fractions of increasing density when applied to a Percoll gradient. NADH-ubiquinone oxidoreductase, succinate dehydrogenase and cytochrome-c oxidase but not F1-ATPase activities increased with density as well as respiratory rate in state 3 and the respiratory control index. Flow cytometry of mitochondrial density fractions stained with rhodamine-123 revealed the occurrence in each density fraction of two distinct mitochondrial populations with different fluorescence intensity. The high fluorescence population was minor and its proportion decreased with density. The extent of high fluorescence population staining depended on the deenergized state of the mitochondria suggesting that this population represents an immature form of the mitochondria which may develop into a fully functional organelle by the incorporation of structural and/or functional proteins. 相似文献
14.
The CYP2D gene subfamily: analysis of the molecular basis of the debrisoquine 4-hydroxylase deficiency in DA rats 总被引:1,自引:0,他引:1
E Matsunaga U M Zanger J P Hardwick H V Gelboin U A Meyer F J Gonzalez 《Biochemistry》1989,28(18):7349-7355
The DA rat has been proposed as an animal model for the human debrisoquine 4-hydroxylase/bufuralol 1'-hydroxylase genetic deficiency. To determine the mechanism of this deficiency, we isolated and sequenced five cDNAs in the CYP2D gene subfamily including a new IID1 allele and two cDNAs of novel P450s, designated IID3 and IID5. IID3 and IID5 cDNA-deduced amino acid sequences contained 500 and 504 residues with calculated molecular weights of 56,683 and 57,081, respectively. IID5 displayed 20 amino acid differences with the IID1, yet bore only 72% and 76% similarity to IID2 and IID3. Despite an overall nucleotide similarity of 80-98% between the 4 cDNAs, a region of 134 nucleotides of sequence exists that contains only 1 base difference. This region is probably the result of gene conversion events between the P450 IID genes. Although all IID cDNAs were expressed into immunodetectable proteins using the COS cell SV40-based expression system, only IID1 could effectively catalyze the oxidation of the prototype substrate bufuralol. Expression of a cDNA isolated in an earlier study [Gonzalez, F. J., Matsunaga, T., Nagata, K., Meyer, U. A., Nebert, D. W., Pastewka, J., Kozak, C. A., Gillette, J., Gelboin, H. V., & Hardwick, J. P. (1987) DNA 6, 149-161], previously called db1 and now designated IID1v, produced a protein with a drastically reduced activity as compared to cDNA-expressed IID1 despite only four amino acid differences between the two cDNA-deduced protein sequences.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
15.
16.
17.
Roderick A. Capaldi Diego Gonzalez Halphen Yu-Zhong Zhang Wayne Yanamura 《Journal of bioenergetics and biomembranes》1988,20(3):291-311
There is a renewed interest in the structure and functioning of the mitochondrial respiratory chain with the realization that a number of genetic disorders result from defects in mitochondrial electron transfer. These so-called mitochondrial myopathies include diseases of muscle, heart, and brain. The respiratory chain can be fractionated into four large multipeptide complexes, an NADH ubiquinone reductase (complex I), succinate ubiquinone reductase (complex II), ubiquinol oxidoreductase (complex III), and cytochromec oxidase (complex IV). Mitochondrial myopathies involving each of these complexes have been described. This review summarizes compositional and structural data on the respiratory chain proteins and describes the arrangement of these complexes in the mitochondrial inner membrane. This biochemical information is provided as a framework for the diagnosis and molecular characterization of mitochondrial diseases. 相似文献
18.
The contribution of this paper is a bivariate optimization of cycling performance. Relying on a biomechanical model of the lower limb, a cost function derived from the joint moments developed during cycling is computed. At constant average power, both pedalling rate (i.e. rpm) and crank arm length are systematically varied to explore the relation between these variables and the cost function. A crank arm length of 170 mm and pedalling rate of 100 rpm correspond closely to the cost function minimum. In cycling situations where the rpm deviates from 100 rpm, however, crank arms of length other than 170 mm yield minimum cost function values. In addition, the sensitivity of optimization results to both increased power and anthropometric parameter variations is examined. At increased power, the cost function minimum is more strongly related to the pedalling rate, with higher pedalling rates corresponding to the minimum. Anthropometric parameter variations influence the results significantly. In general it is found that the cost function minimum for tall people occurs at longer crank arm lengths and lower pedalling rates than the length and rate for short people. 相似文献
19.
Human debrisoquine 4-hydroxylase (P450IID1): cDNA and deduced amino acid sequence and assignment of the CYP2D locus to chromosome 22 总被引:9,自引:0,他引:9
F J Gonzalez F Vilbois J P Hardwick O W McBride D W Nebert H V Gelboin U A Meyer 《Genomics》1988,2(2):174-179
The enzyme P450db1 (db1) is responsible for the common human defect in drug oxidation known as the "debrisoquine/sparteine polymorphism." Polyclonal antibody against the rat db1 protein was used to screen a human liver lambda gt11 library for the db1 cDNA clone. A cDNA containing the full protein coding sequence was isolated; the deduced NH2-terminal sequence of this cDNA was identical to that derived from direct sequencing of the purified human db1 protein. Comparison of the human db1 with rat db1 revealed 71 and 73% similarities of nucleotides and amino acids, respectively. By use of human-rodent somatic cell hybrids the db1 gene was localized to human chromosome 22 (CYP2D locus). 相似文献
20.